Lumbar spondylolisthesis

Introduction

Spondylolisthesis is the anterior translation or displacement of one vertebral body relative to the caudal vertebral body.^1,2 The condition has five distinct types:

• Isthmic
• Degenerative
• Traumatic
• Dysplastic
• Pathologic

Isthmic and dysplastic are by far the most common and maybe found in pediatric patients, whereas degenerative, traumatic, and pathologic spondylolisthesis are acquired with age.¹

Anatomy

Isthmic spondylolisthesis is due to disruption of the pars interarticularis, resulting in anterior translation of the superior vertebra.^1,3 The pars interarticularis is part of the posterior segment of the lumbar vertebra where the superior articular process and the pedicle meet the lamina and inferior articular process.³ Isthmic spondylolisthesis is most likely to occur at the L5/S1 level.^2,4

Pathologic spondylolisthesis is caused by a primary bone disease or metastatic lesions affecting the pars interarticularis, whereas traumatic spondylolisthesis is due a fracture of the vertebral body in a location other than the pars. Most commonly these fractures are found in the posterior elements of the spine.¹

In the dysplastic type of spondylolisthesis, the anatomy of the facet joints allows for anterior translation of the superior vertebral body with out disruption of the posterior elements of neural arch. Additionally, the pars interarticularis is both intact and of normal anatomy.¹

Degenerative spondylolisthesis is most commonly found at L4/L5, where deterioration of the facet joins and intervertebral discs from osteoarthritis cause disruption of the structural stability of the spine and ultimately lead to spondylolisthesis.^1,2

Pathogenesis

Spondylolisthesis has yet to be reported in patients who do not ambulate, such as those with cerebral palsy. Therefore, an upright posture, ambulation, and repetitive axial loading for the spine likely contribute to the disease process. Repetitive axial loading to the par interarticularis is thought to lead to failure by fatigue.⁴

Other factors that contribute to the development of degenerative spondylolisthesis include specific elements of the anatomy of patients’ lumbar spine and sacrum. Patients with increased lumbar lordosis (measured from the superior end plate of L1 to the inferior end plate of L5) are more likely to develop degenerative spondylolisthesis.^5,6 Pelvic incidence is an angle measured between a perpendicular line drawn in the middle of the S1 end plate and a second line drawn to the center of the femoral heads. This value remains unchanged with growth. Patients with increased pelvic incidences angles are at increased risk for developing degenerative spondylolisthesis.⁵ This is likely related to the increased rotational force experienced by the L5 vertebral body.⁶

The size of the vertebral bodies is also significant in the development of degenerative spondylolisthesis. Patients with small vertebral bodies are at increased risk, which is likely due to the increased mechanical stress experienced by the vertebral bodies compared to those patients experiencing the same force but with larger vertebral bodies.⁵ Additionally, lordotic wedging of the lumbar vertebra is more common in patients with degenerative spondylolisthesis.⁶

Natural History

Spondylolysis, a defect in the pars, is present in 5% of the population; however, only 15% of these individuals will progress to spondylolisthesis.^1,7 The incidence of newly diagnosed degenerative spondylolisthesis has been reported to be 12.7%.⁵

Participation in athletics with continued rotation and hyperextension of the lumbar spine, such as football, diving, gymnastics and rowing, result in increased risk of developing both spondylolysis and spondylolisthesis.⁴

Degenerative spondylolisthesis is rarely found in patients younger than 40 years of age, and it has a female-to-male predominance of 3:1. The prevalence of the condition increases with age regardless of gender.² As expected, increased body mass index is also a risk factor for development of spondylolisthesis, especially in women, and is likely due to the increased axial load to the spine during every-day activities. Smoking and occupational exposure are not contributing factors to the devolvement of the condition.⁷

Clinical Presentation

Pediatric patients with spondylolisthesis most often present with back pain typically related to activity or a traumatic event.¹ Physical exam findings in the pediatric and adult populations may be significant for a palpable lumbrosacral step-off, hamstring contracture, or pain with extension of the lumbar spine.^1,3 Hamstring contracture can be observed in a patients’ gait by exaggerated flexion of the hips and knees in conjunction with a shortened stride.⁴

