Paper #3 - Comparison of cemented polyethylene peg and hybrid cage glenoids in total shoulder arthroplasty

Abstract

Introduction: Aseptic glenoid loosening remains a long-term complication of total shoulder arthroplasty (TSA). To improve long-term fixation and decrease the risk of aseptic loosening, glenoid components with hybrid fixation, consisting of a large metal ingrowth central peg and cemented peripheral pegs, have been developed. The purpose of this prospective study is to determine the clinical and radiographic outcomes of a hybrid cage glenoid component compared to an age and gender matched polyethylene (PE) peg glenoid component with a minimum tow year follow-up. Methods: Ninety-two patients with a mean age of 63 years were treated with a TSA for osteoarthritis by 7 surgeons using either a cemented pegged glenoid or a hybrid fixation cage glenoid. Forty-six patients who received a cage glenoid (19 female and 27 males) were matched for sex and age with 46 patients who received a peg glenoid, and all had a minimum 2 year follow-up. The patients were scored preoperatively and at latest follow-up using the SST, UCLA, ASES, Constant, and SPADI metrics; active abduction, forward flexion, and active and passive external rotation were also measured. The average follow-up for all patients was 26 months (cage 25 months; peg 26 months). A Student's two-tailed, unpaired t-test was used to identify differences in preoperative, postoperative, and pre-to-post-operative improvements in results, where P < .05 denoted a significant difference. IRB approval was obtained at each institution. Results: All patients demonstrated significant improvements in pain and function following TSA with a cage or peg glenoid (P < .0001). For the cage prosthesis, ASES scores improved from 37 to 89, Constant scores from 39 to 76 (P < .0001). Significant improvements were also seen in the SST, UCLA and SPADI scores (P < .001). For the peg glenoid, ASES scores improved from 35 to 84, Constant scores from 39 to 69 (P < .0001), and significant improvements were also seen in the SST, UCLA and SPADI scores (P < .0001). Active forward flexion for a cage glenoid improved from 104° to 149° and active external rotation from 22° to 49°. Active forward flexion for a peg prosthesis improved from 92° to 135° and active external rotation from 16° to 47° (all P < .0001). Cemented peg glenoids were noted to have significantly lower preoperative abduction measurements; however, no significant differences were observed in any postoperative clinical metric or motion measurement except for the SPADI score (P = .0497) and active forward flexion (P = .0427). Cage prostheses were associated with significantly less blood loss than a peg glenoid (mean blood loss, 242 cc vs 337 cc; P = .022). Radiolucent lines were noted in 14% of cage glenoid patients and 28% of peg patients. There were no cases of radiographic or clinical loosening, clinical failures or revisions in either cohort. There were 3 complications in the cage glenoid group and 4 complications in the peg patients. Discussion: Similar clinical outcomes were found at a minimum two years follow-up comparing a standard cemented peg glenoid with a hybrid cage glenoid prosthesis. The 50% reduction in radiolucent lines for the cage relative to the cemented peg glenoid is significant. This is a proof of concept study demonstrating statistically significant clinical improvements and a significant decrease in the incidence of radiolucent lines following implantation of a hybrid cage glenoid component. Additional and longer-term follow-up is needed to confirm these early outcomes.