Trapezius Anatomy

Origin (medial, continuous from occiput to T12)

• Medial third of the superior nuchal line and the external occipital protuberance.
• Ligamentum nuchae (spinous processes C1 to C6 by proxy).
• Spinous process of C7 and the spinous processes of all twelve thoracic vertebrae, plus their supraspinous ligaments.
• Around the C7-T3 level the aponeurotic origin widens into a diamond-shaped tendinous sheet shared with the opposite side - the trapezial aponeurosis. This is the thickest, most reliable tissue for suture purchase in a medial repair.

Insertion (lateral, three distinct footprints)

• Upper part: posterior border of the lateral third of the clavicle. This is the only part of the trapezius attached to the clavicle, and the reason the shoulder drops when it fails.
• Middle part: medial margin of the acromion and the superior lip of the crest of the scapular spine.
• Lower part: converges into an aponeurosis that glides over a small bursa at the medial end of the scapular spine and inserts into the tubercle at the apex of the medial (deltoid) end of the scapular spine.

Practical points

• The upper and middle parts share the acromioclavicular region with the deltoid origin; the two muscles are continuous in a common fascial sleeve, which is exploited in the trapezius transfer for deltoid paralysis.
• The inferior angle of the scapula receives no trapezius fibres - it is controlled entirely by serratus anterior and rhomboids.
• The free anterior border of the upper trapezius forms the posterior boundary of the posterior triangle of the neck and is the landmark by which the surgeon judges how far posteriorly a node biopsy may safely go.

Spinal accessory nerve (CN XI) - the sole motor supply

• Origin: the spinal root arises from anterior horn cells of the upper cervical cord (C1 to C5, principally C2 to C4), ascends through the foramen magnum, joins the cranial root briefly, then leaves the skull through the jugular foramen (in the same compartment as CN IX and CN X).
• Descent: passes deep to, or occasionally through, the sternocleidomastoid, which it supplies with a branch entering the deep surface at the junction of the upper and middle thirds.
• Posterior triangle: emerges from the posterior border of sternocleidomastoid at the junction of its upper and middle thirds, on average 1 cm cranial to the point where the great auricular nerve turns around the same border - the single most reliable intra-operative landmark. It then runs infero-posteriorly across the posterior triangle on the surface of levator scapulae, separated from levator only by the prevertebral fascia and lying immediately deep to the investing layer of deep cervical fascia within the fatty pad that contains level V lymph nodes.
• Entry into trapezius: passes deep to the anterior border of the trapezius approximately 2 to 5 cm above the clavicle (most series report 3 to 4 cm) and continues on the deep surface of the muscle, giving branches sequentially to the upper, then middle, then lower parts. Motor entry points are therefore staggered from cranial to caudal along a line paralleling the medial border of the scapula.
• Cervical plexus contribution: the C3 and C4 ventral rami join the nerve as it crosses the triangle, or enter the muscle independently. These carry proprioceptive afferents and, in a proportion of individuals, motor fibres to the middle and lower trapezius. This dual supply is why some patients retain partial lower trapezius function after a proximal CN XI transection - and why the examiner will ask whether CN XI is truly the sole motor nerve. The safe answer: CN XI is the dominant and clinically decisive motor supply; C3-C4 contributions are variable and mainly proprioceptive.

Length and depth

• The intra-triangular segment is only 4 to 6 cm long and lies less than 1 cm deep to the skin in a thin patient. Nothing protects it but fascia and fat.

Named vessels

• Superficial branch of the transverse cervical artery (the superficial cervical artery) - dominant pedicle to the upper and middle trapezius. Arises from the thyrocervical trunk, crosses the posterior triangle transversely just above the clavicle and enters the deep surface of the muscle. It is the pedicle of the upper trapezius (Conley) flap.
• Deep branch of the transverse cervical artery / dorsal scapular artery - descends deep to levator scapulae and rhomboids along the medial border of the scapula and supplies the middle and lower trapezius. It is the pedicle of the lower trapezius island flap, whose long arc of rotation reaches the occiput, the posterior skull base and the upper thoracic spine.
• Occipital artery - supplies the uppermost occipital fibres.
• Dorsal perforators of the posterior intercostal arteries - segmental supply to the lower fibres; these are the vessels that must be divided when the lower trapezius is islanded, and are the reason a purely distally based lower trapezius flap is unreliable.

