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Carpal Tunnel decompression- Extended approach

    Overview

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    Learn the Carpal Tunnel decompression: Extended approach surgical technique with step by step instructions on OrthOracle. Our e-learning platform contains high resolution images and a certified CME of the Carpal Tunnel decompression: Extended approach surgical procedure.

    In carpal tunnel syndrome the median nerve is compressed as it passes under the flexor retinaculum at the wrist, and for the vast majority of cases, an open decompression performed in the palm allows adequate visualisation and decompression of the median nerve at this level. However, there are instances when there is a suspicion of another pathology involving the median nerve. Flexor tenosynovitis associated with inflammatory arthropathy, suspected nerve tumours and revision surgery for failed previous carpal tunnel surgery are the most common of these. In these instances a more extensile exposure of the nerve is required.
    Readers will also find the following associated techniques of interest:
    Carpal tunnel decompression
    Revision carpal tunnel decompression and application of Polyganics Vivosorb membrane
    Combined median and ulnar nerve decompressions
    Median nerve neurolysis, resection and reconstruction using Axogen AVANCE processed nerve allograft

    Indications

    In certain instances, during decompression of the median nerve, the surgeon requires a wider exposure of the nerve and flexor tendons. By extending the approach across the wrist crease, onto the distal forearm, the median nerve, it’s branches and the flexor tendons with their investing sheaths can be inspected. Most commonly this approach is required when there is a suspicion of more widespread pathology, in particular flexor tenosynovitis or nerve tumour, or when revision surgery is being undertaken for carpal tunnel syndrome.
    Non-supporative flexor tenosynovitis is associated with inflammatory conditions such as rheumatoid arthritis. The inflammation can lead to acute median nerve symptoms as well as tendon irritation, tendon attrition and eventually flexor tendon rupture. The synovial sheaths, which form the radial and ulnar bursa, extend through the carpal tunnel and into the distal forearm, investing all the flexor tendons in the distal forearm. Although non-operative treatment with anti-inflammatory drugs has become the mainstay of treatment for flexor tenosynovitis, tenosynovectomy remains an effective procedure and has been shown to be reliable in preventing tendon rupture. Tenosynovectomy is best performed through an extended carpal tunnel approach.
    Carpal tunnel decompression is generally a reliable and effective procedure. When surgical treatment fails it is important to distinguish between patients who report no improvement following surgery, those with new or different symptoms post surgery, and those who initially improved but go on to develop a recurrence of their original symptoms. For patients who experience no improvement, the initial diagnosis may have been incorrect. Cubital tunnel syndrome, cervical radiculopathy and peripheral neuropathies are common conditions that can mimic carpal tunnel syndrome, thoracic outlet syndrome and more proximal compression of the median nerve are rarer examples of a ‘double crush’ phenomena and all of these conditions should be looked for in the initial pre-operative assessment.
    When it appears that the pre-operative diagnosis was correct but there are ongoing median nerve symptoms then the possibility of inadequate or incomplete release of the nerve has to be considered. In an individual who develops new symptoms following surgery, especially new painful nerve symptoms in conjunction with motor or sensory dysfunction, the possibility of a nerve injury should be considered. Occasionally, patients will present with recurrence after initial improvement of symptoms and this can be caused by adhesions around the median nerve at the site of previous surgery.
    Revision surgery is indicated in cases where incomplete release, nerve scarring or nerve injury are suspected. Repeat surgery and exposure of the nerve in a scarred bed can be demanding surgery and there is inherent risk of further injury to the median nerve. The safest approach is to initially expose the nerve where it lies in normal ‘virgin’ tissue. Once the nerve has been confidently exposed and the correct tissue planes identified the nerve is traced into the previously operated on scarred area. The quality of your surgical instruments is of key importance. A mixture of sharp and blunt dissection is used to trace and externally neurolyse the scarred nerve. I prefer a pair of fine-tipped tenotomy scissors and non-toothed atraumatic tissue forceps (Debakey) for the dissection, and always have an array of micro-surgical instruments available whenever I intend to dissect around a nerve.

