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Carpal tunnel decompression- Revision and application of Polyganics Vivosorb membrane

    Overview

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    Carpal tunnel results from compression of the median nerve on the volar aspect of the wrist. Decompression is a successful operation when performed for the appropriate indication, when the nerve is completely released and when there is no impairment of nerve glide in the post-operative period.
    Persistent carpal tunnel symptoms are associated with incomplete decompression and recurrent symptoms after an interval of 3 months or more are usually associated with a degree of scar formation causing further compression or resulting from nerve tether. The rate of failed primary carpal tunnel decompression is approximately 1:20. This figure includes those with significant persistent symptoms or new symptoms after surgery, incorrect diagnosis, contributing concomitant cervical radiculopathy and a failure to manage the patient’s expectations when there is severe nerve dysfunction. The rate of recurrent carpal tunnel syndrome requiring revision decompression within 10 years of the primary procedure is an additional 1:20. Recurrence rates are higher in diabetic patients due to nerve susceptibility to compression and a tendency to develop thickened chronic tenosynovium around the flexor tendons within the carpal canal. Recurrence is also common in women with low body mass index, possibly due to the decreased subcutaneous adipose tissue that otherwise fills the void left after flexor retinaculum (FR) release. The post operative healing in such cases includes rapid reforming of the FR which results in the recurrent compression. Patients with Hereditary Neuropathy with sensitivity to Pressure Palsies (HNPP), a genetic condition, are prone to multiple peripheral nerve compressions and recurrent compression after release. Patients with complications from primary surgery including infection may have impaired nerve glide and develop persistent or recurrent symptoms after primary release.
    One of the causes of failed carpal tunnel decompression (CTD) is scarring of the median nerve paraneurium that impairs physiological nerve glide. Revision CTD may require the use of an adjunct barrier to prevent scar formation resulting in recurrent nerve tether. There are a number of biological and synthetic alternatives. The Vivosorb is a bioresorbable polymer layer that can be sutured loosely around a scarred nerve to prevent scar tether in the surgical bed, maintain nerve gliding and prevent recurrence of compression.
    Readers will also find the following associated techniques of interest:
    Extended approach Carpal Tunnel decompression
    Carpal tunnel decompression
    Combined median and ulnar nerve decompressions
    Median nerve neurolysis, resection and reconstruction using Axogen AVANCE processed nerve allograft

