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Title: Reconstruction of Iatrogenic Ulnar Nerve Injury Following an Ulnar Collateral Ligament Reconstruction.
PNS ID: 110325-2, Published: 3/25/2011, Updated: 3/25/2011.

Author(s): Andrew Yee BS, Simone W. Glaus MD, Susan E. Mackinnon MD.
Division of Plastic and Reconstructive Surgery, Washington University School of Medicine, St. Louis, MO.

Abstract: A 19-year-old right hand dominant athlete underwent a right ulnar collateral ligament reconstruction (Tommy John surgery). This was complicated by complete oblique transection of the ulnar nerve approximately 7 cm proximal to the elbow. The ulnar nerve was immediately primarily repaired and subcutaneously transposed. Five days following the ulnar nerve injury and reconstruction, the patient presented to our institution for consultation. The right arm was casted to support the collateral ligament repair. This prohibited extensive physical examination including pinch and grip testing, but a complete absence of sensation in the ulnar distribution was noted. Additionally, the patient reported significant neuropathic pain in the ulnar nerve distribution.

Regarding a surgical plan, options included an end-to-end (ETE) versus a reverse end-to-side (RETS) anterior interosseous to ulnar motor nerve transfer. Taking into consideration the immediate and excellent primary nerve repair and the relative youth and good regenerative capability of the patient, both institutions decided that there was a possibility for ulnar nerve regeneration and ulnar intrinsic recovery if the ulnar intrinsic muscles could be supported with a RETS nerve transfer. Our experimental work in a rodent model has shown that a RETS nerve transfer of a given nerve can provide the same number of nerve fibers as an end-to-end transfer of the same nerve (in press). When an acceptable donor motor nerve such as the distal AIN is available, a RETS nerve transfer, in combination with primary repair of the injured nerve proximally, may assist in augmenting the total number of nerve fibers reaching the distal muscle. Additionally, distal RETS nerve transfer may provide more expedient reinnervation of the motor end plates, babysitting; end plates through collateral sprouting until native motor axons have regenerated. This is critical in light of the time constraints for good motor recovery (in our clinical experience, little to no additional muscle functional recovery is seen after 12-18 months of denervation). With regards to sensory recovery, because sensory recovery is not subject to the same time limitations as motor recovery, both institutions determined not to proceed with any sensory nerve transfers. There is a reasonable chance that the patient will recover some sensation in the ring and small fingers from the initial primary ulnar nerve repair. If there is persistent numbness in these fingers over time, a third webspace to ulnar sensory nerve transfer could then be performed.

The actual surgical management of this case included a RETS anterior interosseous to ulnar motor nerve transfer and a profundus tenodesis. Due to the recent presentation of this case, the results following this reconstruction are pending long term follow-up.

Figures and Videos

Video 1 – Intra-operative Ulnar Nerve Stimulation Six Days Following an Ulnar Nerve Transection. Under tourniquet, the ulnar nerve was decompressed through Guyon’s canal, specifically releasing the deep motor branch, and the dissection of the ulnar nerve was carried proximally into the distal forearm. The sensory/motor topography mapping of the ulnar nerve was then completed to identify the dorsal cutaneous branch and the adjacent motor component of the ulnar nerve. The cleavage plane between the motor and sensory component of the ulnar nerve was then opened slightly for a distance of less than a centimeter. Even though the patient was dis days following the proximal transection of the ulnar nerve above the elbow, our institution elected to stimulate the ulnar nerve motor fascicular group to determine whether or not there was an indication of a Martin-Gruber anastomosis. Upon motor group stimulation in the video, there was some contraction of the ulnar intrinsic muscles. This case was an ideal situation for a reverse end-to-side (RETS) anterior interosseous to ulnar motor nerve transfer. If the classical direct end-to-end anterior interosseous to ulnar motor nerve transfer was performed, then the Martin-Gruber component from the median to ulnar nerve would have been sacrificed. In this situation, the Martin-Gruber anastomosis was an advantage and the RETS procedure allowed for the augmentation of this anastomosis.