title: Pedicular anatomy of the first sacral segment in transitional variations of the lumbo-sacral junction.
abstract: METHODS
  The study aims to investigate the dimensions and angular orientations of the pedicles of the first sacral segment at the L5-S1 junctions affected by transitional variations.
  
  
  OBJECTIVE
  Measurement of parameters of the S1 pedicle and its orientation in sacra with (1) Accessory L5-S1 articulations, (2) Sacralisation of the L5, and (3) Lumbarisation of the first sacral segment, and comparing data with that observed in normal sacra.
  
  
  BACKGROUND
  Lumbosacral fusion with instrumentation and screw fixation is commonly practiced to treat unstable L5-S1 junctions caused by a host of reasons. Though morphometric data pertaining to normal S1 pedicle structure is available in literature, it is hard to find such information regarding pedicles of first sacral segments associated with transitional variations. Transitional states at the lumbosacral junctions are often linked to development of L5-S1 instability. It thus becomes imperative to investigate S1 pedicular anatomy in context of these variations to prevent inadvertent surgical injuries and optimizing effects of screw placement in such sacral variations.
  
  
  METHODS
  S1 pedicle dimensions were measured in normal and L5-S1 transition affected sacra. Slope of the pedicle was measured with respect to the sagittal and the horizontal planes.
  
  
  RESULTS
  Linear parameters were similar in the normal sacra and those with L5-S1 accessory articulations. Sacralisation reduced all dimensions including pedicle height, sagittal and transverse dimensions. Lumbarisation was associated with small length between the facet and the sacral promontory. Sacralisation reduced the sagittal angulation of the pedicles but substantially increased its downward slope. Lumbarised pedicles were more obtuse with the sagittal plane and less steep in front.
  
  
  CONCLUSIONS
  S1 pedicle morphology and angulation in the first sacral segment are different from the normal in L5-S1 transitional situations and hence should be mapped accordingly in screw placements at the region in context of such common variations.
authors.affiliation: Department of Anatomy, SRM Medical College, Kattankulathur, Kanchipuram District, Tamil Nadu, India. mahatonk@yahoo.co.in
authors.forename: Niladri Kumar
authors.initials: NK
authors.lastname: Mahato
mesh_terms: D001863:Bone Screws; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae / Q000002:abnormalities / Q000473:pathology* / Q000601:surgery; D008297:Male; D008953:Models, Anatomic; D012447:Sacrum / Q000002:abnormalities / Q000473:pathology* / Q000601:surgery; D013122:Spinal Diseases / Q000473:pathology* / Q000601:surgery; D013123:Spinal Fusion / Q000295:instrumentation / Q000379:methods