Summary

Kinematically aligned total knee arthroplasty (KA-TKA) had greater knee joint moments in the coronal plane when performing sit-to-stand and squatting when compared to mechanically aligned total knee arthroplasty (MA-TKA), but does not lead to poorer clinical outcomes and patient satisfaction.

Abstract

Introduction

The impact of kinematic aligned total knee arthroplasties (KA-TKA) on the lower limb kinematics while performing simple activities of daily living (ADL) such as sit-to-stand and squatting are not well investigated especially in staged bilateral TKA. This study aims to contribute to the literature by comparing the lower limb kinematics for patients who have undergone staged bilateral TKA with one knee being mechanically aligned TKA (MA-TKA) and contralateral knee being KA-TKA. We hypothesize that there will be significant differences in lower limb kinematics between MA-TKA and KA-TKA.

Method

This is a retrospective study of prospectively collected data for 13 patients who have undergone bilateral TKA at a single tertiary institution from 2009 to 2017. All patients had MA-TKA followed by KA-TKA with mean interval of 3.3 years. Pre- and post-operative clinical outcome scores were evaluated. The hip, knee and ankle joint angles, moments and ground reaction force (GRF) were measured using an optical motion capture (MOCAP) system with 10 cameras. Statistical analysis was carried out using paired t-test and p-value less than 0.05 was considered statistically significant.

Results

Sit-to-Stand
In the coronal plane, joint angles were similar. KA-TKA exhibited more hip joint moment at 75 percent of task (P=.02) and more knee joint moment throughout task – at maximum knee moment (P=.009), 25 percent of task (P=.012), midway through task (P=.004) and 75 percent of task (P=.003). In the sagittal plane, joint angles at the hip, knee and ankle were similar. MA-TKA had significantly less ankle joint moments midway through task (P=.04) and at 75 percent of task (P=.018). In the transverse plane, joint moments were found to be comparatively similar except for hip joint. KA-TKA had significantly more hip joint moment midway through task (P=.014) and at 75 percent of task (P=.009).

Squatting
In the coronal plane, joint angles were similar throughout the task. Joint moments were similar except for knee joint. KA-TKA showed more significant knee joint moment at maximum knee moment (P=.025), midway through task (P=.048), 75 percent of task (P=.05) and at deepest flexion (P=.039). In the sagittal plane, joint angles in the hip, knee and ankle were comparable. KA-TKA had significantly less knee joint moment at maximum knee moment (P=.008), midway through task (P=.013), 75 percent of task (P=.03) and at deepest flexion (P=.012). In the transverse plane, joint moments were largely similar throughout the task except for the hip joint. KA-TKA had significantly greater hip joint angles at 25 percent of the task (P=.031), midway through task (P=.03) and 75 percent through task (P=.047).


Radiological analysis, clinical outcome and satisfaction scores
The mean hip-knee-angle for KA-TKA was 1 degree (varus) and MA-TKA was 1.4 degree (valgus). There were no significant differences in the degree of improvement between preoperative and postoperative clinical outcome and similar satisfaction rates were obtained between MA-TKA and KA-TKA.

Conclusion

KA-TKA resulted in significantly greater coronal plane knee joint moments for simple ADL (sit-to-stand and squatting) but this does not affect clinical outcome and satisfaction scores when compared to MA-TKA.