Os omovetebrale is an osseofibrocatilagenous connection between the lower cervical or upper dorsal spine and the medial border of the scapula. Most commonly found at the level of C4-C7 and rarely at T1. Most cases described are children; adults can also present with omovertebral bone and features of compressive myelopathy. The most accepted theory in connection with the origin of bone is that the bone is the original scapular element which becomes secondarily fused to the spine [1]. The four-tier classification system [2] identifies the morphological characteristics and helps decision-making.
Proposed classification system for the vertebral anomaly-
Type I-Fibrous
Type II-Osseous-Fibrous
Type III-Osseo-Cartilagenous
Type IV-Osseous (True)
Sprengel deformity is a rare congenital deformity of children, which is associated with a hypoplastic, medially rotated, triangular-shaped scapula with restricted abduction and flexion of the involved shoulder. The scapula is elevated with scapular winging. Incidence is more in female children with M: F=1:3.This condition may occur bilaterally in 10-30% of cases. Interruption of embryonic subclavian blood supply at the level of subclavian, internal thoracic or supra-scapular artery and failure of caudal migration of shoulder to its normal position is considered the aetiology [3,4]. In addition, this deformity is associated with muscle atrophy of the pectoral girdle resulting in disfigurement [5].
One-third of cases of Sprengel's shoulder is associated with Klippel Feil deformity. In addition, congenital scoliosis is often seen. Other uncommon associations are diastematomyelia and renal disease[1]. Omovertebral connection between the cervical spine (C4-C7) and medial angle of the scapula is present in 30-50% of cases. This connection may be fibrous or osseous [6]. Occasionally it may be bilateral.
Diagnosis is often clinical. Plain Radiographs are used as a screening method to evaluate the bony bar; however, fibrous connections require assessment with CT/MRI.CT 3D reconstructions are especially helpful in preoperative planning.MRI is indicated in compressive cervical myelopathy or a review of ipsilateral brachial plexus.
Functional deformities and cosmetic concerns indicate operative treatment (abduction< 110-120 degrees). Surgery is best performed in 3-8 yrs because of the risk of nerve entrapment after age 8. The surgical outcome is significantly favourable, especially in cases with compressive myelopathy. In the absence of shoulder dysfunction, observation is the treatment of choice[1]
Teaching points
Imaging plays a distinct role in management by identifying the morphology of omovertebral bone based on different types, especially when it is not a part of Sprengel scapula.
