Spondylolisthesis (plural: spondylolistheses) is the slippage of one vertebra relative to the one below. It can occur anywhere in the spine, but is most commonly seen in the lumbar spine, particularly in association with spondylolysis at L5/S1 and with degenerative changes at L4/L5.
The Wiltse classification scheme (1981) is used to categorise spondylolisthesis on an aetiological basis. 
- Type I is dysplastic/congenital: There is an abnormal neural arch with rounding of the superior ventral surface of the S1 vertebra. This leads to L5 translating anteriorly. This type has the highest progression risk at 32%.
- Type II is isthmic: There is a lesion of the pars interarticularis. Sports-related isthmic type progresses in 4%.
- Subtype II A (lytic): secondary to stress fracture (spondylolysis)
- Subtype II B (elongated pars): secondary to multiple injury and healing cycles leading to an elongated pars
- Subtype II C (acute pars fracture): secondary to a single event and is rare.
- Type III is degenerative: This is when degenerative changes have lead to ligamentous instability affecting the ligamentum flavum, capsule of the facet joints, and other ligaments. The facet joints are then able to slip forward. This generally occurs at L4/5. It is more common in females over 40.
- Type IV is post-traumatic: There is a fracture in a region other than the pars which leads to slippage.
- Type V is pathologic: There is diffuse (generalised bone disease) or local bone disease (e.g. a lytic pars tumour) which compromises the structural integrity. It may appear sclerotic on radiographs.
- Type VI is iatrogenic
Isthmic means movement of one vertebrae on another, due to a defect in the pars, termed spondylolysis (unhealed stress fracture). Spondylolysis can be present without displacement.
Spondylolisthesis occurs in 40-60% of patients with bilateral spondylolysis (unlikely if unilateral). Most are asymptomatic, 25% have back/radicular pain. Prevalence in children is 2.6%, increasing to 4% in adulthood. It is asymptomatic in 3-11% of adults. It is more common in men and at the L5/S1 level. The causes are multifactorial with a genetic component.
Back pain may be from micro-instability or from secondary discogenic pain. Symptomatic patients are treated non-operatively.
Degenerative Lumbar Spondylolisthesis
The incidence is 19-43%, with a mean age of 71, and is most common in females. The most commonly affected segment is L4/5. Most are grade 1 (75%) and less than 25% slip. The average slip progression is 18%,
There may be an initial event - disc degeneration/narrowing of disc space - leading to micro-instability. Any potential cause of pain may be multifactorial. There is no correlation between progression and symptoms
The natural history and management of low grade slip is controversial, conservative management is generally indicated. Surgery may be offered for refractory cases.
High grade lumbar Spondylolisthesis
This is defined as >50% slippage. Most are at L5/S1, as a result of isthmic spondylolisthesis. Most have a degree of neurologic compromise.
Pain usually occurs with hyperextension, and resolves with time due to fracture union.
For natural history it is difficult to predict if further slippage will occur.
Treatment is focused on correction of lordosis and sagittal balance. Conservative management trailed in adolescence, but usually unable to provide permanent relief.
The Meyerding classification is used to classify the severity of slippage. It divides the superior endplate of the caudal vertebra into four quarters. The grade is dependent on the location of the posteroinferior corner of the cephalad vertebra.
- Grade I: 0-25%
- Grade II: 26-50%
- Grade III: 51-75%
- Grade IV: 76-100%
- Grade V (spondyloptosis): >100%
Epidemiology and Relationship to Pain
The prevalence is 8% in men and 5% in women. It can be completely asymptomatic. Men with spondylolisthesis are not more likely to have back pain, however women are slightly more likely to have back pain. The overall odds ratio for it being a cause of pain are around 1.
Non operative treatment is effective in patients without neurogenic claudication or radiculopathy and stable spondylolisthesis (grade 1). One third show progression over time.
Mechanical instability has been defined as a change of 3mm-6mm between flexion/ext films, or change from sitting to standing
There are two recent randomised controlled trials evaluating the surgical treatment of spondylolisthesis, published in the same edition of the NEJM.
