Modular total shoulder replacement. Design rationale, indications, and results.

Modular total shoulder systems offer many advantages over nonmodular designs. Modularity facilitates precise placement of the humeral head with respect to the rotator cuff and tuberosities, allows for soft tissue tensioning and balance with variable neck lengths, and simplifies revision surgery by allowing removal of the humeral head while maintaining a well-fixed humeral stem. This review includes 47 total shoulder arthroplasties performed in 40 patients from 1986 to 1991. The average patient age was 62.3 years, with followup averaging 54 months. Seventeen patients had rheumatoid arthritis, and 22 had osteoarthritis. In the remaining 8 patients, 5 had posttraumatic arthritis, 2 had avascular necrosis, and 1 had cuff tear arthropathy. Glenoid revision was required in 3 patients, and symptomatic loosening occurred in only 1. Pain relief was achieved in 93.5% of patients. Range of motion improved 34.9 degrees in forward flexion, 18.1 degrees in external rotation, and 4 vertebral levels of internal rotation. Lucent lines were evaluated on the anteroposterior (AP) and axillary radiographs. On the AP radiograph, 16 shoulders demonstrated lucency about the glenoid component. Progression beyond 2 mm occurred in 5 shoulders, and symptoms requiring revision developed in one patient. Twenty-two patients demonstrated a lucency on the axillary radiograph, and 9 patients progressed beyond 2 mm. None required revision. The authors present the results and discuss surgical and design considerations of modular total shoulder arthroplasty.