Heat and Illumination on the Important Topic of Postoperative Periprosthetic Femoral Fractures

Commentary The epidemiology and outcomes of postoperative periprosthetic femoral fractures (POPFFs) following total hip arthroplasty (THA), particularly as they relate to femoral stem selection, remain poorly defined. This is partly due to the low incidence of POPFFs and the fact that most national registries focus primarily on revision surgical procedures, not on open reduction and internal fixation for these fractures. In their study, Lamb et al. address this gap by combining femoral open reduction and internal fixation data from the U.K. National Health Service (NHS) with POPFF revision data from the U.K. National Joint Registry (NJR). This approach contributes novel insights into the relationship between femoral stem selection and POPFF outcomes. The authors report data on the prosthesis time incidence rate (PTIR), adjusted PTIR, and relative risk (hazard ratio) in relation to the choice of femoral implant, grouped into 3 main categories: cementless, cemented composite beam (CB), and cemented polished taper slip (PTS). To minimize bias, the study carefully adjusted for confounding variables and excluded POPFFs occurring within 3 months after a THA, as these fractures are presumed to be intraoperative in nature. Subanalyses were also performed on patients >70 years old and those with diagnoses other than osteoarthritis. The study included 809,832 of 1,128,684 patients who underwent primary THA between January 1, 2004, and December 31, 2020, after applying matching and exclusion criteria. At 10 years postoperatively, the incidence of surgical procedures for POPFFs was 0.9%, with slightly more cases being treated with fixation than revision. The authors found that CB stems were associated with the lowest risk of POPFF, whereas cementless and PTS stems had similar, but higher, rates of fracture. These findings suggest that the design of the femoral stem may be as important as, if not more important than, the method of fixation in preventing POPFF. Although the study provides valuable insights, it also highlights both the strengths and limitations of using national registry data. The authors are to be commended for their efforts in linking large, independent data sets and attempting to minimize selection bias, a common issue with observational registry studies. However, several biases still exist and should be considered before drawing practice-changing conclusions from the results. These biases include: Differences in group sizes: There is a notable disparity in the number of cases across the different femoral stem groups, with a single stem design in the PTS group comprising 3 times as many cases as the next most common stem, which was cementless. This is important because cemented PTS stems are often recommended for femora at higher risk for fracture, such as those in patients with patulous anatomy. Exclusion of early POPFFs: The study excludes fractures occurring within 3 months after the surgical procedure, under the assumption that these represent intraoperative fractures. However, when selecting the femoral stem design, other important outcomes, such as mortality, must be considered, particularly in patients undergoing THA for a femoral neck fracture. Previous studies have shown that cementless fixation in THA for femoral neck fracture is associated with higher mortality rates compared with cemented stems, potentially due to intraoperative fractures that require prolonged bed rest or additional surgical procedures1. Selection bias over time: The study does not account for changes in surgical practice patterns over time, which may introduce bias. For example, variations in the use of certain stem designs or fixation methods may be influenced by evolving clinical preferences, which are not captured in this analysis. Loss of detail in the cementless group: The cementless group contains a broad range of femoral stem designs, but this diversity is not explored in detail. By grouping all cementless stems together, the study loses an opportunity to better understand the specific effects of different cementless stem designs. Despite these limitations, the study adds valuable data to the ongoing discussion on femoral stem selection in THA, particularly with respect to POPFFs. The increasing use of cementless THA worldwide and the growing importance of understanding the risk factors for POPFFs highlight the need for further research in this area2,3. Although Lamb et al. correctly advocate for a more nuanced categorization of stem designs to improve predictions of stem performance, the findings should be interpreted with caution, especially considering the biases and limitations noted above. As the field of THA continues to evolve, there will be increasing emphasis on personalized surgical approaches and patient-specific implant selection.

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