Cubital tunnel decompression- In-situ distal to proximal release of the ulnar nerve

The shoulder externally rotates less with the arm adducted
The usual positioning of the hand table at and distal to the level of the shoulder places the arm with the shoulder in a position of abduction of about 50 degrees; for most patients, the arm will not easily externally rotate to allow the forearm to rest easily on the hand table. This means that the surgeon’s assistant needs to hold the arm rotated, and so cannot focus fully on retracting and optimising the surgeon’s view.
In the picture, the arm is being supported in maximal external rotation without forcing the forearm back. If surgery were to be performed with the arm in this position, the shoulder would need to be pushed into external rotation to orientate the medial aspect of the elbow for the surgeon and the forearm would need to be supported on a pad, potentially with a pad or bolster behind the elbow to assist positioning; unfortunately the elbow has a tendency to slip, which is frustrating and potentially dangerous.

Putting the arm table level with the head lets the arm lie naturally. Unless the shoulder is stiff, abduction of the shoulder to and above 90 degrees will usually allow the arm to rest easily on the hand table, which allows the assistant to focus fully on the operation.
If surgery is performed under local anaesthetic, then the patient may find it more comfortable to rest the hand behind or above their head. Aside from the obvious advantage of avoiding the potential complications and recovery periods of general anaesthesia or regional anaesthesia, the patient can move the elbow as instructed, which helps when assessing nerve and medial head of triceps stability.

The path of the ulnar nerve is palpated and marked, behind and below the medial epicondyle and distally into the forearm in between the two heads of FCUEven in muscular or obese patients, the ulnar nerve can usually be felt behind and below the medial epicondyle. Usually, with careful palpation, the nerve can also be felt where it passes distally into the forearm in between the two heads of FCU, the humeral head arising from the medial epicondyle and the ulnar head from the subcutaneous border of the olecranon.

Knowing where the nerve will be found helps when planning the incision. Feeling and marking the anticipated path of the nerve (N) allows for optimal placement of the initial surgical incision and potential extensions that may be needed in the event of the nerve not being found where expected, or being found to be unstable (in which case conversion to a transposition or medial epicondylectomy procedure may be required, necessitating proximal extension of the wound). Marking the position of the medial epicondyle (E) allows for accurate flap repositioning in the event that anterior transposition is required. The direction of the fibres of the two heads of FCU, humeral (FCUH) and ulnar (FCUU) have been drawn on for illustrative purposes.

Take care not to allow alcoholic skin prep. to get under the tourniquetFor surgery performed under general or regional anaesthesia, where control of the limb rests with the surgical team, preparation of the whole arm, starting with the hand, and initial covering of the arm with an appropriately-sized stockingette facilitates positioning of the arm. Alcohol-based skin preparation that soaks underneath the tourniquet can cause skin burns; while commercially-available barriers can be obtained to act as a “dam” to prevent skin prep. passing proximally under the tourniquet, if the hand is prepared first and care is taken when preparing the forearm, keeping it vertical and allowing the liquid to runoff while having an un-scrubbed team member apply initial manual blockade around the distal margin of the tourniquet, then inflating the tourniquet before completing preparation with a squeezed-out sponge up to the margin of the tourniquet, soaking of the padding wool can be avoided.

Mark the initial incision along with potential extensions that may be needed depending upon surgical findingsThe incision should pass over the palpated course of the ulnar nerve through the cubital tunnel and in between the two heads of FCU; the incision can stop at or just distal to a line passing between the medial epicondyle and the tip of the olecranon, although initially you may be more comfortable using a longer incision, curving proximally behind the medial epicondyle, and shortening the incision in subsequent cases as you become more confident with the proximal releases. In the picture, the dotted lines proximal and distal to the solid longitudinal line mark the extensions that may be required for exposure or to convert to a transposition. The transverse lines mark the initial limits of the incision; I find that a distal extension is more commonly required as there may be crossing branches of the medial cutaneous nerve of the forearm that require a longer distal incision to safely preserve the branches while allowing safe surgical exposure between the two heads of FCU, hence the solid incision line passing distally beyond the solid cross-lines. The dots adjacent to the incision line are to aid flap apposition on closure.

Incise the dermis down to the sub-cutaneous fat. Potential crossing branches of the medial cutaneous nerve of the forearm lie in the sub-cutaneous fat layer, the thickness of which varies considerably between individuals.
Initial sharp dissection, the direction of which would pass obliquely across the anticipated course of these cutaneous nerves and so increase the risk of nerve division, should stop once the dermis has been fully divided.

Spread using fine scissors down to muscle aponeurosis to identify cutaneous nerves. By spreading the jaws of the fine dissecting scissors in the anticipated line of passage of the cutaneous nerves, which is anterior/proximal to posterior/distal, significant branches can reliably be identified and so preserved, potentially requiring wound extension(s).

