15 Spinal Stenosis with Spondylolisthesis
KEY POINTS
Spinal stenosis accompanied by spondylolisthesis is a common diagnosis encountered by the spinal surgeon. Although nonoperative treatment consisting of antiinflammatory medications and epidural steroid injections is effective in some patients, many patients with severe symptoms are not helped by this strategy.1,2 In the group that fails conservative therapy, decompression has been shown to be an effective treatment modality.2–4 Although numerous studies have clearly demonstrated the beneficial effects of decompressive laminectomy, the fear of creating instability often limits this procedure’s application. The concomitant presence of spondylolisthesis increases this likelihood. Controversy also persists regarding the virtues of concomitant spinal fusion in this patient population, which is often elderly. When fusion is chosen, the decision of whether or not to use instrumentation must be made. Fortunately, the management of this condition has evolved over the past several decades and numerous prospective randomized trials have been performed assessing the influence of fusion and instrumentation following decompression.
Part One: Understanding the Condition
Pathophysiology
As the spine ages, the accumulation of years of axial loading and rotational strains may lead to disc degeneration, facet arthrosis with hypertrophy, thickening or buckling of ligamentum flavum, and osteophyte formation. This cascade of degenerative changes can result in the development of central canal or foraminal narrowing with resulting neural compression characterized by low back, buttock, and lower extremity pain.1 They can also result in varying degrees of spinal instability and, depending on the anatomic predisposing factors, the vertebra develops either anterolisthesis or retrolisthesis. Spondylolisthesis, the slippage of one vertebra relative to the adjacent vertebrae, often results from asymmetric degeneration of the disc, the facet joints, or both.
Natural History
The majority of patients with a history of significant neurogenic claudication or vesicorectal symptoms have been shown to have poor outcomes without intervention. A prospective observational cohort study assessing the long-term outcomes (8- to 10-year follow-up) of patients with lumbar spinal stenosis treated either surgically or nonsurgically has demonstrated increased leg pain relief and greater back-related functional status in patients who initially received surgical treatment. Although degenerative spondylolisthesis has been shown to progress in 25% to 30% of patients, it fortunately rarely progresses to more than 30% of the subjacent vertebra. Some studies have demonstrated that as the pathology progresses and the disc space collapses, back pain can improve spontaneously.
Part Two: Clinical Decision Making
Specific Patient Populations and Situations
Elderly
Some controversy exists as to whether age should be considered an independent risk factor for surgery. Many authors report no difference in outcome or rate of complications between elderly and younger patients of comparable health.7 Therefore advanced age alone should not be a contraindication for surgery. Some studies, on the other hand, have demonstrated that increasing age can be an independent risk factor for surgery, especially if the patient is older than 60 years.5 One such study noted a 41% complication rate (14% major and 27% minor) for patients 41 to 60 years of age and a 64% complication rate (24% major and 40% minor) for those 61 to 85 years of age (27). Pulmonary complications were the most common major complications and genitourinary problems were the most common minor complications. Age more than 60 years was therefore found to be a significant risk factor for perioperative complication.
It has also been reported that decompressive surgery in the elderly population can be effective without the need for supplemental fusion, and many authors therefore do not recommend fusion in patients older than 70 years. This is partly because the risk of developing postoperative instability in this age group appears to be small because of some intrinsic stability afforded by the spondylosis and spondylarthrosis that occur as the spine ages as well as the decreased activity level of this population.5
Multiple Comorbidities
Patients who have multiple comorbidities, such as cardiac disease, vascular disease, or diabetes have an increased risk for postoperative complications.6,7 The preoperative evaluation and optimization of patients with these conditions is critical. The addition of an arthrodesis increases the length of anesthesia as well as the amount of blood loss. Both of these factors can delay recovery time, and patients with multiple comorbidities are therefore more likely to require an extended rehabilitation period. These factors should all be considered when deciding upon the advisability of supplemental fusion with decompression. Finally, for patients with a limited life expectancy, treatment should be focused on obtaining an immediate improvement in quality of life without subjecting the patient to a prolonged and painful recovery period.
Several studies in the literature have examined the relationship between preoperative comorbidities and postoperative complications. Although there is a link between certain risk factors and postoperative mortality, increasing American Society of Anesthesiology (ASA) physical status class has been shown to be one of the best independent predictors of mortality. Previous studies have reported an increasing rate of postsurgical mortality with increase in the ASA class. In fact, increasing morbidity and mortality rates have been prospectively demonstrated with an increase in the ASA class in a large population where the mortality rate increased from zero to 7.2% from ASA class 1 to ASA class 4, respectively.7