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Cubital tunnel decompression

    Overview

    Learn the Cubital tunnel decompression surgical technique with step by step instructions on OrthOracle. Our e-learning platform contains high resolution images and a certified CME of the Cubital tunnel decompression surgical procedure.
    Cubital tunnel syndrome is the second most common upper limb peripheral nerve entrapment neuropathy. The pathophysiology is poorly understood but most likely is a combination of nerve compression and abnormal tension forces due to the course of the ulnar nerve posterior to the elbow. The ulnar nerve passes from the arm to forearm posterior and medial to the elbow through the medial retrocondylar groove. The roof of the tunnel is formed by a thickening of the deep fascia (Osborne’s ligament) and the proximal free edge (Osborne’s band) may cause a local compression point. The tunnel lies between the humeral and the ulnar heads of the flexor carpi ulnaris. Where the two heads joint there are deep fascial thickenings within the muscle substance and at its deepest extent that can cause compression of the nerve beneath.
    Surgery to decompress the nerve may not relieve intraneural tension and this may explain the less predictable outcomes from cubital tunnel surgery. Indeed decompression my worsen nerve subluxation exacerbating symptoms. Simple decompression works for the majority of patients, however in cases of subluxation of the nerve or excessive tension a number or adjunctive procedures are described. Transposition of the nerve (subcutaneous or submuscular) anterior to the elbow is designed to shorten the course of the ulnar nerve. However well performed this procedure can produce secondary tether or compression points ay the arcade of Struther’s (distal free edge of the medial intermuscular septum) at the medial supracondylar ridge (against the insertion of the medial intermuscular septum insertion) and at the flexor carpi ulnaris (due to dorsal tether of the ulnar nerve by the proximal take off of the nerve to the ulnar head of the FCU).
    I prefer a detensioning procedure in cases of subluxation or excessive tension. This involves a partial excision of the medial epicondyle, allowing the nerve to translocate into a more anterior position without tension. This will be described separately.




