Conversion Total Hip Arthroplasty Results in Delayed Patient Improvement Timelines Compared to Primary Total Hip Arthroplasty: Findings From a Propensity-Score Matched Analysis of Time to Achieve Minimal Clinically Important Difference in 698 Procedures.

Abstract

Previous studies have shown that conversion total hip arthroplasty (cTHA) is associated with worse clinical outcomes, increased complications, and higher costs than primary total hip arthroplasty (pTHA). An underinvestigated factor that may vary between cTHA and pTHA is patient postoperative clinical improvement timelines. This study compared the median time to achieve minimal clinically important difference (MCID) between cTHA and pTHA patients. We conducted a retrospective analysis comparing 175 cTHA and 523 propensity score-matched pTHA patients. Patient-reported outcomes were evaluated using preoperative and postoperative scores of Patient-Reported Outcomes Measurement Information System (PROMIS) Global Physical, PROMIS Physical Function-10a, and Hip disability and Osteoarthritis Outcome Score Physical Function Shortform. Time to achieve MCID was assessed using survival curves with and without interval-censoring, and statistical comparisons were performed using log-rank and weighted log-rank tests. Using interval censoring to more precisely determine the exact time to achieve MCID, cTHA patients had a statistically delayed time to MCID for the PROMIS Physical Function-10a (3.03 to 3.04 versus 1.63 to 1.63; P = 0.011) and PROMIS Global Physical (0.73 to 0.74 versus 0.67 to 0.67; P = 0.049) as compared to pTHA patients. Time to MCID for the Hip disability and Osteoarthritis Outcome Score Physical Function Shortform was similar between cohorts (1.43 to 1.44 versus 1.33 to 1.34; P = 0.40). Patients undergoing cTHA may have delayed improvement timelines as compared to pTHA. This finding is possibly related to the increased medical and surgical complexity of cTHA. Conversion total hip arthroplasty remains a safe and effective treatment choice to improve patient hip pain and function in many settings. Yet arthroplasty surgeons can counsel cTHA patients that it may take approximately 3 months for the median patient to experience clinically relevant improvement. The same improvement timeline may be experienced by the median pTHA patient in only 1.6 months.