SUMMARY DISH, also known as Forestier disease, is a common disorder of unknown etiology characterized by enthesopathy of the spine and extremities, that usually presents with back pain and spinal stiffness. Diagnosis can be confirmed with radiographs of the cervical and thoracic spine. A CT scan should be performed whenever there is concern for a fracture following low energy trauma. Treatment is usually activity modification, physical therapy, and bisphosphonate therapy. Associated spine fractures are treated with long spinal fusion. Epidemiology Demographics overall incidence 6-12% uncommon before 50 years old prevelence > 50 y.o. (25% males; 15% females) > 80 y.o. (28% males; 26% females) less common in Black, Native-American and Asian populations Location occurs anywhere in spine most common in the thoracic spine (right side) > cervical > lumbar postulated to be due to the protective effect of the pulsatile aorta on the left of the thoracic spine symmetrical in the cervical and lumbar spine (syndesmophytes both on left and right of the spine) Risk factors gout hyperlipidemia diabetes ETIOLOGY Associated conditions lumbar spine lumbar spinal stenosis cervical spine dysphagia and stridor hoarseness sleep apnoea difficulty with intubation cervical myelopathy spine fracture and instability because ankylosis of vertebral segments proximal and distal to the fracture creates long lever arms that cause displacement even in low-energy injuries hyperextension injuries are common seemingly minor, low energy injury mechanisms may result in unstable fracture patterns. One must have increase vigilance in patients with pain and an ankylosed spine Presentation Symptoms often asymptomatic and discovered incidentally thoracic and lumbar involvement mild chronic back pain usually pain is minimal because of stabilization of spinal segments through ankylosis stiffness worse in the morning aggravated by cold weather cervical involvement (with large anterior osteophytes) pain and stiffness dysphagia stridor hoarseness sleep apnea Physical exam decreased ROM of the spine neurologic symptoms of myelopathy or spinal stenosis Imaging Radiographs recommended views AP and lateral spine radiographs of involved region findings non-marginal syndesmophytes at three successive levels (4 contiguous vertebrae) thoracic spine radiographic findings on the right side thoracic spine is often involved in isolation particularly T7-T11 radiographic examination of this area is helpful when attempting to establish a diagnosis of DISH cervical spine anterior bone formation with preservation of disc space (best seen on lateral cervical view) lateral cervical radiographs useful to differentiate from AS AS will demonstrate disc space ossification (fusion between vertebral bodies) lumbar spine symmetrical syndesmophytes (on left and right side of lumbar spine) other joint involvement e.g. elbow Technetium bone scan increased uptake in areas of involvement may be confused with metastases CT or MRI patients with DISH, neck pain and history of trauma must be evaluated for occult fracture with CT Differential DISH vs AS Table DISH Ankylosing spondylitis Syndesmophytes Nonmarginal Marginal Radiographs "Flowing candle wax" "Bamboo spine", squaring of vertebral bodies, "shiny corners" at attachment of annulus fibrosus (Romanus lesions) Disc space Preservation of disc space AS in cervical spine will show ossification of disc space Osteopenia No osteopenia (rather, there may be increased radiodensity) Osteopenia present HLA No evidence of association with HLA-B27 Associated with HLA-B8 (common in patients with DISH and diabetes) Strong association with HLA-B27 Age group Older patients (middle aged) Younger patients SI joint involvement No involvement (SI joint abnormality generally excludes diagnosis of DISH) Bilateral sacroiliitis Diabetes Yes No Diagnosis Diagnostic criteria flowing ossification along the anterolateral aspect of at least 4 contiguous vertebrae preservation of disk height in the involved vertebral segment; relative absence of significant degenerative changes (e.g. marginal sclerosis in vertebral bodies or vacuum phenomenon) absence of facet-joint ankylosis; absence of SI joint erosion, sclerosis or intraarticular osseous fusion Treatment Nonoperative activity modification, physical therapy, brace wear, NSAIDS and bisphosphonate therapy indications most cases cervical traction indications cervical spine fracture use with caution because traction may result in excessive distraction due to lack of ligamentous structures Operative spinal decompression and stabilization indications reserved for specific sequelae (e.g., lumbar stenosis, cervical myelopathy, adult spinal deformity) Complications Mortality for cervical spine trauma in DISH 15% for those treated operatively 67% for those treated nonoperatively higher mortality rates than cervical spine trauma with ankylosing spondylitis similar mortality rates to patients with ankylosing spondylitis overall Heterotopic ossification increased risk of HO after THA 30-50% for THA in patients with DISH <20% for THA in patients without DISH