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Table of Contents    
CASE REPORT
Year : 2016  |  Volume : 64  |  Issue : 5  |  Page : 984-987

“Os” omovertebrale variants prove it to be a misnomer


Department of Neurosurgery, National Institute of Mental Health and Neurosciences, Bengaluru, Karnataka, India

Date of Web Publication12-Sep-2016

Correspondence Address:
Bhagavatula I Devi
Department of Neurosurgery, National Institute of Mental Health and Neurosciences, Bengaluru - 560 029, Karnataka
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0028-3886.190264

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 » Abstract 


There are only a few case reports comprising exclusively of os omovertebrale. Here, we discuss various types, varied clinical presentations, associated abnormalities, and management strategies of this abnormality. We retrospectively analyzed three patients with os omovertebrale and their clinical presentation, and also reviewed the limited available literature. Patients were evaluated clinically and radiologically to diagnose this abnormality as well as the associated abnormalities. Two patients were operated for neurological deficits attributed to this deformity. It is quite common to miss this abnormality when it is of osseocartilaginous or fibrous type, especially when it is asymptomatic and not associated with Sprengel's scapula. By analyzing our patients and other reported cases, we have proposed a classification system. In addition, we discuss varied clinical presentations and their practical application. Os omovertebrale is a rare abnormality. It should be kept in mind and managed when encountered in clinical practice. The classification and clinicoradiological correlations described here can be useful to individualize management issues.


Keywords: Klippel–Feil syndrome; os omovertebrale; Sprengel's deformity


How to cite this article:
Solanki C, Bhat DI, Devi BI. “Os” omovertebrale variants prove it to be a misnomer. Neurol India 2016;64:984-7

How to cite this URL:
Solanki C, Bhat DI, Devi BI. “Os” omovertebrale variants prove it to be a misnomer. Neurol India [serial online] 2016 [cited 2019 Sep 18];64:984-7. Available from: http://www.neurologyindia.com/text.asp?2016/64/5/984/190264





 » Introduction Top


Os omovertebrale or omovertebral bone is a relatively uncommon congenital abnormality comprising of abnormal bone or fibrous band associated with rare anomalies of the shoulder and spine. The first report of the existence of such an abnormal bone was made in 1880 by Willett and Walsham, which they observed while conducting an autopsy.[1] Later on, they reported an 8-year-old child in 1883, who was operated for restricted shoulder movements. Since then, there are only single case reports exclusively addressing this abnormality. The clinical implications of this abnormality have been reported only as a part of Sprengel's scapula management, even though this anomaly may be present even in the absence of Sprengel's scapula.

Os omovertebrale is an osseo-fibrocartilagenous connection between the lower cervical or upper dorsal spine and medial border of scapula. It is most commonly found in relation to the C5 to C7 vertebrae or rarely to T1.[1],[2],[3],[4],[5] A possible explanation for its presence may be that the scapula develops at the C4 to C6 vertebral levels during the fifth week of fetal life, which later descends during development. In most of the cases, the bone is attached laterally to the middle third of the medial border of scapula.

Os omovertebrale is seen in one-third of children with Sprengel's anomaly.[6] The classically described bony bridge may be a rare finding, but the cartilaginous or fibrous variants may be much more common. However, these types might be difficult to suspect and diagnose clinically as well as radiologically.[7] They are frequently found during surgery for Sprengel's scapula.

Os omovertebrale may also be associated with Klippel–Feil anomalies, congenital scoliosis, hemivertebrae, spina bifida, or rib cage abnormalities.[4] Majority of the cases described are in children. Quite uncommonly, adults can present with omovertebral bone with features of compressive myelopathy.[8]

As far as the origin of this abnormality is concerned, there is no definite consensus. Various theories of its origin from either the vertebra, or the scapula, or as an independent entity have been proposed. One theory suggests the origin of the process of bone in connection with the vertebra, which later becomes ankylosed to the scapula. The bone may be homologous to one of the laterally projecting processes, the so-called hyperapophyses, developed near the extremity of the spinous processes of the lower cervical vertebrae. Another theory suggests that the origin of the bone is independent from that of the spine and scapula and occurs due to the ossification of the connective tissue in the intermuscular plane. The most accepted theory presumes the bone to be originally a scapular element which becomes secondarily fused to the spine.[1],[2]


 » Case Description Top


Out of three patients, two were adults, which is extremely rare. They presented with myelopathy, and one of the patient had an occult Sprengel's scapula. One patient had this connection in the upper dorsal spine, which is also contrary to its common location in the lower cervical region. The clinical details of these patients are given in [Table 1].
Table 1: Clinical details of patients with omovertebral anomaly

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 » Discussion Top


Considering the varied morphological presentation, this historically described bony abnormality stands out as a misnomer. Therefore, we propose a morphological classification system [Table 2].
Table 2: Proposed classification system for omovertabral anomaly

