Unicompartmental knee arthroplasty (UKA) is a bone-preserving treatment option for osteoarthritis localized to a single compartment in the knee. The success of the procedure is sensitive to patient selection and alignment errors. Robotic arm-assisted UKA provides technological assistance to intraoperative bony resection accuracy, which is thought to improve ligament balancing. This paper presents the five-year outcomes of a comparison between manual and robotically assisted UKAs. The trial design was a prospective, randomized, parallel, single-centre study comparing surgical alignment in patients undergoing UKA for the treatment of medial compartment osteoarthritis (ISRCTN77119437). Participants underwent surgery using either robotic arm-assisted surgery or conventional manual instrumentation. The primary outcome measure (surgical accuracy) has previously been reported, and, along with secondary outcomes, were collected at one-, two-, and five-year timepoints. Analysis of five-year results and longitudinal analysis for all timepoints was performed to compare the two groups.Aims
Methods
Recent advancements in optical navigated TKA have shown improved overall limb alignment, implant placement and reduced outliers compared to conventional TKA. This study represents the first RCT comparing EM navigation and conventional TKA. 3D alignment was analysed from CT scans. Clinical scores (Oxford Knee Score (OKS) and American Knee Society Score (AKSS)) were recorded at pre-op, 3 and 12 months post-op. Data presented includes 180 patients (n=90 per group) at 3 months and 140 (n=70 per group) at 12 months. The groups had similar mean mechanical axis alignments (EM 0.31° valgus; conventional 0.15° valgus). Mechanical axis alignment however was improved in the EM group with 92% within +/−3° of neutral compared to 84% of the conventional group (p=0.90). The EM group showed improved coronal and sagittal femoral alignment and improved coronal, sagittal and rotational tibial alignment, which was significant for sagittal femoral alignment (p=0.04). The OKS and AKSS scores were significantly better for the EM group at 3 months post-op (OKS p=0.02, AKSS p=0.04), but there was no difference between groups at 12 months. The mean pre-op range of motion (ROM) for both groups was 105°. This decreased at 3 months to 102° in the EM group and 99° in the conventional group, but there was a significant improvement by 12 months: EM=113° (p=0.012) and conventional=112° (p=0.026). ROM was statistically similar between groups at all assessment phases. 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 improvements at early follow-up; however this difference was not sustained at 12 months. ROM was seen to decrease at 3 months but then significantly improve by 12 month post-op. Proving cost-effectiveness for navigation systems in TKA remains a challenge.