    Indications

    INDICATIONS
    Carpal tunnel results from compression of the median nerve on the volar aspect of the wrist. Decompression is a successful operation when performed for the appropriate indication, when the nerve is completely released and when there is no impairment of nerve glide in the post-operative period.
    Persistent carpal tunnel symptoms are associated with incomplete decompression and recurrent symptoms after an interval of 3 months or more are usually associated with a degree of scar formation causing further compression or resulting from nerve tether. Revision surgery may require use of an adjunctive barrier to prevent recurrent scar formation. The Polyganics VivosorbTM is a bioresorbable polymer membrane that may be placed around the nerve following neurolysis. The membrane hydrolyses and is reabsorbed over several months, allowing nerve glide without tether from scar that forms in the immediate post-operative period.
    SYMPTOMS & EXAMINATION
    Carpal tunnel symptoms include paraesthesiae in the thumb, index, middle and radial aspect of the ring finger on the volar surface. Numbness may result from prolonged or severe compression. In severe cases there is wasting and functional loss of the thenar muscles with resultant loss of opposition.
    Typical primary carpal tunnel syndrome (CTS) includes night symptoms with waking from sleep and morning numbness or paraesthesiae that may be alleviated with hand shaking or dependency of the affected limb.
    Following previous surgery, persistent symptoms suggest incomplete decompression or poor residual function in a nerve that has had severe compression with axonal loss and intra-neural scar formation. Recurrent symptoms after an interval with symptom improvement or resolution suggests that scar has formed around the nerve causing recurrent compression.
    Pain exacerbated by passive extension off the fingers or wrist is termed neurostenalgia. This examination finding is suggestive of extrinsic scar that is tethering the nerve and preventing normal physiological glide.
    I assess for a Linburg-Comstock anomaly in cases of previous failed carpal tunnel decompression (CTD). The anomaly is a developmental or acquired tether between the flexor pollicis longus (FPL) and the index finger flexor digitorum profundus (FDP) in the distal forearm. In such cases there is chronic inflammation and thickened tenosynovial proliferation as a result of differential glide against the tether point. The overlying median nerve becomes adherent and encased in thickened tenosynovial fibrotic scar as a result and traction neurirtis is experienced during differential tendon action. The symptoms are deep volar radial wrist sharp pain and median nerve “electric shocks” elicited by extension of the index finger with the thumb actively flexed across the palm.
    A Tinel’s sign may be elicited in recurrent CTS or failed primary CTD by tapping along the course of the median nerve in a distal to proximal direction. The patient reported “electric shocks” or parasthesiae in the cutaneous territory of the median nerve when the tapping is at the point of maximal scar or compression. This site should be marked with a cross prior to surgery to guide the surgeon to the target area.
    IMAGING
    Ultrasound imaging may identify impaired nerve glide, a swollen nerve proximal to the compression and abnormal carpal tunnel contents including tumours, ganglia or tenosynovium. In practice I do not usually request imaging because the important features may be elicited through careful and systematic clinical examination.
    Magnetic Resonance Imaging (MRI) may be used to identify other pathology around the carpal tunnel or within the carpus. MRI may identify accessory tendon slips in the FPL – FDP index interval. In practice I do not request imaging unless there is some diagnostic uncertainty remaining after the clinical examination.
    NEUROPHYSIOLOGICAL INVESTIGATIONS
    Neurophysiology studies are essential in the diagnosis of recurrent or failed CTS. I request access to any previous investigations from prior to the primary surgery in addition to previous outpatient records and operation records. The neurophysiology should be repeated to include conducting tin velocity, amplitude, latency and electromyographic (EMG) recording from the thenar muscles.
    The severity of the primary CTS diagnosis can be ascertained from the original studies and the repeat will detail any interval improvement, persistence or deterioration. The repeat studies also allow a re-grading of the severity for prognostic reasons.
    EMG sampling can identify acute of chronic denervation within the motor axons of the median nerve and any recovery from the prior surgery. In cases with active denervation of the thenar muscles, the motor branch of the median nerve must be identified at surgery and traced through scar and released all the way to where it enters the thenar muscles.
    ALTERNATIVE OPERATIVE TREATMENT
    The standard approach for failed, recurrent or persistent CTS is a revision CTD with a more extensive approach and external neurolysis of the median nerve. In cases of severe scarring there are autologous flaps that can be rotated and placed around the nerve to cushion it and provide a barrier to further scar formation. Scar at the undersurface of the flexor retinaculum or at the site of the previous exposure can be treated with a pedicled flap of hypothenar fat tissue. The hypothenar fat flap is successful in treating localised scarring but is insufficient when there is extensive scar throughout the course of the median nerve in the distal forearm to the common digital nerve branch points.
    Larger autologous tissue flaps include the Becker flap based on the dorsal ulnar artery perforator in the distal forearm. This flap can allow distal pedicled rotation as a “propellor” flap of skin and subcutaneous fat and fascia or fat and fascia alone. The tissue can be placed over the nerve to resurface the nerve or in cases of adipofascial flap alone, the nerve can be loosely wrapped in the flap to prevent tether to skin or the deeper flexor tendons.
    A distally-based perforator flap can be elevated from the radial artery in the distal forearm and rotated in the same way with skin and subcutaneous tissues or adipofascial tissues alone. The flap is used in the same way as the B~ecker flap to protect, wrap or resurface the median nerve. The limitation of the radial forearm perforator flap is the proximity to the lateral cutaneous nerve of forearm nerve branches which are close to the radial side of the flap and these branches may be injured or scarred from this approach, creating a new source of nerve pain.
    There are alternative commercial devices available for nerve protection after neurolysis. The VivosorbTM is a bioresorbable polymer membrane. ~Collagen barriers are available including the AxoGuardTM nerve protector which is a porcine layered extracellular matrix collagen sheet. This revascularises well and allows restoration of nerve glide. the AxoGuardTM may not be acceptable to some patients due to its animal origin.
    All nerve wraps may be associated with recurrent junctional scar at the area where the wrap ends within the surgical bed. tether can occur to the nerve epineurium in the area not covered by the wrap.
    NON-OPERATIVE MANAGEMENT
    The role of conservative management is limited. Recurrent CTS may be assessed with a response to steroid injection and splint age. However there is poor spread of steroid in the presence of scar and there is a risk inadvertent intraneural injection due to tether of the nerve and adherence to the under surface of the flexor retinaculum. These conservative measures will not bee able to alleviate the constricting scar or scar tether points, but temporarily may reduce symptom severity due to resting the area. Topical massage at the scar can reduce scar sensitivity and allow maturation if collagen in the cutaneous scar. I do not advise prolonged conservative management in the setting of nerve pain, clinical nerve tether and neurophysiological evidence of deteriorating nerve function. In such cases surgery should be recommended and undertaken promptly.
    CONTRAINDICATIONS
    There are few contra-indications to implantation of a VivosorbTM membrane. A history of previous wound infection is a relative contra-indication. In such cases where there is no active infection, I would counsel the patient regarding the risks and if acceptable then I would cover the implantation with intravenous antibiotics. In cases with recent infection and concern regarding recurrent infection around the implant, then a biological autologous vascularised flap may be indicated.

