Sprengel Deformity 

Eulenberg first described what later became known as Sprengel deformity in 1863, and, 2 decades later, Willet and Walsham reported 2 cases with anatomic descriptions of this clinical entity.^{[1, 2]} Sprengel then described 4 cases of upward displacement of the scapula in 1891.^[3] Multiple case reports and surgical techniques followed in the literature for Sprengel deformity, also known as congenital elevation of the scapula. A photograph and radiograph of the deformity are below.

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In 1863, Eulenberg described Sprengel deformity as "hochgradige dislocation der scapula" (ie, a high-grade dislocation of the scapula).^[1] In 1883, Willet and Walsham were the first to describe the omovertebral bone, as well as the first to describe the excision of the bone, with good results.^[2] Sprengel described 4 cases of the condition in 1891.^[3] Kolliker, who also described 4 cases in 1891, gave the condition its eponym, Sprengel deformity.^[4]

Sprengel deformity is a complex anomaly that is associated with malposition and dysplasia of the scapula.^{[5, 6, 7, 8, 9]} This condition also involves regional muscle hypoplasia or atrophy, which causes disfigurement and limitation of shoulder movement.

Frequency

Sprengel deformity is the most common congenital malformation of the shoulder girdle.^[10] The male-to-female ratio is 3:1.

Genetics

The condition is sporadic. Rarely, it may run in families (autosomal dominant pattern of inheritance).^{[11, 12]}

Embryology

The scapula is a cervical appendage that normally differentiates opposite the fourth, fifth, and sixth cervical vertebrae at about 5 weeks' gestation.^[13] This structure normally descends to the thorax by the end of the third month of intrauterine life; any impediment to its descent results in a hypoplastic, elevated scapula, known as the Sprengel deformity.

Congenital elevation of the scapula is caused by an interruption in the normal caudad migration of the scapula. This produces both cosmetic and functional impairment and probably occurs between the 9th and 12th week of gestation. An arrest in the development of bone, cartilage, and muscle also occurs. The trapezius, rhomboid, or levator scapulae muscle may be absent, hypoplastic, or contain multiple fibrous adhesions. The serratus anterior muscle may be weak, leading to winging of the scapula. Other muscles, such as the pectoralis major, latissimus dorsi, or the sternocleidomastoid, may be hypoplastic and similarly involved.

Associated malformations are almost always present with a Sprengel deformity. These can include anomalies in the cervicothoracic vertebrae or the thoracic rib cage. The most common anomalies are absent or fused ribs, chest-wall asymmetry, Klippel-Feil syndrome, cervical ribs, congenital scoliosis, and cervical spina bifida. When scoliosis is present, the most common curves are in the cervicothoracic or upper thoracic region. A relationship between a Sprengel deformity and diastematomyelia has also been shown.

Another anomaly that is seen in approximately one third of patients with a Sprengel deformity is the omovertebral bone. This is a rhomboid- or trapezoid-shaped structure of cartilage or bone that usually lies in a strong fascial sheath, which extends from the superomedial border of the scapula to the spinous processes, lamina, or transverse processes of the cervical spine, most commonly the fourth to seventh cervical vertebrae. A well-developed joint can form between the scapula and the omovertebral bone; this bone can also be a solid osseous bridge. The omovertebral bone is best visualized on a lateral or oblique radiograph of the cervical spine.

Despite the work of Engel (Bleb theory), Oxnard, and Ogden et al, no satisfactory explanation exists regarding the pathogenesis of the Sprengel deformity.^{[7, 14, 15, 16]}

The gross pathology can be described as follows:

• Scapula: The scapula is dysplastic and is located higher than normal in the neck or upper thoracic region. This bone is smaller than normal in the vertical plane and appears larger horizontally. The inferior angle is rotated medially, causing the glenoid to face inferiorly. An inverse correlation exists between the superior displacement and rotation of the scapula; with a higher scapula, the rotation is decreased. Convexity of the upper (supraspinous) portion of the scapula is increased and curvature of the clavicular shaft is decreased, forming a narrower scapuloclavicular space, which may contribute to brachial plexus compression postoperatively.
• Omovertebral connection: An omovertebral connection, which may be fibrous, cartilaginous, or bony, may exist in about one third of cases.^{[5, 10]} This connection attaches the superomedial angle of the scapula to the spinous process, lamina, or transverse process of the cervical vertebrae and may be the primary cause of restricted shoulder motion in patients with a Sprengel deformity.^[17] The omovertebral connection is usually unilateral, is always associated with a fixed, elevated scapula, and has a major role in determining the shape and the malpositioning of the scapula.^{[18, 19]} According to Willet and Walsham, the omovertebral bar is homologous to the suprascapular bone in lower vertebrates.^[2]
• Periscapular muscles: The spinoscapular muscles may be fibrotic and contracted, with the trapezius muscle the most commonly affected.

