Reduction of superficial thermal injury using cryogen cooling during laser-assisted cartilage reshaping of composite cartilage grafts; preliminary investigation

The lop ear deformity can treated with laser-assisted reshaping of cartilage. But thermal injury is a problem. In this situation, cryogen spray cooling (CSC) plays an important role in drawing heat from skin when laser heating. Composite cartilage grafts were excised from New Zealand rabbit ears. An incision through the perichondrium exposed a 5mm wide strip of cartilage on the posterior auricle surface. Flat specimens were manually deformed with a jig and maintained in this new position during irradiation. The exposed cartilage was irradiated on the concave surface with an Nd:YAG laser (1064 nm, 3 mm spot) at 10W, 15W, 20W. Cryogen spray cooling (CSC) was applied to the convex, nonirradiated side of the tissue to reduce thermal injury to the graft. The specimens were maintained in a deformation for 15 minutes after irradiation and serially examined for 14 days. It is concluded that higher dosimetry makes more reshaping and more superficial epidermal injury. More cryogen spray cooling makes more protection against superficial epidermal injury and less cartilage reshaping.