FEMORAL STEM DESIGN INFLUENCES POSTOPERATIVE PERIPROSTHETIC FEMORAL FRACTURE (POPFF) AND COMPLICATION RISK: TEN- TO 15-YEAR FOLLOW-UP OF 3,199 TOTAL HIP ARTHROPLASTIES FROM TWO INDEPENDENT CENTRES

As postoperative periprosthetic femoral fractures (POPFF) continue to increase in prevalence, understanding the underlying associated risk factors is important. The aim was to compare the survivorship and POPFF rate of a composite beam (CB) stem with a polished taper slip (PTS) stem. Between 2008 and 2013, 3199 consecutive THAs were performed using either the Exeter V40 (PTS, n=2177) or the Lubinus SP II (CB, n=1021) femoral stem. Patient demographics and operative details were collected prospectively. Patient records and radiographic archives were reviewed at minimum 10-years following surgery to identify subsequent revision surgery, dislocation or POPFF. At mean 11.8-year follow-up (10 to 15), 2214 patients (984/3198) remained alive. Mean patient age at surgery was 67.6 years (SD 11.2). Analysis of all-cause THA failure demonstrated CB stem survivorship of 97.3 % (95.3%–99.2%) and PTS stem survivorship of 95.8% (94.8%– 96.8%) at 13 years (P=0.001). POPFF accounted for 49% of major reoperations (n=36/73) in the PTS group, where 86% of POPFFs underwent ORIF. Multivariate analysis controlling for age, sex, ASA class, and mortality demonstrated that a PTS stem (HR 5.17, P= 0.002) and older patient age at surgery (HR 3.19, P <0.001) were significant predictors of POPPF. Risk of dislocation was higher in the CB group (RR 2.1, CI 1.0 – 4.3, P = 0.03). Patients may be counselled that POPFFS are the main cause of major reoperation following PTS stems, most often treated with ORIF. Overall survivorship remains excellent in both CB and PTS stems and other factors may influence final implant choice.