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Modified Somsak nerve transfer (medial head of triceps nerve transfer to anterior division of the axillary nerve through a posterior approach)

    Overview

    Learn the Modified Somsak nerve transfer (medial head of triceps nerve transfer to anterior division of the axillary nerve through a posterior approach) surgical technique with step by step instructions on OrthOracle. Our e-learning platform contains high resolution images and a certified CME of the Modified Somsak nerve transfer (medial head of triceps nerve transfer to anterior division of the axillary nerve through a posterior approach) surgical procedure.
    The triceps to axillary nerve transfer was popularised by Somsak Leechavengvongs for the management of deltoid paralysis in the C5 avulsion brachial plexus injury. Modifications have been described using the medial triceps branch and transfer to the whole axillary nerve to re-innervate the anterior and posterior deltoid as well as the theres minor. I prefer the medial triceps branch because it avoids denervation of the bi-articular long head of triceps which is important to maintain posterior shoulder stability in an otherwise paralysed shoulder. In addition the medial triceps has a greater motor axon density. I perform co-aptation to the anterior division in a pure axillary nerve lesion or to the anterior and posterior divisions after removal of the fascicle to the upper lateral cutaneous nerve of the arm from the posterior division in a C5 lesion. The latter technique provides restoration of external rotation through re-innervation of the theres minor. Restoration of external rotation in a C5 lesion is often weak when the traditional Somsak transfer to the anterior division is combined with spinal accessory transfer to the supra scapular nerve. The rationale for this technique will be discussed further in the spinal accessory to supra scapular nerve section.

    Indications

    INDICATIONS:
    Triceps to axillary nerve transfer is used in partial plexus injuries where the C5/6 component is damaged and the C7/8 and T1 are intact. The typical indication is in the C5 or C5/6 avulsion injury but it may also be used in cases of C5/6 rupture where presentation is delayed, grafting of the upper trunk has not been successful or in continuity lesions of the upper trunk that failed to reinnervate. It may also be used to salvage the axillary nerve rupture at the quadrilateral space associated with high energy shoulder dislocation or the rare non-recovering isolated lesion in continuity of the axillary nerve following a low energy shoulder dislocation.
    Triceps nerve branch transfer to axillary nerve surgery should be undertaken early (0-3/12) post injury in confirmed cases of C5/6 avulsion but may be delayed (3-6/12) when the donor nerve has a partial low-grade axonopathy injury and progressive improvement is observed. Late transfer (6-9/12) can be undertaken as a salvage in delayed presentation, failed recovery though an early graft of the upper trunk or in continuity lesions where there is no evidence of clinical or electromyographic recovery. Recovery after 9/12 is unpredictable but may be beneficial in continuity lesions with non-functional motor recovery (grade 2) such as seen in C5 severe recalcitrant motor radiculopathy. The window for recovery in such cases is typically longer than the 12 months seen in complete peripheral nerve injury.
    SYMPTOMS & ASSESSMENT:
    Patients with C5 paralysis will have no shoulder abduction or external rotation. There will be sensory loss in the outer aspect of the upper arm from the deltoid to the lateral elbow. Loss of shoulder abduction and forward flexion means that the forearm, wrist and hand cannot be used functionally in the normal working space of the upper limb. Nerve pain may accompany a nerve root avulsion with pain experienced in the C5 cutaneous territory.
    INVESTIGATION:
    Neurophysiology and electromyography can be used to confirm the diagnosis of a complete C5 lesion. typically there is fibrillation within the deltoid muscle with increased insertional activity on needle placement. There will be no motor unit potentials. Other C5 innervatd muscles may be similarly affected. Ultrasound of the rotator cuff may be required to assess the supraspinatus and infraspinatus when the paralysis accompanies an infraclavicular brachialplexus injury and there is no useful shoulder function. Concomitant injury to the suprascapular nerve is possible and my be amenable to a nerve transfer which is described elsewhere. However typically in such cases the injury is an isolated axillary nerve rupture in the quadrilateral space, the sensory impairment is limited to the upper lateral cutaneous nerve of the arm over the deltoid insertion and the cuff dysfunction is due to either a pre-existing degenerative tear or traumatic tear associated with the shoulder dislocation.
    OPERATIVE ALTERNATIVES:
    In an isolated axillary nerve injury consideration should be given to exploration and graft reconstruction. In such cases the functional results are generally good if the injury is explored early. There are no good musculotendinous transfers for shoulder abduction. Transfer of the trapezius to the greater tuberosity may provide some abduction. With an intact supraspinatus patients with isolated axillary nerve palsy may have reasonable shoulder abduction, however initiation of abduction may be impaired. Glenohumeral arthrodesis may be offered to combined axillary and supraspinatus palsy when nerve reconstruction is not possible or the patient is referred beyond the window for successful nerve transfer (9-12 months)
    NON-OPERATIVE ALTERNATIVES:
    The re are no good alternatives for patients with deltoid paralysis. The flail shoulder can be braced with orthoses and in severe cases with preserved distal function in the forearm and hand there s interest developing in the use of exoskeletons to support the flail paralysed upper limb segment. The cost and limited availability mean that there is little uptake.
    CONTRAINDICATIONS:
    Nerve reconstructive surgery for a complete lower motor neurone injury of the axillary nerve will be unsuccessful when the deltoid muscle has been denervated for more than 12 months. If there is severe shoulder pain and stiffness then there is little benefit in nerve transfer surgery and a patient would be best treated with a glenohumeral arthrodesis.

