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Axillary nerve decompression for quadrangular syndrome

    Overview

    Learn the Axillary nerve decompression for quadrangular syndrome surgical technique with step by step instructions on OrthOracle. Our e-learning platform contains high resolution images and a certified CME of the Axillary nerve decompression for quadrangular syndrome surgical procedure.
    Axillary nerve exposure and decompression may be required for primary entrapment neuropathy known as the “quadrangular space syndrome”, for evaluation of an axillary nerve injury and optimisation of the environment for recovery from more proximal injury or for poor regeneration following C5 spinal nerve root decompression.The symptoms and functional loss will be defined by the underlying pathology.
    Quadrangular space syndrome was reported in throwing athletes and those engaged in overhead activity. In this condition there is usually posterior shoulder pain with sensory disturbance in the upper lateral cutaneous nerve territory, weakness of the deltoid and often paralysis of the teres minor resulting in impaired shoulder external rotation in the elevated and abducted shoulder position. There is often occlusion of the posterior circumflex humeral artery on shoulder abduction and external rotation (the ABER position). Placing the patient’s arm in this position may induce symptom onset and is a clinical examination test supporting the diagnosis.
    Decompression is performed using a posterior approach and the axillary nerve can be evaluated with nerve stimulation. Compression points can be released using this approach, however the full course of the axillary nerve from its take-off from the posterior cord cannot be visualised and in trauma presenting early an anterior approach is to be preferred to facilitate access for reconstruction of a ruptured nerve. In late presenting cases, the posterior approach is more useful because if there is no functional continuity of the axillary nerve, a nerve transfer from the triceps motor branches can be performed close to the axillary nerve motor points, allowing late salvage of a complete lesion of the axillary nerve.
    The modified Somsak nerve transfer technique is described as a separate operative technique in OrthOracle Modified Somsak nerve transfer (medial head of triceps nerve transfer to anterior division of the axillary nerve through a posterior approach)


