Book - Buchanan's Manual of Anatomy including Embryology 6
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Frazer JE. Buchanan's Manual of Anatomy, including Embryology. (1937) 6th Edition. Bailliere, Tindall And Cox, London.
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- 1 Chapter VI The Bones of the Upper Limb
- 1.1 The Clavicle
- 1.2 The Scapula
- 1.3 The Humerus
- 1.4 The Radius
- 1.5 The Ulna
- 1.6 The Carpus
- 1.7 The Scaphoid Bone
- 1.8 The Lunate Bone
- 1.9 The Pisiform Bone
- 1.10 The Trapezoid Bone
- 1.11 The Capitate Bone
- 1.12 The Hamate Bone
- 1.13 The Metacarpus
- 1.14 The Second Metacarpal Bone
- 1.15 The Phalanges
- 1.16 The Hand as a Whole
Chapter VI The Bones of the Upper Limb
The upper limb is arranged in four divisions—namely, the pectoral •r shoulder-girdle, brachium or arm proper, antibrachium or forearm, .nd manus or hand. The shoulder-girdle consists of the clavicle and capula, the arm proper comprises the humerus, the forearm is composed >f the radius and ulna, and the hand is subdivided into a carpus , com>rising eight bones, a metacarpus , consisting of five bones, and phalanges, vhich number fourteen.
The clavicle or collar-bone is situated at the lower part of the neck interiorly, where it lies above the first rib, and it extends outwards and >ackwards from the upper border of the manubrium sterni to the acronion process of the scapula. The bone presents two curves: an inner >r sternal, occupying two-thirds, with its convexity directed forwards; md an outer or acromial, extending over the outer third, with its convexity directed backwards. These curves impart elasticity to the bone. The clavicle is divided into a shaft and two articular extremities.
The shaft is usually quadrilateral in section in its inner two-thirds, )ut in many cases is triangular; it is compressed from above downwards >ver its outer third. The superior surface is for the most part narrow, )ut laterally it becomes broad. At its inner third, near the postero;uperior border, it presents a rough ridge, about inches long, for the )rigin of the clavicular head of the sterno-mastoid. At its outer expanded part it is encroached upon by the tendinous fibres of the xapezius and deltoid. Elsewhere it is covered by the skin, fascia, md platysma. The anterior surface is convex over its inner two-thirds, md concave over its outer third, where it is reduced to a mere rough border. Over the inner half it is flat and rough for the origin of the Navicular portion of the pectoralis major, and over its outer marginal hird it gives origin to the clavicular portion of the deltoid. At the nner end of the deltoid impression there is sometimes a pointed projection, known as the deltoid tubercle. The posterior surface is concave t>ver its inner two-thirds, and convex over its outer third, where it s narrowed into a rough border. The inner two-thirds overhang the mbclavian vessels and trunks of the brachial plexus, whilst the outer narginal third gives insertion to the upper fibres of the trapezius. At the inner end of the impression for these fibres, opposite the deltoid spine, there is a conical projection which extends on to the inferior surface for a little, called the conoid tubercle, for the conoid part of the coraco-clavicular ligament. About the centre of the posterior surfac there is the nutrient foramen (often double) for the nutrient arter} which is a branch of the suprascapular. The canal to which the forame: leads is directed outwards. The foramen may be situated on the inferio surface in, or close to, the subclavian groove, or there may be tw foramina, one on the posterior and one on the inferior surface, abou an inch apart. Close to the sternal end the posterior surface give partial origin to the sterno-hyoid. The inferior surface present near its sternal end the impression for the costo-clavicular ligamenl about an inch long. Just lateral to and behind this is often a smoot' oblique depression marking the point where the clavicle rests agains and presses upon the first rib. In the middle third of the lowe surface there is the subclavian groove , which extends from the rhomboii impression to near the conoid tubercle, and gives insertion to th subclavius. The groove is bounded by two lips, anterior and posterior to which the clavipectoral fascia is attached in two laminae. A
Fig. 177. —The Right Clavicle Superior View).
the outer extremity of the inferior surface there is a rough obliqu< line, called the trapezoid line , which extends forwards and outward; from the conoid tubercle, and gives attachment to the trapezoid par of the coraco-clavicular ligament. The conoid tubercle is more fulh seen here than on the posterior border, and is situated at the postero medial extremity of the trapezoid line.
The borders of the clavicle over its outer third are anterior anc posterior. The anterior border bifurcates, over the inner two-thirds into an antero-superior and antero-inferior border , which enclose be tween them the anterior surface. The posterior border bifurcates, ovei the inner two-thirds, into a postero-superior and postero-inferior border the latter forming the posterior lip of the subclavian groove. Th( antero-superior and postero-superior borders limit the superior surface the postero-superior and postero-inferior limit the posterior surface the postero-inferior and antero-inferior limit the inferior surface, and
as stated, the antero-inferior and antero-superior limit the anterioi surface.
fia sternal extremity is enlarged and covered by cartilage. As viewed on end, it is somewhat triangular, and presents a prominent )osterior angle which is directed downwards, inwards, and backwards, rhe surface is concave from before backwards, and convex from above lownwards, and it articulates with the clavicular impression on the ipper border of the manubrium sterni, an inarticular fibro-cartilage ntervening. The circumference of the sternal end is rough for the iterno-clavicular and interclavicular ligaments, except inferiorly, vhere there is a narrow articular strip for the first costal cartilage.
The acromial extremity presents an oval facet for the acromion )rocess of the scapula.
The clavicle receives its blood-supply from the suprascapular and horaco-acromial arteries.
Articulations. —Medially with the manubrium sterni and first costal cartilage, and laterally with the acromion process of the scapula.
Fig. 178.— The Right Clavicle.
A, inferior view; B, sternal extremity.
Structure.—The exterior is composed of compact bone which is hickest towards the centre, and the interior of coarse cancellated issue, the principal lamellae being disposed longitudinally. The lavicle has no medullary canal, but, towards the centre of the shaft, he medullary spaces of the cancellated tissue are of large size.
Varieties. —(1) There may be a deltoid spine. (2) The superior surface lay present a small slit-like aperture almost invariably corresponding with he position of the nutrient foramen, for one of the descending branches of the ervical plexus of nerves.
The Clavicle of the Female.—-The bone is smoother, more slender, traighter, and more cylindrical over its inner two-thirds, than that f the male. An average male English clavicle measures 6 inches; female, 5J inches.
Appears in the 18th year, and joins about 25
Ossification.— The clavicle, which is the earliest bone to ossify, has two primary centres and one secondary centre. It is preceded by a rod of connective tissue. Within the two halves of this rod collections of ‘ precartilaginous tissue ’ are formed, and within these at their contiguous ends the
primary centres appear about the sixth week. Subsequently the precartilaginous collections fuse, and thereafter the primary centres coalesce. Ossification from these two centres proceeds at first in the precartilaginous tissue, but subsequently in the cartilage to which this tissue gives place. The primary centres may fail to join, with the result that the clavicle may persist in two halves.
The secondary centre appears in the cartilage of the sternal end about the
Appears in the 6th week (intra-uterine)
-Ossification of the Clavicle.
twentieth year, and forms a mere scale which seldom covers the whole articular surface. This epiphysis joins the shaft about the twenty-fifth year (Mall and Fawcett).
It will be noticed that in bones with a shaft and one epiphysis the nutrient foramen and the canal to which it leads are directed towards that extremity which has no epiphysis. This is illustrated in the clavicle and the metacarpal, metatarsal, and phalangeal bones, and the rule may be stated in another way by saying that the nutrient artery runs away from the growing end of the bone.
The scapula or shoulder-blade is situated on the posterior aspect of the thorax, where it extends from the second to the seventh rib, being separated by muscles from the thoracic wall. It consists of a body and three processes—namely, a spine, an acromion, and a coracoid process.
The body is a thin triangular plate, and it presents two surfaces, three borders, and three angles. The costal surface , venter , or subscapular fossa is concave, and the bone forming it is for the most part thin, except near the lateral or axillary border, where there is a thick, round, elongated ridge. It gives origin to the subscapularis, except (1) along the anterior aspect of the base from the superior to the inferior angle, where the serratns anterior is inserted, and (2) over the front of the neck. The costal surface is crossed by three or four oblique ridges, which extend upwards and outwards from the base, and give attachment to intramuscular tendons of origin of the subscapularis muscle.
The dorsal or posterior surface is irregularly convex, and is divided into two unequal parts by the spine. The upper division, along with the superior surface of the spine, forms the supraspinous fossa. It represents about one-fourth of the dorsal surface, and gives origin over its inner two-thirds to the supraspinatus. In the region of the neck it presents a nutrient foramen for a branch of the suprascapular artery. The lower division, along with the inferior surface of the spine, forms the infraspinous fossa, and it represents about three-fourths of the dorsal surface. Towards the lateral border it presents an elongated eoncavity, external to which is an oblique line extending from its upper md downwards and inwards to the base near the inferior angle. The infraspinous fossa, as far out as this oblique line, gives origin to the infraspinatus, except at the upper and outer part, and it presents a nutrient foramen superiorly, close to the spine near the centre, for a branch of the circumflex scapular artery. The oblique line marks off impressions for the teres muscles and circumflex scapular artery, as follows: the teres minor arisei from about the upper two-thirds, near the centre of which there is a groove for the circumflex scapular artery, and the teres major arises from about the lower third. The impression for the latter muscle is oval; it extends on to the back of the inferior angle, and it is separated from the impression for the teres minor by a short rough line. This line gives attachment to an intermuscular septum which separates the teres muscles, and the oblique line to a septum which separates these muscles from the infraspinatus. The supra- and infraspinous fossae communicate with each other by means of the spino-glenoid notch, which lies outside the short lateral border of the spine, and transmits the suprascapular artery and nerve.