    Setup

    For cases of revision CTD I use brachial plexus regional block anaesthesia. The block is preformed under ultrasound guidance with a combination of local anaesthetic agents to provide a rapid onset and sustained anaesthesia that provides an extended post-operative block for between 8 and 12 hours. When the block is performed at the level of the upper arm a supplementary subfascial block is required to anaesthetise the skin supplied by the intercostobrachial nerve and the medial cutaneous nerve of the arm. The addition of this block ensures that a pneumatic tourniquet can be placed around the upper arm without discomfort should if be required for more that 60 minutes.
    Antibiotics are administered intravenously to cover common skin commensals in advance of the tourniquet insufflation. The antibiotics are used due to the planned implantation of a scar barrier membrane around the nerve.
    The regional block allows exploration of the site of revision carpal tunnel decompression with a bloodless field. Additionally, the duration of the block ensures that there is sufficient time for a complete neurolysis of the median nerve and if necessary a tenosynovectomy of the flexor tendons.
    A “lead” hand is needed to position the hand for surgery. I use a Mixter to pass sloops around the nerve for retraction. The neurolysis is performed with sharp dissection using a scalpel and multiple blades are needed when there is extensive scar. I would not typically use a nerve stimulator, although it can be of use when there is severe scar around the motor branch to identify the motor branch and any improvement in stimulation thresholds after decompression and neurolysis.
    The surgical dissection is performed with loupe magnification. I use a 3x magnification for the exposure and an operating microscope if there is epineural scar to be excised, or when there is a need for internal interfascicular neurolysis in severe cases with “hourglass” constriction of the nerve.
    I use a monofilament proline 6’0 suture to secure the VivosorbTM around the nerve at the time of surgery.

    Operation – 1

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    The case illustrated is recurrent carpal tunnel compression associated with a malunion of distal radius fracture
    The case illustrated is of a recurrent CTS associated with a mal-union of the distal radius. The distal radius fracture was many years previously and the wrist movements are full and painfree with some remodelling at the distal radio-ulnar joint. As a result there is no reason to correct the wrist alignment. The carpal tunnel mouth will be narrowed and there is tether of the median nerve in scar the wrist crease. There is pain on passive digital extension with reproduction of “electric shocks” and parasthesiae on digit and wrist extension. Scar tether around the median nerve is clinically suspected.
    There may have been an injury to the median nerve at the time of the original wrist fracture with a resultant neuroma in continuity of the median nerve. The function was improved after the original injury and the CTD and has deteriorated. As such the function was deemed too good to consider excision and grafting of a neuroma in continuity. Simple revision CTD was planned with neurolysis and wrapping of the nerve to prevent recurrent scar tether.
    The patient didn’t want to have implantation of an animal product. The option of an autologous flap to protect the nerve at the tether point was given, however the patient opted for the bioresorbable polymer, if deemed necessary after exploration, because he was keen to avoid further scars in the forearm skin.
    The World Health Organisation (WHO) checklist is completed and the site and procedure confirmed with the theatre team, surgeon and scrub nurse.

    There is a trophic burn to index finger associated with the median nerve sensory loss
    The severity of the median nerve dysfunction is demonstrated by the trophic ulceration off the index finger. the patient has experienced a contact thermal injury and without protective sensation the skin was damaged. The aim of this operation is to decompress the median nerve and to allow return of protective sensation to the median innervated area of the hand.

