Lumbosacral Spondylolysis

Updated: Jul 16, 2021
  • Author: Achilles Litao, MD; Chief Editor: Craig C Young, MD  more...
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Practice Essentials

Lumbosacral spondylolysis (lumbar spondylolysis) is a unilateral or bilateral defect of the pars interarticularis that affects one or more of the lumbar vertebrae. See the images below.

Radiograph of L4 defect in the pars interarticular Radiograph of L4 defect in the pars interarticularis.
Computed tomography scan demonstrating defects in Computed tomography scan demonstrating defects in the left and right pars interarticularis.

The term spondylolysis is derived from the Greek words spondylos, meaning vertebra, and lysis, meaning break or defect. Numerous hypotheses have been proposed on the etiology of lumbosacral spondylolysis (lumbar spondylolysis), as follows:

  • Separate ossification centers

  • Fracture during postnatal life

  • Stress fracture [1, 2]

  • Increased lumbar lordosis

  • Impingement of the articular process on the pars articularis

  • Weakness of supporting structures [3]

  • Growth [2, 4]

  • Pathologic changes in the pars articularis

  • Dysplasia of the pars interarticularis

However, mechanical factors are widely believed to be the cause or at least the trigger of the development of lumbosacral spondylolysis (lumbar spondylolysis), especially when congenital abnormalities are present. [5]  Moreover, lumbosacral spondylolysis (lumbar spondylolysis) is argued to be related to the human erect posture and lumbar curve. [1]

Ambulation may have a role in the genesis of lumbosacral spondylolysis (lumbar spondylolysis) because no known cases exist in nonambulatory patients. [6]  As an acquired condition, no reports exist of its occurrence in stillborn fetuses or in the newborn. [7]  Heredity is also implicated. [8]

When the defect in the pars interarticularis is not associated with a forward displacement, the term spondylolysis applies. [9]  The term spondylolisthesis is derived from spondylos and listhesis, meaning movement or slipping, and refers to the slipping forward of one vertebra on the next caudal vertebra (see the image below).

Lateral radiograph of the lumbar spine shows spond Lateral radiograph of the lumbar spine shows spondylolysis at L5 with spondylolisthesis at L5 through S1. On this single view, it is not possible to determine if these pars defects are unilateral or bilateral. Oblique views may help resolve this issue.

Lumbosacral spondylolysis (lumbar spondylolysis) is most common at L5, accounting for 85% of all cases, [10, 11]  and may be observed as high as L2. [12, 13]  Therefore, a slip is most common at the level of L5 slipping forward on S1. Lumbosacral spondylolysis (lumbar spondylolysis) is the cause of the most common type of spondylolisthesis. [4]  Moreover, Ariyoshi et al reported a case of lumbosacral spondylolysis (lumbar spondylolysis) that occurred at 3 sites in L5 that involved the bilateral pars interarticularis and the center of the right lamina. [14]


Functional Anatomy

Repetitive axial loading, especially in an extended lumbar spine is thought to be the most important contributing mechanism causing lumbosacral spondylolysis (lumbar spondylolysis), leading to fatigue fracture of the pars interarticularis. Shear stresses on the isthmic pars are greater when the lumbar spine is extended. When repetitive extension stresses occur, the pars interarticularis becomes impinged from the inferior facet of the cephalad vertebrae, which results in microfractures and attempts at repair. [15] See the images below.

Long TR (T2-weighted) fat suppressed sagittal magn Long TR (T2-weighted) fat suppressed sagittal magnetic resonance image shows increased signal in the pars interarticularis on the left at L5 (same patient in Images 3-4). This is an acute stress reaction.
Sagittal short TR (T1-weighted) magnetic resonance Sagittal short TR (T1-weighted) magnetic resonance image shows decreased signal in the pars interarticularis on the left at L5 (same patient in Images 3-4).

