Intraoperative Femur Fracture is Associated with Stem and Instrument Design in Primary Total Hip Arthroplasty

Intraoperative proximal femoral fracture is a risk in total hip arthroplasty (THA) with cementless stems with reported rates of 1.5-27.8%. Certain designs or designs associated with certain types of instrumentation may have higher rates. We compared the incidence of proximal femoral fracture with two stem and instrument design systems. We retrospectively reviewed 425 patients (457 hips) undergoing primary THAs using a supine, muscle-sparing approach between February 2007 and April 2009. In 439 cases, a monoblock, broach-only, tapered wedge design stem was used with a single low-profile cutting blade (cutting) calcar mill. Eighteen proximally modular, broach-only, tapered wedge design stems were used with a calcar mill with multiple deep cutting teeth (toothed). There were no proximal femoral fractures among the 439 hips using the cutting mill and two intraoperative proximal femur fractures in 18 hips using the toothed mill. Both fractures occurred during calcar milling when the cutting teeth engaged the bone, resulting in a torque of the broach. Given the high intraoperative proximal femur fracture rate using the toothed design, and the absence of fractures using the cutting design, we caution against the use of the toothed style. The overall rate using a flat, wedge, tapered design (two of 457 hips or 0.4%) is lower than that associated with previously published designs. Fracture appears directly related to instrumentation. Level III, retrospective comparison study. See Guidelines for Authors for a complete description of Levels of Evidence.