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Median nerve reconstruction

    Overview

    Learn the Median nerve reconstruction surgical technique with step by step instructions on OrthOracle. Our e-learning platform contains high resolution images and a certified CME of the Median nerve reconstruction surgical procedure.
    Reconstruction of a peripheral nerve with autograft is a useful technique that has numerous applications including reconstruction of a nerve gap following trauma, and excision and grafting of a neuroma in continuity.
    The following case serves to demonstrate the technique in a patient that had previously had treatment for a complete median nerve division at the wrist with surgical exploration and subsequent reconstruction of a nerve gap using processed nerve allograft.
    The patient went on to have very little sensory or motor recovery through the allograft and developed a neuroma in continuity.
    The decision was made to re-explore and to excise the graft and any proximal neuroma and perform a cabled autograft reconstruction using sural nerve autograft.


    Indications

    INDICATIONS:
    Treatment for a failed or poorly regenerating nerve graft reconstruction represents a difficult problem. Decision making here has much in common with that of a neuroma in continuity with poor sensory and motor function. In patients with poor sensory and motor recovery within an important peripheral nerve trunk, the decision to excise and graft is clearer. Where there is satisfactory motor recovery but poor sensation, one may elect to reconstruct only the sensory component, using intra-operative nerve stimulation to identify and preserve motor fascicles.
    In this patient who previously underwent median nerve reconstruction with a 5cm processed nerve allograft, there had been limited motor or sensory recovery through the graft with a painful neuroma over the proximal graft site. The decision was therefore made to excise the original allograft and any neuroma to obtain normal nerve architecture proximally, and to then re-graft the resultant gap using sural nerve autograft.
    The decision making in such cases is not always straightforward. Eventual outcome is difficult to predict and it is important for a surgeon experienced in the management of these problems to consider all of the various treatment options and to discuss them with the patient.
    SYMPTOMS & ASSESSMENT:
    Clinical examination is key. Motor function is assessed clinically and the MRC grade recorded. It is important to note the presence of any joint stiffness or contracture that may influence the decision to attempt motor reinneravtion. Sensory function may be tested with a variety of clinical tests including, two point discrimination, Semmes-Weinstein monofilament testing, and a visual analogue score (VAS). It is important to be able to record clinical findings over time, and of course to compare pre and post-operative findings. The presence of a Tinel-Hoffman sign is useful. In this case there was a prominent non-progressive Tinel-Hoffmans just proximal to the original graft and a less prominent one overlying the midportion of the graft that was non-progressive. Such findings are suggestive of significant failure of axon growth into the graft and possibly arrest of some regenerating axons within the graft.
    INVESTIGATION:
    Nerve conduction tests and electromyography may demonstrate progression or failure of recovery. Results should always be interpreted alongside clinical findings as clinical recovery may precede EMG changes.
    Imaging may be a useful adjunct in some cases. Ultrasound or MRI can visualise the nerve, demonstrate the anatomy of a neuroma and confirm continuity.
    OPERATIVE ALTERNATIVES:
    Where the injured nerve trunk offers poor prospects for repair or reconstruction, nerve transfer surgery may be considered. This is discussed in more detail elsewhere.
    In longer-standing lesions with poor motor function within an important muscle group, one may decide upon tendon transfers to restore motor function. Long standing complete denervation of a muscle (widely considered to include anything over 12 months) is an unfavourable prospect for reinnervation.
    NON-OPERATIVE ALTERNATIVES:
    Where recovery has not yet plateaued, observation for further recovery is an option. It is a matter of clinical judgment as to whether further useful recovery may be anticipated, or merely delays, and possibly compromises the results of, surgical intervention.
    CONTRAINDICATIONS:
    The usual contraindications concerning ongoing infection, poor skin quality and general patient fitness apply. Caution is advised if the distal limb is felt unlikely to regain useful motor or sensory function following successful regeneration through the nerve graft. The donor site must be considered carefully and in those with neuropathic pain, a second site of sensitisation may develop following autograft harvest.

