Lumbosacral Spondylolisthesis

Spondylolisthesis is defined as forward translation of a vertebral body with respect to the vertebra below.[2, 3, 4, 5, 6, 7] The term is derived from the Greek roots spondylo, meaning spine, and listhesis, meaning to slide down a slippery path.

Spondylolisthesis can occur at any level of the spinal column, although it is most common in the lower lumbar spine. Most cases are thought to result from minor overuse trauma, particularly repetitive hyperextension of the lumbar spine. Spondylolysis, a break in the vertebra typically in the region of the pars interarticularis, may or may not be associated with a spondylolisthesis. If the pars defect is bilateral, it may allow slippage of the vertebra, typically L5 on S1, resulting in spondylolisthesis.

Both spondylolysis and spondylolisthesis are often asymptomatic, and the degree of spondylolisthesis does not necessarily correlate with the incidence or severity of symptoms, even when a patient is experiencing back pain. However, these 2 entities have been reported to be the most common underlying causes of persistent low back pain among children and adolescents, despite the fact that most cases are asymptomatic.[4, 6, 8, 9, 10]

Spondylolisthesis can be classified into the following 6 distinct categories.

• Type I is congenital (dysplastic) and is caused by agenesis of the superior articular facet.

• Type II, or isthmic (spondylolytic) spondylolisthesis, is caused by pars interarticularis defects.

• Type III, or degenerative spondylolisthesis, is secondary to articular degeneration.

• Type IV, or traumatic spondylolisthesis, is caused by fracture or dislocation of the lumbar spine, not involving the pars.

• Type V is pathologic and is caused by malignancy, infection, or other types of abnormal bone.

• Type VI is postsurgical (iatrogenic).

A computer-assisted classification has been recommended by the Spinal Deformity Study Group based on slip grade, pelvic incidence, and sacro-pelvic and spinal balance. Software enabled observers to identify all 6 types of spondylolisthesis and to identify 7 anatomic landmarks on each radiograph.[11]

A variety of methods are also used to measure the degree of spondylolisthesis. The primary focus of this article is isthmic spondylolisthesis only, because it is the most common variety and because it is relevant to sports medicine.

Isthmic (spondylolytic) spondylolisthesis usually occurs in children older than 5 years, most commonly in those aged 7-8 years, and it rarely occurs before walking begins. Slip progression is minimal after skeletal maturity.

Isthmic spondylolisthesis is further divided into the following 3 subtypes:

• Type IIA, or lytic spondylolisthesis, involves a defect in the pars area and is thought to result from recurrent microfractures from the impact of the articular processes against the pars while in extension. This defect usually occurs by age 6 years and is occasionally associated with developmental anomalies such as lumbarization, sacralization, and spina bifida occulta.

• Type IIB involves an intact but elongated pars, probably resulting from repetitive microfractures that heal in an elongated position, much like pulled toffee.

• Type IIC spondylolisthesis, a rare form, results from an acute fracture of the pars interarticularis during significant trauma.

For helpful patient education resources, see Back Pain, Slipped Disk, and Lumbar Laminectomy.

Functional anatomy

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). Spondylolisthesis has never been reported in quadrupeds or in people who are chronically bedridden.

Sport-specific biomechanics

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. Examples of such activities include gymnastics, football (lineman), wrestling, weight lifting (particularly standing overhead presses), rowing, pole vaulting, diving, hurdling, swimming (especially the butterfly stroke), baseball (especially pitching), tennis (especially serving), sailing (particularly the hiking maneuver), and volleyball. Gymnastics and football are generally considered the highest risk sports.[5, 6, 7, 12]

United States data

The prevalence of isthmic spondylolisthesis is approximately 5% at age 5-7 years, with an increase to 6-7% by age 18 years. This condition is twice as common in males as in females, and the prevalence is lower among blacks (2.8%, black men; 1.1%, black women) than among whites (6.4%, white men; 2.3%, white women). Despite the higher prevalence among males, progression, although still rare, has been reported to be more common in females.[13]

Additional risk factors include having a first-degree relative with a slip, occult spina bifida at S1, and the presence of scoliosis.

