Spondylolisthesis

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Spondylolisthesis

What Is Spondylolisthesis?

The spine is made up of 33 bones called vertebrae and divided into four regions: cervical (neck), thoracic (mid back), lumbar (lower back), and sacrum. Spondylolisthesis refers to the improper positioning of a vertebra and occurs in two ways: anterolisthesis, in which the vertebral body is positioned forward in relation to the vertebra it sits above, and retrolisthesis, in which the vertebral body is positioned backward from the vertebra it is positioned above. Spondylolisthesis can be either dynamic, fixed, or glacial. Fixed spondylolisthesis indicates misalignment of one vertebral body on top of another, but that this structure does not move during motion of the spine, such as bending forward. Dynamic spondylolisthesis refers to a misaligned vertebral segment that moves when the spine moves, during flexion and extension (bending forward and bending backward). Dynamic Spondylothesis may mask misalignment because the vertebrae may seem aligned in either the flexion or the extension positions. Glacial spondylolisthesis refers to an increasing misalignment over time. Spondylolisthesis is given a grade based on its severity; the grade is determined by the distance that the vertebral body is misaligned.

There are multiple types of spondylolisthesis including isthmic, degenerative, and iatrogenic. Isthmic spondylolisthesis means that there is a defect or fracture in the area of the vertebrae that makes up the facet joints, called the pars interarticularis. This usually occurs during childhood due to stress on the spine as the part interarticularis has a poor blood supply and therefore does not heal well. The symptoms don’t manifest till adulthood so it is commonly undiagnosed until that time. Degenerative spondylolisthesis refers to degeneration of the disc, joints, and ligaments of the spinal column due to aging and wear and tear. As these parts of the spine weaken, their ability to hold the spine in alignment diminishes and may result in the slip of a vertebra. The term iatrogenic refers to any medical treatment that directly results in a complication. Iatrogenic spondylolisthesis commonly occurs as a complication or result of spine surgery.

Types Overview

Spondylolisthesis is a malalignment of the vertebrae in which one vertebra slips forwards or backwards over the vertebra below it. There are six different types of spondylolisthesis: traumatic, iatrogenic, congenital, degenerative, pathologic, and isthmic. This type of structural abnormality of the spine can be found in all regions (i.e. cervical, thoracic, and lumbar), but most frequently occurs in the lumbar spine.

Type I: Congenital/Dysplastic

Congenital spondylolisthesis, also known as dysplastic spondylolisthesis, is an abnormality present at birth. The slip in this type of spondylolisthesis is a defect in the facet joints which connect spinal vertebrae. This occurs in the lower joints at L5 (inferior joint), the upper joints at S1 (superior joints), or at both joints and cause a gradual slip of the L5 vertebrae over time. This type of spondylolisthesis is rare compared to the other types.

 

Type II: Isthmic

Isthmic spondylolisthesis is the most common type of spondylolisthesis and is divided into three separate subtypes, but all have a defect at the same location in the spine. In isthmic spondylolisthesis there is a defect, typically a fracture, of the pars interarticularis, the bone that connects the upper and lower facet joints. This fracture prevents the affected vertebra from staying in line with the other vertebrae, allowing it to slide forward. The L5-S1 level is most frequently affected by isthmic spondylolisthesis.

Type III: Degenerative

Degenerative spondylolisthesis is a slip from arthritis within the spine. Degenerative changes or arthritis is common in aging individuals. Once the joints in the spine begin to wear, they have difficulty keeping the spine in line and a vertebra slips forward. This occurs most frequently in the lumbar spine, but can happen in the cervical spine as well.

Type IV: Traumatic

Traumatic spondylolisthesis is a slip due to an event that places a large amount of force on the spine. This high force results in damage to the neural arch, which is the ring of bone that surrounds the spinal cord. The fracture of the neural arch causes a sliding forward of the vertebrae. Both the cervical and lumbar spine may be affected, but this is an uncommon type of spondylolisthesis.

 

Type V: Pathologic

Pathologic spondylolisthesis is a slip from weakness within the bones, such as tumors, types of cancers, and bone disease. This weakening causes destruction of the posterior (backside) portion of the vertebrae, such as the neural arch, which surrounds the spinal cord. Just like the traumatic type, pathologic spondylolisthesis is a rare type. 

