Developmental anomalies of the scapula—the “omo”st forgotten bone

Abstract

Congenital malformations of the scapula, ranging from complete absence, to abnormal shape and position (Sprengel anomaly) are encountered, not infrequently, in genetic practice. Despite this, little is known of the embryologic origin of the scapula and the relationship of the embryology to the observed birth defects. Standard embryology texts, when discussing the subject at all, generally consider the scapula as part of the upper limb. The pattern of associated birth defects suggests that this is at least an oversimplification and may be inaccurate. Sprengel anomaly is the most frequently encountered malformation of the scapula. It can be seen in isolation, but is often seen in association with other defects that include; scoliosis, hemivertebrae, segmentation abnormalities of vertebrae and ribs (including Klippel-Feil sequence), spina bifida, clavicular abnormalities, renal abnormalities and hypoplasia of the muscles of the neck and shoulder. The ipsilateral limb is usually normal. An unappreciated association between Sprengel anomaly and diastematomyelia of the lumbar spine also raises questions about the embryologic origin of the scapula. 25-50% of Sprengel anomaly patients have an associated omovertebral band or bone that arises from the posterior process of a vertebral body and attaches to the superior angle/medial portion of the scapula. This is felt to be of scapular origin, but the report of at least one patient with an omovertebral bone, not associated with a Sprengel anomaly questions this assumption. Scapuloiliac dysostosis (Kosenow syndrome), a rare skeletal dysplasia, is associated with marked hypoplasia of the scapulae, clavicles and pelvis. Associated anomalies include eye anomalies, rib anomalies and spina bifida. The limbs are normal. Knockout of the Emx2 gene in mice yields a similar skeletal phenotype. Mutations in EMX2 in humans are associated with schizencephaly, not skeletal anomalies. Data on gene expression in the scapula will be reviewed. Based on this information, the author proposes that the scapula arises from 2 or more distinct embryologic anlage under different genetic control than the upper limb.

Duplication of the scapula: case report with 27-year follow-up

“…Complete duplication of the scapula, on the other hand, is exceedingly rare. 6,7,9 Few cases of scapular duplication have been reported in the current literature. 2,4,6,7 Of those cases reported, most were partial duplications and were associated with other skeletal deformities, most often of the ipsilateral upper limb and spine.…”

“…Those cases of complete duplication did not show articulation of the anomalous scapula with the vertebral column. 9 The Sprengel deformity, in contrast, is by far the most common congenital scapular deformity. 9 It is a congenitally high scapula, in which the shoulder girdle fails to descend during embryological development.…”

“…9 It is a congenitally high scapula, in which the shoulder girdle fails to descend during embryological development. 7,9,10 It may be seen in isolation, but more commonly occurs with spinal deformities such as scoliosis, hemivertebrae, segmentation anomalies of vertebrae and ribs, spina bifida, clavicular anomalies, renal abnormalities, and hypoplasia of muscles of the neck and shoulder. 9 The ipsilateral limb, however, usually is not affected.…”

Differential regulation of avian pelvic girdle development by the limb field ectoderm

“…Vitale and Skaggs 2001;Weinstein et al 2004), or scapuloiliac dysostosis (reviewed in e.g. Elliot et al 2000;Hauser et al 1998;Williams 2003), morphogenesis and molecular regulation of pelvic girdle development is largely unknown.…”

Fanconi Anemia Patient With Bilaterally Hypoplastic Scapula and Unilateral Winging Associated With Scoliosis and Rib Abnormality

“…2,6 In Fanconi anemia patients, numerous types of skeletal abnormalities have been described with radial-ray abnormalities being the most common; however scapula, vertebra, and rib abnormalities are quite uncommonly reported. The most common scapular defect by far is the Sprengel deformity, 7 and have also been previously reported in Fanconi anemia patients. 4,8 Herein, to our knowledge, we report the association of Fanconi anemia with a previously unreported thoracic skeletal abnormality.…”