UW Shoulder and Elbow Academy: Shoulder joint replacement

Degenerative Joint Disease

In degenerative joint diseases, the glenoid face is typically flattened and often eroded posteriorly as a result of chronic posterior subluxation. The glenoid may be distorted by peripheral osteophytes masking the location of the anatomic fossa. The humeral head may be flattened in a corresponding manner and effectively enlarged by the proliferation of goat’s beard osteophytes from the anterior, inferior, and posterior articular rim

Intra-articular loose bodies may lie hidden in the subcoracoid or axillary recess. Anterior capsular and subscapularis contractures are common in degenerative joint disease and require release; however, posterior capsular release is not performed if posterior humeral subluxation is noted preoperatively.

Rheumatoid Arthritis

The basic principles of shoulder arthroplasty for rheumatoid arthritis are similar to those for degenerative arthritis, but some important differences exist. Rheumatoid tissue is much more fragile: The bone is more likely to fracture, and the muscle and tendons are more susceptible to tear. Thus, from the outset, extreme care must be taken to preserve bone and soft tissue integrity. We refer to these requirements for extraordinary gentleness as the rheumatoid rules; they guide each step of our management of the patient.

Because rheumatoid arthritis is an erosive and destructive disease, deficiencies of bone and the rotator cuff are more likely to occur than in degenerative joint disease. The glenoid bone may be so eroded that insufficient stock is available to support a glenoid component. The rotator cuff may be partially or totally deficient. The shoulder may be so limited in volume that it will accept only a thin humeral component and no glenoid component. Thus, in the preoperative evaluation and in discussion with the patient concerning the possible outcomes of surgery, all these factors need to be considered.

The standard preoperative scapular AP and axillary radiographs are required to evaluate the humeral and glenoid bone stock. In rheumatoid arthritis, the glenoid erosion is usually medial (rather than posterior, as in degenerative joint disease). For this reason, only minimal glenoid reaming by hand may be necessary to achieve an excellent-quality fit to the back of the glenoid component. The potential fragility of the bone and soft tissues makes it particularly important that the joint not be overstuffed and that adequate soft tissue laxity be present for immediate postoperative motion. This is a particular challenge in diminutive patients with juvenile rheumatoid arthritis; such patients might also have a tiny humeral medullary canal. In addition, some patients have insufficient joint volume to permit the insertion of a glenoid component despite complete soft tissue release.

Secondary Degenerative Joint Disease

In post-traumatic arthritis, the challenges may be even greater. The anatomy is likely to be distorted by previous fracture or surgery. The nonarticular humeroscapular motion interface is likely to be scarred, with important neurologic structures such as the axillary nerve being obscured. The tuberosities, the humeral shaft, and the glenoid may be un-united or malunited. Each case requires consideration of the complexities of the shoulder and the needs of the patient

Capsulorrhaphy Arthropathy

Shoulders affected by capsulorrhaphy arthropathy present additional challenges, such as neurovascular scarring from previous surgery, soft tissue contractures, bone deficiencies, implants from previous surgery, changes in glenoid version, and an increased potential for glenohumeral instability after the arthroplasty. Patients with capsulorrhaphy arthropathy are typically younger than those with primary degenerative or inflammatory arthritis conditions; they also tend to desire a higher level of activity after shoulder arthroplasty. Careful assessment of the preoperative axillary x-ray can alert the surgeon to the excessive posterior capsular laxity that results from chronic posterior humeral subluxation after anterior stabilization procedures. Such laxity can predispose the reconstructed shoulder to posterior instability. Thorough release of the subscapularis tendon is necessary to prevent obligate posterior translation from residual tight anterior structures. If unmanaged, this posterior instability can lead to posterior wear and loosening of a polyethylene glenoid component should a total shoulder be performed.

Cuff Tear Arthropathy

Cuff tear arthropathy presents several unique challenges for regaining glenohumeral comfort and function. The humeral head may be in a superior position so that it articulates with the coracoacromial arch or that it may escape the arch altogether. The rotator cuff is almost never amenable to a repair, and the glenoid is eroded superiorly so that an acetabular-like structure is formed in continuity with the coracoacromial arch. Under these circumstances, a standard anatomic arthroplasty is unlikely to be successful.

If the coracoacromial arch is intact and if the shoulder is capable of 90 degrees or more of active elevation, the shoulder with cuff tear arthropathy can often be reconstructed with a hemiarthroplasty designed to provide a smooth articulation between the proximal humerus on one side and the coracoacromial arch and glenoid on the other. In this situation we prefer a special humeral prosthesis with an articular surface that extends over the area of the greater tuberosity with a curvature that matches that of the resected head.

This type of prosthesis may also be useful in managing post traumatic deformity

When there is anterosuperior instability from acromial erosion or a prior acromioplasty or when there is inability to actively raise the arm above 90 degrees in spite of good passive motion, a reverse total shoulder arthroplasty may be considered.