Any form of narrowing of the spinal canal, nerve root canal, or intervertebral foramen from any cause, resulting in nerve root and/or cauda equina compression syndrome, is collectively referred to as lumbar spinal stenosis. Nerve compression may be limited, segmental or widespread, and the compression may be bony or due to soft tissue.
Etiology Gu Shuming, Department of Orthopedics and Traumatology, Xiyuan Hospital, Chinese Academy of Traditional Chinese Medicine
Developmental spinal stenosis: congenital short pedicle and pedicle coalescence result in small sagittal and transverse diameters of the spinal canal, but there are no symptoms when young, and the spinal canal and its contents gradually become incompatible with each other during development before symptoms of stenosis appear.
Degenerative spinal stenosis: It is the most common cause of lumbar spinal stenosis. After middle age, the spine gradually degenerates, and the degeneration usually occurs first in the intervertebral discs, where the water content of the nucleus pulposus tissue decreases, the discs become narrower, and their original elastic biomechanical function decreases, preventing them from spreading the pressure they bear evenly in all directions. The stenosis and biomechanical changes cause joint disorders, which in turn lead to hypertrophic and proliferative degeneration of the bony and fibrous structures of the spinal canal, resulting in spinal stenosis.
Subtypes
1. Central stenosis is often due to hypertrophy of the lamina and ligamentum flavum and disc degeneration or associated disc herniation. A lumbar spinal canal with an anterior-posterior diameter of less than 10 mm should be considered as central lumbar spinal canal stenosis.
2. Peripheral stenosis can be diagnosed definitely if the anteroposterior diameter of the lateral saphenous fossa is less than 3 mm as measured by CT scan and the clinical symptoms are present.
3. Mixed type with symptoms of both central and peripheral stenosis.
Clinical manifestations
It is more common in middle age and above. It has a history of low back pain and is occasionally aggravated after trauma or weight bearing.
Intermittent claudication is common in people with central spinal stenosis or severe stenosis, and is characterized by pain, numbness, and weakness of the lower extremities after walking a certain distance. As the condition worsens, the distance that can be walked becomes shorter and shorter, so that the time needed to rest for symptom relief becomes longer and longer, but the blood circulation in the lower limbs is normal. When the stenosis is severe, no position of the lower back can relieve the pain.
As the disease progresses, the location of the pain may gradually move down to the lower leg, with local sensory abnormalities and numbness. Some patients may have numbness in the saddle area, swelling and heat sensation and pins and needles sensation. Some patients may have sexual function and bladder and rectal dysfunction. It is characteristic of the disease that early in the disease patients have more symptoms but fewer or lighter signs, especially after rest, and it is more difficult to detect positive signs. There is less restriction of spinal movement, the straight leg raise test is usually negative, and the neurological examination of the lower extremities is generally normal; neurological changes may be detected only after the patient walks as much as possible and has obvious lower extremity symptoms before the examination. The bending test is mostly positive, i.e., if the patient is asked to speed up the walking speed, the pain will increase.
However, when the disease develops to a certain extent, the patient often has scoliosis, paravertebral muscle spasm, lumbar back extension restriction, and positive lumbar hyperextension test during clinical examination. The skin sensation in the area of innervation under pressure is weakened or disappeared, the patient has reduced dorsiflexion of the bunions, weakened or disappeared knee reflexes and Achilles tendon reflexes, and some patients have muscle weakness and atrophy of the lower limbs, numbness in the saddle area, and relaxation of the sphincter muscles. If there is a combination of acute disc herniation and compression of nerve roots, the straight leg raise test may be positive.
Imaging examination
1. x-ray manifestation of the physiological foreshortening or narrowing of the spine, there may be scoliosis; narrowing of the intervertebral space; osteophyte degeneration of the vertebral body edges, hyperplasia of the small synapses, increased density, hypertrophy and hyperplasia of the synapses, narrowing of the synaptic spacing; pseudo-slip of the vertebral body forward, backward or laterally; strips of abnormal density increase between the vertebral plates at the posterior edge of the spinal canal due to thickening and calcification of the ligamentum flavum; 2.
