laminectomy spine surgery
What is a laminectomy surgery?
A laminectomy is a surgery in which portions of the vertebra forming the sides and/or roof of the spinal canal (including the dorsal spinous process, lamina, articular facets, and/or pedicles) are removed to expose the spinal canal, enabling the removal of ruptured disc material, tumors, abscesses, blood clots, and anything else impinging on the spinal cord.
There are several different types of laminectomies that can be performed depending on the size and location of the pathology to be exposed. If the problem is located in the top portion of the spinal canal, above the spinal cord, a procedure that removes portions of the “roof” of the spinal canal is selected. Types of laminectomies that target this area include the dorsal laminectomy, Funkquist A dorsal laminectomy, Funkquist B dorsal laminectomy, and deep dorsal laminectomy. If one side of the spinal canal or the bottom of the canal needs to be accessed, a hemilaminectomy or pediculectomy is performed, creating a window in the side of the vertebra.
To perform these surgeries, the surgeon first makes an incision along the spine over the affected portion of the spinal cord. The back muscles are retracted away from the vertebrae to be accessed. Specialized drills are then used to carefully burr away the bone, exposing the spinal canal. The material compressing the spinal cord is then delicately removed. A fat graft is often placed into the bone “window” that has been created, in order to prevent scar tissue from attaching to the spinal cord. The muscles are then released back into their normal positions, and the incision is closed.
What conditions are treated with a laminectomy?
A variety of conditions causing compression of the spinal cord can be treated with a laminectomy. The most common condition for which a laminectomy is performed is intervertebral disc disease. This disease involves the core of an intervertebral disc extruding into the spinal canal, or the edge of a disc thickening and protruding into the canal. These conditions are most commonly treated with a hemilaminectomy, allowing exposure of the side of the spinal canal for removal of the displaced disc material. A condition called lumbosacral stenosis, in which the spinal canal becomes abnormally narrow in the low back due to thickening of the surrounding vertebrae and ligaments (presumably in response to joint instability) is frequently treated with a dorsal laminectomy combined with distraction and stabilization of the joint space. In many cases, a blood clot or abscess that has formed adjacent to the spinal cord can also be removed with a laminectomy. Finally, some tumors growing around the spinal cord can be removed using a laminectomy.
What symptoms are associated with these conditions?
Most conditions requiring a laminectomy are associated with pain at the site of compression. Depending on the severity of the compression, neurologic signs such as weakness, ataxia (incoordination), abnormal reflexes, paralysis, incontinence, and loss of the ability to feel can be seen below the site of compression. If compression is in the neck, all four limbs are usually affected, while if the compression is in the back, usually only the hind limbs are affected. If one side of the spinal cord is more compressed than the other, the signs may be more severe on one side of the body. Signs can develop gradually or suddenly, depending on the specific disease process.
How are conditions requiring a Laminectomy diagnosed?
The first step in diagnosing a compressive disease of the spine is a thorough physical and neurologic exam. During this exam, in addition to evaluating all other body systems, the veterinarian will carefully palpate each vertebra from head to tail to check for signs of pain, muscle tension, and muscle spasms. Several different maneuvers will be utilized to assess each limb for the presence of normal responses to changes in balance and body position. Spinal reflexes will also be tested in each limb. If the patient is able to walk, their gait will be observed. If they are paralyzed, their ability to feel pain in the affected limbs will be tested. Finally, anal and bladder tone will be evaluated.
If the physical exam is consistent with spinal cord compression, sedated x-rays of the vertebral column will be taken. These are used to look for vertebral abnormalities that may be causing the signs, such as a fracture or joint dislocation, an infection of the bone, or a bone tumor. Because the intervertebral discs cannot be seen on standard x-rays, these cannot be used to definitively diagnose intervertebral disc disease, although sometimes changes such as an abnormally narrow disc space and calcified disc material can be suggestive of this condition.
If spinal x-rays do not reveal a diagnosis, a CT scan or MRI is performed to allow for detailed evaluation of the spinal cord, intervertebral discs, and the surrounding soft tissues. These scans require a patient to be under general anesthesia or heavy sedation, as they must remain very still for the duration of the scan.
What post-operative care is required following a laminectomy?
Following a laminectomy, all patients are hospitalized on IV fluids to maintain hydration and injectable medications for pain and inflammation. They are kept on thick bedding, and if unable to stand up and move around on their own, they are repositioned frequently to prevent pressure sores and lung compression. If bladder control is absent, a urinary catheter or gentle manual pressure is used to empty their bladder on a regular schedule. Patients are bathed as frequently as necessary to keep them clean and prevent skin irritation from developing. Once a patient is eating and drinking on their own and is comfortable on oral medications, they can be sent home. This may take as little as 24 hours, or as much as a week. Disc-related pain is typically significantly improved within 24 hours of surgery, and neurologic deficits often begin to improve within three to five days. Maximal recovery of nerve function can take anywhere from a couple of weeks to several months, and generally relates to the duration of symptoms before surgery.
