Periprosthetic femoral fracture type and location are influenced by the presence of an ipsilateral knee arthroplasty implant: A case-control study of 84 interprosthetic femoral fractures.

Abstract

This multicentre case-control study compares Vancouver Classification System (VCS) grade and Arbeitsgemeinschaft für Osteosynthesefragen/Orthopaedic Trauma Association (AO/OTA) fracture type in interprosthetic femoral fractures (IPFFs) between primary total hip arthroplasty (THA) and ipsilateral total knee arthroplasty (TKA) to periprosthetic femoral fracture (PFF) without ipsilateral TKA. Data were collected following institutional approval. Eighty-four IPFFs were assessed for VCS grade and AO/OTA type. Each IPFF case (84) was matched to five PFF controls (360) by age, gender and stem fixation philosophy (SMD<0.1). VCS grade and AO/OTA type were compared between the IPFF and PFF groups using weighted proportions and medians. Median (IQR) age of IPFF patients was 81.75 (76.57-85.33) years and 61 (72.6%) were female. The commonest VCS grade was B1 (34, 40.5%). The commonest AO/OTA type was spiral (51.8% of VCS B fractures; 50.0% of VCS C fractures). A greater proportion of fractures occurred distal to the stem in IPFF patients versus PFF patients (33.3% versus 18.2%, p = 0.003). VCS grade was significantly different between groups (p = 0.015). For VCS C fractures, twice as many AO/OTA transverse and wedge fractures occurred in the IPFF group compared to the PFF group (25.0% versus 12.6% and 7.1% versus 3.3%, respectively) although the overall difference was not statistically significant (p = 0.407). The presence of an ipsilateral TKA affects the location of PFF with more fractures occurring distal to the stem. A greater proportion of bending type fractures occurred when an ipsilateral TKA was present. These unstable fractures often require more complex surgery.