    Indications

    INDICATIONS:
    Axillary nerve compression at the quadrangular space may follow repeated shoulder abduction for overhead sports-related activity. In such cases there is hypertrophy of the long head of the triceps and the teres major resulting in encroachment of the axillary nerve in the quadrangular space. The nerve may also be compressed by fibrous bands, scar following shoulder trauma, posterior glenoid labral cysts, by scar following a rupture of the posterior circumflex humeral artery, from callus associated with proximal humeral fractures or from tumours in the vicinity of the nerve as it passes to the posterior shoulder through the quadrangular space. The quadrangular space syndrome was first described by Cahill and Palmer in 1983.
    Regenerating nerves following a proximal nerve sheath continuity injury with axonopathy or following spinal nerve root compression, demonstrate swelling as the growth cone progresses and distal decompression at anatomically tight locations may facilitate further regeneration.
    In cases of late presenting C5 injuries after 3 months or isolated axillary nerve injuries after 6 months, the posterior approach for axillary nerve decompression and evaluation is preferred as non-functioning complete lesions may be salvaged at this stage by means of nerve transfer from one of the triceps motor branches.
    SYMPTOMS & ASSESSMENT:
    Quadrangular space syndrome is associated with posterior shoulder pain, weakness of the deltoid muscle, weakness or paralysis of the trees minor and disturbance of sensation in the upper lateral cutaneous nerve of the arm distribution. There may be tenderness on palpation over the quadrangular space posteriorly. Tinel’s sign may be elicited on tapping over the posterior axillary nerve as it exits the space. There will be reduced external rotation strength in the abducted shoulder. Symptom onset may be provoked by placing the arm in the ABER position and passively stretching the arm to full external rotation.
    In cases with axillary nerve injury there will be wasting of the deltoid and teres minor with additionally a sulcus sign apparent due to inferior subluxation of the glenohumeral joint in C5 lesions due to associated loss of the supraspinatus muscle strength.
    In axillary nerve rupture cases there may be an anterior Tinel’s just medial and inferior to coracoid over the proximal axillary nerve at its take-off from the posterior cord. The sensory radiation in such cases will be to the upper lateral cutaneous nerve of the arm territory.
    INVESTIGATION:
    Plain radiographs of the shoulder are useful after trauma to exclude malunion of callus encroachment on the quadrangular space as a chase of pain and axillary nerve dysfunction.
    Computed tomography (CT) may offer a better way to visualise the extent of callus, however the neurovascular bundle may not well visualised unless contrast is used to visualise the posterior circumflex humeral artery (PCHA) with CT angiography.
    Magnetic Resonance Imaging (MRI) and Magnetic Resonance Angiography (MRA) will demonstrate the PCHA and the adjacent axillary nerve as it courses posteriorly through the quadrangular space around the proximal humerus. MRI is a useful investigation for identifying associated shoulder articular pathology including posterior labral cysts, soft tissue extra-neural tumours, intra neural tumours, primary bone tumours and chondral tumours. The teres minor may show denervation oedema changes on MRI.
    Angiography is reported as demonstrating occlusion or compression / distortion of the PCHA in cases of quadrangular space syndrome, however invasive angiography may not be required if there is a clear pattern of denervation and compressive pathology visualised on MRI and MRA.
    Neurophysiology studies including electromyography (EMG) are useful in confirming the denervation changes are isolated to the axillary nerve innervated deltoid and teres minor muscle. The extent of denervation can be used to assist in prognosis and decision-making regarding simple decompression or reconstruction with a nerve transfer from one of the triceps motor branches. EMGs are useful in excluding other pathology such as ~C5 motor radiculopathy from degenerative spinal nerve root compression, C5 brachial plexus injuries or more widespread neurological dysfunction as seen in post-viral neuropathies such as the Parsonage-Turner syndrome.
    OPERATIVE ALTERNATIVES:
    In cases of suspected rupture of the axillary nerve following trauma, exploration is to be preferred through an anterior approach to allow visualisation of the axillary nerve from where it arises as a branch from the posterior cord and to trace it posteriorly and laterally to the quadrilateral space. If a rupture is identified in the quadrilateral space, a second posterior approach may be required to allow reconstruction with nerve grafts to the nerve stump distal to the site of rupture.
    In cases of proximal lesions of the C5 root due to trauma or spinal nerve root compression, exploration using a posterior approach can be followed with a nerve transfer with a motor branch from the triceps. This technique brings the nerve transfer co-aptation site close to the denervated deltoid and the trees minor and provides rapid reinnervation potential in cases when the nerve injury has been complete and there has been a delay to diagnosis, referral or exploration. In such cases functional recovery is still possible as long as the nerve transfer is performed between 6 and 9 months from the complete nerve injury.
    Nerve transfers can also be performed using an anterior approach to the axillary nerve and donor nerves may be intercostal nerves, triceps branches or even a fascicle from the ulnar nerve as it forms as a branch from the terminal medial cord.
    NON-OPERATIVE ALTERNATIVES:
    Non-operative strategies include physiotherapy aimed at rebalancing muscles around the shoulder girdle, alleviating neural tension and strengthening the weak deltoid and trees minor.
    Ultrasound guided injections ion of steroid to the quadrangular space has been suggested as a way of improving pain symptoms and reducing swelling associated nerve compression.
    CONTRAINDICATIONS:
    There are no contraindications to quadrangular space decompression. in complete longstanding nerve lesions, the main challenge is the likely persistent weakness due to longstanding denervation. Decompression may reduce pain but may not improve the muscle strength.

    Setup

    The posterior approach to the quadrangular space can be performed in the prone, “beach chair” sitting position or in the lateral position. I prefer the lateral position as it affords excellent access to the quadrilateral space and the arm can be abducted to facilitate the assessment of the compression and ensure that decompression is adequate in a position similar to that for symptom provocation. The lower arm should be partly flexed at the shoulder and should be carefully positioned with the arm removed from the theatre gown to avoid compression in the axilla and the reduce the risk of iatrogenous nerve compression injury to the contralateral brachial plexus. The head should be supported on pillows with acre to avoid excess contralateral lateral flexion and traction on spinal nerve roots or the ipsilateral supraclavicular brachial plexus.
    General anaesthesia without neuromuscular blockade is to be preferred to allow nerve stimulation intra-operatively. nerve stimulation can be used to assess residual nerve function, improvements from decompression and in cases of severe or complete paralysis to assist in identifying a suitable donor muscle branch from the triceps for nerve transfer.
    Surgery is usually performed as a day case in healthy individuals.
    Thromboembolic deterrent stockings and pneumatic pressure garments are used intraoperatively to reduce the risk of thromboembolic complications.

