Diffuse Idiopathic Skeletal Hyperostosis (DISH)

What it is. DISH (Forestier's disease) is a systemic, non-inflammatory enthesopathy: progressive calcification and ossification of ligaments and entheses, most prominently the anterior longitudinal ligament of the spine. The result is flowing, "candle-wax" new bone that bridges vertebrae and stiffens the spine.

What it is not. It is a disease of abnormal new bone formation at entheses, not of inflammation or of the disc. Because the discs and the facet and SI joints are spared, DISH is distinguished from both ankylosing spondylitis and degenerative spondylosis (Mader et al., RMD Open 2020).

Who gets it. DISH is common in older adults, with a male predominance of roughly 2:1 and a peak from the sixth decade onward. Prevalence rises steeply with age and varies widely by definition and population. The associations are strong and reproducible (Sarzi-Puttini & Atzeni, Curr Opin Rheumatol 2004; Brikman et al., Semin Arthritis Rheum 2024):

• Type 2 diabetes mellitus
• Obesity and higher BMI
• Hyperuricaemia
• The metabolic syndrome

Younger patients. DISH is increasingly recognised in younger obese patients. In one bariatric cohort, 18% of obese patients aged 50 or under met Resnick criteria, far above the expected general-population rate (Brikman et al., 2024).

Why it matters in the exam. Most DISH is asymptomatic and incidental. Candidates are tested on three orthopaedic consequences: the ankylosed-spine fracture, mechanical dysphagia from cervical osteophytes, and the distinction from ankylosing spondylitis.

The enthesis. The primary lesion is at the enthesis, where ligament or tendon inserts into bone. New bone forms through both endochondral and membranous ossification, driven by metabolic and growth-factor signalling rather than inflammation (Sarzi-Puttini & Atzeni, Curr Opin Rheumatol 2004). Candidate metabolic mediators include insulin/IGF-1, which links the disease to diabetes and obesity, and matrix Gla protein.

The anterior longitudinal ligament. It runs along the front of the vertebral bodies, and in DISH it ossifies into a thick anterolateral band that bridges across the discs, giving the flowing "dripping candle wax" appearance. The disc itself is spared, which is why disc heights stay relatively normal.

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Right-sided thoracic predominance. DISH characteristically favours the right side of the thoracic spine, around T7-T11. The classic explanation is mechanical: the pulsatile descending thoracic aorta lies on the left and is thought to suppress ossification on that side, so new bone forms preferentially on the right.

Why the rigid spine breaks. As segments bridge, the spine loses its normal shock-absorbing flexibility and behaves like a single long bone. Combined with age-related osteoporosis, this creates a long, brittle lever arm, the central reason ankylosed spines fracture from trivial force.

The Resnick and Niwayama criteria. The reference standard is radiographic. DISH is diagnosed when all three are present:

1. Flowing ossification along the anterolateral aspect of at least 4 contiguous vertebral bodies
2. Relative preservation of disc height at the involved levels, which excludes degenerative spondylosis
3. Absence of apophyseal (facet) joint ankylosis and of sacroiliac erosion, sclerosis or fusion, which excludes ankylosing spondylitis

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Early disease has no agreed definition. A systematic review found no consensus for diagnosing early DISH: over 20 partly overlapping criteria sets exist and disagree, hampering research and earlier diagnosis, although spinal hyperostosis is required by all (Kuperus et al., Rheumatology 2017). DISH is best thought of as a spectrum, a progressive condition rather than a single dichotomous state, which is exactly why the criteria sets disagree on early disease.

Axial and extraspinal disease. The burden of disease is described in two territories:

• Axial DISH: spinal involvement, typically thoracic first, then lumbar and cervical
• Peripheral (extraspinal) DISH: enthesopathy at the pelvis (iliac crest, ischial tuberosity), patella, calcaneus, olecranon and elsewhere, the "whiskering" of entheses

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The ankylosed-spine fracture. The principles of ankylosing spondylitis fractures apply: these are unstable three-column injuries until proven otherwise. The mechanism is typically hyperextension, so injuries are often extension or distraction type and may open anteriorly; the line is often transverse and frequently passes through a disc. They are classified with AO Spine, and in a DISH MRI series the commonest pattern was a transverse AO type B (distraction) fracture through the vertebral body or disc (Vierunen et al., Eur Radiol 2023).