    Setup

    The procedure is performed under general anaesthesia with local anaesthetic infiltration with or without a nerve catheter at the end of the procedure. Ideally a muscle relaxant should not be used.
    The patient is positioned supine with the affected hand on an arm table. One leg is also be prepped and draped and the choice of side should be discussed with the patient pre-procedure.
    Tourniquets are used for both arm and leg. They are inflated as required. For the arm, the tourniquet time is critical since nerve stimulation will be used and is unreliable after 15 minutes. In this case the forearm tourniquet was inflated just prior to the skin incision.
    A second surgeon to harvest the graft is useful if available.
    Loupe magnification is required and an operating microscope should be available.
    Neurotomes may be used to assist with neuroma debridement.
    Standard nerve microsurgical instruments and nerve sloops should be used. Jeweller’s forceps are used to hold the nerve graft ends during suture placement. Serrated microsurgical scissors are ideal for nerve epineurium trimming or for sectioning the sural nerve graft cables.
    Thrombo-prophylaxis should be considered and applied according to local guidelines.

    Operation – 1

    The hand is positioned on the arm table.
    The previous operative scar is visible and can be seen to extend over the carpal tunnel.

    The skin is marked out and incised.

    There is dense scar tissue throughout the planes of the previous approach. It is important to attempt to define layers as one progresses through the scar. In this case opening up the carpal tunnel allowed identificaton of the nerve and the layers overlying it distally, prior to working through the very dense scar that surrounded the allograft more proximally.

    Haemostasis is performed using bipolar diathermy.

    The deep fascia may not be especially well defined in the line of the scar but efforts to identify it and preserve it as a layer should be made.
    Here it is undermined to improve access. It is clear that the nerve is enveloped in scar.
    Efforts are made to identify and preserve the palmar cutaneous branch which was not involved in the original injury and is functional.
    Once identified, the nerve should be handled carefully using DeBakey’s forceps which are less traumatic to the epineurium.
    Nerve sloops should be used to protect the nerve and through them gentle traction may be applied if needed.

    Nerve sloops are placed proximally and distally around the native nerve using a pair of Mixter forceps.
    Nerve stimulation should be used at this stage to identify the presence of any functioning motor fascicles to the thenar muscle group. These are located within the radial aspect of the median nerve at this level. If motor activity is identified it represents some recovery through the graft and consideration can then be given to preserving these fascicles. Here, no muscle contraction was elicited even at supra-normal stimulation voltages.
    Once the decision is made to excise the entire segment of nerve allograft it can be dissected free. Here it was tethered to scar tissue and careful dissection enabled complete exposure.

    The allograft has now been completely exposed. The distal sutures are visible, marking out the interface between the distal allograft and median nerve. A sharp blade is used to divide the nerve at this level.
    A – Palmar cutaneous branch of the median nerve
    B – Distal end of the median nerve
    C – Proximal end of the median nerve

    The distal aspect of the graft has been divided. Dense scar tissue with disorganised neural components are seen. Slices of the distal end can be further cut in a sequential fashion to ensure that the distal nerve architecture is free of scar tissue.
    A- Distal median nerve
    B- Allograft – still attached to proximal median nerve

    Attention is now turned to the proximal end of the nerve which may be cut sharpy to expose viable fascicles.
    My initial cut is placed within the proximal end of the allograft. Disorganised nerve tissue much like that seen in a neuroma is exposed.
    From this point, sequential slices proximally may be taken until normal nerve architecture is seen.


    From this point, sequential slices proximally may be taken until normal nerve architecture is seen.
    A – Nerve allograft – excised
    B – Proximal median nerve

    A further slice is taken proximally.

    The next slice exposes some more normal looking fascicles alongside some proximal scar tissue.

    The presence of normal fascicles with bleeding through perineurial vessels indicates that normal proximal nerve has been reached.

    The nerve gap is now measured to guide sural nerve harvest.

    Proximal and distal nerve ends are placed onto background material.
    The wound is irrigated to prevent dessication.

