¹Schulthess Klinik, Zürich, Schweiz
²Gelenkzentrum Zürich, Zürich, Schweiz
³Cantonal Hospital Winterthur, Winterthur, Schweiz

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Objectives and questions: Conversion total hip arthroplasty (cTHA) is challenging after failed osteosynthesis of hip fractures and often considered a revision rather than a primary THA (pTHA) intervention. This study aims to compare the mid- to long-term postoperative functional and radiological outcomes as well as the reported complications between cTHA patients after failed proximal fracture fixation and pTHA patients.

Material and methods: From a retrospective analysis of prospectively collected registry data, 58 cTHA patients with failed osteosynthesis of AO/OTA Types 31A and B proximal femoral fractures were propensity matched with 111 patients who underwent pTHA for hip osteoarthritis. Baseline, operative and radiological data, complication rates, and various patient-reported outcomes (PROs) of hip function and activity as well as quality of life were examined up to 5 years post-THA and compared between groups. The influence of fracture type on the 5-year PROs of cTHA patients was also explored. Categorical data were compared with Fisher’s exact and Pearson's chi-squared tests and the Welch’s two-sample t-test.

Results: Of the 58 patients with pertrochanteric (AO 31A) and femoral neck fractures (AO 31B), mal-/nonunion (n=24; 41%) and symptomatic osteoarthritis (n=18; 31%) were the leading causes for cTHA. The mean duration for cTHA (118 mins) was significantly longer than that for pTHA (72 mins). There were no significant differences in implant positioning between groups, but more heterotopic ossification was observed in cTHA patients, particularly those with AO 31A fractures. A total of 39 postoperative adverse events (AE) were documented. 17 (27%) AEs were found in the cTHA group and 22 (19%) in pTHA group. Although earlier (6 and 24 months) postoperative PROs indicated cTHA patients with worse hip function, activity, pain levels and quality of life over pTHA patients, these group differences were no longer apparent by the 5-year follow-up. Fracture type did not have an effect on PROs.

Discussion and conclusions: Conversion THA is the more challenging procedure over pTHA with longer surgical time and higher local complication rate, but the entire patient cohort shared similar 5-year PROs, indicating that even conversions can achieve satisfying results in the long-term clinical course. Salvage cTHA appeared to be less demanding after femoral neck fractures compared to revisions for failed peri-trochanteric fractures. Bone stock should therefore be preserved in femoral neck fractures without advanced osteoarthritis by osteosynthesis, whereby conversion THA is a feasible option in the further course.