Femoral neck fracture following ipsilateral total knee replacement: an analysis of associations and risk factors

There have been case reports of ipsilateral femoral neck fracture after total knee replacement. This occurrence has been attributed to risk factors such as rheumatoid arthritis, osteoporosis, steroid use and poor mobility. The aim of this study was to see if total knee replacement is a risk factor for neck of femur fracture and to study the associated risk factors. Twenty two patients who had sustained subsequent ipsilateral femoral neck fracture were identified from 1,362 patients who had previously undergone a posterior cruciate ligament-substituting total knee replacement. Clinical chart review and radiological assessment were performed. The average age of the patients was 77(+/- 7) years and the fracture occurred 35(+/- 27) months following the total knee replacement. Positive associations were identified between ipsilateral neck of femur fracture and total knee replacement (P < 0.01), age (P < 0.01), female sex (P < 0.025) and rheumatoid arthritis (P < 0.05). We did not find an association between ipsilateral neck of femur fracture following total knee replacement and preoperative knee deformity (P > 0.5). We also observed an increased risk of supracondylar fracture of the ipsilateral femur in patients who had sustained a neck of femur fracture following total knee replacement (P < 0.001).