The natural history of a bioabsorbable interference screw used for anterior cruciate ligament reconstruction with a 4-strand hamstring technique

Purpose: The purpose of this study was to assess radiologically the rate of absorption of the Arthrex poly L-lactide bioabsorbable interference screw (Arthrex, Naples, FL) used in anterior cruciate ligament reconstruction with a 4-strand hamstring technique. Type of Study: Case series. Methods: Eight sequential patients undergoing anterior cruciate ligament reconstruction with a 4-strand hamstring technique were assessed with magnetic resonance imaging (MRI) scans at 1, 2, and 4 years postoperatively. Results: There was no radiologic evidence of absorption of the screw on any of the scans. The MRI appearance remained essentially unchanged from 1 to 4 years with the exception of the presence of a small cyst in the tibial tunnel of one of the patients. No edema was seen associated with the tibial tunnel in any of our patients. Conclusions: There are several quoted theoretical advantages to using bioabsorbable screws. The rate of absorption is dependent on material, weight, and degree of crystallization. In our series using an amorphous low crystallization poly L-lactide screw, there was no evidence of any progression to absorption 4 years after implantation. This may be because all series quoted to date look at absorption using a bone-patellar tendon-bone graft. Level of Evidence: Level IV.