A MULTICENTRE, RANDOMIZED, CONTROLLED TRIAL COMPARING A SECOND-GENERATION UNCEMENTED TRABECULAR METAL-BACKED WITH A CEMENTED POLYETHYLENE GLENOID COMPONENT IN TOTAL SHOULDER ARTHROPLASTY: FIVE-YEAR RESULTS

Previously, we reported early findings (two-year) from a randomized controlled trial comparing a second-generation uncemented trabecular metal (TM) glenoid versus cemented polyethylene glenoid (POLY) in patients undergoing a total shoulder arthroplasty (TSA). The purpose of the current study is to report medium-term (five-year) results from this trial. Approval to conduct this multi-centre randomized trial was obtained from the appropriate institutional ethics boards. Five fellowship-trained surgeons from three centres participated. Patients 18–79 years with a primary diagnosis of glenohumeral osteoarthritis were screened for eligibility. Ineligibility criteria included: significant glenoid bone loss; major joint trauma; avascular necrosis; chronic dislocation; rotator cuff or inflammatory arthropathy; massive rotator cuff tear; previous shoulder surgery; muscle paralysis; Charcot arthropathy; life expectancy <two-years; or inability to read/speak English. Randomization to an uncemented TM or cemented POLY glenoid was performed intra-operatively after adequate bone stock was confirmed. Study intervals were baseline, two- and five-years postoperative. The primary outcome was the Western Ontario Osteoarthritis Shoulder (WOOS) score. Secondary outcomes included the American Shoulder and Elbow Surgeons score EQ5D, SF-12, clinical and radiographic exams. Radiographic images were reviewed for metal debris according to Endrizzi. Sample size was minimum 34 patients per group based on a minimal clinically important difference of 15 points on the WOOS. An additional 14 patients per group were recruited to account for attrition. Mixed effects repeated measures ANOVA for within and between group comparisons were performed. Of the 104 patients consented, 93 were randomized (46 TM; 47 POLY). There were no group differences at baseline (TM: 66.5yo (SD6.4); 24M/22F and POLY: 68.4yo (SD5.5); 23M/24F). No significant or clinically important differences were found with patient-reported outcomes, range of motion, or strength between groups at five-years postoperative. All outcomes in both groups improved significantly from baseline however, only minor improvements were observed between two- and five-years. With respect to the primary outcome (WOOS), the mean (SD) scores at baseline, two- and five-years were: TM: 32 (21), 92 (13), 93 (11) and POLY: 27 (15), 93 (11) and 93 (10), respectively. Metal debris was observed in 11 (23.9%) patients, but outcomes were not negatively impacted. Debris severity was minor (Grade 1 = 9pts; Grade 2 = 2pts) and remained stable in all but one patient who progressed from Grade 1 (years two-four) to Grade 2 in year five. Seven patients in each group experienced a complication. Of these, 6 (13%) in the TM and 4 (8.5%) in the POLY required a re-operation or revision. Only one patient experienced a glenoid-related complication requiring revision; this patient was in the TM group and had glenoid loosening due to infection. No catastrophic glenoid implant failures were observed. At five-years postoperative, there were no statistically or clinically significant differences between the two implants with respect to patient-reported outcomes, shoulder function, and complication rates. There were no catastrophic failures of the second-generation TM glenoid component. Metal debris was observed in 23.9% of patients with a TM glenoid but did not negatively influence implant survival, patient-reported outcomes, or shoulder function.