When viewing the spinal column from the front or back, ideally it appears straight. When viewing the spinal column from the side, it has 3 curves: the cervical lordosis, the thoracic kyphosis, and the lumbar lordosis.

The curves of the spinal column dictate that some of the vertebral bodies will sit on an inclined plane in the lateral dimension. The steepest inclined plane is between L5 (the last lumbar vertebra) and the sacral base.

When a vertebrae slides down (forward) the inclined plane of the vertebrae below (or sacrum), it is called a spondylolisthesis (1):

“Spondylolisthesis is defined as an anterior displacement of a vertebral body in relation to the segment immediately below.”

Spondylolisthesis has a number of classifications. The three most common types are (1, 2):

• Dysplastic Spondylolisthesis: This is a congenital spondylolisthesis because it results from a defect that is present at birth. The facet joints between L5 and the sacrum are underdeveloped, allowing the L5 vertebrae to slide forward.
• Degenerative Spondylolisthesis: Age-related degeneration of the facet joints and the intervertebral disc can allow for an instability between L5 and the sacrum, allowing the L5 vertebrae to slide forward, down the inclined plane of the sacral base.
• Isthmic Spondylolisthesis: Isthmic spondylolisthesis is the focus of this presentation.

The structure most responsible for preventing the slippage of L5 down the sacral base inclined plane is the bony isthmus between the superior and inferior facets of the L5 posterior elements. This bony element is called the pars interarticularis (literally, the part of bone between the articulating facets). The pars interarticularis is the weak link. A fracture of the pars interarticularis will allow the L5 vertebrae to slide down the inclined sacral base.

The fracture of the pars interarticularis is called spondylolysis.

Together, the fracture of the pars interarticularis and the forward slippage of L5 is termed:

Spondylolysis with Anterior Spondylolisthesis

Ninety percent of spondylolysis with anterior spondylolisthesis occur at the L5-sacrum level (1).

The Grading System

The grading system for anterior spondylolisthesis is credited to Meyerding (2). It is based upon the percentage of forward slippage, as follows:

The sacral base is divided into 4 equal quadrants and the magnitude of slip is based on the percentage of endplate that is uncovered as a result of the slip.

Grade I represents a 25% slippage
Grade II represents a 50% slippage
Grade III represents a 75% slippage
Grade IV represents a 100% slippage

Grades I and II are the most common and referred to as “low grade” spondylolisthesis. Grades III and IV spondylolisthesis are commonly referred to as “high grade.”

Congenital vs. Acquired

The fact that there is a fracture of the pars in those with isthmic anterior spondylolisthesis is not controversial. The fracture site is readily visible on x-rays and other imaging. Bone scans can date the fracture as to being acute or of long standing.

Many healthcare providers believe that those with isthmic anterior spondylolisthesis and pars fracture are congenital, meaning the person is born with that finding. However, much evidence challenges that as it has not been documented in newborn babies:

In 1965, Melamed publishes an article titled (4):

Spondylolysis and Spondylolisthesis are Not Congenital

In 1971, Schmorl and Junghanns note (5):

There is increasing support for the opinion that spondylolysis is “acquired after birth during growth of the skeletal system.”

“[Spondylolysis] seems to be closely connected to the upright gait and to the lumbar lordosis.”

In 1973, Farfan notes (6):

“[Evidence] suggests that the defect in the neural arch is acquired,” and that the “condition is a stress fracture.”

In 1975, Cyriax notes (7):

“Evidence has lately been accumulating that a disorder named spondylolisthesis (which had been regarded as due to an inborn defect in the vertebral arch) is seldom congenital but is acquired in childhood.” 

“Stress fractures form between the two halves of the vertebral arch.”

In 1977, Macnab notes (8):

“In spondylolytic spondylolisthesis, the basic lesion is a defect in the neural arch across the pars interarticularis.” “The neural arch defects occur most frequently between ages of 5 and 7. Forward slippage of the vertebral body occurs most frequently between ages of 10 and 15 and rarely increases after 20.”

“In some Eskimo communities the incidence of neural arch defects may rise as high as 50%.” “The incidence of spondylolysis in the white population of the North American continent is about 6%.”