Fig. 180. — The Right Scapula (Anterior View),
The borders are upper, medial, and lateral. The upper border, which is the shortest and thinnest, extends from the superior angle to the coracoid process. Close to that process it presents the suprascapular notch. This is converted into a foramen by the suprascapular ligament, which sometimes undergoes ossification. The suprascapular nerve passes backwards beneath the ligament, and the suprascapular artery over it, whilst the inferior belly of the omo-hyoid arises from its inner part and from the adjacent portion of the upper border. The medial border is known as the base. It is the longest, intermediate in thickness, and extends from the superior to the inferior angle. It is convex, and is divisible into three parts. One part represents the base of the small triangular surface by which the spine arises from the medial border, and it gives insertion to the rhomboid minor; another extends from this to the superior angle, and gives insertion to the levator scapulae; and the third extends downwards to the inferior angle, and gives insertion to the rhomboid major. On the costal surface close to this border there is a long narrow linear impression, which widens towards the superior and inferior angles, and gives insertion to the serratus anterior. The lateral border, which is the thickest and intermediate in length, extends from the inferior angle to the lower margin of the glenoid cavity. Below that cavity it presents a rough impression, an inch long, called the infraglenoid tubercle, which gives origin to the long head of the triceps, and a little below this a groove for the circumflex scapular artery, which also marks the dorsal surface. The costal surface of the bone close to this border presents a groove over the upper two-thirds, which gives origin to many fibres of the subscapularis.
The angles are superior, inferior, and lateral. The superior angle, which is thin, is situated at the meeting of the upper and medial borders, and it forms the highest part of the body, being on a level with the second rib. Its costal surface gives insertion to a part of the serratus anterior, and its edge to a portion of the levator scapulae. The inferior angle, somewhat thick and round, is situated at the meeting of the medial and lateral borders, and it forms the lowest part of the bone, being on a level with the seventh rib. Its costal surface gives insertion to a part of the serratus anterior, and its dorsal surface gives origin to a portion of the teres major. Below the impression for the latter muscle there is sometimes a rough semilunar marking for a slip of origin of the latissimus dorsi. The lateral angle, which is massive, is situated at the upper end of the lateral border. It forms the head of the bone, and supports the glenoid cavity, which articulates with the head of the humerus.
The glenoid cavity, so named from its shallowness, is pyriform, with the narrow end upwards, and its direction is outwards and forwards. Its margin is slightly elevated and rough for the labrum glenoidale, and immediately outside the margin the capsular ligament )f the shoulder-joint is attached. About a third of the way down the interior part of this margin is a slight notch marking the attachment >f the inferior gleno-humeral ligament, and comparable with the icetabular notch in the acetabulum. Superiorly it presents a small •ough elevation, called the supraglenoid tubercle, which gives origin
o the long head of the biceps. The neck is the constricted portion vhich extends from the suprascapular notch to a point immediately ibove the infraglenoid tubercle, and it is most evident posteriorly, vhere it forms, with the lateral border of the spine, the spino-glenoid notch. In this latter situation there are numerous foramina for branches of the suprascapular artery.
Fig. 181. — The Right Scapula (Posterior View).
The spine is situated on the dorsum of the bone, which it crosses in a direction outwards and slightly upwards. It commences at the medial border in a flat triangular surface, over which the tendon receiving the lower fibres of the trapezius glides, with the intervention of a bursa. It soon becomes very prominent, and at its outer extremity it undergoes a slight twist and forms the acromion process. It is triangular, and compressed from above downwards. The superior surface forms part of the supraspinous fossa, and gives origin to fibres of the supraspinatus, whilst the inferior surface forms part of the infraspinous fossa, and gives origin to fibres of the infraspinatus. The lateral border, which is short, bounds medially the spino-glenoid notch. The anterior border is continuous with the body of the bone. The posterior border or crest presents an upper lip, which gives insertion to part of the trapezius; a lower lip, giving partial origin to the deltoid; and an intervening rough surface which is encroached upon by the tendinous fibres of these two muscles. The upper lip is often very projecting at its inner end, where the tendon receiving the lower fibres of the trapezius is inserted.
The acromion is situated at the outer extremity of the spine, and its direction is outwards, upwards, and forwards, so as to overhang the glenoid cavity. It is somewhat triangular, and is compressed from above and behind downwards and forwards. The posterosuperior surface, which is rough, gives origin at its lower part to some fibres of the deltoid, and elsewhere is subcutaneous. The anteroinferior surface, which is smooth and concave, overhangs the glenoid cavity, and is related to the subacromial bursa. The outer border is continuous with the lower lip of the posterior border of the spine, where there is a projection called the acromial angle, and this outer border gives origin to a portion of the deltoid by a series of tubercles. The acromial angle represents the metacromial process of comparative anatomy, and is a useful landmark for taking measurements of the arm. The inner border is continuous with the upper lip of the posterior border of the spine, near which it gives insertion to a part of the trapezius, whilst near the tip of the acromion it presents an oval facet for the outer extremity of the clavicle. The upper and lower margins of this facet are rough for the acromio-clavicular ligaments. The tip or apex of the process is situated at the meeting of the outer and inner borders. The acromion is pierced by many arterial twigs derived from the acrominal rete.
The coracoid process, which is strong and curved, springs from the upper aspect of the head immediately lateral to the suprascapular notch. It is directed at first upwards and forwards for about \ inch, and then, bending sharply, it is directed forwards and outwards to terminate in a blunt tip. I he ascending portion is compressed from before backwards. Its anterior surface is related to the subscapularis, and the posterior to the supraspinatus. Its outer border gives attachment to a portion of the coraco-humeral ligament, and the inner border, which bounds the suprascapular notch laterally, gives attachment at its upper part to the suprascapular ligament. The horizontal portion ot the process is compressed from above downwards. Its antero-medial border, which is long and convex, and the adjacent portion of the superior surface, give insertion anteriorly to the pectoralis minor, W posteriorly they give attachment to the costo-coracoid ligament and the clavipectoral fascia. The postero-lateral border , which is short, receives the fibres of the coraco-acromial ligament, and gives attachment to a portion of the coraco-humeral ligament. At the back part of the antero-medial border there is the conoid impression for the conoid Dart of the coraco-clavicular ligament. On the back part of the superior surface there is the trapezoid line, for the trapezoid part of the coracodavicular ligament, which extends forwards and outwards from the onoid impression, and the pectoralis minor is sometimes inserted into his surface and may make a groove upon it. The inferior surface of he horizontal portion is smooth and concave. The tip or apex, which s blunt, gives origin to the conjoined short head of the biceps and
Appears about the 16th Year, and joins about 25
Subcoracoid Epiphysis. Appears at 10th Year, and joins at 16
Apical Epiphysis. Appears about 18th Year, and joins about 25 Accessory Coracoid. Appears about puberty, and soon joins
Coracoid Element. Appears in 1st Year, and joins at 15
• 1 Appear about the 16th Year,
_ 1 and join Spine about 25
. Line of junction of Coracoid Element
Body. Appears in 2nd Month
Appears about the 16th Year, and joins about 25
Fig. 182.—Ossification of the Scapula.
coraco-brachialis. It is useful to notice that the tip of the coracoid process forms a landmark for reaching the shoulder-joint from in front, just as the metacromial tubercle does behind.
The coracoid process of man represents the coracoid bone of monotremata and lower vertebrates.*
Articulations. —By its acromion process with the outer extremity of the clavicle, and by the glenoid cavity with the head of the humerus.
Some morphologists, however, regard it as an ossified myocomma between the neck and shoulder muscles, in which case the mammalian clavicle may not be homologous with the reptilian.
Structure. — The scapula is a flat or tabular bone, and is composed of two tables of compact bone. In the head, lateral border, inferior angle, and processes there is cancellous tissue between the two tables, but in the central portions of the supra- and infraspinous fossae there is none, and the two tables coalesce, so that the bone is very thin and transparent.
Varieties. —(1) Suprascapular foramen due to ossification of suprascapular ligament. (2) Fenestrated scapula, presenting one or more perforations in the subscapular fossa. (3) Separation of the acromion process, which may be connected with the spine by a plate of cartilage, or by fibrous tissue. (4) Imperfect synostosis of the coracoid process, which, however, is extremely rare. (5) An articular facet on the coracoid process for the clavicle.
Ossification. —The scapula has one primary centre and eleven secondary centres. The primary centre appears in the body a little distance from the neck about the eighth week.
The coracoid process, cartilaginous at birth, has four secondary centres—
coracoid, subcoracoid, supracoracoid, and apical. The coracoid centre appears before the end of the first year, and gives rise to the chief part of the process, which joins about the fifteenth year. The subcoracoid centre appears about the eighth to tenth year, and soon joins the main coracoid. It forms the triangular part of the process which enters slightly into the extreme upper and inner part of the glenoid cavity. The supracoracoid centre appears about the eighteenth year, and forms a thin laminar epiphysis on the upper surface of the process. It joins about the twenty-fifth year. The apical centre appears about the eighteenth year, and forms an epiphysis which caps the tip of the process, and joins about the twenty-fifth year.
Acromial Process. —The inner or basal portion is ossified from the spine, which in turn is ossified from the primary centre for the body. The greater portion constitutes an epiphysis, which has two secondary centres. These appear about the sixteenth year and soon join. The acromial epiphysis usually joins the rest of the process about the twenty-fifth year or earlier. Union, however, may not take place, and then the acromial epiphysis forms a separate acromial bone, connected with the rest of the process by cartilage or by fibrous tissue, and this condition may simulate a fracture.
Glenoid Cavity .—The fundus or bed of this cavity is ossified from the primary centre for the body, and its extreme upper and inner part is formed from the subcoracoid centre. Besides these the cavity has two special secondary centres —superior and inferior. The superior glenoid centre appears about the tenth year, and it joins the fundus or bed of the fossa about the sixteenth year. The inferior glenoid centre appears about the sixteenth year, and forms the glenoid epiphysial plate. It joins about the twentieth year, and gives rise to the slight concavity of the fossa.