International data

A study by de Schepper et al described the magnetic resonance imaging (MRI) findings of 683 patients with low back pain who presented for a lumbar MRI examination after they had been referred by their general practitioner (GP). The investigators found that 94% of the participants had abnormal MRI findings, and 18% showed signs of spondylolisthesis.[14]

Patients with spondylolisthesis are usually asymptomatic. The onset typically occurs during the growth spurt in late childhood and early adolescence, probably because of increased participation in strenuous sports during this period. Spondylolisthesis is an unlikely cause of back pain in adults (especially after age 40 years) with no history of symptoms before age 30 years; typically, another cause is identified (eg, disc injury, strain).

Low back pain is the most frequently reported symptom, and it is often exacerbated by motion, particularly lumbar extension and twisting. Radiation of pain into the buttocks is not uncommon. The patient may report relief of pain with extended periods of rest. Rarely, associated leg pain is present in the L5 or S1 distribution as a result of nerve root compression. Symptoms are often more severe during the advanced months of pregnancy.

Findings noted during the physical examination may include the following:

• With high-grade slips, a palpable step-off may be felt over the spinous process at the level above the slipped vertebra because the posterior arch of the forward translated vertebra remains in place.[15]

• Tenderness to deep palpation of the spinous process above the slip (typically L4) may be present. This palpation occasionally causes radicular pain.

• A positive one-leg hyperextension test (stork test) suggests a diagnosis of spondylolysis, but it is a nonspecific test with low sensitivity[16] and low specificity.[17]

• Hamstring tightness that is associated with all grades of symptomatic spondylolisthesis occurs at a rate of 80%. It commonly results in an abnormal gait, typically waddlelike, due to the inability of the patient to flex the hip with the knees extended.

• Paraspinal muscle spasm and tenderness are usually present.

• In advanced cases, a relatively short torso with a low rib cage, high iliac crests, and heart-shaped buttocks are noted.

• Limited forward flexion of the trunk is common with reduced straight-leg raising, which may cause pain but rarely any signs of nerve root tension.

• Postural deformity and a transverse abdominal crease are seen as a result of the pelvis being thrust forward.

• A thorough neurologic evaluation should be performed, including sensation in the sacral region to check for cauda equina compression.

• Weakness in the tibialis anterior muscle (L4 nerve root) is common.

Imaging studies are necessary for an accurate assessment and diagnosis of spondylolisthesis. Consensus is lacking on the optimal imaging protocol for spondylolysis/spondylolisthesis, in part because of the issue of radiation exposure to the pediatric spine, the many pros and cons for each modality, and developing technology, potentially making magnetic resonance imaging (MRI) the most sensitive option.[18]  Imaging is typically pursued in the following order:

• Radiography
• Single-photon emission computed tomography (SPECT) scanning
• Computed tomography (CT) scanning
• MRI

Radiography

Standing lateral radiographs are the preferred method of evaluating slippage of the vertebrae in persons with spondylolisthesis, and they are an excellent means of monitoring for progression of the condition.[19, 20, 21]  The standing lateral view is best because the translation occurs in the sagittal plane and is often accentuated during standing (due to the oblique orientation of the lower lumbosacral intervertebral disc spaces).

Standing flexion/extension films should be obtained to assess the degree of instability of the involved vertebrae. These radiographs are also useful in detecting an occult spondylolisthesis.

The anteroposterior view offers limited information in mild cases of spondylolisthesis; however, in cases of severe slips, this view may reveal the so-called reverse Napoleon hat sign because the L5 vertebra is viewed end-on through the sacrum, giving rise to the appearance of an upside-down Napoleon hat.

Oblique films are best for evaluating the integrity of the pars interarticularis. A defect is seen as a collar on the neck of the Scotty dog.

Single-photon emission computed tomography (SPECT) scanning

SPECT scanning is an extremely sensitive means of evaluating the integrity of the pars interarticularis, and this bone scanning modality is useful in determining the acuteness of slippage in those with spondylolisthesis. The scan results are positive at the pars interarticularis in those with acute spondylolysis, and then the findings revert to normal once the condition is chronic, even though healing has not occurred.

