Intramuscular tendon length in agonist–antagonist myoneural interface components in transtibial amputation: An anatomic study

Understanding the role of tendons in muscle function and proprioception is crucial for enhancing amputation surgery. Muscle spindles and Golgi tendon organs provide essential feedback for muscle control. Preservation of tendon function in amputation surgery and the development of the agonist-antagonist myoneural interface (AMI) have shown promising results restoring muscle-tendon proprioception and in improving prosthetic control. However, challenges remain in constructing AMI due to anatomical limitations in residual limbs. A total of 25 lower legs from fresh-frozen human Caucasian donors were dissected, and the muscles relevant to the AMI technique, such as the gastrocnemius complex, the tibialis posterior, the tibialis anterior, and the peroneus longus, were analyzed. Demographic and anthropometric measurements, muscle preparation and weight, markings, imaging, and statistical analysis methods were described in detail. In all muscles examined, the intramuscular course of the tendon extended over more than 75% of the distal muscle belly. The muscle belly length of the peroneus longus muscle and the medial head of the gastrocnemius muscle showed a significant positive correlation with the weight and height of the donors. There were no significant correlations between the ratio of the intramuscular course of the tendon to muscle belly length and the weight or height of the donor. The AMI technique can enhance proprioceptive feedback for transtibial amputees wearing prostheses. The study indicates that gender does not impact muscle characteristics, but weight and height show correlations. These results offer valuable insights into muscle anatomy for informing future research on the functional effects of AMI and prosthetic limb design.