Diffuse Idiopathic Skeletal Hyperostosis (DISH)

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

Key concept

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

Epidemiology

• Common in older adults; prevalence rises steeply with age and varies widely by definition and population.
• Male predominance (roughly 2:1) and a peak in the 6th decade onward.
• Strong, reproducible associations with type 2 diabetes mellitus, obesity, higher BMI, hyperuricaemia and the metabolic syndrome (according to PubMed, Sarzi-Puttini & Atzeni, Curr Opin Rheumatol 2004; Brikman et al., Semin Arthritis Rheum 2023).
• 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 (according to PubMed, Brikman et al., 2023).

Why it matters for the orthopaedic exam

• Most DISH is asymptomatic and incidental, but candidates are tested on three orthopaedic consequences: the ankylosed-spine fracture, mechanical dysphagia from cervical osteophytes, and the distinction from ankylosing spondylitis.

The enthesis and new bone formation

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

The anterior longitudinal ligament (ALL)

• Runs along the front of the vertebral bodies.
• In DISH it ossifies into a thick anterolateral band that bridges across discs - giving the flowing "dripping candle wax" appearance.
• The disc itself is spared, which is why disc heights stay relatively normal.

The thoracic right-sided 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.

The biomechanics of rigidity

• 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.

Most patients are asymptomatic - DISH is frequently an incidental finding on chest or abdominal imaging.

When symptomatic, think in three buckets:

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

The acute presentation that must never be missed

• An older patient with a stiff spine who has new spinal pain after a seemingly trivial fall.
• Pain may be the only sign initially; deficits can appear or progress hours to days later.

For the common, stable, symptomatic patient:

• Education and reassurance - most DISH is benign and incidental.
• Analgesia (paracetamol, NSAIDs with caution given comorbidity) and physiotherapy for stiffness.
• Metabolic optimisation: weight loss, glycaemic control - the modifiable associations.
• Dysphagia: dietary modification, upright posture, anti-reflux measures and speech/swallow therapy before considering surgery.

Non-operative care of fractures is largely abandoned for unstable three-column injuries because of high rates of displacement, secondary neurology and mortality; it is reserved only for genuinely stable injuries or patients unfit for any surgery, and even then needs close monitoring.

The topic repeatedly flags "difficult intubation", "airway compromise" and "anticipate a difficult airway" but the airway itself is a distinct, examinable hazard in the DISH 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, anteriorly displacing the pharynx and trachea.

Key points

• Routine airway assessment under-predicts the difficulty. In a reported DISH case 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 (according to PubMed, Zhang et al., Ann Transl Med 2021).
• 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 (according to PubMed, Gosavi et al., Asian J Neurosurg 2018).
• 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.
• Generic difficult-airway ladders and general anaesthetic principles belong to the dedicated anaesthesia topics - here the message is that cervical DISH is a specific "difficult airway" flag that standard bedside tests can miss.

DISH is described throughout this topic as a systemic bone-forming diathesis with peripheral enthesopathy ("whiskering" of the pelvis, olecranon, calcaneus). The surgically important consequence of that diathesis is rarely spelled out: a DISH patient is at increased risk of heterotopic ossification (HO) after total hip arthroplasty, and this changes perioperative planning.

Key points

• Increased HO after total hip arthroplasty is a recognised extraspinal manifestation of DISH, and prophylaxis to prevent it may be indicated in these patients (according to PubMed, Belanger & Rowe, JAAOS 2001).
• In HO risk stratification for hip and knee arthroplasty, DISH sits in the moderate-risk group (alongside ankylosing spondylitis and Paget's disease); the highest-risk groups are men with bilateral hypertrophic osteoarthritis, prior HO in either hip, and post-traumatic hypertrophic osteophytosis (according to PubMed, Iorio & Healy, JAAOS 2002).
• Prophylaxis options are 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 (according to PubMed, Iorio & Healy, 2002).
• When radiation is chosen for a high-risk patient (a category that includes DISH), 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 (according to PubMed, Liu et al., J Arthroplasty 2016).
• The generic HO pathophysiology, Brooker grading and full radiotherapy protocols live in the dedicated heterotopic-ossification topics; the DISH-specific message is simply to flag these patients preoperatively and plan prophylaxis.

• 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 from osteophytectomy generally improves, though recurrence is possible because the underlying disease continues.
• 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 (according to PubMed, 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 (according to PubMed, 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 (according to PubMed, Sarzi-Puttini & Atzeni 2004; Brikman et al. 2023).
• Increasingly diagnosed in younger obese patients as CT use rises - 18% in one obese under-50 cohort (according to PubMed, Brikman et al., 2023).

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 (according to PubMed, 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.

• No agreed criteria for early DISH - more than 20 criteria sets exist and disagree, hampering research and earlier diagnosis (according to PubMed, Kuperus et al., Rheumatology 2017).
• Routine MRI in every ankylosed-spine trauma? Evidence suggests MRI changes management in only a minority, supporting a selective (deficit/unexplained pain) rather than reflexive approach (according to PubMed, Tavolaro et al., Spine J 2019).
• Optimal construct length and the role of percutaneous/cement-augmented fixation continue to evolve, balancing biomechanical stability against the morbidity of open surgery in frail patients.
• Aetiology remains "idiopathic" - metabolic and genetic drivers are implicated but no specific disease-modifying drug exists (according to PubMed, Sarzi-Puttini & Atzeni, Curr Opin Rheumatol 2004).