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Overview

Title: Reconstruction of a Failed 4cm Collagen Conduit Ulnar Nerve Conduit.
PNS ID: 110302-1, Published: 3/2/2011, Updated: 4/5/2011.

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

Abstract: This 57 year-old male sustained a laceration to the ulnar nerve at elbow level upon accidentally falling through a glass shower door. At an outside institution, the patient underwent a submuscular ulnar nerve transposition and ulnar nerve grafting with two 6 mm diameter conduits sewn end-to-end. Five years postoperatively, the patient was referred to our institution predominantly for unbearable neuropathic pain. The patient had no ulnar intrinsic function in the hand. The patient underwent re-exploration. The gap present after resecting back to healthy nerve was too large to permit successful grafting. A tenodesis of the profundus tendons was performed to give better grip, and an extensor indicis proprius tendon transfer was performed to provide improved thumb pinch. Sensation in the ulnar nerve distribution was achieved with a direct nerve transfer from the third web space component of the median nerve to the main sensory component of the ulnar nerve. The less critical sensory component of the ulnar nerve (the dorsal cutaneous branch of ulnar nerve) and the distal portion of the donor third web space component of the median nerve were transferred in an end-to-side fashion in order to restore some, but not normal, sensation to these territories. The patient’s pain was almost immediately well controlled, and his sensory and motor function subsequently improved.

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History

A 57 year-old male accidentally fell through a glass shower door and sustained multiple lacerations to his right arm, including three around the level of the elbow. The patient was felt to have a traumatic ulnar neuritis at initial presentation and was sent for follow-up with a hand specialist. The patient’s ulnar neuropathy did not improve, so an EMG was obtained approximately 1 month post-injury. EMG showed a severe, right-sided ulnar mononeuropathy at the level of the elbow with severe sensory and motor axonal loss, most consistent with nerve transection. The patient was taken to the OR, where an ulnar nerve neuroma-in-continuity was found just proximal to the level of the medial epicondyle. A submuscular ulnar nerve transposition was performed. The neuroma was removed and the ulnar nerve trimmed back to healthy fascicles. Two 6 mm collagen nerve conduits were sewn together in an end-to-end fashion and interposed between the proximal and distal nerve stumps to bridge the gap in a tension-free fashion. The patient had no complications postoperatively. By 13 months postoperatively, the patient had persistent intrinsic muscle atrophy but was felt to have regained protective sensation in the ring and small fingers and to be able to abduct his fingers against resistance. He continued to have pain at the nerve repair site, however, for which he received Neurontin, amitriptyline, and a referral to a pain specialist. Four and half year postoperatively, the patient had persistent pain, ulnar atrophy, weakness, and complaints of numbness. He was referred to our practice with the hope of achieving better pain relief.

Physical Examination

Complete intrinsic muscle atrophy and clawing of the ring and small fingers were present in the right hand. Sensory exam revealed no sensation in the right ulnar nerve distribution. Two-point discrimination in the median nerve distribution was 5-6 mm. Motor exam showed a positive Froment’s sign, a pinch strength of 6 lb, and a grip strength of 41 lb. Pinch and grip on the left were 13 lb and 70 lb, respectively. Tinel’s sign was present at the level of the ulnar nerve repair/transposition.

Diagnostic Testing

No diagnostic testing was performed given the patient’s physical examination, which was clearly consistent with a complete right ulnar neuropathy.

Management

Pre-operative: None

Surgical: The ulnar nerve was approached via the patient’s previous incision, which was extended proximally and distally. The ulnar nerve was traced to its reconstruction site, where there was just a thread of continuity between the two ends. A large neuroma was present proximally, and a large glioma distally. Intraoperative stimulation demonstrated no electrical continuity across the conduit reconstruction. The conduit and proximal stump neuroma were resected. The resulting gap was too large to be reconstructed with an autograft. The proximal ulnar nerve stump was crushed multiple times, cauterized, and then buried between the biceps and brachialis muscles. A separate distal incision was then made to identify the ulnar nerve within Guyon’s canal. The ulnar nerve was decompressed through Guyon’s canal and at the deep motor branch distally. The motor component of the ulnar nerve was then traced proximally to identify the sensory and motor topography. The median nerve was identified in the carpal tunnel, decompressed, and followed distally to the third webspace component. Nerve transfer of the third web space median nerve to the sensory component of the ulnar nerve was performed under the operating microscope. Additionally, end-to-side nerve transfer of the distal end of the third web space median nerve to the median nerve proper was performed, as well as end-to-side transfer of the ulnar nerve dorsal cutaneous branch to the proximal part of the third web space median nerve. For motor reconstruction, the FDP tendons to the ring and small finger were joined in a side-to-side fashion to the FDP tendons of the index and long fingers, and an extensor indicis proprius tendon transfer for thumb adduction was performed.

Post-operative: The patient was begun on early physical therapy two days after surgery, three times per week. For four weeks postoperatively, the patient’s thumb was maintained in adduction and an extension block splint was worn to protect his FDP transfer.

Patient Outcomes

The patient’s pain was dramatically improved postoperatively. He did experience occasional brief shooting pains radiating down his right ring and small fingers. By three months, the patient had begun using his right hand to perform some activities of daily living. Sensory revealed no light touch sensation in the ulnar nerve distribution. Motor exam showed pinch strength of 12 lb and grip strength of 35 lb, compared to 23 lb and 74 lb on the left. Further postoperatively follow-up is pending. Given the typical nerve regeneration rate of one mm per day, or one inch per month, a longer period of follow-up is required to observe ulnar nerve recovery.

Discussion

While conduits have been used in the successful repair of short gaps in small diameter nerves, particularly digital nerves, empty conduit reconstruction has yet to be proven effective for bridging long nerve gaps in large diameter nerves. In fact, conduit failures for these clinical cases have recently been reported. Reconstruction of gaps in critical large diameter nerves such as the ulnar nerve should utilize autografts, which are the gold standard and provide endoneurial architecture as well as Schwann cell support. When the gap is prohibitively large, as in the above case, nerve and/or tendon transfers should be performed.

References

Brown JM, Yee A, Mackinnon SE. Distal median to ulnar nerve transfers to restore ulnar motor and sensory function within the hand: technical nuances. Neurosurgery. 2009 Nov; 65(5): 966-77.
 
Moore AM, Kasukurthi R, Magill CK, Farhadi HF, Borschel GH, Mackinnon SE. Limitations of conduits in peripheral nerve repairs. Hand. 2009 Jun; 4(2): 180-6.