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Most patients have no symptoms. DISH is frequently an incidental finding on chest or abdominal imaging. When it does cause symptoms, think in three groups:

• Axial: thoracolumbar stiffness and a dull ache, reduced spinal range of motion, and reduced chest expansion if the disease is extensive
• Cervical mass effect: dysphagia from large anterior cervical osteophytes compressing the pharynx or oesophagus (Forestier dysphagia); rarely stridor, hoarseness or difficult intubation
• Neurological: usually only when DISH coexists with OPLL, whose posterior ossification produces canal stenosis and myelopathy, or after a fracture

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The presentation that must never be missed. An older patient with a stiff spine and new spinal pain after a seemingly trivial fall. Pain may be the only sign at first, and deficits can appear or progress hours to days later.

The two great mimics. Ankylosing spondylitis also gives a "fused" spine, and degenerative spondylosis also makes osteophytes; the second and third Resnick criteria exist to exclude them. DISH and AS are opposites in mechanism, and against AS the sacroiliac joints are the single best discriminator: spared in DISH, eroded then fused in AS.

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The pathway. Treatment follows the presentation:

1. Incidental, asymptomatic DISH: reassure and address metabolic risk factors (diabetes, weight); no spinal intervention
2. Axial stiffness or pain: analgesia, physiotherapy, activity modification
3. Cervical dysphagia: ENT and swallow assessment, conservative measures first, then anterior osteophytectomy if refractory or causing airway compromise
4. Suspected fracture (any new pain after trauma): immobilise, CT the whole spine, add MRI if a deficit or haematoma is suspected, then surgical stabilisation for unstable injuries
5. Coexisting OPLL with myelopathy: manage as a stenosis and myelopathy problem, with decompression with or without fusion

Non-operative care. This is for the common, stable, symptomatic patient. Most DISH is benign, so education and reassurance come first, with analgesia (paracetamol, and NSAIDs with caution given the comorbidity) and physiotherapy for stiffness. Weight loss and glycaemic control address the modifiable associations.

Dysphagia before surgery. Dietary modification, upright posture, anti-reflux measures and speech and swallow therapy are tried before osteophytectomy is considered.

The fracture is not braced. Treat the ankylosed-spine fracture like an ankylosing spondylitis fracture: assume gross instability, and make operative stabilisation the default, not a collar. Non-operative care is largely abandoned for unstable three-column injuries because of high rates of displacement, epidural haematoma, secondary neurology and mortality. It is reserved for genuinely stable injuries or patients unfit for any surgery, and even then needs close monitoring.

Pre-injury posture. From the first transfer to final positioning on the table, keep the spine in the patient's pre-injury alignment. Forced repositioning of a kyphotic or hyperextended spine into a flat one risks cord injury.

Why the airway is hard. Cervical DISH is a distinct, examinable airway hazard in a patient coming for any operation, not just cervical surgery. Two problems combine: a rigid, ankylosed cervical spine that will not extend, and bulky anterior osteophytes that distort and narrow the laryngopharynx, displacing the pharynx and trachea anteriorly.

Routine assessment under-predicts it. In one reported DISH case, radiographs had not predicted the problem and the Mallampati score was class III, yet video laryngoscopy, direct laryngoscopy, a laryngeal mask and an optical stylet all failed. An unexpected posterior pharyngeal bulge from the osteophyte blocked tube placement, and only flexible fibreoptic nasal intubation succeeded (Zhang et al., Ann Transl Med 2021).

The plan. Awake flexible fibreoptic intubation with a small-calibre tube is the reliable technique in a spine bridged from C2 to C7, preserving spontaneous ventilation and avoiding forced neck manoeuvres (Gosavi et al., Asian J Neurosurg 2018). Video or direct laryngoscopy cannot be relied on, because osteophyte-related laryngopharyngeal distortion can defeat them. Do not force neck extension in the fused cervical spine, and involve senior anaesthesia and ENT early. Preoperative CT, and in complex cases 3D assessment, helps map osteophyte size and location before induction.

How strong the evidence is. The two reports above are the airway evidence on this page: two patients. That is enough to justify anticipating difficulty and preparing an alternative, not enough to mandate awake fibreoptic intubation for every cervical DISH.

Scope. Generic difficult-airway ladders and general anaesthetic principles belong to the anaesthesia topics. The message here is that cervical DISH is a specific difficult-airway flag that standard bedside tests can miss.

The hip in a bone-forming disease. DISH is a systemic bone-forming diathesis with peripheral enthesopathy, and its surgically important consequence is an increased risk of heterotopic ossification (HO) after total hip arthroplasty, which changes perioperative planning. Increased HO after hip arthroplasty is a recognised extraspinal manifestation of DISH, and prophylaxis to prevent it may be indicated (Belanger & Rowe, JAAOS 2001).

