16

Herbiniaux, a Belgian obstetrician, is generally credited with the first description of spondylolisthesis as a pathological entity in 1782,1 whereas the term spondylolisthesis, from Greek for “slipped spine,”² was coined by Killian in 1853.³ Spondylolisthesis refers to displacement of one vertebra with respect to its adjacent vertebrae. In most cases, the superior vertebra translates forward on the inferior vertebra, causing an anterolisthesis.⁴

The most widely utilized clinical grading scale for spondylolisthesis was developed by Meyerding in 1932. For this purpose, the superior end plate of the lower vertebral body, usually the first sacral vertebra, is divided into four equal segments. The degree of subluxation corresponds to the number of segments that the upper vertebral body is translated relative to the one below. A single grade is assigned for a forward slip that spans each segment.³

The most commonly accepted classification system of spondylolisthesis was described by Wiltse, Newman, and Macnab in 1976 (Table 16.1). The scheme is based on anatomical as well as etiologic features and is composed of dysplastic, isthmic, degenerative, traumatic, and pathological categories.⁵ The focus of this chapter is adult low-grade symptomatic isthmic spondylolytic spondylolisthesis.

The pathophysiology of isthmic spondylolisthesis is a defect within the pars interarticularis or spondylolysis, which is thought to arise from repeated fractures followed by healing and remodeling.⁶ The Wiltse–Newman–Macnab classification recognized three subtypes of isthmic spondylolisthesis. Subtype A, also known as lytic, is thought to be due to a fatigue fracture early in life of a congenitally weakened pars interarticularis. The pars defect is usually filled with cartilage/fibrous tissue. Subtype B is characterized by elongation of the pars without a true defect. It is thought to be due to a fracture of the pars that had healed in an elongated position, thereby allowing the vertebral body to slip forward. Subtype C is an acute fracture within the pars.⁵

The epidemiology of spondylolysis and spondylolis-thesis has been the subject of numerous studies over the past century, and several prospective studies exist in the literature. The pathology is very rare in young children up to 2 years of age, 4.4% at age 5 to 7, increasing to 6% at age 18.⁷ österman et al⁸ prospectively evaluated 1147 subjects of 45 to 64 years of age and found isthmic spondylolisthesis in 6% with a slight male predominance. The lesion was observed at L5 in 86% of the cases, with the majority of remaining cases at L4. Ninety-nine percent of subjects had a low-grade slip (Meyerding grades I and II).

Beutler et al prospectively followed 30 individuals with a pars defect from age 5 to 50 years, and these individuals were found to have pain or disability similar to that of the general population. The authors found no association of slip progression with low back pain. Moreover, there was no statistically significant difference between the study population’s SF-36 scores and those of the general population of the same age. Kalichman et al¹⁰ performed a cross-sectional study to evaluate the association of isthmic spondylolisthesis with low back pain and found no significant association.

Table 16.1 Classification of Spondylolisthesis by Wiltse, Newman, and Macnab

Radiographic slip progression in the adult has long been considered unusual and clinically insignificant. The percentage of slip, the slip angle, the lumbar index, and the amount of disk degeneration have all been considered as potential predisposing factors to subsequent radiographic slip progression. However, none of these parameters has been proven to clearly predict the clinical picture, and the degree of progression has never been correlated with the onset or presence of pain.11 The only factor correlating to increased slip is progressive disk degeneration.

This chapter assesses the evidence for the effectiveness of conservative versus surgical management of symptomatic adult low-grade isthmic spondylolytic spondylolisthesis. Multiple databases were searched, and studies pertaining to the subject were reviewed. The Cochrane Library identified two level I studies, both by the same group. The Medline database was searched using the terms “adult spondylolisthesis,” and 180 studies were evaluated. The majority of studies dealt with the pediatric population, specific surgical treatments, or the natural history of the disease. Review articles were used as a reference to identify additional studies. Fifty-six studies were identified based on the relevance of the content, of which only six were pertinent to this discussion. Only three studies addressed conservative management and were included in this review. The level of evidence of the studies is summarized in Table 16.2.

