Levator Scapulae Anatomy

Origin

• Posterior tubercles of the transverse processes of C1 to C4, by four separate tendinous slips.
• The C1 (atlas) and C2 (axis) slips arise from the transverse processes themselves; C3 and C4 slips arise from the posterior tubercles.
• The slips fuse into a single flattened belly as they descend inferolaterally.

Insertion

• The medial (vertebral) border of the scapula, from the superior angle down to the root of the scapular spine - a footprint typically 3 to 5 cm long.
• The bulk of the insertion is concentrated at and just below the superior (superomedial) angle, and the tendon is thickest here.
• Some fibres blend with the deep surface of the rhomboid minor insertion, so the two are difficult to separate cleanly at the border.

The 180-degree twist

The fibres rotate through almost 180 degrees as they descend: the slip from C1, the most cranial origin, inserts most caudally on the scapula, and the slip from C4 inserts most cranially at the superior angle. This spiral is a favourite anatomical question and has a practical consequence - the muscle cannot be split longitudinally along an internervous plane, because the fibres from different roots are interleaved.

Bony detail at the insertion

• The superomedial angle is thin, and its ventral surface may carry a bony prominence known as Luschka's tubercle - a hooked or curled anteriorly projecting corner. It is a recognised cause of mechanical scapulothoracic snapping and is the target of superomedial angle resection.
• The angle lies at approximately the T2 spinous process level with the arm at the side.

Dual supply

• Direct branches from the ventral rami of C3 and C4 (cervical plexus), entering the muscle on its deep surface in the posterior triangle. These are present in essentially everyone and provide the dominant supply.
• Dorsal scapular nerve (C5) also supplies the muscle, entering the deep surface as the nerve passes from the middle scalene toward the rhomboids. In a cadaveric series of 23 dorsal scapular nerves the nerve reached levator scapulae in every specimen, and in about half (48 per cent) it supplied levator scapulae alone, never continuing to the rhomboids.
• Overall root value is therefore commonly given as C3, C4 and C5.

Why the dual supply is examined

• Because the C3 and C4 supply is separate and more proximal, levator scapulae function is frequently preserved after an isolated dorsal scapular nerve lesion, whereas the rhomboids are not. Conversely, because about half of dorsal scapular nerves supply levator alone and never reach the rhomboids, a lesion of that nerve can denervate levator with intact rhomboids. Denervation of both points to the C5 root or the cervical plexus rather than to a peripheral scalene entrapment.
• It also explains why levator function is variably spared in spinal accessory nerve palsy: the trapezius is denervated but the levator, with its own supply, continues to lift the superior angle, contributing to the drooped-but-hitchable shoulder seen in some patients.

Motor entry

Branches enter the deep (anterior) surface of the muscle in its middle third, within the floor of the posterior triangle. This is the surface a surgeon must respect when mobilising the muscle for transfer.

Named vessels

• Dorsal scapular artery - the dominant pedicle, running with the nerve deep to the muscle before continuing under the rhomboids. It arises either as the deep branch of the transverse cervical artery or directly from the third part of the subclavian artery.
• Ascending cervical artery, a branch of the inferior thyroid artery from the thyrocervical trunk, supplies the upper part of the muscle in the neck.
• Transverse cervical artery contributes at the mid-belly.
• Vertebral artery muscular branches supply the uppermost origin slips near the transverse processes.

Pedicle position - the surgical fact

• The dorsal scapular vessels enter the deep surface of the muscle close to the superomedial angle and then descend 1 to 2 cm medial to the medial scapular border. That entry point sits directly in the field of a superomedial angle resection and of a superomedial arthroscopic portal - the reason both are hazardous.
• The transverse cervical vessels cross the posterior triangle on the surface of the levator, immediately deep to the investing fascia and alongside the spinal accessory nerve.

Practical implication

When mobilising the levator for an Eden-Lange transfer, dissect on the superficial (posterior) surface and free the muscle by working from lateral to medial at its insertion, keeping the deep-surface pedicle and nerve entry intact. Excursion is limited by that pedicle.

In the neck

• Superficial (posterior) to it: the investing layer of deep cervical fascia, the spinal accessory nerve crossing the posterior triangle on the surface of the levator, the cutaneous branches of the cervical plexus, and the transverse cervical vessels. Superiorly the sternocleidomastoid overlies it; inferiorly the trapezius.
• Deep (anterior) to it: the splenius cervicis, the posterior and middle scalene muscles, the cervical transverse processes, and, at the root of the neck, the brachial plexus roots emerging between anterior and middle scalene.
• It forms part of the floor of the posterior triangle, together with splenius capitis, the scalenes and semispinalis capitis.