In 1977, D’Ambrosia notes (9):

“[Spondylolysis with spondylolisthesis] only occurs in man who walks with a true upright stance and has lumbar lordosis. There is no evidence that this defect is ever present at birth, and it is not seen in patients who have never been ambulatory. The most common age of onset is between 5 and 6 years of age, but slipping can occur up to age 20. The period of most rapid slipping is between 10 and 15 years when the adolescent growth spurt is at its peak.”

In 1980, Keim notes (10):

“Many authorities consider spondylolysis and spondylolisthesis to be stress fractures of the pars interarticularis, or isthmus, of a vertebrae.”

“After the age of 5 and usually in the teenage years, repeated shearing stresses, such as those that occur in gymnastics or contact sports, can cause a stress fracture in the isthmus.”

In 1980, Finneson notes (11):

Spondylotic spondylolisthesis is due to a separation or dissolution of the pars. “It is always a fatigue fracture.” It is almost never seen below the age of 5, but is found in 4.4% of 7-year-olds.

In 1980, Wertzberger and Peterson note (12):

“There is increasing evidence that the defect in the pars interarticularis is due to fatigue fracture rather than being of congenital origin. We describe the youngest patient on record with spondylolysis and spondylolisthesis in whom roentgenograms that showed no abnormality had previously been taken. This case supports the hypothesis that spondylolysis and spondylolisthesis are acquired and not congenital, even when discovered in a very young child.”

In 1981, Rosenberg and colleagues obtained radiographs of the lumbosacral spines of 143 patients (age range of 11 to 93 years) that had never walked. They note  (13):

“No case of spondylolysis or spondylolisthesis was detected, and when compared to the 5.8% incidence in the general population.”

“These results support the theory that spondylolysis and isthmic spondylolisthesis represent a fatigue fracture resulting from activities associated with ambulation.”

In 1983, Salter notes (14):

“[Approximately 85% of spondylolysis] occur in the fifth lumbar vertebrae and most of the remaining 15% occur in the fourth lumbar vertebrae.”

“Once thought to be a congenital defect spondylolysis is now known to develop during postnatal life.” 

“Since the lower lumbar region of the human spine is subjected to much stress in the erect position, it is possible that spondylolysis represents either a stress fracture (fatigue fracture) from oft-repeated stresses or an ordinary fracture from a single injury.”

The gap in the pars after fracture and separation is filled in with fibrous tissue. 

“The forward slippage of one vertebral body (and the remainder of the spinal column above it) in relation to the vertebral segment immediately below is referred to as a spondylolisthesis. It occurs most commonly in the lower lumbar spine particularly between the fifth lumbar vertebrae and the sacrum.”

A normal lumbar vertebral body is prevented from slipping forward by an intact neural arch. With loss of continuity of the pars interarticularis, “the intervertebral disc is not sufficiently strong to prevent displacement of the vertebrae.”

The forward displacement of spondylolisthesis is “most likely to be progressive during the rapid growth spurt of early adolescence.”

“[Spondylolytic spondylolisthesis] usually becomes manifest during childhood with the gradual onset of low back pain which is aggravated by standing, walking and running and relieved by lying down.”

“The associated clinical deformity, which is related to the degree of forward slip, is characterized by a ‘step’ in the lumbosacral region at the level of the spondylolisthesis and an increased lumbar lordosis above.”

In 1987, Yochum and Rowe note (1):

The Eskimo infant is placed upright at an earlier age. This might account for the higher incidence of spondylolysis and spondylolisthesis in Eskimo populations.        

In 1990, White and Panjabi note (15):

“In spondylolisthesis there is a defect in the pars interarticularis that is associated with anterior translation of the involved vertebrae in relation to the subjacent one.” “The theory that seems to have survived best at present is that of fatigue fracture.”

“The disease is thought to have an incidence of 1.95% in American blacks, 5.8% in American whites, and about 60% in American Eskimos.”

In 2011, Cox notes (16):

“Isthmic spondylolisthesis is the most common type of spondylolisthesis, and it is caused by a defect in the ossification of the pars interarticularis.”