The other secondary centres are allocated as follows: (1) Posterior border of spine; (2) inferior angle; (3) base. These centres appear about the sixteenth year, and join about the twenty-fifth year. It must be realized that all these centres are not invariably present in any one specimen.
Fig. 183 shows a diagram of a generalized shoulder-girdle—that is to say, an ideal from which any existing arrangement may be obtained by a suppression or fusion of parts.
The glenoid cavity, where the humerus articulates, is the point of primary importance; it is fixed to the front of the double sternum by the coracoid, and another stay, the precoracoid, moors it to the mid-ventral line of the root of the neck. This bar is usually perforated at its distal end by a foramen.
The ventral ends of the coracoid and precoracoid are connected by the epicoracoid.
The dorsal part of the glenoid cavity is formed by the scapula, a triangular plate with dorsal and ventral surfaces, which is still further fixed to the mid-ventral line of the neck by two membrane bones, the clavicle and interclavicle.
Where the clavicle is attached to the preaxial border of the scapula is a process representing the spine and acromion, and the medial border of the scapula articulates with another plate, the suprascapula, represented by the epiphyses of the medial border in the human shouldergirdle.
The sternum is shown as two parallel bars, each formed by the union of the ventral ends of ribs which have fused.
Fig. 183.—Scheme of Generalized Shoulder-Girdle.
The humerus extends from the shoulder to the elbow, its direction being downwards and slightly inwards. It is a long bone, and is divisible into a shaft and two extremities, upper and lower.
The upper extremity includes the head, anatomical neck, greater and lesser tuberosities, commencement of the bicipital groove, and surgical neck. The head, which is almost hemispherical, is smooth, convex, and covered by cartilage. Its direction is upwards, inwards, and backwards, and it articulates with the glenoid cavity of the scapula. The anatomical neck is the constriction immediately beyond the cartilage of the head. It is best marked above, especially between the head and greater tuberosity, and it gives attachment to the capsular ligament of the shoulder-joint. It is pierced by numerous nutrient foramina. The greater tuberosity is situated obliquely on the outer surface, immediately beyond the anatomical neck. It presents three flat muscular impressions—an upper for the insertion of the supraspinatus, a middle for the infraspinatus, and a lower for the teres minor, which latter muscl( continues to take insertion into a rough marking on the shaft for al least \ inch below the lower impression. The lesser tuberosity is ar oval prominence situated on the anterior aspect immediately beyond the anatomical neck. It gives insertion to the subscapularis, whicl continues to take insertion into the adjacent part of the shaft for aboul | inch. The commencement of the bicipital groove, which lodges the long tendon of the biceps, lies between the two tuberosities, when it is bridged over by the transverse ligament. It presents a large nutrient foramen close to the greater tuberosity for an offset of the ascending branch of the anterior circumflex humeral artery. The surgical neck is the constriction below the tuberosities.
The upper extremity of the humerus receives its principal bloodsupply from the anterior and posterior circumflex humeral arteries.
The shaft is almost cylindrical in its upper half, but it is laterally expanded and triangular in its lower half. The anterior aspect presents superiorly the bicipital groove, which commences between the tuberosities, where it is deep, and passes downwards and slightly inwards, terminating about the junction of the upper and middle thirds. It is bounded by two rough lips, lateral and medial. The lateral lip, which is the more prominent, gives insertion over about its lower three-fourths to the pectoralis major, this portion being called the pectoral ridge. It is in line with the anterior border of the lower half of the shaft. The medial lip gives insertion over about its lower two-thirds to the teres major, this portion being known as the teres ridge. It is in line with the medial border of the lower half of the shaft. The floor of the groove over about its middle third gives insertion to the latissimus dorsi. The groove is occupied by the long tendon of the biceps, invested by a tubular prolongation of the synovial membrane of the shoulderjoint, and the ascending branch of the anterior circumflex humeral artery. I he outer aspect of the shaft presents a rough V-shaped mark, called the deltoid tuberosity, for the insertion of the deltoid. The point of the V, which is embraced by two slips of brachialis, is at the centre of the shaft, whence it extends upwards for about 2 inches. Its anterior margin is in line with the pectoral ridge, and its posterior margin bounds superiorly the lower part of the spiral groove. On the inner aspect of the shaft, about the centre,there is a rough line about 11 inches long, placed in the course of the medial border, for the insertion of the coraco-brachialis. Immediately below this line is the principal nutrient foramen for the nutrient branch of the brachial aitery, the canal to which it leads being directed downwards. The posterior and lateral aspects of the upper part of the shaft present a winding groove, called the spiral groove, for the radial nerve and profunda brachii vessels. It commences in the upper third posteriorly, and is directed downwards and forwards on to the lateral surface, where it terminates a little below and behind the apex of the deltoid tuberosity. The lower part of this groove is occupied by a pointed slip of brachialis. In the upper part of the groove there is usually a nutrient foramen for a branch of the profunda brachii artery. On the posterior aspect of the shaft, over about its upper third, lateral to the spiral groove, there is a rough marking which gives origin to the latera' head of the triceps, extending as high as the lower part of the insertion of the teres minor. The medial head of the triceps commences to arise in a pointed manner from the back of the shaft medial to the spiral groove, where it reaches a little above the lower border of the tendon of the teres major.
Fig. 184. — The Right Humerus (Anterior View).
The lower half of the shaft, being triangular, presents three surfaces and three borders. The posterior surface, which is Hat, terminates at the olecranon fossa, and it gives origin to most of the fibres of the medial head of the triceps. The lateral and medial surfaces, as well as the anterior border which separates them, give origin to brachialis. The anterior border, which is round, separates the lateral surfaces, and is in line with the anterior margin of the deltoid tuberosity, and, aboye this, with the lateral lip of the bicipital groove. The lateral bordey is called the lateral supracondylar ridge. It is sharp and prominent, and extends from the lateral epicondyle to the spiral groove. It gives attachment to the lateral intermuscular septum. Anteriorly its upper two-thirds give origin to the brachio-radialis, and the lower third to the extensor carpi radialis longus. Posteriorly it gives origin to the medial head of the triceps. The medial border forms the medial supracondylar ridge, and is not so prominent as the lateral. It commences at the medial epicondyle, and it can be followed up through the line for the insertion of the coraco-brachialis into the medial lip of the bicipital groove. It gives attachment to the medial intermuscular septum. Anteriorly it gives origin to brachialis, posteriorly to the medial head of the triceps, and in its lower part to some fibres of the humeral head of the pronator teres. The medial surface of the shaft, in front of the medial supracondylar ridge, and about 2\ inches above the medial epicondyle, sometimes presents a sharp spur-like projection directed downwards, called the supracondylar process. When present it gives attachment to a fibrous band which passes to the medial epicondyle, and gives origin to a third head of the pronator teres. In such cases the band forms an arch through which the median nerve passes, and frequently the brachial artery. The supracondylar process represents a portion of bone which forms a supracondylar foramen in many vertebrates.
There is a very archaic lizard called Sphenodon, in which there is not only this entepicondylar foramen for the median nerve on the inner side of the humerus, but an ectepicondylar foramen for the radial nerve on the outer side. It has been suggested that the shaft of the humerus between the two foramina and the bars bounding the foramina on each side represent the remnants of three fin rays of the pectoral limb of the fish. Be this as it may, the process in man sometimes causes trouble and difficulty in diagnosis.
The lower extremity presents at either side the medial and lateral epicondyles, and inferiorly a transversely elongated articular surface covered by cartilage, and divided by a vertical curved ridge into a lateral part, called the capitulum, and a medial, called the trochlea. Above the capitulum in front there is a rough transverse depression, called the radial fossa. Above the trochlea in front is the coronoid fossa, and above it posteriorly is the olecranon fossa.
Fig. 185. — The Right Humerus (Posterior View).
The medial epicondyle ( epitrochlea ) is very prominent, and is directed inwards and slightly backwards. Its lower part and the adjacent portions of its anterior and posterior aspects give attachment to the medial ligament of the elbow-joint. Its anterior aspect gives origin to the common tendon of the humeral head of the pronator teres, flexor carpi radialis, palmaris longus, part of the flexor digitorum sublimis, and the humeral head of the flexor carpi ulnaris. Behind the medial epicondyle, close to the trochlea, is the ulnar groove, through which the ulnar nerve passes.
The lateral epicondyle is much less prominent than the medial. Anteriorly it gives origin to the common tendon of the extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi, extensor carpi ulnaris, and supinator. Posteriorly it presents an impression for the anconeus, and interiorly a depression near the capitulum for the lateral ligament of the elbow-joint.
The capitulum mainly takes the form of a rounded eminence. It is limited to the anterior and inferior aspects of the bone, and articulates with the cup-shaped depression on the head of the radius. Medial to the rounded portion there is a groove for the play of the inner convex part on the head of the radius. The radial fossa receives the anterior margin of the head of the radius in complete flexion of the elbow-joint.
The trochlea is pulley-shaped, and turns completely round from the front to the back of the bone, becoming rather broader posteriorly. It is concave from side to side, and convex from before backwards. The medial border is more prominent and thicker than the lateral, and extends lower down. As viewed from in front, the borders are inclined downwards and slightly inwards, but posteriorly they incline upwards and slightly outwards, and so the trochlea is here brought into the centre of the bone. The trochlea articulates with the trochlear of the ulna. The coronoid fossa receives the coronoid process of the ulna in flexion of the elbow-joint, and the anterior ligament is attached just above it. The olecranon fossa, much larger than the coronoid, receives the olecranon process of the ulna in extension of the joint, and its margins give attachment to the posterior ligament. The portion of bone which separates the two fossae is thin, and is sometimes perforated by a foramen, called the supratrochlear foramen.
