The term spondylolisthesis derived from the Greek spondylos, meaning “vertebra,” and olisthenein, meaning “to slip.”
Spondylolisthesis is defined as anterior or posterior slipping of one segment of the spine on the next lower segment.
There are two clasifications of spondylolisthesis. One is by Wiltse, Newman, and Macnab’s classification of and other is by Marchetti and Bartolozzi.
It is based on etiological and topographical criteria. It is argued that it is difficult to predict progression or response to treatment
This classification scheme divides the spondylolisthesis in 5 types
Type I – Dysplastic
Congenital abnormalities of the upper sacral facets or inferior facets of the fifth lumbar vertebra that allow slipping of L5 on S1.
The congenital abnormalities of lumbosacral articulation include maloriented or hypoplastic facets, sacral deficiency or poorly developed pars interarticularis.
There is no pars interarticularis defect.
Type II – Isthmic
There is a defect in the pars interarticularis that allows forward slipping of L5 on S1.
There are three subtypes
A stress fracture of the pars interarticularis [Lytic type]
An elongated but intact pars interarticularis [Elongated type]
An acute fracture of the pars interarticularis
Type III – Degenerative
This lesion results from intersegmental instability of a long duration with subsequent remodeling of the articular processes at the level of involvement.
Type IV- Traumatic
This type results from fractures in the area of the bony hook other than the pars interarticularis.
Type V – Pathological
This type results from generalized or localized bone disease and structural weakness of the bone e.g osteogenesis imperfecta, infection
Marchetti and Bartolozzi attempted divided the condition into developmental and acquired forms.
To classify according to this classification, it must be first determined if the condition is developmental or acquired.
Classification of Marchetti-Bartolozzi
- With lysis
- With elongation
- With lysis
- With elongation
- Acute fracture
- Stress fracture
- Direct surgery
- Indirect surgery
- Local pathology
- Systemic pathology
Most spondylolistheses in children and adolescents are developmental.
There is another classification by Meyerding which is based on percentage of slip
Grade 1: 25% of vertebral body has slipped forward
Grade 2: 50% of vertebral body has slipped forward
Grade 3: 75% of vertebral body has slipped forward
Grade 4: 100% of vertebral body has slipped forward
Grade 5: Vertebral body completely fallen off (i.e.,spondyloptosis)
Normal Canal Dimension In Lumbar Spine
Normal canal dimension in lumbar spine are fairly constant and are given below.
Coronal (interpedicle) (mm)
The idea of normal values helps to determine the level of stenosis of the canal.
Dysplastic spondylolisthesis forms the type I spondylolisthesis in Wiltse classification system. It is a true congenital spondylolisthesis that occurs because of malformation of the lumbosacral junction with small, incompetent facet joints.
Dysplastic spondylolisthesis is very rare.
But when it occurs, it is associated with fast progression and severe neurological deficits.
There is a congenital insufficiency of facet joints (of S1 or L5) & disc complex, resulting in gradual attenuation of the pars interarticularis leading to ventral subluxation of L5 ventrally on the sacral facets and pedicles may get elongated as well, further contributing to the forward subluxation; This type, however is not associated with any gap or defect in pars interarticularis.
The articular processes of the vertebrae are tipped too far forward with the facet joints are facing forward (sagittal or axial) instead of sideways (coronal). Another association is malformed sacrum with spina bifida.
Studies have reported a familial predisposition.
Spondylolisthesis is present in 5% of the population and there is no gender difference in occurrence.
Most spondylolistheses in children and adolescents are developmental.
This type of spondylolisthesis generally is not noticed until later in childhood or even in adult life.
Etiology and Natural History
Developmntal stenosis needs to be differentiated from acquired traumatic spondylolisthesis caused by stress fracture. Trauamtic sopndylolisthesis following a stress fracture occurs in individuals with no posterior element dysplasia and with normal spino pelvic morphology.
Following conditions are thought to represent a continuum of disease
- Pars stress reaction
Spondylolysis is a pure stress fracture caused by micrortrauma due to repetitive loading of lumbosacral spine and is typically seen in athletes. In absence of significant dysplasia of posterior elements, the risk of progression to a high grade spondylolisthesis and of neurological abnormality is low in traumatic stress fracture.
In contrast, individuals with developmental spondylolisthes have a genetic predisposition, variable degrees of vertebral dysplasia, a sacropelvic morphology that predisposes to abnormal spino-pelvic balance.