- Swedish Spinal Stenosis Study (SSSS): compared decompression with decompression plus fusion for patients with spinal stenosis and neurogenic claudication with and without degenerative spondylolisthesis of at least 3mm of anterior vertebral slippage, n=246. There was no significant difference seen at two years between the groups. The conclusions of the study have been criticised for the heterogeneity, post-hoc analyses, and lack of power.
- Spinal Laminectomy versus Instrumented Pedicle Screw Study (SLIP): compared decompression with decompression plus fusion for patients with degenerative spondylolisthesis of at least 3mm and neurogenic claudication, n=66. The decompression plus fusion group had better outcomes in SF-36 compared to decompression alone (19.5 vs 9.5) after two years, and was sustained at 3 and 4 years. The minimal clinically important difference was reached in 92% of the fusion group versus 76% of the decompression-only group at 2 years, but was not statistically significant. The decompression group had a higher reoperation rate (14% vs 34%) at four years. The study has been criticised for small sample size, 14% lost to follow up at 2 years, and 32% lost to follow up at 4 years. It excluded those with mechanical low back pain.
I am not aware of any randomised controlled trials comparing operative versus non-operative management, or indeed operative versus sham surgery.
Some view nonoperative management has having substantial cost without benefit in those that are potentially suitable for surgical intervention. Lumbar decompression alone can be effective for low grade, and fusion if higher grade.
- Wiltse, Leon L.. “Classification, Terminology and Measurements in Spondylolisthesis.” The Iowa Orthopaedic Journal vol. 1 (1981): 52–57. Full Text
- McPhee IB, O'Brien JP, McCall IW, Park WM. Progression of lumbosacral spondylolisthesis. Australas Radiol. 1981 Mar;25(1):91-5. doi: 10.1111/j.1440-1673.1981.tb02225.x. PMID: 7271629.
- Bhalla A, Bono CM. Isthmic Lumbar Spondylolisthesis. Neurosurg Clin N Am. 2019 Jul;30(3):283-290. doi: 10.1016/j.nec.2019.02.001. Epub 2019 Apr 19. PMID: 31078228.
- Bydon M, Alvi MA, Goyal A. Degenerative Lumbar Spondylolisthesis: Definition, Natural History, Conservative Management, and Surgical Treatment. Neurosurg Clin N Am. 2019 Jul;30(3):299-304. doi: 10.1016/j.nec.2019.02.003. PMID: 31078230.
- Beck AW, Simpson AK. High-Grade Lumbar Spondylolisthesis. Neurosurg Clin N Am. 2019 Jul;30(3):291-298. doi: 10.1016/j.nec.2019.02.002. PMID: 31078229.
- Patrick Rock et al. Spondylolisthesis grading system. Radiopaedia.org. https://radiopaedia.org/articles/spondylolisthesis-grading-system
- Bogduk et al. Imaging In: Management of Acute and Chronic Low Back Pain. Elsevier 2002.
- Försth P, Ólafsson G, Carlsson T, Frost A, Borgström F, Fritzell P, Öhagen P, Michaëlsson K, Sandén B. A Randomized, Controlled Trial of Fusion Surgery for Lumbar Spinal Stenosis. N Engl J Med. 2016 Apr 14;374(15):1413-23. doi: 10.1056/NEJMoa1513721. PMID: 27074066.
- Karsy M, Bisson EF. Surgical Versus Nonsurgical Treatment of Lumbar Spondylolisthesis. Neurosurg Clin N Am. 2019 Jul;30(3):333-340. doi: 10.1016/j.nec.2019.02.007. Epub 2019 Apr 19. PMID: 31078234.
- Ghogawala Z, Dziura J, Butler WE, Dai F, Terrin N, Magge SN, Coumans JV, Harrington JF, Amin-Hanjani S, Schwartz JS, Sonntag VK, Barker FG 2nd, Benzel EC. Laminectomy plus Fusion versus Laminectomy Alone for Lumbar Spondylolisthesis. N Engl J Med. 2016 Apr 14;374(15):1424-34. doi: 10.1056/NEJMoa1508788. PMID: 27074067.