This study aimed to compare the effect of an image-based (MAKO) system using a gap-balancing technique with an imageless (OMNIbot) robotic tool utilising a femur-first measured resection technique.
A retrospective cohort study was performed on patients undergoing primary TKA with a functional alignment philosophy performed by a single surgeon using either the MAKO or OMNIbot robotic systems. In all cases, the surgeon\'s goal was to create a balanced knee and correct sagittal deformity (eliminate any fixed flexion deformity). Intra-operative data and patient-reported outcomes (PROMS) were compared.
A total of 207 MAKO TKA and 298 OMNIbot TKAs were analysed. MAKO TKA patients were younger (67 vs 69, p=0.002) than OMNIbot patients. There were no other demographic or pre-operative alignment differences. Regarding implant positioning, in MAKO TKAs the femoral component was more externally rotated in relation to the posterior condylar axis (2.3° vs 0.1°, p<0.001), had less valgus femoral cuts (1.6° vs 2.7° valgus, p<0.001) and more varus tibial cuts (2.4° vs 1.9° varus, p<0.001), and had more bone resected compared to OMNIbot TKAs. OMNIbot cases were more likely to require tibial re-cuts than MAKO (15% vs 2%, p<0.001). There were no differences in femur recut rates, soft tissue releases, or rate of achieving target coronal and sagittal leg alignment between robotic systems. A subgroup analysis of 100 MAKO and 100 OMNIbot propensity-matched TKAs with 12-month follow-up showed no significant difference in OKS (42 vs 43, p=0.7) or OKS PASS scores (83% vs 91%, p=0.1). MAKO TKAs reported significantly better symptoms according to their KOOS symptoms score than patients that had OMNIbot TKAs (87 vs 82, p=0.02) with a higher proportion of KOOS PASS rates, at a slightly longer follow-up time (20 months vs 14 months, p<0.001). There were no other differences in PROMS.
A gap-balanced technique with an image-based robotic system (MAKO) results in different implant positioning and bone resection and reduces tibial recuts compared to a femur-first measured resection technique with an imageless robotic system (OMNIbot). Both systems achieve equal coronal and sagittal deformity correction and good patient outcomes at short-term follow-ups irrespective of these differences.

BACKGROUND: Technology that enables the orthopaedic surgeon to deliver a surgical plan with precision and reproducibility continues to evolve. Robotic TKA represents the next phase of technological development in knee arthroplasty. Multiple propriety robotic platforms are now available for use in TKA, and one such system is the OMNIBotics platform. We conducted a review of this system, reporting its history and principles of use, published outcomes and our own personal experience performing OMNI robotic-assisted TKAs.
METHODS: A literature review was conducted using the PRISMA guidelines. Thirteen papers were included for the final review.
RESULTS: The OMNIBot is an accurate and consistent delivery tool in TKA surgery and compares favourably to instrumented, navigation-assisted and patient-specific cutting guides. The OMNIBot has been shown to be a reliable tool for delivering different alignment philosophies as well as planning and achieving tibio-femoral coronal balancing. The utility of the system is increased when the robot is used in conjunction with a soft-tissue tensioning device-the BalanceBot. Data regarding PROM\'s are limited, however results to date show reliable outcomes. Survival analysis of RATKA using the OMNIBot is limited to one study which reported 99.26% survivorship at 3 years. We report our own outcomes using the OMNIBot, having performed 766 TKA\'s using the OMNIBot, since 2014 with 99.48% survivorship at 6 year follow-up.
CONCLUSIONS: The OMNIBot platform is an imageless, passive robotic system available since 2007, with over 30,000 TKA\'s being performed with its assistance. It has a small physical footprint, is relatively inexpensive and time efficient. Our review demonstrates a high level of precision of the surgical planning, with a modestly improved accuracy compared to conventional and navigation technology. Published outcomes are limited, however demonstrate good short-term PROM\'s and survivorship data that compare favourably to other robotic TKA cohorts.