title: The influence of anatomy (normal versus scoliosis) on the free-hand placement of pedicle screws: Is misplacement more frequent in patients with anatomical deformity?
abstract: METHODS
  Retrospective prognostic study.
  
  
  OBJECTIVE
  To evaluate whether patients with anatomical deformity due to scoliosis have a higher frequency of inaccurate pedicle screw insertion and related complications using the free-hand technique compared with those whose normal anatomy had been impacted by trauma.
  
  
  METHODS
  Consecutively treated trauma patients with otherwise normal anatomy (48 patients instrumented with 291 screws, group A) and scoliosis patients (24 patients instrumented with 287 screws, group B) were evaluated. Screw position on CT was evaluated using the classification by Gertzbein and Robbins with modification by Karagoz Guzey. (See web appendix at www.aospine.org/ebsj for complete classification description.) Images were examined by two fellows and one junior staff member none of whom participated in patient management. Screw position was determined by consensus.
  
  
  RESULTS
  In group A, five (1.7%) out of 289 screws were severely misplaced and 26 (9%) screws caused either medial (3.8%) or lateral (5.2%) cortical breeches. The other 258 (89.3%) screws were fully contained within the cortical boundaries of the pedicle. In group B, seven (2.8%) out of 256 screws were severely misplaced. Thirty-three (13%) screws caused cortical breeches, either medial (9%), lateral (2%), or anterior (2%), and 216 (84.3%) screws were fully contained within the cortical boundaries of the pedicle and the vertebra. Neurological complications were reported in one patient with scoliosis. No vascular complications were reported in either group.
  
  
  CONCLUSIONS
  The percentage of incorrectly placed screws was similar in both groups, trauma and deformity patients. The presence of vertebral anatomical changes related to adult scoliosis was not associated with an increase in the screw-related neurological or vascular complications. [Table: see text] The definiton of the different classes of evidence is available on page 73.
authors: Italian Hospital of Buenos Aires, Buenos Aires, Argentina.
authors: Marcelo
authors: M
authors: Gruenberg
authors: Matías
authors: M
authors: Petracchi
authors: Marcelo
authors: M
authors: Valacco
authors: Carlos
authors: C
authors: Solá
references: J Bone Joint Surg Am. 1999 Nov;81(11):1519-28
references: 10565643
references: J Spinal Disord Tech. 2006 Aug;19(6):436-41
references: 16891980
references: Neurosurgery. 2001 Apr;48(4):771-8; discussion 778-9
references: 11322437
references: Spine (Phila Pa 1976). 2000 Sep 15;25(18):2285-93
references: 10984779
references: Clin Orthop Relat Res. 1986 Feb;(203):54-7
references: 3955997
references: J Bone Joint Surg Am. 2000 Oct;82(10):1458-76
references: 11057475
references: Spine (Phila Pa 1976). 2007 Jan 15;32(2):E56-64
references: 17224800
references: Spine (Phila Pa 1976). 2001 Nov 1;26(21):2340-6
references: 11679819
references: Spine (Phila Pa 1976). 2007 Feb 1;32(3):E111-20
references: 17268254
references: Spine (Phila Pa 1976). 1990 Jan;15(1):11-4
references: 2326693