Levator Scapulae Anatomy

Origin. Four separate tendinous slips from the posterior tubercles of the transverse processes of C1 to C4. The C1 (atlas) and C2 (axis) slips arise from the transverse processes themselves, the C3 and C4 slips from the posterior tubercles, and the four 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 superomedial angle, where the tendon is thickest, and 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. The spiral is a favourite anatomical question with a practical consequence: the muscle cannot be split longitudinally along an internervous plane, because the fibres from different roots are interleaved.

The bone at the insertion. The superomedial angle is thin, and its ventral surface may carry a hooked or curled, anteriorly projecting prominence known as Luschka's tubercle. It is a recognised cause of mechanical scapulothoracic snapping and is the target of superomedial angle resection.

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Dual supply. Direct branches from the ventral rami of C3 and C4 (cervical plexus) enter the muscle on its deep surface in the posterior triangle; they are present in essentially everyone and provide the dominant supply. The dorsal scapular nerve (C5) also supplies it, entering the deep surface as the nerve passes from the middle scalene toward the rhomboids, so the overall root value is commonly given as C3, C4 and C5. 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.

Why it is examined. The C3 and C4 supply is separate and more proximal, so 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.

Spinal accessory nerve palsy. The same separate supply explains why levator function is variably spared when the trapezius is denervated: the levator 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.

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Named vessels. Four sources supply the muscle:

• 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

The pedicle. The dorsal scapular vessels enter the deep surface of the muscle close to the superomedial angle. That entry point sits directly in the field of a superomedial angle resection and of a superomedial arthroscopic portal, which is the reason both are hazardous.

In the neck. Superficial (posterior) to the muscle lie 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, immediately deep to the investing fascia and alongside the accessory nerve; the sternocleidomastoid overlies it superiorly and the trapezius inferiorly. Deep (anterior) to it lie 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. With splenius capitis, the scalenes and semispinalis capitis it forms part of the floor of the posterior triangle.

At the scapula. Superficial to it is the trapezius. Deep to it are 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. Rhomboid minor lies immediately inferior, often blending with it.

The nerve on its surface. The spinal accessory nerve lying on the levator in the posterior triangle is the reason a node biopsy over the muscle is dangerous, and the reason a superomedial arthroscopic portal is discouraged.

The condition. Snapping (or crepitant) scapula syndrome is painful, audible or palpable crepitus arising from the scapulothoracic articulation, at the superomedial angle first and the inferior angle second.

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

• The serratus anterior (infraserratus) space, 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 (supraserratus) space, 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 they are the ones that hurt.

Causes of the snap. Six categories:

The pathway. Three steps, in order:

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: bursectomy alone, or bursectomy with superomedial angle resection where imaging shows a bony prominence, performed open or arthroscopically

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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, into the medial scapula and occasionally to the shoulder, with a palpable, exquisitely tender taut band at the insertion. It is aggravated by sustained sitting with an unsupported arm, carrying a bag, driving, and by holding the head turned away from the painful side; contralateral cervical side-bending and rotation are restricted, with the pain reproduced when the shoulder is depressed at end range. It hurts at rest and with neck position, whereas 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. A dorsal scapular nerve lesion at the middle scalene may denervate the levator; combined levator and rhomboid denervation on EMG is the pattern. C3-C5 root pathology denervates it reliably, so 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; the Green procedure likewise releases the levator and excises the bar as part of caudal repositioning of the scapula. The brachial plexus is at genuine risk during caudal translation, the most feared complication of these operations, which is why the superomedial angle is resected first: it reduces the translation required and so the traction on the plexus.

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, in the patient the pathway selects: pain abolished by a diagnostic bursal block, structured rehabilitation failed, and a bony prominence or symptomatic bursa demonstrated on CT or MRI.

The operation. Prone or lateral position, with the 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. Then, in order:

1. Incision along the medial border from the superior angle distally for 6 to 8 cm
2. The trapezius is split or elevated, and levator scapulae and rhomboid minor are detached from the superomedial angle, leaving tendinous cuffs on the muscle for repair. The detachment is unavoidable: the levator insertion sits on the bone being removed
3. The infraserratus (scapulothoracic) bursa is excised
4. The superomedial angle is resected with an osteotome or saw as a triangular wedge, the plane developed from below under direct visualisation. Resection is deliberately limited, a wedge of the order of 2 cm along each of the superior and medial borders; larger resections increase the risk of destabilising the scapula and of straying toward the dorsal scapular neurovascular structures
5. 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
6. Sling for 2 to 3 weeks with early passive motion, then progressive scapular strengthening, with return to sport at 4 to 6 months

Structures at risk. Each has a position relative to the angle and a rule for avoiding it:

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, for three reasons:

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

Set-up. Prone, 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, with 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.

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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 by dissecting on its superficial (posterior) surface and freeing the insertion from lateral to medial so that the deep-surface pedicle and nerve entry stay intact, and transferred laterally onto the scapular spine, fixed through a bone trough or tunnels with the arm at about 30 degrees of abduction.

The modified transfer. In the classical position the transferred insertion sits close to the scapular rotation axis, so its upward-rotation moment arm is poor and too short to correct scapular downward rotation. Carrying the levator further laterally, toward the lateral scapular spine or the acromion, lengthens that moment arm, which is the entire rationale for the modification, and cadaveric work supports the lateralised position as restoring kinematics closer to normal.

Prerequisite and limit. The transfer needs an intact dorsal scapular nerve and cervical plexus supply, confirmed on EMG. Excursion is only a few centimetres because of the deep pedicle, and over-lateralisation without adequate mobilisation simply tears the transfer out.

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