“It is no longer questioned that spondylolysis is a fracture that may or may not heal. These fractures are postulated to occur because of the assumption of the upright posture by the infant, allowing a fatigue type of fracture to occur when stress beyond the strength of bone occurs.”

“One reason that forward slippage occurs most often in children aged 5 to 7 years may be because of the increased activity or to increased sitting in the lordotic posture done by children. It is known that fracture never occurs in animals other than humans, and only humans have lordosis.”

“At the time of slippage, the disc must break down, allowing annular stretching and tearing.” “The disc, being a very pain-sensitive structure, certainly creates symptomatology as the slippage occurs.”

“In adults, after the slippage occurs and the annular fibers heal, the pain lessens or disappears.”

•••••

Although the pars fracture may occur as a consequence of a single, painful traumatic event, it is usually a stress fracture that occurs in youth, and often in those who are most involved in sports activities (3). Children normally develop this type of fracture between the ages of 5 and 7, yet symptoms are not usually noticed until adulthood. The common incidence in the population is about 6%.

About 93% of cases of spondylolysis are associated with sports practice as follows (3):

• 50% in cricket, rugby, and American football players
• 44% in hockey players
• 40% in tennis players
• 40% in diving athletes
• 21% in volleyball players

Classically, the pain associated with anterior isthmic spondylolisthesis is not related to the degree of slippage, but rather to the degree of stability. Stability is historically evaluated with flexion/extension radiography, or by a hanging method (17). Instabilities greater than 3 mm may require bracing or a surgical stabilization, similar to the initial x-ray in this presentation.

Management

The pain of spondylolysis and spondylolisthesis is nearly always managed conservatively, which includes spinal manipulation and flexion distraction techniques (16). Reference examples include:

In 1978, Cassidy notes (18):

“Spinal manipulation offers rapid symptomatic relief to many patients with back pain associated with spondylolisthesis.”

In 1987, Yochum and Rowe note (1):

“A more conservative approach including chiropractic spinal manipulative therapy has been found beneficial in managing patients’ low back pain with the presence of spondylolysis or spondylolisthesis.”

In 1988, Kirkaldy-Willis et al. note (19):

“Frequently, spondylolisthesis is complicated by a posterior joint syndrome one level above the lesion or by a sacroiliac syndrome. Thus, improvement in the patient’s symptoms results from the effect of manipulation on these other joints. In our experience, manipulation is a good first line of treatment in patients with spondylolisthesis. We have seen patients who did not benefit from [surgical] decompression and/or fusion but who were relieved of their back and leg pain by manipulation directed to the sacroiliac joint.”

In 2017, Fedorchuk et al. report the correction of a grade II anterior isthmic spondylolisthesis using a chiropractic biomechanical protocol (20):

“This case provides the first documented evidence of a non-surgical or chiropractic treatment, specifically Chiropractic BioPhysics®, protocols of lumbar spondylolisthesis where spinal alignment was corrected.”

In 2024, Fedorchuk et al. report improvement in pain and quality of life in a series of three patients with anterior isthmic spondylolisthesis using a chiropractic biomechanical protocol (21):

“This series documents the first-recorded long-term corrections of lumbar spondylolisthesis and concomitant improvements in back pain, urinary urgency, and QOL using CBP^®.”

Ending Story

Rocky Bleier is now 78 years old (January 3, 2025). Growing up he was very athletic, excelling in football, basketball, and track. He played football at the University of Notre Dame where he was team captain. His Notre Dame team won a national championship in 1967. After graduation he was drafted by the Pittsburgh Steelers football team. His football dreams were put on hold because in 1968 he was drafted into the US Army. It was the height of the Vietnam War.

On August 20, 1969, Rocky Bleier was shot in the left thigh and an exploding grenade sent shrapnel into his lower right leg and foot. His injuries were severe. Years of rehabilitation included multiple surgeries that removed hundreds of pieces of shrapnel and scar tissue. The Army graded him with a 40% disability. When he returned to play NFL football with the Steelers, he wore shoes of different sizes because the surgeries had shortened his right foot. In the 10 years he played with the Steelers, he earned four Super Bowl rings.

Chiropractic lore claims that Rocky Bleier did all of this with a grade IV anterior spondylolisthesis of L5 on the sacral base and that he took advantage of regular chiropractic care (22).