The clinical presentation of spondylolisthesis in the adult population is highly variable. Patients may present with lower back pain, but this is fairly unspecific to the condition. Symptomatic spinal stenosis manifested by radicular symptoms such as leg pain, weakness, numbness, or tingling are also possible.² However, unlike the pediatric population, cross-sectional studies of adults have failed to demonstrate a significant association between low back pain and the presences of lumbar spondylolisthesis.⁷ Rates of low back pain in patients with spondylolisthesis are similar to rates in the population in general, suggesting the condition may not be a significant cause of low back pain and, therefore, may question the need for surgical intervention for back pain alone.^2,3

Rectal exam is warranted in patients who present with high-grade slips of greater than 50% to evaluate the integrity of the sacral nerve roots and to rule out cauda equina.¹ While cauda equina syndrome is rare, patients with the dysplastic type of spondylolisthesis are at an increased risk because the posterior neural arch is intact. In contrast, patients with isthmic spondylolisthesis caused by bilateral pars defects are unlikely to have cauda equina syndrome because the posterior arch is free from the remainder of the vertebral body, making it difficult to impinge the nerve roots.³

Imaging and Diagnostic Studies

Primary imaging should consist of lateral and anteroposterior radiographs of the lumbosacral spine.^1,8 Oblique lumbar views may help to accentuate a pars defect or spondylolysis, which is demonstrated by lucency in the collar of the “scotty dog” and are consistent with the isthmic type of spondylolisthesis. Flexion and extension views can be used to evaluate for translation and stability. Greater than 50% translation is considered unstable.^1,8

Computed tomography (CT) scan is more sensitive for spondylolysis and can be used for surgical planning and monitoring of patients after intervention.^1,3 Magnetic resonance imaging (MRI) can be used to evaluate degenerative disc disease related to spondylolisthesis, but is less helpful in assessing par defects.

In pediatric populations, where stress fractures of the pars interarticularis are likely, a bone scan with single-photon-emission computed tomography (SPECT) can help determine healing potential. Increased uptake of the tracer in the area of the pars is suggestive of osseous activity and, therefore, increased healing potential. Radiographic evidence of a pars defect without increased signal suggests a non-union and could be an indication for surgical management.^1,8

Classification

The Wiltse-Newman Classification is used to catalog spondylolisthesis base on pathophysiology.⁴

• I -- Dysplastic - Congenitally acquired abnormalities
• II -- Isthmic - Lesion involving the pars interarticularis
  • A - Stress fracture
  • B - Elongated Pars
  • C - Acute, traumatic pars fracture
• III -- Degenerative - Secondary to disc disease and osteoarthritis of the facet joints
• IV -- Traumatic - Fractures to the spine not involving pars interarticularis
• V -- Pathologic - Primary bone disease or secondary causes such as metastatic lesion or infection

The Meyerding Classification quantifies the anterior translation of the superior vertebral body and can be used to evaluate the stability of the spine, as well as determine treatment plans. Slip percentage is calculated by dividing the distance from the posterior edge of the superior end plate of the inferior vertebral body to the posterior edge of the inferior end plate of the listhetic vertebral body by the total length of the superior end plate of the inferior vertebral body.⁸

• Grade I -- 0-25% slip
• Grade II -- 26-50% slip
• Grade III -- 51-75% slip
• Grade IV -- 76-99% slip
• Grade V -- 100% or greater slip (spondyloptosis)

Treatment

Medical Therapy

For the pediatric patient, activity modification and exercise focusing on reducing lumbar lordosis and hamstring contraction is the first line of treatment. Additionally, provoking physical activity and sports should be avoided. Symptomatic children with potential to heal their pars defect based on SPECT should be treated with a spinal orthotic designed to reduce lumbar lordosis. Ideally, the brace should be worn full time for 3 months with activity modification, followed by 3 months of wear with activity. Most children (more than 80%) treated conservatively have resolution of their back pain.¹

Adults are also likely to get better with nonoperative treatment consisting of non-steroidal anti-inflammatory drugs, activity modifications, and rest.³ Physical therapy focused on hamstring stretching, core strengthening and decreasing provoking activities can also be useful. Additionally, adults with radicular symptoms may benefit from steroid injections to the affected nerve root or defective pars interarticularis.^1,3

Operative Treatment

Operative treatment for adults with spondylolisthesis has focused on decompression or fusion with and without instrumentation. A review of randomized controlled clinical trials and observational studies showed a higher likelihood of satisfactory clinical outcome with fusion compared to decompression. However, there was no significant difference in the clinical outcome in patients who were fused without instrumentation compared to those who received instrumentation. Still, patients who received instrumented fusion had higher fusion rates and were less likely to develop pseudoarthrosis.⁹

