gms | German Medical Science

Objectives: Although recent studies have shown different tibiofemoral kinematics between cruciate-ligament retaining (CR-TKA) and cruciate-ligament substituting total knee arthroplasty (CS-TKA)and also suggest a possible influence of different types of total knee arthroplasty on patellar kinematics and the appearance of anterior knee pain, the influence CR-TKA and CS-TKA on patellar kinematics is unclear so far. The aim of this study was to compare patellar kinematics after CR and CS-TKA of the same manufacturer. The hypothesis that there is a significant difference in patellar kinematics between both types of TKA was tested.

Methods: Patellar kinematics of nine cadaveric knees before and after CR-TKA and CS-TKA was investigated using a commercial optical computer navigation system with an additional patella array during passive motion on a passive motion machine between 0° and 90° of flexion. Patellar kinematics were analysed using patellar mediolateral shift, tilt, rotation and epicondylar distance (distance between transepicondylar line and the patella). The student's t-test for paired samples and the Wilcoxon signed-rank test for not normally distributed data was used to determine statistical significance. A p-value of <0.05 was considered to indicate statistical significance. The study had the power to detect a difference of 0.7-1.5 mm and 1.5°-4° between the natural knee and the TKAs and to detect a difference of 0.5-1.0 mm and 2.5°-3.5° between the two types of TKAs.

Results and Conclusion: No significant difference between the natural knee and knees after TKA as well as between both types of TKA could be found. Although, the patellae of the TKAs shifted more medially compared to the natural knee. The CR-TKAs showed a contrary patellar tilt behaviour compared to the CS-TKAs in higher and more externally rotated patellae in early flexion angles.

In summary, no significant difference in patellar kinematics between CR- and the CS-TKA could be found. Individual component alignment seems to be of higher importance to restore patellar kinematics in TKA than whether to choose a CR- or a CS-TKA.