Abstract
This RCT compared electromagnetic (EM) navigated and conventional total knee arthroplasty (TKA) in terms of clinical and functional outcomes. 200 patients (navigated=102, conventional=98) were recruited. Oxford Knee Scores (OKS) and the American Knee Society Score (AKSS) were recorded pre operation, 3 and 12 months after surgery. Post operative (coronal, sagittal and rotational) alignment was analysed from 3D CT scans taken 3 months after surgery. An objective functional assessment was completed using electrogoniometry on a sub group (navigated=60, conventional=57) at 12 months post surgery.
The EM group showed statistically significantly improved OKS (p=0.04) and AKSS (p=0.03) scores at 3 months post operation. However at 12 months post surgery there was no difference between the two groups. At the 1 year follow up it was reported that 9% of the navigated compared to 14% of the conventional group were dissatisfied with their surgical outcome.
The mechanical axis alignment of 90% of the navigated group was within 3 degrees of neutral compared to 84% of the conventional group. Although all alignment parameters except for tibial rotation was improved in the navigated group they did not reach significance apart from femoral slope alignment (p=0.01).
There was no statistically difference between the surgical groups in terms of the maximum, minimum and excursion knee joint angles during 12 functional activities. Only the knee kinematic function cycles for level walking resulted in statistically significant higher knee joint angles during 55–70% of the gait cycle in the navigated group.
Knee alignment was better restored following EM navigated TKA relative to conventional TKA, but the difference was not significant. The EM group showed greater clinical and functional improvements at early follow-up; however this difference was not sustained at 12 months. The EM group reported minimal gait improvements. Proving cost-effectiveness for navigation systems in TKA remains a challenge.