    The site of maximum Tinel intensity is marked with a cross, prior to anaesthesia.During the pre-operative assessment, I mark the site of maximum Tinel’s intensity. Typically this correlates with the point of maximum scar tether or constriction and the nerve should be identified proximal to this area and traced into this zone to avoid inadvertent injury due to distorted anatomy and impaired visualisation off the nerve in scar. In this case, the Tinel’s point correlated with the distal radius mal-union and the site of nerve constriction at the distal ante brachial fascia where the nerve passes towards the mouth of the carpal tunnel.

    Following skin preparation and draping, the incision site is marked.-DESCRIBE LINE OF INCISIONThe planned site of incision is marked
    The exposure for a revision CTD requires safe exposure of the nerve through the previous surgical site and a longer incision is necessary to identify the nerve proximally in a bed without scar.
    A “V” extension is made across the volar wrist crease to expose the median nerve deep to the ante brachial fascia in the distal forearm.
    A”STOP” moment is undertaken just prior to incising the skin to confirm the procedure and site of surgery.

    The skin in the palm is incised over the carpal tunnel.The skin is incised in the line of the skin markings. The surface landmarks for incision are in the line of the radial border of the ring finger. The previous palm incision was in the appropriate position and this part is re-opened.

    The skin incision is extended proximally across the wrist crease into the forearm along the line of the “V” markings to cross the wrist crease at an angle.This reduces the risk of scar placement directly over the nerve, minimises the risk of injury to the palmar branch of the median nerve and prevents longitudinal scar contracture due to the forces created through wrist extension.

    The superficial dissection should expose the palmaris longus tendon in the distal forearm.The palmaris longus is a key landmark for the carpal tunnel release. the carpal tunnel should be released along the ulnar border of the PL tendon to avoid leaving a scar directly over the median nerve. An incision too ulnar may open Guyon’s canal and risk injury to the ulnar nerve or artery. An incision too radial risks injury to the median nerve or the palmar branch of the median nerve.

    Bipolar cautery is used to control bleeding from the superficial veins.

    The palmaris longus tendon is mobilised to expose the ante-brachial fascia beneath.The palmaris longus (PL) tendon inserts into the palmar aponeurosis overlying the flexor retinaculum (FR). The tendon is identified and the exposure is performed along the ulnar side of the tendon to expose the FR and the distal forearm antebrachial fascia which hasn’t previously been released.

    The superficial dissection is completed to expose the antebrachial fascia in the forum, the flexor retinaculum (FR) and the scar at the previous site of FR release.

    The ante brachial fascia is released in the distal forearm as far as the proximal edge of the flexor retinaculum, following which the median nerve is visible in the distal forearm.The ante brachial fascia is the enclosing deep fascia of the forearm. This is incised along the ulnar border of the PL tendon to expose the deeper structures including the median nerve.

    Following full release of the ante brachial fascia, the median nerve is visible in the distal forearm.
    Exposing the median nerve in the distal forearm allows safe distal exposure in the scarred bed from the previous CTR. The median nerve may be compressed at the distal forearm fascia. In this case the Mal-union of the distal radius has resulted in compression of the nerve under the ante brachial fascia.

    Dissection along the radial side of the median nerve is required to expose the palmar branch of the median nerve, which sits in the interval between the median nerve and the FCR tendon.The median nerve lies in fat deep to the flexor digitorum superficially and emerges superficially at the wrist crease between the PL and the fCR tendons. on the radial aspect of the median nerve lies the palmar branch. This can be identified and protected during the distal exposure at the level o the wrist crease.

    The palmar branch of the median nerve is identified in the interval between the median nerve and the FCR tendon.
    The palmar branch of the median nerve is exposed in the distal forearm and lies between the median nerve and the fCR tendon.

    The median nerve is mobilised in the distal forearm.The median nerve is identified in the proximal surgical wound. The nerve is less compressed or tethered at this point which is outside the field of the primary surgery. the nerve is mobilised using carful dissection with the tips of Jamieson scissors which are used to develop the plane around the paraneurium. The neurolysis should be 360 degree circumferential around the median nerve. Carefully dissect on the radial side of the nerve because the palmar branch of the median nerve arises from the median nerve in this area 50mm from the volar wrist crease. The palmar branch then runs in the plane alongside the median nerve between the nerve and the Far tendon towards the wrist crease where is pierces the deep fascia to enter the subcutaneous tissues over the theta eminence.

