title: Biomechanical analysis of atlas fractures: a study on 40 human atlas specimens.
abstract: METHODS
  Forty isolated specimens of the first cervical vertebra were tested by the application of pure axial force to failure. To exclude ligamentous side effects, transverse ligaments were dissected in all specimens.
  
  
  OBJECTIVE
  To investigate the biomechanical characteristics of the human atlas and to describe the influence of different speeds of force impact on the fracture types.
  
  
  BACKGROUND
  Atlas fractures have been reproduced in some studies in the literature. However, the characteristics of isolated atlas fractures under pure axial loading at different speeds has not been reported so far.
  
  
  METHODS
  After dissection of soft tissue and generation of a peripheral quantitative computed tomography scan, the atlas preparations were tested to failure by displacement-controlled axial force application at constant speeds of either 0.5 mm/s (Group 1) or 300 mm/s (Group 2). The fracture types were classified according to Gehweiler.
  
  
  RESULTS
  At slow loading speed (Group 1), 2 Type-I (anterior arch), 3 Type-II (posterior arch), 2 Type-III (anterior and posterior arch), and 13 Type-IV (lateral mass) fractures occurred out of 20 specimens. At high loading speed (Group 2), Type-III fractures (burst fractures of 2 to 4 parts) occurred in all 20 tested specimens.
  
  
  CONCLUSIONS
  The presented results strongly suggest that the Type of atlas fracture depends on the speed of axial force impact. The present study demonstrates that Type-III fractures (2- to 4-part burst fractures) result from fast force impact whereas slow force impact is responsible for Type-IV atlas fractures of the lateral mass.
authors: Center for Biomechanics and Skeletal Biology UKE, Germany.
authors: Matthias
authors: M
authors: Gebauer
authors: Nils
authors: N
authors: Goetzen
authors: Florian
authors: F
authors: Barvencik
authors: Frank Timo
authors: FT
authors: Beil
authors: Martin
authors: M
authors: Rupprecht
authors: Johannes M
authors: JM
authors: Rueger
authors: Klaus
authors: K
authors: Püschel
authors: Michael
authors: M
authors: Morlock
authors: Michael
authors: M
authors: Amling
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D002102:Cadaver; D001270:Cervical Atlas / Q000000981:diagnostic imaging / Q000503:physiopathology*; D005260:Female; D050723:Fractures, Bone / Q000000981:diagnostic imaging / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012044:Regression Analysis; D014057:Tomography, X-Ray Computed