Definition
The posterior longitudinal ligament: starts from the 2nd cervical vertebra and runs along the back of the vertebrae against the sacral canal. The posterior longitudinal ligament in the cervical vertebrae is divided into two layers: its superficial layer is a strong ligament that descends vertically from the skull base and extends laterally to the intervertebral foramen; its deeper layer is dentate, and some fibers of the joint capsule of the vertebral body hook vertebral joint and start at this layer.
With the growth of age, due to the role of many factors in the formation of new ectopic bone structures in the posterior longitudinal ligament and gradually ossification, resulting in the narrowing of the spinal canal and intervertebral foramen, compression of the spinal cord, nerve roots, clinical symptoms of spinal cord damage and nerve root irritation symptoms, that is, ossification of posterior longitudinal ligament (OPLL).
In 1960, Japanese scholars found that the ossification of posterior longitudinal ligament of the cervical spine led to spinal cord compression during autopsy, and in 1964, Terayma named the pathological change “ossification of posterior longitudinal ligament of the cervical spine”, which was widely accepted and became an independent clinical disease.
Etiology
1.The role of substances related to bone metabolism
2.Genetic basis
3.Local factors
Local factors
Relationship with cervical degeneration: Some scholars believe that cervical OPLL is not only a pathology occurring in the posterior longitudinal ligament itself, but sometimes it may be caused by the wave of proliferating bone flab to the posterior longitudinal ligament after cervical degeneration. Relationship with disc herniation: In animal experiments, it was found that disc herniation after nucleus pulposus enlargement, rupture of cartilaginous tissue of the fibrous annulus and regenerative proliferation of chondrocytes could excite experimental animals leading to the onset of ossification of the posterior longitudinal ligament. In addition cervical spine surgery has also aggravated and accelerated the rate of ligament ossification.
Clinical presentation.
The onset and development of ossification of the posterior longitudinal ligament in the cervical spine are generally slow, so patients may not show any clinical symptoms in the early stage, but when the ossified mass thickens and widens to a certain degree causing cervical spinal stenosis, or when the lesion progresses quickly and in case of trauma or when the ossification of the posterior longitudinal ligament is not serious but accompanied by developmental spinal stenosis, it may cause compression of the spinal cord or spinal blood vessels, and thus patients tend to show symptoms after middle age.
In the early stage of the lesion, the patient’s neck can be painless and gradually develop mild pain and discomfort; most of the cervical spine activities are normal or mildly restricted, with posterior extension of the head and neck being obvious; when the passive activities exceed the normal range of activities, it can cause pain or soreness in the neck.
Neurological symptoms
The main symptom is spinal cord compression, which is characterized by intermittent, chronic progressive, spastic tetraplegia of varying degrees. The symptoms usually start in the lower extremities and gradually appear in the upper extremities. In a few cases, upper extremity symptoms may appear first or all four extremities may develop at the same time. Upper limb symptoms: mainly one or bilateral hand or arm muscle strength is weakened, and numbness and weakness and reduced flexibility of hand activities appear, and in severe cases, the patient is unable to hold pens and chopsticks or pinch small objects; the patient’s grip strength is mostly reduced, and the muscles are moderately or mildly atrophied, especially the large and small fissures are obvious.
Neurological symptoms
Lower limb symptoms The main symptoms are weakness of both lower limbs and difficulty in lifting, dragging the ground or trembling gait, and a feeling of stepping on cotton. If the spasm of the adductor muscle is obvious, the walking gait is scissor-like. At the same time, there may be numbness, weakness and spasticity of both lower extremities, and in severe cases, the person cannot sit up and turn over by himself, and is completely paralyzed in bed. The tendon reflexes of the lower limbs are hyperactive or active, the patellar clonus is positive, the pathological reflexes are mostly positive, and there may be deep sensory and superficial sensory hyposensitivity.
Other symptoms The main symptom is urethral sphincter dysfunction, manifested as urinary difficulty or urinary incontinence; defecation function is also mostly low, once every 3 to 5 days, often with constipation and abdominal distension. Patients may have a banding sensation in the chest and abdomen, and it is easy to detect painful dysesthesias, and the abdominal wall reflex and testicular reflex are weak or absent.
Imaging examination
X-ray examination: performance and type of ossification, X-ray film of ossification of the posterior longitudinal ligament of the cervical spine is mainly characterized by abnormal high-density strip shadows at the posterior edge of the vertebral body. To accurately determine the degree of stenosis, plain radiographs and tomograms can be used to measure the stenosis rate of the spinal canal. The stenosis rate is the ratio of the maximum anteroposterior diameter of the ossified mass to the sagittal diameter of the vertebral canal in the same plane on a lateral view.
CT scan
is an important method for diagnosing ossification of the posterior longitudinal ligament, allowing the morphological distribution of the ossified mass and its relationship to the spinal cord to be observed and measured in cross-section. On CT scan images, a high density ossified mass is seen at the posterior edge of the vertebral body protruding into the spinal canal, narrowing the spinal canal, reducing its volume, and displacing the spinal cord and nerve roots by compression. The cross-sectional stenosis rate of the spinal canal can be used to indicate the degree of spinal canal stenosis, and the development of ossification in the longitudinal and lateral directions of the spinal canal if the sagittal reconstruction of the cross-sectional images is performed. This provides a more comprehensive understanding of the extent of ossification of the posterior longitudinal ligament.
MRI scan
The normal or abnormal condition of the ligament can be determined based on the morphology and signal changes of the spinal ligament. On T1-weighted and T2-weighted images of MRI, the ossified posterior longitudinal ligament often projects into the spinal canal with low signal intensity, and is seen to have reduced extradural fat and dural sac compression. On the corresponding cross-sectional view, the ossified posterior longitudinal ligament with low signal at the posterior edge of the vertebral body is seen to compress the spinal cord and nerve roots from the anterior part of the spinal canal.
Diagnosis
Combine symptoms, signs and imaging; pay attention to the differential diagnosis of similar diseases and do not miss patients with thoracic spinal stenosis.
Treatment
Non-surgical treatment: Non-surgical treatment can be used for those with mild symptoms, or those with significant symptoms but can be relieved by rest, and those with organic diseases at older ages. Commonly used are continuous cranial traction, bed rest, cervical brace immobilization, physical therapy and medication.
Since the ossified block of the posterior longitudinal ligament can produce both direct successive compression on the spinal cord and friction on the spinal cord during cervical activities, the irritation caused by friction can be eliminated by fixing the neck with conservative therapy, and the results achieved are often better than expected. Intermittent traction and tui-na therapy for the cervical spine have been reported to cause aggravation of symptoms and should be used with caution. In addition to the injection of anti-inflammatory and analgesic drugs and neurotrophic drugs, nerve growth factor has recently been used in clinical practice and has shown certain efficacy.
Surgical treatment and methods
Patients with ossification of the posterior longitudinal ligament of the cervical spine should first take conservative treatment, and consider surgery if conservative treatment is still ineffective after a period of time. The posterior, anterior and combined anterior and posterior surgeries are chosen according to the specific conditions of the patient.