DeClaire LaMacchia Orthopaedic Institute

Achieving a balanced knee is a critical aspect of Total Knee Arthroplasty (TKA). Coronal and axial boundaries for femoral component placement to achieve balance however, are not well defined. Our aim is to investigate the effect of femoral component and long leg coronal and axial alignment on patient outcomes when using a tibia-first gap balancing technique.All surgeries were performed using the OMNIBotics robot-assisted TKA platform and BalanceBot device. A total of 197 patients were prospectively enrolled into this study and received TKA surgery using the OMNIBotics platform and completed 1-year KOOS outcome scores. Femoral component and tibiofemoral alignment were categorized as inliers or outliers in the coronal and axial planes. Knee Injury and Osteoarthritis Outcome Score (KOOS), and University of California at Los Angeles Activity Scale (UCLA) was collected at 1-year post-op.No significant differences were found between the KOOS subscores or UCLA outcome and femoral coronal or tibiofemoral coronal and axial alignment. Significant differences were found between the KOOS pain and sports sub-scores and femoral axial alignment (∆ = 5.4, p = 0.007, ∆ = 8.3, p = 0.03 respectively), in which outlier femoral rotation reported higher scores.Component alignment limits for improved survival and patient outcomes are a source of ongoing debate. The data presented here indicates that when utilizing a tibia-first gap balancing technique, small deviations outside of traditional ±3°alignment boundaries did not negatively affect KOOS or UCLA outcomes, indicating balance may have a stronger link to patient outcome than alignment.

Joint balance in total knee arthroplasty (TKA) has traditionally focused on achieving a tight symmetric extension gap and rectangular or trapezoidal gaps in flexion. This study sought to investigate the effect of femoral and tibial coronal rotation and femoral axial rotation on midflexion coronal joint balance and patient outcomes.A prospective multi-center study was performed with a mixture of tibia-first gap-balancing and femur-first approaches were performed using the Corin OMNIBotics robot-assisted TKA platform with APEX implant components. Coronal and axial femoral and tibial resections were recorded by the platform. Medial and lateral joint gaps were recorded while applying a computer-controlled load to the joint throughout flexion during trialing using the Corin BalanceBot device. In addition, 1-year Knee Injury and Osteoarthritis Outcome Score (KOOS) and PROMIS-10 global health scores were collected.231 surgeries were identified: 66.9±8.1 years, 31.4±4.8 kg/m2 and 57% female (121) with a mean pre-operative HKA angle of 4.5±5.2° varus. A significant correlation was found between the medio-lateral (ML) joint gap difference in midflexion and both extension and flexion joint line (p=0.003, r2=-0.20, p=0.001, r2=-0.22, respectively). A significant correlation was found between midflexion ML imbalance and KOOS stiffness questions at 3 M and 6 M post-op (r2=-0.15, p=0.036, r2=-0.18, p=0.013), in which a more balanced knee correlated with improved outcomes.Treating flexion and extension joint balance in isolation may not capture the effect on midflexion laxity. Component placement should take in to account the effect on joint gaps throughout flexion to target optimal joint balance.

This study reports on the one-year clinical results and patient reported outcomes (PROMs) associated with a new ‘predictive balance’ tibia-cut first total knee arthroplasty (TKA) technique that uses a robotic ligament tensioner. PROMs are compared to registry data and historical results in the literature.Five hundred and thirty-three patients were prospectively enrolled and underwent robotic TKA (mean age: 67.7±8.4; females: 320; BMI: 31.2±4.9). Pre-op, three, six and 12-month WOMAC, UCLA activity scale, and HSS-Patient satisfaction assessments were completed by 533, 352, 314, and 256 patients, respectively, and compared to WOMAC registry data from the Shared Ortech Aggregated Repository (SOAR) and to historical satisfaction reports in the literature.Despite having equivalent baseline PROM scores, predictive balance patients had significantly higher WOMAC scores at all post-operative timepoints (p<0.001) and higher UCLA activity scale scores at 3M and 6M (p<0.013). Overall patient satisfaction in the predictive balance cohort was 91.2%, 92.4%, and 96.5% at 3M, 6M and 1YR, respectively. Average length of stay was 1.6 days (±0.8). Surgical complications in this cohort were typical of TKA.Limitations to this study include the lack of a closely matched control group. Nonetheless, first year results are promising with improved objective measures compared to large registry databases and recently reported patient satisfaction measures.