Leg length discrepancy risk differs between fit-and-fill and taper wedge stems across Dorr types.

Introduction: The comparison between the cementless taper wedge stem and fit-and-fill stem in total hip arthroplasty (THA) for various proximal femoral morphological types has not been thoroughly assessed. This study aimed to compare the risk of leg length discrepancy (LLD) ≥ 10 mm between these two stem types in Dorr type A, B, and C femurs.

Materials and methods: From April 2015 through April 2021, we analyzed 1178 unilateral primary cementless THA procedures. We categorized all procedures into three groups: Dorr type A (N = 220, 18.7%), B (N = 875, 74.3%), and C (N = 83, 7.0%). Within each Dorr type, we compared the incidence and risk of postoperative LLD ≥ 10 mm between the two stem types. The factors considered in the multivariate regression analyses included stem type, age, sex, body mass index, diagnosis, canal flare index, femoral cortical index and stem alignment.

Results: The taper wedge stem group had a higher overall incidence of LLD ≥ 10 mm (12.8% vs. 7.4%, P = 0.012) and in Dorr type A femurs (22.2% vs. 7.6%, P = 0.014), compared with the fit-and-fill stem group. In multivariate analysis, the taper wedge stem exhibited an increased risk of LLD ≥ 10 mm only in Dorr type A femurs (aOR: 3.449, 95% CI: 1.325-8.794). The incidence and risk of LLD ≥ 10 mm were not different between the two stems in Dorr type B and C femurs.

Conclusions: The taper wedge stem demonstrated an elevated risk of LLD ≥ 10 mm in Dorr type A femurs compared with the fit-and-fill stem, necessitating meticulous preoperative templating and intraoperative femoral canal preparation.