    The sural nerve is now cut into an appropriate number of cables of the correct length to bridge the gap.
    The graft is placed in a reverse orientation in order to prevent axon loss through endoneurial side branches. Placing a blue dot at the distal end of each cable prevents any confusion about orientation.
    Dessication of the graft and loss of the graft from the table are concerns. Ideally graft preparation should be done on a separate table supported upon a flat, firm surface such as the back of a kidney dish as shown here. Damp swabs should be used to ensure the graft remains moist throughout. Once prepared the graft should be wrapped in a damp swap until required when it is carefully opened up at the operating site.
    Note: The technique of sural nerve harvest is demonstrated elsewhere.

    The cables are positioned into the gap in the correct orientation with the distal ends placed at the proximal end of the median nerve gap.

    Four fascicles of a large calibre sural nerve have filled the gap in this case.
    One cable is lined up with the radial motor fascicles, and three are lined up with the sensory fascicles.

    Micro-instruments and microscope magnification is used to place epineurial sutures to align and secure the graft cables into place.
    9/0 nylon suture is used.
    I have sutured individual cables here to correspond to fascicle groups. An alternative technique is to glue the cables together prior to placing the entire cabled graft construct into the gap.

    Once the proximal sutures have been placed, any excess graft length may be trimmed before placing the distal sutures.
    Some laxity should remain in order to achieve a tension free repair.
    A- Proximal suture repair

    Fibrin glue is placed over the distal neurorrhaphy.

    Fibrin glue placed proximally.

    The Birmingham cigar technique may be used to achieve a circumferential seal of fibrin around any neurorrhaphy.

    After haemostasis and irrigation, local anaesthetic may be infiltrated into the wound edges and over the nerve.
    If neuropathic pain has been a predominant feature one may consider a longer period of infiltration over the nerve by placing a temporary nerve catheter for 24-48 hours.


    A layered wound closure is performed using 4/0 monocryl, followed by 4/0 nylon interrupted skin sutures.

    Operation – 2

    The wound is cleaned and an adhesive dressing applied.

    A well padded soft dressing is applied.
    This will also serve to limit excessive wrist extension in the early post-operative period.

    Post Operative

    The patient will require post operative oral analgesia and may return home as soon as it is safe to do so. In our practice this is often on the day of surgery.
    Elevation in a Bradford sling is advised.
    The wound is examined at 7 days in a dressing clinic and redressed. Sutures are removed at 10-14 days and gentle wrist and hand mobilisation started with specific attention to nerve gliding exercises. This should be supervised by a hand therapist.
    The patient may notice some immediate deterioration of function within the median nerve territory and should be counselled about this pre-operatively. Gradual recovery through the nerve graft is expected to take several months.

    Recommended Reading

    There are a great many studies reporting the results of primary repair with inferior motor and sensory recovery in older patients, more proximal injuries and following significant delay to surgery.
    There is no doubt that the results of autograft reconstruction are inferior to those of primary repair. The two large series below, demonstrate better results in younger patients, shorter time to surgery and shorter nerve gaps and repair without tension.
    Although most reconstructive surgeons reverse their nerve grafts for reasonable concerns about axon escape through side branches, evidence for better outcomes in reversed grafts is lacking.
    Pederson WC, Median nerve injury and repair.J Hand Surg Am. 2014 Jun;39(6):1216-22.
    2. Ruijs AC, Jaquet JB, Kalmijn S, Giele H, Hovius SE. Median and ulnar nerve injuries: a meta-analysis of predictors of motor and sensory recovery after modern microsurgical nerve repair.
    3. Kallio PK, Vastamäki M. An analysis of the results of late reconstruction of 132 median nerves. J Hand Surg Br. 1993 Feb;18(1):97-105.
    4. Kalomiri DE, Soucacos PN, Beris AE. Nerve grafting in peripheral nerve microsurgery of the upper extremity. Microsurgery. 1994;15(7):506-11.
    5. Roberts SE et al. To reverse or not to reverse? A systematic review of autograft polarity on functional outcomes following peripheral nerve repair surgery. Microsurgery. 2017 Feb;37(2):169-174. doi: 10.1002/micr.30133. Epub 2016 Dec 9.

    Reference

    • orthoracle.com

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