title: Shape retention in porcine-septal cartilage following Nd:YAG (lambda = 1.32 microm) laser-mediated reshaping.
abstract: OBJECTIVE
  Photothermal heating of mechanically deformed cartilage accelerates stress relaxation and results in sustained shape change. In this study, shape retention was measured in Nd:YAG laser reshaped porcine septal cartilage.
  
  
  METHODS
  Specimens were laser reshaped either 4 (Group I) or 28 hours (Group II) following extraction from the crania. Specimens were bent into approximately semicircular shapes and irradiated half way between the endpoints of the semicircle. Resultant bend angle was calculated based on linear measurements. Shape retention was calculated by comparing resultant curvature with pre-irradiation measurements.
  
  
  RESULTS
  Mechanical deformation alone resulted in initial bend angles varying from 188 degrees to 229 degrees. Resultant bend angles varied from 84 degrees to 194 degrees corresponding to shape retention varying from 58 to 75%. Non-irradiated cartilage retained less than 46% of the original bend. Shape retention was greater in Group II, compared to Group I. In Group I, no cephalocranial difference in shape retention was observed, though in Group II greater shape retention was observed in rostral specimens.
  
  
  CONCLUSIONS
  While laser heating does significantly reshape cartilage, clinical use of this technology will require "overbending" of the cartilage graft to compensate for this memory effect. The degree of overbending is likely to vary with cartilage type and location.
authors.affiliation: Department of Biomedical Engineering, The Johns Hopkins University School of Medicine, 720 Rutland Avenue, Baltimore, MD 21205, USA.
authors.forename: D S
authors.initials: DS
authors.lastname: Gray
authors.forename: J A
authors.initials: JA
authors.lastname: Kimball
authors.forename: B J
authors.initials: BJ
authors.lastname: Wong
mesh_terms: D000818:Animals; D007834:Lasers; D009300:Nasal Septum; D019651:Plastic Surgery Procedures; D013552:Swine