Sport-Specific Biomechanics

Lumbosacral spondylolysis (lumbar spondylolysis) occurs in 3-7% of the general population [16] The athletic population is believed to be more prone to the development of this condition, [15] because the incidence of lumbosacral spondylolysis (lumbar spondylolysis) in competitive athletes is higher than the percentage reported for the nonsports population. [17]

The overall percentage of lumbosacral spondylolysis (lumbar spondylolysis) among athletes in a study by Soler et al was about 8%, a figure not significantly higher than that among the general population. [16] However, certain sporting events were found to contribute higher percentages when each sport was considered separately, with the highest percentages of lumbosacral spondylolysis (lumbar spondylolysis) occurring in throwing sports (26.67%), artistic gymnastics (16.96%), and rowing (16.88%). [16] In an earlier series, a high percentage of lumbosacral spondylolysis (lumbar spondylolysis) was been observed in diving (43.13%), wrestling (29.82%), and weight lifting (22.68%). [17]

Other sports with high incidence rates of lumbosacral spondylolysis (lumbar spondylolysis) are ballet, dancing, football, volleyball, and fast bowlers in cricket. In ballet, the higher incidence rate is due in part to an inability to reach or maintain proper turn-out and thus overcompensation with lordosis.

In general, the presence of the repetitive actions of flexion, extension, rotation, and torsion, either alone or in combination, that are often associated with resistance are the biomechanical movements that show the highest prevalence of lumbosacral spondylolysis (lumbar spondylolysis). [16]



United States statistics

Lumbosacral spondylolysis (lumbar spondylolysis) is more commonly observed in males, [10] but this difference may not be significant. [18, 16]

In the United States, a reported difference exists between the sexes and races, with an incidence of lumbosacral spondylolysis (lumbar spondylolysis) of 6.4% in white men, 2.8% in black men, 2.3% in white women, and 1.1% in black women. A pars defect is twice as common in boys than in girls, although high-grade slippage is 4 times more common in girls than in boys. Alaskan Eskimos (26%) have the highest incidence, with the highest rate in Eskimos from north of the Yukon River. [4]

In general, athletes may have an increased chance of having symptomatic lumbosacral spondylolysis (lumbar spondylolysis). Whether the overall incidence is any different than the general population is unknown.



If treatment is instituted early, lumbosacral spondylolysis (lumbar spondylolysis) can be successfully treated with conservative management. [2]  The cure rate for early lumbosacral spondylolysis (lumbar spondylolysis) with activity restriction and a thoracolumbosacral orthosis is 73%, whereas more advanced spondylolyses were found to be less responsive to this regimen. [2]

Tatsumura et al studied factors associated with the failure of conservative therapy in adolescents and children with acute unilateral lumbar spondylolysis with bone marrow edema. They found that progressive pathological stage, contralateral pseudarthrosis, and L5 lesion level had a significant negative effect on the achievement of successful bony union. [19]

With history and physical examination findings compatible with lumbosacral spondylolysis (lumbar spondylolysis), athletes with normal findings on plain radiography and bone scanning are most likely to have pathology other than a pars defect. They are presumed to have a chronic back strain, and further investigation of the cause of the back pain is indicated while they are placed on physical therapy. Studies are repeated in 6-8 weeks if patients are still symptomatic with physical therapy. [12]  MRI is appropriate in this setting. [20]

Surgical treatment is an option for persistently symptomatic patients who did not achieve bony healing with activity restriction and bracing. [21, 22, 23, 24, 25, 26, 27]  Bony union has also been reported with transcutaneous electrical stimulation (TENS) in this group of patients. [28]

Return to play

Return to play of an athlete with lumbosacral spondylolysis (lumbar spondylolysis) is first begun with low-level sport activities after the follow-up visit at 4-6 weeks, after which gradual increase in intensity as tolerated is allowed under supervision. [29] Return to full activity is permitted only when patients are totally asymptomatic with full range of motion. [12] Patients must also have normal flexibility and normal strength and balance.


Complications of lumbosacral spondylolysis (lumbar spondylolysis) include a progression to spondylolisthesis (ie, slippage of the vertebrae and its sequelae) as well as delayed diagnosis and nonunion with chronic pain.


Patient Education

All athletes, especially those younger than 18 years, should know that not all sources of back pain are muscular and, therefore, should not be ignored if persistent. This is most important if the athlete is participating in gymnastics, football, dancing, or figure skating.

Because the etiology of lumbosacral spondylolysis (lumbar spondylolysis) is unknown and factors that cause slippage are unknown, prevention suggestions are unavailable. However, athletes must be advised that preventing recurrences may prove difficult if they return to high-level competition.

For excellent patient education resources, see eMedicineHealth's patient education article Low Back Pain.