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International Journal of Anatomical Sciences 2010, 1: 7-10

Research Paper

Diffuse Idiopathic Skeletal Hyperostosis

Ravichandran D, Muthukumaravel N,b Deepti S, Melani R, Subramaniam PM.

Department of Anatomy, VMKV Medical College, Salem, India; bDepartment of Anatomy, Annapoorna Medical College, Salem, India; cDepartment of Anatomy, SRMC&RI, Chennai, India; dDepartment of Pathology, VMKV Medical College, Salem, India

Key Words: thoracic vertebrae, anterior longitudinal ligament, supra-spinous ligament

 Abstract: A dry bone specimen comprising six thoracic vertebrae held together by ossified anterior longitudinal and supra-spinous ligaments is reported. The specimen was subjected to plain radiography. The antero-posterior and lateral views confirmed the ossification of the above ligaments. Moreover, the ossified anterior ligament was found to be separated from the body of the vertebrae by a space and a radio-dense line paralleling the longitudinal axis of the vertebrae. The inter-vertebral disc space and the zygoapophyseal joint space were free. A piece of the ossified mass, subjected to histo-pathological examination also confirmed the ossified ligaments. Review of literature  suggests  that  this  is  a  case  of  diffuse  idiopathic  skeletal  hyperostosis (DISH).

 The anterior longitudinal ligament is extending  from  atlas  to  sacrum  is  a  flat strong   band   found   along   the   anterior surfaces of the vertebral bodies which becomes broader when traced caudally. It is thicker and narrower in the thoracic region than  in  the  cervical  and  lumbar  regions. The posterior longitudinal ligament on the posterior surfaces of the vertebral bodies inside the vertebral canal gradually narrows when traced downwards.   These ligaments are adherent to the inter-vertebral discs, hyaline  cartilage  lining  the  articular surfaces,   margins   of   adjacent   vertebral bodies and the laminae.   At various levels, ligamentous fibres blend with the subjacent periosteum, perichondrium and periphery of the annulus fibrosus (Williams et al., 1995).

 Correspondance to: Ravichandran D, Department of Anatomy, VMKV Medical College, Salem, India. Email: [email protected]

Supraspinous   ligament   is   a   strongfibrous band connecting the tips of spinous process from C7 to the sacrum.   Its most superficial fibers span over three or four spines, the deeper fibers bridge over two or three spines, while the deepest connect adjacent spines  becoming continuous with interspinous   ligaments   (Williams   et   al.,1995). Heylings (1978) considers supra- spinous ligament to cease at the fifth lumbar spine.

The anterior longitudinal, posterior longitudinal and supraspinous ligaments (para-spinal ligaments) undergo degene- ration secondary to attrition, and they often ossify. This condition is broadly termed as spinal enthesopathy.  Ossification involving the anterior longitudinal ligament is referred to as Forestier’s disease. Further, a diffuse variant exhibiting additional extra-axial features is termed as diffuse idiopathic skeletal hyperostosis (DISH)

Material and Methods

Morphological examination was undertaken on a dry bone specimen comprising   six   thoracic   vertebrae   held  together  by  ossified  anterior  longitudinal and supraspinous ligaments, identified in the bone bank of the Dept. of Anatomy, VMKV Medical College, Salem. The specimen was subjected to plain radiographic study. Histo- pathological  examination  also  was  carried out on a piece of the ossified tissue.

 Observations

 Gross examination revealed a tortuous mass anteriorly along the sides (prominent on the right side) of the vertebral bodies holding them together. A clear space was   noted   between   the   mass   and   the vertebral  bodies.    The  spinous  processes were also found to be held together by a similar tortuous mass (Fig. 1). The gross appearance  of  the  mass  was  like  that  of   candle wax dripping down the spines. The intervertebral disc space was found to be maintained and the zygoapophyseal joints were found to be free (Fig. 2).   The intervertebral foraminae and vertebral canal appeared normal.    Other parts of the vertebrae including the pedicles, laminae, transverse  processes  and  the  costal  facets also appeared normal.    The anteroposterior and lateral views of radiographs showed the mass to be of bony nature. It was found to be separated from the body of the vertebrae indicated by a space and radiodense line paralleling the longitudinal axis of the vertebrae (Fig. 3). The inter-vertebral disc space and zygapophyseal joint space were free. Histo-pathological examination confirmed the tissue as ossified (Fig. 4).

