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POSTEROMEDLAL APPROACH TO THE ULNAR NERVE

USES

This approach is used primarily for neurolysis of the ulnar nerve or anterior transposition of the nerve; however, this is a common enough procedure that this approach needs to be mastered. The approach can also be used for medial collateral ligament repairs of the elbow and coronoid fracture fixation. Campbell describes this approach combined with an osteotomy of the medial epicondyle.

ADVANTAGES

The posteromedial approach provides good visualization of the nerve and is easily extended proximally and distally.

DISADVANTAGES

This approach does not allow good access to the anterior or posterior elbow joint.

STRUCTURES AT RISK

If not done carefully, the ulnar nerve can be damaged. The motor branches of the ulnar nerve come off the nerve posteriorly. The branch to the flexor carpi ulnaris muscle can come off proximal to the elbow joint and must be avoided. When doing an anterior transposition of the ulnar nerve, the sensory branch going into the elbow joint frequently is not long enough to be salvaged. The motor branches to the flexor carpi ulnaris muscle must be saved. It is very helpful if this surgery is done with the patient not paralyzed and with the nerve stimulator used to identify the motor branches, which can be very small. A pure motor nerve has a small number of axons in it and so may not appear very nervelike. Sensory nerves have sensory axons for each sensory modality and are bigger and easier to identify. It is a pure motor nerve that is mistaken for other tissue and is at risk.

TECHNIQUE

A 10- or 12-cm incision is made, usually centered on the medial epicondyle and just 1 cm behind it. It is carried through subcutaneous tissue. The fascia overlying the muscles is split. This exposes the triceps posteriorly and the flexor carpi ulnaris tendon running off the medial epicondyle and going distally. The intermuscular septum is usually palpated at this point. The nerve is identified just behind the intermuscular septum and in front of the triceps muscle. This is done by blunt dissection. Once the nerve is identified, the cubital tunnel can be opened by placing a hemostat or some other blunt instrument to protect the nerve, while the overlying soft tissues are cut. Once the nerve has been freed through the entire course of the cubital tunnel, it is then necessary to free it up from its underlying soft tissues to prepare it for anterior transfer.