    Setup

    A regional anaesthetic block of the brachial plexus (axillary block) provides optimal anaesthesia, otherwise general anaesthesia will be required. A tourniquet is applied to the upper arm and inflated after appropriate exsanguination of the limb with an Eschmark bandage. A lead hand is useful to position and support the hand with the fingers extended and the wrist and forearm in a supinated position. The hand will tend to pronate if not supported and this can mis-direct the surgical dissection in an ulnar direction, so it’s worth periodically checking that the hand position has been correctly maintained during the exposure.

    Operation

    Mark the skin incision. The distal incision is as for a standard carpal tunnel approach, lining up with the radial side of the ring finger. Incorporation of ‘V’ component to the incision as it crosses the wrist crease avoids the scar perpendicularly crossing the flexion crease, which can lead to the formation of a scar contracture. The apex of the ‘V’ is pointed in an ulnar direction so as to avoid the palmar cutaneous branch of the median nerve. Proximally, the line of incision is on the ulnar edge of the Palmaris Longus.

    The distal exposure is as for a standard carpal tunnel decompression. A natural plane between the hypothenar and thenar fat pads will exist and can be developed with minimal need for sharp dissection. This is a safe plane with relatively few vessels or cutaneous nerve branches. Immediately deep to the fat pads lie the longitudinal fibres of the palmar aponeurosis, an extension of the Palmaris Longus tendon.

    The palmar aponeurosis is split longitudinally in line with it’s fibres. Proximally, dissection is performed just ulnar to the Palmaris Longus tendon as the palmar cutaneous branch of the median nerve lies immediately radial to the tendon. A further small fat pad exists between the deep surface of the palmar aponeurosis and flexor retinaculum, this is retracted to display the flexor retinaculum and deep forearm fascia which form a continuous layer.

    a. Palmar aponeurosis
    b. Palmaris Longus
    c. Deep forearm fascia and flexor retinaculum
    d. Fat pad deep to palmar aponeurosis

    The deep forearm fascia and flexor retinaculum are incised and retracted to expose the median nerve and flexor tenosynovium. Note the thickening of the tenosynovium (a.). In this case, the vaso nervorum on the anterior surface of the median nerve can be seen to diminish at wrist level indicating compression of the nerve at this level (b.).
    If the nerve has to be dissected from a scarred bed then first expose the nerve where it is healthy and lies in ‘virgin’ tissue. Once the nerve has been confidently exposed it can be trace into the previously operated on scarred area. I prefer to use a pair of fine-tipped tenotomy scissors and non-toothed, atraumatic tissue forceps (Debakey) when performing a neurolysis and will switch to micro-surgical instruments when dissecting smaller calibre nerve branches.

    The thickened flexor tenosynovium individually invaginates the flexor digitorum superficialis and profundus tendons, as well as the flexor pollices longus tendon.

    Tenosynovectomy is best performed with tenotomy scissors. Each tendon is individually stripped of its investing sheath. In this case only a limited tenosynovectomy was required to allow histological analysis and fully decompress the median nerve.

    The tenosynovium has a rich vascular capillary supply and dissection will leave a surgical bed prone to bleeding. The tourniquet should be released and careful attention paid to haemostasis using bipolar diathermy. Following this the skin wound is closed using interrupted nylon sutures.

    Post Operative

    A non-adherent dressing covers the wound and wool and crepe bandage layers are applied to support and protect the extremity. The metacarpophalangeal joints should be left free enough so that they can flex and extend without undue restriction.
    The patient is advised on limb elevation to help control post operative swelling. This is best achieved with a high arm sling for when the patient is upright and pillows when lying. Elevation should be continued throughout the postoperative period, whilst the extremity remains swollen and the wound is healing. The bulky dressing is replaced with a light occlusive dressing after 72 hours and this allows for greater mobilisation and light hand activities needed for basic daily living tasks to be resumed.
    Sutures are removed at between 10 and 14 days.

    Recommended Reading

    Reference

    • orthoracle.com

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