In the vicinity of the lower extremity there are numerous nutrient foramina for branches of the profunda, ulnar collateral, and supratrochlear of the brachial, radial and ulnar recurrent, and interosseous recurrent, arteries.
Articulations.— Superiorly with the scapula, and inferiorly with the radius laterally, and ulna medially.
Structure. — The shaft is composed of compact bone, which is thicker at the centre than at the extremities. It contains a medullary anal, lined with a thin coating of cancellated tissue, which does not 3 ach higher than the surgical neck of the bone. The articular exremities are filled with cancellated tissue, except at the surface, where aere is a thin layer of compact bone.
Appears in the 1st Year 1
Appears in the 3rd Year Appears in the 5th Year
All three coalesce at the 6th Year, and join at 20
Appears at the 6th to 7th Week(intra-uterine
Varieties. — These are (i) a supracondylar process, and (2) a supratrochlear iramen.
Ossification. —The centre for the shaft appears in the sixth to seventh week, tid at birth both ends are usually cartilaginous: there is often a centre present t birth, however, in the head of the bone, probably more commonly in girls, he upper end (the growing end) has three centres—for the articular head and ich of the tuberosities. That >r the head appears usually l the first few months after irth (M.), that for the greater iberosity within the year (F.)
just after this (M.), while the mtre for the lesser tuberosity )mes between four and five;
.1 these centres are rather iriable. They fuse together,
>rming a compound proximal hphysis, at four to five in Dys, about a year earlier in rls. The whole epiphysis joins le shaft at about twenty (M.), at in women about eighteen.
The lower end has four
condary centres, the most ledial of which is separated om the others by a downward rolongation of the shaft. The ipitular centre appears first
the second to third year, hat for the medial epicondyle,
Le separated centre, shows in ie fifth (F.) to eighth (M.) year. The trochlear centre is found at nine (F.) or
n (M.), and that for the lateral epicondyle about two years later. The shaft isification extends down about the time of puberty between the trochlear and edial epicondylar centres. The others join together to form a lower epiphysis, hich fuses with the shaft at about fourteen in girls and seventeen in boys; le medial epicondyle joins the shaft about a year or less afterwards.
Appears in the 14th Year .
Appears in the 5th Year, and joins at 18
Appears in the 3rd Year Appears in the 12th Yeai
The Lateral Epicondyle, Capitulum, and Trochlea, having previously coalesced, join at 17
Fig. 186. —Ossification of the Humerus (M.).
Epiphyses and the Law of Ossification.
The law of ossification applicable to long bones with an epiphysis r epiphyses at either end is as follows: the epiphysis or epiphyses, at 'e end towards which the nutrient foramen and the canal to which it leads v e directed, are the last to show signs of ossification, hut they are the first 1 join the shaft. The only exception to (a part of) this rule occurs in ie fibula .
It is obvious that a bone will make most growth at that end where ie epiphysial line remains longest, and we have seen, in the case of ie clavicle, that the nutrient artery runs away from the growing end f the bone.
It has now only to be realized that the artery nearly always ru towards the elbow and away from the knee, and it follows that t bones of the upper extremity grow from the ends away from t elbow, while in the lower extremity they grow from the ends near< the knee. Whether the epiphyses appear early or late seems to ha no influence on the growth of a bone; indeed, it does not make a: difference whether there is a bony epiphysis or not until that epiphy fuses with the shaft and the epiphysial line is thus obliterated.
We have seen that the epiphysis of the clavicle does not appe until eighteen, but by that time the bone is almost fully grown. It interesting to note that in the tailed amphibia (newts, etc.) the epiphys remain cartilaginous throughout life, while in birds no bony epiphys occur, but the bony shaft grows to the very end of the cartilage, ai growth stops when the epiphysial line has reached the articular surfac
It will be obvious that the epiphyses of the humerus are divide into two perfectly distinct groups. One of these, comprising tj head, the capitulum, and the trochlea, consists of articular or pressu epiphyses, and these are the ones which, by their fusion with the shal eventually stop the growth of the bone.
Another group, consisting of the greater and lesser tuberosities ar the two epicondyles, are non-articular and associated with the pull muscles, and so are often spoken of as traction epiphyses.
A third variety of epiphyses, not present in the humerus, but ind cated in the coracoid process and medial border of the scapula, represei parts of the skeleton which were once of greater importance than the are now; and for these the name of atavistic epiphyses is suggested.
The radius is the lateral bone of the forearm (which is assume to be in a position of supination). It is parallel with, and shorter thai the ulna, and extends from the elbow to the wrist. It is a long bon< and is divisible into a shaft and two extremities.
The upper extremity presents a head and neck. The head is dis< shaped, and covered by cartilage, both on its upper surface and cii cumference. The upper surface , at its centre, presents a depressio which articulates with the rounded portion of the capitulum of th lumerus in flexion of the elbow-joint. Around this depression th surlace is convex, especially on the inner side, and this portion glide on the inner grooved part of the capitulum. The circumferentia cartilage is deeper on the inner aspect than elsewhere, and this portioi articulates with the radial notch of the ulna, whilst the remainde plays within the orbicular ligament. The constricted portion below th iea is ca led the neck. It is cylindrical, and its upper part is embrace( y me annular ligament, whilst beyond this on the outer and fron aspec l gives insertion to a few fibres of the supinator. The uppe ex remi y presents several nutrient foramina for branches of the radia i ecurrent and interosseous recurrent arteries.
The shaft increases in size from above downwards, and is curved, he convexity being directed outwards and slightly backwards. This mrve imparts elasticity to the bone, and guards it against the shocks 0 which it is so much exposed from the fact that it supports the hand, rhe shaft is triangular, and presents superiorly, on its antero-medial ispect just below the neck, an oval eminence, called the tuberosity of 'adius. This is divided vertically into two parts, a rough posterior portion which gives insertion to the tendon of the biceps, and a smooth interior part which is separated from that tendon by a bursa. Below he radial tuberosity the shaft presents three borders and three suraces. The anterior border extends from the lower and anterior part )f the tuberosity to the anterior border of the styloid process. In its ipper third it crosses the shaft obliquely downwards and outwards, his portion of it being called the anterior oblique line. This line imits laterally the insertion of supinator, and medially the origin of the lexor pollicis longus, whilst its prominent edge gives origin to the hin radial portion of the flexor digitorum sublimis. The interosseous border commences at the lower and back part of the radial tuberosity, md near the lower extremity of the shaft it divides into two ridges, vhich pass to the anterior and posterior margins of the ulnar notch. Kt its commencement it is round and indistinct, and immediately )elow the tuberosity it gives attachment to the oblique cord. Over he rest of its extent it is sharp and wiry for the attachment of the nterosseous membrane, which is also connected with the posterior of he two lower divisions. The posterior border extends from the back of he tuberosity to the prominent dorsal tubercle about the centre of the >osterior border of the lower extremity. In its upper third it crosses he shaft obliquely downwards and outwards, this portion of it, vhich is prominent, being called the posterior oblique line. This line imits the insertion of supinator above, and the origin of the abductor )ollicis longus below.
The anterior surface is situated between the anterior and inter•sseous borders. In the upper two-thirds it is concave, and gives •rigin to the flexor pollicis longus. In the lower third it is flat and xpanded, and this portion gives insertion to the pronator quadratus, except close to the anterior border of the lower extremity, where it
gives attachment to the anterior radio-carpal ligament of the wristoint. The anterior surface presents the nutrient foramen about the unction of the upper and middle thirds. The direction of the canal o which it leads is upwards, and it gives passage to the nutrient branch f the anterior interosseous artery. The portion of bone between the nterior oblique line, the lower part of the front of the neck, and the uberosity gives insertion to a portion of supinator. The lateral surface 5 situated between the anterior and posterior borders. It is convex rom above downwards, and from side to side. In its upper third it ives insertion to supinator; at its centre there is a rough impression, ully an inch long, for the insertion of pronator teres; and below this supports the tendons of the extensores carpi radialis longus et brevis and is crossed obliquely by the tendons of the abductor pollicis longus nd extensor pollicis brevis. The lateral surface also supports the irachio-radialis, which is inserted into its lower extremity close to the iase of the styloid process. The posterior surface is situated between he posterior and interosseous borders. Above the posterior oblique ne it is covered by supinator, which takes insertion into its outer alf. Below the posterior oblique line it is concave over about the liddle third, where it gives origin from above downwards to the bductor pollicis longus and extensor pollicis brevis. The lower third 3 broad and convex, and it supports the tendons of the extensor lollicis longus, extensor digitorum, and extensor indicis.
The lower extremity is large and cuboidal. Laterally it presents he styloid process, medially the ulnar notch, and inferiorly the carpal .rticular surface, the latter two being covered by cartilage. The tyloid process projects downwards as a stout conical process, terminatng in a round tip which gives attachment to the lateral ligament of the wrist-joint. The inner surface is covered by the cartilage of the carpal rticular surface. The outer surface presents a groove directed downwards and slightly forwards, and subdivided into two compartments, he anterior of which transmits the tendon of the abductor pollicis 3 ngu&, and the posterior that of the extensor pollicis brevis. This
roove is separated from the pronator surface in front by a prominent ubcutaneous ridge which gives attachment to the extensor retinacu11m. The anterior surface supports a portion of the radial artery.
The ulnar notch is concave from before backwards, and articulates with the outer convex surface of the head of the ulna.
