Relationship between femoral component placement and patient-specific anatomical rotational landmarks in robotic arm...

Osteoarthritis of the knee is a common problem in the elderly, leading to severe morbidity. Total Knee Arthroplasty (TKA) is a widely validated surgery to provide a remarkable extent of knee function and simultaneously alleviates pain for knee osteoarthritis (OA). It is clearly understood that precision of the rotational alignment and accuracy of the technique in the placement of the femoral component is a prerequisite for excellent and successful outcomes of TKA. Advanced technology has now allowed surgeons to understand patient-specific variabilities in anatomical reference landmarks and the relationship of component positioning in relation to the reference landmarks to achieve accurate gap balancing with minimal soft tissue release.¹⁴ Robotic Arm Assisted-Total Knee Arthroplasty (RAA-TKA) is a semi-automated system that enables us in replicating the same. Using this technology, the bony resections, component positions, probable component sizing and gap balancing can be tentatively planned preoperatively with CT Scan Analysis and executed intraoperatively. Hence this study was undertaken to estimate the relationship between femoral component placement to normal rotational landmarks such as the Posterior Condylar Axis (PCA) and to quantitatively evaluate coronal and sagittal plane correction obtained. Also, we aimed to use the data to detect any anatomical variations in the study population and evaluate the accuracy of predicted component sizing, including gender-based evaluation.

A Prospective Observational Study of 1073 knees of patients of either sex above 50 years of age with Kellgren Lawrence Grade 4 Osteoarthritis of the knee which were confirmed with X-Ray undergoing RAA-TKA using MAKO Robotic System using Stryker Triathlon (Cruciate Substituting) CS Knee was conducted during the period between 2022 and 2023 in two South Indian hospitals specializing in joint replacement surgeries.

We found a statistically significant difference between the native Posterior Condylar Axis (PCA) (4.82 ± 2.15°) and final femoral component external rotation (3.24 ± 1.29°) with a p-value of <0.001 at 95% confidence interval. The accuracy of component size prediction was 99.8%. Also, analysis in our study has shown the most common implant sizes to be 4 in males and 2 in females. We also found no statistically significant difference based on age, size, laterality, or primary varus deformity.

RAA-TKA provides patient-specific alignment/restricted kinematic alignment which might further enhance the outcome for the patient. Reliable deformity correction in coronal and sagittal planes can be achieved. Accurate flexion and extension gap balancing can be done through component placement and with minimal soft tissue dissection. Irrespective of all the advantages noted in RAA-TKA, further follow-up and long-term outcome studies are required to properly gauge and analyze this new technology.