A rigid spine is a condition that is characterised by the ossification and/or fusion of spinal segments thus leading to a change in biomechanics. The shock absorption capabilities of normal intervertebral discs, as well as the elasticity of ligaments, is eliminated thus making the rigid spine more to fracture. A rigid spine can develop in the following clinical conditions ¹:

• ankylosing spondylitis

• diffuse idiopathic skeletal hyperostosis

• degenerative spondylosis

• surgically fused spine

Clinical importance

A rigid spine can alter the management in the setting of spinal fractures and is recognised as a modifier in the AO Spine classification system ^1,2. Delayed diagnosis of spinal fracture is common, which may be in part due to low or no impact mechanism reducing clinical suspicion, distant fracture from the region of rigidity, osteoporotic bone, and difficulty visualising through obscuring degenerative change, overlapping anatomy, or/and metalware ¹.

These patients are at risk of patients are at risk of missed diagnosis, with risk of profound neurologic deficit. The non-contiguous injury rate is high, so the entire spine should be imaged.

• ankylosing spondylitis

  • prone to transdiscal fractures often as a result of hyperextension injuries

  • often located in the cervical spine

• diffuse idiopathic skeletal hyperostosis (DISH)

  • intervertebral bridging with fusion, along with poor bone quality, often leads to fragility of the spine

  • prone to hyperextension and translational injury

  • often located at the thoracolumbar junction or lower cervical spine

  • cervical DISH can make intubation more difficult, and may cause dysphagia ^1,3

• degenerative spondylosis

  • more often transvertebral fractures

  • often located where spondylosis is present e.g. in the cervical and lumbar spine

• surgically fused spine

  • increased fracture risk at the junctional zone (up to 3 vertebrae) above and below the fused segments

  • prone to transverse fractures and compression fractures