title: Additive-manufactured patient-specific titanium templates for thoracic pedicle screw placement: novel design with reduced contact area.
abstract: Image-based navigational patient-specific templates (PSTs) for pedicle screw (PS) placement have been described. With recent advances in three-dimensional computer-aided designs and additive manufacturing technology, various PST designs have been reported, although the template designs were not optimized. We have developed a novel PST design that reduces the contact area without sacrificing stability. It avoids susceptibility to intervening soft tissue, template geometric inaccuracy, and difficulty during template fitting.
  
  
  
  Fourteen candidate locations on the posterior aspect of the vertebra were evaluated. Among them, locations that had high reproducibility on computed tomography (CT) images and facilitated accurate PS placement were selected for the final PST design. An additive manufacturing machine (EOSINT M270) fabricated the PSTs using commercially pure titanium powder. For the clinical study, 36 scoliosis patients and 4 patients with ossification of the posterior longitudinal ligament (OPLL) were treated with thoracic PSs using our newly developed PSTs. We intraoperatively and postoperatively evaluated the accuracy of the PS hole created by the PST.
  
  
  
  Based on the segmentation reproducibility and stability analyses, we selected seven small, round contact points for our PST: bilateral superior and inferior points on the transverse process base, bilateral inferior points on the laminar, and a superior point on the spinous process. Clinically, the success rates of PS placement using this PST design were 98.6 % (414/420) for scoliosis patients and 100 % (46/46) for OPLL patients.
  
  
  
  This study provides a useful design concept for the development and introduction of patient-specific navigational templates for placing PSs.
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medicine, Kyoto University, 54 Kawaharacho, Shogoin, Sakyo-ku, Kyoto, Kyoto, 606-8507, Japan. m.take@kuhp.kyoto-u.ac.jp.
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Takemoto
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medicine, Kyoto University, 54 Kawaharacho, Shogoin, Sakyo-ku, Kyoto, Kyoto, 606-8507, Japan.
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Fujibayashi
authors.affiliation: Department of Orthopaedic Surgery, Shiga Medical Center for Children, 5-7-30, Moriyama, Shiga, 524-0022, Japan.
authors.forename: Eigo
authors.initials: E
authors.lastname: Ota
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medicine, Kyoto University, 54 Kawaharacho, Shogoin, Sakyo-ku, Kyoto, Kyoto, 606-8507, Japan.
authors.forename: Bungo
authors.initials: B
authors.lastname: Otsuki
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medicine, Kyoto University, 54 Kawaharacho, Shogoin, Sakyo-ku, Kyoto, Kyoto, 606-8507, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Kimura
authors.affiliation: Department of Orthopaedic Surgery, Osaka Red Cross Hospital, 5-30 Fudegasaki-cho, Tennoji-ku, Osaka, Osaka, 543-8555, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Sakamoto
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medicine, Kyoto University, 54 Kawaharacho, Shogoin, Sakyo-ku, Kyoto, Kyoto, 606-8507, Japan.
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Kawai
authors.affiliation: Department of Orthopaedic Surgery, Shiga Medical Center for Children, 5-7-30, Moriyama, Shiga, 524-0022, Japan.
authors.forename: Tohru
authors.initials: T
authors.lastname: Futami
authors.affiliation: Sagawa Printing Co. Ltd., 5-3 Morimoto-cho Inui, Mukou, Kyoto, 617-8588, Japan.
authors.forename: Kiyoyuki
authors.initials: K
authors.lastname: Sasaki
authors.affiliation: Department of Biomedical Sciences, College of Life and Health Sciences, Chubu University, 1200 Matsumoto-cho, Kasugai, Aichi, 487-8501, Japan.
authors.forename: Tomiharu
authors.initials: T
authors.lastname: Matsushita
authors.affiliation: National Hospital Organization Kyoto Medical Center, 1-1 Mukaihata-cho, Fukakusa, Fushimi-ku, Kyoto, Kyoto, 612-0861, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Nakamura
authors.affiliation: Department of Orthopedic Surgery, Osaka Medical College, 2-7 Daigakumachi, Takatsuki, Osaka, 569-8686, Japan.
authors.forename: Masashi
authors.initials: M
authors.lastname: Neo
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medicine, Kyoto University, 54 Kawaharacho, Shogoin, Sakyo-ku, Kyoto, Kyoto, 606-8507, Japan.
authors.forename: Shuich
authors.initials: S
authors.lastname: Matsuda
mesh_terms: D006801:Humans; D019637:Orthopedic Procedures / Q000295:instrumentation / Q000379:methods; D066230:Patient-Specific Modeling; D065289:Pedicle Screws; D012600:Scoliosis / Q000601:surgery; D025321:Surgery, Computer-Assisted / Q000295:instrumentation / Q000379:methods; D013904:Thoracic Vertebrae / Q000601:surgery*; D014025:Titanium / Q000627:therapeutic use*
chemical_list: D014025:Titanium
keywords: Additive manufacturing; Patient-specific template; Pedicle screw; Rapid prototyping; Surgery; Surgical guide; Titanium
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