Subsidence of collarless uncemented femoral stems in total hips replacements performed for trauma.

INTRODUCTION: Collarless, uncemented, femoral stems give excellent results in elective hip replacements but few studies look at outcomes in trauma patients. The presence of osteoporosis and subsequent widened femoral canal may compromise the mechanical stability of uncemented femoral stems resulting in early subsidence. The aim of this study was to assess whether early subsidence occurred when collarless uncemented stems were used to treat trauma patients.

MATERIALS AND METHODS: Post-operative radiographs of 46 patients, mean age 71, who underwent an uncemented, collarless, total hip replacement for trauma, were reviewed. The difference in distance from the calcar to the prosthesis tip between the immediate post operative radiograph and the subsequent follow-up radiograph was calculated and adjusted for magnification. The same procedure was performed on 36 age-matched patients, who underwent elective hip replacements for osteoarthritis. Hospital notes were reviewed to assess for complications and DEXA scans reviewed for trauma patients where available.

RESULTS: The mean femoral stem subsidence was significantly greater in the fracture cohort than in elective patients (p=0.001) with mean subsidence of 4.27 mm (range 0.02-22.05 mm) and 1.57 mm (range 0-5.5 mm), respectively. In the fracture cohort there were 4 revisions within 6 months of surgery, 1 for infection and 3 for femoral stem subsidence leading to dislocation. There were no revisions in the elective cohort.

DISCUSSION AND CONCLUSIONS: This study showed that collarless uncemented stems subsided significantly more when performed for fractures and had a high early revision rate. We recommend that uncemented collarless should not be used in trauma patients requiring total hip replacement.