The carpal articular surface is of large size, and its plane is oblique, >eing sloped outwards and a little downwards. It is concave from >efore backwards, and from side to side, and is divided into two parts >y an antero-posterior elevation. The outer division is triangular, its artilage being prolonged on to the inner surface of the styloid process, md it articulates with the scaphoid bone. The inner division is quadilateral, and articulates with the lunate bone. It is separated from the ilnar notch by a sharp concave margin, which gives attachment to he base of the triangular interarticular disc. Immediately above the interior border there is a rough surface for the attachment of the interior radio-carpal ligament. The posterior border is on a slightly ower level than the anterior, and is irregularly convex. It presents Lbout its centre a prominent elevation, called the dorsal tubercle, md is divided into three grooves—outer, middle, and inner. The mter groove, which is broad, is bounded laterally by a ridge which sepaates it from the groove on the outer surface of the styloid process, and nedially by the dorsal tubercle. It is usually subdivided by a faint ine into two compartments, the outer of which transmits the tendon >f the extensor carpi radialis longus, and the inner that of the extensor mrpi radialis brevis. The middle groove, narrow and deep, is directed rom above downwards and outwards, and is bounded laterally by the lorsal tubercle, which slightly overhangs it, and medially by an oblique ridge separating it from the inner groove. It transmits the tendon of he extensor pollicis longus. The inner groove is single, and transmits he tendons of the extensor digitorum, the extensor indicis, the posterior iterosseous nerve, and the anterior interosseous artery. It is separated rom the ulnar notch by a sharp ridge which, with the ulna in position, 'Ounds a groove for the tendon of the extensor digiti minimi. The
Fig. i88.—The Right Radius (Posterior Surface]
Fig. 189.—The Lower Ends of the Left Radius and Ulna AS SEEN FROM BELOW IN PRONATION.
The dorsal aspect is upwards.
ridges separating the grooves give attachment to deep expansions of he extensor retinaculum ligament, which, with the ligament, convert the grooves into fibro-osseous canals.
The lower extremity presents several nutrient foramina for branches >f the anterior and posterior interosseous arteries, and anterior and posterior carpal networks.
Articulations. — Superiorly with the capiulum of the humerus and radial notch cavity )f the ulna, and inferiorly with the head of he ulna, scaphoid, and lunate.
Structure. — This is similar to that of long Dones. At the lower extremity the cancellous issue extends upwards for about ij inches ibove the styloid process, this level being the site of Colles’ fracture.
Ossification. — A shaft centre appears in the seventh veek; the ends and tuberosity are cartilaginous at )irth. The distal (growing end) centre comes in the lecond year in boys, in the first year in girls. Union
vith the shaft about nineteen or later in boys, and ^ _ 0ssIFICATION it seventeen or earlier m girls. „ OF THF r adius (M 1
The centre for the head appears from four to six, OF THE radius
np rlipr rlufpQ fnr ptfIci
The tuberosity is formed by the main shaft centre, but occasionally an jpiphysial cap develops on it about puberty, with junction in a short time.
The ulna is the medial bone of the forearm (which is assumed to be in a position of supination). It is parallel with, and longer than, the radius, and extends from the elbow to the wrist, being separated from the latter joint by the triangular interarticular disc. It is a long bone, and is divisible into a shaft and two extremities, the upper of which is of large size.
The upper extremity presents the olecranon and coronoid processes, and the trochlear and radial notches. The olecranon forms the highest part of the bone, and is curved forwards at its upper part. It is largely subcutaneous. Superiorly it presents a broad, flat, quadrilateral surface, at the back part of which is a rough elevation for the insertion of the triceps. In front of this there is a smooth area where a bursa intervenes between that muscle and the bone when the elbow is flexed. At its anterior part, near the anterior margin, there is a narrow transverse impression for part of the posterior ligament of the elbow-joint. The superior surface is limited anteriorly by a sharp convex border, projected at its centre into a process, called the beak , which overhangs the upper part of the trochlear notch, and is received into the olecranon fossa of the humerus in extension of the joint. The anterior surface is directed downwards and forwards, and forms the upper part of the trochlear notch. The posterior surface, smooth, flat, and triangular, is subcutaneous, and covered by a bursa. The inner surface presents a tubercle for the ulnar head of the flexor carpi ulnaris, and the inner border gives attachment to the posterior part of the medial ligament of the elbow-joint. The outer surface gives insertion to a portion of the anconeus, and the outer border gives attachment to fibres of the posterior ligament of the joint.
The coronoid process is pyramidal, with the base attached to the rest of the ulna, and the linear apex directed forward. The superior surface forms the lower and anterior part of the trochlear notch. The inferior surface is rough and concave, and the roughness is prolonged upon the anterior surface of the shaft for about an inch, giving rise to a triangular impression, the inner half of which gives insertion to brachialis. The upper part of this surface, close to the. anterior border of the process, affords attachment to the anterior ligament of the elbow-joint. The lower pointed portion presents laterally a rough prominence, called the tuberosity, which gives insertion to fibres of brachialis, and attachment to the oblique cord. The anterior margin is sharp, convex, and curved slightly upwards, and it is projected at its outer part into a process, called the beak, which is received into the coronoid fossa of the humerus in flexion of the elbow-joint. The inner surface gives attachment to the anterior portion of the medial ligament of the elbowjomt, and at its upper part it presents a tubercle for the ulnar head of the flexor digitorum sublimis. Leading downwards from this there is a short ridge for the origin of the deep head of the pronator teres, be ow which a slip of the flexor pollicis longus sometimes arises. Behind the flexor sublimis tubercle there is a depressed surface which gives origin to the highest fibres of the flexor digitorum profundus. The outer surface presents the radial notch.
The trochlear notch, which articulates with the trochlea of the humerus, when viewed from the side, forms half a circle. The upper half of the cavity is formed by the anterior surface of the olecranon process, and the lower half by the upper surface of the coronoid process. It is constricted at the centre by a notch at either side, which marks the meeting of the olecranon and coronoid processes, the inner notch being bridged over by a fibrous band with which the middle part of the medial ligament of the elbow-joint blends. The cartilage of the cavity is sometimes broken up at this part by a narrow, rough, transverse interval. Extending from the beak of the olecranon to the beak of the coronoid there is a longitudinal elevation, which divides the cavity into two.
The radial notch, which is situated on the outer surface of the coronoid process, is concave from before backwards, and articulates with the inner aspect of the head of the radius. Its anterior and posterior margins give attachment to the cornua of the annular ligament.
The upper extremity presents several nutrient foramina for branches of the anterior and posterior ulnar recurrent and interosseous recurrent arteries.
The shaft diminishes in size from above downwards, and is triangular in its upper three-fourths, where it is slightly curved, with the convexity directed backwards. In the lower drical, being flattened in front. It
Fig. 191.—The Right Ulna (Posterior Surface).
fourth it is slender and subcylinpresents three borders and three
surfaces. The anterior border extends from the flexor sublimis tubercle on the inner margin of the coronoid process to the front of the styloid process. Over its upper three-fourths it is round, and gives origin to fibres of the flexor digitorum profundus. Over its lower fourth it is sharp, and gives origin to the pronator quadratus. The posterior border extends from the apex of the triangular subcutaneous surface on the back of the olecranon to the back of the styloid process. Over its upper two-thirds it gives attachment to a strong aponeurosis, and common origin to the flexor and extensor carpi ulnaris, and flexor digitorum profundus, but the practical point about it is that it is subcutaneous from the olecranon to the styloid processes, and by running a finger down it a fracture may be detected easily. The lateral or interosseous border extends from the apex of the bicipital hollow, about 2 inches below the radial notch, to the outer aspect of the head. Over the middle three-fifths of the shaft it is sharp and prominent, but over the lower fifth it is very faint. It gives attachment to the interosseous membrane.
The anterior surface is situated between the anterior and interosseous borders. It is concave over its upper three-fourths, and gives origin to part of the flexor digitorum profundus. The lower fourth is flat, and gives origin to the pronator quadratus. This surface presents the nutrient foramen a little above the centre, the direction of the canal to which it leads being upwards. It gives passage to the nutrient branch of the anterior interosseous artery. The medial surface is situated between the anterior and posterior borders. Over its upper two-thirds it gives origin to part of the flexor digitorum profundus, the lower portion being subcutaneous. The posterior surface is situated between the posterior and interosseous borders, and is directed backwards and outwards. It presents superiorly the oblique line , which extends from the supinator ridge on the posterior margin of the bicipital hollow to the posterior border at the junction of the upper and middle thirds. The triangular portion above this line is called the anconeal surface, which extends over the outer surface of the olecranon. It gives insertion to the anconeus. The posterior surface, below the oblique line, is divided into two lateral parts by a vertical ridge. The inner portion has the extensor carpi ulnaris playing over it, and the outer gives origin, from above downwards, to the abductor pollicis longus, extensor pollicis longus, and extensor indicis. On the outer aspect of the shaft superiorly there is a triangular depression, which commences immediately below the small radial notch, and extends downwards for about 2 inches. It is bounded in front and behind by prominent lips, the anterior of which passes above into the outer margin of the coronoid process, and the posterior into the posterior margin of the radial notch. The upper part of the posterior lip, which is prominent, is called the supinator ridge , and it gives origin to a part of supinator. The two lips form by their meeting the commencement of the lateral or interosseous border. The anterior part of this surface superiorly receives the tuberosity of the radius, with the tendon of insertion of the biceps, in pronation, whilst the posterior part gives origin to fibres of supinator.
The lower extremity is small, and presents a head and styloid process. These are separated behind by a groove for the tendon of the extensor
arpi ulnaris, and below by a rough pit which gives attachment to the rpex of the triangular interarticular disc. The outer aspect of the head is convex, and covered by cartilage for articulation with the ulnar notch of the radius, a portion of the synovial membrane, called membrana sacciformis, intervening. The inferior surface, also covered by cartilage, is flat, and is related to the upper surface of the triangular interarticular disc.
The styloid process, of small size and subcutaneous, projects downwards from the posterior and inner part of the head (mainly from the back part), and it terminates in a round tip which gives attachment to the medial ligament of the wristjoint.
