Peek screw displacement after PCL reconstruction: A radiographic red herring solved by MRI

Posterior cruciate ligament (PCL) repair has been increasingly performed as opposed to conservative management of PCL tears, in order to protect against future osteoarthrosis and meniscal degeneration. Fixation of the graft to bone can be done with interference screws, of which those composed of a bioresorbable material such as polyetheretherketone (PEEK) are preferred, owing to their inertness, good fixation strength and superior MR imaging compatibility. However, PEEK screws (unlike titanium screws) are radiolucent, and can make accurate post-operative evaluation by radiographs challenging. This is the first reported case of loosening of PEEK screw post-PCL repair, which highlights the importance of MRI and potential pitfall of radiography in evaluating post-surgical ligament laxity.