Spondylolisthesis is the displacement of one vertebra on top of another. This displacement can occur when there is significant acute damage to the area, from a contact sports injury say, or as a result of more chronic issues such as cervical degenerative disc disease, osteoarthritis, and other cervical spinal issues. Unchecked, degenerative spondylolisthesis can lead to cervical spinal stenosis (Kalichman, 2008).
Physicians usually classify spondylolisthesis according to its cause, with the most common being degenerative spondylolisthesis. This is caused by chronic degenerative changes in the ligaments, facet joints, bones, and cartilage that hold the spinal/vertebral column in position. This degeneration can lead to spondylolisthesis as the vertebral column loses its ability to stay together and the vertebrae slip out of position. Isthmic spondylolisthesis is the result of spondylolysis; a defect in the pars interarticularis (part of the vertebrae) most commonly caused by repetitive microtrauma in childhood through activities such as gymnastics, diving, soccer, football, and wrestling (Standaert, 2000).
Traumatic spondylolisthesis is due to direct trauma inflicted upon the vertebrae causing a fracture of the pedicle, lamina, or facet joints and allowing the front of the vertebrae to move forward. Cervical spondylolysis can lead to spondylolisthesis by altering the normal structure of the vertebral column and causing vertebral displacement. Congenital abnormalities of the facet joints can lead to spondylolisthesis, as the vertebrae are allowed to slip out of place. The condition is referred to as dysplastic spondylolisthesis. A further classification is pathological spondylolisthesis, where a defect of the bone, or a tumour causes the slip to occur.
Understanding the cause means that the correct treatment can be applied, such as adequate rest from the microtrauma-inducing sport, analgesics, anti-inflammatories, physical therapy, or surgery in cases where significant damage has occurred and conservative treatment has proved ineffective. Spondylolysis normally does not require surgical intervention, unless it progresses into spondylolisthesis. The use of a brace may be helpful in reducing neck pain in the meantime. Identifying the exacerbating activity is key to preventing future occurrences of the condition, meaning that correct posture, and core muscle strengthening, along with neck strengthening exercises are key to a positive outcome. In the case of lumbar or cervical spine surgery, typically a spinal fusion is the procedure used to correct spondylolisthesis.
Causes of Spondylolisthesis
There are five major types of spondylolisthesis, all with different causes. The most common is degeneration of the components of the vertebral column and spine – degenerative spondylolisthesis. These structures, when healthy, maintain the spine’s correct position, allowing for strength and flexibility of movement. As these components degrade, through chronic wear and tear they lose their ability to stay supple and strong, making shifts in the spinal structure more likely, including the slippage of the vertebrae as occurs in spondylolisthesis. Cartilage calcification and degeneration, ligaments stretching and tearing, bone spurs or osteophyte growth, and changes in the shock absorbing and cushioning qualities of the intervertebral discs means that the vertebra can slide forward (or backward in the case of retrolisthesis), and cause deformity of the spine, with associated pain, paraesthesia, pinched nerves, numbness, muscle weakening, and impaired mobility.
Degeneration with age is not, however, the only cause of spondylolisthesis. Congenital abnormalities such as misshapen bones in the spinal column, or problems with the pelvic incidence (tilt), can also cause excess pressure on the spinal column leading to slippage of the vertebrae and spondylolisthesis (Labelle, 2004). This is known as dysplastic spondylolisthesis. Isthmic spondylolisthesis is a further classification, used to describe the condition that results from spondylolysis. This is a condition where repetitive microtrauma causes defects in the pars interarticularis, a specific part of the vertebrae, which may develop into spondylolisthesis if the vertebrae slip forward due to this defect. Spondylolysis is commonly caused in adolescents and children by activities such as gymnastics, football, wrestling, and diving. With appropriate rest and possible use of a brace it should correct itself without developing into spondylolisthesis.
Specific injury or damage to the vertebrae through complications of surgery, epidural injections, assault, or accidents, such as whiplash, can cause traumatic spondylolisthesis. These types of injury can result in fractures of the lamina, facet joints, or pedicle, and allow the vertebrae to slide forward. The final class is pathologic spondylolisthesis. This is where the vertebrae slip forward due to an abnormal growth such as a tumour or bone growth. The specific pathology of the spondylolisthesis requires careful diagnosis in order to apply appropriate treatment.
Symptoms of Spondylolisthesis
In some cases the patient may be asymptomatic and only discover the spondylolisthesis by chance when having an x-ray conducted for an unrelated reason. Many cases involving children cause no, or few, symptoms. Other patients suffer extreme symptoms, involving persistent, severe neck pain, back and spine, with radiating pain down the legs and arms. Pain may be worsened when hyperextending (arching) the back, making some activities such as yoga or pilates potentially unsuitable for those with spondylolisthesis. In general, however, these activities would be excellent for maintaining back and neck health.
Some patients may experience neurological symptoms, such as intermittent claudication or vesicorectal disorder; in most cases these patients will require spine surgery to correct the slippage and compression on spinal structures. Pinched nerves in the cervical spine may lead to weakness and numbness in the arms and shoulders, along with paraesthesia. Pain in neck and head can occur, depending on the location of the slippage and which nerves are being impinged upon. Symptoms of spondylolisthesis may share commonalities with symptoms of bulging or herniated discs, spinal stenosis, and cervical arthritis, as well as the issues found with severe osteophyte growth in the spine. If the patient experiences numbness in the genital area, or loses bladder or bowel control then they should seek medical help immediately as they may be signs of cauda equina syndrome which is considered a medical emergency.
