Abstract
Introduction:
Unicompartmental knee arthroplasty (UKA) has been proven to be an effective treatment for degenerative joint disease confined to a single tibiofemoral compartment. Recently, UKAs have been performed with robotic-arm assistance (RAA) devices to build and improve upon previous computer-assisted navigation. As a pilot study, we have analyzed short term outcomes for a series of robotic-arm assisted medial UKAs and compared them to a comparable cohort of traditionally instrumented medial UKAs.
Methods:
Ninety-eight fixed-bearing medial UKAs were isolated in our prospective data collection database for short-term analysis for this study. Included patients completed pre and post-operative Short Form 12 version 1 Health Survey (SF12), Western Ontario and McMaster University Outcome Scores (WOMAC), and Knee Society Function Score (KSFS) questionnaires. Forty-eight RAA UKAs were performed using the MAKO RIO system with Restoris implants, and fifty manual UKAs were performed with the Zimmer® Unicompartmental High-Flex Knee System (ZUK).
Results:
Both cohorts experienced increased gains in all categories, except for the change in SF12 mental subscore in the MAKO cohort. Only the WOMAC pain subscore at 1 year showed statistically significant differences between the two cohorts, with MAKO subjects experiencing less pain than ZUK subjects (92.4 MAKO vs. 82.0 ZUK, p = 0.03). The SF12 mental score at three months and the change in SF12 mental score from pre-op to 1 year were also statistically significant; however, the pre-op differences between the two groups in the SF 12 mental category were also significantly different. Within the groups that were not significantly different, ZUK subjects experienced greater changes from pre-operative to three months in SF12 mental, all WOMAC subsets, and KSFS, while MAKO subjects had a greater change in SF12 physical subscore. This pattern held true with changes between pre-operative and 1 year, with the exception that MAKO patients experienced a greater positive change in WOMAC pain scores than ZUK patients. Additionally, age and body mass index were not significantly different between cohorts; however, operative time was significantly longer in the MAKO cohort (p < 0.001).
Discussion:
These results suggest that despite the lower WOMAC pain scores at one year, the extra expense and operative time required for RAA UKA may not translate into immediate functional gains. These conclusions are however limited due to the short follow-up time period and the randomization of patients. Future studies must also analyze implant alignment, rotation and position in order to fully analyze the operations.