At the scapula

• Superficial: trapezius.
• Deep: the superomedial angle of the scapula, the supraserratus and infraserratus bursae and the serratus anterior on the costal surface, with the second and third ribs beyond.
• Adjacent: rhomboid minor immediately inferior, often blending with it.

Structures at risk

• Spinal accessory nerve lying on the muscle in the posterior triangle - the reason a node biopsy over the levator is dangerous, and the reason a superomedial arthroscopic portal is discouraged.
• Dorsal scapular nerve and artery on its deep surface and at the superomedial angle.
• Pleura and the second and third ribs immediately deep to the superomedial angle - millimetres away during angle resection or bursectomy.

The condition

Snapping (or crepitant) scapula syndrome is painful, audible or palpable crepitus arising from the scapulothoracic articulation. The superomedial angle is the commonest site, followed by the inferior angle.

The anatomy of the space

Cadaveric work has defined two triangular scapulothoracic spaces separated obliquely by serratus anterior:

• The serratus anterior space (infraserratus) - bounded by the chest wall anteriorly, serratus anterior posteriorly and the rhomboids medially. It contains a well-defined bursa and is the space entered at arthroscopy.
• The subscapularis space (supraserratus) - bounded by serratus anterior anteriorly, subscapularis posteriorly and the axilla laterally.

In addition, adventitial bursae develop at the superomedial angle and at the inferior angle in response to chronic friction; these are acquired, not constant, and are the ones that hurt.

Causes of the snap

Management pathway

1. Non-operative first, and for at least 3 to 6 months. Postural correction, scapular retraction and upward-rotation strengthening (serratus and lower trapezius), levator and pectoralis minor stretching, activity modification, and analgesia.
2. Ultrasound-guided bursal injection - both therapeutic and, crucially, diagnostic.
3. Surgery only for the patient whose pain is abolished by the diagnostic block and who has failed structured rehabilitation. Options are bursectomy alone, or bursectomy with superomedial angle resection where imaging shows a bony prominence, performed open or arthroscopically.

What it is

A painful insertional enthesopathy and myofascial trigger point at the levator's attachment to the superomedial angle. It is one of the commonest causes of the combined neck-and-shoulder-blade ache seen in general practice, and it is frequently mislabelled as "trapezius strain" or "cervical spondylosis".

Presentation

• Deep aching pain at the superomedial angle, referring up the side of the neck and occasionally to the shoulder.
• Aggravated by sustained sitting with an unsupported arm, carrying a bag, driving, and by holding the head turned away from the painful side.
• Restricted contralateral cervical side-bending and rotation, with pain reproduced when the shoulder is depressed at end range.
• A palpable, exquisitely tender taut band at the insertion.

Distinguishing it from snapping scapula

• Levator scapulae syndrome hurts at rest and with neck position; snapping scapula hurts with arm motion and produces crepitus.
• The two coexist frequently, which is why treating only one disappoints.

Management

Postural and ergonomic modification, specific levator stretching (side-bend and rotate away, then flex, with the shoulder depressed), scapular stabilisation work, dry needling or trigger point injection performed tangentially under ultrasound, and management of any underlying cervical or shoulder pathology driving the compensation. Surgery has no role in isolated levator scapulae syndrome.

Denervation

• Dorsal scapular nerve lesion at the middle scalene may denervate the levator in the roughly 50 per cent of people in whom it carries the supply; combined levator and rhomboid denervation on EMG is the pattern.
• C3-C5 root pathology denervates it reliably. A cervical MRI is indicated if levator denervation is found without an obvious peripheral cause.

Cervical dystonia and torticollis

The levator is a frequent target for botulinum toxin in laterocollis and in the shoulder-elevation component of cervical dystonia, because it both side-bends the neck and elevates the scapula. In congenital muscular torticollis the sternocleidomastoid is the primary muscle, but secondary levator shortening contributes to the fixed posture and must be addressed in rehabilitation.

Sprengel deformity and Klippel-Feil syndrome

The scapula is elevated, small and medially rotated, and the levator is short and often fibrotic. An omovertebral bar - a fibrous, cartilaginous or bony bridge between the superomedial angle and a lower cervical spinous process, transverse process or lamina - may be present, running in and around the levator. In the Woodward procedure the trapezius and rhomboid origins are detached from the spinous processes and moved caudally; the omovertebral bar and the superomedial angle are excised, and the levator is released - with the brachial plexus at genuine risk during caudal translation of the scapula, which is why the superomedial angle is resected first to reduce the required translation.

