Ossification of the Posterior Longitudinal Ligament (OPLL) is a progressive spinal condition where the ligament running along the back of the vertebral bodies hardens into bone. This transformation causes the ligament to thicken and lose flexibility, most frequently occurring within the cervical spine, or neck. As the ligament turns into a bone-like mass, it begins to crowd the spinal canal, which contains the spinal cord. This narrowing can lead to the compression of the spinal cord and nerve roots, potentially causing various neurological symptoms. The decision to pursue surgery for OPLL is complex, balancing the risks of the operation against the potential for permanent neurological decline.
Determining the Need for Operation
The primary indication for surgical intervention in OPLL is the presence of myelopathy, which signifies compression of the spinal cord. Symptoms suggesting severe compression include progressive neurological deficits such as motor weakness, difficulty with fine motor skills like buttoning a shirt, and problems with balance or gait disturbance. Patients may also experience numbness, tingling, or pain that radiates into the arms and hands, known as radiculopathy.
The goal of an operation is to prevent further deterioration of neurological function. For patients with mild or no symptoms, conservative treatment like monitoring, physical therapy, and activity modification is often recommended. Imaging studies are essential: Computed Tomography (CT) scans define the extent and density of the ossification, while Magnetic Resonance Imaging (MRI) evaluates the spinal cord itself, identifying signs of compression or injury. Surgery is typically reserved for patients whose symptoms are serious, progressive, or when imaging shows severe spinal canal stenosis.
Anterior Versus Posterior Surgical Strategies
The two main surgical strategies for treating OPLL are determined by the location and extent of the ossification, as well as the overall curvature of the cervical spine. The fundamental principle of both approaches is to decompress the spinal cord and maintain the stability of the spinal column. The choice between the two methods depends on whether the ossified mass is highly localized or spread across multiple vertebral segments.
Anterior Approach (Direct Decompression)
The anterior approach involves accessing the spine through the front of the neck to directly remove the ossified ligament. Procedures like anterior cervical corpectomy and fusion (ACCF) or discectomy and fusion (ACDF) are commonly used to remove the vertebral body or disc spaces contributing to the compression. This technique is favored when the OPLL is localized to a few segments, especially if the ossification occupies a large ratio of the spinal canal, often exceeding 50% to 60%.
The advantage of the anterior approach is the direct relief of pressure on the spinal cord. However, this direct removal can be technically demanding, as the ossified ligament is sometimes tightly adhered to the dura mater, the protective covering of the spinal cord. Due to this proximity, the anterior approach carries a higher risk of complications such as cerebrospinal fluid leakage or spinal cord injury.
Posterior Approach (Indirect Decompression)
The posterior approach accesses the spine from the back of the neck and aims to create more space for the spinal cord, achieving indirect decompression. This strategy is preferred for OPLL that spans three or more vertebral segments or in cases where the spinal canal occupation ratio is lower than 60%. The most common procedures are laminoplasty or laminectomy with fusion.
Laminoplasty involves reshaping the posterior bony arch of the vertebra, known as the lamina, and holding it open with small plates to expand the spinal canal. This allows the spinal cord to move away from the ossified ligament. Laminectomy involves the complete removal of the lamina to relieve pressure, often requiring subsequent fusion to maintain stability. While technically less complex and associated with a lower risk of dural tear compared to the anterior method, the posterior approach may not be suitable if the spine has a significant forward curvature (kyphosis).
Post-Operative Care and Expected Rehabilitation
Immediately following OPLL surgery, patients typically spend a few days in the hospital for monitoring and pain management. Patients are quickly mobilized, with walking encouraged as the best early exercise. Depending on the specific procedure, a cervical collar or brace may be prescribed to limit movement and provide stability during the initial healing period.
For patients who underwent an anterior approach, temporary difficulty or pain with swallowing (dysphagia) is a common short-term side effect. Post-operative restrictions generally include avoiding bending, twisting, and lifting anything heavier than ten pounds for several weeks to protect the surgical site. Formal physical therapy usually begins about four to six weeks after the operation.
Rehabilitation focuses on range-of-motion exercises, endurance, and strengthening to restore function. Neurological recovery can be slow and variable, often continuing for months after the surgery. The most important outcome is the stabilization of the neurological condition and the prevention of further decline.