    Setup

    The patient is placed in the lateral position with the left (operated) side uppermost. The torso should be supported with posts posteriorly at the lower lumbar spine and anteriorly at the anterior superior iliac spines. The operated arm should be supported in a gutter. An alternative position is to perform the operation in the prone position. I avoid this position because of a concern regarding traction on the brachial plexus and the added anaesthetic challenges including the need for neuromuscular blockade at induction.
    General anaesthesia is required and either short acting or no neuromuscular paralysis is essential. Intra-operative nerve stimulation is a mandatory requirement for this procedure and successful nerve transfer can only be achieved after confirmation of normal stimulation in the donor nerve and absent stimulation in the recipient.
    I use a regional anaesthesia block needle with stimulation provided by an aesthetic nerve stimulator which provides a range of stimulation from 0.02mA to 5mA at a frequency or 60Hz. The needle is covered with an arthroscopy camera drape and the circulating team activate the stimulator and make the adjustments as requested by the operating team. The patient requires an electrode outside the operative field to complete the circuit.
    During dissection and localisation of nerves a Mixter (90 degree fine pointed clip) is a convenient way of passing tagging and insulating colour-coded surgical rubber sloops around nerves. These rubber sloops allow gentle traction on a nerve for the neurolysis and mobilisation and minimise handling of the epineurium. They provide an insulation against cross stimulation to adjacent nerves when used to lift a nerve during assessment with higher stimulation thresholds.
    An operating microscope should be available. A set of surgical micro-instruments is essential for performing nerve transfer surgery. Neurotomes enable clean nerve transection without crush injury and serrated microsurgical scissors are useful for debriding epineurium. The co-aptation is performed using curved needle holders and 8’0 or 9’0 monofilament non-absorbable suture depending on the diameter of the nerve transfer at the co-aptation site.
    TisseelTM is used as a biological tissue glue (fibrin) to support the co-aptation site and minimise the need for sutures which may distort the nerve ends and create scar at the neurorraphy site.


    Operation – 1

    This image demonstrates the anatomy of the posterior aspect of the right shoulder with the elbow at the bottomof the clinical photograph.
    Axillary nerve fibres arise from the posterior division of C5; the posterior divisions of the upper, middle and lower trunks join to form the posterior cord; the axillary nerve arises as a terminal branch from the posterior cord with the branches to triceps (long, lateral and medial) and the radial nerve.
    The axillary nerve passes posteriorly around the humerus through the quadrilateral space where it branches into anterior and posterior divisions. The axillary nerve is accompanied by the posterior circumflex humeral artery and vein. The quadrilateral space boundaries are the long head of triceps medially, the shoulder capsule superiorly, the surgical neck of the humerus laterally and the upper border of teres major inferiorly.
    The anterior division passes under the deltoid muscle to supply the anterior supplying innervation to the muscle from its deep surface. The posterior division supplies deltoid, a branch to teres minor and the upper lateral cutaneous nerve to the skin of the arm overlying the deltoid muscle.
    The radial nerve exits the posterior wall of the axilla through the triangular space accompanied by the branches to triceps and the profunda brachii artery and vein.
    The superior boundary of the triangular space is the inferior border of teres major (seen from posteriorly the white tendon of latissimus dorsi overlies the teres major and rolls under its lower margin to insert in the floor of the intertubercular groove on the medial humerus). The lateral margin is the humeral shaft and the medial margin is the lateral border of the long head of triceps muscle-tendon unit.