 The differential diagnosis of paraspinal ligament ossification includes Forestier’s disease, Ankylosing spondylitis and Rheumatoid spondylitis (Khozaim Nakhoda     and     Grays,     2009).     Other  associated problems like fluorosis, ossified posterior longitudinal ligament (OPLL), hypophosphatemia and hypoparathyroidism need to be considered. The present observation of ossification along the anterolateral aspect of the vertebral body involving more than four thoracic vertebrae,

supraspinous ligament  ossification,    main- tained disc space, free facetal joints, separation  of  the  ossified  mass  from  the body and candle wax dripping appearance favour the diagnosis   of Forestier’s disease otherwise known diffuse idiopathic skeletal hyperostosis (DISH).

 DISH is an idiopathic rheumato- logical abnormality in which exuberant ossification occurs along the ligaments (McCafferty et al., 1996). The incidence of this disease is about 6 – 12 % (Khozaim Nakhoda  and  Grays,  2009)  and  shows  a male   predominance   (Westerveld   et   al.,2008).  It is noted predominantly in elderly individuals usually after 50 years. But some had observed paediatric cases with ossification of anterior longitudinal ligament of cervical spine (Coakley et al., 1995). Although DISH commonly affects the anterior  longitudinal  ligament,  ossification of posterior longitudinal ligament of the cervical  spine  is  also   noted  in   2%  of Japanese and 0.16% of Whites by Ono et al., (1982). However the pathophysiology of this phenomenon remains unknown.

 DISH is found in 1-3 % of baboons, monkeys, gorillas, bears, camels, horses (Bjorkergren et al., 1985; Ferigolo, 1988; Rothschild and Woods, 1988). It is interesting to note that paleontologic records  showed DISH in dinosaurs and early mammals (Rothschild, 1987; Rothschild and Berman, 1991). DISH is usually asymptomatic.  Reduction in range of spinal movement may occur if vertebral fusion is extensive (Olivieri et al., 2007).

 References

Bjorkergren AG, Sartoris DJ, Shermis S (1987) Patterns of aravertebral ossification in the prehistric saber toothed cat. Am J Roentgenol,148: 779-782.

Coakley FV, Vive J,  Finlay DB, Shannon RS (1995) Childhood ossification of the anterior longi- tudinal ligament of the cervical spine. Clin Radiol, 50: 115 – 116.

Ferigolo J, Estudos (1988) Multidisciplinares. In: Goncalves de Araujo AJ, Ferreira LF, eds. Non human Vertebrate Paleopathology. Brazil: Panorama. 213 – 234.

Heylings DJA (1978) Supraspinous and interspinous ligaments of the human lumbar spine. J Anat,125: 127 – 131.

Khozaim N, Grays (2009) Diffuse Idiopathic Skeletal

Hyperostosis, e- Medicine Radiology / article /388973 – overview.

McCafferty RR, Harrison MJ, Tamas LB, Larkins MV (1991)    Ossification    of    the    anterior longitudinal ligament and Forestier’s disease: an analysis of seven cases. J Neurosurg, 85: 524 –525.

 Olivieri , Dvingelo S, Cutro MS, Padula A, Peruz G, Montaruli M (2007) Diffuse idiopathic skeletal hyperostosis   may   give   the   typical   postural abnormalities      of      advanced      ankylosing spondylitis. Rheumatology, 46: 1709 – 1711.

Ravichandran et al., Diffuse idiopathic skeletal hyperostosis  Ono M, Rusell WJ, Kudo S (1982) Ossification of  the thoracic posterior longitudinal ligament in a  fixed population.  Radiological and neurological manifestations. Radiology, 143: 469-474.