Ossification of Posterior Longitudinal Ligament
The ligaments in the spine function to provide structural support to the vertebral column. The ligaments also keep a check to prevent excessive motion in the range of movement. The spinal cord lies inside the central vertebral canal formed in the front but the vertebral body and the lamina at the back.
The posterior longitudinal ligament is present in the vertebral body’s back (front of the spinal cord). The ligament flavus is present in the back of the spinal cord.
Causes & Pathology
Ossification means the formation of bone tissue in any tissue. The posterior longitudinal ligament is a flexible ligament which is naturally not ossified. The ossification in OPLL causes the ligament to become rigid and grow in size. The increased size may decrease the precarious space in the vertebral canal already occupied by the spinal cord and its coverings.
The enlargement of the ligament occurs most commonly in the cervical spine and may compress the spinal cord. The compression of the spinal cord may cause symptoms of cervical myelopathy. The ossification of posterior longitudinal ligament occurs most frequently in patients of Asian ancestry, particularly Japanese.
The exact cause of ossification of posterior longitudinal ligament has been unclear but has been thought to be caused by various factors. Diabetes, mechanical factors, a diet rich in salt, high body weight, and genetics have been associated with the ossification of the posterior longitudinal ligament.
The symptoms of OPLL may be mild at first as the disease has a slow progression but may be accelerated in some cases. The patients may complain of pain and stiffness in the neck. There may be symptoms of altered sensation in the arms and hands. Patients may complain of feeling numbness and tingling in the upper extremities.
As the disease progresses and the compression of the cord increases, the patients may complain of clumsiness in their hands. They may experience difficulty in holding and manipulating objects. There may be difficulty walking and navigating stairs. The patients may complain of weakness in the lower extremities. In rare cases, there may be loss of bowel and bladder control.
The physician extracts a thorough history and establishes a timeline of the symptoms. The physician conducts a thorough physical examination. The physical examination includes tests to look for the patient’s walking pattern, the strength in the arms and the legs, and the sensation in all four limbs.
The radiological examination includes an X-ray, CT scan and an MRI. The X-ray is usually the first imaging done in suspected OPLL. The physician is able to see the bone structure as well as ossification of the posterior longitudinal ligament.
A CT scan provides a more detailed image of the bone structures as compared to an X-ray. The MRI scan is able to discern the soft tissue structures including the spinal cord. MRI myelography may be done in patients who are unable to have a regular MRI.
Nonoperative management is done in patients with mild disease. The patients are regularly followed up for observation. The conservative modalities include medications such as nonsteroidal anti-inflammatory medications and physical therapy to improve strength and flexibility.
Surgical management forms the mainstream treatment for patients with functional degradation. The surgical management is done in the form of decompression and stabilization. Different approaches may be used depending upon the patient’s anatomy and the disease process.
The decompression part of the surgery involves removing all the bony/soft tissue structures compressing the spinal cord. The segment of spine is then fused together to eliminate any motion in between the involved vertebrae. The elimination of motion provides stability and prevents any further compression.
The surgeon may access to decompress and fuse the spine either from the front, known as anterior cervical decompression and fusion. Or the surgeon may approach from behind the neck, known as posterior cervical decompression and fusion. In some cases, both anterior and posterior approaches may be used to relieve compression.
Majority of the patients experience significant relief from their symptoms after the surgery. There may be some loss of movement in the range of motion of the neck owing to the fusion.