Overview

Noninflammatory flowing ossification along at least four contiguous vertebral bodies
Disc height preserved, no sacroiliac or facet ankylosis (Resnick criteria)
Common in older men, linked with diabetes and obesity
Large anterior cervical osteophytes can cause dysphagia
Ankylosed spine behaves like a long bone, so minor trauma causes unstable fractures
New spinal pain after a fall needs CT, then MRI if CT is normal

Western Health Orthopaedic Registrar presentation – Arthropathy of the Spine by Dr Devinder Garewal

Pathology

Non-inflammatory enthesopathy with ossification of ligaments and entheses
Bulky flowing ossification of the anterior longitudinal ligament, right-sided in the thoracic spine from aortic pulsation
Discs, facets and sacroiliac joints preserved, bone density normal or increased
Linked with heterotopic ossification after hip arthroplasty

Resnick criteria

	Criterion
1	Flowing ossification along the anterolateral aspect of at least four contiguous vertebral bodies
2	Relative preservation of disc height
3	No facet ankylosis and no sacroiliac erosion, sclerosis or fusion

Ankylosing spondylitis affects adults under 40, is HLA-B27 positive and causes sacroiliitis
AS shows thin marginal syndesmophytes, facet ankylosis and osteoporotic bone
Spondylosis deformans has disc narrowing and horizontal osteophytes that do not flow continuously

Dysphagia, hoarseness or difficult intubation from anterior cervical osteophytes

Ankylosed spine acts as a lever, so low-energy falls cause unstable three-column fractures
Assume a fracture with any new spinal pain after trauma
CT of the whole spine, since radiographs miss many injuries and non-contiguous fractures occur
MRI for ligamentous injury, epidural haematoma and cord compression
Immobilise in the pre-injury posture and never force the spine into neutral
Most need long-segment posterior instrumentation, often percutaneous

Reviewed by Professor Phong Tran, Head of Orthopaedic Surgery, Western Health. Last updated 10 October 2026.