    A Mixter passed deep to the median nerve in preparation for passing a sloop.A Mixter (90 degree tipped fine clip) is passed deep to the median nerve to allow passing of a silicone elastic sloop for nerve retraction.

    The Mixter should pass through a pre-prepared passage deep to the nerve.

    A sloop is introduced to the Mixter jaws.Sloop is passed to the tips of the Mixter. Avoid opening the Mixter more than that necessary to introduce the sloop. Too much opening risks the dorsal aspect of the median nerve becoming caught unsighted in the Mixter jaws. Note how the Mixter is rotated to allow one pdf the arms to contact the dorsal Aspe t of the median nerve rather than the space between the two arms of the Mixter.

    The sloop is precisely positioned in the jaws of the Mixter too ensure that it is flush with the superficial aspect of the Mixter tips. This ensures that there is no prominent edge to snag on the dorsal aspect of the median nerve as the Mixter is retrieved from deep to the median nerve.

    The sloop is safely retrieved and passed around the median nerve in the distal forearm.The sloop is now pulled around the nerve and the Mixter removed. This method of positioning a sloop is precise and necessary. Although the median nerve may be more robust than some nerves, any unnecessary traction of risk of crush entrapment in the jaws of instruments is avoided. The sloop is used to gently retract the median nerve to assist with neurolysis.

    Following tagging of the median nerve in the distal forearm, the flexor retinaculum is divided in line with the skin incision in the palm.The scalpel, with a number 15 blade, is used to release the flexor retinaculum down to the nerve epineurium.
    There may be scar onto the nerve and two the position of the nerve shoulder be constantly checked and the sloop can be used to provide a gentle retraction during the nerve exposure.

    The flexor retinaculum is divided from proximal to distal towards the superficial palmar arch.Sharp dissection is continues distally to release the FR and expose the median nerve in the carpal tunnel. The distal flexor retinaculum edges converge until fully released, when they take on a parallel configuration. In the fat at the distal edge of the flexor retinaculum lies the superficial palmar arch. this is the continuation of the ulnar artery from the Guyon’s canal. It crosses obliquely from ulnar proximal to radial distal across the proximal mid palm, providing common digital arteries to each web space. The superficial palmar arch forms an anastomosis with the superficial branch of the radial artery. The dominant arterial supply to the superficial palmar arch is the ulnar artery.

    The median nerve is mobilised in the carpal tunnel using a sloop for retraction to assist with the neurolysis that is performed.The deep surface if the median nerve is adherent to scar at the wrist crease. The sloop can be used to retract the nerve. Here the closed fine toothed Adsons forceps are used to push the nerve and maintain tension in the paraneurial tissue which is incised along the edge of the epineurium. If the nerve is to be handled I prefer to use DeBakey forceps without teeth to pick up the epineurium. These forceps are less traumatic to the delicate tissues of the nerves than fine toothed Adsons forceps.

    The palmar branch of the median nerve is identified in the distal exposure.Neurolysis of the median nerve within the carpal tunnel allows it to be fully mobilised and retracted with the sloop.
    The radial side of the nerve is exposed. In the distal carpal tunnel the motor branch of the median nerve will be seen leaving the radial aspect of the median nerve. This part of the procedure requires great care in a revision case to identify and then safely release the motor branch in scarred tissues.
    The motor branch of the median nerve has a variable course and these variations must be considered during the exposure to avoid inadvertent iatrogenic nerve injury.
    The commonest finding is a true recurrent motor branch which arises from the radial aspect of the median nerve and then crosses the distal FR or pierces the distal edge of the FR to enter the thenar muscles. A proximal motor branch piercing the mid FR is rare but liable to injury.
    The motor branch must always be visualised in a revision CTD. In a primary case I note the position of the motor branch but I will only dissect and release the motor branch when there is thenar muscle wasting.