At home, patients who are able to walk must be confined to strictly limit their physical activity while they heal. Only short, slow leash walks are permitted for the first few weeks after surgery, and they must be prevented from jumping, playing, or stair use. Slick surfaces should also be avoided.
Patients who are not able to get up and move about on their own, as well as those that do not have complete bladder or bowel control, require more intensive care at home. This includes deep bedding that is kept clean and dry at all times, frequent repositioning to avoid pressure sores, and the use of sling support when taking them outside to use the bathroom. If a patient is not able to empty their bladder on their own, the owner is taught how to catheterize or manually express their bladder. Patients who are incontinent will need to be checked frequently for any urine or feces that might be on their hind end, and cleaned with warm water and a gentle cleanser whenever soiling is present.
The first follow-up appointment is typically scheduled for two to three weeks after surgery. At this appointment, the progress of healing and restoration of function will be assessed, and the stitches will be removed. Based on the patient’s progress, the veterinarian will determine if an increased level of physical activity can be introduced. For patients who have not yet recovered normal nerve function, a physical rehabilitation program will be implemented to facilitate neurologic recovery. Further recheck appointments are scheduled once a month until maximal neurologic improvement is achieved.
What are the possible risks and complications of a laminectomy?
Several complications can occur during or following a laminectomy. Because of the close proximity of the spinal cord and spinal nerves to the tissues that must be manipulated during surgery, there is a risk of temporary or permanent damage to these structures. If the large blood vessels located within the spinal canal are disrupted during surgery, significant hemorrhage may result. While this hemorrhage is rarely life-threatening, it often necessitates halting the procedure, closing the surgical site, waking the patient up, and waiting a day or two before attempting a second surgery to finish the procedure. Magnification, specialized instruments, and very careful and precise surgical technique help to minimize these risks.
In the immediate post-operative period, in addition to the potential for a surgical site infection, patients with significant neurologic deficits are at increased risk of developing pneumonia, urinary tract infections, and skin infections. These risks are minimized by providing intensive nursing care to patients who are immobile and/or incontinent.
What is the prognosis following a laminectomy?
The prognosis following a laminectomy depends on the disease being treated, the severity and duration of spinal cord compression, and the severity of the neurologic deficits present before surgery.
Patients undergoing a hemilaminectomy for Type I IVDD (disc extrusion) that was causing only pain and mild neurologic deficits have a greater than 95% chance of return to normal function. Those who have Type I IVDD that is causing significant neurologic dysfunction (inability to walk, incontinence) but who are able to feel their affected limbs, have a 90% chance of returning to normal or near-normal function following a hemilaminectomy. Individuals who are unable to feel pain in their affected limbs have a much more guarded prognosis, with less than a 50% chance of recovery with a hemilaminectomy. This worsens to less than 10% if pain sensation has been absent for more than 24 hours. In a small fraction of the most severely affected individuals, a process called spinal cord myelomalacia occurs, resulting in the death of nerve cells in the spinal cord at the site of the initial contusion. This process is irreversible, may not become evident until after surgery has already been performed, and may progress up and down the spinal cord. Patients diagnosed with this condition have no hope of recovery, and are at a high risk of dying from respiratory paralysis; for this reason, euthanasia is recommended in cases of myelomalacia. It is also important to keep in mind that an individual who has experienced a disc extrusion is at an elevated risk of having another disc extrusion in the future. Avoiding jumping, stairs, and vigorous play indefinitely can delay the extrusion of other degenerating discs.
Patients undergoing a hemilaminectomy for Type II IVDD (disc protrusion) have a 22% chance of regaining normal or near-normal function with surgery. Many patients do experience partial improvement and can have a good quality of life with special support devices to aid in mobility.
Patients undergoing a dorsal laminectomy (with or without distraction and stabilization of the joint space) for LS stenosis who have minimal neurologic deficits have a 70-80% chance of improvement. Patients with severe neurologic abnormalities, urinary incontinence, and/or fecal incontinence, have a much more guarded prognosis following surgery; they typically do not recover bladder and/or bowel control, although surgery may still be effective in improving comfort.
When a laminectomy is performed to remove a tumor within the spinal canal, the prognosis depends on the condition of the spinal cord and nerve roots, whether the tumor can be completely removed, and what cell type makes up the mass. The prognosis with other causes of spinal cord compression, such as blood clots and abscesses, varies depending on the severity, duration, and underlying cause of the abnormality.
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