When the hand is pronated it must be realized that the knob on the ulnar side of the wrist, which forms such a prominent Landmark, is not the back, but the front of the head of the ulna.
The lower extremity presents several nutrient foramina for branches of the anterior and posterior interosseous arteries.
Articulations. — Superiorly with the trochlea of the humerus, and the inner aspect of the head of the radius; inferiorly with the ulnar notch of the radius, and the triangular interarticular disc, the latter structure separating it from the os triquetrum.
Structure.— This is similar to that of long bones.
Ossification. —The ulna ossifies in cartilage from one primary, and two secondary, centres. The centre for the shaft appears during the seventh week: this forms the coronoid process by extension. The ends of the bone are cartilaginous at birth. The epiphysial centre for the lower end appears at about frve to six years in boys, about six months earlier in girls. They unite with the shaft at nineteen (M.) or seventeen (F.) approximately.
The centre for the olecranon appears about ten (M.) or eight (F.), and joins the shaft about seventeen (M.) or fourteen to fifteen (F.). It only forms the recurved piece of the olecranon, and there is often an additional centre for the tip.
An occasional accessory centre for the styloid process is described.
Fig. 192.—Ossification of the Ulna (M.).
The carpus or wrist is composed of eight short bones, which are arranged in two rows, four in each row. The rows are called first or proximal , and second or distal. The bones of the first row, from without
inwards, are called scaphoid, Innate, triquetral, and pisiform; whils those of the second row, in a similar order, are named trapezium trapezoid, capitate, and hamate.
The Scaphoid Bone
The scaphoid bone, which is characterized by its boat-like shape lies with its long axis oblique, the broad end being directed upward and inwards, and the narrow end or prow downwards, outwards, anc forwards. Superiorly it presents a convex articular surface for th< radius, which encroaches on the dorsal aspect. Inferiorly it als( presents a convex articular surface directed downwards, outwards and backwards, which likewise encroaches on the dorsal aspect, anc is divisible into two parts—an outer for the trapezium, and an innei for the trapezoid. The medial surface presents two articular facets —i superior, crescentic, narrow from above downwards, and looking inwards for the lunate; and an inferior, large, concave, and directed downward as well as inwards, for the outer side of the head of the capitate. The lateral aspect takes the form of a rough border, extending from the radial surface to the tubercle, and giving attachment to the lateral ligament of the wrist-joint. At its lower end there is a prominent tubercle, directed forwards, which gives attachment to fibres of the flexor retinaculum and abductor pollicis brevis. The palmar surface is rough and triangular. The dorsal surface, being encroached upon by the superior and inferior convex articular surfaces, is reduced to a rough oblique groove for the posterior ligament of the wrist.
Fig. 193.—The Right Scaphoid Bone.
A, posterior view; B, medial view.
The tubercle of the scaphoid is a useful surgical landmark, and can be felt on the outer side of the wrist just below the styloid process of the radius.
Articulations . — Superiorly with the radius, inferiorly with the trapezium and trapezoid, and medially with the lunate and capitate.
The Lunate Bone
The lunate bone is characterized by the crescentic concavity on its nferior surface. Superiorly it presents a quadrilateral, convex, articllar surface for the radius, which encroaches on the dorsal aspect, rhe inferior surface is deeply concave from before backwards. The greater part of it articulates with the upper surface of the head of the capitate, and the narrow inner strip with the upper border of the lamate. The lateral surface, narrow from above downwards, presents l crescentic facet for the scaphoid. The medial surface, which is nclined downwards and outwards, is deep from above downwards, md presents a quadrilateral facet for the triquetral. The palmar and lor sal surfaces are rough, the former being large, convex, and quadriateral, and the latter small and flat.
Fig. 194.—The Right Lunate Bone.
A, medial view; B, supero-lateral view.
Articulations. — Superiorly with the radius, inferiorly with the apitate and hamate, laterally with the scaphoid, and medially with the riquetral.
The Triquetral Bone.
Inferior Surface for Hamate
- Lateral Surface for Lunate
The triquetral bone is characterized by its resemblance to a wedge, t pyramid, and it lies obliquely with the base directed outwards and upwards. The lateral surface, which corresponds with the base, iresents a quadrilateral facet for the iinate. The medial surface, which epresents the rounded apex, is of united extent, and rough for the nedial ligament of the wrist-joint, he palmar surface has..a circular, lean-cut, flat facet, which occupies ather more than the inner and lower alf, and articulates with the pisiorm, the rest of the surface being ough. The supero-posterior surface is divisible into two parts, outer nd inner. The outer portion, which is close to the base, presents convex facet for the inferior surface of the triangular interarticular isc. The inner portion is marked by two rough oblique grooves,
Fig. 195.—The Right Triquetral Bone (Anterior, Lateral, and Inferior Surfaces).
superior and posterior, separated by a ridge which is dorsally placed. The inferior surface presents a large triangular facet, concavo-convex from without inwards, for the hamate.
Articulations. — Superiorly with the triangular interarticular disc, inferiorly with the hamate, laterally with the lunate, and anteriorly with the pisiform.
The Pisiform Bone
The pisiform bone, as its name implies, is pea-shaped, and is placed in front of the triquetral, which constitutes its only articulation. It is an irregular sphere, except posteriorly , where it presents over its
upper three-fourths a circular, flat facet for the triquetral, the lower fourth being nonarticular. The long axis of the bone is directed downwards and slightly outwards. The palmar surface gives attachment superiorly to the flexor carpi ulnaris, inferiorly to the piso-hamate and piso-metacarpal ligaments, and abductor digiti minimi, and laterally to a portion of the flexor retinaculum. The medial surface is irreguf v larly convex, and has a narrow, rough groove
or a igament. The lateral presents the smooth, shallow ulnar groove. lodging the ulnar nerve.
Fig. 196.—The Right Pisiform Bone (Posterolateral View).
T-kf trapezium is the lateral bone of the second row, and is characenzed by a groove and ridge on its palmar surface, and a saddle-shaped facet on its inferior surface. It is polyhedral, and its long axis is directed
Fig. 197. — The Right Trapezium.
A, antero-inferior; B, supero-medial view.
mZI? ‘I 1 '/* 11 , 1 . war '^' The superior surface presents a semi-oval, 1 ‘ : "y or ie scaphoid. The inferior surface presents a saddle amfHi™ co " cav ® from Slde t0 side, convex from before backwards,
and directed outwards as well as downwards, for the base of the first metacarpal bone. The medial surface has two facets—an upper, which is large and concave, for the trapezoid, and a lower, which is small, for the base of the second metacarpal bone. The lateral surface is broad, pentagonal, and rough. The palmar surface, rough and elongated from above downwards and inwards, is broad above and narrow below. Superiorly it presents a deep groove, directed downwards and inwards, which transmits the tendon of the flexor carpi radialis, and lateral to this groove a prominent crest which gives attachment to the flexor retinaculum, abductor pollicis brevis, and opponens pollicis. The dorsal surface is broader than the palmar, and its inferior and medial angle is much elongated towards the base of the second metacarpal bone, with which it articulates by the small facet on its inner aspect.
Articulations. — Superiorly with the scaphoid, inferiorly with the first metacarpal, and medially chiefly with the trapezoid, but also with the second metacarpal.
The Trapezoid Bone
The trapezoid bone somewhat resembles the trapezium, but it is destitute of a groove and tuberosity. Its antero-posterior diameter is longer than the transverse. The palmar surface is small and pentagonal, and it gives origin to fibres of the oblique head of adductor pollicis.
Fig. 198.—The Right Trapezoid Bone. A, lateral view; B, posterior view.
The dorsal surface is large, and has its medial and inferior angle elongated towards the styloid process of the third metacarpal bone. Both of these surfaces are rough for ligaments. The superior surface presents a quadrilateral, concave facet, elongated from before backwards, for the scaphoid. The inferior surface is characterized by a large saddleshaped facet, convex from side to side and concave from before backwards, for the base of the second metacarpal bone. The lateral surface has a convex facet for the trapezium, below which there is a rough triangular surface with the base directed anteriorly. The medial surface is concave from before backwards, and its anterior portion presents a facet for the capitate.
Articulations. — Superiorly with the scaphoid, inferiorly with the second metacarpal, laterally with the trapezium, and medially with the capitate.
The Capitate Bone
The capitate is the largest bone of the carpus, its distinctive characters being that it is composed of a head, neck, and body. The superior and lateral aspects of the head are convex, and merge gradually into each other. The cartilage of the superior aspect is prolonged more behind than in front, and articulates with the lunate. The lateral aspect of the head articulates with the scaphoid. The medial aspect of the head is flat, and presents the commencement of the facet for the hamate bone. The neck is mainly present in front and behind.
The body is quadrilateral, and narrower in front than behind. The palmar and dorsal surfaces are rough, the former giving origin to fibres of the oblique head of adductor pollicis. The lateral surface , which is continuous with the outer convex aspect of the head, presents anteriorly a facet for the trapezoid. The medial surface presents at its back part the lower portion of the facet for the hamate, which is here narrow. The inferior surface is narrow in front, but broad behind, and the medial of the two posterior angles is elongated downwards and mwards. This surface presents three facets. The middle one is e largest, and articulates with the third metacarpal bone. The
Fig. 199. — The Right Os Magnum.
A, lateral view; B, medial view (the double unciform facet is abnormal).
TT. era 1S a narrow > concave strip for the second metacarpal bone.
le medial one, small and circular, tips inferiorly the projecting posteromedial angle, and articulates with the fourth metacarpal bone.
• + , Superiorly with the lunate, superiorly and laterally
yA1 , , e sca phoid, inferiorly with the second, third, and fourth metacarpal bones, laterally with the trapezoid, and medially with the hamate.