Cutaneous nerves can be preserved to minimise forearm numbness. Altered sensation along the medial border of the forearm towards and potentially as far as the wrist is a relatively common complaint following use of medial surgical approaches to the elbow. By identifying and preserving significantly-sized branches, the extent of sensory impairment can be minimised (both the area and the level of impairment).

Use your assistant to retract cutaneous nerves and clear the Flexor Carpi Ulnaris aponeurosis. Care should be taken to avoid forceful retraction of the nerve branches, to minimise the risk of cutaneous nerve impairment; this may require the skin incision to be extended to allow for adequate surgical “windows” to be created either side of the crossing nerve, allowing more limited retraction of the nerve both proximally and distally when performing the necessary exposure and release of the ulnar nerve deep to the crossing cutaneous nerves. The fascia overlying the two heads of FCU can be seen exposed deep to the sub-cutaneous fat layer; the fibrous tissues can be seen to pass in three directions, with fibres running obliquely in the line of the muscle fibres of both the humeral and the ulnar heads of FCU and, passing between the two fibrous elements, the third fibrous component passing across between the two heads of FCU (straight, or slightly curved apex-distal). It is this third element that forms the “roof” over the nerve, with muscle fibres sandwiched in between the aponeurosis and the ulnar nerve; the ulnar nerve will lie in the apex or “V” formed by the approximation of the two heads of FCU.

Now expose the nerve where it enters the forearmFeel the path of the ulnar nerve passing between the two heads of FCU to ensure that the aponeurosis is divided directly above the nerve, making exposure of the nerve when subsequently separating the two heads of FCU easier and quicker.

Incise the aponeurosis longitudinally along the interval between the muscle fibres of the two heads of FCU, passing distally through the transversely-orientated / curved fibres, without incising the underlying muscle fibres. Do not worry about the proximal limit of the release at this stage; the incision through the aponeurosis is to enable identification and distal release of the ulnar nerve at this point in the operation.

Use the fine scissors to separate the muscle heads exposing the ulnar nerve. By placing the curved fine dissecting scissors between the converging muscle fibres of the humeral and the ulnar heads of FCU with the tips of the scissors pointing up out of the wound (i.e., away from the underlying nerve), then gently separating the blades, the two heads of FCU will be separated, exposing the underlying ulnar nerve surrounded by the peri-neural fat. (A single residual strand of the transverse fibrous aponeurosis can be seen in the picture,which was divided soon after; this is not of any relevance!)

Expose the nerve between the two heads of FCU and release any crossing fibrous bands first working distally. Separate the tissues superficial to the nerve, identifying and controlling / dividing any crossing fibrous or vascular elements. There is no need to dissect deep to the nerve unless there is a clear area of circumferential peri-neural fibrosis, which is uncommon in a primary procedure unless there has been significant previous local trauma. By leaving the deep tissues undisturbed, damage to the neural blood supply can be minimised, as is the risk of rendering the nerve unstable through the dissection.

Take care not to damage motor branches passing to innervate FCU. These motor nerve branches can be identified and preserved with careful surgical technique. In the picture, a motor division can be seen passing distally between the separated jaws of the dissecting scissors, passing just anterior to (above) the tips of the forceps.

Confirm adequate distal release between the two heads of FCU has been achieved . There is often a fibrous arch at the distal end of the confluence between the two heads of FCU; in clinical practice, I find this site often corresponds with the site of maximal pre-operative neural irritability to percussion along the path of the ulnar nerve (Tinel’s sign). Having carefully divided any fibrous arches, confirm that the passage of the nerve into the forearm is not compromised by gently passing an instrument superficial to the nerve (such as a McDonald’s dissector, as used in the picture).

Now release the nerve from under the fibrous arch at the proximal end of Osborne’s ligamentHaving completed the distal release, attention can be turned to the proximal passage of the ulnar nerve. Remembering and retracting the previously identified cutaneous nerves, the tissues superficial to the ulnar nerve are mobilised and divided to expose and simultaneously decompress the ulnar nerve. In the picture, the separated jaws of the fine dissecting scissors can be seen defining a crossing fibrous sheet with bands of condensations of fibrous tissues; these form Osborne’s ligament which forms the roof of the cubital tunnel, which will have been partially divided at its distal limit in the preceding steps of the operation.

Ensure the fibrous band as been freed from the nerve and any vessels controlled before dividing it. By carefully and incrementally passing the closed tips of the dissecting scissors into the plane between Osborne’s ligament and the underlying ulnar nerve, gently opening the jaws to break down any adhesions, but being careful to withdraw the scissors with the jaws still opened (to minimise the risk of accidental damage to the ulnar nerve), a clear plane can be developed to isolate the ligament prior to division of the ligament itself. Commonly there will be crossing vessels, particularly along the proximal limit of the ligament; these vessels need to be carefully controlled prior to division, using fine bipolar diathermy forceps , lifting the ligament and vessels up and away from the nerve before deploying the diathermy, and using repeated very short pulses of the diathermy to minimise the risk of accidental thermal injury to the ulnar nerve.

