The effect of cemented femoral component design and prophylactic wire placement against early periprosthetic femoral fracture in primary total hip arthroplasty

Previous studies have highlighted differences in the risk of periprosthetic fractures (PPFs) in patients undergoing total hip arthroplasty with either a cemented taper slip (TS) stem or a composite beam (CB) stem. This biomechanical study explored the occurrence of PPF around these stems, and the protective effect of adding a 16-gauge prophylactic calcar or diaphyseal wire to the TS stems to increase the resistance to torque as a potential way to prevent these fractures. A total of 21 TS stems (eight alone, six with calcar wiring, and seven with diaphyseal wiring placed 2 cm distal to the lesser trochanter) and seven CB stems were cemented into standard sawbones. The peak torque at failure was measured using a servohydraulic test machine, and the fracture location was recorded. An a priori power analysis determined that seven specimens per group were needed to detect a 30 Nm difference with 90% power, assuming a 14.8 Nm SD in peak torque between groups. Comparisons were performed using paired t-tests. CB stems exhibited a significantly higher mean peak torque at failure (205.3 Nm (SD 26.9)) than TS stems (159.5 Nm (SD 17.4); p = 0.012), calcar-wired TS (148.2 Nm (SD 38.6); p = 0.031), and diaphyseal-wired TS (164.9 Nm (SD 21.5); p = 0.027). This study did not demonstrate that wired-TS stems had a higher peak torque at failure than non-wired TS stems. Additionally, calcar wiring was not found to be stronger than diaphyseal wiring (p = 0.400). Four CB fractures occurred distal to the stem, whereas all TS fractures occurred at the mid-stem, simulating a Vancouver type B fracture. Interestingly, adding the diaphyseal wire shifted the fracture location more distally in four of the seven stems (p = 0.070). In this model, CB stems had greater resistance to torque than TS stems, which may explain the lower risk of PPF. Adding calcar or diaphyseal wires to the TS stems resulted in no significant change in peak torque to fracture. CB cemented stems should be considered in patients at high risk of PPF.