Spinal decompression is performed to relieve spinal stenosis or narrowing of the spinal canal usually resulting in pressure on nerves or the spinal cord.

The decision to perform spinal decompression is based on three factors: Patient's symptoms, findings on physical exam, and radiographic abnormalities. Laminectomy, laminotomy and foramenotomy are three technical terms which all describe surgical enlargement of the spinal canal to relieve pressure on nerves. In the past laminectomy was used to refer to removal of a disc, although this is now more accurately referred to as a discectomy. Each procedure can be performed in the cervical, thoracic or lumbar spine.

Symptoms associated with spinal stenosis can include pain, weakness, numbness and imbalance. The patient's pain symptoms can be categorized into three patterns. Axial pain is that which occurs along the spine and the overlying musculature. Referred pain is that which occurs along the buttocks or pelvic region in the lumbar spine or the shoulder and scapula in the cervical region. Radicular pain is that which extends partially or completely along the length of the leg or arm.

Axial pain is generally vague and is typically similar irrespective of the underlying problem. Referred pain into the pelvis or buttocks is also generally vaguely defined. These patterns of pain may be due to irritability of small nerves along the surface of discs or joints and it is difficult to differentiate these patterns of pain from soft tissue inflammation such as ligamentous injuries or tendonitis. Instability of joints or vertebrae in the lumbar spine can also produce similar patterns of referred pain. Radicular pain typically conforms to a specific nerve root distribution or course. A radicular pattern of pain is most easily identified as specifically related to nerve root impingement and as such is generally most accurately correlated with a specific abnormality within the spine.

Radicular symptoms in stenosis may be vaguely defined. Typically they are increased with ambulation and positions which extend the spine. Ideally, symptoms of radicular pain are clearly present and are greater than patterns of referred or axial pain. Radicular pain usually responds well to relief of pressure on spinal nerves whereas referred and axial pain responds less predictably. This may occur due to the relationship between these patterns of pain and degenerative change within the discs, joints etc., which persist despite neural decompression.

Physical Findings

Physical findings can generally be divided into three groups: Limitation of motion, the presence of tenderness and neurological deficits. While limited range of motion in the lumbar or cervical spine is frequently present, it is a very nonspecific finding and does not reflect any particular abnormality which would suggest an indication to perform a spinal decompression. However, reproduction of symptoms on standing or extension of the lumbar or cervical spine with relief on flexion or bending is very suggestive of spinal stenosis. Tenderness is also frequently present and may be diffusely noted along the musculature and joints and is usually present over the sciatic notch in patients with complaints of sciatic nerve irritation. The sciatic notch is located in the lower buttocks and is the point origin of the sciatic nerve from the pelvis. Similar patterns of tenderness may be present over the supraclavicular fossa or scapular boarders with cervical nerve impingement. Tensions signs, such as the straight-leg raising maneuver, are another method of eliciting tenderness in the patient. These techniques involve stretching the affected nerve and recreating the symptomatic leg pain. In lumbar spinal stenosis, the femoral stretch test, which elicits pain along the femoral nerve, and the straight leg raise, which elicits pain along the course of the sciatic nerve, are commonly negative.

Neurological deficits are the most specific indicator of cervical or lumbar nerve root compression. Neurological deficits include loss of a specific reflex, loss of sensation in a specific area correlating with a particular nerve, or loss of strength in a muscle or muscles conforming to a particular nerve.

Central stenosis of the cervical or thoracic spine causes compression on the spinal cord and may result in increased or spastic reflexes, loss of strength, sensation and imbalance. Weakness may be subtle and present as merely fatigue in the legs on walking. Narrowing of the neuro foramen within the cervical and thoracic spine may also produce numbness and weakness, but is also usually productive of radicular pain, which may not exist in central stenosis. Similarly, stenosis of the lumbar canal, central, lateral or foraminal, may produce pain, numbness or weakness of the lower extremities but does not produce reflex spasticity.

In general, patients are usually not considered for surgical treatment until a period of six to eight weeks of nonoperative care has been attempted. This treatment would generally include restricted activity, physical therapy or chiropractic treatment, anti-inflammatory medication, narcotic analgesics and muscle relaxants, and possibly epidural cortisone injections. Several factors may indicate a need for more expeditious surgical treatment. These factors would include incapacitating unremitting pain, compression on a nerve root resulting in progression of a neurological deficit posing a potential functional impairment, or development of bowel or bladder dysfunction, or symptomatic compression on the spinal cord.

Radiographic Abnormalities

Radiographic indications for surgical treatment would include the presence of spinal stenosis on MRI, CT scan, or myelography. Stenosis can occur as an isolated abnormality or in combinations of multiple abnormalities. Stenosis is usually defined by the area of narrowing, in the central canal, in the lateral recess and in the foramen. Stenosis may be congenital or acquired. Congenital stenosis refers to the canal being smaller due to an inherent tendency the patient is born with. Acquired stenosis is usually due to progressive narrowing from bone spur formation, disc bulging and other degenerative changes, or subluxation of vertebrae. Fibrosis or scarring and hardening of old herniated discs can also result in stenosis.

