In a forward luxation of this kind, the operator should further flex the humerus, and while it is in this flexed position, force is exerted upon the articular head of this bone, and it is pushed downward and backward into its normal position.
After-care consists in restriction of exercise and, if necessary, confining the subject in a sling and the application of a vesicant over the scapulohumeral region.
Anatomy.—There is interposed between the tendon of the biceps brachii (flexor brachii) and the intertubercular or bicipital groove a heavy cartilaginous pad, which is a part of the bursa of the biceps brachii. This synovial bursa forms a smooth groove through which the biceps brachii glides in the anterior scapulohumeral region. Great strain is put upon these parts because the biceps brachii is the chief inhibiting structure of the scapulohumeral articulation—the one which prevents further flexion of the humerus during weight bearing. Passing, as it does, over two articulations, the biceps brachii has a somewhat complicated function, being a flexor of the radius and an extensor of the humerus. Thus it is seen, the biceps brachii is a weight bearing structure, as well as one that has to do with swinging the leg.
Etiology and Occurrence.—Because of the exposed position of the bicipital bursa (bursa-intertubercularis) it is occasionally injured. Blows and injuries received in runaway accidents do serious injury to the bursa and because of the peculiar and important part it plays during locomotion, serious injuries are not likely to resolve, and too often chronic lameness results. It is to be noted that the tendon of the biceps brachii (flexor brachii) is always involved in cases of inflammation of the bicipital bursa, and according to the late Dr. Bell strain of the biceps brachii is a frequent cause of lameness in city horses, more frequent than is generally supposed.
Pathological Anatomy.—More or less destruction of the cartilaginous portion of the bursa, sometimes involving the tendinous portion of the biceps, takes place and, according to Moller, in some instances there occurs ossification of the tendon. Autopsies in some old horses reveal the presence of erosions of cartilage and hyperthrophy of the inflamed parts.
Symptoms.—In acute inflammations, there is always marked lameness. This is manifested to a greater degree when the subject advances the affected leg. There is incomplete advancement of the member; the toe is dragged when the horse is made to walk and the foot kept in a position posterior to the opposite or weight bearing foot while the subject is at rest. Lameness is disproportionate to the amount of local manifestation in the way of heat, swelling and pain that is to be recognized on palpation. In fact, in some cases so much pain attends the condition that no weight is borne by the affected member, and when compelled to walk, the subject hops on the sound leg.