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Excision of a sural nerve end neuroma and application of a Polyganics NeuroCapTM

    Overview

    Learn the Excision of a sural nerve end neuroma and application of a Polyganics NeuroCapTM surgical technique with step by step instructions on OrthOracle. Our e-learning platform contains high resolution images and a certified CME of the Excision of a sural nerve end neuroma and application of a Polyganics NeuroCapTM surgical procedure.
    The sural nerve is a common donor site for autologous nerve grafting for peripheral nerve defects. It is harvested from the lower leg from the midpoint of the upper calf to the lateral ankle mid way between the posterior aspect of the lateral malleolus and the Achilles tendon. When harvested the proximal end is usually cleanly transected and left deep to the deep fascia to reduce the risk of a symptomatic end neuroma formation.
    In this case the patient had trauma to the right forearm following a road traffic collision and the sural nerve harvest was for reconstruction of the posterior interosseus nerve as three reversed cable grafts for extensor carpi ulnaris, finger extension and thumb extension. Three years later he represented with pain in the posterior calf worse when lying supine in bed with sleep disturbance. A diagnostic local anaesthetic block under ultrasound confirmed excellent pain reduction and he was consented for exploration and neroma resection and application of a Polyganics bioresorbable PCL NeuroCapTM.

    Indications

    INDICATIONS
    The indications for exploration of a neuroma are neuropathic pain with neurostenalgia (tether pain) following trauma to a peripheral nerve. This should not be responsive to conservative management with analgesia, neuromodulator medication, desensitisation exercises and other strategies including mirror therapy. There should also be a good response to targeted peripheral nerve local anaesthetic blockade with a pain reduction of at least 50% on a visual analogue scale. The decision to use a NeuroCap should be for the management of an end neuroma following nerve transection or amputation. The NeuroCap can also be used for the management of a neuroma in continuity in sensory nerves where there is no distal sensory preservation and there is a contraindication to reconstruction such as a poor surgical bed that is unlikely to provide a favourable environment to support regeneration through a nerve graft.
    In this case there was a history of chronic neuropathic pain at the site of sural nerve harvest for autologous reconstruction of a nerve gap in the upper limb.
    SYMPTOMS & EXAMINATION
    The patient reported pain in the posterior calf on lying supine. There was a palpable 1cm firm spherical swelling at the site of reported pain at the upper end of the previous surgical scar. There was a positive Tinel’s sign (pain and dysaesthesiae in the distribution of the sural nerve) on gently tapping over the swelling. There was hypoaesthesia in the distal cutaneous territory of the sural nerve.
    IMAGING
    Ultrasound is a useful investigation to define the site of a neuroma where the clinical examination is equivocal. Some patients do not tolerate the pressure required from the ultrasound probe for this investigation due to allodynia. In this case the previous surgery, palpable swelling and positive Tinel’s sign precluded the need for further imaging.A diagnostic nerve block with local anaesthetic and a visual analogue pain score (VAS 0-100mm) are useful to confirm a positive pain reduction response prior to consideration of surgical excision.
    ALTERNATIVE OPERATIVE TREATMENT
    There is no single satisfactory solution for the definitive management of a painful neuroma. In a neuroma in continuity for a critical nerve, sensory restoration through excision of the neuroma and nerve grafting may reduce neuroma pain. Restoration of pain to anaesthetic skin may modulate pain pathways centrally. Using a processed nerve allograft for this reconstruction may confer advantages over autologous nerve grafting as the latter creates another sensory nerve injury (albeit a controlled surgical insult) to a nerve in a pre-sensitised individual.
    In many situations there is an end neuroma or the surgical bed is too poor to sustain revascularisation and nerve regeneration through a nerve graft. Many operations have been described for end neuromata including simple transection of the nerve and removal of the neuroma. Regrowth and tether of the cut nerve end in scar is very common and therefore repositioning the proximal end to deeper tissues including bone and muscle is often recommended. The aim of this intervention is to provide more padding around the nerve end to prevent mechanical irritation and the healthier tissues should be better vascularised and prevent nerve tether to mobile cutaneous tissue. Allograft can be used to redirect regenerating nerve proximally or directly in to muscles in situations where the anatomy precludes direct deeper relocation of the nerve end following end neuroma resection. Polyganics have developed a bioresorbable polycaprolactone nerve capping device (the NeuroCap) that is designed to cover the nerve end following neuroma resection. The device has a chamber for nerve regrowth but the nerve is prevented from adherence to scar by a physical barrier which slowly changes to a hydrogel and is ultimately completely resorbed over 18 months.
    The NeuroCap was the treatment of choice for this neuroma in the sural nerve at the site of previous autologous nerve harvest.
    NON-OPERATIVE MANAGEMENT
    The management of neuroma pain is challenging. Patients frequently are prescribed increasing doses of systemic opioid medication with poor symptom relief. Neuromodulators including Pregabalin and Gabapentin may modulate the pain response through their effects on central pathways. The use of antidepressant medications can also help to modulate central pain perception and improve affect in patients with chronic neuropathic pain. Topical analgesics including local anaesthetic patches may help areas of cutaneous hyperaesthesia and local anaesthetic gels or creams may have the added benefit of facilitating local scar management to reduce nerve tether and desensitise nerve endings in the skin. Capsaicin patches are useful in areas of cutaneous hypersensitivity.
    Physical therapies including friction massage, desensitisation and neural glides are useful in the early stages of management of nerve pain at the site of a suspected neuroma.
    Nerve stimulation can modify the pain response and is the basis of transcutaneous electrical nerve stimulation (TENS) therapy.
    Spinal cord stimulation is an option for severe neuropathic pain management when other more conservative methods have failed and where there is no surgical target for the management of the neuropathic pain.
    Mirror therapy involves the use of masking of the affected limb and functional movement, tactile stimulation and massage of the contralateral normal limb with graduated introduction of tactile stimulation bilaterally to facilitate visual over riding of the pathological central nervous system pain pathways. This has demonstrated benefit in the management of phantom limb pain after amputation and in the rehabilitation after peripheral nerve injury and stroke.
    CONTRAINDICATIONS
    The NeuroCap is contraindicated in active infection, poor surgical beds or hypersensitivity to polycaprolactone. The NeuroCap is limited to 8mm diameter nerve stumps and the stump should be measured so that an appropriate sized device can be used for each nerve. The nerve stump should have sufficient length that it can be mobilised and introduced to the cap with a 5mm distal void to allow for unsupported nerve regeneration. The device must be anchored loosely to a deep tissue plane to prevent superficial migration and the risk of wound irritation or extrusion. The soft tissue cover should adequate to pad the area as the NeuroCap may be palpable for a few months. Caution should be exerted in the surgical management of neuromata where there is only a poor response to pre-operative local anaesthetic nerve blockade. In such cases the pain may have significant central modulation that will result in a poor response to surgical intervention in the periphery.