    Operation

    This patient had persistent dysfunction of the deltoid and the trees minor following a dislocation if the glenohumeral joint with no neurophysiological evidence of recovery in the deltoid, posterior shoulder pain and a Tinel’s sign at the quadrilateral space.
    The suspected diagnosis is a rupture of the axillary nerve within the space, a continuity lesion with neuroma or a recovering axonopathy with scar and compression in the space.
    The patient is 6 months post injury and functional recovery should be apparent clinically and on EMGs at this stage. The decision was made to explore, decompress, neurolyse the axillary nerve if scarred, stimulate and if necessary undertake a triceps to axillary nerve transfer if a complete injury with no stimulation was identified.
    The lower arm is partially flexed at the shoulder, the torso is supported by posts with care to avoid pressure on the abdomen and the affected arm is uppermost in a gutter support with padding and no pressure over the brachial plexus in the axilla. The head is supported on pillows to prevent excessive lateral flexion.

    Viewed from posteriorly the operative site is exposed and access to the quadrangular space can be readily achieved. Hair removal is with an electric razor if necessary.
    The arm to be operated is partially abducted and forward flexed to open the access to the quadrangular space.
    the whole limb will be left exposed so that the effects of nerve stimulation intra-operatively can be observed and to allow mobilisation of the arm including passive elevation, external rotation and internal rotation to identify any impingement lesions that may need decompression.

    The surface anatomy has been marked prior to skin preparation. The scapular spine and the acromial arch in continuity with the clavicle are palpable and marked superiorly. this arch gives origin to the deltoid muscle which is wasted in this patient.
    The medial and lateral border of the scapula are marked. The scapula will rotate as the arm is abducted and may shift relative to the skin markings with shoulder protraction and retraction during the operation. The surgeon should be aware of the possibility of intra-operative changes in the position of the scapula that may affect the deep surgical exposure and identifying the relevant anatomy of the quadrangular space.
    The insertion of the deltoid is marked at the lateral mid-humeral position. The axillary nerve anterior division is marked as it courses laterally and anteriorly around the upper humerus, deep to the deltoid muscle, 5cm distal to the lateral border of the acromial arch.
    The interval between the long head of triceps distal and the lateral head of triceps proximally is marked on the posterior arm in case the triceps branches must be identified with the radial nerve at the triangular space below the trees major tendon in the event of an intra-operative decision to proceed with a triceps branch to axillary motor nerve transfer.
    The whole ipsilateral upper limb skin is prepared from the posterior mid-line and the top off the shoulder into the posterior triangle of the neck.
    A “U” shaped drape is placed in the axilla and further drapes used to isolate the surgical field. Disposable adhesive paper strips may be used to prevent drape slippage and displacement intra-operatively.
    An electrode must be place on the non-prepped skin close to the operative site to allow a nerve stimulator s=circuit to be made for use during the surgery.
    A monopolar diathermy plate should be placed over a muscles area of the lower back, buttock or thigh. Monopolar diathermy is used for the superficial exposure. The deeper exposure uses a bipolar diathermy to prevent inadvertent current passing along neurological structures during haemostasis close to nerve branches.

    The surgical assistant stands in front of the patient and the operating surgeon stands posterior to the shoulder. The skin is incised with a number 10 bladed scalpel. The incision is placed along the posterior border o the deltoid from the quadrangular space distally in the inter triceps interval. The incision starts 4cm proximal to the marked axillary nerve.
    The incision proximal landmark is approximately 3cm diagonally distal and lateral to the posterior corner of the acromial arch which is readily palpated due to the overlying deltoid wasting.

