Shape retention in porcine-septal cartilage following Nd : YAG (lambda=1.32 mu m) laser-mediated reshaping

Background and Objective: Photothermal heating of mechanically deformed car tilage accelerates stress relaxation and results in sustained shape change. . In this study, shape retention was measured in Nd:YAG laser reshaped porc ine septal cartilage. Materials and Methods: Specimens were laser reshaped either 4 (Group I) or 28 hours (Group II) following extract-ion from the crania. Specimens were b ent 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 resulta nt curvature with pre-irradiation measurements. Results: Mechanical deformation alone resulted in initial bend angles varyi ng from 188 degrees to 229 degrees. Resultant bend angles varied from 84 de grees to 194 degrees corresponding to shape retention varying from 58 to 75 %. Non-irradiated cartilage retained less than 46% of the original bend. Sh ape retention was greater in Group II, compared to Group I. In Group I no c ephalocranial difference in shape retention was observed, though in Group I I greater shape retention was observed in rostral specimens. Conclusion: While laser heating does significantly reshape cartilage, clini cal use of this technology will require "overbending" of the cartilage graf t to compensate for this memory effect. The degree of overbending is likely to vary with cartilage type and location. (C) 2001 Wiley-Liss, Inc.