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 clinica l 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 patien ts of whom 28 were available for follow-up at minimum of 2.5 years. Since t he implant material was new and the screw would not show on plain film radi ographs, the clinical assessment was expanded beyond the usual historical a nd physical findings. The evaluation included opportunistic knee joint aspi ration and repeat magnetic resonance imaging (MRI) studies to investigate t he longevity of the implant and potential adverse effects of this new bioab sorbable material. The knee joint aspirations showed no infection. Serial M RIs 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 aro und the bone tunnels that resolved by 12 months. There were no symptoms or adverse clinical result correlated with the MRI evidence of edema. There wa s temporary bone tunnel expansion. The clinical results were good. The OAK- score (Orthopadische Arbeitsgruppe Knie) showed 89.5 % excellent and good r esults, 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 th e KT-1000 arthrometer showed 93% to have a 3-mm or less difference compared with the unoperated knee. This bioabsorbable interference screw appeared s afe and effective for fixation of bone blocks during ACL reconstruction whi le producing no occult infection or adverse clinical response during the de gradation process.