title: Compressive biomechanical properties of human nasal septal cartilage.
abstract: BACKGROUND
  Nasal septal cartilage is frequently used in nasal reconstruction and is a common source of chondrocytes for cartilage tissue engineering. The biomechanical properties of septal cartilage have yet to be fully defined and this limits the ability to compare it to the various alternative tissue-implant materials or tissue-engineered neocartilage. Given the unique structure and orientation of the septum within the nose, we sought to investigate anisotropic behaviors of septal cartilage in compression and correlate this to the concentration of glycosaminoglycans (GAG) and collagen within the cartilage.
  
  
  METHODS
  Human nasal septal cartilage specimens were tested in confined compression, with each sample analyzed in a medial orientation and also either a vertical or caudal-cephalic orientation, with the order of tests randomized. The equilibrium confined compression (aggregate) modulus, HAO, and the permeability, kp, at different offset compression levels were obtained for each compression test. After testing, the cartilage samples were solubilized, and the concentrations of GAG and collagen were obtained.
  
  
  RESULTS
  Forty-nine compression tests (24 medial, 12 vertical, 13 caudal-cephalic) were run on cartilage specimens obtained from 21 patients. There was a significant effect of orientation on compression modulus, HAO, with the vertical (0.7 +/- 0.12 MPa) and caudal-cephalic (0.66 +/- 0.01 MPa) orientations being significantly stiffer (p = 0.05) than the medial orientation (0.44 +/- 0.04 MPa). There was a trend of an orientation effect on kp at 15% offset compression (p = 0.12) and a borderline significant effect of orientation on kp at 30% offset compression (p = 0.05), demonstrating the M orientation to be more permeable than both the vertical and caudal-cephalic orientations. Both univariate and multivariate analysis did not demonstrate a significant effect of order of compression, age, gender, thickness, dry/wet weight, GAG, or collagen on either HAO, or kp values (p > 0.05).
  
  
  CONCLUSIONS
  This study provides new information on the compressive properties of septal cartilage along different axes of compression. The results demonstrate that human septal cartilage is anisotropic; the compressive stiffness is higher in the vertical and caudal-cephalic orientations than in the medial orientation. Additionally, the medial orientation tends to have the greatest permeability. The data obtained in this study provide a reference to which various craniofacial reconstruction materials and tissue-engineered neocartilage can be compared.
authors.affiliation: Division of Head and Neck Surgery, University of California, San Diego, and San Diego Veterans Affairs Healthcare System, San Diego, California, 92103, USA. jrichmon@hotmail.com
authors.forename: Jeremy D
authors.initials: JD
authors.lastname: Richmon
authors.forename: August
authors.initials: A
authors.lastname: Sage
authors.forename: W Van
authors.initials: WV
authors.lastname: Wong
authors.forename: Albert C
authors.initials: AC
authors.lastname: Chen
authors.forename: Robert L
authors.initials: RL
authors.lastname: Sah
authors.forename: Deborah
authors.initials: D
authors.lastname: Watson
authors.forename: Deborah
authors.initials: D
authors.lastname: Watston
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D016880:Anisotropy; D002358:Cartilage, Articular / Q000737:chemistry / Q000166:cytology* / Q000187:drug effects / Q000502:physiology; D002463:Cell Membrane Permeability; D003094:Collagen / Q000032:analysis; D019245:Compressive Strength; D019286:Endopeptidase K / Q000494:pharmacology; D005260:Female; D006025:Glycosaminoglycans / Q000032:analysis; D006801:Humans; D006868:Hydrolysis; D008297:Male; D008875:Middle Aged; D009300:Nasal Septum / Q000166:cytology* / Q000601:surgery; D013696:Temperature; D013997:Time Factors; D023822:Tissue Engineering / Q000379:methods
chemical_list: D006025:Glycosaminoglycans; D003094:Collagen; D019286:Endopeptidase K