Biodegradable polylevolactic acid implants have become more commonly used for the treatment of fractures and osteotomies over the past few years. In the present study, the biocompatibility and degradation of polylevolactide screws used for rotational acetabular osteotomy were assessed on the basis of radiographic and MRI findings.
Forty-nine hips of 47 patients were analyzed for this study. The average age of the patients at the time of surgery was 38.0 years (range 18-62 years). The original diagnosis was osteoarthritis in 43 hips and osteonecrosis in 6 hips. The mean duration of follow-up was 2.8 years (range 1.5-5.5 years). Anteroposterior radiographs obtained at 1 week, 6 months, 1 year after the operation, as well as the most recent radiographs, were used to assess bony union, the radiolucent tract of each screw, and the sclerotic rim around each screw. Fifteen patients were chosen randomly to undergo MRI.
Union of the osteotomized surfaces occurred in all patients within 6 months of surgery. Radiographs showed no osteolysis, no formation of bone cysts, and no displacement of the osteotomized acetabulum in any of the 49 hips. None of the patients was found to have any complications caused by problems with the biocompatibility of the implants. At the final postoperative examination, a central radiolucent tract and a sclerotic rim around the screws were seen in 34/49 hips (69%) and 23/49 hips (47%), respectively. On MRI findings, we were able to detect significant resorption of the screws in two patients after 1.2 and 1.7 years of follow-up. Though localized low-intensity areas on T1-weighted images and high-intensity areas on T2-weighted images were observed at the top of the screws in 5 patients, there was no development of pain, tenderness, or a sinus during the follow-up period.
Although absorption of polylevolactic acid screws did not occur in a large majority of cases, rotational acetabular osteotomy appears to be a good indication for the use of polylevolactic acid screws.