Having created planes above and below the fibrous band, divide it. As long as the ligament has been fully freed from the nerve, the dissecting scissors can be used to divide the ligament under direct vision; if there is any doubt about the presence of any persisting neural adhesions, using a fresh scalpel blade (No. 15) with care to align the blade parallel to the nerve and to keep the ligament tissue taut with gentle pressure on the scalpel blade against the tensioned fibrous tissues affording division of the ligament while allowing the nerve to “roll away” is a safer way to proceed; this is a technique best developed following observation of its use by repeated supervised practice.

Next develop a pocket superficial to the fascia proximally towards the shoulder along the path of the nerveYou can see in this picture the ulnar nerve passing proximally between the divided edges of Osborne’s ligament (the anterior edge being more clearly seen passing distally from the Langenbeck-type right angle retractor). You should also be able to recognise that the Langenbeck retractor is no longer being used with the blade passing vertically into the wound (to hold the cutaneous nerves at the proximal limit of the incision) but instead that the blade of the retractor has been passed into a pocket created by blunt dissection with the scissors between the fascia and the subcutaneous fat layer, the blade lying parallel and following the path of the underlying ulnar nerve (which is still deep to the intact proximal fascia) and the overlying fat and skin (along with the previously preserved cutaneous nerve branches). By pulling the handle of the retractor away from the arm, the skin and fat are lifted away from the fascia and the underlying ulnar nerve, creating a tunnel above the fascia that allows direct vision of the fascia proximal to the site of previous division of Osborne’s ligament.

Extend the elbow to look up the tunnel that you have created proximally. Straightening out the elbow allows the operating surgeon, now sitting towards the end of the hand table, to crouch and look up into the tunnel; careful positioning of the operating light to focus up the tunnel created by the Langenbeck retractor (the beam passing over the shoulder of the operating surgeon) allows the proximal release to be undertaken under direct vision despite the overlying skin remaining intact.

Develop a plane above and below the fascia proximally under direct vision to extend the tunnel proximally. The Langenbeck retractor blade should be fully seated proximally and pulled away from the patient to maximise the field of view. The fascia is released from the underlying ulnar nerve using the same careful technique described for freeing Osborne’s ligament in the previous steps.

Carefully divide the fascia under direct vision, controlling any crossing vessels that may be encountered. Sharp dissection working proximally from the free edge of the fascia with a fresh scalpel blade (carefully aligned to lie parallel with the nerve, as previously described) is useful, but the most proximal extent of the release is more easily performed using the opened jaws of the fine dissecting scissors as a blade. Having extended the proximal limit of tunnel superficial and deep to the fascia under direct vision using blunt dissection with the dissecting scissors, the opened jaws of the scissors are placed with the free edge of the fascia between the opened (and fixed) jaws of the scissors.

The proximal release can be completed using the opened jaws of a pair of long-handled scissors that have engaged the edge of the fascia under direct vision. It is important that you have freed the fascia from the nerve and the overlying fat to adequately define the fascia, and that the scissors are held opened and not closed, so that the scissors act as a blade with firm but controlled proximal pressure directed proximally to divide the fascia. By ensuring the jaws of the scissors are never closed, the risk of inadvertent nerve damage is minimised.

Confirm adequate proximal release using a McDonald’s dissector or equivalent curved instrument in the same way as previously used for the distal release.

Confirm that the ulnar nerve is stable behind the medial epicondyle through a full range of flexion under direct vision prior to wound closureAs long as you have not dissected the nerve from the floor of the cubital tunnel, the nerve is unlikely to have been made unstable by the release procedure. nonetheless, it is important to confirm and document that the nerve remains stable throughout a full range of motion; anterior subluxation is usually seen in the more extreme flexion range; if present, ulnar nerve instability should prompt consideration of formal anterior transposition of the nerve.

Confirm that any crossing cutaneous nerves remain in-continuty. The two cutaneous nerves identified at the outset of the procedure can be seen intact, lying vertically in the wound. The two edges of the divided Osborne’s ligament can be seen lying to the left of the cutaneous nerves.

Confirm haemostasis and then close the subcutaneous fat and the skin in two layers

As long as there have been no problems with exposure and that the ulnar nerve remains stable, the initial incision need not be extended.

Apply steristrips to support and detension the wound, then liberally infiltrate local anaesthetic with adrenaline being careful to include the line of the proximal release. While administration of the local anaesthetic and adrenaline to deeper planes can usefully be performed prior to closure, particularly at the proximal and distal ends of the surgical field, I prefer to infiltrate the skin after wound closure to allow for more accurate skin apposition.

Cover the wound with a waterproof adhesive dressing then apply a bulky bandage to the elbow. If an extension proximal to the elbow has been used, applying the anterior length of the adhesive dressing with the elbow extended and the posterior half with the elbow flexed will minimise any reduction in active post-operative movement of the elbow due to tension from the dressing. A bulky bandage (wool and crepe) will initially slow motion to help with post-operative discomfort by reminding the patient to minimise un-necessary use of the operated arm.