    The patient is positioned in the left lateral position and the right arm is draped over a gutter support. The support should be padded and care must be taken to ensure that there is no pressure exerted directly on the axillary vessels and nerves. The elbow is seen at the top of the clinical photograph. The operator stands on the posterior aspect of the shoulder.
    Make a 10cm longitudinal curvilinear incision on the posterior arm starting at the level of the quadrilateral space following the posterior border of deltoid and continue distally along the midpoint of triceps. the deltoid is wasted which facilitates the exposure of the axillary nerve using this approach.

    The skin is incised and monopolar diathermy with an epitome blade is used to develop the incision to the deep fascia.

    A Travers self retaining retractor is placed in the wound edges and used to assist exposure.

    Lift up the skin flaps and look for the upper lateral cutaneous nerve of the arm (ULCNA) where it pierces the deep fascia and enters the deep surface of the skin of the upper arm. The branch can be confirmed by gentle traction, which dimples the skin. Place a surgical rubber loop around the nerve using Mixter forceps.

    The sloop will enable gentle traction on the nerve branch to assist dissection and mobilisation. The ULCNA can be used to trace deep to the posterior division of the axillary nerve from which it arises. In turn the posterior division can be traced deep to the quadrilateral space to identify the main axillary nerve trunk which may then be traced anteriorly to identify the anterior division of the axillary nerve as it courses around the proximal humerus, deep to the deltoid, approximately 5cm lateral and distal to the lateral border of the acromion process.

    ULCNA – Upper lateral cutaneous nerve of the arm
    D – Deltoid
    LaHT – Lateral head of triceps
    LoHT – Long head of triceps
    The ULCNA is neurolysed and the dissection proceeds through the deep fascia exposing the deltoid muscle and posteriorly the quadrilateral space. Split the fascia at the point where the ULCNA pierces and then trace this branch back to the posterior division of the axillary nerve in the quadrilateral space. Follow the posterior division deep until the anterior division is identified and then trace this distally to the deltoid muscle. The anatomy in the space may be difficult to define and axillary vessels may cross the nerve branches.

    The quadrilateral space can be palpated with the operator’s index finger. The boundaries are superiorly the capsule of the shoulder, medially the surgical neck of the humerus, laterally the long head of the triceps and inferiorly the upper border of the teres major muscle. The axillary nerve exits the quadrilateral space on the posterior aspect of the shoulder with the posterior circumflex humeral artery.

    If the ULCNA can not be identified I would recommend identifying the anterior division of the axillary nerve directly. The anterior division passes deep to the posterior border of the deltoid muscle approximately 5cm distal to the posterolateral corner of the acromion. There are usually two main branches and lifting the deltoid using a retractor placed more proximally facilitates this exposure without risking damage to the nerve branches. Use a rubber surgical loop to tag the anterior and posterior divisions of the axillary nerve.
    AA – Surface marking for the anterior division of the axillary nerve

    The anterior division of the axillary nerve is mobilised as it passes deep to the posterior border of deltoid. there are usually two branches at this point and the nerve is accompanied by a vascular pedicle. A pair of Mixter forceps is passed deep to the nerve to facilitate passage of a surgical rubber sloop.

    A yellow sloop is used to identify the anterior division of the axillary nerve which will be the target for the nerve transfer.

    ULCNA – Upper lateral cutaneous nerve of arm
    AA – Anterior division of the axillary nerve
    PA – Posterior division of the axillary nerve (deltoid branch)

    The sloops can be used to mobilise the tagged nerve branches to define the anatomy. Here the posterior division of the axillary nerve branch to deltoid is identified. It is much smaller than the anterior division. The ULCNA arises from the posterior division of the axillary nerve which has branches to teres minor and to deltoid.

