Biodegradable and metallic interference screws in anterior cruciate ligament reconstruction surgery using hamstring tendon grafts: prospective randomized study of radiographic results and clinical outcome

BACKGROUND: The use of biodegradable screws in anterior cruciate ligament reconstruction has grown in popularity. PURPOSE: To compare the clinical and radiographic results in arthroscopically assisted anterior cruciate ligament reconstruction using 4-strand hamstring tendon grafts and either metallic (metal group) or biodegradable (PLLA group) interference screw fixation. STUDY DESIGN: Randomized controlled trial; Level of evidence, 1. METHODS: A randomized series of 77 patients, all with a unilateral anterior cruciate ligament rupture, was included in the study. The preoperative assessments in both groups were similar in gender, Tegner activity level, Lysholm score, KT-1000 arthrometer measurements, and single-legged hop test results. In both groups, interference screw fixation of the graft was used at both ends, and 68 of 77 (88%) patients returned for a radiographic examination at 6 and 24 months, respectively. RESULTS: At follow-up, no significant differences were found between the 2 groups in KT-1000 arthrometer laxity measurements, Tegner activity level, or Lysholm score. The PLLA group had a significantly better outcome in the single-legged hop test and the final International Knee Documentation Committee classification (P = .007 and P = .03, respectively). At 6 and 24 months after the index operation, the PLLA group displayed significantly larger drill holes on the radiographs than did the metal group on both the tibial (8.1 vs 6.6 mm at 6 months [P = .0007]; 6.0 vs 3.2 mm at 24 months [P < .0001]) and femoral sides (7.8 vs 5.6 mm at 6 months [P < .0001]; 6.3 vs 1.9 mm at 24 months [P < .0001]). CONCLUSION: There were significantly larger radiographically visible drill holes on both the tibial and femoral sides in the PLLA group compared with the metal group at 6 and 24 months. Clinical examination at 2 years revealed no major differences between the groups. The larger drill holes in the PLLA group did not correlate with inferior clinical results.