Arm Flexion for Radial Nerve Gap Repair: An Anatomic Study
Jasmine A. Thum, MD1, Justin Luk, BS2 and Justin M. Brown, MD2, 1University of California, Los Angeles, Los Angeles, MA, 2Massachusetts General Hospital, Boston, MA
Introduction:
It is now well known that direct nerve repairs fare better than grafted nerve repairs. There is currently renewed interest in direct repair of nerves achieved by limb flexion followed by serial distraction as it is the least morbid and most easily implemented surgical technique to provide extra nerve excursion. This is especially simple in the upper extremity, which can be easily immobilized post-operatively in a sling. This anatomic study aims to (1)quantify nerve gap lengths that can be reliably overcome with elbow flexion (EF), with or without brachialis branch neurectomy, to inform surgical planning for direct repairs of the radial nerve (RN) and (2)provide guidance on rate of elbow distraction in the post-operative period after RN repair.
Methods & Materials:
Four fresh and 11 fixed cadaver arms with shoulder intact were dissected to determine the relationship between degrees of EF (ranged from 0-90 degrees EF) and nerve gap length overcome with proximal excursion of the distal nerve. Additional excursion from brachialis branch neurectomy was also assessed. (Image 1)
Results:
We found an approximately linear relationship between EF and RN excursion. Compliance of fresh cadaveric nerves more closely approximated that of surgical tissue. In fresh cadavers, there was 3mm of RN excursion per 10 degrees EF in the proximal half of the arm, and 4mm excursion per 10 degrees EF with neurectomy. (Image 2)
Conclusion:
Elbow flexion can significantly augment the ability to achieve an end-to-end repair of the RN. To simplify our findings, 90-degree EF should readily overcome a RN gap of 3.5cm, and additional brachialis neurectomy allows for total RN excursion of 4.7cm on average in the proximal arm with 90-degrees EF. Given nerve regeneration rates of 1-2mm/day, we recommend 14-27 days prior to full elbow extension from a RN repair performed with 90-degree EF without neurectomy, and 18-36 days for repair at 90-degree EF with neurectomy.
Image 1-RN Anatomy.jpg
Image 2-RN Graphs.jpg
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