Small deviations between planned and performed bone cuts using a CT-based robotic-arm-assisted total knee arthroplasty system.

PURPOSE: Computed tomography (CT)-based robotic system for total knee arthroplasty (TKA) has shown improved accuracy compared to conventional. This study was designed to (1) confirm the accuracy of the robotic system in achieving the plan and (2) establish the alignment and positioning deviation between final components and planning, by measuring the discrepancy between final implant alignment and the corresponding planned cut. METHODS: Ninety-six cementless robotic-arm assisted (RA) TKAs were assessed. Bone resections were performed using the haptically controlled robotic arm. Alignment in the coronal and sagittal plane and resection depth of the distal femoral and proximal tibial cuts were recorded with a navigation planar probe. After final components were impacted, the probe was positioned on each implant surface to determine its alignment and positioning. RESULTS: The mean tibial resections and implanted tibial component's positioning were 0.4 mm (standard deviation, SD: 0.6) and 0.9 mm (SD: 0.8), respectively, higher than planned (p < 0.01). The tibial sagittal cut had 19/96 cases (19.8%) of ±1° outliers from plan. In 40/96 cases (41.7%), the tibial component was more prominent than planned of more than 1 mm. The mean femoral resections and impacted femoral component's positioning was 0.1 mm (SD: 0.8) and 0.2 mm (SD: 0.7), respectively, higher than planned. In 23/96 cases (24.0%), the femoral sagittal cut and femoral component coronal alignment deviated more than ±1° from plan. CONCLUSIONS: The computed tomography-based robotic-assisted TKA system showed good accuracy regarding bone preparation and component's positioning relative to the planning. Cementless tibial component impaction resulted in the most deviation from plan, with a large proportion of cases resulting in being more prominent than planned. LEVEL OF EVIDENCE: Level III.

No difference in clinical outcomes between functionally aligned cruciate-retaining and posterior-stabilized robotic-assisted total knee arthroplasty.

PURPOSE: To compare the clinical outcomes of subjects undergoing primary robotic-assisted total knee arthroplasty (RA-TKA), following functional alignment (FA) principles, with cruciate-retaining (CR) or posterior-stabilized (PS) bearing designs, at a minimum of 24 months of follow-up. METHODS: This observational, retrospective study included 167 consecutive patients undergoing RA-TKA with cemented PS and cementless CR implants performed with a CT-base robotic-arm assisted system (Mako, Stryker), following FA principles, between 2017 and 2020. Patients were followed up with a clinical and radiographic assessment and were administered the Forgotten Joint Score-12 (FJS-12), Knee Injury and Osteoarthritis Outcome Score for Joint Replacement (KOOS-JR), and the 5-level Likert scale (5-LLS). RESULTS: Three TKA revisions were performed (2 PS, 1 CR); therefore, a total of 164 knees with a mean age of 71.7 years (SD 8.9) were considered (80 cemented PS; 84 cementless CR). No statistically significant differences were recorded between study groups relative to FJS-12, KOOS-JR, and 5-LLS at a minimum of two year follow-up (FJS-12 89.3 ± 9.2 vs 87.5 ± 12.8, p-value 0.46; KOOS-JR 88.8 ± 10.0 vs 86.7 ± 14.0, p-value 0.31; 5-LLS 4.5 ± 0.7 vs 4.5 ± 0.8, p-value 0.34). CONCLUSION: No significant outcome differences were reported between patients undergoing PS and CR RA-TKA at a minimum of two year follow-up. RA-TKA achieves excellent clinical results and high satisfaction scores, regardless of the implant design used.