Table 16.2 Level of Evidence of Published Studies

A search of the current literature revealed only two randomized, controlled trials comparing conservative versus surgical treatment for adult low-grade isthmic spondylolytic spondylolisthesis. Möller and Hedlund in 2000 published their report comparing posterolateral fusion in patients with adult isthmic spondylolisthesis to an exercise program.12 One hundred eleven symptomatic patients with radiographically verified diagnosis of spondylolisthesis were randomized. The surgical intervention consisted of posterolateral fusion in situ (40 patients) as one group and fusion with transpedicular instrumentation without reduction (37 patients) as another group. Thirty-four patients were randomized to an exercise program. The exercise group was compared with the combined surgical group. The inclusion criteria were individuals 18 to 55 years of age, presence of lumbar isthmic spondylolisthesis of any grade (98% had grade I or II), at least 1 year of low back pain or sciatica, and severely restricted functional ability. Patients with previous back surgery, mild symptoms, and substance abuse history were excluded from the study. The Disability Rating Index (DRI), which is composed of 12 functional visual analogue scales, and pain scales were used to quantify the patients’ response to treatment. Outcomes were assessed before treatment onset and at 1- and 2-year follow-up. The final outcome data were available for 93% of the study participants.

The authors found a statistically significant benefit with surgical intervention (in situ and transpedicular fusion groups were analyzed as one cohort). Although both groups showed improvement, the surgical group showed significant improvement in all DRI (p = 0.004) and pain indices (p = 0.002) over an exercise program. There were also fewer patients on sick leave or disability pension after surgical intervention (p < 0.0001).

Overall, this study was carefully constructed and executed. The authors had clearly defined the aim of the study. Each group had sufficient power to detect a clinically relevant difference in functional outcome, and both subjective and objective variables were assessed. The two groups were similar in demographics and other patient-specific factors. The study showed a high retention rate and minimal crossover.

A major criticism of this study is the treatment option chosen for the nonoperative group. A multimodality approach is generally accepted and consists primarily of activity modification, bracing, physical therapy, and interventions such as medications or injections.¹³ It is presumed that the authors had chosen the exercise program alone to provide for a more homogeneous treatment group. But the question remains whether the nonoperative group received suboptimal treatment. In his letter to the editor, Mooney commented on the validity of the exercise program utilized in this study. He cautioned that the study did not provide any information regarding the results of the strength-training program or some method of monitoring progress in a standardized objective manner.14

In 2004 Eckman et al reported on long-term outcome data from the same patient groups. They concluded that postero-lateral fusion in adult lumbar isthmic spondylolisthesis results in a modestly improved long-term outcome compared with an exercise program. Although the results showed that some of the previous reported short-term improvement is lost at long term, patients in the surgical group still classified their global outcome more favorably than the conservatively treated patients did. Seventy-six percent of patients in the surgical group considered the overall outcome as much better compared with 50% of conservatively treated patients (p = 0.015).¹⁵

O’Sullivan et al published a prospective randomized, controlled trial comparing outcomes in a group receiving specific truncal stabilizing exercises to a control group treated with a general exercise program, in patients with chronic low back pain and a radiologic diagnosis of spondylolysis and spondylolisthesis.¹⁶ The authors hypothesized that the stabilizing exercises would strengthen deep abdominal muscles and lumbar multifidus and would impart greater stability to the spine thereby counteracting instability caused by spondylolysis and spondylolisthesis. Forty-four patients between the ages of 16 and 49 were included in the study. In all patients the symptoms had been present longer than 3 months without relief. Outcomes were measured using various pain scales, the Oswestry Functional Disability questionnaire, standing lumbar spine and hip sagittal range of movement, and abdominal muscle recruitment patterns. Patients were assessed prior to onset of treatment, at 3, 6, and 30 months follow-up after beginning the different exercise programs. Individuals in the special stabilizing exercise program underwent a 10-week treatment program directed on a weekly basis by an experienced physiotherapist. The control group underwent a 10-week treatment directed by each patient’s medical practitioner consisting of swimming, walking, and gym work. Forty-two patients completed the study.

At the onset of the study, statistical analysis did not show any significant differences between the groups. Analysis of differences within each group after the intervention revealed significant improvement in the special exercise group but not in the controls. The exercise group experienced a decrease in pain intensity (p < 0.0001), functional disability levels (p = 0.0001), total amount of analgesics of nonsteroidal antiinflammatory drug (NSAID) intake, and the use of transcutaneous nerve stimulation. The control group did not show significant change in any parameters analyzed after treatment. When differences between the groups were analyzed based on the degree of change in each group after intervention, a statistically significant difference was observed in reduction of pain intensity (p < 0.0001) and functional disability (p < 0.0001) in the special exercise group when compared with the control group. With regard to the lumbar spine sagittal mobility, no significant difference was observed within or between groups. Analysis of the follow-up data revealed lasting benefit in favor of the special stabilizing exercise group with regard to pain intensity (p = 0.0006) and Oswestry Functional Disability scores (p = 0.0481) at 30-months follow-up.