    Once the median nerve is fully released it is inspected for signs of compression. Here it can be seen to be swollen proximal to the point of maximum compression.
    The neurolysis has been completed for the main median nerve and the swelling of the nerve proximal to the carpal tunnel demonstrates how tightly compressed the nerve has been. In such cases the swelling is considered to be related to disruption of axoplasmic transport in the nerve.
    I sometimes have to consider release of the epineurium and minimal interfascicular decompression when there is full thickness scar and the epineurium is involved in the scar process.
    When the epineurium is involved and removed I would usually place a collagen nerve barrier around the nerve and I prefer the AxoGuardTM AxoGen Inc USA.
    In cases where there is an intact epineurium and there is scar between the nerve and adjacent structures, the use of a barrier and the choice of barrier type is less critical.

    Operation – 2

    The motor branch of the median nerve is identified in the distal and radial part of the carpal tunnel exposure.The motor branch is identified and a Mixter is passed deep to it to receive a sloop for identification and retraction for completion of the neurolysis

    A sloop is passed around the motor branch of the median nerve to enable further retraction and mobilisation.The red sloop is now positioned around the motor branch of the median nerve. The white sloop is around the proximal median nerve.
    The median nerve neurolysis has been completed and the nerve will be wrapped in a VivosorbTM membrane to reduce the risk of recurrent scar formation in the paraneurial tissues.

    The Vivosorb membrane is supplied refrigerated in a box detailing the dimensions and the expiry date.
    The Vivosorb is a thin flexible membrane manufactured from a polylactide of polycaprolactone. This polymer is bioresorbable, becoming hydrolysed and softening before full absorption within 18 months. The material should be stored in a refrigerator to maintain its shelf life. The membrane is provided sterile and comes in a box with inner pouch containing the sterile pouch and product.
    The VivosorbTM comes in a variety of dimensions. The 50mm x 70mm sheet is suitable for laying around the median nerve in an extended CTD from the distal forearm to the common digital nerve branching points.
    The VivosorbTM is part of the nerve repair portfolio of products manufactured by POLYGANICS BV, a Netherlands based biomedical polymer company.

    The VivosorbTM sheet is removed from the sterile packaging inside the box.
    The VivosorbTM is supplied on a thin sheet which is folded.

    The Vivosorb is introduced to the wound to ascertain the dimension required for coverage of the median nerve throughout the wound.The Vivosorb sheet can be applied straight out of the packaging. It is a thin sheet and handles well with relative flexibility. If it is too cold then it will appear stiff. In such situations pre-soaking of the sheet in warm saline is beneficial and improves the handling characteristics.

    Prior to use the VivosorbTM is soaked in warm saline which improves its handling characteristics.The Vivosorb is placed in a warm saline bath for 30 seconds. This allows the material to warm and soften which makes it more pliable. This improves the handling characteristics and allows easier placement around the nerve.

    The Vivosorb is lifted from the warm saline with toothed forceps. The membrane is opened to prepare for implantation around the nerve.

    The surgical bed is prepared for implantation. The white sloop allows the nerve to be lifted from the surgical bed to facilitate the passage of the membrane deep to the nerve, between the dorsal aspect of the median nerve and the underlying flexor tendons.

    A Mixter is used to pass the Vivisorb membrane deep to the median nerve.A Mixter is passed beneath the median nerve to receive the Vivosorb membrane.

    The Vivosorb membrane is placed deep to the median nerve. The position is adjusted to allow it to lie smoothly in contact with the epineurium. The sheet is a little too long in this case and cannot be positioned smoothly under the nerve. The sheet can be trimmed at this point to ensure that there is sufficient length to cover the nerve without redundancy.

    The Vivosorb membrane is trimmed to fit the whole exposed median nerve and then wrapped around itThe membrane has been trimmed to shorten it. This is then positioned smoothly along the deep surface of the median nerve.

    The VivosorbTM sheet is wrapped around the median nerve. Any excess width can be trimmed to allow loose wrapping around the median nerve to enable suture in place without excessive redundancy.

    The trimmed Vivosorb membrane sheet is sutured in place around the median nerve.The trimmed VivosiorbTM sheet is sutured in place with interrupted 6’0 prolene sutures.

    The sutures are placed along the open edge of the wrap to secure the membrane, prevent displacement and leave a gliding area around the nerve. The sutures are not placed in the epineurium in order to avoid nerve injury and scarring of the epineurium.

    Further sutures are placed along the open edge of the membrane to secure it in place.

