Although we have as yet said but little of any displacement of the head of the humerus occurring as a consequence of this chronic rheumatic disease, except in the di rection upwards, and upwards and inwards, yet we would now call attention to facts to prove that the head of the humerus, un. der the influence of the changes induced by this disease in the structures of the shoulder joint, may stiffer a partial displacement di rectly inwards under the coracoid process ; partially downwards, enlarging the axillary margin of the scapula, so as to form a new glenoid cavity ; and lastly, that the infi.a-spi natus fossa of the dorsum of the scapula may become the new situation, to which the head of the humerus niay be transferred from the effects of chronic rheumatic arthritis of the shoulder.
The wr;ter has after much investigation seen but two examples of this last displace ment, and, curious to observe, these were m the right and left shoulder joint of the same individual.
Partial dislocation of the head of the hunterus inwards.— In the museum of the College of Surgeons, Dublin, we find a specimen pre sented by Professor Hargrave, which he con siders one of partial luzation inwards front accident. The accidental origin of the af fection, however, cannot be proved, as the history of the case is unknown ; and the spe cimen presents so many of the features of the chronic rheumatic disease combined with the partial luxation, that we are of opinion that Professor Hargrave's specimen cannot be considered the result of accident ; but that all the appearances it presents are the conse quence of long established chronic rheu matic arthritis. We shall here give an ab stract of Dr. Hargrave's case, referring for a fuller account to the Edinburgh Medical Journal.
The capsular ligament presented a perfect state of integrity along the superior and pos terior part of the joint. It was very dense and strong, extending from the acromion process downwards and forwards towards thehumerus. When the capsule was opened on its internal aspect, the head of the humerus was seen to be in part external to the joint, and was di vided into two unequal portions by a deep groove extending for the entire length of its head in a perpendicular direction. Of these two portions the internal and larger one passed a small distance beyond the corre sponding edge of the glenoid cavity into the subscapular fossa, while the posterior and smaller one remained in the glenoid cavity, occupying its internal surface.
The groove now mentioned fitted on the inner edge of the glenoid cavity, which did not present its usual well defined border, but was rounded off, so as to present a thick lip, from the constant pressure and frequent mo tion of the humerus upon it. The bead of the humerus in its superior aspect was in close apposition with the coracoid process, and had altered in a remarkable degree its form, which in place of being beaked and point ed, was much expanded,flattened and slightly hollowed.
- When the articulation was first opened, the tendon of the long head of the biceps could not be seen ; but on more particular examina lion it was found to have been ruptured, the portion connected with the muscle being in timately attached to the bicipital groove of the humerus, while the portion belonging to the gleam(' cavity was much diminished in size, and presented a mere rudimental character in the capsular cavity.* When we carefully observe this specimen, we notice that it presents many of the general anatomical characters of the chronic rheumatic arthritis, these appearances being of course modified, as to the external shape of the sur faces, by the special peculiarity of the partial displacement which had in this case occurred.
The head of the humerus was much en larged and mis-shapen. It was found that a large portion of the new articular cavity for the head of the 'lanterns lay on the sub scapular fossa, but that a portion of the old glenoid cavity remained, and that the head of the humerus, divided into two surfaces, arti culated with both the new and old glenoid cavity. The effects of friction during the movements which took place between the bifid head of the humerus and the double articular cavity, which corresponded to it, were such that perfect and complete ebur nisation of parts of the contiguous surfaces took place. This last circumstance could not be said to amount to proof, that chronic disease rather than accident had caused the partial luxation. In addition to the ivory-hke enamel, we find also that bony vegetations, or granular nodules of new bone, surround the out line of the new articular surface formed for the head of the humerus; and that stnall foreign bodies, like sesamoid bones, are seen bordering the edge of the articular cavity posteriorly. All these minor circumstances remind us of the anatomical characters we have found in examining cases of chronic rheumatic arthritis of the shoulder. The coracoid process, we are informed, had altered in a remarkable degree its form, which had become expanded, flattened, and slightly hollowed; itr a word, it became articular, as we have often before found it to be, as the result of chronic rheu matic arthritis. The glenoid ligament (Pro fessor Hargrave's case) was absent ; and the following description, which we may be ex cused for recopying, may well be applied, we think, to the ordinary condition of the tendon of the biceps in most of the cases of chro nic rheumatic arthritis of the shoulder.