Introduction: Traditional patient-reported outcome measures (PROMs) have failed to highlight differences in outcome when comparing knee replacement designs and implantation techniques. Wearable sensors, such as ankle-worn inertial measurement units (IMUs), can be used to remotely measure and monitor the bi-lateral impact load of patients, augmenting traditional PROMs with objective data. The aim of this study was to compare IMU-based outcomes with PROMs in patients who had undergone robotic total knee arthroplasty (RA-TKA) and conventional TKA (TKA) in the early post-operative period.
Methods: 50 patients undergoing primary knee arthroplasty (20 RA-TKA and 30 TKA) for osteoarthritis were prospectively enrolled. Remote patient monitoring was performed pre-operatively, then weekly from post-operative weeks two to six using bilateral ankle-worn IMUs and PROMs. IMU-based outcomes included: cumulative impact load, bone stimulus, and impact load asymmetry. PROMs scores included: Oxford Knee Score (OKS), EuroQol Five-dimension with EuroQol visual analogue scale, and the Forgotten Joint Score.
Results: Differences in IMU-based outcomes and PROMs were observed in the initial six weeks after surgery between RA-TKA and TKA. The mean change scores for OKS over the early post-operative period were 7.5 and 11.4 for RA-TKA and TKA, respectively (P=0.179). However, this did not always reflect the same trend as IMU-based impact loads between RA-TKA and TKA groups. Notably, improvements in OKS were consistent with IMU outcomes in the RA-TKA group, but the conventional TKA group did not reflect the same trend in improvement as OKS, demonstrating a functional decline from post-operative week three.
Conclusion: Our wearables show that there are differences in bi-lateral impact loads between patients who undergo RA-TKA and conventional TKA, which are overlooked by using PROMs alone.