    The Vivosorb membrane is secured in place with interrupted sutures to close the free edge of the wrapped nerve.The Vibosorb is sutured to itself, not to the nerve and not to the bed. This creates a cylinder of protection around the median nerve through which the nerve can glide.
    The membrane is now secured in place and nerve gliding can be confirmed prior to closure.
    The sloops are removed and the wound is irrigated prior to closure.

    The wound is closed after haemostasis.The wound is closed with interrupted prolene 4’0 sutures.

    interrupted sutures are useful should the patient develop a haematoma postoperatively. A single suture can be use and any haematoma expressed without oping the whole suture line.

    The palm may be closed with vertical mattress sutures. These allow eversion of the wound edges and prevent skin tethering.

    The wound is closed and ready for dressing application.

    The completed wound closure with interrupted sutures prior to application offthe dressings.

    A Mepitel sheet is applied to the wound after closure.A MepitelTM open weave surface dressing is apple dot the wound. The holes allow blood to escape to the overlying gauze pad dressing. MepitelTM isa low adhesive dressing that is easy to remove in the clinic.

    Gauze pads are applied to the wound dressing.A blue dressing gauze pad is applied to the wound dressing to absorb any blood that oozes from the wound.

    Further blue gauze is applied and loosely wrapped at the wrist. care should be taken to ensure that this isn’t applied too tightly to the hand and wrist because swelling will occur after the tourniquet release and in the post-operative period as a response to surgery.

    Operation – 3

    A wool bandage support is applied to the wrist and hand.Dressing wool bandage is applied over the wound dressing for support and protection.

    A loose crepe bandage is applied over the wool across the wrist and hand leaving the MCPJs free.A dry dressing is applied to the burn ulceration of the index finger. The surgical site dressing is completed with a loosely applied crepe bandage. The tourniquet is then released. The bandage should be checked after tourniquet release to ensure that is isn’t too tight as the bloodflow returns to the arm and the tissues swell.
    The bandage is secured with EastoplastTM tape.
    The arm is placed in a Bradford sling and elevated.
    Final theatre counts are completed and the “sign out” performed in line with the World Health Organisation (WHO) theatre checklist requirements.

    Post Operative

    The arm is elevated in a Bradford sling and the patient is observed for any bleeding of immediate swelling before discharge later the same day. Simple analgesics are prescribed and the patient os advised to take the first dose as soon as they feel the start of sensation returning to the hand as the brachial plexus block wears off.
    The patient is encouraged to mobilise the fingers and to gently mobilise the wrist.
    Introduction of light functional use of the hand at 24 hours post-operatively allows nerve glide and prevents tethering to the flexor tendons.
    In addition the use of the hand for gripping encourages a natural slight wrist extension which prevents the median nerve becoming tethered in the volar wound.
    Sutures are removed at 2 weeks and the patient is reviewed at 6 weeks and 3 months to ensure that there are no complications and that the symptoms have resolved.

