title: Canine sacroiliac luxation: anatomic study of dorsoventral articular surface angulation and safe corridor for placement of screws used for lag fixation.
abstract: OBJECTIVE
  To define a safe corridor in the dorsoventral plane to facilitate placement of screws inserted in lag fashion within the sacral body for fixation of sacroiliac fracture-luxation injuries in dogs.
  
  
  METHODS
  Anatomic study.
  
  
  METHODS
  Cadaveric canine sacra.
  
  
  METHODS
  Canine sacra (n=45) were used for a radiographic study to define a safe corridor in the dorsoventral plane for placement of screws inserted in lag fashion for fixation of sacroiliac luxation in the dog. The defined safe corridor allowed drilling to a depth of 65% of the sacral width to ensure screw purchase of > or =60%. Effects of positioning and measurement techniques were evaluated.
  
  
  RESULTS
  Eighty-seven safe corridors were measured. The mean articular surface was 100+/-4.52 degrees from horizontal. Mean maximum, optimum, and minimum safe corridor drill angles were 111+/- 4.57 degrees, 100+/-4.70 degrees, and 89+/-5.17 degrees, respectively, from the articular surface. Predicted surgeon error of +/-4 degrees was used to define the safe corridor for use clinically.
  
  
  CONCLUSIONS
  In 91% of sacra, a drill angle of 100+/-4 degrees would remain ventral to the vertebral canal. Twelve sacra (14%) were at risk of penetration of the pelvic canal. A drill angle of 97+/-4 degrees avoids penetration of the vertebral canal in all sacra measured but risks ventral exit from the body in 30% of sacra studied.
  
  
  CONCLUSIONS
  A drill angle of 97 degrees from the articular surface is recommended for insertion of screws for lag fixation of canine sacroiliac luxation.
authors.affiliation: Queen's Veterinary School Hospital, Department of Veterinary Medicine, Madingley Road, Cambridge, UK. cjs24@cam.ac.uk
authors.forename: Chris J
authors.initials: CJ
authors.lastname: Shales
authors.forename: Sorrel J
authors.initials: SJ
authors.lastname: Langley-Hobbs
mesh_terms: D000818:Animals; D001863:Bone Screws / Q000662:veterinary*; D002102:Cadaver; D004285:Dogs / Q000033:anatomy & histology* / Q000293:injuries / Q000601:surgery*; D007593:Joint Instability / Q000601:surgery / Q000662:veterinary; D012446:Sacroiliac Joint / Q000033:anatomy & histology / Q000293:injuries / Q000601:surgery