Serial magnetic resonance imaging evaluation of a bioabsorbable interference screw and the adjacent bone

The purpose of this prospective study was to review, using expanded clinical assessment tools, the initial use of a bioabsorbable interference screw (copolymer 85/15 D, L lactide/glycolide) in anterior cruciate ligament (ACL) reconstruction at the Wels Hospital, Austria. The study enlisted 32 patients of whom 28 were available for follow-up at minimum of 2.5 years. Since the implant material was new and the screw would not show on plain film radiographs, the clinical assessment was expanded beyond the usual historical and physical findings. The evaluation included opportunistic knee joint aspiration and repeat magnetic resonance imaging (MRI) studies to investigate the longevity of the implant and potential adverse effects of this new bioabsorbable material. The knee joint aspirations showed no infection. Serial MRIs showed the physical presence of the screw to remain intact for 4 months and disappear in 6 months. The MRIs showed minimal collection of edema around the bone tunnels that resolved by 12 months. There were no symptoms or adverse clinical result correlated with the MRI evidence of edema. There was temporary bone tunnel expansion. The clinical results were good. The OAK-score (Orthopadische Arbeitsgruppe Knie) showed 89.5 % excellent and good results, 7% fair results and 3.5 % poor results. The average score was 90.7 points (range, 63 to 100 points). The knee joint stability measured with the KT-1000 arthrometer showed 93% to have a 3-mm or less difference compared with the unoperated knee. This bioabsorbable interference screw appeared safe and effective for fixation of bone blocks during ACL reconstruction while producing no occult infection or adverse clinical response during the degradation process.