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Guyons canal release

    Overview

    Learn the Guyons canal release surgical technique with step by step instructions on OrthOracle. Our e-learning platform contains high resolution images and a certified CME of the Guyons canal release surgical procedure.
    The ulnar nerve and artery pass through Guyon’s canal to the hand. The canal lis superficially on the ulnar palmar side of the wrist and is bordered ulnarly by the hypothenar eminence. The ulnar nerve is vulnerable to trauma at the wrist level. Compression of the ulnar nerve at this site is rare and can be associated with tumours or ganglion swellings arising from the piso-triquetral articulation. A well-developed palmaris brevis may contribute to compression. thickening of the fascia at the distal forwarm can be associated with distal ulnar neuropathy as the nerve crosses the wrist crease to the hand through the start of Guyon’s canal. The motor branch passes deeply into the hand and courses around the hook of the hamate where it is vulnerable to injury. Symptoms of ulnar nerve compression at this site may be both sensory and motor depending on the site of compression.
    Functionally there are 3 zones to Guyon’s canal. Zone 1 includes the main motor and sensory ulnar nerve proximal to bifurcation; zone 2 the deep ulnar nerve exits to pass around the hook of the hamate; zone 3 the ulnar nerve superficial branch is at risk of compression superficially in the palm.

    Indications

    INDICATIONS:
    Exposure of Guyon’s canal may be required in trauma with wounds in the region of the ulnar wrist crease and hypothenar eminence. Elective exploration and decompression may be required for distal ulnar nerve entrapment neuropathy due to trauma, tumours or ganglion compression. Injuries to the hook of the hamate with non-union are rare, difficult to diagnose and may cause isolated compression of the deep motor branch. Chronic compression may occur in cyclists and in the “hypothenar hammer” syndrome due to repeated direct trauma to the ulnar nerve and artery (which may thrombose or develop aneursymal swelling). In recovering proximal nerve repairs the regenerating nerve is swollen and distal decompression may be required to maintain neural regeneration and avoid auto compression at tight anatomical sites.
    SYMPTOMS & ASSESSMENT:
    Patients may describe aching discomfort in the ulnar side of the wrist, there may be swelling visible of palpable in cases of ganglion compression from the pisotriquetral joint or with intrinsic nerve sheath tumours. Sensory disturbance is isolated to the palmar ulna 1.5 digits and the skin over the hypothenar eminence in entrapment of Guyon’s canal. The ulnar dorsal cutaneous sensory nerve branches from the main ulnar nerve in the distal 1/3 of the forearm and crosses the ulnar border of the wrist and hand to supply the dorsal 1.5 digits and so is not implicated in compression at the more distally placed Guyon’s canal. Isolated motor branch involvement may be seen in distal Guyon’s canal entrapment without sensory disturbance.
    There may be ulnar-innervated intrinsic weakness or paralysis with severe compression. In such cases there is flattening of the transverse palmar metacarpal arch, hyperextension of the MCPJs and ulnar deviation of the small finger (Wartenburg’s sign). There is unopposed action of the long extrinsic digital flexors and extensors without intrinsic modulation. The posture is described as an ulnar “claw hand”. The adductor pollicis is weak or paralysed in such cases and attempted key pinch grip requires recruitment of FPL (median innervated). This is Froment’s sign. There may be thumb MCPJ hyperextension due to loss of the flexion vector pull of the adductor (Jeanne’s sign).
    sensory assessment of the palmar ulnar nerve can be using the 10/10 system and comparison with the digits on the opposite hand or with quantitative assessment using Semmes-Weinstein or West monofilament pressure thresholds, and/or static and moving 2 point discrimination.
    The pisotriquetral joint should be balloted for tenderness and crepitus.
    The hook of hamate should be palpated for tenderness and comparison made with the opposite hand as there is usually some discomfort with pressure at this point due to the proximity of the ulnar nerve.
    Resisted FDP flexion to the small finger may produce pain with a hamate hook fracture or non-union due to the pulley action of the FDP around the hook. In rare cases the FDP to the small finger can suffer an attrition rupture with hamate hook fractures.
    Vascular assessment of ulnar artery flow should include Allen’s test at the wrist.
    INVESTIGATION:
    Investigations may be required to exclude degenerative joint disease and fractures, soft tissue imaging for ganglia and intrinsic nerve tumours, neurophysiology for quantitative evaluation of ulnar nerve dysfunction and rarely vascular studies to look at ulnar artery flow.
    The lateral wrist radiograph may demonstrate degeneration at the pisotriquetral joint. Plain radiographs are of limited value in evaluation of the hamate. A carpal tunnel view may be useful but CT provides the optimum bone imaging for the carpus.
    MRI is useful in imaging ganglia and intrinsic nerve tumours and excluding other wrist pathology that could produce ulnar sided wrist symptoms.
    US is an excellent modality for imaging the ulnar nerve and artery at Guyon’s canal. The superficial location of the canal lends itself well to this technique. The distal deep motor branch is more difficult to visualise and MRI will be required if distal imaging is unsatisfactory.
    Neurophysiological studies can assess nerve conduction velocity, latency and amplitude. Slowing of ulnar nerve conduction velocity across the wrist is suggestive of a compression neuropathy at Guyon’s canal. Electromyography of the ulnar innervated intrinsic muscles may demonstrate evidence of denervation in severe compression. This would be manifest with fibrillation and positive sharp waves on sampling the ADM, the dorsal interossei and the adductor pollicis.
    OPERATIVE ALTERNATIVES:
    Compression of the nerve should be treated with open decompression. Nerve tumours may be resected. A ganglion compressing the nerve and arising from the pisotriquetral articulation should be treated with decompression, ganglion excision and consideration given to pisiform excision in recurrent cases or those patients with severe symptomatic pisotriquetral osteoarthritis. The hook of the hamate can be excised for symptomatic non-union.
    In severe motor neuropathy, anti-claw procedures and an adductorplasty can be used to improve hand posture and function. In severe sensory loss without recovery, transfer of the 3rd web space nerve (median) to the UDN to the small finger can provide some protective sensation to the ulnar side of the hand and small finger.
    NON-OPERATIVE ALTERNATIVES:
    An early diagnosis of compression can be treated with rest and a wrist splint. Steroid injections may reduce sensory symptoms, but in cases with established motor neuropathy I would advocate a surgical approach to management.
    CONTRAINDICATIONS:
    There is a genetic condition HNPP where there is a predisposition to peripheral nerve compression. In such cases initial conservative measures should be adopted. Persistent symptoms, recurrent symptoms and pain are indications to consider surgery.

