Radiostereometric Analysis Comparison of Wear of Highly Cross-Linked Polyethylene Against 36- vs 28-mm Femoral Heads

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Abstract

This study used radiostereometric analysis (RSA) to compare the femoral head penetration of 28- vs 36-mm-diameter femoral heads into highly cross-linked polyethylene in 2 groups of total hip arthroplasty patients. Thirty patients were enrolled in this RSA study using highly cross-linked polyethylene (Longevity, Zimmer Inc, Warsaw, Idaho) against either 28- or 36-mm-diameter cobalt chrome femoral heads. At 3-year follow-up, there was no significant difference in the total average femoral head penetration, including both creep and wear, using 3 methods of RSA measurement between the 2 groups. Importantly, after bedding-in, there was no further significant increase in the amount of femoral head penetration (ie, wear) with either head size between years 1 and 3. There were no radiographic signs of lysis or radiolucencies at a minimum 3-year follow-up.

Section snippets

Methods

Institutional review board approval was obtained for this nonconsecutive, nonrandomized clinical study. Thirty patients in need of primary THA were enrolled in this RSA hip study in which all patients received e-beam–irradiated and subsequently melted, highly cross-liked polyethylene. Sixteen patients received cementless Trilogy Acetabular components (Zimmer Inc, Warsaw, Ind) with 28-mm-diameter femoral heads, and 14 patients received the same type of components with a 36-mm femoral head

Results

The initial group of patients enrolled in the study consisted of 19 men and 11 women with an average of 56.1 (range, 36-77) years of age at surgery. The most common primary diagnosis was osteoarthritis (12 patients). Additional primary diagnoses were developmental abnormalities (7 patients), avascular necrosis (4 patients), slipped capital femoral epiphysis (2 patients), and other (5 patients). Since surgery, 4 patients refused follow-up for the study, and 1 hip was revised because of recurrent

Conclusion

Regardless of analysis method, no significant measurable wear of the highly cross-linked polyethylene was detected in either group. The 3 analysis methods were found to yield comparable femoral head penetration results. The results obtained using the marker-free version of the RSA software from the same set of radiographs show good agreement with the standard RSA method and shell + marker RSA method, which use tantalum beads attached to the implants. This method allows inclusion of images in

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Benefits or funds were received in partial or total support of the research material described in this article from Zimmer Inc (Warsaw, Ind).

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