Summary

This study evaluates the effectiveness of different corrective sequences in robotic-assisted total knee arthroplasty for addressing fixed flexion contracture, finding that sequential distal femoral resections are more effective than posterior cruciate ligament excision, and that posterior capsule release resolves the contracture in over one-third of cases.

Abstract

Introduction

Total Knee Arthroplasty (TKA) is an effective treatment for gonarthrosis; however, a significant percentage of patients report dissatisfaction, and over 6% will require revision surgery within the first five years. Fixed flexion contracture (FFC) is a common complication in advanced knee osteoarthritis and can significantly impact TKA outcomes. While robotic-assisted TKA, such as the MAKO® system, enhances surgical precision, the optimal sequence of corrective actions to achieve full knee extension remains debated. This study aims to evaluate the effectiveness of different corrective sequences in robotic-assisted TKA for addressing fixed flexion contracture and achieving optimal postoperative knee extension.

Materials And Methods

This study involved 29 knee replacements on 15 fresh cadavers, excluding one knee due to a prior Girdlestone procedure. Two groups were formed based on laterality, 15 knees were right-sided and 14 left-sided. Each TKA was performed using the MAKO® robotic system, guided by a preoperative CT scan, and utilized the Triathlon® cruciate-retaining total knee prosthesis. Two experienced surgeons performed the surgeries using a medial parapatellar approach, initially preserving the posterior cruciate ligament (PCL ).
For knees with residual FFC, a corrective algorithm was applied, starting with posterior capsule release in both right and left knees. If FFC persisted, the sequence diverged: for right knees, PCL excision was performed, followed by sequential 1mm distal femoral resections up to 4mm; for left knees, the order was reversed. The degree of FFC was recorded after each corrective measure, and medial and lateral laxities were assessed to evaluate the impact on TKA stability.

Results

Out of the 29 knees studied, flexion contracture was observed in 19, with a mean contracture of 6.6° ± 4.9°. The posterior capsule release alone corrected the contracture in 36.8% of cases, with an average extension gain of 1.68° ± 1.11°. The second corrective action for right knees, PCL excision, improved extension by a mean of 1.1°, but none achieved full extension. In contrast, the second action for left knees, 1mm distal femoral resections, resulted in an average extension gain of 4.3° ± 0.6°. The difference in extension gain between PCL excision and distal femoral resection was statistically significant (p = 0.002).
The corrective algorithm applied to left knees was more efficient, with an average of 2.33 steps required to achieve full extension, compared to 4.25 steps for right knees.

Conclusions

The study concludes that posterior capsule release can resolve FFC in over one-third of cases. Sequential distal femoral resections offer significantly greater correction of flexion contractures than PCL excision. The corrective algorithm applied to left knees proved more efficient. Robotic assistance is valuable in enhancing the precision and effectiveness of FFC correction.