Minimally Invasive Spine Surgery
Minimally invasive outpatient lumbar (low back) and cervical (neck) spine surgery is performed to relieve pain, restore neurological function, and improve the quality of life in patients with signs and symptoms of a “pinched nerve” or pressure on the spinal cord.
Outpatient lumbar spine surgery is most commonly performed for a “herniated” (displaced) disc or from spinal stenosis (overgrowth of bone and ligament).
Lumbar Disc Disease
Lumbar disc is a cartilaginous material (like crab meat but hundreds of times stronger) located in between the vertebral bodies (blocks of bone) in the front of the spine. They are not “jelly” and do not “ooze or squirt” in and out. The center of the disc is the nucleus pulposus which contains numerous circular rings of cartilaginous material and is contained by a strong fibrous covering called the annulus. The discs contribute to the strength, cushioning, and movement of the spine. Most commonly, degenerative (“wear and tear”) changes and less commonly a single traumatic event results in the disc being displaced or “herniated” causing pressure on a nerve root or multiple nerve roots. This can cause gradual or sudden onset of buttock and leg pain, weakness, and/or numbness. The symptoms are usually worse sitting, bending, or walking, and better lying down. The disc herniation will cause leg symptoms in a specific distribution depending on which nerve is being compressed. A lumbar MRI scan is the preferred imaging study. Surgery is performed for intolerable leg symptoms, not low back pain, which have not improved despite several weeks of medical management such as medications, injections, and physical therapy. Surgery may be performed earlier if there is significant weakness or the pain is incapacitating.
A lumbar microdiscectomy is an outpatient procedure safely performed in an ambulatory care center in patients who are generally healthy. Patients who are elderly or who have major medical problems can still have surgery performed as an outpatient, but it is usually performed in a hospital setting. The surgery is performed with the patient lying prone (on their abdomen) under general anesthesia for 1-2 hours. A 1-2 inch vertical incision (depends on the size of the patient) is made in the middle of the low back. The muscles running vertically parallel to spinous processes (the bones protruding in the middle of the back from the neck to the low back) on the side of the symptoms are reflected from the spinous processes. A tubular/speculum retractor is used to minimize tissue disruption (shorter incision and less postoperative pain) and provide superior exposure. The operating microscope (“microdiscectomy”) is used to provide outstanding visualization through a small incision due to its superb lighting and magnification. This makes the procedure safer and more precise. After removing a small amount of the lamina and ligamentum flavum (the bone and ligament in the back spine which surround and protect the nerves), the disc material pressing on the nerve is removed. In some cases, fragments of disc which have migrated from the disc space are all that need to be removed. More commonly, the herniated disc pressing on the nerve is in continuity with the disc space, so approximately 20% of the disc within the disc space is removed in order to reduce the chance of recurrence. Resorbable sutures are used and a waterproof sealant is placed on the incision. Patients are discharged 1-2 hours after surgery.
Lumbar stenosis, or narrowing of the spinal canal, is due to hypertrophy (overgrowth) of bone and ligament in the back of the lumbar spine. This occurs over many years of “wear and tear” and most commonly causes symptoms in those over 50 years old. A herniated disc can also contribute to spinal stenosis. Lower extremity pain, weakness, heaviness, numbness, and/or tingling which increases with walking, standing, or bending backwards and which decreases sitting, lying, bending forward, or squatting are characteristic. The natural history of lumbar spinal stenosis is one of gradual worsening, although the rate and extent of the worsening varies. A lumbar MRI scan is the preferred imaging study. Surgery is performed for intolerable leg symptoms, not low back pain, which have usually been present for several months or years.
Lumbar Stenosis Surgery
Lumbar decompression for spinal stenosis is performed on one or both sides of the spine depending on whether one or both legs are involved. The surgical procedure is the same as the lumbar microdiscectomy, except the main cause of the narrowing of the spinal canal is overgrown bone (facet joint and lamina) and ligament (ligamentum flavum). Usually, only the bone (“partial hemilaminectomy” or “laminotomy”) that is pressing on the nerves is removed rather than all the bone (“laminectomy”) in order to preserve stability of the spine. This surgery varies from 1-4 hours depending on whether it is performed on one side, both sides, or at one or multiple levels.
Outpatient cervical spine surgery is most commonly performed for a “pinched nerve” due to an acute (recent) or chronic (long standing) herniated disc or osteophyte (bone spur) and less commonly for pressure on the spinal cord.
Cervical Disc Disease
Disc in the cervical spine is similar to that in the lumbar spine, except the disc is much smaller in diameter. A “pinched nerve” in the neck causes pain in the shoulder blade, arm, and hand, including the fingers, depending on which nerve is involved. This can be associated with numbness, tingling, and/or weakness. Similar to the lumbar spine, this usually occurs from degenerative (“wear and tear”) changes and less commonly to a single traumatic event. The symptoms are usually better or worse depending on neck position. Surgery is performed if the arm symptoms, not neck pain, are intolerable, despite several weeks of medical management such as medication and physical therapy. Surgery can be performed earlier if there is significant weakness or incapacitating pain.
Cervical Spinal Stenosis
Disc or bone pressing on the spinal cord typically causes bilateral upper and lower extremity weakness and sensory changes with reduced coordination and difficulty with gait. These symptoms usually develop gradually but can arise suddenly. There is usually no associated pain. A cervical MRI scan is the preferred imaging study. The threshold for performing surgery for symptomatic spinal cord compression is much lower than for a “pinched nerve”, since successful reversal of spinal cord symptoms tends to decrease the longer the symptoms have been present.
Cervical Spine Surgery
Cervical spine surgery is safely performed in an outpatient ambulatory care center in patients who are generally healthy. Patients who are elderly or who have major medical problems can still have surgery performed as an outpatient, but it is usually performed on a hospital setting.
Anterior cervical discectomy with allograft fusion and plating is the most common surgical procedure performed for cervical disc disease. This takes 1-4 hours depending on how many disc segments are treated. Cervical disc is anterior (in front) of the spinal cord and nerve roots, so approaching these from the front of the neck is more direct with access to nerve roots on both sides. The posterior (back of the neck) approach involves removing normal bone (lamina) and provides limited access to disc and bone spurs since they are underneath the spinal cord and nerve roots which cannot be retracted or moved. It is also not preferred if the cervical spine has a reverse curve. It is recommended if the main cause of nerve root or spinal cord compression is from abnormalities in the back of the spine, not from disc, or if the number of levels or anatomy precludes the anterior approach.
With the anterior approach, an approximately 1.5 inch horizontal incision is made in the front of the neck. Dissection then proceeds in between important structures. Using special retractors and the operating microscope, almost all the disc in the disc space, including the disc and/or bone pressing on the nerves and/or spinal cord, is removed. A bone graft or “spacer” is then placed in the disc space in order to maintain the curvature of the spine, preserve the disc space height, and reduce abnormal movement thereby reducing neck pain. The most common spacer is allograft (donor bone). Titanium cages, synthetic grafts (PEEK), or autograft (patient’s own bone harvested from the iliac crest/”hip bone”) can also be used. A titanium cervical plate spanning the bone graft is placed in the front of the spine and anchored with screws in the vertebral bodies (square blocks of bone above and below the disc) immobilizing the segment and securing the graft to facilitate successful fusion. Resorbable sutures are used with a waterproof sealant on the skin. The patient is discharged 1-2 hours following surgery.