Soft Tissue Safety In Robotic-Assisted Total Knee Arthroplasty: Is It Reliable?

Soft Tissue Safety In Robotic-Assisted Total Knee Arthroplasty: Is It Reliable?

Eric Camprubí, MD, SPAIN Juan Ignacio Erquicia, MD, PhD, SPAIN Berta Gasol Cudos, MD, SPAIN Albert Pons Riverola, MD, SPAIN Angela Zumel, PhD, SPAIN Joan Leal-Blanquet, MD, PhD, SPAIN

Hospital Althaia, Manresa, Barcelona, SPAIN


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Anatomic Location

Diagnosis / Condition

Treatment / Technique

Diagnosis Method


Summary: This study evaluates the effects of expanding safety boundaries in robotic-assisted total knee arthroplasty using the MAKO® system on 29 cadaveric knees. Soft tissue injuries, particularly in the posterior compartment, were observed, with a 68.9% injury rate. Despite the increased damage from expanded margins, there was no correlation between soft tissue injuries and final knee stability.


Introduction

Total Knee Replacement is the gold standard treatment for severe osteoarthritis, with an 80% patient satisfaction rate. Soft tissue injuries can occur during procedure generating instability and may reduce implant longevity. Robotic-assisted surgery enhances precision and minimizes complications, such as the MAKO® Robotic System. This semi-active robot aids in surgical cutting, however there are safety boundaries that may need to be expanded depending on the patient's morphology. The aim of this study is to describe and quantify the soft tissue injuries and instability caused by the increasing boundaries.

Material And Methods

The study involved 29 cadaveric knees. A preoperative CT scan was conducted to match the knee's three dimensions during surgery, required using MAKO® robotic system. An expert surgeon performed the prosthetic surgery. After completing the bone cuts, the robot´s safety margins were expanded at the tibial cut level. The tibial cut was then re-executed to its limits in all directions, and knee stability was reassessed. Soft tissue lesions were evaluated by two surgeons and two anatomy professors using the MASTI classifications to quantify structural damage to the knee. Additionally, the anatomists measured the distance from the tibial bone margin to the injured structures. The MASTI classification scores range from 0 (complete detachment) to 10 (uninvolved tissue) across four compartments: anterior, medial, lateral, and posterior. Each knee could score between 0 and 40 points. Statistical analysis included descriptive methods, and T-student, Kruskal-Wallis, and U-Mann-Whitney tests were performed for comparison of the variables. Intraclass correlation explored the agreement between the two observers' measurements, and Pearson correlation was used for other continuous variables.

Results

67% of the hemibodies were male, with a mean age of 77.2±13.1 years. The average MASTI score was 33.38 ± 4.45. A higher percentage of injuries were observed in the posterior compartment (68.9%) compared to the lateral (41.4%) and medial (37.9%) compartments. The correlation of MASTI scores between surgeons and anatomists was moderate (rho = 0.47). Soft tissue cleavage injuries, classified as the second most severe category, occurred in 6.9% of the medial and lateral compartments, and in 24.1% of the posterior compartment. Severe damage in the posterior compartment was identified in only one case (complete detachment). The percentages of undamaged compartments were 62.1% for medial, 58.6% for lateral, and 31% for posterior. The mean MASTI scores by compartment were similar in the medial (8.37) and lateral (8.34) compartments, but lower in the posterior (6.65). The mean lesion size was largest in the medial compartment (11.90 mm), followed by the lateral (9.41 mm) and posterior (8.78 mm) compartments, with a high correlation between observers (rho = 0.99, p < 0.0001). The average distance from the bone margin to the injured structure in the posterior compartment was 10.86 mm. No correlation was observed between soft tissue damage and final knee stability.

Conclusions

Expanding boundaries during robotic-assisted total knee arthroplasty results in a high percentage of soft tissue damage, predominantly affecting the posterior compartment. However, this damage was not correlated with final knee stability.