As spondylolisthesis develops and progresses, findings become positive more anteriorly and diffusely. Therefore, SPECT scanning helps the physician predict who would benefit from a spinal fusion. Those patients with positive findings should benefit because the slippage is acute.

Computed tomography (CT) scanning

CT scans are the best test for defining bony detail, especially in surgical planning.[22, 23]  CT is an excellent imaging modality for evaluating the pars interarticularis. The size of the defects in type IIA lesions can be measured.

CT scans may help distinguish between type IIA and IIC lesions by identifying the presence of cortication of the defects. These studies are also helpful in identifying fibrocartilaginous tissue at the defects, which may cause nerve root compression, leading to radicular symptoms

Sagittal reformations may help clinicians in assessing foraminal stenosis

Magnetic resonance imaging (MRI)

The value of MRI in the diagnosis of spondylolysis is highly dependent on sequencing. It is useful in the diagnosis of early active spondylolysis.[24]

MRI should be ordered in cases that are associated with neurologic deficits. This imaging modality is an excellent means of observing compression of the dural sac, such as in degenerative cases in which the posterior arch is left behind and increased compression results from advancing slip.

Grading spondylolisthesis

The following methods are used to grade spondylolisthesis:

• Meyerding technique: This technique involves dividing the superior aspect of the vertebra below the slip into 4 equal divisions, as is observed on a lateral radiograph. Assess where the posterior arch of the slipped vertebral body lies with respect to these 4 quadrants.

  • Grade 1: Less than 25% slippage

  • Grade 2: Between 25% and 50% slippage

  • Grade 3: Between 50% and 75% slippage

  • Grade 4: Between 75% and 100% slippage

  • Grade 5: Greater than 100% slippage (also called spondyloptosis)

• Taillard method: This method describes the degree of slippage as a percentage of the anteroposterior diameter of the top of the first sacral or fifth lumbar vertebra (ie, %slip = displacement of (L5 on S1/width of S1) X 100). The result is an exact percentage of the slip.

• Sacral inclination: This inclination is the angle formed between the posterior sacral border and a vertical line perpendicular to the floor and, thus, it is another means of measuring the extent of slippage. The sacrum tends to a more vertical position with increasing slips.

• Slip angle: This angle is the relationship determined by a line along the posterior border of S1 and the inferior endplate of L5.

The slip angle and percentage slip may predict the risk of future slip progression.

If alternative diagnoses are being considered, order appropriate laboratory tests (eg, laboratory workup for malignancy).

An electromyogram (EMG) may be helpful for detecting subtle radiculopathy, especially in the setting of a negative neurologic examination.

 

 

Rehabilitation program

Physical therapy

As a general rule, physical therapy should not be started until after an adequate rest period and once pain with daily activities has subsided.

The goals of physical therapy are to decrease extension stresses of the lumbar spine and to strengthen elements that promote an antilordotic posture. This consists of exercises to strengthen the abdominal muscles (eg, Williams flexion-type exercises) and flexibility programs to stretch the spinal extensor muscles, hamstrings, and lumbodorsal fascia.

Bracing with a thoracolumbosacral orthosis (eg, Boston antilordotic brace) may offer relief for those who do not respond to activity restrictions or whose daily activities are producing symptoms.[2, 25] This type of bracing is usually effective in most patients with less than 50% slippage. The brace is generally worn for 3-6 months and may be worn during activity.

If the slippage is less than 50% but the patient is symptomatic, then nonoperative therapy (eg, stretching and strengthening exercises, antilordotic brace, activity modification) is instituted.[2] If pain continues to persist, then a spinal fusion is recommended.

Occupational therapy

Avoidance of heavy-duty labor or activities with repetitive lumbar extension is necessary to allow healing to occur. An occupational therapist can be very beneficial for those individuals who need instructions and compensatory strategies for activities of daily living.

