Periprosthetic Femoral Fractures around Primary Total Hip Replacements

Post-operative periprosthetic femoral fractures (POPFF) increase morbidity and mortality, and premature failure of hip replacements. POPFF is most likely after cementless femoral stem implantation and are caused by intraoperative and post-operative injury. Prevention of POPFF may be possible by modifying implant selection, design and use.
Propensity matched survival analysis of 4831 intraoperative periprosthetic femoral fractures (IOPFF) from the National Joint Registry of England, Wales and the Isle of Man (NJR) identified increased risk of POPFF revision and mortality when compared to propensity matched controls. IOPFF risk-factor modelling using 793977 primary total hip replacements identified that cementless femoral implants doubled the risk of any IOPFF, but particularly calcar and shaft fractures. A novel design-linked analysis of 349161 cementless hip replacements from the NJR identified stem features which were associated with increased risk of POPFF within 90-days, including: collarless design, mineralised and porous coatings, and triple-tapered stem bodies.
A novel manual segmentation method to analyse POPFF fracture patterns was developed and used to analyse a series of 125 cases from four large UK centres. This analysis demonstrated that POPFF within 90 days occurred almost exclusively around the femoral stem, probably as a result of rotational and axial forces. Experimental simulation of early POPFF in paired cadaveric femurs established that the force required to fracture was increased when a calcar collar was present. Further testing revealed that the increased fracture resistance during simulation was dependent on calcar-collar contact and was most likely when the initial separation was 1 mm or less.
A strong relationship between femoral implant design and risk of subsequent POPFF exists. The ability to associate specific design features with clinical outcomes and ratify the findings with experimental methods will help to develop this field further and improve implant use and design for future generations of patients with hip replacement.