Does the tibia component design affect the need for offset stems in revision total knee arthroplasty?

Abstract

The stem/keel location varies between anatomic and symmetric revision tibial baseplates. The current study investigates the impact of an anatomic versus symmetric stem location on the need for offset couplers in revision total knee arthroplasty. Hip to ankle standing radiographs and lateral radiographs of 75 patients were analyzed using digital templating software. The offset in the anterior-posterior as well as medial-lateral plane between the center of the tibial diaphysis and the stem of the tibial baseplate were determined for an anatomic and symmetric tibial baseplate, respectively. Measurements were repeated for 4 resection levels: tip of fibular head (0), 10mm (1), 15mm (2) and 20mm (3) below the tip of the fibula head. Anatomic tibial baseplates require less offset for resection levels up to the tip of the fibula: total offset 2.28 versus 5.44mm (p < 0.001). However, for defects that result in resection levels below the tip of the fibula symmetric tibial baseplates require less offset: resection level 1: 3.18 versus 2.4mm (p = 0.008), 2: 4.81 versus 1.67mm (p < 0.001) and resection level 3: 5.66 versus 1.52mm (P < 0.001). The current study suggests that while asymmetric anatomic tibial baseplates have benefits for revisions with minimal bone loss, symmetric tibial baseplates require less offset when larger bone defects are encountered.