Spondylolisthesis is the anterior or posterior displacement of a vertebra or the vertebral column in relation to the vertebrae below. The variant “listhesis,” resulting from misdivision of this compound word, is sometimes applied in conjunction with scoliosis. These “slips” (aka “step-offs”) occur most commonly in the lumbar spine. Spondylolysis (a defect or fracture of the pars interarticularis of the vertebral arch) is the most common cause of spondylolisthesis. This is not to be confused with a slipped disc, where one of the spinal discs in between the vertebrae has ruptured.
A hangman’s fracture is a specific type of spondylolisthesis where the C2 vertebra is displaced anteriorly relative to the C3 vertebra due to fractures of the C2 vertebra’s pedicles.
General stiffening of the back and a tightening of the hamstrings, with a resulting change in both posture and gait. A leaning-forward or semi-kyphotic posture may be seen, due to compensatory changes. A “waddle” may be seen in more advanced causes, due to compensatory pelvic rotation due to decreased lumbar spine rotation. A result of the change in gait is often a noticeable atrophy in the gluteal muscles due to lack of use.
MRI of L5-S1 Spondylolisthesis
Generalized lower-back pain may also be seen, with intermittent shooting pain from the buttocks to the posterior thigh, and/or lower leg via the sciatic nerve. Additional symptoms may include tingling and numbness. Coughing and sneezing can intensify the pain. An individual may also note a “slipping sensation” when moving into an upright position. Sitting and trying to stand up may be painful and difficult.
Isthmic spondylolisthesis refers to spondylolisthesis due to degeneration of the pars interarticularis. When symptomatic, patients with symptomatic low-grade (<50 percent slippage) isthmic spondylolisthesis typically present with activity-related back pain and often with radicular symptoms as well.
Patients with low grade spondylolisthesis are usually young adults (90 percent adults and 10 percent adolescents) who present with low back pain and often with radiculopathy. High grade spondylolisthesis may also present with back pain, but may also present with cosmetic deformity, hamstring tightness, radiculopathy, abnormal gait, or it may be asymptomatic.
X-ray of a grade 4 spondylolisthesis at L5-S1 with spinal misalignment indicated
High-grade isthmic spondylolisthesis and dysplastic spondylolisthesis are regarded as separate clinical entities from low-grade isthmic slips. High-grade slips are defined as those with greater than 50 percent forward displacement. These slips are also accompanied by a significant amount of lumbosacral kyphosis, which is forward bending of the L5 vertebral body over the sacral promontory. Rounding of the sacral body and trapezoidal deformation of L5 are also common features. High-grade slips are much rarer than low-grade slips, representing less than 10 percent of all isthmic slips, and the vast majority present during adolescence, most during the early teenage years.
Unlike low-grade slips, many patients present without pain. Instead symptoms like bodily deformity, neurologic abnormalities, tight hamstrings, and abnormal gait are often the reason for consultation.
Patients with isthmic spondylolisthesis almost universally have a neural arch defect, meaning widening of the central spinal canal at the level of the slip. In contrast, in degenerative spondylolisthesis the forward translation of the vertebral body also causes narrowing of the central spinal canal at the level of the slip, termed the “napkin ring effect” depecting the spinal canal as a series of napkin rings with one of the rings slid forward in comparison to the others. The classic symptomology of patients with symptomatic degenerative spondylolisthesis are similar to those with symptomatic lumbar spinal stenosis; either neurogenic claudication or radiculopathy (either unilateral or bilateral radiculopathy) with or without low back pain.
Neurogenic claudication is thought to result from central canal narrowing that is exacerbated by the listhesis (forward slip). The classic symptoms of neurogenic claudication are bilateral (both legs) posterior leg pain that worsens with activity, but is relieved by sitting or forward bending.
The appropriate treatment of patients with isthmic spondylolisthesis is controversial. For the purposes of treatment and study, patients with isthmic spondylolisthesis are usually divided into two general classes: low grade isthmic spondylolisthesis (<50 percent slip) and high grade isthmic spondylolisthesis (>50 percent slip).
Patients with symptomatic isthmic spondylolisthesis are initially offered conservative treatment consisting of activity modification, pharmacological intervention, and a physical therapy consultation.
Degenerative spondylolisthesis with spinal stenosis is one of the most common indications for spine surgery among older adults, and current evidence suggests that patients have much better success rates and more clinical benefit with decompression and fusion than with decompression alone.