    ULCNA – Upper lateral cutaneous nerve of arm
    AA – Anterior division of the axillary nerve
    PA – Posterior division of the axillary nerve (deltoid branch)
    AN – Main trunk of the axillary nerve

    Each of the branches is stimulated to confirm the anatomy and to ensure that there is no residual function or recovered function in the axillary nerve.

    The sloops are mobilised to the proximal wound and left free without clips which could create a traction injury or result in inadvertent avulsion. The interval between the Lateral and long head of triceps is identified and gentle digital dissection develops the plane and the radial nerve can be palpated against the humeral shaft with the profunda brachii artery. The Travers retractor can then be positioned more deeply in the wound. care must be taken to avoid damaging the delicate motor branches to the triceps muscle heads.

    Identify a fat streak on the triceps and then at this point develop the interval between the long and lateral heads of triceps using gentle finger dissection and carefully place a self-retaining retractor in this interval taking care not to position the jaws deep to the muscle because this can risk damage to the triceps branches. The radial nerve courses from proximal medial to distal lateral as it enters the spiral groove of the humerus.
    LaHT – Lateral head of triceps
    LoHT – Long head of triceps
    TM – Teres major
    RN – radial nerve

    The radial nerve (RN) is exposed in the triangular space. There is a separate motor branch to the medial head of the triceps lying superficial to the main radial nerve trunk with the posterior cutaneous nerve of the arm. The teres major tendon is cleared of soft tissue. The teres major is the boundary between the quadrilateral and triangular spaces viewed from posteriorly.

    The white tendon of latissimus dorsi should be seen separating the quadrilateral space (axillary nerve) from the triangular space (radial nerve and triceps branches). The triceps branches lie in close proximity to the radial nerve and each should be tagged with a surgical loop. The posterior cutaneous nerve of the arm lies on top of the main radial nerve and can easily be confused with the medial triceps branch. Use a pair of Mixter forceps to pass a sloop around the superficial branches so that they can be further identified with nerve stimulation.

    The motor branch to the medial head of triceps is being lifted away from the main radial nerve. At this point it is always a separate branch lying in loose connective tissue.

    A yellow sloop is used to identify this donor nerve branch.

    The sloop is delivered under the medial triceps nerve branch with care to avoid traction on the branch of catching the deep surface of the nerve in the jaws of the Mixter forceps.

    The chosen nerve branch can be lifted away from the main radial nerve for confirmation of the anatomy with nerve stimulation to avoid direct cross stimulation of the radial nerve. The sloop can then be used to assist neurolysis to mobilise sufficient donor nerve branch length without excessive direct handling of the nerve which could otherwise create damage.

    The other proximal branches can be tagged with sloops to confirm the anatomy on stimulation. I use colour coding to ensure that the correct branch is tagged and sectioned for the transfer.
    Yellow – Donor branch: Medial head triceps motor branch
    Red – Posterior cutaneous nerve of the arm
    White – Lateral head of triceps motor branch
    Blue – Long head of triceps motor branch.
    The other sloops in the proximal wound are tagging the axillary nerve branches. The recipient anterior division of the axillary nerve is similarly tagged with a yellow sloop to help with the subsequent dissection and branch mobilisation.

    Nerve stimulation confirms the anatomy. Note in the yellow sloop there is a double branching nerve. The medial triceps typically has two branches one of which also supplies the anconeus. Both can be harvested for a greater number of motor axons. In some cases where the branches are large I have taken a single branch maintaining function within the medial head of triceps. Confirmation of the radial nerve is through active wrist and finger extension. The triceps medial head contraction can be seen in the wound and palpated at the posterior elbow.

    Neurolysis of the medial triceps branch is performed to separate the branch from the radial nerve as far as the inferior border of the teres miajor tendon.

    Operation – 2

    The distal medial triceps branch has also been mobilised to the triceps muscle so that there is sufficient length for transfer to the anterior division of the axillary nerve close to the motor point.

    The medial triceps branch is sectioned at the muscle to have sufficient length for transfer. Section should be under direct vision to avoid damage to any of the other branches.

