Impact of preoperative variables on the functional and radiological outcome of an uncemented femoral stem: a prospective two-year follow-up.

The demand for improved clinical outcomes in total hip arthroplasty (THA) has led to improvements in fixation, bone ingrowth and designs providing an increased range of motion.The purpose of this prospective clinical study was to evaluate the outcome of a new cementless stem (Hipstar). The variables of body mass index (BMI), gender, preoperative function and age were explored as predictors for recovery after surgery. Clinical and radiological evaluation of 100 patients were undertaken preoperatively and at 6, 12 and 24 months postoperatively using the Harris Hip Score (HHS), WOMAC-Score and the SF-36-Score. The mean preoperative HHS was 53.6 + or - 14.5 points and it increased significantly to 82.8 + or - 15.4 at the postoperative evaluation at 24 months (WI-test p<0.001). Diminished preoperative function led to a lower postoperative score, but BMI, age and gender were not predictors of clinical and radiological outcome. Due to stress-shielding the straight Hipstar stem revealed radiolucent lines of between 41.5% and 68.5% in the proximal Gruen zones, which indicates a higher primary and secondary stability by enhanced osseous integration compared to other straight stems. Our clinical results are encouraging, but long-term follow-up will be necessary to confirm the successful introduction of the new Hipstar stem.