Highly Crosslinked Polyethylene Tibial Post Fracture in the Unafflicted Limb of a Patient with Unilateral Lower Limb Poliomyelitis: A Case Report

We present a unique case of tibial post fracture of a posteriorstabilised total knee arthroplasty (PS-TKA) using highly crosslinked polyethylene (HXLPE) in the unafflicted limb of a patient who had poliomyelitis. The tibial post is an upright structure perpendicular to the PE insert articular surface which articulates with the cam of the femoral component to prevent excessive posterior translation of the tibia. We explore the choice of PS polyethylene (PE) inserts in patients with neuromuscular disorders (NMD). A 74-year old gentleman presented with recurrent knee pain seven years after the index PS-TKA with HXLPE. The TKA was performed on the unafflicted left limb (contralateral to the weak side affected by poliomyelitis). The posterior drawer test was positive. During the single-stage revision surgery, the HXLPE tibial post was noted to be broken. The liner was replaced with a thicker non-HXLPE. The patient achieved an excellent outcome at one-year post-surgery. This is the first report of HXLPE tibial post fracture in the unaffected knee of a patient with NMD affecting the lower limb. The HXLPE’s reduced resistance to fatigue crack propagation might not be suitable in PS-TKA where there might be focal stress points on the tibial post, which was amplified in this case as it was the limb that the patient most depended on. When managing end-stage osteoarthritis with TKA in the unafflicted knee of a patient with NMD causing lower limb weakness, the selection of polyethylene material in PS-TKA may need more consideration than previously thought.