    The sectioned medial triceps branch is reflected proximally and placed on a microsurgery background that is positioned on the teres major tendon. There are two fascicles seen within this nerve branch. The anterior division of the axillary nerve is still attached to the main axillary nerve and is lying in the yellow sloop proximally and anteriorly in the wound.

    The medial triceps fascicles are teased apart. There is an opportunity to direct one fascicle to the anterior deltoid and another to the teres minor. In this case I decided to direct section the donor medial triceps branch more proximally with a neurotome and then to transfer to the anterior division of the axillary nerve in isolation to try and regain functional use in the deltoid muscle which was the main functional loss for the patient. The anterior division of the axillary nerve is about to be sectioned from the axillary nerve proximally.
    REMEMBER: “Donor distal and recipient proximal” when undertaking the neurotomies for nerve transfer.

    Following preparation of the medial triceps donor branch the anterior division of the axillary nerve has been sectioned proximally. There is plenty of length and redundancy is trimmed from the recipient nerve to bring the neurorraphy closer to the motor point of the deltoid and reduce the reinnervation distance and time.

    The anterior division of the axillary nerve is trimmed. Note that the neurorraphy can still be performed without tension. Also note that the anterior division branches in to two main nerves as it passes deep to the posterior fibres of the deltoid muscle. This is a consistent finding. the medial triceps double fascicle and the whole of the anterior division of the axillary nerve are a good size match for transfer.

    The nerve branches are approximated on the microsurgery background in preparation for the nerve transfer co-aptation under the operating microscope.

    The microscope is positioned over the wound to allow the operator and assistant access for the neurorraphy.

    There is bleeding from the cut nerve ends confirming healthy tissues. The blood can be irrigated away with saline. Diathermy must never be used on or near the nerve branches.

    This image shows the microsurgical neurorraphy under the operating microscope. 5 x 9’0 nylon sutures are placed around the neurorraphy at approximately 70 degrees of separation to allow the nerve ends to contact each other without distortion.

    The completed neurorraphy is supported with TisseelTM fibrin glue. This acts to support the nerve transfer, seal the epineurium and provide some resistance to traction along the nerve branches.

    The wound is closed in layers. The deep fascia is closed with 2’0 vicryl.

    The superficial closure is with an absorbable monofilament interrupted approximation of the superficial fascia.

    The skin is closed with a continuous monofilament absorbable suture.

    Local anaesthetic is infiltrated to the wound edges. Steristrips are used to support the subcuticular closure. An occlusive dressing is applied. this procedure was performed at the same time as a nerve transfer from the XIth nerve to the suprascapular nerve (SSN) through a posterior approach. The dressing in the foreground of the clinical photograph is from that other procedure. The XI to SSN transfer is described separately on OrthOracle.

    Post Operative

    This procedure may be performed in combination with spinal accessory to suprascapular nerve transfer for C5 nerve root injuries and in combination with nerve transfers to biceps and brachialis when there is also involvement of the C6 nerve root. These procedures will be featured elsewhere in OrthOracle.
    A waterproof dressing with absorbent pad is applied to the wound. The wound should be kept clean and dry for 7 days after which the patient can shower then replace the dressing. A polysling is applied to the upper limb with a torso strap around the waist before the patient wakes from surgery. The polysling and torso strap should be maintained for 3 weeks to prevent excessive passive movement at the shoulder.
    During this phase the patient is encouraged to maintain isometric contraction of the donor muscle in the sling and to visualise the combination of trapezius activation and shoulder abduction and external rotation.
    Nerve transfer rehabilitation involves a 6-phase programme of activity developed at the Centre for Nerve Injury and Paralysis, Birmingham, UK.
    Phase 1 – Pre-operative phase: Education and donor optimisation. Introduction to trophic stimulation and the concept for functional electrical stimulation (FES).
    Phase 2 – Protection phase: During the immediate post-operative period the nerve transfer is protected from inadvertent injury with the arm immobilised. Isometric contraction of the donor and visualisation of the combination donor-recipient action is performed during this period which typically lasts 3 weeks.
    Phase 3 – Prevention phase: During this phase the arm is mobilised and neural gliding is commenced. Joint range of motion exercises (active and passive) are commenced to prevent joint contractures developing. The isometric exercises are continued and isotonic and eccentric exercises are commenced for the donor muscle to maintain function and restore strength. Functional stimulation can be commenced on the donor muscle. Trophic stimulation can be maintained on the recipient muscle.
    Phase 4 – Power phase: During this period the donor muscle is strengthened and the recipient muscle starts to respond. Typically the first sign of reinnervation is a tender muscle squeeze sign due to small fibre reinnervation. Typically this is 3 months following transfer but is affected by the distance of the co-aptation from the recipient motor point.Visible flickers of contraction follow within 6 weeks and donor activation potentiate the recipient response. FES continues and the phase lasts for approximately 6-12 months during which useful motor grade returns: Medical Research Council – (MRC) Grade 3-4.
    Phase 5 – Plasticity: During this phase the patient works on activation of the recipient muscle without activation of the donor. This phase can overlap with phase 4 and is guided by a therapist specialised in nerve transfer rehabilitation.
    Phase 6 – Purpose: During this phase the patient introduces function tasks discussed as objectives during the pre-operative phase. This period of training is tailored to the individual and includes work hardening. Improvements are typically found in power and functional performance for at least 2 years following nerve transfer surgery.
    Outcomes assessment can be with MRC scales but because of the huge functional variation within MRC Grade 4, I prefer absolute muscle testing with digital myometry and comparison with the contralateral limb. In addition fatigue testing and functional scores are important. The EQ5D, DASH and the BrAT scores are in common use in assessing upper limb function after brachial plexus injury. The Canadian Occupational Performance Measure (COPM) is an ideally suited tool to assess patient specific objectives and outcomes.