Type VI: Iatrogenic

Iatrogenic spondylolisthesis is a slip caused directly from a prior spine surgery that involved decompression of the spine without stabilization. During decompression procedure a small amount of bone is removed to release pressure on the spinal cord and/or the nerves that branch off. The removal of too much bone during this procedure can cause the vertebral body to slip. In general, this is avoided using a stabilization surgery when a large portion of bone needs to be removed.

Causes Overview

Spondylolisthesis is typed by the cause. There are six different major causes for a vertebral slip; depending on the cause, the slip will occur in different regions of the spine.

Type I: Congenital/Dysplastic

Congenital spondylolisthesis, also known as dysplastic spondylolisthesis, is an abnormality present at birth. The slip in this type of spondylolisthesis is a defect in the facet joints which connect spinal vertebrae. This occurs in the lower joints at L5 (inferior joint), the upper joints at S1 (superior joints), or at both joints and cause a gradual slip of the L5 vertebrae over time. This type of spondylolisthesis is rare compared to the other types.

Type II: Isthmic

Isthmic spondylolisthesis is the most common type of spondylolisthesis and is divided into three separate subtypes, but all have a defect at the same location in the spine. In isthmic spondylolisthesis there is a defect, typically a fracture, of the pars interarticularis, the bone that connects the upper and lower facet joints. This fracture prevents the affected vertebra from staying in line with the other vertebrae, allowing it to slide forward. The L5-S1 level is most frequently affected by isthmic spondylolisthesis.

Type III: Degenerative

Degenerative spondylolisthesis is a slip from arthritis within the spine. Degenerative changes or arthritis is common in aging individuals. Once the joints in the spine begin to wear, they have difficulty keeping the spine in line and a vertebra slips forward. This occurs most frequently in the lumbar spine, but can happen in the cervical spine as well.

Type IV: Traumatic

Traumatic spondylolisthesis is a slip due to an event that places a large amount of force on the spine. This high force results in damage to the neural arch, which is the ring of bone that surrounds the spinal cord. The fracture of the neural arch causes a sliding forward of the vertebrae. Both the cervical and lumbar spine may be affected, but this is an uncommon type of spondylolisthesis.

Type V: Pathologic

Pathologic spondylolisthesis is a slip from weakness within the bones, such as tumors, types of cancers, and bone disease. This weakening causes destruction of the posterior (backside) portion of the vertebrae, such as the neural arch, which surrounds the spinal cord. Just like the traumatic type, pathologic spondylolisthesis is a rare type.  

Type VI: Iatrogenic

Iatrogenic spondylolisthesis is a slip caused directly from a prior spine surgery that involved decompression of the spine without stabilization. During decompression procedure a small amount of bone is removed to release pressure on the spinal cord and/or the nerves that branch off. The removal of too much bone during this procedure can cause the vertebral body to slip. In general, this is avoided using a stabilization surgery when a large portion of bone needs to be removed.

Symptoms Overview

The symptoms of spondylolisthesis can range from non-existent to debilitating. The condition may be found incidentally, meaning that the physician was performing a general checkup or looking for something different when the malalignment of the spine was discovered. The symptoms are related to the motion created by the vertebral slip and are often similar regardless of cause. Although spondylolisthesis may occur at any level in the spine, the lumbar region tends to be affected more often than the cervical or thoracic spine except in for cases of traumatic spondylolisthesis which is found in the cervical spine most often.

Type I: Congenital/Dysplastic

Symptoms of congenital spondylolisthesis is often not found till later in life, typically till around the time of a growth spurt in adolescence. Low back pain that worsens with activity is the most common complaint, particularly pain that increases with activities that involve extension of the lumbar spine and decreases with rest. Since this type of spondylolisthesis affects the L5-S1 level, radicular symptoms appear in both legs, radiating along the length of the L5 nerve:  into the buttocks and down the back of the thigh. With more severe slips the pain may radiate farther down the leg into the foot, especially on the side with the big toe. Certain neurologic symptoms may be present as well, such as changes in reflexes or weakness, particularly with pulling toes up toward the face or moving toes up when walking. If impingement is severe at this level, this may lead to the foot “slapping” the ground when walking. The symptoms may be progress rapidly compared with other types of spondylolisthesis.