2. Myelography Myelography is of great value in the diagnosis of lumbar spinal stenosis, which shows varying degrees of dural sac filling defects and obstruction. In cases of partial obstruction, the dural sac is narrowed by limited pressure and the contrast column passes slowly, usually at the level of the interproximal joints; in cases of complete obstruction, the cross-section often shows curtain-like, pencil-like or brush-like filling defects. The critical criterion for central canal stenosis is when the sagittal diameter of the dural sac is measured ≤10 mm: nerve root canal stenosis can be diagnosed when the blind diameter of the nerve root canal is ≤4 mm. It also clearly shows the nerve root cuff filling with contrast agent, so that the presence or absence of nerve root canal stenosis and the degree of stenosis can be determined.
3. CT examination CT measurement of patients whose sagittal diameter of the spinal canal is less than 15 mm and presents changes such as lack of epidural fat in the spinal canal, multiple lumbar disc bulges or protrusions, calcification and ossification of the posterior longitudinal ligament, thickening of the ligamentum flavum, formation of bone redundancy at the posterior edge of the vertebral body, and severe intervertebral joint hypertrophy, which are manifestations of central lumbar spinal canal stenosis, and less than 10 mm can be clearly diagnosed. The lateral saphenous fossa is located on the lateral side of the spinal canal, with the posterior side of the vertebral body and intervertebral disc in the front, the superior articular eminence, the vertebral intervertebral joint capsule and the ligamentum flavum in the back, the lateral pedicle, the dural sac in the inside, and the nerve root canal opening in the bottom. If a myelography CT scan (CTM) can be performed, it is easier to clearly show the subarachnoid space, cauda equina and nerve root compression.
4. MRI of lumbar spinal stenosis is characterized by deformation of the subarachnoid space in the lumbar segment with or without compression of the cauda equina and/or nerve roots. At the same time, MRI can clearly show the degree of compression of the spinal cord, cauda equina nerve and nerve roots by disc herniation, vertebral osteophytes, hypertrophy and hyperplasia of small articular processes, and hypertrophy of the ligamentum flavum, etc. The size of the subarachnoid space can also be accurately displayed on T, weighted images, and the narrowing of the spinal canal due to the above factors can be directly observed, reflecting the interrelationship between the spinal canal and its contents.
Diagnosis
The diagnosis can be confirmed based on the history, clinical manifestations, and imaging examinations.
Treatment
Non-surgical treatment is used for lumbar spinal stenosis with mild symptoms that do not seriously affect life and work, including rest, reduced activity, drugs to improve microcirculation, epidural steroid injections, massage with massage, and use of elastic lumbar brace. Surgery is required in cases where non-surgical treatment is ineffective and neurological symptoms are severe. Restoring the volume of the spinal canal is the only treatment to relieve the compression of the nerve and its supply vessels. The less damage to spinal stability caused by surgical decompression, the better.
(I) Non-surgical treatment
Bed rest is a better way to relieve symptoms in the acute phase. After bed rest, local venous return improves, sterile inflammatory reaction (congestion, edema) subsides, the stenosis in the spinal canal is relieved, and with the relaxation of the lumbar back muscles, the subjective symptoms are usually reduced by bed rest for 2 to 3 weeks.
2. Drug treatment.
(1) Traditional Chinese medicine treatment: The disease is mainly caused by deficiency of kidney qi, deficiency of true yin, strain and long-term injury, or invasion by external evil, resulting in stasis of wind, cold and dampness that do not dissipate.
(2) Anti-inflammatory and pain-relieving drug treatment: such as anti-inflammatory pain, ibuprofen, Fenbid, etc. can partially relieve the symptoms.
(3) Massage treatment Manual treatment of lumbar spinal stenosis can activate blood and relax tendons and loosen adhesions, so that symptoms can be relieved or disappear.
(B) Surgical treatment
1. Indications for surgery: (1) restriction of daily activities or unbearable pain that has not been treated with systematic non-surgical treatment; (2) progressive worsening of neurological symptoms, such as weakness of quadriceps muscle and inability to extend the ankle joint dorsally; (3) bladder dysfunction.
2. The purpose of surgery is to prevent further aggravation of dysfunction, reduce pain and improve daily activities. It should be made clear to the patient that the functional improvement is obvious after surgery, but the prognosis of low back pain is unpredictable. Sometimes the surgery is very thorough, but the low back pain still exists.
The choice of surgical procedure depends on the patient’s symptoms and examination. (1) Total laminectomy and decompression. (2) Multi-segmental laminectomy and decompression. (3) Arthrocentesis partial decompression. (4) Total laminectomy decompression with bone graft fusion. (5) Total laminectomy decompression with bone graft fusion plus internal fixator fixation. (6) Limited decompression lumbar posterior structural reconstruction.