• Mitsuru Takemoto, Shunsuke Fujibayashi, Eigo Ota, Bungo Otsuki, Hiroaki Kimura, Takeshi Sakamoto, Toshiyuki Kawai, Tohru Futami, Kiyoyuki Sasaki, Tomiharu Matsushita, Takashi Nakamura, Masashi Neo, and Shuich Matsuda.
• 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.
• Eur Spine J. 2016 Jun 1; 25 (6): 1698-705.

PurposeImage-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.MethodsFourteen 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.ResultsBased 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.ConclusionThis study provides a useful design concept for the development and introduction of patient-specific navigational templates for placing PSs.

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