The hallmarks of the Sprengel deformity are shoulder asymmetry and restriction of shoulder abduction. Clinically, the affected scapula usually is elevated 2-10 cm and is adducted, and its inferior pole is rotated medially. Because of this rotation, the glenoid faces inferiorly. A prominence in the suprascapular region is characteristic because of the upwardly rotated superomedial angle of the scapula, which causes the ipsilateral side of the neck to appear fuller and its normal contour to be lost. The scapula is hypoplastic, and the length of the vertebral border is decreased. Occasionally, some anterior bending of the supraspinous portion is present.

Passive movement of the glenohumeral joint, including abduction and external and internal rotation, may be normal. However, scapulothoracic movements may be severely limited. In 40% of patients with a Sprengel deformity, combined abduction is limited to less than 100º. The omovertebral bone may also limit abduction by affecting scapular mobility, and can also limit neck movement if this bone is attached high in the cervical spine. Other causes of limited abduction include abnormal and weakened scapular muscles.

The left side is more commonly affected than the right side. The condition may sometimes be bilateral, in which case, although it is cosmetically much more acceptable, functionally, it is more disabling.

Problems that may be associated with this condition include syndromes such as the following:

• Klippel-Feil syndrome^{[20, 21, 22, 23]}
• Greig syndrome^[24]
• Poland syndrome^[25]
• VATER association (ie, vertebral defects, imperforate anus, tracheoesophageal fistula, and radial and renal dysplasia)^[26]
• Velocardiofacial syndrome^[27]
• Floating-harbor syndrome^[28]
• Goldenhar syndrome^[29]
• X-linked dominant hydrocephalus, skeletal anomalies, and mental disturbance syndrome^[12]

These syndromes are extremely rare, with the possible exception of the Klippel-Feil syndrome.

Based on the severity of the condition, a Sprengel deformity can be classified as follows (Cavendish grades)^[8] :

• Grade 1: The deformity is very mild. The shoulders are almost level, and the deformity cannot be noticed with the clothes on.
• Grade 2: The deformity is mild. The shoulders are almost level, but the superomedial portion of the high scapula is visible as a lump.
• Grade 3: The deformity is moderate. It is visible, and the affected shoulder is elevated 2-5 cm higher than the opposite shoulder.
• Grade 4: The deformity is severe. The scapula is very high, with the superomedial angle at the occiput, with neck webbing and brevicollis.

This classification, however, is difficult to apply in bilateral cases, as in the photo below.

Indications for surgical intervention of a Sprengel deformity include significant cosmetic concerns and significant restriction of shoulder abduction in children younger than age 6 years.

Some vital structures are at risk during the extensive dissection that is required as part of the relocation procedure. These structures include the following^[30] :

• The dorsal scapular nerve: This nerve courses close to the superomedial border of the scapula in the plane between the rhomboid and erector spinae muscles. The dorsal scapular nerve remains anterior to the serratus anterior and the subscapular muscles. There exists a risk of injuring the nerve during dissection of the periscapular muscles at the superomedial angle of the scapula, and when the trapezius and rhomboid muscles are reflected off as a single unit from the spine in the Woodward procedure (see Treatment, Intraoperative details, below). Therefore, staying subperiosteal during the process of freeing the periscapular muscles is essential, especially at the superomedial angle of the scapula.
• The spinal accessory nerve: This nerve is located between the trapezius and rhomboid muscles and is, therefore, at risk theoretically; however, because the spinal accessory nerve is sandwiched between the 2 muscles, it is rarely ever injured when these muscles operate as a unit.
• The suprascapular nerve: This nerve runs in the suprascapular notch of the scapula and may be injured if the dissection is carried too far laterally when the superior portion of the scapula is resected. By staying at least 1 cm medial to the notch, injury to the nerve during the procedure can be avoided.

The presence of a mild deformity with minimal restriction of movement is a contraindication to surgery. Although treatment of the Sprengel deformity is essentially surgical, some factors exist that could compromise the results of surgery and, thus, may be considered to be contraindications. These factors include the presence of associated syndromes that affect the final functional outcome.