Why the pedicle position matters

• The dorsal scapular artery runs 1 to 2 cm medial to the medial border of the scapula, deep to the rhomboids. Any medial parascapular dissection - Eden-Lange harvest, medial scapular winging surgery, scapulothoracic fusion - risks this vessel and a troublesome deep haematoma.
• Mapping the deep branch pre-operatively with Doppler or CT angiography is standard before a lower trapezius flap, because a dominant deep branch arising directly from the subclavian artery (a true dorsal scapular artery) is present in a substantial minority of shoulders.

Venous and lymphatic

• Venae comitantes drain to the transverse cervical and external jugular veins. The muscle's fascial roof contains the level V (posterior triangle) lymph nodes - the anatomical reason node biopsy and CN XI injury are inseparable topics.

Superficial to trapezius

• Skin, subcutaneous fat, and the supraclavicular nerves (C3, C4) crossing the clavicle. Sacrificing these during a posterior or superior approach gives anterior chest-wall numbness that patients notice more than the surgeon expects.

Deep to trapezius (from cranial to caudal)

• Splenius capitis and semispinalis capitis superiorly.
• Levator scapulae and the rhomboid minor and major - the plane the surgeon develops in the posterior scapular approach and in the Eden-Lange transfer.
• Supraspinatus and the supraspinous fossa laterally.
• Serratus posterior superior and the erector spinae inferiorly.
• Dorsal scapular nerve and artery running vertically 1 to 2 cm medial to the medial scapular border, deep to the rhomboids.

Boundaries it defines

• Posterior triangle of the neck: anterior border of trapezius (posteriorly), posterior border of sternocleidomastoid (anteriorly), middle third of clavicle (inferiorly). Contents at risk: CN XI, the cervical plexus cutaneous branches, the transverse cervical vessels, the external jugular vein, the upper trunk of the brachial plexus deep to the prevertebral fascia, and the thoracic duct on the left.
• Triangle of auscultation: medial border of the scapula (laterally), lateral border of trapezius (medially), superior border of latissimus dorsi (inferiorly), with the rhomboid major in the floor - the classic route to the posterior chest wall and to the 6th rib without dividing muscle.

Structures at risk in trapezius surgery

• CN XI in the posterior triangle and on the deep surface of the muscle.
• Suprascapular nerve at the suprascapular notch, 2 to 3 cm medial to the base of the coracoid, encountered once the trapezius is elevated off the scapular spine.
• Dorsal scapular nerve and artery medially.

Iatrogenic (the great majority)

• Posterior triangle lymph node biopsy - the commonest single cause. Typically an excision biopsy done for lymphadenopathy under local anaesthesia, without nerve monitoring, by a surgeon not expecting the nerve.
• Radical and modified radical neck dissection - classical radical neck dissection sacrifices CN XI by design; modified radical and selective dissections preserve it but still cause a traction neurapraxia in a substantial proportion ("shoulder syndrome" after neck dissection).
• Carotid endarterectomy, internal jugular vein cannulation, cervical rib resection, brachial plexus exploration.
• Facelift and parotid surgery where dissection strays into the upper posterior triangle.

Non-iatrogenic

• Blunt or penetrating trauma to the posterior triangle, including seat-belt and rugby injuries.
• Traction injury from a fall onto the shoulder with the head forced to the opposite side.
• Parsonage-Turner syndrome (neuralgic amyotrophy) - CN XI involvement is uncommon but described; look for other patchy palsies (long thoracic, suprascapular, anterior interosseous).
• Radiotherapy to the neck - late fibrotic neuropathy, often years afterwards.
• Skull base tumours and jugular foramen lesions - here CN IX, X and XI fail together (Vernet syndrome), so ask about swallowing and voice.

The classic history

A patient who had a neck lump removed weeks to months earlier presents with a dropped, aching shoulder and difficulty lifting the arm overhead or carrying a bag on that side. The pain is described as a dragging or burning discomfort over the trapezius and the medial scapular border, worse at the end of the day.

Examination findings

• Visible trapezial atrophy and a hollow above the scapular spine.
• Drooped shoulder with a widened, asymmetric neckline.
• Lateral scapular winging on abduction; the inferior angle swings laterally.
• Weak shrug, weak abduction above 90 degrees.
• Full passive range initially; a secondary adhesive capsulitis develops in the neglected case.

