Spondylolisthesis

Spondylolisthesis is the forward (or, less commonly, backward) slippage of one vertebra relative to the one below it. The two principal adult forms are isthmic spondylolisthesis, due to a defect in the pars interarticularis, and degenerative spondylolisthesis, due to facet and disc degeneration that allows the vertebra to slip while the neural arch remains intact. It is a common cause of mechanical back pain and, when it narrows the canal, of neurogenic leg symptoms.

Definition

Spondylolisthesis is anterior or posterior translation of one vertebral body on the adjacent vertebra, classified by cause (most commonly isthmic, from a pars defect, or degenerative, from facet and disc degeneration) and graded by the degree of slip.

Scope

This topic covers the main types and grading of vertebral slippage, the mechanisms that allow a vertebra to translate, the associated symptoms, and the comparative evidence on management, including the question of whether fusion should be added to decompression. It is a reference description and not individual clinical guidance.

Core questions

• What distinguishes isthmic from degenerative spondylolisthesis?
• How is the severity of a slip graded and why does grade matter?
• How does slippage produce mechanical back pain and neural compression?
• When does decompression need to be combined with fusion?

Key concepts

• Isthmic versus degenerative spondylolisthesis
• Pars interarticularis defect (spondylolysis)
• Meyerding grading of slip severity
• Segmental instability
• Associated central and foraminal stenosis
• Decompression with versus without fusion

Mechanisms

In isthmic spondylolisthesis a defect in the pars interarticularis (spondylolysis) interrupts the bony restraint of the neural arch, allowing the vertebral body to slide forward. In degenerative spondylolisthesis the neural arch is intact, but degeneration and remodelling of the facet joints together with disc-height loss reduce segmental stability and permit slippage, most often at L4-L5 (Kalichman & Hunter, 2008). Slippage can stretch and compress neural elements and narrow the canal and foramina, producing back pain and neurogenic leg symptoms. The degree of slip is commonly described with the Meyerding grading, which divides the slip into quartiles of the vertebral endplate width (Meyerding, 1934).

Clinical relevance

Degenerative spondylolisthesis is a frequent indication for lumbar surgery and is the setting for one of the field's central debates about adding fusion to decompression, making it important for understanding surgical decision-making in degenerative spine disease. This entry is a reference description and not a basis for individual diagnosis or treatment decisions.

Epidemiology

Degenerative spondylolisthesis is more common in older adults, occurs more often in women, and is most frequent at the L4-L5 level; isthmic spondylolisthesis typically presents earlier and is associated with a pars defect (Kalichman & Hunter, 2008).

Evidence & guidelines

The SPORT degenerative spondylolisthesis cohort found greater improvement with surgery than with non-operative care, with the usual caveat of crossover between arms (Weinstein et al., 2007). Whether decompression should be supplemented by fusion has been examined in randomized trials with differing conclusions; one trial reported a benefit of adding fusion (Ghogawala et al., 2016), while other contemporaneous evidence questioned the routine addition of fusion, leaving the issue actively debated.

History

The grading of vertebral slip by quartiles described by Meyerding in 1934 remains the standard descriptive scheme for severity (Meyerding, 1934). The clinical study of spondylolisthesis advanced from anatomical description to comparative-effectiveness research, with the degenerative form featuring prominently in modern trials of surgical versus non-surgical care and of decompression with versus without fusion (Weinstein et al., 2007; Ghogawala et al., 2016).

Debates

Should decompression be combined with fusion in degenerative spondylolisthesis?

Randomized trials have reached differing conclusions, with one supporting the addition of fusion to improve outcomes and others questioning its routine use given added cost and morbidity, so the indication for fusion remains contested.

Key figures

• Henry William Meyerding
• Leonid Kalichman
• James Weinstein
• Zoher Ghogawala

Seminal works

• meyerding-1934
• weinstein-2007-spondylo
• ghogawala-2016

Frequently asked questions

What is the difference between isthmic and degenerative spondylolisthesis?

Isthmic spondylolisthesis results from a defect in the pars interarticularis that allows the vertebra to slip, while degenerative spondylolisthesis occurs with an intact neural arch as facet and disc degeneration reduce segmental stability, typically in older adults.

Does a slipped vertebra always need fusion surgery?

No. Many people are managed without surgery, and even when surgery is done the role of adding fusion to decompression is debated, with randomized trials reaching differing conclusions; the decision depends on factors such as instability and symptoms.