    Monopolar diathermy is used to expose and divide the subcutaneous fat in the line of the skin incision down to the deep fascia.

    Vessels crossing the incision in the fat should be coagulated with diathermy. The upper lateral cutaneous nerve terminal branches may be identified as they pas through the deep fascia to the skin in the middle and distal thirds of the incision. These branches may be traced through the deep fascia to the posterior division of the axillary nerve and are a useful landmark to identifying the nerve in the quadrangular space.

    The posterior fibres of the deltoid muscle are seen here in the upper part of the proximal incision. The deltoid does not look denervated. A denervated muscle is pale brown in colour. Innervated muscle has a deep red-brown colour and twitches when gently squeezed with forceps. Jamieson scissors are being used in the middle third of the incision to identify the upper lateral cutaneous nerve terminal branches crossing the interval from the deep fascia to the skin.

    A cat’s-paw retractor is used in the inferior edge of the incision to retract the skin and assist visualisation of the posterior border of the deltoid muscle. A larger Langenbeck retractor is placed in the upper (proximal) skin edge and when necessary may be placed deeply under the posterior edge of the deltoid to retract superiorly to assist in deeper exposure of the quadrangular space. the operating surgeon should place the retractor in this interval to avoid too distal positioning with risk of direct trauma to the underlying anterior division of the axillary nerve as it passed anteriorly and laterally around the proximal humerus deep to the deltoid muscle.

    A nerve stimulator needle is connected to the electrode placed at the start of the procedure and covered with an arthroscopy cameo drape. The electrical connections are made to the anaesthetic nerve stimulator box which can be controlled by an unscrubbed member of the team. Stimulation thresholds between 0.05mA and 5mA can be used to assess whether there is retained function in the axillary nerve. A normal threshold for visible contraction of the deltoid muscle would be 0.1mA with evidence of increased contraction with increasing stimulation usually reaching a maximum recruitment at 0.5-1.0mA depending on the proximity of the needle tip to the motor fascicles and the thickness of the epineurium. In a scarred nerve the stimulation may be less obvious with weaker contraction and greater stimulus required. After neurolysis the threshold may drop and the contraction may be more forceful. this I a good result and bodes well for further recovery. In a sever axonotmesis injury with no recovery or a neurotmesis injury, there will be no visible contraction. In such cases the axillary nerve should be traced deeply into the quadrilateral space to rule out scar and compression which can be released. In such cases a neuroma in continuity or a rupture may be identified, however rupture or neuroma may occur much more proximally where the axillary nerve arises from the posterior cord. This area cannot be visualised from the posterior approach and the surgeon would only use this posterior approach in isolation if the duration of paralysis is longstanding at 6 months or more and a salvage nerve transfer from triceps is contemplated if no stimulation is identified.

    The Langenbeck retractor is retracting deltoid proximally and a self-retaining Travers retractor is placed between the deep fascia inferiorly and the deltoid superiorly to expose the fat overlying the quadrangular space.

    The deep dissection is performed with jamieson scissors and DeBakey non-toothed forceps. The axillary nerve is identified either through tracing the upper lateral cutaneous nerve deep to the fascia, under deltoid and the to the posterior division of the axillary nerve or by palpating the anterior division of the axillary nerve and rolling it against the humerus under deltoid and tracing poteriorly deep into the quadrangular space. There are multiple vascular branches from the accompanying vessels with the PCHA and veins. Careful dissection and haemostasis with bipolar cautery is required to avoid bleeding from obscuring the view of the nerve and its branches.

    Bipolar cautery is used to prevent bleeding from the accompanying vessels exiting and entering the quadrangular space.

    The anterior division of the axillary nerve is seen here exiting the quadrangular space and crossing anteriorly and laterally around the upper humeral shaft deep to the deltoid muscle.

