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Background: We have conducted a prospective cohort study with the aim of comparing operative time, intraoperative blood loss, and radiologic and clinical outcomes between imageless (NAVIO) and image-based (MAKO) robot-assisted unicompartmental knee arthroplasty (UKA) for medial compartment osteoarthritis (OA) of the knee. Methods: A total of 33 patients with medial compartment OA of the knee were prospectively allocated on alternate operative days of their surgery to MAKO (16 patients) or NAVIO (17 patients) robot-assisted UKA. The primary outcome (Knee Society Score [KSS] and Knee Functional Score [KFS]) and the secondary outcomes (intraoperative time of seven steps [registration of hip and ankle, femur and tibia, ligament tension, implant planning, preparation femur, tibia and trial implant], component alignment [coronal and sagittal of femur, tibia implant], blood loss, complications, and revision at 1 year after surgery) were compared between two groups. Statistical significance was set at P < 0.05. Results: Mean KSS measured at baseline and 1 year were, respectively, 70.3 (5.6) and 96.9 (5.7) in the NAVIO group and 72.3 (4.5) and 94.7 (10.01) in the MAKO group. Mean KFS measured at baseline and 1 year were, respectively, 95.5 (7.9) and 99.9 (0.25) in the NAVIO group and 67.3 (7.8) and 99.5 (1.2) in the MAKO group. There were no significant differences for KFS and KSS outcomes (P = 0.203 and P = 0.457, respectively) between the NAVIO and MAKO groups. Mean operative time and blood loss in the NAVIO versus MAKO robot-assisted UKA groups were 98 min versus 82.5 min and 136.3 ml versus 80 ml, respectively, and these differences were statistically significant. In the MAKO group, the intraoperative time was statistically significantly shorter in registration of hip and ankle center, femur and tibia, femur preparation, and trial implantation compared with the NAVIO group. There were no significant differences of component alignment and radiologic alignment at 1 year between the two groups. No perioperative or delayed complications (infection, periprosthetic fracture, thromboembolism, and compromised wound healing) and revisions were reported in either group. Conclusions: This study demonstrated that two robotic systems showed no difference in clinical outcomes at 1 year and radiologic alignment of implants, whereas operative time and intraoperative blood loss were found to be less in MAKO robot-assisted UKA. Trial registration: ClinicalTrials.gov, NCT03954912. Registered on 17 May 2019.

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INTRODUCTIONThe outcome of knee replacement depended on alignment, balancing of soft tissue, symmetrical andrectangular gaps adjustment, and accurate implant placement. Many techniques have been used toimprove these factors including navigator assisted knee replacement, which has precise bone cutand accurate soft tissue balancing. However, cementation may change gaps and alignment that canaffect outcome of knee replacement.OBJECTIVETo compare gaps and alignment after cementation in computer assisted total knee replacementMATERIAL AND METHODSProspective collecting data all cases performed computer assisted total knee replacement withcruciate retaining - mobile bearing implant design. Gaps and mechanical axis was collected andcompered between complete trial prosthesis and final cementation.RESULTLateral extension gap and flexion contracture significantly increase after cementation whencompared with trial implantation [0.6 mm (P = 0.021), 2.7o (P = 0.00)]. The mechanical axis was notdeviated after cementation (P = 1.00).CONCLUSIONCementation is able to influence gap and alignment. It may be useful to control and recheck gap andalignment with navigation system during cementation. Clinical correlation needs furtherinvestigation.

Introduction: The aim of this study was to evaluate the reliability of the femoral component rotation on intra-operative data recorded in a computer-assisted navigation system (CAN-FRA) compared with the post-operative femoral component rotation observed on computed tomography (CT-FRA). Material and method: Computer-assisted total knee arthroplasty (TKA) or primary osteoarthritis of the knee was performed in 51 knees in 36 patients with a mean age of 69.51 years. All procedures were performed by a single surgeon using the same implant design. The intraclass correlation coefficient (ICC) was used to compare the intra-operative CAN-FRA with the post-operative CT-FRA. The angle between the anatomical epicondylar axis and the posterior condylar axis of the implant (CT-FRA) was measured at two separate timepoints by three observers who were blinded to the intra-operative CAN-FRA. Internal rotation was defined as rotation in the negative direction, while external rotation was defined as positive. Results: The mean intra-operative CAN-FRA was 0.1° ± 2.8° (range -5.0° to 5.5°). The mean post-operative CT-FRA was -1.3° ± 2.1° (range -4.6° to 4.4°). The mean difference between the CAN-FRA and the CT-FRA was -1.3° ± 2.2° (range -7.9° to 2.4°). The respective ICC values for the three observers were 0.92, 0.94, and 0.93, while the respective intra-observer coefficients were 0.91, 0.85, and 0.90. The ICC for the intra-operative CAN-FRA versus the post-operative CT-FRA was 0.71. Conclusion: This study shows that using a computer-assisted navigation system in TKA achieves reliable results and helps to achieve optimal positioning of the femoral component and rotation alignment correction.