The Hamate Bone
nalrnnr ^one is characterized by a hook-like process on its
P Ur aC6 u trlan gcd ar > ° r wedge-shaped, and lies with its
for th^ 7 ™ ards - T1 ? e extremity presents a narrow facet
na e. he inferior surface is divided by an antero-posterior ridge into two quadrilateral facets, the outer of which articulates with the fourth, and the inner with the fifth, metacarpal bone. The palmar surface, which is rough, presents at its lower and inner part a prominent curved projection, called the hook. This process is laterally compressed, the lateral surface being concave and the medial convex, so that the direction of the curve is outwards. Its borders are superior, inferior, and anterior. The medial surface gives origin to the flexor, and opponens, digiti minimi, and close to the root the ulnar groove for the deep branch of the ulnar nerve may sometimes be seen. The anterior border gives attachment to the flexor retinaculum and the piso-hamate ligament. The dorsal surface is extensive and rough. The lateral surface presents an elongated facet, broad above and narrow below, where it is confined to the back part, for articulation with the capitate. The supero-medial surface is concavo-convex from below upwards, and articulates with the triquetral. The medial border, situated at the meeting of the supero-medial and inferior surfaces, is narrow and rough, its direction being from before backwards.
Fig. 200. — The Right Hamate Bone.
A, lateral view; B, supero-medial view; C, inferior view.
Articulations. — Superiorly with the lunate, supero-medially with the triquetral, inferiorly with the fourth and fifth metacarpal bones, and laterally with the capitate.
The carpus as a whole is narrower above than below. The dorsal aspect is irregularly convex, and the dorsal surfaces of the bones of the first row (exclusive of the pisiform) are narrow, but in the second row they are broad, this being reversed on the palmar aspect. It is to be noted that the posteromedial angles of the trapezium, trapezoid, and capitate are distinctly elongated. The palmar aspect is rendered concave by the tubercles of the scaphoid and trapezium laterally and the pisiform bone and hook of hamate medially. These projections give attachment to the flexor retinaculum, which with the palmar concavity forms a fibro-osseous canal for the passage of the flexor tendons and median nerve. The superior aspect , which is directed backwards as well as upwards, is convex, and articulates with the radius and triangular interarticular disc. The inferior or metacarpal aspect is somewhat undulating. The inferior surface of the first row is for the most part deeply concave, but laterally it is convex. The superior
surface of the second row is concavo-convex from without inwards, the concavity being formed by the trapezium and trapezoid, into which the scaphoid convexity above is received, whilst the convexity is formed by the capitate and hamate, and is received into the concavity above.
Structure.—The carpal bones are each composed of cancellated tissue, covered by a thin shell of compact bone.
Fig. 201. — Carpus of Sphenodon Lizard.
Fig. 202. — Scheme of a Generalized Carpus.
Varieties. — The number of carpal bones is sometimes increased to nine, which is brought about in one or other of the following ways: (a) The scaphoid, lunate, trapezium, or capitate may be divided into two parts; (b) the styloid process at the base of the third metacarpal, or the hook of the hamate, may remain an independent ossicle; or (c) there may be a persistent os centrale, situated on the dorsal aspect between the scaphoid, trapezoid, and capitate. It is said that fractured carpal bones seldom unite, but each piece develops an articular surface and resembles a separate bone.
Ossification. — The carpal bones are all cartilaginous at birth. Each ossifies from one centre in the following order, and at the following periods approximately :
Capitate, 1st year. Hamate, 2nd year. Triquetral, 3rd year. Lunate, 5th year.
Trapezium, 5th year. Scaphoid, 6th year. Trapezoid, 6th year. Pisiform, 10th year.
The most primitive or generalized carpus is a transcendental arrangement Uuch is not found in any living animal. The nearest approach to it is found n the Sphenodon lizard, which only lacks one bone of the complete series, the adiale marginale (see Fig. 201).
The accompanying diagram (Fig. 202) gives the generalized arrangement dth the names by which the bones are known in comparative morphology, n man the radiale marginale has fused with the radiale to form the tubercle if the scaphoid, and these two have then coalesced with the centrale radiale, o that the human scaphoid contains three morphological elements. The entrale ulnare joins the third distale to form the capitate, while the fourth and ifth distalia probably fuse to form the hamate.
The metacarpus supports the phalanges, and is composed of five ong bones, which are named numerically from without inwards, hat of the thumb being the first. Each bone is divisible into a shaft md two extremities, proximal and distal. The shaft is triangular,
xcept in the first, in which it is compressed from before backwards, it is longitudinally concave on the palmar aspect, and presents three urfaces, two lateral and a dorsal. The lateral surfaces give attachment
o interosseous muscles, and are separated from each other by an interior border. The dorsal surface over its proximal third presents 1 median ridge, which in the case of the fifth metacarpal is placed owards the inner side. Over the distal two-thirds the ridge dfurcates, its divisions passing each to the dorsal tubercle on the side of the head, and enclosing between them a flat triangular surface. The head or distal extremity, which articulates with a proximal phalanx, is convex, and covered by cartilage, except laterally. The cartilage is prolonged farther on the palmar than on the dorsal surface, md terminates anteriorly in a concave border, the extremities of yhich form small condyles. Laterally the head is compressed, and presents at either side a dorsal tubercle and palmar depression for
he collateral ligament of the metacarpo-phalangeal joint. The base or proximal extremity is irregularly quadrilateral, being Droader on its dorsal than palmar surface, and it articulates superiorly with the carpus, and at either side with its fellows, except in the case of the first.
The First Metacarpal Bone.—This is shorter than any of the others, md its shaft is compressed from before backwards. The palmar %spect } which has an inclination inwards, has the anterior border placed nearer the inner than the outer side. The outer margin and idjacent part of the palmar aspect give insertion to the opponens pollicis, and the inner margin over its proximal half gives origin to the outer head of the first dorsal interosseous. The dorsal surface 's slightly convex, and is destitute of the ridge which characterizes the others. The head is elongated transversely, and articulates on its palmar surface with two sesamoid bones. The base is transversely oval, and has a saddle-shaped articular surface for the trapezium, which is concave from before backwards, and convex froi side to side. Laterally it presents a tubercle for the insertion ( the abductor pollicis longus, and medially it gives origin to the fin palmar interosseous. The side to which the bone belongs may be told by the outer part of the saddleshaped facet being the larger.
Fig. 203. — The First Right Met.a carpal Bone (Palmar View).
Articulations. —Superiorly with the trapezium, and inferiorly with the first phalanx of the thumb, and the two sesamoid bones.
The Second Metacarpal Bone
This is the longest. Its base, which is the largest, has a V-shaped notch for the trapezoid, being concave from side to side. Medial to this, it rises into a prominent border, which presents a faceted strip for the capitate, and laterally at the back part there is a small facet for the trapezium. The inner side presents an antero-posterior facet, notched at the centre of its lower border, for the third metacarpal The palmar aspect gives insertion to the principal part of the tendon 0 the flexor carpi radialis, and origin to a portion of the oblique hea( of adductor pollicis. The dorsal aspect at its outer part gives insertioi to the extensor carpi radialis longus, and at its inner part to a smal slip of the extensor carpi radialis brevis, there being a notch betweei the two impressions. The shaft gives origin to the first and seconc dorsal, and second palmar, interossei.
Articulations. — Superiorly with the trapezium, trapezoid, anc capitate magnum, medially with the third metacarpal, and inferior /1 with the proximal phalanx of the index finger.
The Third Metacarpal Bone. — This is next in length to the second Its distinctive character is the styloid process at the base. Th( superior surface of the base articulates with the capitate. The oute] side presents an antero-posterior facet, notched at its lower border for the second metacarpal. The inner side presents two circular facets separated by a rough vertical groove, for the fourth metacarpal The palmar aspect gives insertion to a slip of the flexor carpi radialis and origin to a portion of the oblique head of adductor pollicis. The dorsal aspect laterally gives insertion to the principal part of the extensor carpi radialis brevis, and it is projected upwards at its outei angle into the styloid process. The anterior border of the shaft, ovei its distal two-thirds, gives origin to the transverse head of adductoi pollicis, and the shaft also affords origin to the second and thirc dorsal interossei.
Articulations. — Superiorly with the capitate and the second anc
Fig. 204. — The Second Right Metacarpal Bone.
A, medial view; B, lateral view.
Fig. 205. —The Third Right Metacarpal Bone.
A, medial view; B, lateral view.
Fig. 206.—The Fourth Right Metacarpal Bone. A, medial view; B, lateral view.
For 4th Metacarpal • Tubercle for Extensor
For Hamate Carpi Ulnaris
Iug. 207.—The Fifth Right Metacarpal Bone.
A, lateral view; B, dorsal view.
ourth metacarpal bones, and inferiorly with the proximal phalanx if the middle finger.
The Fourth Metacarpal Bone—This is shorter than the third, and ts base is small. The outer side of the base usually presents two drcular facets, separated by a rough vertical groove, for the third netacarpal, though quite often one of these facets is wanting. The inner side has a semi-oval facet for the fifth metacarpal. The superior surface presents two facets. One is large for the hamate, whilst the ither, situated at the outer and posterior part, is small for the capitate. The shaft gives origin to the third and fourth dorsal, and third palmar, interossei.
Articulations. Superiorly with the capitate, hamate, and third and fifth metacarpals, and inferiorly with the proximal phalanx of the ring finger.
The Fifth Metacarpal Bone. — This is shorter than the fourth, but longer than the first. The superior surface of the base presents a quadrilateral facet for the hamate. The outer side has an auricular facet for the fourth metacarpal, and the inner side presents a rounded tubercle for the insertion of the extensor carpi ulnaris. The inner margin of the shaft gives insertion to the opponens digiti minimi, and the shaft also affords origin to the fourth dorsal, and fourth palmar, interossei.
