Maximizing stem body size may reduce the risk of postoperative periprosthetic fractures

Aims: There is concern around an increased risk of postoperative periprosthetic fracture (POPPF) with cemented polished taper slip (PTS) femoral components. We hypothesized that femoral constructs resulting in increased load on the cement mantle would be associated with higher POPPF risk. The aim of this study, based on our hypothesis, was to undertake an analysis of a large cohort of PTS femoral components to understand the role of implant construct variations on the incidence of POPPF. Methods: We retrospectively reviewed 2,757 patients undergoing THA with a PTS femoral component between January 2009 and December 2021. POPPFs were identified using a combination of linked Hospital Episode Statistic, National Joint Registry data, and local records. All fractures were confirmed with review of radiographs and documentation. Demographic data and implant details were collected. Associations between POPPF and potential contributory variables were assessed using univariate and multivariate regression analyses. Results: In total, 40 POPPFs (1.45%) were identified at a mean of 6.4 years (SD 2.9; 0.2 to 10.1) from index procedure. Patients with POPPFs were older (mean age 74.5 years; SD 8.6) than the overall cohort (p < 0.001). BMI, height, weight, and American Society of Anesthesiologists grade were not different. Most fractures were type B (B1 65%, B2 17.5%, B3 5%). One fracture (B1) was managed conservatively, seven (17.5%) were revised, and 32 (80%) fixed. Multivariate analysis showed increased POPPF risk with age (odds ratio (OR) 1.076), but no other patient factors were significant. Offset (OR 1.13, 95% CI 1.04 to 1.22) and construct ratio (head + neck offset/femoral component-size) (OR 3.92; 95% CI 1.31 to 11.79) were strongly predictive. Conclusion: The findings show that, for a given offset, a larger femoral component (reducing the construct ratio) was associated with a lower risk of POPPF. Surgeons should aim to maximize the size of the femoral component to optimize the 'torsional resistance' of the femoral component relative to their reconstructed offset to reduce the risk of POPPF.