Feedback-Controlled Laser-Mediated Cartilage Reshaping

Abstract

To demonstrate feedback-controlled lasermediated 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 ϫ 10 ϫ 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 ( = 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 la-ser ( = 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.

Analysis of Nd:YAG laser‐mediated thermal damage in rabbit nasal septal cartilage

“…As expected, degree of injury increased with energy deposition, whereas shape change decreases dramatically at 40.7 W/cm 2 due to possible desiccation and ablation of cartilage tissue (Figs. [3][4][5]. The temperature history profiles generated by laser irradiation lead to reasonably accurate damage predictions that were derived from rate constants obtained using water bath immersion heating [23].…”

“…This similarity can be seen by comparing the rate process estimates of damage radii for corresponding laser dosimetry (Figs. [3][4][5]. For example, at 6 W, 8 seconds, the rate process model predicted the damage threshold (where O ¼ 1) to be approximately 2.4 mm from the center of laser exposure-or 4.8 mm in diameter; confocal microscopy revealed a damage diameter of 4.8 mm for the same laser dosimetry.…”

“…It is believed that laser cartilage reshaping (LCR) results from thermal interactions between heat, water, and the cartilage matrix proteins [4]. Cartilage is largely composed of proteoglycans, type II collagen, and water [5][6][7].…”

In Vivo Electromechanical Reshaping of Ear Cartilage in a Rabbit Model

“…4 Of these, the corrective method found to be most appropriate has been approached subjectively, with minimal quantifiable data. 5 To overcome the limitations of conventional surgery, minimally invasive reshaping techniques (including laser, 6 radiofrequency, 7 and enzymatic digestion 8 ) have been developed. Electromechanical reshaping (EMR) of cartilage is a minimally invasive technique that was introduced previously 9 but is still experimental.…”

Use of flow cytometry to assess chondrocyte viability after laser reshaping of cartilage

“…6 The five grafts from each individual septal cartilage were randomly assigned to three experimental groups (receiving one, two, or three laser exposures) and two control groups (native tissue [negative control] or tissue denatured in 50% ethanol [positive control]). Specimens were maintained in saline prior to irradiation.…”