Background: Use of modern cementing techniques
for fixation of femoral components in total hip arthroplasty has
had excellent clinical and radiographic results in most patients.
However, several authors have described early loosening of femoral
components with roughened and precoated finishes. The purpose of
this study was to examine the performance of the precoated Iowa
stem, which has increased offset, and to compare the results with
those of another cemented precoated femoral component with standard
offset used at our institution.
Methods: We carried out a prospective analysis
of 102 primary hybrid total hip arthroplasties (a cementless acetabular
component and a cemented femoral component) performed with use of
the Iowa femoral component in ninety-five patients at our institution.
The Iowa stem was used in hips that required greater offset than
is available with standard stems as determined by preoperative templating.
The average age of the patients at the time of the index procedure
was sixty-nine years. Sixteen patients (seventeen hips) died before
the forty-eight-month minimum follow-up period had elapsed. Two
patients were lost to follow-up, and radiographic follow-up was
incomplete for one. The mean duration of clinical and radiographic follow-up
of the remaining eighty-two hips in the seventy-six surviving patients
was sixty-five months (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 total 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 survival 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 make it difficult
to achieve a good cement mantle, and, in combination with the geometry
and increased offset of the stem, may compromise the long-term survival
of this cemented femoral component.