Conversion Total Hip Arthroplasty Following Prior Internal Fixation: A Comparison with Primary and Revision Total Hip Arthroplasty.

BACKGROUND: With rising life expectancy, the incidence of total hip arthroplasty (THA) following prior femoral and/or acetabular fracture fixation is increasing. Conversion THA (cTHA) following these procedures is technically complex and associated with unique challenges. However, direct comparisons between primary (pTHA), conversion (cTHA), and revision (rTHA) THA remain limited.

METHODS: This was a retrospective cohort study comparing intraoperative and postoperative outcomes among patients undergoing cTHA from April 2012 to October 2022. This was defined as THA following previous fixation with hardware present in the femur or acetabulum, including previous acetabular open reduction internal fixation (ORIF), femoral intramedullary nail, sliding hip screw, or blade plate. After propensity score-matching to pTHA and rTHA, each group included 148 patients. Outcomes were analyzed using odds ratios and hazard ratios with 95% confidence intervals. Kaplan-Meier and adjusted Cox proportional hazards analyses were used to assess reoperation- and revision-free survival.

RESULTS: Compared with cTHA, pTHA demonstrated a lower risk of reoperation (P = 0.03), whereas there was no significant difference to rTHA (P = 0.42). Intraoperatively, cTHA demonstrated higher odds of transfusion compared with pTHA (P < 0.01), but similar to rTHA (P = 0.06). Operative duration for cTHA (124.3 minutes, range, 70 to 250) was longer than pTHA (93.5 minutes, range, 56 to 142; P < 0.01), but shorter than rTHA (177.3 minutes, range, 79 to 392; P < 0.01). The mean lengths of stay for cTHA (3.3 days, range, one to 17) were longer than pTHA (2.5 days, range, zero to eight; P < 0.01), but similar to rTHA (3.4 days, range one to 17; P = 0.92).

CONCLUSION: This study establishes cTHA as a distinct surgical category with perioperative and postoperative risks between those of pTHA and rTHA, underscoring the need to classify it separately for surgical planning, resource allocation, and patient counseling.