A PROSPECTIVE RANDOMISED STUDY TO COMPARE PROXIMAL FEMORAL BONE REMODELLING AFTER HIP ARTHROPLASTY USING 3 DIFFERENT FEMORAL STEM DESIGNS

Abstract

We aimed to determine whether proximal femoral bone remodelling, as measured by DEXA scan for each Gruen Zone, differed for 3 different femoral stem designs. These were:

• Group 1 – Triple taper polished (C-stem J& J DePuy)

• Group 2 – Double taper polished (TPS J& J DePuy)

• Group 3 – Collared satin finish stem (Stanmore Biomet)

Ethical Committee approval was obtained and all patients gave informed consent. All operations were performed by 3 surgeons using a standard lateral approach, third generation cementing technique and a standard post-operative regime.

Seventy-five patients were randomised prospectively using a stratified randomisation programme for known risk factors in bone density. The randomisation was stratified by age, sex, Charnley Group (A or B), BMI and femoral neck bone mineral density. There were 25 patients in each Group, 5 patients did not have complete data sets and were therefore withdrawn from evaluation.

The Groups were similar with regard to age, sex, BMI, BMD and Charnley Group. Patients were followed up at 3, 6, 12 and 24 months by Nurse Practitioners for clinical and radiological evaluation and DEXA scan at each time of follow-up. There were no catastrophic failures of sepsis or dislocation. All patients functioned well at 24 months by Harris Hip Score.

The bone remodelling pattern will be described for each stem design. Findings are summarised thus. In the lateral Gruen Zones the triple taper and collared stem design faired better and both behaved differently to the double taper design. In Gruen Zone 7, all stems demonstrated reduced bone density as compared to pre-operative scans but this was less with the triple taper design.