REFERENCES

1. Yochum TR, Rowe LJ; “The Natural History of Spondylolysis and Spondylolisthesis,” in Essentials of Skeletal Radiology, Chapter 5; Williams & Wilkins; 1987.
2. Gallagher B, Moatz B, Tortolani PJ; Classifications in Spondylolisthesis; Seminars in Spine Surgery; September 2020; Vol. 32; No. 3; Article
3. de Lima MV, Caffaro MFS, Santili C, Watkins RG; Spondylolysis and Spondylolisthesis in Athletes; Revista Brasileira de Ortopedia (Sao Paulo); March 21, 2024; Vol. 59; No. 1; pp. e10–e16.
4. Melamed A; Spondylolysis and Spondylolisthesis are Not Congenital; Wisconsin Medical Journal; March 1965; Vol. 64:130-133.
5. Schmorl G, Junghanns H; Schmorl’s and Junghanns, The Human Spine in Health and Disease; Grune & Stratton; 1971.
6. Farfan HF; Mechanical Disorders of the Low Back; Lea & Febiger; 1973.
7. Cyriax J; The Slipped Disc, Causes, Prevention, and Treatment of a Universal Complaint; Second Edition; Grower Press, 1975.
8. MacNab I; Backache; Williams & Wilkins; 1977.
9. D’Ambrosia RD; Musculoskeletal Disorders, Regional Examination and Differential Diagnosis; Lippincott; 1977.
10. Keim H; Low Back Pain, Clinical Symposium; Vol. 32; No. 6; CIBA; 1980.
11. Finneson B; Low Back Pain; Second Edition; Lipponcott; 1980.
12. Wertzberger KL, Peterson HA; Acquired spondylolysis and spondylolisthesis in the young child; Spine; Sep-Oct 1980; Vol. 5; No. 5; pp. 437-442.
13. Rosenberg NJ, Bargar WL, Friedman B; The incidence of spondylolysis and spondylolisthesis in non-ambulatory patients; Spine; Jan-Feb 1981; Vol. 6; No. 1; pp. 35-38.
14. Salter RB; Textbook of Disorders and Injuries of the Musculoskeletal System; Second Edition; Williams and Wilkins; 1983.
15. White AA, Panjabi MM; Clinical Biomechanics of the Spine; Second Edition; Lippincott; 1990.
16. Cox JM; Low Back Pain, Mechanism, Diagnosis, and Treatment; Seventh Edition; Wolters Kluwer/Lippincott Williams & Wilkins; 2011.
17. Friberg O; Lumbar Instability: A Dynamic Approach by Traction-Compression Radiography; Spine; March 1987; Vol. 12; No. 2; pp. 119-129.
18. JD Cassidy JD, Potte GE, Kirkaldy-Willis WH; Manipulative Management of Back Pain in Patients with Spondylolisthesis; The Journal of the Canadian Chiropractic Association; March 1978.
19. Kirkaldy-Willis WH; Managing Low Back Pain; Second Edition; Churchill Livingstone; 1988.
20. Fedorchuk C, Lightstone DF, McRae C, Kaczor D; Correction of Grade 2 Spondylolisthesis Following a Non-Surgical Structural Spinal Rehabilitation Protocol Using Lumbar Traction: A Case Study and Selective Review of Literature; Journal of Radiology Case Reports; May 31, 2017; Vol. 11; No. 5; pp. 13-26.
21. Fedorchuk C, Fedorchuk CG, Lightstone DF;Improvement in Pain, Quality of Life, and Urinary Dysfunction following Correction of Lumbar Lordosis and Reduction in Lumbar Spondylolistheses Using Chiropractic BioPhysics^® Structural Spinal Rehabilitation: A Case Series with >1-Year Long-Term Follow-Up Exams; Journal of Clinical Medicine; March 2024; Vol. 13; No. 7.
22. Yochum TR; class presentation; 1985. [Terry Yochum, DC, is the most celebrated chiropractic radiologist in history. His textbook (1), Essentials of Skeletal Radiology, is core curriculum in all chiropractic colleges and in a number of medical schools].