    Setup

    The patient was consented for exploration under general anaesthesia and the neuroma site and limb are identified with a permanent skin marker.
    Antibiotics were administered after induction to cover insertion of the prosthetic NeuroCap device.
    He was positioned in the lateral position with shaving of the skin at the site of surgery on the posterior calf. A tourniquet was applied with padding to the mid thigh.
    The skin was prepared with an alcoholic disinfectant and draped above the knee using a limb pack, leaving the whole lower leg, foot and ankle exposed.
    Exsanguination was achieved with elevation and application of an Esmark bandage and the tourniquet was inflated.
    Basic instruments are required with a Mixter forceps, surgical rubber sloops and a self-retaining Travers retractor.
    Microinstruments and an operating microscope are required for neuroma resection and application of the NeuroCap.

    Operation – 1

    The patient is positioned in the right lateral decubitus position exposing the posterior aspect of the left lower leg. The neuroma site is marked with a circle and cross at the point of maximum Tinel’s sign.
    The right leg has a TED stocking applied and a FlotronTM pneumatic device to provide a mechanical eans of preventing venous stasis.
    Gel heel pads are positioned at the ankles and a pillow is placed between the knees and thighs with a tourniquet applied to the left med thigh to facilitate exposure with minimal bleeding.

    After elevation and exsanguination the skin is prepped and draped with a limb pack.

    The site of the neuroma is palpated and marked again with a permanent marker pen.

    The neuroma is palpable at the upper end of the old surgical scar. The line of the sural nerve is marked to the midpoint of the gastrocnemius muscles at the lower margin of the popliteal fossa.

    The line of the planned incision is marked over the course of the sural nerve to facilitate exposure and ensure that the neurectomy can be sited deep to the deep fascia in the upper calf.

    The skin is incised in the line of the marking.

    The superficial dissection is performed using monopolar diathermy and an epitome blade.

