Osteoarthritis Of The Glenohumeral Joint
Osteoarthritis of the shoulder is considered a degenerative condition of the articular cartilage. It may be associated with inflammatory changes of the joint, but the damage to the cartilage is not primarily based on an inflammatory pathologic process as it is for rheumatoid arthritis. The rotator cuff tendons are almost always intact in patients with osteoarthritis, and there is a proliferative osteophyte formation around the periphery of the humeral head, making it much larger than normal. The joint enlargement and flattening of the humeral head results in loss of motion. There is loss of the uniformly white articular cartilage on the surface of the humeral head, and there is proliferation of bone (osteo- phyte) along the periphery of the humeral head. The head becomes flattened and larger, sometimes resembling a mushroom. In most cases of osteoarthritis, the humeral head is well centered within the center of the glenoid in anteroposterior radiographs. This is defined as the center of the humeral head being close to the midline of the center of the glenoid. Another method of assessing this alignment is a smooth and continuous scapulohumeral line at the inferior part of the humeral neck (Maloney line). This is a result of an intact rotator cuff. A continuous Maloney line is not seen when the rotator cuff is damaged, as seen on the anteroposterior radiographs in rotator cuff tear arthropathy (see Plates 1-49 and 1-50. With large and massive rotator cuff years there is superior migration of the humeral head with narrowing of the subacromial space. In some cases of more advanced osteoarthritis there is posterior glenoid bone loss associated with posterior translation in the humeral head that is best seen on an axillary radiograph or on an axial CT scan. The more advanced pathologic changes are more difficult to correct with joint replacement.
The clinical findings of advanced osteoarthritis are significant loss of passive (stiffness) and active (pain-related) glenohumeral motion. Significant pain in the shoulder is typically along the anterior and post- erior joint line with deep palpation. Advanced-stage osteoarthritis is often treated by total shoulder arthroplasty. Total-shoulder arthroplasty involves osteotomy (removal) of the humeral head at the anatomic neck (see Plates 1-1 and 1-45) and insertion of a stem down the medullary canal to which is attached an anatomically sized and positioned prosthetic humeral head. In addition, there is the preparation of the glenoid bone surface to correct pathologic version and insertion of a plastic glenoid component. After total shoulder arthroplasty with an intact rotator cuff without severe glenoid bone loss, there is restoration of the normal anatomic relationships between the humeral head center and glenoid center line on both the anteroposterior and axillary radiographs.
Nonoperative treatment for early and midstage arthritis would include modification activities, oral anti-inflammatory medication, and, occasionally, corticosteroid injection (see Plate 1-54). Viscosupplementation with high-molecular-weight hyaluronic acid (see Plate 1-54) injected into the joint over a series of three to five injections spaced 1 week apart has been used as an effec- tive nonoperative treatment for knee and shoulder osteoarthritis.