APPLICATION OF ROBOTIC ASSISTANCE IN PATIENTS WITH EXTRA-ARTICULAR KNEE DEFORMITY UNDERGOING TOTAL KNEE ARTHROPLASTY.

Abstract

Introduction

Extra-articular knee deformities, especially in the coronal plane of the femur or tibia, alter the mechanical axis of the limb, accelerating the progression of gonarthrosis and making total knee arthroplasty a more complex procedure to achieve proper joint alignment. In moderate to severe varus or valgus deformities, the conventional technique based on intra-articular resection may require extensive soft tissue releases or prostheses with a higher level of constriction to attempt to achieve adequate alignment.

The application of robotic assistance has demonstrated greater precision in bone cutting and component positioning, achieving alignments within ±3° of the planned mechanical axis and significantly reducing outliers compared to conventional techniques. Furthermore, it identifies dynamic deformities such as reverse coronal deformity, which describes a change from varus to valgus or vice versa between extension and flexion, in approximately 7.8% of patients, allowing for its precise intraoperative correction.

General Objective

To evaluate the effectiveness of robotic-assisted total knee arthroplasty in patients with extra-articular coronal deformities undergoing total knee arthroplasty, in terms of mechanical alignment accuracy, implant position, and improvement in clinical functional scales.

Methodology

This is an observational, longitudinal, retrospective study that will include patients with gonarthrosis who present with an extra-articular deformity of the femur or tibia and who underwent robotic-assisted total knee arthroplasty (ROSA Robot) at the National Institute of Rehabilitation in the joint reconstruction service between January 2023 and December 2024.

Results

This study aims to demonstrate that the application of robotic assistance in patients with extra-articular deformities results in the following findings:

Improved restoration of the postoperative mechanical axis, thanks to the three-dimensional planning and precision of the bone cuts guided by the robotic system.

Greater precision in the placement of prosthetic components, especially in anatomically complex situations due to extra-articular deformity.
Reduced need for additional procedures such as corrective osteotomies, as proper alignment is achieved without extra interventions.
Improved short- and medium-term functional outcomes, assessed using functional scales such as WOMAC.
A comparable or lower rate of surgical complications, such as instability, early loosening, or malrotation of components, compared to the conventional technique.

Conclusions

Robot-assisted surgery represents an effective and safe alternative for performing total knee arthroplasty in patients with extra-articular deformities in the coronal plane. The preliminary evidence and expected results of this study suggest that this surgical approach allows for more individualized planning, more precise execution, and better postoperative alignment—crucial factors in the success of total knee arthroplasty in patients with complex anatomy.

Furthermore, the possibility of avoiding additional procedures, improving component placement, and promoting intraoperative ligament balance can translate into better functional outcomes and a lower rate of revisions in the medium term.