DISH is a systemic condition characterized by the ossification of ligaments and entheses, primarily involving the Anterior Longitudinal Ligament (ALL) of the spine. While it is often asymptomatic and discovered incidentally, it can lead to significant spinal stiffness, dysphagia, and a dramatically increased risk of unstable spinal fractures following minor trauma. For the board-certified physician, the key is to differentiate DISH from its more famous mimic, Ankylosing Spondylitis (AS).

1. Epidemiology and Risk Factors

DISH typically affects older individuals (usually over age 50) and is more common in men.

• Metabolic Association: There is a strong correlation between DISH and metabolic syndromes, specifically Type 2 Diabetes Mellitus, obesity, and hyperinsulinemia.
• Location: It most commonly involves the thoracic spine (T7–T11), followed by the cervical and lumbar regions.

2. The Resnick Diagnostic Criteria

The boards frequently test the specific radiographic requirements that define DISH:

1. Continuous Ossification: Presence of flowing calcification/ossification along the anterolateral aspect of at least four contiguous vertebral bodies (three disc spaces).
2. Preserved Disc Height: Relative preservation of intervertebral disc height in the involved segments (this distinguishes it from degenerative disc disease).
3. Absence of Ankylosis: Absence of apophyseal (facet) joint bony ankylosis and absence of sacroiliac (SI) joint erosion or fusion (this distinguishes it from Ankylosing Spondylitis).

3. Pathophysiology: The “Flowing Wax” Appearance

The ossification in DISH is often described as looking like “candle wax dripping” down the front of the spine.

• The Right-Sided Preference: In the thoracic spine, the ossification is almost always more prominent on the right side. It is hypothesized that the pulsations of the descending aorta on the left side inhibit the formation of bone.
• Enthesopathy: DISH is not limited to the spine. It can cause prominent bone spurs (enthesophytes) at the olecranon, patella, and calcaneus.

4. Clinical Presentation: Stiffness and “Mechanical” Complications

• Spinal Stiffness: Chronic, non-inflammatory stiffness, particularly in the morning, that improves slightly with activity.
• Dysphagia: Large anterior osteophytes in the cervical spine can compress the esophagus, leading to difficulty swallowing or a sensation of a lump in the throat.
• Stridors/Hoarseness: Compression of the larynx or recurrent laryngeal nerve.

5. High-Yield Board Comparison: DISH vs. Ankylosing Spondylitis (AS)

Feature	DISH	Ankylosing Spondylitis (AS)
Age of Onset	> 50 years	< 40 years
SI Joints	Normal	Eroded/Fused (Sacroiliitis)
Facet Joints	Normal	Fused
HLA-B27	No association	Strong association (>90%)
Ossification	Flowing ALL (Thick)	Syndesmophytes (Thin/Vertical)
Disc Height	Preserved	Preserved

[Image comparing the radiographic appearance of DISH and Ankylosing Spondylitis]

6. The “Chalkstick” Fracture Risk

From a PM&R and Trauma perspective, this is the most critical complication of DISH. Because the ossified ALL turns the spine into a rigid, long-lever arm, even minor trauma (like a fall from a standing height) can cause a transverse “Chalkstick” fracture.

• High Instability: These fractures often go through the ossified ligament and the vertebral body, making them highly unstable and prone to spinal cord injury.
• Diagnostic Pearl: Any patient with DISH who presents with new-onset back pain after a fall requires an immediate CT or MRI, even if initial X-rays appear “stable.”

7. Management

• Conservative: NSAIDs for symptomatic pain and physical therapy focusing on maintaining axial range of motion and core stability.
• Surgical: Surgery is rare but may be indicated for severe dysphagia (osteophyte resection) or to stabilize a “Chalkstick” fracture.
• Metabolic Control: Given the link to diabetes, optimizing glucose control may play a role in slowing progression, although this is not yet definitively proven.

---

High-Yield Board “Fast Facts”

• Flowing Wax: The classic description of ALL ossification in DISH.
• Four Contiguous Levels: The requirement for diagnosis.
• Normal SI Joints: The primary way to rule out Ankylosing Spondylitis.
• Dysphagia: A common symptom when the cervical spine is involved.
• Thoracic Spine (Right Side): The most common site of involvement.