    A toothed “cat’s paw” retractor is used to retract the upper skin end. The diathermy is used to deepen the wound to the sural nerve and the adjacent short saphenous vein.

    Once the nerve or vein are identified tenotomy scissors are used to widen the zone of dissection and identify the key structures.

    Bipolar diathermy is used to coagulate the side branches o fthe short saphenous vein that cross the sural nerve. Care should be taken to prevent inadvertent sectioning, traction or diathermy injury to any cutaneous nerve branches in the vicinity.

    The sural nerve is now identified proximal to the neuroma site and mobilised using Jamieson scissors.

    A pair of 90 degree tipped fine Mixter forceps are passed deep to the sural nerve to facilitate passage of a surgical rubber sloop.

    A red sloop is placed in the jaws of the Mixter to ensure that it can be readily passed deep to the sural nerve without snagging the deep surface.

    The sloop is passed under the sural nerve. This can be used to provide gentle traction on the nerve to facilitate dissection and neurolysis.

    The sloop is used to put traction on the sural nerve to minimise handling during dissection.

    DeBakey forceps are used to handle the epineurium when necessary. These are relatively atraumatic and reduce the risk of creating a site of injury that could result in a neuroma in continuity of the sural nerve above the site of neuroma excision. The dissection of the sural nerve from the bed and the adjacent short saphenous vein continues in a proximal direction.

    Traction on the sloop facilitates the neurolysis and dissection.

    A West self-retaining retractor is placed in the distal part of the wound and two toothed retractors are placed in the proximal wound to facilitate exposure of the sural nerve and trace it deep to the deep investing fascia of the calf. The neurectomy should be positioned deep to the deep fascia to reduce the risk of proximal stump tether to the site of the surgical scar.

    The self-retaining retractor is reversed and the sloop used to provide traction on the distal nerve as is forms a neuroma and is tethered in scar.

    Two Langenback retractors allow exposure of the neuroma and neurolysis from scar. A tributary of the short saphenous vein is seen crossing the proximal neuroma.

    The sural neuroma is dissected free from its bed around its circumference using Jamieson scissors. A sloop provides gentle traction on the nerve.

    A Mixter is passed deep to the neuroma to enable placement of a second sloop to allow traction on the distal tether point of the neuroma in the old surgical scar.

    The second red sloop is in position distal to the neuroma in the sural nerve passed around the scar to the surgical bed.

    Traction on the distal sloop allows the scar tether to be visualised and sectioned with the Jamieson scissors.

    The neuroma and the sural nerve are dissected free from the scar and the surgical bed in a distal to proximal direction. DeBakey forceps are used to handle the nerve. The prior performance fo the circumferential neurolysis using sloop retraction means that this step can be accomplished quickly and with minimal trauma to the nerve.

    Operation – 2

    The scar, neuroma and sural nerve in continuity lying in the wound after removal of the sloop.

    Proximal neurolysis is completed deep to the investing fascia of the lower leg.

    The sural nerve is being mobilised and prepared for the neurectomy which will be performed at the site demonstrated by the surgeon’s finger.

    The neurectomy is performed with sharp transection of the sural nerve with Jamieson scissors under gentle traction.

    The neurectomy is performed with sharp transection of the sural nerve with Jamieson scissors under gentle traction. The distal stump with neuroma can be sent for histopathological analysis is necessary. This may be indicated if pathology is uncertain or in cases of iatrogenous nerve injury. It is not indicated in this scenario.

    The proximally sectioned end of the sural nerve lying in the wound ready for capping.

    The resected specimen demonstrating scar tether point, neuroma and proximal sural nerve resected in continuity with neuroma to facilitate capping deep to the deep fascia more proximally in the calf.

    The Polyganics Neurocap is made from a bioresorbable polymer Poly-DL-Lactide-co-caprolactone (PLC). This polymer udergoes hydrolysis in vivo and the bi-products are metabolised and excreted. The device provides a chamber to enclose the cut nerve end for 3 months after surgery and prevents scar tether of the cut nerve end. The device is fully resorbed by 18 months after implantation.
    A 3.5mm diameter NeuroCap was selected after measuring the diameter of the sectioned sural nerve.
    The cap is provided in a tray and this should be carefully opened and the device soaked in warm saline at 37 degrees to soften the device and improve handling properties.

