Effect of anisotropy and drying of costal cartilage on its optical transmittance in laser reshaping of implants with 1, 2, and 3 mm in thickness.

BACKGROUND AND OBJECTIVE: Laser reshaping of cartilage is a prospective technique which can be applied for manufacturing the natural implants for otolaryngology and reconstructive surgery. Optical properties and optimal laser settings for laser reshaping of costal cartilage depend on its thickness, water content, and structural anisotropy of the tissue, in particular, the distinct orientation of collagen packing. The aim of the work is to study the effect of different collagen orientation, thickness, and drying of costal cartilage on its interaction with laser radiation. MATERIALS AND METHODS: Costal cartilage was cut along and crosswise the distinct collagen orientation. The dried and normal cartilage was used for the comparative analysis. The collagen package was studied using atomic force microscopy. The dried tissue was analyzed with thermogravimetry-differential scanning calorimetry (TG-DSC) analysis to reveal the residual water content. The optical transmittance was measured for two wavelengths λ: 1,560 and 532 nm. The reshaping of cartilage of 1-3 mm in thickness was performed with infrared laser with λ = 1560 nm while, the radiation with λ = 532 nm was used to determine the location of the IR beam. RESULTS: The transmittance of 532 nm radiation does not depend on collagen orientation and tissue drying. The IR radiation transmits better along the distinct collagen direction in dried cartilage while in normal cartilage the intensity of transmitted IR radiation increases intermittently passing crosswise and does not change dramatically with time along the collagen orientation. CONCLUSIONS: The effect of structural anisotropy of costal cartilage reveals itself in the increasing scattering of IR radiation with λ = 1,560 nm passing crosswise the collagen orientation when tissue water content is decreased. The radiation with λ = 1,560 nm is effective to perform the reshaping for cartilage of 1-3 mm in thickness; however, for 3 mm, the residual mechanical stress should be taken into account. Lasers Surg. Med. 48:887-892, 2016. © 2016 Wiley Periodicals, Inc.

Laser reshaping of costal cartilage for transplantation.

BACKGROUND AND OBJECTIVE: Laser reshaping of cartilage is a new effective and safe technique for correction of nasal septum and ear deformities. Costal cartilage is a most suitable natural material for transplantation. The problem is to obtain stable proper shape of cartilage implants. The objective of this article is to study reshaping of porcine costal cartilage for larynx stenosis surgery using Erbium glass fiber laser. MATERIALS AND METHODS: Porcine cartilage plates 3 mm in thickness were mechanically curved and irradiated (1) on one side (stretched or compressed) and (2) on both sides with different sequence. Irradiation was performed using a 1.56 µm laser with power varied from 1 to 2.5 W, exposure time from 5 to 20 seconds, spot diameter of 2.5 mm, pulse duration of 500 milliseconds, pulse repetition rate of 1.4 Hz. For each laser setting, stable curvature radius was measured during 24 hours after the experiment. Irradiated samples were analyzed by means of differential scanning calorimerty (DSC) to reveal the collagen denaturation degree. RESULTS: The optimum laser setting for stable reshaping of costal cartilage without visual thermal damage of cartilage matrix was established: laser power of 2.2 W, exposure time of 6 seconds. Nonlinear thermomechanical behavior of cartilage in the course of its laser reshaping is experimentally revealed. The influence of irradiation sequence on the curvature radius of cartilage implant is found for the first time. It is shown that (1) it is possible to use laser reshaping technique for making stable proper shape of costal cartilage, and (2) primary irradiation of compressed side followed with an irradiation of stretched side is more effective than reverse sequence of laser treatment. DSC analysis showed that thermal effect of irradiated specimens (2.58-3.79 J/g) was slightly lower that that for intact cartilage specimens and considerably lower than that for denaturation of collagen (65 ± 5 J/g). CONCLUSIONS: It is possible to use laser reshaping technique for preparation of stable cartilage implants. Nonlinear thermomechanical behavior of cartilage is experimentally revealed. The influence of irradiation sequence on curvature radius of cartilage grafts is established for the first time.