    Setup

    The patient should be consented for exploration and suitable anaesthesia selected. I would advocate either general anaesthesia without neuromuscular blockade or high regional anaesthesia at the axillary level. Both of these techniques will allow intra-operative nerve stimulation to assess function in the motor component of the ulnar nerve if necessary.
    An upper arm tourniquet is applied and the limb exsanguinated with an Esmarch bandage or pneumatic Rhys Davies exsanguinator.
    A lead hand is useful to position the forearm, wrist and hand in supinator and provide a stable operative target.
    Loupe magnification should be used to assist in dissection and identification of nerve branches.
    Bipolar diathermy with fine-tipped micro-forceps should be used for haemostasis.
    A nerve stimulator may be required to assess motor function in the ulnar nerve.
    The limb is prepped from fingers to tourniquet level and draped with a limb pack.

    Operation

    The hand is placed in a lead hand for support and the pisiform is palpated and marked proximally and ulnar to the nerve at the level of the wrist crease. The hook of the hamate is more radially and distally positioned and required deep palpation to identify it.
    The skin incision is marked from the radial border of the FCU tendon in the forearm in a “lazy S” orientation angulated at the wrist crease and extended distally initially straight and then curved radially towards the distal palm beyond the hook of hamate if needed to visualise the distal part of the deep motor branch of the ulnar nerve.
    Gross and Gelberman described three zones of compression in Guyon’s canal in 1985. proxmally zone 1 includes the motor and sensory ulnar nerve, distal and radially is zone 2 containing the deep motor ulnar nerve and distally and ulnarwards is zone 3 containing the superficial ulnar nerve (sensory).

    The skin is incised. Fascial bands cross the ulnar neurovascular bundle at the mouth of Guyon’s canal. These bands arise in the distal antebrachial fascia but there are sometimes bands extending from the FCU tendon inserting into the deep palmar fascia. These should be divided.

    The ulnar artery and venae commitantes can be seen within the zone 1 of Guyon’s canal.

    The ulnar nerve (UN) is ulnar to the vessels (UA) in zone 1 of Guyon’s canal.

    The nerve is identified and protected and the roof of the canal opened.
    Palmaris brevis may be present and cross the nerve at this point. If found it should be simply divided.
    The canal is bounded ulnarly by the pisiform, the pisohamate ligament and the abductor digiti minimi muscle belly. The floor is the hypothenar muscle sand the transverse carpal ligament. The roof is the volar carpal ligament and the radial border is the hypothenar fat pad proximally and the hook of the hamate distally.

    The volar carpal ligament should be divided to fully expose the ulnar nerve in zone 1 and the sensory (superficial) ulnar nerve in zone 3.
    A sloop may be placed around the nerve in zone 1 or even in the distal forearm to gently lift the ulnar nerve from the bed and allow retraction to expose the deep motor branch which is hard to visualise.
    A vessel may cross from radial to ulnar from the ulnar artery towards the hypothenar eminence and must be divided to allow this retraction.
    The operator may identify two nerves in the distal superficial dissection (zone 3) and erroneously conclude that the motor and sensory nerves have been demonstrated. The superficial (sensory) ulnar nerve branches in the canal providing a branch to the hypothenar skin, the UDN to the small finger and a 4th web space nerve. In the distal palm there may be a radial sided communicating branch to the 4th CDN from the median nerve to the 3rd web space. care should be taken to avoid injury to this common variant branch at this level (Berrettini anastomosis).
    Ferrari and Gilbert have classified the common variations fo the Berrettini anastamosis.
    Type 1 is a communication in an oblique course from the ulnar to the median nerve
    Type 2 is a communication parallel to the distal margin of the transverse carpal ligament
    Type 3 is a communication in an oblique course from the median nerve to the third common digital nerve originating below the distal margin of the transverse carpal ligament
    Type 4 is an atypical communication

    In 15% of cases there are distal sensory branches crossing Guyon’s canal and care should be taken to avoid injury. These branches form the palmar ulnar branches of the ulnar nerve and they cross towards the skin of the hypothenar eminence.

