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THE MEDIAL GASTROCNEMIUS FLAP: IS IT A VIABLE OPTION FOR FREE MUSCLE TRANSFER TO RESTORE ELBOW FLEXION?
Presenter: Steven H Bailey, MD
Co-Authors: Ramanadham S; Cheng J
UT Southwestern Medical Center

Background: Traditionally, gracilis free functional muscle transfer has been described as a viable option to restore elbow flexion after brachial plexus injury. The force-generating capacity of this muscle is often lacking,resulting in a weak elbow flexion. The purpose of this study is to critically assess the medial gastrocnemius muscle and detail anatomic and physiologic considerations that make the gastrocnemius muscle a better option for restoration of elbow flexion.

Methods: 11 flaps were harvested. Muscle and neurovascular dimensions were recorded including branching patterns, artery length and diameter, vein length, and nerve length. Additionally, physiologic parameters were measured (muscle length, achilles tendon length, volume, cross sectional area, fiber length and excursion). 3-D and 4-D CT angiography was performed for all specimens using dilute barium and omnipaque.

Results: Based on the dissections, the mean artery length and diameter were 4.2 cm and 1.94 mm, respectively. Mean vein length was 4.77 cm and nerve length was measured at 6.7 cm. Mean muscle fiber length was 20.17 cm and mean measured excursion was 3.49 cm. Potential excursion was calculated at 8.068 cm. Mean cross sectional area was 4.6 cm2. Measured values were compared to CT calculated values and a conversion factor was developed to estimate excursion and force generating capacity. Three main vessel branching types were encountered (Single dominant, Early bifurcation and Late trifurcation). The early branching pattern was found to be the most common which is the most suitable pattern for muscle splitting to imitate short head and long head biceps function.

Conclusion: Medial gastrocnemius functional free muscle transfer (MGFFMT) is a viable option for restoring elbow flexion after devastating upper brachial plexus injury. The muscle is expendable. The neurovascular branching patterns and pedicle lengths are consistent and are of adequate size and length for neurovascular anastomosis. Further more the physiologic parameters of the MGF allow for a closer approximation of normal biceps brachii function than the gracilis muscle.


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