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Type I omovertebral band has fibrous structure [Figure 1]. It is the most common type and is usually asymptomatic. It is most likely to be missed clinically as well as radiologically. When it is symptomatic, restriction of the shoulder is present. It just requires division of the band for release of the scapula.
Figure 1: Fibrous type (Type I) of omovertebral band, a fibrous band connecting spine to medial border of scapula

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Type II is an osseofibrous connection, which is the second most common type [Figure 2]. Usually asymptomatic, it may present in later life as myelopathy (especially when not associated with other abnormalities), due to ossification of the cartilaginous element. It requires excision of the cartilaginous part and disconnection of the fibrous element.
Figure 2: Osseofibrous (Type II) omovertebral anomaly, medial bony ridge is connected to scapula by a fibrous band

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Type III osseocartilaginous form [Figure 3] is usually associated with varying degrees of restricted shoulder movements. The osseocartilaginous end forms a “joint like” connection to the scapular border. Surgical excision is indicated in symptomatic patients; or, as a part of surgery for Sprengel's scapula (for addressing the cosmetic deformity), if the patient is asymptomatic.
Figure 3: Osseocartilagenous (Type III) omovertebral bone; there is a “joint” like connection of the omovertebral bone with the scapula

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Type IV “true” os omovertebrale [Figure 4] is almost always associated with restricted shoulder movements. Therefore, complete excision is necessary because it is usually associated with aberrant muscular attachments and both surfaces are covered with periosteum. Therefore, partial excision at the compressing spinal end may not be sufficient as these bony abnormalities may recur.
Figure 4: “True” Os Omovertebrale (Type IV); there is direct rigid bony connection of spine with scapula

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Figure 5: X-ray (left) showing Os omovertebrale (arrow) on the left side connected to the scapula with a cartilaginous joint like connection, and the MRI (right) showing significant compression

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Figure 6: The CT scan of cervico-thoracic spine, axial (left) and coronal (right) images showing the omovertebral bone causing canal compromise

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Figure 7: X-ray (left) showing the omovertebral bone (arrow) and CT scan (right) showing the spinal attachment of the omovertebral bone to the C5-C6 laminae

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Thus, the management of os omovertebrale can be individualized based on the type and clinical presentation, especially when it is not a part of Sprengel's scapula.


 » Conclusion Top


True os omvertebrale is an abnormal bone connecting the medial border of the scapula to the lower cervical or upper thoracic vertebra. Other fibrous, osseofibrous, and osseocartilaginous forms are also documented thus making the term “os” omovertebrale a misnomer. It may be asymptomatic or may present with cosmetic deformity, restricted joint movements, neck pain, or compressive myelopathy. It commonly presents in childhood as a part of associated deformities such as Sprengel's scapula. Uncommonly, it presents in later life as myelopathy. All asymptomatic cases can be managed expectantly unless cosmetic deformity due to Sprengel's scapula is present.[4],[5] The above-described four-tier classification system identifies morphological characteristics and helps in decision-making, especially in the absence of associated congenital abnormalities. The surgical outcome is significantly favorable, especially in those presenting with compressive myelopathy.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest

 
 » References Top

1.
Willett A, Walsham WJ. An account of the dissection of the parts removed after death from the body of a woman the subject of congenital malformation of the spinal column, bony thorax, and left scapular arch; with remarks on the probable nature of the defects in development producing the deformities. Medico-chirurgical Transactions 1880; 63:257-302  Back to cited text no. 1
    
2.
Willett A, Walsham WJ. A second case of malformation of the left shoulder-girdle; removal of the abnormal portion of bone; with remarks on the probable nature of the deformity. Medico-Chirurgical Transactions 1883; 66:145-58  Back to cited text no. 2
    
3.
Mol W, Detmar SJ. The combination of Sprengel's deformity with Klippel-Feil disease and the presence of an os omovertebrale. Archivum Chirurgicum Neerlandicum 1966; 18:167-74  Back to cited text no. 3
    
4.
Schultz GD, Phillips RB. Omovertebral bone. J Manipulative Physio Th 1989; 12:50-3  Back to cited text no. 4
    
5.
Williams MS. Developmental anomalies of the scapula-the “omo”st forgotten bone. Am J Med Genet Part A 2003;120A: 583-587. doi: 10.1002/ajmg.a.20091.  Back to cited text no. 5
[PUBMED]    
6.
Azouz EM. CT demonstration of omovertebral bone. Pediatric radiology 2007;37:404.  Back to cited text no. 6
[PUBMED]    
7.
Wada A, Nakamura T, Fujii T, Takamura K, Yanagida H, Yamaguchi T, et al. Sprengel deformity: Morphometric assessment and surgical treatment by the modified green procedure. J Ped Ortho 2014; 34:55-62.  Back to cited text no. 7
    
8.
Fullbier L, Tanner P, Henkes H, Hopf NJ. Omovertebral bone associated with Sprengel deformity and Klippel-Feil syndrome leading to cervical myelopathy. J Neurosurg Spine 2010; 13:224-8.  Back to cited text no. 8
    


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]
 
 
    Tables

  [Table 1], [Table 2]



 

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