Extra-articular migration of PEEK interference screw after anterior cruciate ligament reconstruction: a report of two cases

Background The interference screw is the most popular device that fixes the graft for anterior cruciate ligament reconstruction, reducing the incidence of windshield effect and bungee effect. For the screw, either metallic, "bioresorbable," or polyetheretherketone (PEEK) material is available. PEEK is popular and extensively used due to its stability, biocompatibility, radiolucency, and elastic modulus. Rare relevant complications were reported, but here, we report two cases of extra-articular migrations of PEEK interference screw from the tibial tunnel after anterior cruciate reconstruction. Case report An 18-year-old boy and a 56-year-old woman underwent anterior cruciate ligament reconstruction using a PEEK interference screw to fix the graft in the tibial tunnel. They suffered from screw extrusion from the tibial tunnel after 40 days and six months, respectively, with an incision rupture or palpable subcutaneous mass. They underwent a second operation and recovered well. Conclusions The exact incidence of extra-articular migrations of PEEK interference screws is unknown, but it seems to be quite low; despite this and its uncertain cause, the negative effects caused by the PEEK material need to be considered. Keywords: Polyetheretherketone, PEEK, Anterior cruciate ligament, Interference screw, Migration, Case report