Skeletal hyperostosis involves the excessive growth of new bone tissue where ligaments and tendons attach to bones, an area known as an enthesis. The body calcifies these soft tissues, leading to ossification, which is the formation of bone within them. This abnormal growth can occur in various parts of the skeleton, with effects depending on the location and extent of the new bone.
Types and Affected Areas
The most common form is Diffuse Idiopathic Skeletal Hyperostosis (DISH). The term “idiopathic” means its cause is unknown. DISH is characterized by the ossification of spinal ligaments, which creates a distinct “flowing” or “dripping candle wax” appearance on medical imaging as new bone cascades down the vertebrae.
This process most frequently impacts the thoracic spine (the middle and upper back), with bone growth often occurring along the right side of the vertebrae in this region. While the thoracic spine is the most common site, the condition can also affect the cervical spine in the neck and the lumbar spine in the lower back.
Beyond the spine, DISH can manifest in the peripheral skeleton (the limbs). Common sites for this bone formation include:
- Heels (at the Achilles tendon insertion)
- Elbows (at the olecranon process)
- Kneecaps
- Pelvis
Symptoms and Associated Conditions
Many people with skeletal hyperostosis experience no symptoms, with the condition often discovered by chance during an X-ray or other imaging for an unrelated issue. When symptoms arise, they include persistent spinal stiffness, particularly upon waking in the morning or during cold weather. This stiffness is often accompanied by a reduced range of motion and mild to moderate pain in the neck or upper back.
In some instances, bone overgrowth leads to more specific complications. Bone spurs in the neck can press on the esophagus, causing difficulty swallowing (dysphagia). This pressure can also affect the airway, leading to a hoarse voice or contributing to sleep apnea, while nerve compression in the lower back may result in tingling or numbness in the legs.
Skeletal hyperostosis has a strong association with certain metabolic conditions, suggesting these factors may play a role in its development. Research shows a clear link between DISH and disorders such as:
- Type 2 diabetes
- Obesity
- Hypertension (high blood pressure)
- Hyperinsulinemia (high blood insulin levels)
Diagnosis and Medical Evaluation
Diagnosis is primarily made through medical imaging, with spinal X-rays being the standard tool. A definitive diagnosis of DISH requires identifying the characteristic “flowing” ossification that connects at least four consecutive vertebrae. This continuous bone formation along the front and side aspects of the vertebrae is a hallmark of the condition.
To distinguish DISH from other spinal disorders like ankylosing spondylitis, clinicians look for two other important signs. The first is the preservation of intervertebral disc height between the affected vertebrae. Unlike some other forms of spinal arthritis, DISH does not cause the discs to degenerate and narrow.
Another distinguishing feature is the absence of fusion in the sacroiliac joints, which connect the spine’s base to the pelvis. These joints are commonly fused in ankylosing spondylitis but remain unaffected in DISH. While X-rays are sufficient for diagnosis, a computed tomography (CT) scan may be ordered for a more detailed, three-dimensional view of the bone growth, especially if there are concerns about nerve compression or before a surgical procedure.
Managing Skeletal Hyperostosis
With no cure available, management focuses on alleviating symptoms and preserving quality of life through a conservative, non-surgical approach. Physical therapy is a primary component of this management plan. It emphasizes stretching and range-of-motion exercises designed to improve flexibility and combat spinal stiffness.
For pain relief, over-the-counter nonsteroidal anti-inflammatory drugs (NSAIDs) are recommended to manage back and neck pain. These medications can help reduce inflammation, making it easier for individuals to engage in physical therapy and daily activities. Consistent, gentle exercise is also encouraged to help maintain mobility.
A large part of managing DISH involves addressing the associated metabolic conditions. Patients are advised to work with healthcare providers to control blood sugar, maintain a healthy weight, and manage blood pressure. Addressing these related health issues can positively impact overall well-being and may influence symptom progression.
In rare cases, surgery may be considered for individuals who develop severe complications. For instance, a procedure to remove a large bone spur might be necessary if it significantly obstructs the esophagus and causes severe swallowing difficulty. Surgery may also be required if bone growth leads to compression of the spinal cord.