Results of anatomic nonconstrained prosthesis in primary osteoarthritis with biconcave glenoid.

BACKGROUND:
Biconcave glenoids in primary osteoarthritis represent a challenge because of the associated static posterior instability of the humeral head and secondary posterior glenoid erosion. This study evaluated the influence of different preoperative radiographic measurements on the outcome of total shoulder arthroplasty (TSA), particularly regarding the development of complications.

MATERIALS AND METHODS:
We retrospectively evaluated 92 anatomic TSAs performed in 75 patients with primary osteoarthritis and a biconcave glenoid. All patients underwent preoperative imaging with an axial computed tomography arthrogram. Measurements were taken for posterior bone erosion depth and ratio as well as humeral head subluxation. Clinical outcomes were evaluated with the Constant score.

RESULTS:
At an average follow up of 77 months (range, 14-180 months), 15 revisions (16.3%) were performed for glenoid loosening (6.5%), posterior instability (5.5%), or soft tissue problems (4.3%). At the final follow-up, the mean Constant score improved significantly from 32.4 to 68.8 points (P = .0001). Subjectively, 66.3% of patients were very satisfied or satisfied. Glenoid loosening was observed in 20.6% and was significantly associated with posterior bone erosion in depth (P = .005) and wear ratio (P = .02), humeral head subluxation (P = .01), and neoglenoid (P = .002) and intermediate glenoid retroversion (P = .001). Dislocation was correlated only with neoglenoid retroversion (P = .01).

CONCLUSIONS:
Performing TSA in patients with osteoarthritis and biconcave glenoids resulted in acceptable clinical outcomes but a very high rate of complications. We found that the preoperative measurement of the neoglenoid retroversion was best for predicting postoperative complications in terms of glenoid loosening and dislocation.