Custom-made asymmetric polyethylene liner to correct tibial component malposition in total knee arthroplasty — a case report

A 56-year-old woman presented with knee pain, bow-leggedness, and instability following revision total knee arthroplasty 11 years previously.

A complex surgical history related to her right knee was revealed. At the age of 19, she suffered a midshaft tibial fracture treated non-operatively resulting in a sagittal bowing deformity. The anterior cruciate ligament was reconstructed at the age of 37 and a proximal bony correction using Ilizarov external fixation was done to correct recurvatum at the age of 38. In addition, 10 arthroscopic procedures were performed on the knee from the age of 20 to 34 years. A primary cemented TKA was performed at the age of 44 (NexGen CR, femur size C, tibia size 3, polyethylene 12 mm and patella size 29; Zimmer Biomet, Warsaw, IN, USA). Due to instability a partial revision was done 5 months later where the femoral component was brought distally and the polyethylene liner changed to LPS (NexGen LCCK femur size C, stem 12 × 100 mm, medial and lateral augments size 5mm, polyethylene size 14 LPS). However, pain, malalignment, and instability persisted.

Physical examination revealed a varus leg with varus thrust and lateral laxity of 5–10° in both extension and flexion, and limited knee hyperextension with flexion to 120°. There was no pathological medial or sagittal laxity, normal patellar tracking and no signs of malrotation. Radiographs revealed well-fixed components (Figure 1). Supplementary CT scan showed correct rotational placement of components. An EOS scan revealed coronal malposition of the tibial component with with mechanical tibiofemoral angulation of 9° varus (mechanical lateral distal femoral angle (mLDFA) = 91°, mechanical medial proximal tibial angle (mMPTA) = 82°) and a sagittal deformity of the tibia with posterior translation of the plateau and increased posterior slope (Figure 2).