What is incidence of pars interarticularis injury in the US?

Updated: Jan 22, 2019
  • Author: Gerard A Malanga, MD; Chief Editor: Craig C Young, MD  more...
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The incidence of isthmic spondylolysis varies according to different surveys, but it has been estimated to be approximately 3-6% in the general adult population. The incidence has been found to vary amongst different ethnic groups, possibly identifying genetic factors as having a degree of influence. Roche and Lowe examined 4200 cadaveric spines and found an overall incidence of 4.2%, with an incidence of 6.4% for white males, 2.3% for white females, 2.8% for black males, and 1.1% for black females. [7] Lifestyle differences among cultural groups undoubtedly account for at least part of the difference in incidence among ethnic groups, and these findings must be treated with a degree of caution. [8]

Most studies reveal that males are consistently affected 2-3 times as often as females, and whites are affected almost 3 times as often as blacks. Most studies also show no significant change in incidence in individuals aged 20-80 years. Based on these studies, spondylolytic lesions are generally believed to occur in the early school-age years.

A prospective study demonstrated a 4.4% incidence of spondylolysis in 500 first-grade children, which increased to an incidence of 6% in adulthood, with a follow-up interval of 45 years. [9] The prevalence of spondylolytic lesions among adolescent athletes appears to be much higher than the prevalence among the general population. According to large-scale radiographic studies, the prevalence among adolescent athletes ranges from 8-15%; among adolescent athletes referred for evaluation of back pain, this figure has been reported to be as high as 47%. [10]

A large screening study in Japan obtained from children who presented with LBP and who were participating in sports found that 32% of the patients younger than 19 years had at least one or more pars interarticularis defects. [11] Morita et al investigated 185 adolescents younger than 19 years with spondylolysis and found 180 to be currently active in sports. [11]

Within competitive sports, increasing age and training more than 15 hours per week correlates with a higher incidence of spondylolytic defects. [12] The most common level of a spondylolytic lesion is at the L5 level, estimated at 85-95%, followed by the L4 level, estimated at 5-15%.

Further evidence supporting the role of genetics as a significant factor was found by Fredrickson et al, who discovered an increased incidence of spondylolysis in fathers, mothers, and male siblings of affected people in their study. [13] In an earlier study, as many as 26% of the immediate relatives of those with a demonstrable spondylolysis were found to have a similar problem. [14]

A strong association exists between lumbar spondylolysis and the presence of spina bifida occulta, which has been found to occur in 5-10% of the general population. [7, 13, 15] One theory is that spina bifida occulta may lead to instability of the lower lumbar segment, predisposing an individual to the development of pars interarticularis defects. [16] Hyperlordosis of the lumbosacral spine, such as seen in Scheuermann kyphosis, has been associated with a higher incidence of spondylolysis. [17]

Spondylolysis is associated with spondylolisthesis in approximately 25% of cases; however, the progression of the spondylolisthesis to any significant degree is generally uncommon in those who participate in athletics and in those who do not participate in athletics. The tendency of progression of spondylolisthesis is correlated with the pubescent growth spurt; in a study involving a 20-year follow-up of 255 patients, the mean slip progression was 4 mm. [18] Only 11% of adolescents and 5% of adults had slip progressions of greater than 10 mm in this radiologic review.

A European retrospective analysis by Lemoine et al that included 717 pediatric abdominal and pelvic CT scans from 532 children who had a CT scan for a variety on non-lumber conditions reported that the prevalence of spondylolysis was 1% in children under age 3, 3.7% in children under age 6 and 4.7% total (editors note - the prevalence may have been affected by the inclusion of multiple CT studies on the same patient since it was unclear how the researchers handled these cases - other than noting that 3 of these patients had findings of spondylosis on all their studies). The study also found that unilateral spondylolysis was associated with a spinal malformation with normal pelvic incidence. [19]

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