Diagnostic delay

Mean time from injury to diagnosis in published series is measured in months, often more than six. The reason is that the pain is attributed to "muscle spasm" or "post-operative stiffness" and the winging is never elicited because the patient is only asked to push against a wall.

Electrodiagnostics

• EMG and nerve conduction studies at 3 to 6 weeks and repeated at 3 months. Look for fibrillations and positive sharp waves in trapezius with sparing (or involvement) of sternocleidomastoid - SCM involvement localises the lesion proximal to the posterior triangle.
• Examine serratus anterior, rhomboids, supraspinatus and infraspinatus in the same study to exclude a more diffuse plexopathy or neuralgic amyotrophy.
• Persistent absence of voluntary motor units at 3 months and no advancing reinnervation at 6 months indicate exploration.

Imaging

• MRI of the trapezius: denervation oedema early (high signal on fluid-sensitive sequences), then fatty infiltration and volume loss in the chronic case. Fatty replacement of the whole muscle predicts a poor result from neurolysis or grafting and pushes the decision toward tendon transfer.
• Cervical spine MRI if the lesion is not clearly iatrogenic, to exclude a skull-base or foraminal cause.
• Radiographs of the shoulder to exclude a scapular osteochondroma or malunion causing pseudo-winging.

Baseline documentation

Photograph the resting posture and the abducted position. Objective serial photographs are more useful in the medicolegal setting - which these cases frequently become - than any narrative note.

The concept

Eden-Lange substitutes for each of the three parts of the trapezius by moving the surviving scapular stabilisers laterally, so that their line of pull becomes a stabilising and rotating vector rather than a purely medial one. All three donor muscles are innervated by the dorsal scapular nerve (levator scapulae also by C3-C4), so the transfer is only viable if the dorsal scapular nerve is intact - confirm this on EMG before committing.

The three limbs

• Levator scapulae is detached with a wafer of bone from the superior angle and transferred laterally onto the scapular spine, substituting for the upper trapezius.
• Rhomboid minor is detached from the medial border and transferred laterally onto the infraspinatus fossa, substituting for the middle trapezius.
• Rhomboid major is detached and transferred laterally onto the infraspinatus fossa, below the rhomboid minor, substituting for the lower trapezius.

Fixation

Each tendon is passed through a subperiosteal tunnel or a bone trough on the dorsal scapular surface and fixed with transosseous sutures or suture anchors through drill holes, with the arm held in about 30 degrees of abduction so the transfers are tensioned in a shortened position.

Why it was modified

The classical transfer relocates the levator only as far as the middle of the scapular spine. Because the lower trapezius has the dominant upward-rotation moment arm, patients with a persistent inferior-angle problem after classical Eden-Lange were shown to be under-corrected for downward rotation.

The modification

The levator scapulae is transferred further laterally, to the region of the acromion or the lateral scapular spine, lengthening its moment arm and giving a stronger upward-rotation vector; the rhomboid transfers are placed as far laterally on the infraspinatus fossa as the muscle excursion allows. Biomechanical cadaver work has confirmed that the lateralised levator transfer restores scapular kinematics closer to normal than the classical position.

Selection

• Best candidates: young, active patients with an irreparable complete CN XI lesion, intact dorsal scapular nerve, supple passive scapular motion and no glenohumeral arthritis.
• Contraindications: fixed scapular contracture, additional serratus palsy (which removes the other half of the upward-rotation couple), and painful glenohumeral degeneration.
• Outcome expectation: reliable pain relief and improvement in the neckline and droop; abduction improves but rarely returns to normal. Long-term follow-up shows the correction is durable in ISOLATED trapezius palsy - excellent or fair Constant outcomes in 11 of 12 patients at a mean of 32 years - whereas the failures occurred in patients who also had a long thoracic or dorsal scapular nerve lesion. Counselling should therefore turn on whether the palsy is truly isolated.

Scapulothoracic fusion

Reserved for the failed transfer or the patient with combined trapezius and serratus palsy (for example facioscapulohumeral dystrophy). It abolishes scapular winging and gives the deltoid a fixed base, at the cost of scapulothoracic motion and with real risks - pneumothorax, rib fracture, non-union, and a permanent reduction in the last 30 to 40 degrees of elevation.

