Posterior longitudinal ligament ossification (OPLL) is a spinal condition where a specific ligament within the vertebral column abnormally hardens into bone. This condition primarily affects the posterior longitudinal ligament, which runs along the back of the vertebral bodies, inside the spinal canal. Its presence can impact the stability and function of the spinal cord and surrounding nerves.
Understanding Posterior Longitudinal Ligament Ossification
The posterior longitudinal ligament is a flexible band of fibers extending along the back of the vertebral bodies, from the neck down to the sacrum. This ligament helps to stabilize the bones of the spinal column and reinforces the intervertebral discs. It is situated directly adjacent to the spinal cord within the spinal canal.
Ossification refers to the abnormal process where soft tissue transforms into bone. In OPLL, this causes the posterior longitudinal ligament to thicken and harden. This hardening results in osseous projections that can progressively narrow the spinal canal, which is the confined space housing the spinal cord and nerve roots.
The consequence of this narrowing is potential compression of the spinal cord, a condition known as myelopathy, or compression of individual nerve roots, termed radiculopathy. Such compression can impede the normal function of these delicate neural structures. While OPLL can occur throughout the spine, it is most frequently observed in the cervical spine, or neck region, accounting for approximately 75% of cases.
Causes and Risk Factors
The precise cause of OPLL often remains unknown, with most cases considered idiopathic. However, it is widely believed to be a multifactorial condition, meaning both genetic and environmental elements contribute to its development.
There is a strong genetic predisposition associated with OPLL, with familial cases reported in various populations. This condition also shows a higher prevalence in certain ethnic groups, particularly East Asian populations, where the incidence ranges from 0.8% to 3.0%, compared to Caucasians, with an incidence of 0.1% to 1.7%.
OPLL is also linked to various metabolic and endocrine disorders. These include conditions such as diabetes mellitus, obesity, hypophosphatemic rickets/osteomalacia, hypoparathyroidism, and acromegaly/gigantism. In individuals with these associated diseases, OPLL may manifest with earlier onset and greater severity.
Additionally, mechanical stress or microtrauma to the spine has been considered as a contributing factor to the development and progression of OPLL. Factors like prolonged static postures or repetitive movements may influence the expression of genes involved in bone formation within the ligament. The average age of onset for symptomatic OPLL is typically over 50 years, with a male predominance, affecting men at approximately twice the rate of women.
Recognizing the Symptoms
Symptoms of OPLL can vary significantly depending on the location and severity of the ossification and the degree of spinal cord or nerve compression. Initially, individuals may experience no symptoms or only mild discomfort, such as slight pain, tingling, or numbness in the hands.
As the ossified ligament grows and takes up more space within the spinal canal, symptoms typically become more pronounced. Common manifestations include neck stiffness and pain, which may radiate into the arms or legs. Neurological symptoms such as numbness, tingling, or weakness in the arms and legs are also frequently reported. The most common site for OPLL to become symptomatic is the cervical spine, leading to issues in the upper extremities.
More severe neurological symptoms can develop with progressive spinal cord compression. These may include gait disturbances, balance issues, and difficulty with fine motor skills, such as writing or buttoning clothes. Symptoms often progress slowly over time, but in some instances, a sudden worsening can occur after a minor injury.
Diagnosis and Treatment Options
Diagnosing OPLL begins with a thorough clinical evaluation, including a physical and neurological examination to assess symptoms and neurological function. Imaging studies play a central role in confirming the diagnosis and determining the extent of the condition.
X-rays are often the initial imaging modality used, as they can reveal the presence of ossification as a linear density behind the vertebral bodies within the spinal canal. For a more precise visualization of the bone formation and the degree of spinal canal narrowing, a computed tomography (CT) scan is considered the most effective imaging study. CT scans provide detailed images of the ossified ligament’s shape and size, and can show whether the ossification is continuous, segmental, mixed, or localized. Magnetic resonance imaging (MRI) is also used to evaluate spinal cord compression and any associated changes within the spinal cord itself.
Treatment decisions for OPLL are highly individualized, depending on the severity of symptoms and the degree of spinal cord compression. For mild cases or individuals without significant neurological deficits, conservative management is often recommended. This approach may include physical therapy, pain management using medications such as non-steroidal anti-inflammatory drugs (NSAIDs) or anticonvulsants, and watchful waiting with activity modification.
Surgical intervention is generally considered for progressive neurological symptoms or severe spinal cord compression. The primary goal of surgery is to decompress the spinal cord and nerve roots by either removing the ossified ligament or expanding the spinal canal. Common surgical approaches include laminectomy, which involves removing the “roof” of the spinal canal, or laminoplasty, which creates more space for the spinal cord by hinging open the lamina. Anterior decompression techniques, such as anterior cervical corpectomy and fusion, directly remove the vertebral body and the attached ossified ligament. Following surgery, rehabilitation is often important to help patients regain function and mobility.