Modern trunnion designs do not affect clinically significant patient-reported outcomes.

Abstract

Trunnion geometry is known to vary between hip systems. Trunnionosis and the impact of trunnion design on total hip arthroplasty (THA) survival, has gained attention as a failure mechanism. We sought to report the differences in patient-reported outcome measures (PROMs) between the most commonly utilised modern THA trunnions. We reviewed primary unilateral THA patients from May 2007 to October 2011. The most frequently used stems were included. LEAS, HOOS subdomains, and SF-12 were obtained pre and post operatively while satisfaction was measured at 2 years after THA. Trunnions were grouped by taper geometry and manufacturer. The 2-year change in PROMs for each trunnion was compared to the pooled 2-year change in HOOS for all other trunnions. 3950 THA patients were studied. 6 trunnion designs were evaluated from 5 manufacturers. The range in differences between the 2-year change in individual PROMs were as follows: HOOS pain (0.6-2.4), HOOS symptoms (0-3.8), HOOS ADL (0.4-4), and HOOS QOL (0.5-3.6). None of the differences in the 2-year change in PROMs reached a minimal clinically important change (MCIC), which we previously determined to be a minimum of 9 points for all HOOS domains. All of the trunnions designs utilised in our study cohort demonstrated excellent clinical results. Small differences were well below the known MCIC; and were not clinically relevant. The findings of this study should prompt further investigations into the long-term impact of trunnion design on clinical patient-reported outcomes.