Bone tunnel remodeling at the site of biodegradable interference screws used for anterior cruciate ligament reconstruction:: 5-year follow-up

Purpose: The purpose of this prospective study was to review, using expanded clinical-assessment tools, the long-term results of the local effects of a bioabsorbable interference screw (copolymer 85/15 D,L lactide/glycolide) in anterior cruciate ligament (ACL) reconstruction. Type of Study: This prospective study was initiated in May 1993. The inclusion criteria for patient selection included rupture of the ACL in athletic patients without involvement of the collateral ligaments, arthroscopic ACL reconstruction using middle third of the ligamentum patella, and magnetic resonance imaging (MRI) and plain radiographic examinations of the knee joint during follow-up. Materials: Between May 1993 and October 1994, 32 patients were enlisted in the study; 48 patients did not fit the inclusion criteria. There were 25 men 7 women. The average age was 29.1 years (range, 19 to 50 years). There were 21 right knees and 11 left knees. The follow-up examinations were performed by an independent examiner. There were 28 patients available for follow-up at a medium of 5.2 years (range, 4.1 to 6.4 years). The evaluation included various testing systems (i.e., OAK, IKDC, Lysholm) as well as MRI and plain radiographic studies to investigate the longevity of the implant and potential adverse effects of this new bioabsorbable material. Results: The clinical results were good. The OAK score (Orthopadische Arbeitsgruppe Knie) showed 93% excellent and good results, and 7% fair results. The IKDC and Lysholm scores were 92% and 96% good and excellent results, respectively. MRI showed bone remodeling and new bone formations at the site of the implant in the femoral as well as in the tibial bone tunnel at follow-up. No cystic or osteolytic changes where seen on MRI or plain radiographs. Conclusions: This study showed the correlation between histology and MRI: there was minimal surgical-site edema, minimal reaction to this material, and complete replacement by new bone formation of the previous site of this implant. At 5 years, this bioabsorbable interference screw appeared clinically safe and effective for fixation of bone blocks during ACL reconstruction and MRI showed complete absorption and replacement with new bone.