The authors concluded that the specialized stabilizing exercise program offered a sustained reduction in symptoms and functional disability level over the general exercise program at 3-, 6-, and 30-month follow-ups. In addition, patients in the special stabilizing exercise program reported a reduced need for medication and medical treatment need as compared with the control group.¹⁶

Level II Data

There are no level II data published regarding this topic.

Level III Data

Daniel et al¹³ reported their experience with nonoperative management of spondylolysis at the Walter Reed Medical Center in 1995. In their retrospective chart review analysis, 29 patients ages 13 to 31 were identified. Inclusion criteria were radiographic documentation of lumbar spondylolysis, symptoms with a discrete onset of low back pain, and a minimum of 4 months of nonoperative treatment. Treatment included activity modification, full-time thoracolumbosacral orthosis, NSAIDs, and narcotic analgesics when indicated. Success was defined as no pain with ad lib activity and radiographic evidence of healed pars defect.

In this series, only two out of 29 patients had a good outcome after nonoperative treatment; the remaining group underwent surgical repair of the pars interarticularis. The surgical outcomes are not discussed in the study. The authors speculate that the high rate of failure of nonoperative treatment was due in part to the delay in diagnosis that led to the development of fibrous nonunion and failure of non-operative managment.

Sinaki et al¹⁷ conducted a retrospective analysis of two conservative treatment programs with a 3-year follow-up. The authors hypothesized that spondylolysis and spondylolis-thesis are the consequence of stresses exerted by the lordotic curvature of the lumbar spine. Their argument was based on the fact that apes lack lordotic curvature and do not develop such pathologies.

In this study, 48 patients with lumbar spondylolisthesis randomly received flexion or extension exercises. The great majority of patients had Meyerding grade I spondylolisthesis. The two groups were comparable in age, gender, height, weight, and duration of symptoms. Patients were evaluated with respect to pain relief, work status, the need for back support, and the need for operation. Follow-up data were available for 44 patients (92%) and were obtained at 3 months and 3 years.

On follow-up evaluation, the differences between the two groups were significant. Evaluation of pain at 3 months demonstrated mild or no pain in 73% of the flexion group and 33% of the extension group. At 3 years, 81% of the flexion group had minimal or no pain compared with only 33% of the extension group with similar findings for return to work status. Of the subjects in the flexion group, 68% were working at 3 months follow-up with 76% at 3 years. In the extension group, 39% had returned to work at 3 months, without any further increase at 3 years. From the patients’ point of view, 58% of the flexion group considered themselves recovered at 3 months, and 62% at 3 years. Of the subjects in the extension group, only 6% considered themselves recovered at 3 months, and this number dropped to zero at 3 years. Based on these findings, the authors concluded that flexion exercises are superior to extension exercises. The findings support the authors’ argument that flexion exercises strengthen the muscles that counteract the forces of lordotic lumbar spine, thereby imparting greater stability and relief of symptoms.17

Kwon et al¹⁸ performed a critical analysis of the literature regarding surgical approach and outcome of adult low-grade isthmic spondylolisthesis. The objective of the analysis was to determine whether conclusions could be made as to the optimal choice for a surgical procedure in the management of symptomatic adults with low-grade isthmic spondylolis-thesis. The authors identified 34 studies in which anterior, posterior, or combined fusion procedures were described. Only four of these were prospective, randomized, controlled studies with minimum 24-month follow-up that compared one form of treatment against another. The remaining studies were of level III evidence. A true meta-analysis was not possible due to significant heterogeneity of the studies. The data were pooled from all of these studies to assess whether the rate of radiographic fusion and the rate of clinical success were influenced by the surgical approach. The total combined patient population was reported at over 1100 patients.

The authors found that patients with combined anterior and posterior procedures had the highest radiographic fusion rate and the best clinical outcome. Moreover, fusion rates and clinical success were higher with the use of instrumentation, whereas smoking had the opposite effect.

Summary of Data

There is a limited amount of level I data directly comparing the outcomes of conservative treatment with surgery. There are only two level I studies available. There are three level III studies evaluating conservative treatment and one level III analysis of pooled data of the surgical management. The best available evidence suggests that surgical intervention is indicated in symptomatic patients with low-grade isthmic spondylolisthesis who have failed an initial course of conservative therapy. Based on the grading scale proposed by Fisher et al, the data support such a recommendation at the level of grade IB—a strong recommendation, likely to apply to most patients.¹⁹

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