During growth, these individuals undergo abnormal development of the sacrum and pelvis which leads to altered mechanical stresses.
Those associated with high pelvic incidence, low sacral table angle and high sacral slope are subjected to higher shear stresses resulting in increased tension on L5 pars interarticularis. h with lower pelvic incidence but a high sacral table angle and low sacral slope are predisposed to impingement of L4 and S1 posterior facets with posterior elements of L5 leading to repititive trauma to L5 pars dur
ing extension movements
Mechanical stresses play an important role in this process. Erect posture produces a constant downward and forward thrust on the lumbar vertebrae.
Stresses on the pars interarticularis are accentuated during repetitive hyperextension, which results in increased contact of the caudal edge of the L4 inferior articular facet with the L5 pars interarticularis.
This collective trauma may eventually result in a stress fracture of the pars interarticularis. Spondylolisthesis may occur when bilateral pars defects are present, which allows forward slippage of the vertebra (typically L5 on S1).
Sports that involve repetitive hyperextension and axial loading of the lumbar spine may result in repetitive microtrauma to the pars interarticularis, resulting in spondylolysis and sometimes spondylolisthesis.
Gymnastics, football, wrestling, weight lifting rowing, pole vaulting, diving, hurdling, swimming (especially the butterfly stroke), baseball , tennis , sailing and volleyball are the sports that carry the risk.
Gymnastics and football are generally considered the highest risk sports.
Risk Factors For Progression
Risk of progression in spondylolytic patients is low. [4-5%]
An increased risk of progression has been noted in
- Female gender
- Presentation at a young age
- Severe slip at time of presentation
- Nonisthmic type
- Increased lumboscaral kyphosis
- A high degree of bony dysplasia
In a skeletally immature patient , the lumbosacral kyphosis has been suggested to be most useful predictor of progression.
In most of the cases the medical consultation is sought because of postural and gait problems rather than the pain.
Pain is mostly backache which occurs during the growth spurt. Sometimes the leg pain may also occur. The pain in the back is due to instability of the affected segment whereas pain the leg is due to irritation of the nerve root.
Symptoms are aggravated by high activity or sports decrease on rest or with medication.
Depending on severity of the listhesis, physical findings may vary.
In mild cases, there may not be any finding on physical examination.
In cases with moderate amount of slip, a step may be palpable at lumbosacral junction and motion of lumbar spine is restricted. Hamstring tightness may be felt on straight leg raising.
With further slip, the patient assumes a lordotic posture above the level of the slip to compensate for the displacement. The sacrum becomes more vertical, and the buttocks appear heart shaped because of the sacral prominence.
In severe slips, the trunk becomes shortened and often leads to complete absence of the waistline. These children walk with a peculiar spastic gait called pelvic waddle or crouched gait.
Scoliosis associated with spondylolisthesis may be found.
Routine diagnosis of spondylolisthesis is made on radiographs. These include
- Anteroposterior view
- Standing lateral views
- Ferguson coronal view.
The Ferguson coronal view is obtained by making the x-ray beam parallel to the L5-S1 disc. This view depicts clearer profile of the L5 pedicles, transverse processes, and sacral ala.
Sometimes oblique views are also done in suspected pars defect which is not visible on routine views.
Bone scan is indicated in children where palin film do not show any defect but the defect is believed to be present. An bone scan may shw the pars defect in stress reaction stage determined by increased uptake.
Mostly not needed, a CT scan can be used to differentiate between a stress reaction and acute stress fracture. [Developmental versus traumatic]. CT is the best study to diagnose and delineate anatomy of lesion.
MRI is useful in determining the extent of injury to the disc at the level of the spondylolisthesis. Nerve root compression also can be evaluated. MRI is indicated if neurologic symptoms present. It is a useful tool to diagnose associated stenosis.
Non operative treatment includes
- Restriction of the patient’s activities
- Rehabilitation and exercises of spinal, abdominal, and trunk muscles
- Intermittent use of a rigid back brace
Non operative treatment is useful if symptoms are few and the spondylolisthesis is mild.
Gradual increase in activity is allowed if symptoms improve.
For non symptomatic patients no active treatment is required but contact sports and high energy that might injure the back are to be avoided A follow up every 6-12 months til the completion of growth is required.
Indications for surgery include
- Persistent symptoms despite 9 months to 1 year of conservative treatment
- Persistent tight hamstrings
- Abnormal gait
- Pelvic-trunk deformity.
