Abstract
Total hip replacements have been shown to give superior outcomes in patients with intracapsular fractures of the neck of femur compared with hemiarthroplasty. Collarless uncemented femoral stems give excellent long term results in elective hip replacements but there are few studies looking at their outcomes in fractured neck of femur patients. There is some concern that in trauma patients bone quality maybe inferior as most neck of femur fractures are secondary to osteoporosis. The presence of osteoporosis and subsequent widened femoral canal may compromise the mechanical stability of uncemented femoral stems and result in early subsidence, which can lead to altered leg length and decreased hip stability. The aim of this study was to assess whether early subsidence occurred when collarless uncemented stems were used to treat patients with fractures of the neck of femur.
Post-operative radiographs of 33 patients, mean age 71, who underwent an uncemented collarless total hip replacement for a fracture, were reviewed. The distance from the calcar to the tip of the prosthesis was measured for each patient on the initial post operative radiograph and again on the follow-up radiograph at 6 months post operation. Any subsidence was recorded and magnification for each radiograph was calculated by measuring the diameter of the femoral head, which was known to be 36mm. Distances were then adjusted for magnification. The same procedure was performed on 36 age-matched patients, mean age 71, who underwent elective uncemented total hip replacements for osteoarthritis. Hospital notes for each patient were reviewed to assess for complications and DEXA scan results for trauma patients were also evaluated where available.
The mean femoral stem subsidence was significantly greater in the fracture cohort than in elective patients (p = 0.001) with mean subsidence of 4.07mm (range 0.02–18.5mm) and 1.57mm (range 0–5.5mm) respectively. In the fracture cohort there were 3 revisions within 6 months of surgery, 1 for infection and 2 for femoral stem subsidence leading to dislocation. There were no revisions in the elective cohort. DEXA scan results were available for 21 of the 33 fracture cohort patients. All these patients had abnormal bone density with 52% being osteoporotic and 48% osteopenic.
This study showed that collarless uncemented stems subsided significantly when performed for fractures and had a high early revision rate. We therefore recommend that cemented or collared femoral stems be used in patients with femoral neck fractures requiring total hip replacement to reduce the risk of femoral stem subsidence.