Recreational therapy

Restriction from sports and other activities that require repetitive hyperextension may be sufficient treatment in young athletes. Patients with grade 2 slippage are generally instructed to avoid hyperextension loading of the spine after symptoms resolve with conservative treatment.

Medical issues/complications

Younger patients require more careful observation, even if the initial symptoms resolve, because of their greater risk for progression. In an asymptomatic child with slippage up to 25% (grade 1), initially observe with radiographs every 4-6 months if younger than age 10 years, semiannually until age 15 years, then annually until the end of growth. No limitation of activities is required, but the patient is advised to avoid occupations that entail heavy labor.

If the slippage is 26-50% (grade 2) and the patient is asymptomatic, then the treatment is the same as for the grade 1 slippage but with a warning against participation in contact sports or sports requiring lumbar hyperextension (eg, football, gymnastics). In general, the results of conservative management are good in most athletes with grade 1 or 2 slips.

Complications include slip progression, loss of motion segments, neurologic deficit (eg, cauda equina syndrome, radiculopathy [greatest risk with >50% slippage]), and residual deformity following fusion of a high-grade spondylolisthesis.

Surgical intervention

Surgery is indicated in the following settings[25, 26] :

• For skeletally immature patients with greater than 30-50% slippage (with or without symptoms) because they are at greater risk for progression.
• In the event of progressive neurologic deficit.
• For patients with any degree of slip who have pain persisting for more than 6-12 months that has not been relieved with rest and immobilization.

Spondylolysis or low-grade spondylolisthesis may be managed nonoperatively.[2, 3]

Options for operative management include direct repair of the spondylolytic defect, fusion in situ, reduction and fusion, and vertebrectomy. Ideally, repair of a pars defect is for young patients with spondylolysis but no spondylolisthesis. Best results are observed in those with a lytic defect between L1 and L4. L5 defects yield less predictable results. Disc degeneration as seen on magnetic resonance imaging (MRI) is a relative contraindication. Slippage of greater than 2 mm decreases the likelihood of successful repair.

Fusion in situ at the involved level is the criterion standard of surgical treatment for most patients in whom conservative management fails. Fusion in situ is recommended for patients with persistent, symptomatic, low-grade spondylolisthesis and for patients who are not candidates for repair of the pars defect. The desire to participate in a contact sport should not be the sole indication for a fusion.

Decompression and fusion are typically performed in cases of dural sac compression with the presence of bowel or bladder dysfunction or significant motor deficits. Decompression is never performed without concomitant fusion. Pedicle screw fixation enables rapid mobilization and early ambulation after decompression and fusion. Fixation may be beneficial in repairing pseudoarthrosis and, in the face of laminectomy, in preventing further slippage while awaiting fusion.[27, 28]

Spondylolisthesis reduction is performed either through closed or open procedures. Reduction serves to correct lumbosacral kyphosis and to diminish sagittal translation observed in high-grade slips. Vertebrectomy may be used to treat spondyloptosis (grade 5 spondylolisthesis), as an alternative procedure to reduction or fusion in situ. The postoperative rate of permanent neurologic deficits is high (25-30%), although many are preexistent. This high rate of deficits does not appear to be balanced by improved results; fusion in situ has achieved similar clinical outcomes with a lower complication rate.

Consultations

The following specialists might be consulted:

• Sports medicine specialist

• Orthopedic surgeon, spine surgeon, or neurosurgeon if surgical intervention is considered (ie, high-grade slippage, refractory cases)

Rehabilitation program

Physical therapy

Antilordotic strengthening and flexibility exercises for the back and lower extremities are emphasized (progressive spinal stabilization).

Occupational therapy

Avoidance of heavy labor or any repetitive hyperextension continues to be important. An occupational therapist can assist by completing an ergonomic evaluation and assessing subsequent workstation modifications if needed to avoid unnecessary loading of the patient's lumbosacral spine.

Recreational therapy

Once asymptomatic, patients with grade 1 or less slippage may resume their activities as desired (as long as they remain pain free). Continue to emphasize avoidance of aggravating factors, particularly those activities that involve repetitive hyperextension of the back.

