Title: Submuscular Ulnar Nerve Transposition at the Elbow. Published: 4/11/2011, Updated: 4/11/2011. 
Author(s): Susan E. Mackinnon MD, Andrew Yee BS. Division of Plastic and Reconstructive Surgery, Washington University School of Medicine, St. Louis, MO.

There is currently no evidence that any single operative procedure is “the best” for the management of cubital tunnel syndrome. However, our institution has stressed that the success of any described surgical techniques, for the management of cubital tunnel syndrome (CTS), is dependent on not creating a new compression point proximal or distal to the ulnar nerve decompression/transposition. Following a transposition, the ulnar nerve could be compressed at the medial epicondyle with a too-tight of a flip. In decompression and transposition procedures, it is important to ensure early range-of-movement to facilitate neural gliding. Failure at identifying and releasing all compression points at the cubital tunnel will result in recurrent CTS symptoms. The submuscular ulnar nerve transposition is the choice ulnar nerve procedure of our institution for management of cubital tunnel syndrome. In our experience, this procedure has not resulted in any recurrences of CTS symptoms, given that there is a recurrence rate with a simple decompression and a submuscular ulnar nerve transposition. The submuscular ulnar nerve transpositions completed by our institution can be further described as an intramuscular transposition with step-lengthening of the flexor-pronator muscles. In addition, to prevent any possible distal compression points during nerve regeneration within the hand, the submuscular ulnar nerve transposition is accompanied by a Guyon’s canal release and the decompression of the deep motor branch.

Surgical Tutorial – Submuscular Ulnar Nerve Transposition. A submuscular ulnar nerve transposition is performed to decompress the ulnar nerve in the cubital tunnel at the elbow. The medial antebrachial cutaneous nerve is identified and protected. Proximally, the medial intermuscular septum is resected. A step-lengthening of the fascia of the flexor-pronator muscles is performed. The ulnar nerve is placed in a transmuscular location. More importantly, the distal fascial septum between the flexor carpi ulnaris and the flexor-pronator muscles is removed.

Surgical Techniques

PROCEDURE: Submuscular Ulnar Nerve Transposition at the Elbow.

Incision Description: The incision is marked behind the medial epicondyle in line with the ulnar nerve. The use of a sterile tourniquet will provide a bloodless operative field, but will hide a possible proximal compression site from the Struther’s band when it exists. The tourniquet can be removed and the band addressed directly, as it is located directly underneath the tourniquet.

Sugical Steps:
Exposure and Dissection:
1. Incise skin and dissect through subcutaneous tissue.
2. Protect the crossing branches of the medial antebrachial cutaneous nerve. It is located 3.5cm distal to the medial epicondyle.
3. Palpate the medial intramuscular septum and identify the ulnar nerve just below.

Ulnar Nerve Submuscular Transposition: 
4. Decompress the ulnar nerve through the cubital tunnel.
5. Elevate the soft tissue above the flexor-pronator muscle fascia.
6. Identify and remove the medial intramuscular septum found proximal to the cubital tunnel.
7. Mark the step-lengthening pattern on the fascia of the flexor pronator muscle origin and elevate the two fascia flaps. Be sure the flaps are long enough to prevent tension on the ulnar nerve.
8. Identify the “T-shaped” fascia in the mid-portion of the flexor-pronator muscle origin and resect it. Be sure to not go too deep or else you will be in the elbow joint.
9. identify the fascia between the ulnar-innervated flexor carpi ulnaris and the median-innervated muscles and remove the fascicle. Always divide the fascial bands away from the medial epicondyle first and then resect them.
10. Divide the flexor-pronator muscles proximally down to the level of the brachialis.
11. Divide the more distal flexor-pronator muscle only as deep as you need to go in order to have a complete straight-line position of the ulnar nerve in the transposition site.
12. Neurolyse the posterior motor branches that tether the ulnar nerve posteriorly to allow a good anterior transposition of the ulnar nerve without tension.
13. Close the fascial flaps very loosely over the ulnar nerve.
14. Using your finger, run it proximally and distally to be sure that there is no proximal or distal compression points. Pay special attention distally to make sure that there is no fascial band that is kinking the ulnar nerve in the distal-most aspect of the transposition site.