AB228. 80. Fracture of bio-absorbable interference screw as a source of loose body in the knee

Background: We highlight a rare complication of bio-interference screw fixation in anterior cruciate ligament reconstruction.

Methods: We describe the case of a sixteen-year-old girl who presented to clinic complaining of knee locking and instability one year following an anterior cruciate ligament (ACL) reconstruction using hamstring graft, fixed with a BioComposite™ interference screw (Arthrex, Inc., FL, USA) in the tibia and ACL tightrope in the femur. An MRI revealed a loose body in the knee adjacent to the footplate of the ACL and arthroscopy confirmed that the absorbable bio-interference screw had fractured, with the tip now loose in the joint. The loose body was removed and the knee was found to be stable with the ACL intact and the remaining screw well fixed. She recovered rapidly with full resolution of symptoms.

Results: ACL reconstruction is a very common and well tolerated procedure with low complication rates. Interference screws are the standard for rigid fixation of the graft in the tibial tunnel, with absorbable bio-interference screws growing in popularity. Bio-interference screws are equivalent to metal interference screws in terms of fixation and outcomes however have a number of disadvantages including higher cost and known risk of fracture. To date this fracture has been reported intra-operatively and has not resulted in long-term patient effects however this case demonstrates the potential for detrimental patient effects from fracture of the screw.

Conclusions: Bio-absorbable screws are known to be at risk of fractures and should be investigated as a source for loose bodies in the patient with new locking following ACL repair.

Keywords: Bio-absorbable; screw; fracture; loose; bodies