Feedback-Controlled Laser-Mediated Cartilage Reshaping

Objective  To demonstrate feedback-controlled laser-mediated cartilage reshaping using dynamic measurements of tissue optical properties and radiometric surface temperatures. Design  Flat cartilage specimens were reshaped into curved configurations using a feedback-controlled laser device. Materials  Fresh porcine nasal septum, stripped of perichondrium and cut into uniform strips (25×10×1.5-2.1 mm) with a custom guillotine microtome. Interventions  Cartilage specimens secured in a cylindrical reshaping jig (2.5 cm in diameter) and irradiated with an Nd:YAG laser (λ=1.32 µm, 25 W/cm 2 , 50-Hz pulse repetition rate). During laser irradiation, radiometric surface temperature was measured along with changes in forward-scattered light from a diode probe laser (λ=650 nm, 5 mW), using a lock-in detection technique. Sequential irradiation of the specimen outer surface was made (3 laser passes). Characteristic changes in tissue temperature and light-scattering signals were used to terminate laser irradiation. Results  Effective reshaping was accomplished for both thin (1.5-mm) and thick (2.1-mm) specimens. Following reshaping, specimens were stored in saline solution at 4°C for 21 days. No return to the original flat configuration was noted during this period. Conclusions  The prototype device effectively reshapes flat native porcine cartilage into curve configurations. The use of optical and thermal signals provides effective feedback control for optimizing the reshaping process.