Classification of Spondylolisthesis

Numerous spondylolisthesis classification schemes exist. These generally describe spondylolisthesis according to anatomy and etiology. The two most commonly used classification systems are the Wiltse-Newman and Marchetti-Bartolozzi.

The Wiltse-Newman classification divides spondylolisthesis into five categories: dysplastic, isthmic, degenerative, traumatic, and pathologic ( Table 152-1 ). Isthmic spondylolisthesis is further subdivided into three subtypes.

The Marchetti-Bartolozzi scheme divides spondylolisthesis into acquired and developmental forms ( Table 152-2 ). Acquired spondylolisthesis is further categorized as degenerative, iatrogenic, traumatic, and pathologic. The developmental forms include low-grade and high-grade dysplasia. The classification of spondylolisthesis is important, as the underlying cause and anatomy are primary factors in determining treatment.

Spondylolisthesis can also be graded according to the degree of slip present. The Meyerding system is the most widely used grading method. There are four grades of increasing severity: grade 1 is 0 to 25% slippage, grade 2 is 26% to 50% slippage, grade 3 is 51% to 75% slippage, and grade 4 is 76% to 99% slippage ( Fig. 152-1 ). Less than 50% slippage (grades 1 and 2) is considered low grade, whereas high-grade spondylolisthesis is slippage of greater than 50% (grades 3 and 4). Complete or 100% spondylolisthesis is referred to as spondyloptosis (grade 5).

Meyerding Spondylolisthesis Grading System.

Grade 1: 0 to 25% slip; grade 2: 26% to 50% slip; grade 3: 51 to 75% slip; grade 4: 76% to 99% slip.

Types of Spondylolisthesis

Lumbar spondylolisthesis can result from a variety of etiologies and is often multifactorial. The shared defect, however, is vertebral slippage due to loss of normal structural support. The interarticular facets, lamina, pars, pedicles, and vertebral discs are the key elements that prevent slippage.

Clinical Presentation

Younger patients tend to present with back pain and a history of activities that involve repetitive hyperextension such as gymnastics, wrestling, weight lifting, and diving. Adult patients typically present with axial back and leg pain. The back pain is usually mechanical and positional. The pars interarticularis defect, intervertebral discs, and facets are common pain generators. However, discomfort can also come from soft tissues (i.e., muscle, ligaments) or nerve root irritation. Leg pain is usually radicular when associated with isthmic spondylolisthesis as a result of foraminal height loss and impingement of the exiting nerve root by hypertrophic fibrous tissue immediately surrounding the defect in the pars interarticularis or degenerated disc. Neurogenic claudication is more common in degenerative spondylolisthesis. Ventral slippage narrows the canal and foramen, leading to spinal stenosis. In addition, degenerative changes including hypertrophic facets and ligamentum flavum further contribute to central, lateral recess and foraminal stenosis that can cause claudication. Neurogenic claudication is characteristically described as bilateral buttock cramping and thigh pain with leg “fatigue.” This generally improves with flexion and rest.

On physical examination, isthmic spondylolisthesis patients often demonstrate hamstring tightness as the pelvis retroverts to compensate for the lumbosacral kyphosis. Hamstring tightness can result in a waddling gait as the patient is unable to fully extend the hip. Neurologic impairment including sensory dysfunction and focal weakness can be seen.

Imaging

Standing lateral radiographs will show the vertebral slip and are useful for determining the degree of slippage, the slip angle, the degree of lordosis, and sagittal alignment. Flexion and extension radiographs can sometimes be helpful in cases of dynamic instability but are not necessary. Oblique radiographs allow for better visualization of pathology within the pars interarticularis. In cases of high-grade slips with compensatory pelvic verticalization, a “heart-shaped” pelvis is often seen.

Advanced imaging such as computed tomography (CT) scans and magnetic resonance images (MRIs) provide better visualization of the dorsal element anatomy including dysplasia. These also better assess the degree of canal or foraminal stenosis, facet widening, end plate degenerative changes, sagittal facet orientation, synovial cysts, and facet sclerosis.

Nonsurgical Treatment

All patients presenting with spondylolisthesis should initially be treated with a course of nonsurgical management. The modality of treatment and its success depends on several factors including the type of spondylolisthesis as well as age.

In skeletally immature patients, a low-grade slip should be observed with serial radiographs every 6 months until skeletal maturity. Symptomatic patients should have activities restricted with consideration of bracing. Soft corsets, hard “clamshell” lumbosacral orthoses, and formal casting have all been used successfully in adolescent patients with an acute spondylolysis. Adolescent patients with high-grade slips or a high slip angle are at risk for progression and are offered surgery.

In general, anti-inflammatory medications, activity modification, physical therapy, bracing, and spinal injections are the mainstays of nonsurgical management. Formal physical therapy focuses on flexion based exercises that limit forces across a painful spondylolysis or facet and increase neural canal and foraminal dimensions. Lumbar traction is of variable benefit and may provide a counter to associated muscle spans. The best benefits are derived in acute (< 6 weeks of symptoms) situations.

Steroid injections may target a pars interarticularis defect, facet, epidural space, or nerve root. Epidural steroid injections can be of significant benefit to radicular leg pain. A series of up to four injections in concert with other treatments can allow patients who would otherwise be considered surgical candidates to avoid surgery.

Obese patients with a body mass index of greater than 30 should be encouraged to undergo a structured weight-loss program, as obesity has been linked to higher rates of infection, reoperation, and less clinical postoperative improvement. Although nonoperative treatment is often helpful, it has been shown to be less effective than surgery in the long term.