Total hip arthroplasty (THA) is a reliable operation, but it is critical that orthopaedic surgeons characterize which surgical factors influence patient-reported outcomes. The purpose of this study was to determine whether implant selection at the time of THA affects the odds of having (1) inadequate improvement according to patient-reported pain, function, and activity; (2) failure to achieve a substantial clinical benefit (SCB) with respect to pain; or (3) failure to achieve a patient-acceptable symptomatic state (PASS) according to pain and function.
Prospective data were collected from 4,716 patients who underwent primary THA (from July 2015 to August 2018) in a single health-care system with standardized care pathways. Patients were categorized according to the type of femoral and acetabular components and bearing surface used. Outcomes included 1-year postoperative patient-reported outcome measures (PROMs) and improvement in the Hip disability and Osteoarthritis Outcome Score (HOOS) and the University of California at Los Angeles (UCLA) activity score. Inadequate improvement was defined as PROMs that changed by less than the minimal clinically important difference (MCID) for the HOOS pain and physical function short form (PS) and as failure to improve beyond a mostly homebound activity status for the UCLA activity score (a score of ≤3). The MCID and SCB thresholds were set at values reported in the literature.
One-year PROM data were available for 3,519 patients (74.6%). There were no differences in the proportion of patients who attained the MCID in terms of HOOS pain, HOOS PS, or UCLA activity scores at 1 year for all analyzed implant parameters. Multivariate regression demonstrated that implant selection was not a significant driver of inadequate improvement, according to HOOS pain and HOOS PS (p > 0.05). Larger (36-mm) femoral heads demonstrated lower odds of inadequate improvement versus 28-mm femoral heads according to UCLA activity scores (odds ratio [OR]: 0.64; 95% confidence interval, 0.47 to 0.86; p = 0.003). Implant-related criteria were not significant drivers of attaining a PASS or achieving an SCB with respect to HOOS pain.
For the most part, THA implant characteristics are not drivers of inadequate improvement with respect to pain and function. Surgeons should utilize implants with an acceptable track record that allow stable fixation and restoration of hip biomechanics.
Level of Evidence:
Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.