Summary

The aim of this prospective observational cohort study was to evaluate early functional outcomes of patients who have undergone robotic-assisted TKA compared with conventional TKA using wearable sensors and traditional PROMs.

Abstract

Introduction

Robotic-assisted total knee arthroplasty (RA-TKA) has demonstrated significant benefits, including improved accuracy of component positioning compared to conventional jig-based TKA. However, previous studies have often failed to associate these findings with clinically significant improvements in patient-reported outcome measures (PROMs). Inertial measurement units (IMUs) provide a more nuanced assessment of a patient's functional recovery after TKA. The purpose of this study was to evaluate early outcomes of patients that underwent RA-TKA and conventional TKA using wearable IMU sensors and traditional PROMs.

Methods

This was a prospective, matched, parallel cohort study of 100 patients with symptomatic end-stage knee osteoarthritis undergoing primary TKA (44 RA-TKA, 56 conventional TKA). Functional outcomes were assessed using ankle-worn inertial measurement units (IMUs). IMU-based outcomes included impact load, impact asymmetry, maximum knee flexion angle, and bone stimulus. PROMs, including Oxford Knee Score, EuroQol-Five Dimension, EuroQol Visual Analogue Scale, and Forgotten Joint Score, were evaluated at pre-operative baseline, weeks 2 to 6 post-operatively, and at 3-months and 1-year follow-up.

Results

By post-operative week 6, RA-TKA patients showed improved function compared to the conventional TKA group, with increased maximum knee flexion angle (118o ± 6.6o vs 113o ± 5.4o; p=0.04), improved symmetry in regard to limb loading (82.3% vs 22.4%; p<0.01), increased cumulative impact load (146.6% vs 37%; p<0.01), and increased bone stimulus (25.1% vs 13.6%; p<0.01). RA-TKA patients demonstrated an earlier return to symmetrical limb loading compared to conventional TKA by post-operative week 3. There were no differences in PROMs between the two groups at any timepoint.

Conclusions

RA-TKAs were associated with faster return of normal gait and improved range of motion when assessed using IMUs compared to conventional TKA, which were not detected by traditional PROMs during the early post-operative period. Ankle-worn wearable IMUs have the potential to quantify significant differences, which may be overlooked by traditional PROMs, among emerging RA-TKA platforms and alignment strategies in future studies. Future research with more robust methodology and longer follow-up is warranted to address whether subtle differences detected with wearable IMU sensors are clinically meaningful.