    Recommended Reading

    The results of primary carpal tunnel decompression are generally predictable and good. Jeremy Bland has documented poorer outcome in cases where there is mild neurophysiological carpal tunnel or severe, perhaps representing diagnostic confusion in the former and severe nerve impairment in the latter. Outcome is less predictable in patients with diabetes and with peripheral neuropathy. Peripheral neuropathy is not a contra-indication to surgery however careful consideration should be given to severe compression cases with little preserved function who remain pain free because occasionally neuropathic pain may develop following decompression. The effects of scar pain and tenderness can be minimised with careful surgical technique avoiding injury to the cutaneous branches in the palm, early functional use of the hand, scar massage and desensitisation. Severe motor dysfunction with loss of thenar bulk does not recover with decompression and adjunctive tendon transfers should be considered in such cases to improve hand and thumb dexterity for opposition grip.
    The results of revision CTD surgery are more variable and reflect the diagnostic uncertainty, the nerve dysfunction and the presence of scar in the nerve bed, involving the epineurium and potentially intraneural scar. the reasons for revision need to be defined. Is it a true recurrent compression or is it a nerve tether or perhaps an unrecognised nerve injury.
    In persistent or recurrent compression there is approximately a 80% chance of symptom resolution or significant improvement. This is slightly less than the 90-95% successful primary decompression results.
    When there are new symptoms following primary release the possibility of a nerve injury renders the outcome less good in this group with 70% of patients benefitting from the revision surgery.
    When revision decompression has not resolved the symptoms, a further decompression is successful in only approximately 50% of cases.
    I therefore consider using an scar barrier when there is significant epineurium involvement in scar, scar tether or repeat revision surgery cases.
    There is insufficient published data to provide comment on efficacy of different scar barriers used in this setting, however the safety profiles of the different devices are good.
    My personal experience is of using collagen barriers in revision nerve surgery (more than 90 cases of revision CTD and revision cubital tunnel decompression). I am happy with the results and have only revised one for a post-operative haematoma. The use of the Vivosorb is more limited in this setting but in the cases I have performed to date (less than 10) there is no safety concern and good efficacy. The Vivosorb is useful when there is not significant epineurium scar and also when there is a patient objection to the use of an animal collagen product.
    The Vivosorb is also cheaper than porcine collagen nerve wraps.
    The Vivorsorb is manufactured from a polylactide of polycaprolactone. There is comprehensive data on the use of this polymer in peripheral nerve repair. The material is available as a Neurolac conduit for bridging small nerve gaps and in a thin walled version (Neurolac TW) for augmenting primary nerve repair or bridging small gaps in nerves at mobile points such as the digital nerves. There is one paper (Nassar 2014) detailing the use in carpal tunnel revision surgery.
    Comparative data on revision nerve surgery with simple decompression, nerve wrapping (collagen and bioresorbable polymer) or adjunctive anti-scar agents is needed to define the efficacy and risk profile of each. Based on the response to revision CTD with simple revision decompression alone, the majority of cases benefit without adjunctive techniques (90%) and so identifying an at-risk sub-group should be a key research strategy to target those patients that may benefit with the addition of some enhancement to simple revision decompression alone. In re-revision, the high failure rate suggests that this group would benefit most from the addition of an anti-scar technique. The datasets that would be required to power such an investigational study are large and a multicentre, long duration randomised controlled trial is impractical. Registry data would contribute to the evidence base and help define a future clinical trial.

    References:
    Levine DW, Simmons BP, Koris MJ, Hohl GG, Fossel AH, Katz JN. A self-administered questionnaire for the assessment of severity of symptoms and functional status in carpal tunnel syndrome. J Bone Joint Surg Am 1993;75:1585-1592
    Fowler JR. Nerve Conduction Studies for Carpal Tunnel Syndrome: Gold Standard or Unnecessary Evil? Orthopaedics 2017;40(3):141–142
    Kaile E, Bland JDP. Safety of corticosteroid injection for carpal tunnel syndrome. J Hand Surg Eur 2017 Jan 1:1753193417734426. doi: 10.1177/1753193417734426 [Epub ahead of print]
    Bland JD. Do nerve conduction studies predict the outcome of carpal tunnel decompression? Muscle Nerve 2001 Jul;24(7):935-40
    Bland JD. A neurophysiological grading scale for carpal tunnel syndrome. Muscle Nerve 2000 Aug;23(8):1280-3
    Tang CQY, Lai SWH, Tay SC. Long-term outcome of carpal tunnel release surgery in patients with severe carpal tunnel syndrome. Bone and Joint Journal 2017 Oct;99-B(10):1348-1353
    Sun PO, Selles RW, Jansen MC, Slijper HP, Ulrich DJO, Walbeehm ET. Recurrent and persistent carpal tunnel syndrome: Predicting clinical outcome of revision surgery. J Neurosurg 2019 Feb 15:1-9. doi: 10.3171/2018.11.JNS182598
    Djerbi I, Cesar M, Lenoir H, Coulet B, Lazerges C, Chammas M, Revision surgery for recurrent and persistent carpal tunnel syndrome: Clinical results and factors affecting outcomes. Chir Main 2015 Dec;34(6):312-7. doi: 10.1016/j.main.2015.08.010. Epub 2015 Nov 3
    Zieske L, Ebersole GC, Davidge K, Fox I, Mackinnon SE. Revision carpal tunnel surgery: A 10-year review of intraoperative findings and outcomes. J Hand Surgery Am 2013 Aug;38(8):1530-9. doi: 10.1016/j.jhsa.2013.04.024
    Nassar WA, Atiyya AN. New technique for reducing fibrosis in recurrent cases of carpal tunnel syndrome. Hand Surg. 2014;19(3):381-7

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