    Indications

    Indications:
    Surgical treatment of cubital tunnel syndrome should be offered to patients with established motor dysfunction or sensory disturbance that is longstanding (3-6 months) without improvement following conservative measures. Surgery aims to release any compression points and minimise the risk of secondary complications from nerve subluxation.
    Symptoms and examination:
    Patients report tingling or numbness typically in the ring and small finger and not extending to the forearm. They will frequently report that the symptoms are worse when performing tasks where the elbow is held flexed for long periods or when there is repeated elbow flexion from lifting. Typical provoking activities include using a telephone, reading a book or driving. Symptoms are often worse at night causing nocturnal waking with numbness in the fingers. Patients often notice loss of fine motor movement and co-ordination in the dominant hand and weakness of grip.
    On examination there may be noticeable wasting of the ulnar nerve innervated intrinsic muscles within the hand with loss of bulk especially obvious in the first web space. In severe cases there may be mild clawed posture of the hand typified by MCPJ hyperextension and IPJ flexion. When there is motor involvement there will be reduced power of the flexor digitorum profundus to the small and ring fingers. Sensory loss can be rapidly screened using the “10-10s” test where the patient is asked to rate sensation to light tough in each of the fingers using 10 as normal and 0 as complete numbness. Quantitative sensory assessments can be performed using West or Semmes-Weinstein monofilament pressure threshold detection and innervation density can be assessed using static and moving 2 point discrimination. These should assess the hand as well as the medial arm. Typically medial arm involvement may suggest a more proximal compression at the thoracic outlet level.
    Provocation of symptoms can be achieved through elbow flexion for 1 minute. The onset of tingling or numbness in the ulnar digits is usually diagnostic. Direct compression of the nerve at the cubital tunnel posterior to the medial epicondyle is another way of reproducing symptoms. Tinel’s sign should be assessed starting distally at the hand and working upwards across Guyon’s canal to the forearm and then across the elbow segment to the infraclavicular plexus following the course of the nerve. The reproduction of tingling symptoms during gentle tapping over the nerve can highlight potential areas of compression and also identify other causes of the symptoms such as intrinsic peripheral nerve sheath tumours. Thoracic outlet syndrome and distal compression at Guyon’s canal should be excluded.
    Special tests include Froment’s sign which demonstrates recruitment of the median nerve innervated flexor pollicis longus (FPL) during examination of first webspace grip. Weak adductor pollicis and first dorsal interosseus function is compensated for using FPL. Jeane’s sign is positive when there is compensatory hyperextension at the MCPJ of the thumb during Froment’s test due to loss of the flexion moment of the intrinsic muscles that should be acting at this joint. Wartenburg’s sign is small finger escape with ulnar deviation due to loss of the palmar interosseus function at the 4th webspace.
    Stability of the ulnar nerve through a full range of active and passive elbow flexion is required to determine whether the nerve subluxes around the medial epicondyle during flexion. Surgical decompression in these cases typically results in further instability and the need for an adjunctive procedure such as medial epicondylectomy can usually be predicted in such cases.
    Revision cases require a more in depth clinical assessment including the sensation in the medial cutaneous nerve of arm and forearm to identify possible sites of injury and neuroma formation, nerve stability and possible secondary sites of compression.
    Investigation:
    Neurophysiology should be performed looking for reduced conduction velocity across the elbow segment of the ulnar nerve and normal sensory conduction in the medial cutaneous nerve of the arm and forearm. If there is motor involvement the ulnar innervated muscles should be sampled with electromyography to look for evidence of denervation (fibrillation and positive sharp waves).
    Neurophysiological assessment with motor and sensory conduction velocities can detect slowing of conduction across the elbow segment in cases of cubital tunnel syndrome. Comparison can be made with other nerves in the upper limb to exclude concomitant compression neuropathies or peripheral neuropathy. Electromyography can detect denervation changes in the ulnar innervated muscles as a result of motor axon death from longstanding or severe compression. Neurophysiology is essential in equivocal cases and is particularly good at excluding proximal pathology at the brachial plexus, medial cord, thoracic outlet or root level. In revision cases comparison should be made with previous neurophysiology and whether there was any post surgery improvement, even temporary.
    Imaging studies are useful to exclude other pathologies. MRI is useful in the cervical spine or plexus to determine whether symptoms may be contributed to by a spondyloradiculopathy or a thoracic outlet compression. Ultrasound is a useful dynamic investigation to determine site of compression, nerve instability of screen the nerve at other sites to exclude intrinsic pathology such as peripheral nerve sheath tumours. Ultrasound can demonstrate pre-stenotic dilatation of a compressed nerve as well as abnormal motion or thinning during elbow motion indicative of subluxation or abnormal tension.
    Non-operative management:
    Conservative strategies include avoidance of repeated elbow flexion tasks, night elbow extension splints and steroid injection at the cubital tunnel mouth. Splints are poorly tolerated by patients. Steroid injection may be beneficial but should only be undertaken by specialists familiar with the anatomy of the ulnar nerve at the elbow. The nerve lies in a subcutaneous position in deep elbow flexion and is fairly immobile in this position and the risk of inadvertent intraneural injection is high.
    Alternative operative management and contraindications:
    Surgery aims to release any compression points and minimise the risk of secondary complications from nerve subluxation. Decompression may be achieved using mini-open techniques which are designed to address the primary compression site whilst minimising the risk of creating nerve instability. A more extensive decompression can be performed using endoscopic nerve surgery with a light source, long retractors and long scissors. This technique allows proximal and distal compression points to be addressed but does not address tension and there is a learning curve with potentially higher rates of inadvertent iatrogenous injury to the ulnar nerve or the cutaneous branches to the arm and forearm. standard open decompression is the most common surgical procedure but can render the nerve unstable. Unstable nerves can be managed with transposition, designed to shorten the course of the nerve and alleviate tension. Transposition may be subcutaneous or sub-muscular. Both of these techniques carry a risk of creating secondary compression or tether points along the course of the ulnar nerve.







    Setup

    The arm is blocked with an axillary regional anaesthesia at the upper arm. The intercostobrachial nerve (lateral sensory branch form the 2ns intercostal nerve) and the medial cutaneous nerve of the arm lie separate from the main axillary neurovascular bundle and a separate subfascial block of local anaesthesia is usually required for adequate sensory block of the medial arm at the upper extent of the surgical incision.
    The arm is prepped from fingertips to axilla and draped for exposure of the whole limb. A sterile tourniquet is applied to the upper arm as high as possible so that it doesn’t interfere with the site of surgery.
    The shoulder is externally rotated and the elbow flexed 45 degrees and placed on a side table with supportive padding under the lateral side of the elbow to lift the arm away from the side table to improve access.
    If the shoulder doesn’t fully externally rotate then consideration should be given to performing the procedure with the arm flexed across the chest or in the patient under general anaesthesia, in the lateral position with a gutter arm support under the upper arm allowing access to the extensor surface of the elbow.
    The limb is exsanguinated using an Esmarch bandage and the tourniquet inflated to 250mmHg (150mmHg above mean arterial pressure).

