title: A preclinical large animal study on a novel intervertebral fusion cage covered with high porosity titanium sheets with a triple pore structure used for spinal fusion.
abstract: OBJECTIVE
  To evaluate the osteoconductivity and the bonding strength of the newly developed interbody cage covered with the porous titanium sheet (porous Ti cage) to vertebral bodies in a sheep model.
  
  
  METHODS
  Twelve sheep underwent anterior lumbar interbody fusion at L2-3 and L4-5 using either the new porous Ti cages (Group-P) or conventional Ti cages with autogenous iliac bone (Group-C). The animals were euthanized at 2 or 4 months postoperatively and subjected to radiological, biomechanical, and histological examinations.
  
  
  RESULTS
  Computed tomography analyses showed that the ratio of bone contact area in Group-P was significantly increased at 4 months compared with that at 2 months (p = 0.01). Although the ratio of bone contact area in Group-C was significantly higher than Group-P at 2 months (p < 0.001), there was no statistically significant difference between the two groups at 4 months. Biomechanical test showed that there was no significant difference in bonding strength between the two groups at either 2 or 4 months. Histological analyses revealed that the bone apposition ratio increased significantly with time in Group-P (p < 0.001). Although Group-C showed significantly higher bone apposition ratio than Group-P at 2 months (p = 0.001), there was no statistical difference between the two groups at 4 months.
  
  
  CONCLUSIONS
  There was bone ingrowth into the porous Ti sheet, and bonding capacity of the porous Ti cage to the host bone increased with time. However, the speed of union to the bone with a porous Ti cage was marginally lower than a conventional cage along with an autogenous bone graft. Although it needs further experiment with a larger sample size, the results of the current study suggested that this material could achieve interbody fusion without the need for bone grafts.
authors.affiliation: Department of Orthopedic Surgery, Graduate School of Medicine, Hokkaido University, North-15, West-7, Kita-ku, Sapporo, Hokkaido, 060-8638, Japan. yka2q@yahoo.co.jp.
authors.forename: Katsuhisa
authors.initials: K
authors.lastname: Yamada
authors.affiliation: Department of Spine and Spinal Cord Disorders, National Hospital Organization, Hokkaido Medical Center, Sapporo, Japan.
authors.forename: Manabu
authors.initials: M
authors.lastname: Ito
authors.affiliation: Industrial Research Institute, Industrial Technology Research Development, Hokkaido Research Organization, Sapporo, Japan.
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Akazawa
authors.affiliation: Department of Oral and Maxillofacial Surgery, School of Dentistry, Health Sciences University of Hokkaido, Tobetsu-cho, Japan.
authors.forename: Masaru
authors.initials: M
authors.lastname: Murata
authors.affiliation: Division of Biomedical Engineering and Science, Faculty of Health Sciences, Hokkaido University, Sapporo, Japan.
authors.forename: Toru
authors.initials: T
authors.lastname: Yamamoto
authors.affiliation: Department of Orthopedic Surgery, Graduate School of Medicine, Hokkaido University, North-15, West-7, Kita-ku, Sapporo, Hokkaido, 060-8638, Japan.
authors.forename: Norimasa
authors.initials: N
authors.lastname: Iwasaki
mesh_terms: D000818:Animals; D016025:Bone Transplantation; D007085:Ilium / Q000637:transplantation; D008159:Lumbar Vertebrae / Q000601:surgery*; D008953:Models, Anatomic; D016348:Osseointegration; D016062:Porosity; D012756:Sheep; D013123:Spinal Fusion / Q000295:instrumentation / Q000379:methods*; D014025:Titanium
chemical_list: D014025:Titanium
keywords: Biomaterial; Bone ingrowth; Interbody fusion; Intervertebral cage; Porous titanium