title: Newly occurred L4 spondylolysis in the lumbar spine with pre-existence L5 spondylolysis among sports players: case reports and biomechanical analysis.
abstract: METHODS
  Case series and a biomechanical study using a finite element (FE) analysis.
  
  
  OBJECTIVE
  To report three cases with multi-level spondylolysis and to understand the mechanism biomechanically.
  
  
  BACKGROUND
  Multi-level spondylolysis is a very rare condition. There have been few reports in the literature on multi-level spondylolysis among sports players.
  
  
  METHODS
  We reviewed three cases of the condition, clinically. These patients were very active young sports players and had newly developed fresh L4 spondylolysis and pre-existing L5 terminal stage spondylolysis. Thus, we assumed that L5 spondylolysis may have increased the pars stress at the cranial adjacent levels, leading to newly developed spondylolysis at these levels. Biomechanically, we investigated pars stress at L4 with or without spondylolysis at L5 using the finite element technique.
  
  
  RESULTS
  L4 pars stress decreased in the presence of L5 spondylolysis, which does not support our first hypothesis.
  
  
  CONCLUSIONS
  It seems that multi-level spondylolysis may occur due to genetic and not biomechanical reasons.
authors.affiliation: Department of Orthopedics, The University of Tokushima School of Medicine, Tokushima 770-8503, Japan. sairyokun@hotmail.com
authors.forename: Koichi
authors.initials: K
authors.lastname: Sairyo
authors.forename: Toshinori
authors.initials: T
authors.lastname: Sakai
authors.forename: Natsuo
authors.initials: N
authors.lastname: Yasui
authors.forename: Ali
authors.initials: A
authors.lastname: Kiapour
authors.forename: Ashok
authors.initials: A
authors.lastname: Biyani
authors.forename: Nabil
authors.initials: N
authors.lastname: Ebraheim
authors.forename: Vijay K
authors.initials: VK
authors.lastname: Goel
mesh_terms: D000293:Adolescent; D001265:Athletic Injuries / Q000000981:diagnostic imaging / Q000473:pathology; D001696:Biomechanical Phenomena; D002648:Child; D020342:Finite Element Analysis; D006801:Humans; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000473:pathology*; D008297:Male; D013169:Spondylolysis / Q000000981:diagnostic imaging / Q000235:genetics / Q000473:pathology* / Q000628:therapy; D014057:Tomography, X-Ray Computed