Ossification of the Posterior Longitudinal Ligament (OPLL)
OPLL is ossification (bone formation) of the posterior longitudinal ligament of the spine. It most often affects the cervical (neck) region and can narrow the spinal canal over time, causing spinal cord compression (myelopathy). It is more common in people of Asian descent and is a slowly progressive disease, often asymptomatic at first.
Останнє оновлення: 2026-06-06
Definition
OPLL (ossification of the posterior longitudinal ligament) is a progressive disease characterized by bone formation within the posterior longitudinal ligament, which runs along the back of the vertebral bodies inside the spinal canal. The ossified ligament narrows the canal; chronic compression of the spinal cord and nerve roots can cause myelopathy and radiculopathy. It is most common in the cervical (neck) region, particularly at C3-C6, with thoracic and lumbar involvement being rarer.
Causes and Risk Factors
The cause is multifactorial. There is a strong genetic predisposition: the disease is markedly more common in Asian populations (Japan, Korea, China) and shows familial clustering, with gene polymorphisms in collagen and bone metabolism described. Metabolic factors include diabetes mellitus, obesity and hyperinsulinemia. Diffuse idiopathic skeletal hyperostosis (DISH) frequently coexists. Hormonal conditions such as acromegaly, chronic mechanical stress and repetitive neck trauma also contribute. It is more common in men and is usually diagnosed between ages 50 and 60.
Classification
On CT-based morphology, four types are defined: segmental (isolated at each vertebral level, the most common), continuous (uninterrupted across several levels, with a high risk of severe compression), mixed, and localized/circumscribed (focal at a disc level, the mildest). The degree of compression is assessed by the ratio of ossification thickness to canal diameter (canal-occupying ratio). On lateral radiograph/MRI, the K-line connecting the posterior corners of C2 and C7 guides surgical planning: if the mass lies in front of the K-line (K-line positive) a posterior approach may be used, whereas if it crosses the line (K-line negative) an anterior approach may be preferred.
Symptoms
OPLL progresses slowly over years and many patients remain asymptomatic for a long time. When symptomatic, the most common picture is cervical myelopathy: loss of fine hand dexterity (buttoning, writing difficulty), numbness, and neck pain and stiffness are early signs; as it progresses, gait disturbance, imbalance, weakness, spasticity, Hoffmann's and Babinski's signs and, in advanced stages, bladder-bowel symptoms appear. Some patients have radiculopathy from nerve-root compression (radiating arm pain, dermatomal numbness, weakness). In patients with a narrow canal, a minor injury can cause sudden neurological deterioration.
Diagnosis
Diagnosis is made by imaging. A lateral cervical radiograph may show the ossification. CT most accurately demonstrates its structure, type and the degree of canal narrowing and is essential for surgical planning; it also reveals features that increase surgical difficulty, such as dural ossification. MRI shows cord compression and intramedullary signal change (myelomalacia/gliosis), which carry prognostic importance. Clinical severity is graded with the JOA (Japanese Orthopaedic Association) myelopathy score.
Treatment Options
Asymptomatic or mild cases are managed with regular clinical and radiographic follow-up; avoidance of neck trauma, symptom management (analgesics, physical therapy) and control of risk factors (diabetes, obesity) are advised. Surgical decompression is indicated for progressive or moderate-to-severe myelopathy. Posterior approaches (laminoplasty or laminectomy with or without fusion) are often preferred for multilevel involvement and K-line-positive cases. Anterior decompression and fusion (with corpectomy when needed) is used for K-line-negative, limited-level cases with marked anterior compression; the risk of CSF leak is higher because of dural ossification.
Prognosis
The main aim of surgical decompression is to halt progression of myelopathy and, where possible, improve neurological function. The outcome depends on the duration and severity of preoperative myelopathy and the degree of permanent cord injury; earlier intervention is associated with better results. Because the disease is progressive, follow-up remains important after surgery. Outcomes vary individually.
Джерела
- Greenberg MS. Greenberg's Handbook of Neurosurgery. 10th ed. Thieme; 2023:1370.
- Winn HR, ed. Youmans Neurological Surgery. 6th ed. Saunders; 2011.
- Fehlings MG, et al. A Clinical Practice Guideline for the Management of Degenerative Cervical Myelopathy. Global Spine J. 2017.
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