Surgical Techniques

Spinal stenosis can be addressed either microsurgically or in a traditional manner, depending on the number of levels affected. The basis for any microsurgical procedure is the use of magnification and bright illumination of the operative field. This can be provided to a satisfactory degree by use of an operative microscope, operative magnifying loupes, and fiberoptic head lamp. The primary advantage of microsurgery is a reduction of tissue trauma, a decrease in operative recovery, and a reduction of postsurgical scarring and operative trauma. Microsurgery can be performed at one or more levels, either unilaterally (one side), or bilaterally (both sides). Obviously, the primary benefits diminish as the number of levels increase due to the exposure necessary to address each level.

The basic one-level laminectomy for lateral recess stenosis in the lumbar spine is performed as follows. An approximately 1 inch or less incision is made, overlying the disc space in the skin as determined by an intraoperative x-ray. The fatty tissue beneath the skin is then divided to the dorsal fascia which is the thick tissue overlying the muscle above the spine. This fascia is then incised and the musculature swept to the side, revealing the underlying bone and ligaments. The spinal canal is entered by resection of the ligamentum flavum, which is the ligament connecting between the lamina of each vertebra. The lamina are the flat areas of bone overlying the top of the canal at each level. A portion of the edge of the lamina above and below is resected with the ligaments to allow adequate exposure of the underlying nerve root. Once the canal has been exposed, the nerve root is identified and gently moved to the center of the canal and held with a retractor. Small veins are coagulated to minimize bleeding. The medial edge of the facet joint is removed until the nerve is adequately relieved of any pressure. The foramen can be enlarged by removing the upper portion of the superior facet. When stenosis is also present centrally, the lamina may be removed completely on both sides, including the spinous process, along the area of narrowing. A small piece of fat is usually placed over the surface of the nerve to prevent adhesions. More recently, a number of synthetic materials have been made available which provide this same function. The tissues are then closed in three layers, the muscle fascia, the subcutaneous fat, and the skin. Most frequently the skin is closed under its surface using a subcuticular suture.

Post-Operative Course

Patients are generally maintained at bedrest for several hours following the surgical procedure. They are typically advanced to ambulation on the day of surgery. Patients are usually advanced to a regular diet on a gradual basis and IV fluids are discontinued when they are able to accept liquids. IV antibiotics are usually given pre-operatively and for 24 hours post-operatively. If the patient is independent with ambulation, able to tolerate a regular diet, and afebrile and able to void they are discharged in one to two days for one or two level procedures or in 2-3 days for multiple level procedures. Patients having undergone multiple level lumbar decompressions in our experience have remained in the hospital an average of 2.7% days.

Spinal stenosis is the most common diagnosis requiring multiple level lumbar laminectomies. Given that this condition occurs more frequently in elderly patients, it is not surprising that the average patient age for this procedure is 69 years. This may have an effect on the post-operative hospitalization.

Patients are advised at the time of discharge to avoid activities such as bending, lifting, and vigorous twisting. They are instructed on body mechanics or techniques in sitting, standing, and transferring out of bed, etc. Patients are typically prescribed pain medication to be taken by mouth as needed and occasionally anti-inflammatory medication for residual nerve root swelling and irritation.

Patients are generally advised to refrain from getting the incision wet for three days post-operatively. At that time they may shower. It is generally advisable to avoid submerging the incision in a tub or pool for at least one week.

Follow-up examinations are typically conducted at one week, one month, and three months post-operatively.

At approximately one month post-operatively patients are referred for physical therapy. This includes a graduated course of lower extremity and lumbar flexibility, strengthening, and instructions on body mechanics and postural alignment. Patients are generally advised to increase their recreational and daily activities commensurate with their progress at physical therapy. Benefits Complications

Benefits

Appropriately selected patients, as previously described, can generally expect approximately an 80-90% likelihood of improvement, if not relief, of radicular pain following lumbar decompression. Our surgical procedures have resulted in a success rate of 86% good and excellent outcomes in 215 multiple level procedures.

Although relief of leg pain is common, relief of back pain to the same degree is less predictable. Although the majority, approximately 70-80% of patients can expect improvement or substantial relief of back pain, some patients may experience continued back pain of a substantial degree. This most likely represents degenerative changes unassociated with pressure on a nerve root.

Complications

Operative risks include infection, bleeding, neurological injury, instability, dural tear.

Post-operative infection rates for all surgical procedures performed vary on a national basis between 1 and 2%. We have experienced an infection rate of less .5% with respect to multiple level lumbar decompressive procedures.

Bleeding associated with lumbar decompression is usually minimal. Although the potential exists for greater blood loss in multiple level procedures there have been no cased requiring blood transfusion.

Neurological injury is an unlikely operative complication. The exact incidence of permanent neurological injury is unknown although it is probably on the order of less than 1%. Most frequently, post-operative neurological deficits were present pre-operatively. Occasionally, transient weakness or sensory change may be noted post-operatively due to traction, compression, or swelling of affected nerve roots. These conditions are typically temporary and usually resolve in a matter of days or weeks. Transient paraparesis (weakness of lower extremities) developed in one case post-operatively and gradually recovered.

10 patients (4.7%) have undergone re-operation for problems related to the initial procedure. Five of these patients (2.3%) required fusion including instability in four and as a result of infection in one. Four patients (1.9%) required repeat decompression for persistent symptoms following their initial procedure. One patient (.5%) underwent re-exploration and repair of a persistent CSF leakage following a dural tear during the initial procedure.

Eight patients (3.7%) required subsequent decompression procedures for new onset symptoms at other levels after successful initial treatment.