title: Incidence of lumbar spondylolysis in the general population in Japan based on multidetector computed tomography scans from two thousand subjects.
abstract: METHODS
  Epidemiological analysis using CTs.
  
  
  OBJECTIVE
  To investigate the true incidence of lumbar spondylolysis in the general population in Japan.
  
  
  BACKGROUND
  Although there have been several reports on the incidence of lumbar spondylolysis, they had some weakness. One of them concerns the subjects investigated, because the incidence of lumbar spondylolysis varies considerably, and some patients are asymptomatic. In addition, most of the past studies used plain radiograph films or skeletal investigation. Therefore, the past reported incidence may not correspond to that of the general population.
  
  
  METHODS
  We reviewed the computed tomography (CT) scans of 2000 subjects (age: 20-92 years) who had undergone abdominal and pelvic CT on a single multidetector CT scanner for reasons unrelated to low back pain. We reviewed them for spondylolysis, spondylolytic spondylolisthesis, and spina bifida occulta (SBO) in the lumbosacral region. The grade (I-IV) of spondylolisthesis was measured using midsagittal reconstructions.
  
  
  RESULTS
  Lumbar spondylolysis was found in 117 subjects (5.9%). Their male-female ratio was 2:1. Multiple-level spondylolysis was found in 5 subjects (0.3%). Among these 117 subjects, there were 124 vertebrae with spondylolysis. Of them, 112 (90.3%) corresponded to L5, and 26 (21.0%) had unilateral spondylolysis.SBO was found in 154 subjects. Of them, 25 had spondylolysis (16.2%), whereas, in 1846 subjects without SBO, 92 had spondylolysis (5.0%). The incidence of spondylolysis among the patients with SBO was significantly higher than that in subjects without SBO (Odd ratio was 3.7-fold).Of 124 vertebrae with spondylolysis, 75 (60.5%) showed low-grade (Meyerding grade I or II) spondylolisthesis, and no subject presented high-grade spondylolisthesis. Spondylolisthesis was found in 74.5% of the subjects with bilateral spondylolysis, and in 7.7% of those with unilateral spondylolysis.
  
  
  CONCLUSIONS
  The incidence of lumbar spondylolysis in the Japanese general population was 5.9% (males: 7.9%, females: 3.9%).
authors.affiliation: Departments of Orthopedics, Institute of Health Biosciences, The University of Tokushima Graduate School, Tokushima, Japan.
authors.forename: Toshinori
authors.initials: T
authors.lastname: Sakai
authors.forename: Koichi
authors.initials: K
authors.lastname: Sairyo
authors.forename: Shoichiro
authors.initials: S
authors.lastname: Takao
authors.forename: Hiromu
authors.initials: H
authors.lastname: Nishitani
authors.forename: Natsuo
authors.initials: N
authors.lastname: Yasui
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D015994:Incidence; D007564:Japan / Q000453:epidemiology; D008159:Lumbar Vertebrae; D008297:Male; D008875:Middle Aged; D016136:Spina Bifida Occulta / Q000150:complications; D013168:Spondylolisthesis / Q000150:complications / Q000453:epidemiology; D013169:Spondylolysis / Q000150:complications / Q000000981:diagnostic imaging* / Q000453:epidemiology*; D014057:Tomography, X-Ray Computed / Q000379:methods*; D055815:Young Adult