- Development of a neurological deficit
- Progression of the slip [Indicative of a severe dysplasia].
Early surgery have benefit over delayed ones. An early surgery may may prevent difficult or risky surgeries at a later time.
A slip of more than 50% in asymptomatic patients with dysplasia would warrant surgery.
In low dysplastic type of sopndylolisthesis, a spinal fusion [posterolateral] between L5 and the sacrum is recommended for slips of less than 50% [mild dysplasia] in children and adolescents who are symptomatic despite conservative treatment. This degree of slippage is a mild dysplasia (low dysplastic type) usually without a significant slip angle. In our experience, these children do well with a posterolateral fusion in situ. Instrumentation with pedicle screw is done to avoid need of postoperative immobilization. .
In high dysplastic spondylolisthesis, slippage of more than 50% requires fusion. The operative options include
- Posterior in situ fusion
- Instrumentation and posterior in situ fusion
- Posterior decompression, partial reduction, instrumentation, and fusion
- Posterior decompression, complete reduction, instrumentation, and posterior fusion
- Posterior fusion with postoperative cast reduction
- Posterior instrumentation and fusion combined with posterior lumbar interbody fusion
- Anterior release; and intradiscal graft or structural cage combined with posterior instrumentation and fusion.
For grade V [spondyloptosis] L5 vertebra removal with L4 to the sacrum fusion has been described.
The reduction of spondylolisthesis with instrumentation carries risk of increased operative time, complications, and reoperations. Therefore most of authors recommend fusion in situ [without reduction] a method of choice though reduction increases the chances of fusion itself.
If a patient has a neurological deficit preoperatively, decompression of the cauda equina at the time of the arthrodesis can be considered.
Postoperatively, a brace [Paantaloon brace] is worn for 3 to 4 months.
- Neurologic deficits
- Progression of slippage
- Hardware failure
Degenrative spondylolistheis was first described by Rosenberg in 1975. The most commonly affected level is L4-L5 followed bby L3-L4. It may occur at two levels or even three levels simultaneously.
It has also been reported in cervical spine.
Degenerative spondylolisthesis is more common in people over age 50. It is more common in women and blacks.
Facet joints of the vertebral column restrain the motion of the spine [Allow flexion and extension but restrict rotational movements] while the disc itself acts as shock absorber. With age, as the degeneration sets, the facet joint may not remain competent and allow vertebral body to slip forward on the other.
With slip and enlargement of facets with time, the canal space reduces leading to spinal stenosis.
The degree of slip in degenerative spondylolisthesis is almost always a grade 1 or 2. [Compare with Developmental stenosis]
Symptoms are mostly produced due to facet joint arthritis and spinal stenosis [Decrease in canal space]
Low back pain with or without leg apin is most common presentation. Leg pain without back pain can also be a presenting complaint.
Symptom suggestive of nerve irritation or compression [ Numbness, heaviness of the legs, Pareasthesias or tingling senation may be present]
Pseudoclaudication, a feature typical of spinal stenosis may be present.
Patients may have decreased symptoms while sitting or further bending as canal becomes more spacious with flexion of the spine [Similarly, the space reduces on extension of spine and increased pain may be associated with it].
Tight hamstring muscles (the muscles in the back of the thigh) and stiffness in the lower back may be associated findings.
Nerve root damage is very rare with degenerative spondylolisthesis per se but decreased canal space may make the structures more vulnerable to any insult like disc herniation.
With increased stenosis, patient may not be able to walk even a few meters.
Diagnosis can be made on routine xrays. AP and lateral views reveal the slip and associated degenrative changes may also be noted. MRI reveals neural compression and stenosis.
Symptomatic analgesics, local gels for back pain, hot compresses and steroids are varoius prescribed drugs for this ailments
Life Style Modification
This generally includes:
- Bed rest
- Avoid standing or walking for long periods
- Avoiding activities that require spine extension
For patients with severe pain, especially leg pain, epidural steroid injections may be an option. They decrease pain and increase a patient’s function in up to 50% of cases. Epidural injections can be given for up to three times per year. The pain relief can lasts from one week to one year.
Most of the patients with degenrative spondylolisthesis get relieved by non surgical measures and surgery is rarely required.
Surgery may be considered in disabling pains not relieved by non surgical managemnt and in cases of progressive neurologic deterioration.
The surgery involves decompression and fusion along with spinal instrumentation.
Decompression surgery ( laminectomy) without fusion alone is not advisable as it can lead to instability.
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