Introduction There are clear theoretical advantages to support the use of bioabsorbable interference screws in the reconstruction of the anterior cruciate ligament. The purpose of this study is to determine how long it takes for an ACL screw marketed as bioabsorbable to be absorbed in the tibia.

Methods Eight patients that underwent an ACL reconstruction utilising a femoral endobutton and tibial bio-absorbable screw (Arthrex Bio-interference) made of Poly-L-Lactide (PLA) were followed up radiographically with sequential MRI scans at one, two and four years post-operatively. The scans, (Axial T1 and T2 with minimal interslice gap) were assessed by two independent consultant radiologists.

Results There was no evidence radiologically of progression to absorption of the tibial screw on any scan. The MRI appearance remained unchanged from one to four years with the exception of the presence of a small cyst in the tunnel of one of the patients.

Conclusions Despite claims by manufacturers of rapid rates of bio-absorption of their products, this study questions the accuracy of such statements not tested in-vivo. Our study clearly shows the continued presence of such a bioabsorbable screw at four years post-operatively.