Biomechanical comparison of cemented versus cementless fixation in intraoperative femoral fractures during total hip arthroplasty.

Introduction: Intraoperative periprosthetic femoral fractures (IPFF) are serious complications of total hip arthroplasty (THA) that occur more frequently with cementless stems than with cemented stems. Although cerclage wiring is commonly used to stabilize IPFFs, the biomechanical effects of subsequent stem fixation methods remain unclear. This study aimed to compare the biomechanical stability of cemented and cementless stems following cerclage wire fixation in an experimental IPFF model.

Materials and methods: Six fourth-generation composite femurs with simulated Vancouver A2-type fractures were stabilized using a single 1.8 mm cerclage wire. Identical stem designs of polished cemented stems and fully hydroxyapatite-coated cementless stems were implanted in three specimens of each group. After applying a vertical axial load of 2000 N, an additional 40° of internal rotation was imposed. The primary outcome was the maximum torque at the time of fracture. Secondary outcomes included the maximum internal rotation angle, construct stiffness (calculated from force-displacement curves above 1500 N), and peak strain at three positions on the cerclage wire, measured using strain gauges.

Results: The maximum torque was significantly higher in the cemented group compared to the cementless group (160.8 ± 24.9 vs. 89.1 ± 18.0 N·m, p = 0.016). Although the differences in stiffness and internal rotation angle were not statistically significant, both trended higher in the cemented group. The peak strain was consistently lower in the cemented group, with a significant difference at the medial side of the fracture line (p = 0.011, Cohen's d = - 3.64).

Conclusions: Cemented stems demonstrated superior biomechanical stability following cerclage wire fixation in the IPFF model, likely because of improved stress distribution via the cement mantle. Therefore, cemented fixation may be a favorable option for managing IPFF during THA.