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Cluster-hole acetabular component yields small volumes of osteolytic lesions after THA
Relatively small volumes of osteolytic lesions were found among patients who underwent total hip arthroplasty with use of a cluster-hole acetabular component, according to study results.
Researchers randomly assigned 100 patients undergoing total hip arthroplasty to either a solid-backed or a cluster-hole acetabular component, all without screws. At the time of surgery, 12 patients received a cluster-hole cup with screw augmentation.
The researchers performed functional assessment before surgery and again at 2 years and 5 years postoperatively using Oxford Hip Scores and SF-12.
Five-year CT scan showed 34.4% of all patients had osteolytic lesions. According to the per protocol analysis, osteolysis was found in 35.7% of patients who received cluster-hole cup without screws, 41.7% of patients who received cluster-hole cup with screws and 29.2% of patients who had a solid cup.
Using linear mixed models, the researchers found no differences in any of the functional outcomes between the cluster-hole cup without screws group and solid cup group. Results also showed improved Oxford Hip Scores and SF-12 scores at the 2-year mark, which were maintained at 5 years, according to the researchers. – by Casey Tingle
Disclosure: The researchers report no relevant financial disclosures.
Perspective
Back to TopThe authors are to be congratulated on a well-conceived and well-executed study. In this work, 100 patients were randomized to receive either a solid-backed component, or an otherwise identical implant with 3 cluster-holes for adjunctive screw fixation. Both implants utilized highly cross-linked polyethylene liners. Of note is that the particular implant studied had a highly polished surface, in hopes of decreasing backside wear of the liner.
No difference between the groups was found with regard to osteolysis volume based on CT scans obtained 5 years after surgery; 34% of the entire group had osteolytic lesions. The average volume of osteolytic lesions was small, averaging 1.98 mm3. There was no difference in clinical outcome; among 12 patients who had adjunctive screw fixation, there was no statistically significant increase in osteolytic volume when compared with solid or cluster hole cups without screws, although the small sample size in the adjunctive screw group reduces the power of this conclusion.
There are important clinical conclusions from this study. First, at least for the implant system studied (Reflectionr, Smith & Nephew), there appears to be no advantage conferred by a solid cup design with regard to osteolysis potential. Therefore, the surgeon should not hesitate to use this implant with screw holes, and always have the option for adjunctive screw fixation. The question as to the effects of screw use on the osteolysis risk cannot be answered by this study. Lastly, it appears when compared with earlier studies of modular acetabular implants that did not use highly cross-linked polyethylene, that the “new” polyethylenes produce a significant reduction in osteolysis volume at 5 year’s follow-up.