Long-term viability and mechanical behavior following laser cartilage reshaping

Objective: To investigate the long-term in vivo effect of laser dosimetry on rabbit septal cartilage integrity, viability, and mechanical behavior. Methods: Nasal septal cartilage specimens ( control and irradiated pairs) were harvested from 18 rabbits. Specimens were mechanically deformed and irradiated with an Nd:YAG laser across a broad dosimetry range (4-8 W and 6-16 seconds). Treated specimens and controls were autologously implanted into a subperichondrial auricular pocket. Specimens were harvested an average +/- SD of 208 +/- 35 days later. Tissue integrity, histology, chondrocyte viability, and mechanical property evaluations were performed. Tissue damage results were compared with Monte Carlo simulation models. Results: All laser-irradiated specimens demonstrated variable tissue resorption and calcification, which increased with increased dosimetry. Elastic moduli of the specimens were significantly either lower or higher than controls (all P <.05). Viability assays illustrated a total loss of viable chondrocytes within the laser-irradiated zones in all treated specimens. Histologic examination confirmed these findings. Experimental results were consistent with damage profiles determined using numerical simulations. Conclusion: The loss of structural integrity and chondrocyte viability observed across a broad dosimetry range underscores the importance of spatially selective heating methods prior to initiating application in human subjects.