Indications and contraindications

Surgical stabilization is indicated in patients with unstable spondylolisthesis (grade III or higher), as well as lesser grades that demonstrate dynamic translation on flexion and extension radiographs. Progression of the grade of spondylolisthesis over time and cauda equina syndrome are also indications for surgical intervention. Patients who fail conservative non-operative management are also surgical candidates.^3,11

Complications

The most common surgical treatment for lumbar spondylolisthesis is lumbar fusion. This procedure is generally considered safe, with reported mortality rates from 0.15% to 1.3%.^3,10 Commonly reported complications from lumbar fusion for spondylolisthesis include hematomas and seromas occurring in up to 5% of patients. However, the clinical significance of these complications is unknown, as they may be incidental findings.

More significant are the risks of cardiac, renal, and pulmonary complications as a general risk of undergoing surgery. These medical complications were found in up to 6% of patients undergoing spinal fusion for spondylolisthesis and were more common in older patients. Risk of neurologic complication, infection, and thromboembolism are relatively rare, each occurring in less than 1 in 100 procedures.¹⁰

Pseudoarthrosis, or failure of fusion, is a common complication in pediatric patients undergoing posterior spinal fusion for spondylolisthesis. This complication is more common in patients who undergo in situ fusion, patients with higher-grade slips, and those who were inadequately immobilized in the post-operative period. However, evidence of pseudoarthrosis post-operatively is not necessarily correlated with poor clinical outcomes. Therefore, patients should only undergo a revision surgery if the pseudarthrosis is symptomatic.¹¹

Neurologic injury is always a consideration in spinal surgery. Fortunately this complication is rare during in situ fusion of low-grade spondylolisthesis. However, significant risk for neurologic injury exists for patients who undergo reduction and fusion of high-grade spondylolisthesis in an effort to restore sagittal balance. Intraoperative neurophysiologic monitoring, nerve root decompression, and controlled reduction can help to minimize the risk of neurologic injury during a reduction and fusion procedure.¹¹

References

1. Hu SS, Tribus CB, Diab M, Ghanayem AJ. Spondylolisthesis and Spondylolysis. J Bone Joint Surg Am. 2008;90:656-671.
2. Kalichman L, Kim DH, Li L, Guermazi A, Berkin V, Hunter D. Spondylolysis and Spondylolisthesis. Spine. 2009;34:199-205.
3. Jones TR, Rao RD, Adult Isthmic Spondylolisthesis. J Am Acad Orthop Surg. 2009;17:609-617.
4. Cavalier R, Herman MJ, Cheung EV, Pizzutillo PD. Spondylolysis and Spondylolisthesis in Children and Adolescents: I. Diagnosis, Natural History and Nonsurgical Management. J Am Acad Orthop Surg. 2006;14:417-424.
5. Aono K, Kodayashi T, Jimbo S, Atsuta Y, Matsuno T. Radiographic Analysis of Newly Developed Degenerative Spondylolisthesis in a Mean Twelve-Year Prospective Study. Spine. 2010;35:887-891.
6. Been E, Li L, Hunter DJ, Kalichman L. Geometry of the vertebral bodies and the intervertebral discs in lumbar segments adjacent to spondylolysis and spondylolisthesis: pilot study. Eur Spine J. 2011;20:1159-1165.
7. Jacobsen S, Sonne-Holm S, Rovsing H, Monrad H, Gebuhr P. Degenerative Lumbar Spondylolisthesis: An Epidemiological Perspective. Spine. 2007;32:120-125.
8. Meyerding HW. Spondylolisthesis. Surg Gynecol Obstet. 1932;54:371-377.
9. Martin RC, Gruszczynski AT, Braunsfurth HA, Fallatah SM, O’Neil J, Wai EK. The Surgical Management of Degenerative Lumbar Spondylolisthesis. Spine. 2007;32:1791-1798.
10. Kalanithi PS, Patil CG, Boakye M. National Complications Rates and Dispositions After Posterior Lumbar Fusion for Acquired Spondylolisthesis. Spine. 2009;34:1963-1969.
11. Cheung EV, Herman MJ, Cavalier R, Pizzutillo PD. Spondylolysis and Spondylolisthesis in Children and Adolescents: II. Surgical Management. J Am Acad Orthop Surg. 2006;14:488-498.