DOES STEM DESIGN AFFECT THE INCIDENCE OF PERIPROSTHETIC FEMORAL FRACTURES AFTER ARTHROPLASTY FOR FEMORAL NECK FRACTURES? A SECONDARY ANALYSIS OF THE HEALTH TRIAL

Periprosthetic femoral fractures (PFFs) after arthroplasty for fragility femoral neck fractures (FNFs) remain a major concern, as they carry high morbidity for this sensitive population. In this study we tried to evaluate how stem design influences the risk of PFFs after hemiarthroplasty (HA) or total hip arthroplasty (THA) for low energy FNFs. We performed a secondary analysis to the HEALTH trial; a multicenter, prospective randomized control trial which assessed THA vs HA for low-energy FNFs at 2 years. We assessed 1374 patients (414 male, 960 female) with a mean age of 80 years. The incidence of PFFs was compared between cemented vs cementless stems. Within the cemented stem group (n=896), we further analyzed the effect of taper-slip (n=482) vs composite-beam (n=414) designs, while within the cementless stem group (n=478), we assessed the impact of single-wedge stems (n=206) vs metaphyseal filling stems (n=272). The role of a collar (n=87) was also examined, within the press-fit stems. Student's t-tests were used to assess continuous variables, and chi-squared tests for categorical variables. Statistical significance was set at p < 0 .05. Between the 1374 patients of this study, 72 patients sustained a PFF (5.2 %). Early PFFs (90 days) in 15 patients. Cemented stems had significantly lower incidence of PFFs, as compared to their cementless counterparts (2.6% vs 10.3%, p 0.05). Most of the PPFs in the composite-beam group occurred early (83%), while most of taper slip PPFs were late (55%). There was no difference between the examined press-fit stems, while the presence of a collar did not show protective results (p>0.05). In this population, cementless stems have a very high PFF rate, regardless the type of stem or the presence of collar. Cemented fixation is the safest option. Composite beam stems have higher early PFF rate. Taper-slip stems are responsible mostly for late fractures; raising concerns about their performance in longer follow-up.