Patient Reported Outcomes After Conversion vs. Primary Total Hip Arthroplasty: A Propensity Matched Analysis.

Background: Conversion total hip arthroplasty (cTHA) is increasingly utilized as a salvage procedure for complications associated with fracture fixation around the hip and acetabulum and for failed hip preservation surgery. While primary THA (pTHA) has a high success rate, little is known about outcomes following conversion THA. The purpose of this study is to evaluate patient reported outcomes (PROs) and complication rates following conversion THA compared to primary THA.

Methods: Patients that underwent cTHA or pTHA from 2015-2020 at a large tertiary referral academic center were retrospectively identified. THA patients were propensity matched in a 1:1 fashion by age, body mass index (BMI), and sex. Pain scores and PROMIS physical function (PF), pain interference (PI), and depression (DA) scores were compared at preoperative and final postoperative follow up timepoints using independent t-tests. Differences in complication and reoperation rates between cohorts were assessed using chi square analysis.

Results: A total of 118 THAs (59 cTHA, 59 pTHA) were included in this analysis with an average follow up of 21.3 months. cTHAs were most commonly performed following hip fracture fixation (50.8%). The conversion cohort had significantly longer lengths of stay (3.6 days vs 1.9 days, p<0.01) and greater use of revision-type implants (39.0% vs 0.0%, p<0.01) compared to pTHA. There was no significant difference in complication rates (cTHA = 15.3%, pTHA = 8.5%; p=0.26), with intraoperative fracture being the most common for both. Primary and conversion THA groups also experienced similar reoperation rates (cTHA = 5.1%, pTHA = 6.8%; p=0.70). No significant differences in PROs at final follow up were identified between groups.

Conclusion: Patients undergoing cTHA required increased utilization of revision hip implants and had longer lengths of stay, but had comparable complication and reoperation rates, and ultimately demonstrated similar improvements in PROMIS scores compared to a matched cohort of pTHA patients. Level of Evidence: III.