    A surgical sloop (red) has been placed around the ULCN branch. This branch arises from the posterior division of the axillary artery and can be traced back to the quadrangular space identifying the nerve to trees minor and the posterior division branch to the deltoid. Tracing further proximally identifies the posterior branch take-off from the main axillary nerve trunk. The anterior division can then be traced from the main axillary trunk and traced to the deltoid where is passes anteriorly around the humerus deep to the deltoid. The origin of the anterior division is obscured by vessels which may need mobilising or dividing to expose the nerve. Ligaclips are being applied to a branch off the axillary artery to assist in identification and mobilisation off the nerve deep to it.

    A second ligaclip is being applied to the vessel that is to be divided.

    The vessel branch is being divided with scissors after application of two ligaclips proximal and distal to the site of sectioning. This will expose the axillary nerve branch beneath.

    The axillary nerve trunk is being directed free from scar in the quadrangular space. the space, viewed from posteriorly is bounded by the log head of triceps medially, the surgical neck of the humerus laterally, the lower border of the trees minor and the inferior shoulder capsule superiorly and the upper border of the trees major inferiorly. Viewed from the anterior aspect the lower border is bounded by the latissimus doors tendon which twists around the trees major lower borer before inserting into the floor of the bicipital (inter-tubercular) groove of the humerus with pectorals major inserting into the anterior lip and teres major inserting into the posterior lip.

    Following neurolysis and release of the axillary nerve the stimulation is repeated. n this case there was improved stimulation with good contraction of the deltoid and teres minor contraction at 1mA after mobilising and stimulating the proximal axillary nerve trunk.
    If stimulation remains poor and the space is tight, release of the upper tiers major tendon can increase the space. This is a useful strategy in the quadrangular space syndrome where symptoms are associated with compression of the axillary nerve plus a compression of the posterior circumflex humeral artery.
    In cases where there is a tumour that need resecting or severe scar, the long head of triceps tendon can be released partially to allow access and increase the space available for the neurovascular structures.

    Local anaesthetic is placed in the wound edges and the wound is closed in layers with 3’0 vicryl to the deep fascia and a continuous absorbable suture to the skin.

    Closure with a continuous absorbable suture.

    The dermis is closed with a continuous monaural suture.

    The completed wound closure. Steristrips can be applied and a waterproof dressing. the operated limb is placed in a polysling.

    Post Operative

    Following decompression for quadrangular space syndrome, or following neurolysis for a scarred axillary nerve, the limb should be mobilised and the patient is encouraged to use the arm as soon as comfortable within 48 hours. Physiotherapy can assist in functional use, strengthening and restoring range of motion. It is essential to enable nerve gliding to prevent post-operative scar formation that could tether the nerve and result in recurrent or persistent symptoms.
    In cases where there is no axillary nerve function and a nerve transfer is performed from a triceps branch, the arm should be rested in a polishing with a bedstraw to prevent abduction for 3 weeks. The technique of triceps to axillary motor nerve transfer is featured as a separate procedure on the OrthOracle platform.

    Recommended Reading

    There are a few cases reports reported in the literature. The syndrome is an usual cause of posterior shoulder pain, may present as isolation wasting of the deltoid, with loss of external rotation strength or difficulty with overhead activity. The syndrome my be identified following routine MRI imaging of the shoulder due to denervation oedema in the teres minor muscle. Physiotherapy should be attempted to alleviate the symptoms but many patients require decompression and the posterior approach is preserved.
    References
    1: Hangge PT, Breen I, Albadawi H, Knuttinen MG, Naidu SG, Oklu R. Quadrilateral
    Space Syndrome: Diagnosis and Clinical Management. J Clin Med. 2018 Apr 21;7(4)
    They report vascular and neurological symptoms and the challenges in making a diagnosis. They recommend conservative management initially with activity modification, physical therapy and massage. Surgery should be reserved for those without relief after conservative management.
    2: Flynn LS, Wright TW, King JJ. Quadrilateral space syndrome: a review. J
    Shoulder Elbow Surg. 2018 May;27(5):950-956
    This paper discusses the diagnostic challenges. Tenderness at the posterior quadrilateral space is a useful determinant and imaging with radiographs and MRI cannot make a diagnosis but can define other pathologies that may cause compression. The role of surgery is discussed after 6 months trial of conservative management. They do do define neurological and vascular subtypes although this was defined in the paper from the Mayo clinic in 2015 (detailed below).