    Recommended Reading

    Adolf Stoffel described the technique of triceps to axillary nerve transfer via an anterior approach in 1911 in a textbook of orthopaedic surgery “Orthopadische Operationslhere” published in 1913. This text was never translated from German and the technique did not receive wide uptake.
    Somsak Leechavengvongs published two papers in 2003 on the anatomy and clinical outcomes of long head of triceps transfer to the axillary nerve.
    Susan Mackinnon published the transfer of the medial triceps branch as part of a double posterior nerve transfer to the shoulder in 2006.
    Jayme Bertelli published a paper on the anterior approach for triceps to axillary transfer in 2007 and using the lower medial triceps branch to anconeus as donor in 2014.
    Author’s note:
    The medial triceps branch is larger than the long head branch with more motor axons and therefore it may be transferred to the whole axillary nerve after dissection of the upper lateral cutaneous nerve fascicles. This gives potential for improved shoulder external rotation through teres minor. The long head is a good size match for the anterior division of the axillary nerve and can be used as an adjunct to grafting the upper trunk where some recovery may occur across the graft into the posterior division. I prefer the medial branch because of the extra length which is useful if there is damage to the axillary nerve at the quadrilateral space. When the medial branch has a clear division it is possible to take one branch and preserve the function of the medial head of triceps (power and control of extension at the elbow in the deep elbow flexion position). In isolated axillary nerve palsy 75% of patients regain a functional MRC grade 4 power after transfer to the axillary nerve.
    References:
    Orthopadische Operationslhere. “Operationen am nervensystem” Oskar Vulpius and Adolf Stoffel. Publshed by Ferdinand Enke, Stuttgart, 1913
    Nerve Transfer to Deltoid Muscle Using the Nerve to the Long Head of the Triceps, Part I: An Anatomic Feasibility Study: An anatomical feasibility study. Witoonchart K, Leechavengvongs S, Uerpairojkit C, Thu-Vasethakul P, Wongnopsuwan V. J Hand Surg 2003;28A:628–632
    Posterior approach for double nerve transfer for restoration of shoulder function in upper brachial plexus palsy. Colbert SH, Mackinnon S. Hand 2006;1(2):71-7
    Axillary nerve repair by triceps motor branch transfer through an axillary access: anatomical basis and clinical results. Jayme Augusto Bertelli, Paulo Roberto Kechele, Marcos Antonio Santos, Hamilton Duarte, Marcos Flávio Ghizoni.
    Journal of Neurosurgery August 2007; Vol. 107 No.2:370-377
    Nerve transfer from triceps medial head and anconeus to deltoid for axillary nerve palsy. Bertelli JA, Ghizoni MF. J Hand Surg Am. 2014 May;39(5):940-7

    Reference

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