Surgical intervention

Surgery is indicated if the slippage is greater than 50% or in cases of refractory symptoms or progressive neurologic deficit.

Consultations

Consultations with specialists may be indicated as in the acute phase (eg, sports medicine specialist, orthopedic surgeon, spine surgeon, neurosurgeon).

Rehabilitation program

Physical therapy

Recommend that the patient continue with his or her home exercise program, focusing on lumbar stabilization to reduce biomechanical stresses (particularly extension) in the lumbosacral spine. The program should continue to include both stretching and strengthening exercises. The athlete now starts to focus on sports-specific retraining, with attention to skill and technique refinement.

Occupational therapy

Recommendations similar to those in the acute and recovery phases are continued in the maintenance phase. The patient should still be instructed to avoid heavy labor or any activity that may cause repetitive hyperextension loading of the lumbar spine.

Recreational therapy

If the patient demonstrates low-grade spondylolisthesis, he or she may continue pain-free activities as tolerated. Those with higher-grade or symptomatic spondylolisthesis must avoid aggravating activities (especially those involving repetitive hyperextension or heavy labor).

Surgical intervention

Surgery is necessary only if high-grade slippage is present or if symptoms are refractory to conservative management.

Consultations

Specialty consultations are indicated only if high-grade slippage is present or if symptoms are refractory to conservative management.

Return to play

In general, the athlete is ready to return to play once the following are demonstrated[29] :

• Full, pain-free range of motion

• Normal strength

• Appropriate aerobic fitness

• Adequate spinal awareness and mechanics

• Performance of sports-related skills without pain

Patients with a slippage equal to or less than grade 1 may resume desired activities once they are asymptomatic. Patients with a grade 2 or greater slippage are generally instructed to avoid hyperextension loading of the spine after symptoms resolve with conservative treatment.

Complications

Possible complications include slippage progression, neurologic deficit, and disc degeneration adjacent to the previously fused segments.

Prevention

Avoiding activities that involve repetitive hyperextension is important for preventing spondylolisthesis. Continuous flexibility and strengthening exercises are recommended to minimize excessive forces on the lumbosacral spine. If overweight, the athlete is encouraged to achieve his or her ideal weight to reduce stress on the lumbar spine.

Prognosis

The prognosis of spondylolisthesis is benign in most cases, and the problem can usually be managed nonoperatively. Surgical correction, when necessary, is usually successful in eliminating symptoms, and the union rate following surgery has been estimated at approximately 75% (depending on the degree of slippage and the surgical technique used).

Education

Patients need to be educated regarding which activities to avoid and which exercises should help minimize the forces that aggravate the condition, and how to identify the typical signs of complications. In their chosen sport, proper technique should be emphasized along with avoidance of abrupt increases in training frequency.

Medical/legal pitfalls

Medicolegal issues may arise in cases of missed diagnoses (especially if they result in permanent symptoms), improper treatment, or poor postoperative outcomes.

The goals of pharmacotherapy are to reduce morbidity and to prevent complications.

Class Summary

Nonsteroidal anti-inflammatory drugs (NSAIDs) have analgesic, anti-inflammatory, and antipyretic activities. The mechanism of action of these agents is not known, but NSAIDs may inhibit cyclooxygenase activity and prostaglandin synthesis. Other mechanisms may include leukotriene synthesis inhibition, lysosomal enzyme release, lipoxygenase activity, neutrophil aggregation and various cell membrane functions.

Ibuprofen (Motrin, Ibuprin)

Ibuprofen is available in both prescription and nonprescription strength.

Class Summary

Nonnarcotic analgesics are used for control of pain but not inflammation. These drugs are not associated with any adverse gastrointestinal (GI) reactions (ie, gastritis, peptic ulcer disease).

Acetaminophen (Tylenol, Feverall, Tempra, Aspirin-Free Anacin)

Acetaminophen is the drug of choice for pain in patients with documented hypersensitivity to aspirin or NSAIDs, with upper GI disease, or who are taking oral anticoagulants.