Component alignment and functional outcome following computer assisted and jig based total knee arthroplasty

Incorrect positioning of the implant and improper alignment of the limb following total knee arthroplasty (TKA) can lead to rapid implant wear, loosening, and suboptimal function. Studies suggest that alignment errors of > 3° are associated with rapid failure and less satisfactory function. Computer navigated systems have been developed to enhance precision in instrumentation during surgery. The aim of the study was to compare component alignment following computer assisted surgery (CAS) and jig based TKA as well as functional outcome.

This is a prospective study of 100 knees to compare computer-assisted TKA and jig-based surgery in relation to femoral and tibial component alignment and functional outcome. The postoperative x-rays (anteroposterior and lateral) of the knee and CT scanogram from hip to foot were obtained. The coronal alignment of the femoral and tibial components and rotational alignment of femoral component was calculated. Knee society score at 24 months was used to assess the function.

Results of our study show that mean placement of the tibial component in coronal plane (91.3037°) and sagittal planes (3.6058°) was significantly better with CAS. The difference was statistically insignificant in case of mean coronal alignment of the femoral components (90.34210° in navigation group and 90.5444° in jig group) and in case of the mean femoral condylar twist angle (external rotation 2.3406° in navigation group versus 2.3593° in jig group).

A significantly improved placement of the component was found in the coronal and sagittal planes of the tibial component by CAS. The placement of the components in the other planes was comparable with the values recorded in the jig-based surgery group. Functional outcome was not significantly different.