Articulations. — Superiorly with the hamate, laterally with the fourth metacarpal, and inferiorly with the proximal phalanx of the little finger.
Each metacarpal bone presents a nutrient foramen, that of the first, and usually that of the second, being situated on the inner or ulnar side of each shaft, whilst those of the third, fourth, and fifth are situated on the outer or radial side* The foramen of the first and the canal to which it leads are directed downwards towards the head, but those of the other four are directed upwards towards the base. The nutrient artery of the first metacarpal is furnished by the princeps pollicis artery, those of the second and third are branches of the first palmar metacarpal, that of the fourth is furnished by the second palmar metacarpal, and that of the fifth by the third palmar metacarpal arteries.
The metacarpus as a whole is concave from side to side, and also longitudinally, on its palmar aspect, whilst the dorsal aspect is convex. The first metacarpal stands off at an angle from its fellows, and occupies a more anterior plane, thus fitting it for the important movemen of opposition on the part of the thumb. The other four metacarpal lie very nearly parallel with each other. They articulate with on< another by their bases, but diverge slightly towards their heads, when they are connected on their palmar aspects by the transverse meta carpal ligament. Between the five bones there are four intervals called interosseous spaces , the first being that between the first an( second bones.
Of 100 second metacarpal bones examined, 59 had the nutrient foramen on the inner side, and 41 on the outer.
Fig. 208. — The Bases of the Right Metacarpal Bones (Superior View).
The phalanges are also known as ossa internodia , from their positioi between the joints of the fingers. The fingers, of which they forn the framework, are called pollex or thumb, index, middle, ring, am little, respectively. The number of phalanges is fourteen, three fo each of the four inner fingers, and two for the thumb. They an arranged in rows, both longitudinally and transversely, and the^ diminish in length from above downwards. They are distinguishes as proximal, intermediate, and distal, or ungual, except in the cas< of the thumb, where the second is wanting. It is inadvisable t<
speak of the rows as first, second, am third, as mistakes often arise in thi way.
The Proximal Phalanx.—The shaft i
compressed from before backwards, fla and concave longitudinally on the palma aspect, and convex on the dorsal. Tb palmar surface presents at either side ; rough border for the sheath of the flexo tendons. The proximal end or base i enlarged, and presents superiorly a con cave articular surface, transversely oval for the head of a metacarpal bone, am at either side a slight tubercular enlarge ment. The distal end is small, and pre sents a trochlear surface, grooved at tb centre and elevated at either side of thi into a small condyle, for articulation witl the middle phalanx, except in the case o the thumb, where it articulates with tb Proximal Extremity distal phalanx. The cartilage of the dista
Fig. 209. — The Phalanges of end is Prolonged more on the palm; the Middle Finger (Dorsal aspect than on the dorsal. At either sic View). it presents a depression for the collater
ligament of the interphalangeal joint. The Middle Phalanx. - 1 his is shorter and smaller than the proxima from which it is distinguished by having on its proximal end or bai two shallow articular depressions, separated by a median anter< pos erior nclge, for the distal end of the proximal phalanx. TI
distal end resembles that of a first phalanx, except that it is smaller. The shaft resembles that of a proximal. Its palmar surface presents at the centre of the lateral borders two rough impressions, one at either side, which give insertion to the divisions of a superficial flexor tendon. The dorsal surface of the base is marked by a rough transverse ridge for the insertion of the middle division of a common extensor tendon.
The Distal Phalanx. — This is of small size. The proximal end or base resembles that of a middle phalanx, and has in front a rough transverse ridge for the insertion of a deep flexor tendon, whilst the dorsal surface gives insertion to the two lateral divisions of a common extensor tendon. The distal end presents a rough, tapering, convex border, the roughness being continued for a little on the palmar aspect. This roughness, which is semilunar, is called the ungual process , and it supports the nail and the tissues forming the pulp of the finger.
The two phalanges of the thumb are of large size.
Special Muscular Attachments. —The base of the proximal phalanx of the thumb gives insertion laterally to the abductor pollicis brevis and the flexor pollicis brevis, medially to the first palmar interosseous, oblique and transverse heads of adductor pollicis, and posteriorly to the extensor pollicis brevis. The -base of the distal phalanx gives insertion anteriorly to the flexor pollicis longus, and posteriorly to the extensor pollicis longus. The base of the proximal phalanx of the index finger gives partial insertion to the first dorsal interosseous laterally, and the first palmar interosseous medially. The base of the proximal phalanx of the middle finger gives partial insertion to the second dorsal interosseous laterally, and the third dorsal interosseous medially. The base of the proximal phalanx of the ring finger gives partial insertion to the third palmar interosseous laterally, and the fourth dorsal interosseous medially. The base of the proximal phalanx of the little finger gives partial insertion to the fourth palmar interosseous laterally, and insertion to the abductor digiti minimi (partially) and flexor digiti minimi medially.
The nutrient foramen of each phalanx is situated on the palmar aspect of the shaft, not far from the distal end. It may be single, in which case it is mesially placed, or there may be two, one close to each lateral border. In all cases the direction of the foramen and the canal to which it leads is downwards towards the distal end. The nutrient arteries are furnished by the corresponding palmar digital arteries.
The Sesamoid Bones.—These are usually two in number, and are placed on the palmar aspect of the head of the first metacarpal bone. They are originally nodules of cartilage, one of which is developed in the tendon of insertion of the superficial head of the flexor pollicis brevis, and the other in that of the oblique head of adductor pollicis. Similar ossicles are sometimes met with on the palmar aspects of the heads of the second and fifth metacarpal bones, and are a reversion to the arrangement in the lower mammals, in which each digit has two sesamoid bones.
Ossification of the Metacarpal Bones and Phalanges. —Each of these bones ossifies in cartilage from one primary, and one secondary, centre.
The metacarpal bones begin to ossify about the ninth week, centres appearing in the middle of the shafts. At birth the heads are cartilaginous, epiphysial centres appearing here during the second to third year; in the thumb the epiphysis is at the proximal end, but an additional one at the distal end, ossifying later, is present in about 6 per cent, of cases. Occasional additional centres may be found for the proximal end of the index metacarpal and the styloid process of the third; this last may be present as a separate bone.
In girls the epiphysial ossification seems to appear somewhat earlier, and to fuse with the shaft about puberty; in the male fusion occurs about eighteen. This sexual difference applies also to the phalanges.
The phalanges ossify first, curiously enough, in the distal row, in the seventh to eighth week, the last phalanx of the thumb usually being the first bone in the hand to show an ossific centre. Centres for the first phalanges follow in about a fortnight, and for the second after a like interval. The proximal ends are cartilaginous at birth, and here epiphysial centres appear in the second year in the first row, and in the fifth in the others.
Fig. 210. — Ossification of the Bones of the Hand. A, 2nd metacarpal; B, ist metacarpal; C, ist phalanx.
It will now be obvious why, on p. 306, the statement was made that the nutrient artery nearly always runs towards the elbow,’ and that these phalanges and first metacarpal bones are exceptions. At the same time it will be seen that there is no exception to the xule that the nutrient artery always runs away from the growing end of a bone. A very little thought will show that this must be so.
The Hand as a Whole
The hand presents two surfaces, dorsal and palmar; two borders, °Ucei and inner; and two extremities, proximal and distal.
phe dorsal surface is convex, both longitudinally and transversely.
transversd mar 01 V °* ar sur * ace concave, both longitudinally and
rhe outer or radial border is in line with the thumb or pollex, thumb 0rme< ^ scaphoid, trapezium, and the phalanges of the
The inner or ulnar border is in line with the little finger, and is formed by the triquetral, hamate, and the phalanges of the little finger. This border has the tubercle on the inner side of the base of the fifth metacarpal bone for the tendon of the extensor carpi ulnaris. ^
Fig. 211.—The Right Hand (Palmar Surface).
The proximal extremity is formed by the scaphoid, lunate, and triquetral bones.
The distal extremity is formed by the distal phalanges.
It is to be noted (1) that the thumb is the shortest of all the digits; (2) that it stands off at an angle from its fellows; and (3) that it occupies a more anterior plane than its fellows, in which respects it presents a striking contrast to the great toe.
The palmar aspect of the carpus is rendered concave by the tuberch of the scaphoid and trapezium laterally, and the pisiform and the hoc of the hamate medially. These four projections give attachment 1 the flexor retinaculum. This ligament, along with the palmar coi cavity of the carpus, constructs a fibro-osseous passage, called tt anterior palmar canal, which transmits (i) the tendons of the flex(
Fig. 212. Ihe Right Hand (Dorsal Surface),
«Iv° ri !r sublimis and profundus, and the median nerve lyi
nnr1 arge inner compartment of the great palmar synovial shea
i j J , e en don of the flexor pollicis longus lying within the sm outer compartment of the sheath. *
^ scaphoid gives partial attachment to the fle? m, anc paitial origin to the abductor pollicis brevis muscli
The crest of the trapezium , which forms the outer lip of the groove, skives partial attachment to the flexor retinaculum, as well as to (i) the abductor pollicis brevis, (2) the opponens pollicis, and (3) the flexor pollicis brevis.
The groove on the palmar surface of the trapezium transmits the tendon of the flexor carpi radialis, which lies in a special compartment in the outer part of the flexor retinaculum, and is invested by a special synovial membrane.
The pisiform bone gives attachment to (1) part of the flexor retinaculum, (2) the tendon of the flexor carpi ulnaris, (3) the pisohamate and piso-metacarpal ligaments, and (4) the abductor digiti minimi muscle.
The hook of the hamate gives attachment anteriorly to part of the flexor retinaculum and the piso-hamate ligament, and medially partial origin to the flexor digiti minimi and opponens digiti minimi. The ulnar groove on the medial surface of the hook, close to its root, transmits the deep branch of the ulnar nerve.