    The NeuroCap is trimmed to the desired length for the indication and position chosen for cap placement. The ideal is for 6-8mm of nerve stump containment with a chamber of approximately 5mm to allow for unsupported neuroma outgrowth.

    Injection of saline to the lumen facilitates passing the needle and introducing the nerve stump.

    The NeuroCap prepared for introduction of the nerve stump.

    An 8’0 nylon suture is used to pass through the NeuroCap and then through the epineurium of the nerve stump approximately 5mm fromthe cut end then back through the cap exiting adjacent to the first suture position. A tungsten needle is preferable as it is stronger than the ususal 8’0 nylon suture needle, but with care the standard Ethicon needle will suffice.

    The suture is delivered back through the NeuroCap.

    The cut end of the proximal nerve is introduced to a 3.5mm NeuroCap using the mattress suture.
    A chamber of at least 5mm should be left as a void between the nerve stump and the end of the NeuroCap to allow for axon sprouting.

    The suture is tied to leave the nerve stump within the cap with a void beyond for regeneration.

    A second suture can be used to secure the cap inserted in the same way at 180 degrees from the first.

    A void of at least 5mm beyond the nerve stump is ideal.

    The cap is positioned deep to the deep fascia. Note the small cutaneous branches from the proximal sural nerve. care should be taken to avoid damage to these branches.

    There is a suture hole at the tip of the NeuroCap that may be used to anchor the cap deep to the fascia to prevent superficial migration to the wound. In this case a vicryl suture is being used to anchor the device. This should be done without kinking the nerve or undue tension.

    The final position of the NeuroCap buried and anchored deep in the wound.

    The self-retaining retractor is removed and the wound is irrigated in preparation for closure.

    Local anaesthetic is injected around the proximal sural nerve to reduce the post-operative neuropathic pain.

    Interrupted 3’0 vicryl sutures are used to oppose the wound edges.

    Completion of the interrupted vicryl sutures.

    The wound is ready for the continuous subcuticular monacril monofilament absorbable 3’0 suture.

    Operation – 3

    Tying the know on the monacril subcuticular suture.

    The final wound after closure.

    Steristrips are placed to support the wound.

    Local anaesthetic is injected along the wound edges.

    An occlusive dressing is applied to the wound.

    Gauze padding to the dressing.

    A bulky, supportive wool and crepe dressing is applied to the lower leg.

    Post Operative

    Surgery is performed as a day case unless there is debilitating neuropathic pain and concerns regarding management of post-operative pain. In such cases I would advise admitting the patient and leaving an indwelling nerve catheter adjacent to the proximal sural nerve so that a background local anaesthetic infusion and intermittent boluses can be delivered for 1-2 days post-operatively.
    The patient is advised to elevate the limb for 48 hours after surgery.
    I usually recommend continuation of usual pain medications and neuromodulators for at least 6 weeks following surgery before controlled reduction. This strategy reduces the risk of a pain flare response form surgery and nerve manipulation in sensitised individuals.
    Dressing reduction can be undertaken at 5-7 days and the wound can be left open from 2 weeks with advise on scar massage from 3 weeks.
    The patient can full weight bear mobilise after surgery.

    Recommended Reading

    NeuroCap results
    The patient should have a visual analogue score monitored pre-operatively, after the diagnostic block and at intervals of 3,6,12 and 24 months post-operatively. The outcome of neuroma surgery is variable. Careful pre-operative patient assessment and selection is key to good results.
    References:
    Van Der Avoort DJJC, Hovius SER, Selles RW, Van Neck JW, Coert JH. The incidence of symptomatic neuroma in amputation and neurorrhaphy patients. J Plast Reconstr Aesthetic Surg. 2013;66(10):1330-1334
    Stokvis A, van der Avoort D-JJC, van Neck JW, Hovius SER, Coert JH. Surgical management of neuroma pain: a prospective follow-up study. Pain. 2010;151(3):862-869
    Lewin-Kowalik J, Marcol W, Kotulska K, Mandera M, Klimczak A. Prevention and management of painful neuroma. Neurol Med Chir (Tokyo). 2006;46(2):62-67; discussion 67-68
    Watson J, Gonzalez M, Romero A, Kerns J. Neuromas of the hand and upper extremity. J Hand Surg Am. 2010;35(3):499-510
    Elliot D, Sierakowski A. The surgical management of painful nerves of the upper limb: a unit perspective. J Hand Surg Eur Vol. 2011;36(9):760-770

    Reference

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