AI Article Synopsis
- The study investigates the effectiveness of using gracilis free functioning muscle transfer (FFMT) to restore elbow flexion after pan-brachial plexus injuries, focusing on different tendon insertion options.
- Cadaveric experiments revealed that the peak instantaneous moment arm for elbow flexion occurs between 83° to 92° at various insertion sites, with distal insertions (FDP/BRD) offering significantly greater strength potential compared to the biceps brachii insertion.
- The findings support the rationale for choosing distal muscle insertion locations in surgical planning, enhancing the reconstruction of elbow flexion strength based on measurable moment arm curves.
Article Abstract
Purpose: Following pan-brachial plexus injuries, restoration of elbow flexion is widely accepted as the reconstructive priority. A gracilis free functioning muscle transfer (FFMT) can be used to restore elbow flexion alone with insertion into the biceps brachii (BIC) or brachioradialis (BRD) tendons or restore combined elbow and finger flexion with a more distal insertion into the flexor digitorum profundus (FDP) tendons. Using cadaveric experiments, we determined the peak instantaneous moment arm for each insertion option.
Methods: Six simulated gracilis transfer surgeries were performed using both arms of three fresh-frozen full body cadaveric specimens (age: 79 + 10 years. 2 female). The gracilis muscles from both legs were harvested and transferred to the contralateral upper extremity. The elbow was manually moved through three flexion-extension cycles while the instantaneous moment arm was calculated from measurements of gracilis excursion and elbow joint angle for the three distal insertion sites.
Results: Peak instantaneous moment arm for all three insertions occurred at an elbow angle between 83° to 92° with a magnitude ranging from 33 mm to 54 mm. The more distal (FDP/BRD) insertions produced a significantly greater (∼1.5 times) peak elbow flexion instantaneous moment arm compared to the BIC insertion.
Conclusions: Based on the instantaneous moment arm, the gracilis FFMT distal insertion locations could result in greater reconstructed elbow flexion strength. In addition, direct measurement of the shape and magnitude of the moment arm curve for differing insertion sites allows high resolution surgical planning and model testing.
Clinical Relevance: This study presents the first direct experimental quantification of the gracilis FFMT instantaneous moment arm. The experimental evidence supports the use of FDP/BRD insertion locations by providing a quantitative explanation for the increased elbow flexion torque observed clinically in patients with a gracilis FFMT and distal FDP insertion.
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| http://dx.doi.org/10.1016/j.jhsa.2023.06.006 | DOI Listing |
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