As there are numerous blood vessels in the cervical area, including the arteries and veins leading up to the head, it is possible that spondylolisthesis can cause compression of these blood vessels. This may occur upon movement, with patients experiencing light-headedness upon rotation or flexion of the neck and head. If this occurs it is essential to seek medical assistance immediately as it may lead to blackouts, falls, and accidents as circulation to the brain is impaired.
Physical signs of the slippage of the vertebrae can, in extreme cases, include deformity of the back and neck, with stiffness of the neck, pain on rotation, flexion, and extension, and an abnormal tilt to the posture. Those with spondylolisthesis of the lumbar area may experience tightness in their hamstrings, sciatic nerve pain, and numbness in the legs and buttocks; the latter is a sign of cauda equina syndrome and should be thoroughly investigated.
Diagnosis of Spondylolisthesis
In general it will not be possible for a physician to observe outward signs of spondylolisthesis upon examining a patient. Taking a history of symptoms, and a detailed record of trauma and activities such as contact sports, the physician will recommend further tests and scans as they see fit. They may also ask patients to conduct some simple stretches, rotation or flexion of the neck, and to apply resistance during gentle pressure on their hands, shoulders, and head from the physician. The production, or relief, of pain from these physical tests can be enlightening as to the aetiology of their spine condition, and also make it easier for the physician to estimate the specific area which is damaged so as to scan that area. Common symptoms of spondylolisthesis, such as tight hamstrings, muscle spasms, and pain, may overlap with other conditions, such as muscle strain, disc herniation, spinal stenosis, and diabetic neuropathy, making it extremely important to obtain the correct diagnosis prior to commencing treatment.
Grades of Spondylolisthesis
X-rays taken from the side (lateral) can identify slippage of vertebra relative to the adjacent vertebrae. The degree of slippage can be calculated and is graded as follows: Grade 1 is a slip of up to 25%, grade 2 is a slip of 26%-50%, grade 3 is a slip of 51%-75%, and grade 4 76%-100%. Grade 5 is known as spondyloptosis and is where the vertebra has slipped off the next vertebra completely.
MRI or CT scans can be helpful in identifying any stenosis of the spine that may be causing neck, back, and shoulder pain, and radiating pain to the extremities. Paraesthesia, numbness, and weakness indicate nerve problems, possibly with a pinched nerve such as can occur in disc herniation. If a spinal fusion surgical procedure is being considered then a PET scan can ascertain whether the defective bone site has active bone growth occurring. This will affect the likely healing of the patient’s spine post-surgery, making decisions about the effectiveness of certain treatments simpler.
Treatment of Spondylolisthesis
Conservative treatment is the usual therapeutic course for patients with spondylolisthesis. In small children, where the slip is normally quite minor, the usual therapeutic plan is simple observation and restriction of boisterous activities. More significant slips pose a threat of progressive complication and justify the use of more invasive treatment methods. NSAIDs and analgesics are likely to be used, alongside physical therapy, and the condition will be monitored closely. If treatment is unsuccessful after six months or so, or if an acute exacerbation occurs, then surgery may be required.
If intermittent claudication and other neurological symptoms are present then the need for surgical intervention is more likely. Favored treatment plans for minor cases involve the use of analgesics and NSAIDs, or alternative supplements for those concerned with the potential side-effects of pharmaceutical medications. Epidural steroid injections and selective nerve root blocks may be used to provide relief from the condition and break the cycle of inflammation often found in spondylolisthesis. If the patient has adequate rest and refrains from any exacerbating activities, it is possible that the combination of anti-inflammatories, physical therapy and flexion strengthening exercises can alleviate, or even correct, the problem. Exercises to strengthen the core abdominal muscles are also likely to benefit a patient with spondylolisthesis as these may help correct underlying postural issues and alleviate some pressure on the spine. The use of a hyperextension brace may also assist those with isthmic spondylolisthesis as it can help to extend the lumbar spine and promote healing.
Surgery varies depending on the type of spondylolisthesis. Isthmic spondylolisthesis patients are likely to have repair work done on the portion of the vertebrae that is defective, most notably the pars interarticularis. Healthy post-surgical healing is likely to occur if an MRI or PET scan reveals active bone at the defective site. In this procedure the scar tissue will be removed and a bone graft put in place with screws to hold it across the defect, thus encouraging the re-knitting of the bone. Those patients with neurological symptoms will likely undergo a decompression procedure to make the foramina through which the nerves exit the spine more spacious. Decompression surgery is often conducted alongside fusion to reposition the vertebrae correctly and hold them in place with plates. In some cases the vertebrae are fused in the position they have moved to, to prevent further slippage. This is done in cases where moving the vertebrae back has an increased risk of further nerve damage.
Standaert , C.J., Herring, S.A., Halpern, B., King, O., (2000), Spondylolysis, Phys Med Rehabil Clin N Am., Vol.11, No.4, pp.785-803.
Kalichman, L., Hunter, D.J., (2008), Diagnosis and conservative management of degenerative lumbar spondylolisthesis, Eur Spine J., Vol.17, No.3, pp.327-35.
Labelle, H., Roussouly, P., Berthonnaud, E., Transfeldt, E., O’Brien, M., Chopin, D., Hresko, T., Dimnet, J., (2004), Spondylolisthesis, pelvic incidence, and spinopelvic balance: a correlation study, Spine (Phila Pa 1976), Vol.29, No.18, pp.2049-54.