HUMERAL PROBLEMS IN REVERSE SHOULDER ARTHROPLASTY

Abstract

The purpose of this study is to catalogue humeral problems with reverse total shoulder arthroplasty and define their influence on outcome.

A multicenter retrospective review of 399 reverse humeral arthroplasties implanted between January 1994 and April 2003, yielded seventy-nine patients with humeral problems. We define a clinical humeral problem as an event that alters the expected rehab or postoperative course. Perioperative problems are fractures within the stem zone while postoperative problems involve fractures distal to the stem, prosthetic disassembly and subsidence. Radiologic problems include humeral loosening and radiolucencies of greater than 2 mm that have not had a clinical impact. All radiographs were available and reviewed by three orthopaedic surgeons. Objective results were rated according to the Constant score; active forward flexion and external rotation were recorded; and subjective outcome was noted.

We identified twenty-six intra-operative fractures and eleven postoperative fractures. There were four cases of disassembly, three cases of subsidence, and fifteen cases of radiographic loosening. At a mean follow-up of forty-seven months, average active elevation was 111.3 degrees, external rotation was 7.0 degrees, and absolute Constant score improved from 21.9 to 50.1 points. Seventy-one percent of the patients were satisfied or very satisfied. Intra-operative humeral fractures were associated with poor final Constant score (42.3), poor range of motion and increased shoulder pain (p=0.001 for all items). Constant score for those revision patients who experienced a fracture was lower by 9.6 points (p=0.0347) than those patients who underwent a reverse prosthesis for revision surgery without a fracture. Constant score for those patients with a postoperative fracture averaged 47.2 (range, 8–70). A re-operation was performed in seven of the cases (9%).

Intra-operative humeral fractures occur commonly when a reverse prosthesis is indicated for revision; humerotomy is not protective, however, and is not recommended for all humeral revisions. Fractures, either intraoperative or post-operative, result in lower Constant scores. Any patient who received an intervention for a humeral problem yielded a lower constant score. While postoperative Constant scores improved in all categories, they were lower than those patients who did not sustain a humeral complication.