Type II: Isthmic

The symptoms of isthmic spondylolisthesis may be diagnosed during adolescence, around the time of a large growth spurt, or may not be identified until adulthood. Low back pain that worsens with activity is the most common complaint, particularly pain that increases with activities that involve extension of the lumbar spine and decreases with rest. Since this type of spondylolisthesis affects the L5-S1 level, radicular symptoms appear in both legs, radiating along the length of the L5 nerve:  into the buttocks and down the back of the thigh. With more severe slips the pain may radiate farther down the leg into the foot, especially on the side with the big toe. Certain neurologic symptoms may be present as well, such as changes in reflexes or weakness, particularly with pulling toes up toward the face or moving toes up when walking. If impingement is severe at this level, this may lead to the foot “slapping” the ground when walking. Other symptoms include tightness in the hamstring muscles, the group on the back of the thigh. There may also be changes in gait, such as taking smaller steps or walking with a waddle.  

Type III: Degenerative

Symptoms of degenerative spondylolisthesis tend to start gradually and progress over time. Lower back pain that radiates into the buttocks and the back of the thigh is the most common symptom. Neurogenic claudication, pain with standing and walking, is also a typical symptom. The claudication is generally relieved with rest and may be relieved further with flexion of the lumbar spine (bending forward). Many patients with degenerative spondylolisthesis have other lumbar comorbidities such as spinal stenosis which may cause other symptoms to occur simultaneously with the symptoms of the spondylolisthesis.

Type IV: Traumatic

Application of a large force may lead to traumatic spondylolisthesis; this usually presents after an acute injury, such as a fall or motor vehicle accident. This type of spondylolisthesis is typically accompanied by severe pain associated in the neck or the back since traumatic spondylolisthesis most often affects the cervical spine. Often the amount of pain and injury from trauma limit the range of motion within the spine. Based on which vertebrae are affected, there will be pain or weakness that radiates into both sides of the body at the areas corresponding to the nerves at that vertebrae. If this occurs in the lumbar spine, this may cause compression on the cauda equina, the nerve roots at the end of spinal cord. Acute compression of these nerve roots can cause dysfunction of the bladder, bowel, numbness in the genital region, and pain.

Type V: Pathologic

Pathologic spondylolisthesis is cause by an underlying medical condition that causes weakness within the bones. The symptoms are usually gradual and include localized neck pain or low back pain. The pain may include radicular symptoms, such as pain that radiates into the arms or legs, and usually occurs on both sides of the body.

Type VI: Iatrogenic

Iatrogenic spondylolisthesis may not create any symptoms, but can also cause low back or neck pain, despite having a prior decompression. The symptoms may radiate into the arms and legs depending on how far the vertebra slides.

Diagnosis Overview

Patient history and physical examination are typically the first step in diagnosing spondylolisthesis. Types of symptoms, duration of symptoms, factors that improve/exacerbate symptoms, treatments that have been already tried, and past relevant medical problems/surgeries are all collected during the history. The physician completes a physical exam to check for specific symptoms by inspecting the back, assessing gait, and testing the upper and lower extremities for motor strength, reflexes, and range of motion.

Both history and physical exam contribute to a diagnosis of spondylolisthesis, but imaging is necessary to finalize the diagnosis. X-rays are typically obtained first to look at the overall alignment of the spine; for cases of spondylolisthesis, one vertebra will have slid either forward (anterolisthesis) or backward (retrolisthesis) from the other vertebrae. It is important that the x-rays are performed standing, as gravity can change the alignment of the spine and spondylolisthesis may not be visible if the spine is in a relaxed, laying down position. Oblique views of the spine (left and right side) are also obtained to better visualize the pars interarticularis, the bone that connects the upper and lower facet joints. The oblique views may show a break or fracture in the pars interarticularis, leading to a diagnosis of isthmic spondylolisthesis. In addition, specialized x-rays are taken with the spine in both flexion and extension, bending to touch the toes and leaning back respectively. These views determine if the vertebra moves with motion in the spine, which is called a dynamic spondylolisthesis. A fixed spondylolisthesis refers to a slip that stays the same whether the spine is in a flexed or extended position.

Advanced 3D imaging may be used to determine the type of spondylolisthesis, as this is not always evident on x-ray imaging. MRI scans show soft tissues better and are used to determine the amount of compression on the spinal cord and nerve roots, and to evaluate the amount of inflammation in the facet joints, damage to the intervertebral disc, inflammation in the bone, and any underlying bone conditions, such as metastatic cancer or tumors. CT scans show bony elements better and may show the disruption of the neural arch from a traumatic spondylolisthesis, evaluate the defect of the pars interarticularis in isthmic spondylolisthesis, assess the joint formation in congenital spondylolisthesis, or evaluate the extent of arthritic damage in degenerative spondylolisthesis. Together history, physical exam, and imaging are all necessary in order to make a correct diagnosis and design an optimal treatment plan for a spondylolisthesis.

