THE METAL BACKED GLENOID COMPONENT IN TOTAL SHOULDER ARTHROPLASTY- MINIMUM 5 YEARS FOLLOW UP

Abstract

Purpose of the study: To assess the survivability of the metal backed glenoid component, to examine its mode of failure and to measure the range of movement, specifically rotation following Total Shoulder Arthroplasty.

Patients and methods: 46 patients (55 shoulders) were prospectively followed up after Biomet biomodular Total Shoulder Arthroplasty using a metal backed glenoid component fixed with screws. 36 patients (43 shoulders) had Rheumatoid arthritis, 9 patients (11 shoulders) had Osteoarthritis and 1 patient had Psoriatic arthritis. Mean age at surgery was 58 years (range 37 to 79 years). Patients were followed up for a minimum of 5 years. Data was collected prospectively for a mean follow up of 84 months. 28 of the 46 patients had more than 10 years follow up. Range of movement including forward flexion and rotation was measured. Data was analysed by 3 independent observers. Intention to treat or revision of component was taken as failure. Paired t test comparison was carried out for statistical analysis.

Results: One failure was noted in the Osteoarthritis group at 8 years follow up. Superior head migration and eccentric wear of polyethylene liner was noted in an otherwise well fixed glenoid component. Range of external rotation improved from a mean of 18.2 to 38.2 degrees. This improvement was statistically significant (p=0.01, 95% CI= 6.3 to 35.2). The range of forward flexion improved significantly from a mean of 80.5 to 110 degrees (p= .01, 95% CI= −42.6 to −5.9)

3 failures were noted in the Rheumatoid group. 2 patients needed revision to hemiarthroplasty within 4 years of surgery for rotator cuff insufficiency with superior head migration but without loosening of glenoid. One other shoulder was revised at 11 years for glenoid component loosening with a worn out polyethylene liner. All 3 failures occurred in patients more than 60 years of age. Rheumatoid patients under 60 had a significant improvement in the range of external rotation from a mean of 24.2 to 30.6 degrees (p= 0.03, 95% CI = −21.4 to −1.1). The range of forward flexion improved from a mean of 71.2 to 73.3 degrees which was not statistically significant (p=.767). Rheumatoid patients over 60 years of age did not have a statistically significant improvement in the range of external rotation( p= 0.712) or in their range of forward flexion (p=.757).

Conclusion: Contrary to recent literature, in this study the metal backed glenoid component performed well in the medium to long term following Total Shoulder Arthroplasty particularly in patients with Osteoarthritis and in younger patients suffering with Rheumatoid arthritis.