title: In vivo analysis of insertional torque during pedicle screwing using cortical bone trajectory technique.
abstract: METHODS
  The insertional torque of pedicle screws using the cortical bone trajectory (CBT) was measured in vivo.
  
  
  OBJECTIVE
  To investigate the effectiveness of the CBT technique by measurement of the insertional torque.
  
  
  BACKGROUND
  The CBT follows a mediolateral and caudocephalad directed path, engaging with cortical bone maximally from the pedicle to the vertebral body. Some biomechanical studies have demonstrated favorable characteristics of the CBT technique in cadaveric lumbar spine. However, no in vivo study has been reported on the mechanical behavior of this new trajectory.
  
  
  METHODS
  The insertional torque of pedicle screws using CBT and traditional techniques were measured intraoperatively in 48 consecutive patients. A total of 162 screws using the CBT technique and 36 screws using the traditional technique were compared. In 8 of 48 patients, the side-by-side comparison of 2 different insertional techniques for each vertebra were performed, which formed the H group. In addition, the insertional torque was correlated with bone mineral density.
  
  
  RESULTS
  The mean maximum insertional torque of CBT screws and traditional screws were 2.49 ± 0.99 Nm and 1.24 ± 0.54 Nm, respectively. The CBT screws showed 2.01 times higher torque and the difference was significant between the 2 techniques (P < 0.01). In the H group, the insertional torque were 2.71 ± 1.36 Nm in the CBT screws and 1.58 ± 0.44 Nm in the traditional screws. The CBT screws demonstrated 1.71 times higher torque and statistical significance was achieved (P < 0.01). Positive linear correlations between maximum insertional torque and bone mineral density were found in both technique, the correlation coefficient of traditional screws (r = 0.63, P < 0.01) was higher than that of the CBT screws (r = 0.59, P < 0.01).
  
  
  CONCLUSIONS
  The insertional torque using the CBT technique is about 1.7 times higher than the traditional technique.
  
  
  METHODS
  2.
authors.affiliation: *Department of Orthopaedic Surgery, National Defense Medical College, Tokorozawa, Saitama, Japan; and †Department of Orthopaedic Surgery, National Hospital Organization, Murayama Medical Center, Tokyo, Japan.
authors.forename: Keitaro
authors.initials: K
authors.lastname: Matsukawa
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Yato
authors.forename: Takashi
authors.initials: T
authors.lastname: Kato
authors.forename: Hideaki
authors.initials: H
authors.lastname: Imabayashi
authors.forename: Takashi
authors.initials: T
authors.lastname: Asazuma
authors.forename: Koichi
authors.initials: K
authors.lastname: Nemoto
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D015519:Bone Density; D001863:Bone Screws; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae / Q000601:surgery*; D008297:Male; D008422:Materials Testing; D008875:Middle Aged; D013122:Spinal Diseases / Q000601:surgery*; D013123:Spinal Fusion / Q000379:methods*; D019415:Torque