    Operation

    A – Medial epicondyle
    B – Olecranon
    The arm is positioned supported on towels with the elbow flexed to 45 degrees and the shoulder fully externally rotated. The medial epicondyle is the origin of the common flexor muscle mass. The posterior most of these muscles is the humeral head of the FCU.
    The olecranon is easily palpated more posteriorly and the subcutaneous ulnar border is the origin of the ulnar head of the FCU.
    The ulnar nerve lies in the cubital tunnel between these two boney landmarks.
    It is usually easily palpated just above the cubital tunnel where it may be balloted against the posterior aspect of the medial epicondyle.
    In deep elbow flexion the nerve is compressed against the bone and is less readily palpable.

    The course of the ulnar nerve is marked just posterior to the medial epicondyle. This will form the line of the incision.

    The medial epicondyle and the olecranon are marked.

    Osborne’s band is the proximal free edge of the Osborne’s fascia which is the deep condensed fascia bridging the ulnar nerve between the humeral and ulnar heads of the FCU. The band is the commonest primary entrapment point during the nerve decompression.

    Consideration should be given to the cutaneous innervation of the medial elbow area as damage to the nerve branches can result in painful scars, subcutaneous neuromata and numbness. The anterior branch of the medial antebrachial cutaneous nerve (medial cutaneous nerve of the forearm) lies a mean 3.2cm anterior to the medial epicondyle and is found in virtually 100% of cadaveric specimens and a posterior branch is found a mean of 1.8cm posterior to the medial epicondyle in 60% of specimens (Mackinnon et al. J Plast Reconstr Surg. 2004).

    The skin is incised along the course of the ulnar nerve over the roof of the cubital tunnel posterior to the medial epicondyle over a course of 6cm.

    The wound is deepened looking for cutaneous nerve branches which must be preserved. Particular caution should be used in the distal end of the incision from 2cm distal to the medial epicondyle.

    There are small veins that cross the incision in the subcutaneous fat and these should be cauterised with bipolar diathermy to reduce the risk of haematoma.

    The fat is fully mobilised from the deep fascia and a self-retaining West retractor is inserted to expose Osborne’s fascia.

    The ulnar nerve is usually tightly compressed under Osborne’s fascia. Direct exposure of the ulnar nerve through the fascia can be undertaken with sharp dissection, however I prefer to expose the nerve distal to the fascia at the interval between the two heads for the FCU muscle where the tissue planes are more reliable and the nerve less compressed. This way it is easier to develop the epineural plane around the nerve for the release without a risk of breaching the epineurium.

    Further dissection along the deep fascia distally demonstrates the origins of the two heads of the FCU muscle. The ulnar head is seen here in the distal and posterior aspect of the wound. A Ragnell retractor can be placed under the distal subcutaneous fat to retract and protect any cutaneous branches to prevent damage during the distal deep exposure of the main ulnar nerve trunk.

    The fascia overlying the muscle can be incised to expose the ulnar nerve.

    O – Osborne’s fascia
    H – Humeral head FCU
    U – Ulnar head FCU
    UN – Ulnar Nerve
    The interval between the two FCU heads has been opened and the ulnar nerve lies just deep to this layer.

    The humeral head of FCU it lifted demonstrating fascial bands crossing the ulnar nerve. These can be released using tenotomy scissors. Care must be taken when dissecting close to the nerve as there are motor branches to the FCU heads lying in the perineural fat that are vulnerable to injury at this stage of the operation.

    The ulnar nerve is released further distally using Ragnell retractors to expose the nerve between the two heads of the FCU.

    Next the Osborne’s fascia is released proximally throughout the length of the cubital tunnel.

    The ulnar nerve has now been released throughout the length of the cubital tunnel and is seen lying in the floor of the tunnel overlying the humero-ulnar joint capsule and the retrocondylar groove.

