title: Experimental assessment of a novel intramedullary nail for callus distraction by the segmental bone transport method.
abstract: BACKGROUND
  Segmental bone transport (SBT) is a revolutionary method for treating extensive bone defects, and it is in wide clinical use. Although external fixation is generally used to perform SBT, it is associated with problems such as complications due to pin placement and limitations of the amount and rate of lengthening. As a way to overcome these problems we developed a novel intramedullary (IM) nail for SBT that minimizes damage to the surrounding tissue and improves the amount and rate of bone lengthening. The purpose of this study was to perform SBT in the femur of beagle dogs using the novel IM nail that we devised, and to evaluate the morphology and quality of the regenerated bone and circulation status in the surrounding tissue. We also considered the possibilities and limitations of the IM in regard to clinical application.
  
  
  METHODS
  This experiment was conducted on six beagle dogs. The novel IM nail we devised was inserted into the marrow cavity of the femur, and a 30-mm bone defect was created. After a 7-day postoperative waiting period, a bone segment was transported by 1.0 mm per day in two 0.5-mm increments. Because the nail broke in two dogs, they received only partial elongation by 15 mm over a 15-day period, with a 15-mm defect remaining, whereas full elongation by 30 mm in 30 days was performed in the other four dogs. The elongation was followed by a 30-day bone hardening period.
  
  
  RESULTS
  The macroscopic and histological results demonstrated that high-quality, new bone had replaced the 30-mm bone defect created in the femur of all six dogs. The density and number of blood vessels that had penetrated the elongated segment of bone from the surrounding muscles was greater than in the corresponding segment of the contralateral femur, which served as a control. The results imply that the traction stimulus induced vigorous angiogenesis in the surrounding tissue.
  
  
  CONCLUSIONS
  We concluded that this method has tremendous potential for clinical application, and will overcome the limitations of conventional external fixators.
authors.affiliation: Department of Orthopedic Surgery School of Medicine, Keio University, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan. Electronic address: marushun18@gmail.com.
authors.forename: Kenji
authors.initials: K
authors.lastname: Yamaguchi
authors.affiliation: Department of Orthopedic Surgery School of Medicine, Keio University, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan.
authors.forename: Yoshinari
authors.initials: Y
authors.lastname: Fujita
authors.affiliation: Department of Orthopedic Surgery School of Medicine, Keio University, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Funayama
authors.affiliation: Department of Orthopedic Surgery School of Medicine, Keio University, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan.
authors.forename: Arihiko
authors.initials: A
authors.lastname: Kanaji
authors.affiliation: Department of Orthopedic Surgery School of Medicine, Keio University, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan.
authors.forename: Michiro
authors.initials: M
authors.lastname: Susa
authors.affiliation: Department of Orthopedic Surgery School of Medicine, Keio University, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan.
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Toyama
authors.affiliation: Department of Orthopedic Surgery, Saiseikai Central Hospital, 1-4-17 Mita, Minato-ku, Tokyo 108-0073, Japan.
authors.forename: Shigeru
authors.initials: S
authors.lastname: Yanagimoto
authors.affiliation: Second Department of Surgery, Azabu University School of Veterinary Medicine, 1-17-71 Fuchinobe, Chuoh-ku, Sagamihara, Kanagawa 252-5201, Japan.
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Kageyama
mesh_terms: D000818:Animals; D001852:Bone Lengthening / Q000379:methods*; D001858:Bone Nails; D001861:Bone Regeneration; D002146:Bony Callus / Q000000981:diagnostic imaging / Q000601:surgery*; D004195:Disease Models, Animal; D004285:Dogs; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging / Q000601:surgery*; D008297:Male; D019637:Orthopedic Procedures / Q000295:instrumentation*; D011859:Radiography; D016896:Treatment Outcome