SHOULDER JOINT (NORMAL ANATOMY). 



tern consequent on the administration of 

 mercury. Neither must the influence of at- 

 mospheric pressure be forgotten, which, ex- 

 erting as it does a force of nearly fifteen 

 pounds on the square inch, must powerfully 

 contribute to preserve the contact of the 

 articular surfaces. 



Within the capsular ligament, and at the 

 upper and outer part of the joint, two struc- 

 tures are found, which may, with propriety, 

 be described as inter-articular ligaments; these 

 are the tendon of the long head of the biceps, 

 and the gleno-humeral, or I^lood's ligament. 



The long tendon of the biceps has been de- 

 scribed already, as attached to the apex of the 

 glenoid cavity, and to the fibrous portion of 

 its circumferential fibro-cartilage. Surrounded 

 by synovial membrane, it passes downwards 

 and outwards, forming an arch over the head 

 of the humerus, it then descends in the bi- 

 cipital groove, where it is retained in situ by 

 the fibres of the capsular, and of the accessory 

 (coraco-hnmerafy ligaments. 



Cruveilhier mentions that in two cases he 

 found this tendon united by a strong adhesion 

 to its groove, " thus justifying the name of 

 ' inter-articular ligament:' the tendon for the 

 long head of the biceps took its origin from 

 the same groove." This condition, Cruveil- 

 hier supposes to have been the result of in- 

 jury ; but as the appearance in question has 

 been seen by the writer, as the result of 

 chronic rheumatism, affecting the scapulo- 

 humeral articulation, he is compelled, although 

 reluctantly, to dissent from such high autho- 

 rity, and to express his opinion that this 

 change originated in rheumatism, not in ac- 

 cident; his opinion is farther borne out by 

 the state of the inter-articular portion of the 

 tendon in Cruveilhier's cases, for it is stated, 

 that " the bicipital groove was depressed, and 

 the inter-articular ligament flattened, and, as 

 it were, lacerated." 



The inter-articular portion of the tendon of 

 the biceps, by itself, could scarcely protect 

 the head of the humerus from displacement 

 upwards, a use very commonly assigned to it, 

 as the smooth convex head of the bone 

 would readily slip from beneath it ; but in the 

 interior of the joint, a second band, the 

 " gleno-humeral ligament," described by the 

 late Dr. V. Flood, is thrown across the head 

 of the humerus, and may contribute to oppose 

 this luxation ; we quote the following de- 

 scription of this ligament from Dr. Flood : 

 " It may be easily exposed," he says, " by cut- 

 ting through the inferior part of the capsule 

 transversely, and throwing back the arm over 

 the head, you thus expose the interior of the 

 upper part of the capsule, also the biceps 

 tendon. Parallel to the inner edge of the 

 latter, this ligament may be felt and exposed 

 b) a little dissection. The tendon of the sub- 

 scapularis in passing to its insertion, rests in 

 a notch in the superior and internal part of 

 the edge of the cavity ; from the edges of 

 this notch, the ligament arises broad and flat, 

 then proceeds along the internal edge of the 

 biceps tendon, and becoming smaller and 



575 



rounder, is inserted into a distinct pit in the 

 anatomical neck of the humerus, at the inner 

 edge of the bicipital groove. In its triangular 

 form, its origin at a notch in the articular 

 fossa, and its insertion into a pit, it strongly 

 resembles the ' ligamentum teres ' of the hip- 

 joint."* 



In nearly all the specimens examined by the 

 writer, the upper half of this ligament had 

 both its surfaces invested by the synovial 

 membrane. This enables the dissector readily 

 to distinguish it from the capsule; but in- 

 feriorly, its fibres are generally identified with 

 this structure, and therefore it loses the ap- 

 pearance of a distinct ligament, before ar- 

 riving at the humerus. 



With the mode of its origin, and its intra- 

 capsular position, all resemblance between 

 this structure and the " ligamentum teres " 

 in the hip-joint, ceases ; the latter has little 

 of the structure, and fulfils none of the uses 

 of a ligament. Not so the " gleno-humeral liga- 

 ment:" its structure is distinctly fibrous, it 

 possesses great powers of resistance, and it is 

 an auxiliary to the tendon of the biceps, so 

 that both together are enabled to restrain the 

 undue ascent of the humerus ; an object which 

 it seems probable neither of them could ac- 

 complish, unaided by the other. 



Synovial membrane. In its arrangement 

 and general characters, the synovial membrane 

 of the shoulder joint differs in no way from 

 that of other articulations. As the fibrous 

 capsule is lax, so the serous membrane, which 

 lines it, presents a cavity of large size. Hav- 

 ing covered the articular cartilage of the head, 

 it passes downwards on the neck and tubero- 

 sities of the humerus, as far as the lower 

 attachment of the capsule, to the inner surface 

 of which it is thence reflected : having lined 

 the capsule, the synovial membrane arrives at 

 the glenoid cavity, the articular surface of 

 which it similarly invests ; it forms sheaths 

 for the inter-articular ligaments, for the long 

 tendon of the biceps, and for the gleno- 

 humeral ligament : that for the former, as has 

 been already described, extends along the 

 bicipital groove, even beyond the limits of the 

 capsule. Internally, where the capsule is 

 deficient, the synovial membrane covers the 

 corresponding portion of the tendon of the 

 subscapularis, and here a communication is 

 established between the cavity of the serous 

 membrane of the articulation and that of the 

 bursa mucosa, which is found beneath that 

 muscle. A similar communication sometimes 

 exists posteriorly between the cavity of the 

 joint and the bursa, which is subjacent to the 

 infra-spinatus muscle. A few fatty folds are 

 generally found attached to the reflections of 

 the membrane. 



In connection with the scapulo-humeral 

 articulation, the remarkable vaulted arch 

 placed above it remains to be described. This 

 is constituted by the acromion and coracoid 

 processes, and the intermediate ligament. It 

 may be regarded as supplemental to the 



* Lancet, 1829-30, p. 672. 