    Following release of the band the crossing vessel is seen in the distal Guyon’s canal. This will need dividing to lift the nerve and demonstrate the deep motor branch.

    The volar carpal ligament is fully released and the nerve is visualised in Guyon’s canal. The motor branch must be seen between the artery and the superficial ulnar nerve as it passes deep and around the hook of the hamate covered by the fibrous origin of the flexor digiti minimi on the hamate.

    The vessel has been divided. The ulnar nerve is seen lying free in the first part of the Guyon’s canal The deep motor branch (zone 2) must be identified and requires mobilisation and retraction of the ulnar nerve trunk in zone 1 or the sensory ulnar nerve in zone 3.

    The motor branch is being traced distally around the hook of the hamate under the fibrous arch of the FDM origin. This fibrous tisssue must be divided. A watson-Cheyne place between the nerve and the arch can protect the nerve during release of the tight fibrous arch. Great case should be taken to avoid damage to any accompanying vessels from the ulnar artery that will pass with the deep branch of the ulnar nerve t form the deep palmar arch. Bleeding on tourniquet release will require the use of diathermy near the nerve which is not advised.

    The tips of the curved scissors are following the course of the deep motor branch of the ulnar nerve.
    It can be difficult to identify the motor branch. The following tips may help:
    Separate the UN from the uA and lift from the bed in a sloop having used bipolar diathermy to coagulate ten divide vessels crossing the nerve. The motor branch will be seen passing deep and distally and can be traced to the hamate hook then decompressed.
    Develop the interval between the UN and the UA. Retract the superficial sensory UN and branches in a sloop pulled gently distally and ulnarwards in the zone 3 of Guyon’s canal. The motor branch can be seen leaving the UN in distal zone 1 and passing radially and distally towards the hook of the hamate.
    Palpate the hook of the hamate and identify the fibrous origin of FDM. Pass a Watson-Cheyne deep to the proximal origin and carefully release the fibrous arch. The deep UN will be visualised as it passes distal to the hook of the hamate.

    In this photograph the ulnar sensory branch is retracted radially and the deep UN branch is seen passing distal to the hook of the hamate. The overlying fascia has been released.

    Careful haemostasis prevents post-operative haematoma formation. The wound is closed in this case using interrupted vicryl 4’0 sutures. An occlusive dressing is applied with gauze padding and a wool and crepe bulky bandage for support. The limb is elevated in a high sling.

    Post Operative

    The limb is elevated and the patient is prescribed simple analgesia medication.
    The bulky dressing is reduced after 48 hours and a clean occlusive dressing maintained for 10 days after which the area can be washed.
    Scar massage can be commenced from 2 weeks until scar maturation.
    A sensory and motor assessment should be made at 6 weeks.

    Recommended Reading

    Guyon’s canal compression of the ulnar nerve is uncommon and therefore exploration will be unfamiliar to the surgeon. revising the rlevant anatomy and pathoanatomy is important prior to surgery. Many cases of recurrent or persistent symptoms are seen in our peripheral nerve practice and i suspect the the motor branch is infrequently adequately decompressed in zone 2. The operating surgeon may identify the branching of the superficial ulnar nerve to UDN, second web nerve and mistake that for the zone 1 branch point between motor and sensory UN. To avoid this pitfall I would recommend starting proximally, even in the forearm and using a sloop to elevate the UN from the bed in Zone 1 and the motor branch will be readily seen passing distally, radially and deep to the superficial ulnar nerve. It can then be traced distally and decompressed fully as it courses around the hamate.
    References:
    1.The anatomy of the distal ulnar tunnel. Gross MS, Gelberman RH. Clin Orth Rel Res. 1985;238-47
    This paper describes the commonly used 3 zones to define the sites of Guyon’s canal compression.
    2. The results of ulnar nerve decompression in Guyon’s canal syndrome. Kaiser R, Houstava L, Brzezny R, Haninec P. Acta Chir Orthop Traumatol Cech. 2012;79:243-8
    This paper report 13 cases of distal ulnar nerve compression. 4 cases were associated with a ganglion. The remainder were thought to be due to local trauma or compression from fibrous structures at Guyon’s canal. 12/13 demonstrated improved symptoms post-operatively.

    Reference

    • orthoracle.com

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