Treatment Overview

Once spondylolisthesis is diagnosed through history, physical exam, and imaging studies, a treatment plan is created. Treatment generally begins with addressing symptoms through conservative, non-invasive options and may include a combination of options. These options include alternative therapy, medication, physical therapy, injections, and lifestyle modifications.

The majority of patients with a spondylolisthesis will be able to improve their condition or control the symptoms using conservative treatment options. Surgical options will be considered depending on the cause, severity, and presence of neurologic symptoms, such as sensation changes, drop foot, muscle wasting, or weakness in a specific muscle group. Traditional surgical options use a large incision with tissue and muscle disruption, but there are several minimally invasive surgical options that may be more appropriate for addressing a spondylolisthesis. Minimally invasive surgeries are performed through a small incision with minimal disruption of the surrounding muscles and tissues allowing for faster healing and return to normal activities. The location, grade, and underlying cause of the spondylolisthesis will all help to determine which surgical procedure is best for treatment. As there is an abnormal motion in the spine with spondylolisthesis, all procedures will be aiming to fix the slip or create stability.

Conservative Options

Bracing

Bracing is a mainstay for therapy, especially in isthmic and traumatic spondylolisthesis. Bracing keeps the spine stable and prevents motion. A rigid brace is typically used and is sized to target the specific vertebra with the spondylolisthesis. Bracing is typically needed only during the day and may be removed at night. Several factors may influence how long the brace is needed, but a typical time frame is 6-12 weeks.

Lifestyle Modifications

Certain lifestyle factors may worsen the symptoms from a spondylolisthesis, such as increased weight and repetitive tasks. Added weight may increase symptoms due to the change in the center of gravity, which may worsen the slip. Reducing weight through a low-calorie diet and exercise can reduce pressure on the spine, decreasing the symptoms of a spondylolisthesis.

Repetitive leisure or work-related motions such as excessive bending, lifting, and twisting, along with any activity that may be high impact on the spine, such as running or riding ATVs, can also increase the symptoms of a spondylolisthesis. Some of these repetitive task activities may be due to leisure and others due to demands of a job. For people with full labor or heavy-duty jobs, you may need to change jobs or support your work with proper lifting technique, relaxed breaks, and equipment such as a back brace to avoid worsening symptoms. You may also need to alter or avoid high impact activities, such as running to reduce the symptoms and potential to worsen spondylolisthesis.

Physical Therapy/Exercise

Physical therapy focuses on changing body mechanics to improve posture and walking as well as to strengthen and retrain muscles, particularly those in the core. The initial step is meeting with a Physical Therapist for a consultation to assess posture, gait, and muscle weakness and to design a personalized exercise program. Other techniques that physical therapists may use are manual treatments such as massage, ultrasound, and electro-stimulation through a TENS (transcutaneous electrical nerve stimulation) unit. A combination of these methods can provide symptom relief.

A home exercise program may be used in conjunction with or instead of a formal physical therapy regimen. A daily low impact exercise regimen is important for strengthening muscles, especially those in the core. Low impact cardiovascular activities such as walking, swimming, elliptical, and biking are also important for increasing blood flow and strengthening muscles without adding stress on the spine. Home exercise can also lead to weight loss which may reduce pressure on the spine and reduce symptoms. Home exercise routines should be paired with stretches and physician supervision to avoid harm.

Medications

There are multiple types of prescribed and over the counter medications that may be used to treat the symptoms of spondylolisthesis. Some of these medications include Tylenol (acetaminophen), NSAIDs (nonsteroidal anti-inflammatory drugs), muscle relaxants, nerve membrane stabilizers, topical medications, and off label medications.

Common over the counter medications are acetaminophen and NSAIDs. Acetaminophen is considered an analgesic, meaning it relieves pain but does not reduce inflammation. NSAIDs are effective at both relieving pain and reducing inflammation; they can be found in brand and generic forms over the counter. These medications are best taken with food to avoid an upset stomach. They can be taken for longer durations, as long as there is no history of kidney disease. The mechanism of both NSAIDs and Acetaminophen differ, so they are taken together often to combat pain.

