Patellar tracking and patellar tilt in kinematic versus mechanical knees

This study aims to compare patellar tracking and tilt following kinematic and mechanical total knee arthroplasty (TKA) via comparison of the incidence of lateral release and the patellar tilt angle on the postoperative sunrise X-ray view.

A retrospective study was conducted identifying 252 patients who underwent TKA. Radiographic measurements were collected prior to and following TKA, including the mechanical distal femoral angle, proximal tibial angle, lateral joint line release, patellar tilt and patellar displacement prior to and following operation.

Of the 222 patients analysed, 119 patients underwent kinematic TKA (KA-TKA) and 103 patients underwent mechanical TKA (MA-TKA). Mechanically aligned knees were found to have a higher incidence of lateral joint line release (3.9% vs. 0%) (p = 0.04) and a greater incidence of patellar retinacular release (4.9% vs. 0.8%), although not significant (p = 0.10). There was no difference between kinematic and mechanical TKA regarding change in patellar tilt or patellar displacement prior to and following TKA.

Patellar tracking was found to be comparable between mechanical and kinematic TKA, with no significant difference in incidence of patellar release, patellar tilt or patellar displacement. Mechanically aligned TKA required a non-statistically significant increased incidence of lateral joint line release. Overall, these results support that MA-TKA and KA-TKA both result in satisfactory patellar tracking with possible reduced need for patellar and lateral joint line releases in KA-TKA.

Level III, clinical research.