title: Posterolateral lumbar fusion using Escherichia coli-derived rhBMP-2/hydroxyapatite in the mini pig.
abstract: BACKGROUND
  Hydroxyapatite (HA) is used as a bone graft extender for posterolateral spinal fusion in human. It is also useful as a recombinant human bone morphogenetic protein (rhBMP)-2 carrier because of its high affinity for rhBMP-2.
  
  
  OBJECTIVE
  To assess the osteoinductivity of Escherichia coli-derived rhBMP-2 (E-BMP-2) using HA granules as a carrier and to evaluate the bone-forming ability depending on the different dosages of E-BMP-2.
  
  
  METHODS
  A mini-pig lumbar posterolateral fusion model using microcomputed tomography (μCT) scanning.
  
  
  METHODS
  Thirty-one adult male mini pigs were randomized into a single control group (n=8) without E-BMP-2 and two experimental groups with two different doses of E-BMP-2 (1 mg per side, n=8 and 3 mg per side, n=15).
  
  
  METHODS
  Outcome was measured by plain radiography, manual palpation, CT, three-dimensional μCT, and histologic examinations.
  
  
  METHODS
  Bilateral intertransverse process arthrodesis was performed, and E-BMP-2 (0, 1.0, 3.0 mg per side) was implanted into the intertransverse space using HA granules as a carrier.
  
  
  RESULTS
  Three mini pigs were removed because of death. Among 28 experimental subjects, 19 animals achieved solid bony union. The fusion rates were 37.5% for control group, 71.4% for 1 mg group, and 84.6% for 3 mg group. Fusion rates were significantly different among groups (p=.031). However, there was no statistically significant difference in fusion rates between 1 and 3 mg groups (p=.587). Thirty-eight intertransverse fusion masses of 19 subjects underwent μCT scanning. The bone volumes determined by μCT were 12,603±3,240 mm(3) for control group, 18,718±3,000 mm(3) for 1 mg group, and 26,768±7,256 mm(3) for 3 mg group, and the difference between groups was statistically significant (p<.001).
  
  
  CONCLUSIONS
  This study shows that E-BMP-2 has osteoinductive activity in dose-dependent fashion, and porous HA granule is suitable for E-BMP-2 carrier in a porcine posterolateral fusion model. These preliminary findings suggest that E-BMP-2-adsorbed porous HA granules could be a novel effective bone graft substitute.
authors.affiliation: Department of Orthopedic Surgery, Korea Cancer Center Hospital, 215-4, Gongneung-dong, Nowon-gu, Seoul 139-706, Korea.
authors.forename: Chang-Bae
authors.initials: CB
authors.lastname: Kong
authors.affiliation: Department of Orthopedic Surgery, College of Medicine, Seoul National University, Seoul Metropolitan Goverment Seoul National University Boramae Medical Center, 41 Boramae-Gil, Seoul 156-707, Korea. Electronic address: spinelee@snu.ac.kr.
authors.forename: Jae Hyup
authors.initials: JH
authors.lastname: Lee
authors.affiliation: Department of Orthopedic Surgery, College of Medicine, Seoul National University, Seoul Metropolitan Goverment Seoul National University Boramae Medical Center, 41 Boramae-Gil, Seoul 156-707, Korea.
authors.forename: Hae-Ri
authors.initials: HR
authors.lastname: Baek
authors.affiliation: Department of Orthopedic Surgery, Seoul National University Hospital, 28 Yeonkeon-dong, Chongro-gu, Seoul 110-744, Korea.
authors.forename: Choon-Ki
authors.initials: CK
authors.lastname: Lee
authors.affiliation: Department of Orthopedic Surgery, Seoul National University Hospital, 28 Yeonkeon-dong, Chongro-gu, Seoul 110-744, Korea.
authors.forename: Bong-Soon
authors.initials: BS
authors.lastname: Chang
mesh_terms: D000818:Animals; D055396:Bone Morphogenetic Protein 2 / Q000008:administration & dosage / Q000627:therapeutic use*; D016025:Bone Transplantation / Q000379:methods*; D004337:Drug Carriers / Q000737:chemistry; D017886:Durapatite / Q000737:chemistry; D006801:Humans; D008159:Lumbar Vertebrae / Q000601:surgery; D008297:Male; D011994:Recombinant Proteins / Q000008:administration & dosage / Q000627:therapeutic use; D013123:Spinal Fusion / Q000379:methods*; D013552:Swine; D013556:Swine, Miniature; D016212:Transforming Growth Factor beta / Q000008:administration & dosage / Q000627:therapeutic use*
chemical_list: D055396:Bone Morphogenetic Protein 2; D004337:Drug Carriers; D011994:Recombinant Proteins; D016212:Transforming Growth Factor beta; C499469:recombinant human bone morphogenetic protein-2; D017886:Durapatite
keywords: Escherichia coli–derived rhBMP-2; Hydroxyapatite; Mini pig; Osteoinductivity; Posterolateral fusion