Static suspension

Fascial or synthetic suspension of the scapula to the spinous processes or the clavicle has largely been abandoned because the static construct stretches out, but it retains a role in the low-demand or medically unfit patient whose main complaint is the drooping, painful shoulder.

Indication

Irreparable axillary nerve palsy with a flail deltoid, in a patient with an intact cuff, a supple shoulder and a normally functioning trapezius (CN XI intact). Typical setting: a late-presenting axillary nerve injury after anterior shoulder dislocation or a proximal humeral fracture, or a failed nerve transfer, where nerve reconstruction is no longer an option (usually more than 12 months from injury or with a fatty-infiltrated deltoid on MRI).

Technique (Bateman / Saha type transfer)

• Sabre-cut or strap incision over the lateral clavicle, acromion and scapular spine.
• The trapezius insertion is mobilised together with a block of bone, classically an osteotomised segment of the lateral clavicle and acromion, preserving the continuity of the muscle with its bony insertion.
• The bone block with the attached trapezius is transferred distally onto the lateral aspect of the proximal humerus, at or just distal to the level of the deltoid insertion, and fixed with screws through the bone block.
• Length is frequently insufficient, so an interposition graft (fascia lata, Achilles allograft or a tendon graft) is used to bridge the trapezius to the humerus, tensioned with the arm in 60 to 90 degrees of abduction.
• Immobilise in an abduction brace at 60 to 80 degrees for 6 weeks, then progressive weaning over 3 months.

Realistic outcome

Restores active abduction to around 60 to 90 degrees with reasonable pain relief; it is a salvage of function, not a restoration of normal deltoid. Compare with the alternatives: latissimus dorsi and teres major bipolar transfer (L'Episcopo type) to the proximal humerus, and arthrodesis in the manual labourer.

Indication

Irreparable posterosuperior rotator cuff tear with loss of active external rotation in a patient who still has a functional subscapularis, a preserved glenohumeral joint and no static superior escape. Also used for external-rotation restoration in brachial plexus birth palsy and in the young patient in whom reverse arthroplasty is undesirable.

Why the lower trapezius

Its line of pull is almost identical to that of the infraspinatus - infero-medial, in the plane of the scapula - so it reproduces the native external-rotation vector far better than a latissimus dorsi transfer, whose vector is anteroinferior. It is also in phase with external rotation during arm elevation, which shortens re-education.

Technique (Elhassan)

• Interscapular incision along the medial scapular spine; the lower trapezius is elevated from medial to lateral, protecting the spinal accessory nerve on the deep surface entering roughly at the junction of the medial and middle thirds of the muscle - the dissection must not extend more than a few centimetres cranial to the scapular spine at the medial border.
• An Achilles tendon allograft is sutured to the trapezius insertion to bridge the length deficit.
• A lateral incision or arthroscopic assistance is used to pass the graft beneath the deltoid and the remaining cuff, and to fix it to the infraspinatus footprint on the greater tuberosity with anchors, with the arm in 45 degrees of abduction and 45 degrees of external rotation.
• Brace in abduction and external rotation for 6 weeks; active external rotation from 6 to 12 weeks; strengthening after 3 months.

Outcome

Published series report reliable improvement in active external rotation and in pain, with the best results in patients with an intact subscapularis and no pseudoparalysis. Failure of the graft-to-tendon junction is the main mode of failure.

Upper trapezius (Conley) myocutaneous flap

Based on the superficial branch of the transverse cervical artery, raised as a laterally based flap for lateral neck and lower face defects. Predictable but sacrifices the shoulder-suspending fibres, so it exchanges a wound problem for a droop.

Lower trapezius island flap

Based on the deep branch of the transverse cervical artery / dorsal scapular artery, islanded on its pedicle after dividing the segmental intercostal perforators. It reaches the occiput, posterior skull base, posterior cervical and upper thoracic spine, and is the workhorse flap for a dehisced posterior cervical spinal wound with exposed instrumentation. Because the upper and middle fibres are preserved, shoulder function is largely maintained - the key advantage over the Conley flap.

Vascular caveat

Doppler or CT-angiographic identification of the pedicle is advisable: the deep branch may arise from the thyrocervical trunk or directly from the subclavian artery, and its course relative to the brachial plexus trunks differs accordingly.