Where DISH sits on the risk scale. In HO risk stratification for hip and knee arthroplasty, DISH is in the moderate-risk group, alongside ankylosing spondylitis and Paget's disease. The highest-risk groups are men with bilateral hypertrophic osteoarthritis, patients with prior HO in either hip, and post-traumatic hypertrophic arthritis (Iorio & Healy, JAAOS 2002).

Prophylaxis. Either a single fraction of peri-operative radiation or an NSAID regimen, given before the fifth postoperative day and optimally within 24 to 48 hours. Recurrence after surgical excision should be expected unless prophylaxis is used (Iorio & Healy, 2002).

The radiation dose. When radiation is chosen, a randomised trial found 700 cGy superior to 400 cGy in preventing HO progression on the Brooker scale after total hip arthroplasty, with no wound complications (Liu et al., J Arthroplasty 2017). The trial compared two doses, not radiation against none, and reported no DISH-specific subgroup.

Two meanings of high risk. The trial's enrolment criterion of "high risk" included DISH, whereas the Iorio stratification places DISH at moderate risk: the same phrase in two different schemes.

Scope. Generic HO pathophysiology, Brooker grading and full radiotherapy protocols belong to the heterotopic-ossification topics. The DISH-specific message is to flag these patients preoperatively and plan prophylaxis.

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After fracture fixation, days 0-14. Mobilise as early as the construct and comorbidities allow; these elderly patients deteriorate quickly with immobility, through pneumonia, VTE, delirium and pressure injury. VTE prophylaxis, careful glycaemic control and aggressive medical co-management follow: postoperative medical complications occurred in 45.8% of Buxbaum's ankylosed-spine fixation series. Monitor neurology closely in the first days for a delayed deficit from haematoma or displacement.

After cervical osteophytectomy. Watch the airway and swallowing closely in the early postoperative period, because oedema can transiently worsen dysphagia.

Long term. Serial radiographs confirm union and maintained alignment after fracture fixation, and diabetes and weight are reassessed. Recurrent dysphagia after osteophytectomy merits re-imaging for regrowth.

Incidental DISH has an excellent prognosis. It is the associated metabolic disease (cardiovascular risk, diabetes) that drives long-term health, not the spinal ossification itself.

Dysphagia generally improves after osteophytectomy.

Ankylosed-spine fractures carry a sobering prognosis: high rates of spinal cord injury, neurological deterioration, medical complications and mortality, reflecting both the injury and the comorbid, elderly population. In post-traumatic DISH MRI series, spinal cord injury was present in the majority of those imaged, and spinal epidural haematoma was a frequent, potentially treatable contributor (Vierunen et al., Eur Radiol 2023).

Global epidemiology

• DISH is common in older adults worldwide; prevalence rises with age and is reported across all populations, with figures varying widely because criteria differ (Kuperus et al., Rheumatology 2017).
• Consistent male predominance (~2:1) and strong associations with type 2 diabetes, obesity, hypertension and the metabolic syndrome are seen internationally (Sarzi-Puttini & Atzeni 2004; Brikman et al. 2024).
• Increasingly diagnosed in younger obese patients as CT use rises - 18% in one obese under-50 cohort (Brikman et al., 2024).

Side-by-side guideline / consensus positions

Registry / outcome evidence

• There is no dedicated DISH implant registry; the evidence base is retrospective cohorts and case series (e.g. MRI trauma cohorts, percutaneous fixation series).
• These consistently show frequent epidural haematoma and spinal cord injury after low-energy trauma and good union with cement-augmented, often percutaneous, long constructs in frail patients (Vierunen 2023; Buxbaum 2021).

High- vs limited-resource practice variation

• High-resource settings: whole-spine CT (and selective MRI) for any ankylosed-spine trauma; percutaneous, cement-augmented long-segment fixation; multidisciplinary frailty co-management.
• Limited-resource settings: greater reliance on plain films (which miss these fractures) and open surgery; the universal priority everywhere is a low threshold to image the whole spine in a rigid spine with new pain.

Construct length and technique. The optimal construct length, and the role of percutaneous and cement-augmented fixation, continue to evolve, balancing biomechanical stability against the morbidity of open surgery in frail patients.

Aetiology. DISH remains "idiopathic". Metabolic and genetic drivers are implicated, but no specific disease-modifying drug exists (Sarzi-Puttini & Atzeni, Curr Opin Rheumatol 2004).

Diagnosis and imaging. The lack of agreed criteria for early DISH and the case against routine MRI after every ankylosed-spine injury are set out under Classification Systems and Imaging and Investigations.