Levator scapulae in scapular dyskinesis

An over-active levator holding the scapula in downward rotation and anterior tilt narrows the subacromial space and contributes to secondary impingement in the overhead athlete. The rehabilitation target is serratus and lower trapezius activation with levator and rhomboid down-training.

Indication

Symptomatic snapping scapula localised to the superomedial angle, with pain abolished by a diagnostic bursal block, refractory to at least 3 to 6 months of structured rehabilitation, and with a bony prominence or symptomatic bursa demonstrated on CT or MRI.

Technique

• Prone or lateral position, arm draped free so it can be placed in the "chicken wing" position (internal rotation with the hand behind the back), which lifts the medial border away from the chest wall.
• Incision along the medial border from the superior angle distally for 6 to 8 cm.
• Trapezius is split or elevated; levator scapulae and rhomboid minor are detached from the superomedial angle, leaving tendinous cuffs on the muscle for repair. This detachment is unavoidable - the levator insertion sits on the bone you are removing.
• The infraserratus (scapulothoracic) bursa is excised.
• The superomedial angle is resected with an osteotome or saw as a triangular wedge. Resection is deliberately limited - a wedge of the order of 2 cm along each of the superior and medial borders is typical. Larger resections increase the risk of destabilising the scapula and of straying toward the dorsal scapular neurovascular structures.
• The levator and rhomboid minor are reattached through drill holes in the fresh cancellous edge or with suture anchors. Omitting this step is the classic technical error and produces a painful, unstable, laterally translated scapula.
• Sling for 2 to 3 weeks with early passive motion, then progressive scapular strengthening; return to sport at 4 to 6 months.

Structures at risk with distances

Portal placement - the safe zone

Cadaveric work defining the scapulothoracic spaces established the rule that portals should be placed inferior to the spine of the scapula and three to four fingerbreadths medial to the vertebral (medial) border. Three reasons are given:

1. To avoid the neurovascular structures at the superomedial angle.
2. To avoid the dorsal scapular nerve and artery running close to the medial border.
3. To prevent the arthroscope being oriented perpendicular to the chest wall, which risks pleural penetration.

Practical set-up

• Prone position with the arm in the "chicken wing" position to open the space between the scapula and the chest wall.
• Two portals along the medial border, both inferior to the scapular spine, the second placed 4 to 5 cm distal to the first.
• Enter the infraserratus (serratus anterior) space - between serratus anterior and the chest wall - which contains the constant bursa. Do not attempt to work in the supraserratus space.
• Keep the instruments parallel to the chest wall at all times, low pump pressure, and avoid fluid extravasation.
• The superior angle is difficult to reach from these portals; an accessory portal placed superior to the scapula has been described specifically to allow easier resection of the superomedial angle, but it must be established under direct visualisation from a distal portal because of the neurovascular crowding.

Advantages and limits

Arthroscopic bursectomy avoids detaching the levator and rhomboid insertions and allows early rehabilitation. Its weakness is quantifying and completing a bony resection, so an open or hybrid approach remains reasonable where a substantial Luschka's tubercle must be removed.

Levator in the Eden-Lange transfer

• The levator scapulae is the upper limb of the transfer for irreparable trapezius palsy, substituting for the upper trapezius.
• It is detached from the superior angle with a wafer of bone, mobilised while preserving its deep-surface pedicle and nerve entry, and transferred laterally onto the scapular spine, fixed through a bone trough or tunnels with the arm at about 30 degrees of abduction.
• In the modified transfer it is carried further laterally, toward the lateral scapular spine or the acromion, because the classical position leaves the upward-rotation moment arm too short to correct scapular downward rotation. Cadaveric work supports the lateralised position as restoring kinematics closer to normal.
• Pre-requisite: an intact dorsal scapular nerve and cervical plexus supply. Confirm on EMG.
• Limit: excursion is only a few centimetres because of the deep pedicle; over-lateralisation without adequate mobilisation simply tears the transfer out.

Levator release in Sprengel deformity

In the Woodward and Green procedures the levator is released (and the omovertebral bar excised) as part of caudal repositioning of the scapula. Resecting the superomedial angle first reduces the amount of caudal translation required and therefore reduces traction on the brachial plexus - the most feared complication of these operations.