    3: Rollo J, Rigberg D, Gelabert H. Vascular Quadrilateral Space Syndrome in 3
    Overhead Throwing Athletes: An Underdiagnosed Cause of Digital Ischemia. Ann Vasc
    Surg. 2017 Jul;42:63.e1-63.e6
    This paper details 3 cases of severe vascular compromise and digital emboli from propagating thrombosis following vascular compression in throwing athletes. Prompt surgical management is recommended. All patients returned to sport.
    4: Brown SA, Doolittle DA, Bohanon CJ, Jayaraj A, Naidu SG, Huettl EA, Renfree KJ, Oderich GS, Bjarnason H, Gloviczki P, Wysokinski WE, McPhail IR. Quadrilateral space syndrome: the Mayo Clinic experience with a new classification system and case series. Mayo Clin Proc. 2015 Mar;90(3):382-94. doi: 10.1016/j.mayocp.2014.12.012
    They report that the incidence of quadrangular space syndrome (QSS) is low however it is an under diagnosed condition that presents in athletes in activities requiring overhead activity. Untreated it may cause aneurysmal change in the PCHA and the risk of thrombosis or embolism. They propose a classification system for QSS and form analogies with thoracic outlet syndrome, determining that there is repetitive traction and trauma during activity resulting in predominant vascular symptoms with thrombosis or aneurysm and a predominant neurological subtype with fibrous bands or other static anatomical anomalies that result in a neurological compression even in the at rest position.

    5: Robinson P, White LM, Lax M, Salonen D, Bell RS. Quadrilateral space syndrome caused by glenoid labral cyst. AJR Am J Roentgenol. 2000 Oct;175(4):1103-5
    Other causes of axillary neuropathy should be considered and imaging can determine extrinsic compression from labral cysts, osteochondroma, callus and tumours. Intrinsic nerve tumours, although rare at this location, may present with axillary neuropathy and diffuse posterolateral shoulder pain.
    6: Lester B, Jeong GK, Weiland AJ, Wickiewicz TL. Quadrilateral space syndrome: diagnosis, pathology, and treatment. Am J Orthop (Belle Mead NJ). 1999 Dec;28(12):718-22, 725
    This review describes two surgically managed patients with detachment of the deltoid and teres minor to decompress the nerve. They suggest that invasive angiography is beneficial, however other papers dispute this viewpoint.
    7: Linker CS, Helms CA, Fritz RC. Quadrilateral space syndrome: findings at MR imaging. Radiology. 1993 Sep;188(3):675-6
    They report that fibrous bands in the quadrilateral space may cause compression of the axillary nerve and result in shoulder pain. MRI imaging demonstrated atrophy of the teres minor and they reported that this finding in the setting of appropriate symptoms is diagnostic for quadrilateral space syndrome which may respond to surgical decompression.
    8: Mochizuki T, Isoda H, Masui T, Ohkawa Y, Takahashi M, Takehara Y, Ichijo K, Kodaira N, Kitanaka H. Occlusion of the posterior humeral circumflex artery: detection with MR angiography in healthy volunteers and in a patient with quadrilateral space syndrome. AJR Am J Roentgenol. 1994 Sep;163(3):625-7
    10 PCHA were imaged with MRA: 1 in a symptomatic individual and 6 asymptomatic volunteers. they found all had normal appearance of the vessel in the sting position but the symptomatic individual and 80% of the healthy volunteers had vascular occlusion on arm elevation into abduction. The conclusion was that MRA has no role in diagnosing this condition.
    9: Cahill BR, Palmer RE. Quadrilateral space syndrome. J Hand Surg Am. 1983 Jan;8(1):65-9
    They report forward flexion or ABER positioning of the shoulder causing compression of the pCHA and axillary nerve. They used invasive angiography to confirm vascular compression. 18 cases not responding to conservative management had surgery with 8 having symptom resolution, 8 improved and 2 unchanged.

    Reference

    • orthoracle.com

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