Hybrid total hip arthroplasty with a precoated offset stem - Four to nine-year results

Background: Use of modern cementing techniques for fixation of femoral comp onents in total hip arthroplasty has had excellent clinical and radiographi c results in most patients. However, several authors have described early l oosening of femoral components with roughened and precoated finishes. The p urpose of this study was to examine the performance of the precoated Iowa s tem, which has increased offset, and to compare the results with those of a nother cemented precoated femoral component with standard offset used at ou r institution. Methods: We carried out a prospective analysis of 102 primary hybrid total hip arthroplasties (a cementless acetabular component and a cemented femora l component) performed with use of the Iowa femoral component in ninety-fiv e patients at our institution. The Iowa stem was used in hips that required greater offset than is available with standard stems as determined by preo perative templating. The average age of the patients at the time of the ind ex procedure was sixty-nine years. Sixteen patients (seventeen hips) died b efore the forty-eight-month minimal follow-up period had elapsed. Two patie nts were lost to follow-up, and radiographic follow-up was incomplete for o ne. The mean duration of clinical and radiographic followup of the remainin g eighty-two hips in the seventy-six surviving patients was sixty-five mont hs (range, forty-eight to 104 months). Results: The average preoperative Harris hip score of 47 points (range, 16 to 69 points) improved to an average of 87 points (range, 24 to 100 points) at the time of the review. Two hips underwent femoral component revision. Four femoral stems were radiographically loose at an average of thirty-four months. Femoral osteolysis was seen in five hips (6 percent) at an average of fifty-four months postoperatively. No acetabular component was revised because of aseptic loosening. According to Kaplan-Meier analysis, the seven -year survival rate, with an end point of femoral revision, osteolysis, or stem debonding, was 90.6 percent (95 percent confidence interval, 0.87 to 0 .94). Conclusions: The prevalence of revision, osteolysis, and loosening after to tal hip arthroplasty with the Iowa femoral component at our institution was higher than that seen in our series of Harris Precoat stems, which had a s urvival rate of 98.4 percent (95 percent confidence interval, 0.97 to 1.00) at ten years with the same end points. The design of the Iowa stem may mak e it difficult to achieve a good cement mantle, and, in combination with th e geometry and increased offset of the stem, may compromise the long-term s urvival of this cemented femoral component.