title: Optimal internal fixation of anatomically shaped synthetic bone grafts for massive segmental defects of long bones.
abstract: BACKGROUND
  Large segmental bone defects following tumor resection, high-energy civilian trauma, and military blast injuries present significant clinical challenges. Tissue engineering strategies using scaffolds are being considered as a treatment, but there is little research into optimal fixation of such scaffolds.
  
  
  METHODS
  Twelve fresh-frozen paired cadaveric legs were utilized to simulate a critical sized intercalary defect in the tibia. Poly-ε-caprolactone and hydroxyapatite composite scaffolds 5 cm in length with a geometry representative of the mid-diaphysis of an adult human tibia were fabricated, inserted into a tibial mid-diaphyseal intercalary defect, and fixed with a 14-hole large fragment plate. Optimal screw fixation comparing non-locking and locking screws was tested in axial compression, bending, and torsion in a non-destructive manner. A cyclic torsional test to failure under torque control was then performed.
  
  
  RESULTS
  Biomechanical testing showed no significant difference for bending or axial stiffness with non-locking vs. locking fixation. Torsional stiffness was significantly higher (P=0.002) with the scaffold present for both non-locking and locking compared to the scaffold absent. In testing to failure, angular rotation was greater for the non-locking compared to locking constructs at each torque level up to 40 N-m (P<0.05). The locking constructs survived a significantly higher number of loading cycles before reaching clinical failure at 30 degrees of angular rotation (P<0.02).
  
  
  CONCLUSIONS
  The presence of the scaffold increased the torsional stiffness of the construct. Locking fixation resulted in a stronger construct with increased cycles to failure compared to non-locking fixation.
authors.affiliation: Robert E. Carroll, MD and Jane Chace Carroll Laboratories for Orthopedic Surgery, Department of Orthopedic Surgery, College of Physicians and Surgeons, Columbia University, New York, NY, USA.
authors.forename: George C
authors.initials: GC
authors.lastname: Vorys
authors.affiliation: Robert E. Carroll, MD and Jane Chace Carroll Laboratories for Orthopedic Surgery, Department of Orthopedic Surgery, College of Physicians and Surgeons, Columbia University, New York, NY, USA.
authors.forename: Hanying
authors.initials: H
authors.lastname: Bai
authors.affiliation: Robert E. Carroll, MD and Jane Chace Carroll Laboratories for Orthopedic Surgery, Department of Orthopedic Surgery, College of Physicians and Surgeons, Columbia University, New York, NY, USA.
authors.forename: Chandhanarat
authors.initials: C
authors.lastname: Chandhanayingyong
authors.affiliation: Center for Craniofacial Regeneration, School of Dental Medicine, Columbia University, New York, NY, USA.
authors.forename: Chang H
authors.initials: CH
authors.lastname: Lee
authors.affiliation: Robert E. Carroll, MD and Jane Chace Carroll Laboratories for Orthopedic Surgery, Department of Orthopedic Surgery, College of Physicians and Surgeons, Columbia University, New York, NY, USA.
authors.forename: Jocelyn T
authors.initials: JT
authors.lastname: Compton
authors.affiliation: Robert E. Carroll, MD and Jane Chace Carroll Laboratories for Orthopedic Surgery, Department of Orthopedic Surgery, College of Physicians and Surgeons, Columbia University, New York, NY, USA.
authors.forename: Jon-Michael
authors.initials: JM
authors.lastname: Caldwell
authors.affiliation: Robert E. Carroll, MD and Jane Chace Carroll Laboratories for Orthopedic Surgery, Department of Orthopedic Surgery, College of Physicians and Surgeons, Columbia University, New York, NY, USA.
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Gardner
authors.affiliation: Center for Craniofacial Regeneration, School of Dental Medicine, Columbia University, New York, NY, USA.
authors.forename: Jeremy J
authors.initials: JJ
authors.lastname: Mao
authors.affiliation: Robert E. Carroll, MD and Jane Chace Carroll Laboratories for Orthopedic Surgery, Department of Orthopedic Surgery, College of Physicians and Surgeons, Columbia University, New York, NY, USA. Electronic address: fl127@columbia.edu.
authors.forename: Francis Y
authors.initials: FY
authors.lastname: Lee
mesh_terms: D000368:Aged; D001696:Biomechanical Phenomena; D001860:Bone Plates; D001863:Bone Screws; D018786:Bone Substitutes / Q000737:chemistry*; D016025:Bone Transplantation; D002102:Cadaver; D017886:Durapatite / Q000737:chemistry; D005260:Female; D005593:Fracture Fixation, Internal / Q000379:methods*; D006801:Humans; D008297:Male; D011091:Polyesters / Q000378:metabolism; D013314:Stress, Mechanical; D013977:Tibia / Q000473:pathology*; D023822:Tissue Engineering; D054457:Tissue Scaffolds
chemical_list: D018786:Bone Substitutes; D011091:Polyesters; C016240:polycaprolactone; D017886:Durapatite
keywords: Mechanical testing; Rigid fixation; Scaffolds; Segmental bone defects; Tissue engineering