A PROSPECTIVE RANDOMIZED CLINICAL TRIAL ASSESSING THIGH PAIN AND STRESS SHIELDING IN PROXIMAL TAPERED VERSUS FULLY COATED CYLINDRICAL FEMORAL COMPONENTS

Abstract

Controversy continues to exist regarding the choice of a cementless femoral component in a primary total hip arthroplasty. Both proximally coated tapered stems and fully coated cylindrical stems have excellent clinical results. The incidence of both thigh pain and proximal femoral stress shielding and multiple validated outcome measures were evaluated in a prospective randomized clinical trial with a minimum of two year follow-up comparing a proximally coated tapered femoral stem to a fully coated cylindrical femoral stem.

A prospective randomized clinical trial (RCT) was performed comparing a cylindrical cobalt chrome fully coated femoral stem (Prodigy, Depuy, Warsaw, IN) to a tapered, titanium, proximally porous coated stem (Synergy, Smith & Nephew,

Memphis, TN) with respect to thigh pain, femoral stress shielding and multiple outcome measures.

One hundred and ninety-four patients were enrolled and evaluations were performed pre-operatively, three months, six months and annually. Multiple outcome measures (Harris Hip Score, SF12, WOMAC, Patient Satisfaction Questionnaire, Thigh Pain Questionnaire) were obtained. Sixty-one of these patients were randomized to receive a bone density scan pre-operatively, two weeks post-operatively, six months and annually.

Twelve patients were unavailable for two-year follow-up, leaving one hundred and eighty-two patients evaluated. No significant differences were demonstrated in thigh pain incidence or the multiple outcome measures. Bone density scans demonstrated significantly greater bone density (p< 0.005) in the tapered stem versus the cylindrical stem patients at two-week evaluations from distal femoral reaming. Both stem designs demonstrated statistically significant bone loss in Gruen zones one, six, seven between the two-week and one and two-year evaluations. There were no differences between stem designs although the Prodigy stem demonstrated trends towards greater bone loss in Gruen zones six and seven.

This prospective RCT demonstrated no difference in thigh pain incidence and multiple outcome measures between patients receiving a proximally coated tapered versus a fully coated cylindrical femoral component. Both stem designs demonstrated statistically significant proximal femoral bone loss between the post-operative and two-year evaluations; however, there were no differences between stem designs.