Muscle relaxants are used to provide relief from muscle spasms and increase range of motion; they are best used in combination with physical therapy or an exercise/stretching regimen. Drowsiness is a common side effect of muscle relaxants and they are not recommended while driving or working. Common muscle relaxants include Flexeril, Soma, Baclofen, Robaxin, and Tizanidine.

Nerve membrane stabilizers are another class of medications often used to treat the numbness, tingling, shooting, stabbing, or radiating pain associated with spondylolisthesis. Gabapentin (Neurontin) and Lyrica (Pregabalin) are commonly prescribed nerve membrane stabilizers and work by reducing pain signals released by nerves. Both medications, Gabapentin especially, can be taken in higher dosages multiple times per day, but this class of medication may cause dizziness and drowsiness. Nerve membrane stabilizers are typically started on a low and infrequent dose; the dosage is gradually increased until the pain is controlled and then gradually decreased prior to discontinuation.

There are other medications that may be used ‘off-label,’ meaning not for the use listed on the label. Some common medications used off label for pain are anti-depressants, such as Cymbalta and Amitriptyline. Similar to the nerve membrane stabilizers, these medications are slowly increased in dosage and they also target nerve-type pain, such as burning, numbness, and tingling associated with nerve pain. They may also cause drowsiness and are usually used at night for pain control.

Epidural Steroid Injections

Epidural steroid injections reduce pain by injecting steroid, or anti-inflammatory, medication at a specific level/levels in the spine. As the herniation places pressure on a nerve, this causes inflammation of the nerve and surrounding tissue which causes pain. A specialized needle is used to deliver medication to the correct area, past the muscles of the back and as close to the spinal nerves as possible. As steroids are a natural anti-inflammatory, this may reduce the inflammation around the nerve, diminishing pain caused by the disc herniation. Steroid injections have the ability to provide pain relief for up to several months, and provide better pain relief for radiating symptoms, such as leg pain, than treatments designed for back pain alone. Steroid injections are only safe to have completed 3 times in one year and must be at least one month apart between sequential injections. This is due to the muscle and tendon breakdown with exposure to the steroid medication too often or too soon.

Surgical Options

Cervical

An ACDF is a minimally invasive surgical stabilization procedure. This is performed through a small incision on the front of the neck. The surgeon tunnels between the thin neck muscles until the spinal column is reached. The old disc is removed and bone spurs or disc fragments around the nerve roots are removed to take pressure off the nerves. A special implant with bone graft will then be placed in the disc space with screws to secure placement, which may reduce or fix the slip of the vertebra. Once the procedure is completed, the disc level is fused.

 Lumbar

 A transverse lumbar interbody fusion (TLIF) is a minimally invasive stabilization procedure that uses a specialized implant to fix the appropriate disc level. This procedure is performed through a small incision on the midline of the lumbar spine. Once the spine is reached, the backside portion of the vertebrae is removed, the laminae, until the nerve is reached and the compression on the nerve is removed. The disc material is removed from the disc space and a special implant with bone graft is placed into the disc space with screws placed into the vertebral body above and below the disc space, that are connected via rods. This implant with screws may reduce the slip and prevents any further motion once fused. Once the procedure is complete the spinal level is fused.

 An extreme lateral lumbar interbody fusion, or XLIF, is a minimally invasive surgery that is performed on the lumbar spine. A small incision is made on the left side, between the hip and the ribs. A thin wire, called a guide wire, is placed and sequentially cylindrical tubes, called dilators are placed through the psoas muscle to reach the left side of the spine. Once the spine is reached, the disc is then completely removed. A special implant is sized, filled with bone graft and placed in the empty disc space. The implant is then screwed in place, with screws placed into the upper and lower vertebral body to provide structure. This will fuse and stabilize the level to prevent any further motion. The XLIF can only be performed on certain levels in the lumbar spine, as the space between the hip and lowest rib is limited, even with specialized positioning of the body on the surgical table.

All procedures to address spondylolisthesis are minimally invasive stabilization procedures, they fix the slipped vertebrae in place via a fusion. The spinal cord and spinal nerve roots are decompressed properly and the mal-aligned vertebral body is stabilized to prevent further motion. Multiple factors are taken into consideration in order to plan an appropriate surgical option to treat the symptoms and structural abnormality of a spondylolisthesis.

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