title: Analysis of lumbar pedicle morphology in degenerative spines using multiplanar reconstruction computed tomography: what can be the reliable index for optimal pedicle screw diameter?
abstract: OBJECTIVE
  The measurement of transverse pedicle width is still recommended for selecting a screw diameter despite being weakly correlated with the minimum pedicle diameter, except in the upper lumbar spine. The purpose of this study was to reveal the difference between the minimum pedicle diameter and conventional transverse or sagittal pedicle width in degenerative lumbar spines.
  
  
  METHODS
  A total of 50 patients with degenerative lumbar disorders without spondylolysis or lumbar scoliosis of >10° who preoperatively underwent helical CT scans were included. The DICOM data of the scans were reconstructed by imaging software, and the transverse pedicle width (TPW), sagittal pedicle width (SPW), minimum pedicle diameter (MPD), and the cephalocaudal inclination of the pedicles were measured.
  
  
  RESULTS
  The mean TPW/SPW/MPD values were 5.46/11.89/5.09 mm at L1, 5.76/10.44/5.39 mm at L2, 7.25/10.23/6.52 mm at L3, 9.01/9.36/6.83 mm at L4, and 12.86/8.95/7.36 mm at L5. There were significant differences between the TPW and MPD at L3, L4, and L5 (p < 0.01) and between the SPW and MPD at all levels (p < 0.01).
  
  
  CONCLUSIONS
  The MPD was significantly smaller than the TPW and SPW at L3, L4, and L5. The actual measurements of the TPW were not appropriate for use as a direct index for the optimal pedicle screw diameter at these levels. Surgeons should be careful in determining pedicle screw diameter based on plain CT scans especially in the lower lumbar spine.
authors.affiliation: Department of Orthopaedic Surgery, National Hospital Organization Osaka Minami Medical Center, Kawachinagano, Osaka, Japan. t-makino@za2.so-net.ne.jp
authors.forename: Takahiro
authors.initials: T
authors.lastname: Makino
authors.forename: Takashi
authors.initials: T
authors.lastname: Kaito
authors.forename: Hiroyasu
authors.initials: H
authors.lastname: Fujiwara
authors.forename: Kazuo
authors.initials: K
authors.lastname: Yonenobu
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001863:Bone Screws; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae / Q000033:anatomy & histology / Q000000981:diagnostic imaging* / Q000601:surgery; D008161:Lumbosacral Region / Q000033:anatomy & histology / Q000000981:diagnostic imaging* / Q000601:surgery; D008297:Male; D008875:Middle Aged; D013130:Spinal Stenosis / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery; D013168:Spondylolisthesis / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery; D014057:Tomography, X-Ray Computed