Observation of internal stress relaxation in laser-reshaped cartilaginous implants using OCT-based strain mapping

In this study, for the first time, we apply optical coherence elastography to map and monitor slow strains caused by residual stresses in cartilaginous tissues subjected to thermomechanical laser-assisted reshaping in regimes used for the preparation of implants in otolaringological surgery. Such laser-fabricated implants made of the patient's rib cartilage have already been successfully used for treating trachea stenosis. However, intraoperative verification of sufficient stability of the implant shape still lacks reliable instrumental means. Application of the developed phase-sensitive OCT-based strain mapping revealed previously inaccessible features of slow-rate strains associated with relaxation of internal stresses and made it possible to determine an allowable post-reshaping strain rate, which can be used as an objective criterion of sufficient stability of laser-fabricated cartilaginous implants. The obtained results indicate that the OCT-based strain mapping can be used in otolaringology and maxillo-facial surgery for intraoperative stability control to enable safer and broader application of the emerging technique of laser-assisted implant fabrication.