    At the mouth of the cubital tunnel there may be deep fascia condensations causing nerve compression. Using a Ragnell retractor to retract the proximal sound edge away from the nerve, the fascia can be visualised and released. Approximately 3cm above Osborne’s fascia there is a vein that crosses the nerve. This should be cauterised with bipolar diathermy to prevent a haematoma forming on tourniquet release.

    The proximal dissection is completed and the nerve is seen lying free in the floor of the cubital tunnel.

    Stability of the nerve is next assessed. Here the elbow is fully extended and the nerve position is noted. An assessment of intraneural tension can be made by palpation of the nerve from side to side.

    Next the elbow is flexed fully and the position of the nerve is noted relative to the medial epicondyle. A further assessment of tension should be made by palpation in this position.
    Here the nerve remains stable and well located in the medial epicondylar groove throughout all range of motion in the elbow and there is no undue tension.
    Simple decompression is sufficient. If there is subluxation, excessive tension or there is a tardy ulnar nerve palsy associated with cubitus valgus or progressive fixed flexion of the elbow due to osteoarthritis then consideration should be given to a medial epicondylectomy adjunctive procedure at this stage This will be described in a separate procedure.

    Following haemostasis with bipolar diathermy a subcuticular closure is performed with an absorbable continuous suture.

    The surgery site after wound closure and prior to dressings.

    Steristrips can be applied to the wound edges followed by an occlusive dressing and a wool and crepe buly bandage from mid forearm to mid humerus level.

    Post Operative

    The arm should be elevated in a sling for 24 hours and protected until the regional block has worn off completely.
    Reduce the bulk dressings at 5 days, inspect the wound for haematoma and infection complications.
    Replace the occlusive dressing.
    Remove the dressing and steristrips at 14 days and trim any suture ends.
    Encourage moisturising scar massage at this stage. This aids scar maturation and reduces scar sensitivity.
    The arm can be used for light household tasks from dressing reduction at 5 days. Heavy lifting and repetitive elbow flexion tasks should be avoided for 2-4 weeks.
    Clinical review at 6 weeks should assess functional recovery and symptom resolution. Nerve stability under active range of motion should also be assessed.

    Recommended Reading

    Following cubital tunnel surgery clinical outcome may be assessed with sensory testing using monofilaments and 2 point discrimination. Motor recovery can be assessed using the MRC grading system or absolute measures can be made using digital myometry assessment of the intrinsic muscles using a standard test algorithm. The PRUNE score (Patient Rated Ulnar Nerve Evaluation is a useful patient reported outcome measure that has been validated for use in this condition (McDermid JC and Grewal R. BMCMusculoskeletal Disorders 2013, 14:146).
    References and literature review:
    Natural History and Conservative Management of Cubital Tunnel Syndrome. (2007). Natural History and Conservative Management of Cubital Tunnel Syndrome, 23(3), 311–318. http://doi.org/10.1016/j.hcl.2007.05.002
    Splinting is effective in cubital tunnel compression however may not be well tolerated by patients. Steroir d injections have lower efficacy than seen in other peripheral nerve compressions such as carpal tunnel syndrome.

    O’Grady EE, Vanat Q, Power DM, Tan S. A systematic review of medial epicondylectomy as a surgical treatment for cubital tunnel syndrome. J Hand Surg Eur 2017, Nov;42(9):941-945. doi: 10.1177/1753193417724351. Epub 2017 Aug 31.
    This review examines 21 case series and 886 medial epicondylectomy procedure with 79% of cases having improved outcome using McGowan’s criteria. The comparative data for simple decompression is limited with no difference observed in one series. Comparison with transposition shows no difference in 2 series and improved function with medial epicondylectomy in 3 publications.
    MacDermid JC, Grewal R. Development and validation of the patient-rated ulnar nerve evaluation. BMC Musculskeletal Disorders 2013, 14:146
    This paper evaluates a novel patient rated score (PRUNE Score) in the assessment of cubital tunnel syndrome. The use of a disease specific patient reported outcome measure (PROM) is to be recommended for studies in this area. Previous outcome measures for cubital tunnel syndrome have detailed intrinsic wasting, weakness or paralysis and there is significant intra- and inter-observer error. Indeed the literature on cubital tunnel is littered with modifications to previous scoring systems that make meta-analysis impossible.The PRUNE score needs to be validated in simple decompression versus medial epicondylectomy as it may have different responsiveness with different surgical procedures.

    Reference

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