Three-Dimensional Finite Analysis of the Optimal Alignment of the Tibial Implant in Unicompartmental Knee Arthroplasty.

Abstract

Although unicompartmental knee arthroplasty (UKA) has become more common because of its good outcomes, several complications have been reported. Tibial implant alignment, an important cause of such complications, has been investigated; however, the optimal alignment of the tibial implant has not been determined. This study used 3-dimensional finite element analysis to investigate changes in stress distribution in the proximal tibia after UKA at multiple tibial implant alignments. A 3-dimensional finite element model was created with CT digital imaging and communications in medicine (CT-DICOM) data from a medial osteoarthritic knee. Change in stress distribution of the tibial implant alignment on the coronal plane (middle position, varus 5°, valgus 5°) and sagittal plane (0°, 5°, 10°) under conditions of a loose boundary between implant and bone and no loosening was analyzed with 3-dimensional finite analysis. In the absence of loosening, the stress distribution was high at the lateral rim of the subchondral bone in the varus alignment model, and the high stress distribution moved from the anterior to the posterior position with posterior tilting from 0° to 10°. With loosening, the stress distribution was high at the proximal tibial medial cortex in the valgus alignment model. To reduce UKA complications, the present findings indicate that the optimal alignment of the tibial implant is at the middle position on the coronal plane, with a posterior inclination similar to the original inclination on the sagittal plane.