Dmitry E. Protsenko

Viability of human septal cartilage after 1.45 µm diode laser irradiation

Chondrocyte viability following laser irradiation and reshaping has not been established for human nasal septal cartilage. Knowledge of the relationship between thermal injury and laser dosimetry is needed in order to optimize septal laser cartilage reshaping. The objective of this study was to determine the depth and width of thermal injury in human septal cartilage following laser irradiation.

In Vivo Needle-Based Electromechanical Reshaping of Pinnae: New Zealand White Rabbit Model

IMPORTANCE Electromechanical reshaping (EMR) is a low-cost, needle-based, and simple means to shape cartilage tissue without the use of scalpels, sutures, or heat that can potentially be used in an outpatient setting to perform otoplasty. OBJECTIVES To demonstrate that EMR can alter the shape of intact pinnae in an in vivo animal model and to show that the amount of shape change and the limited cell injury are proportional to the dosimetry. DESIGN, SETTING, AND SPECIMENS In an academic research setting, intact ears of 18 New Zealand white rabbits underwent EMR using 6 different dosimetry parameters (4 V for 5 minutes, 4 V for 4 minutes, 5 V for 3 minutes, 5 V for 4 minutes, 6 V for 2 minutes, and 6 V for 3 minutes). A custom acrylic jig with 2 rows of platinum needle electrodes was used to bend ears at the middle of the pinna and to perform EMR. Treatment was repeated twice per pinna, in proximal and distal locations. Control pinnae were not subjected to current application when being bent and perforated within the jig. Pinnae were splinted for 3 months along the region of the bend using soft silicon sheeting and a cotton bolster. MAIN OUTCOMES AND MEASURES The ears were harvested the day after splints were removed and before euthanasia. Photographs of ears were obtained, and bend angles were measured. Tissue was sectioned for histologic examination and confocal microscopy to assess changes to microscopic structure and cellular viability. RESULTS Treated pinnae were bent more and retained shape better than control pinnae. The mean (SD) bend angles in the 7 dosimetry groups were 55° (35°) for the control, 60° (15°) for 4 V for 4 minutes, 118° (15°) for 4 V for 5 minutes, 88° (26°) for 5 V for 3 minutes, 80° (17°) for 5 V for 4 minutes, 117° (21°) for 6 V for 2 minutes, and 125° (18°) for 6 V for 3 minutes. Shape change was proportional to electrical charge transfer, which increased with voltage and application time. Hematoxylin-eosin staining of the pinnae identified localized areas of cell injury and fibrosis in the cartilage and in the surrounding soft tissue where the needle electrodes were inserted. This circumferential zone of injury (range, 1.5-2.5 mm) corresponded to dead cells on cell viability assay, and the diameter of this region increased with total electrical charge transfer to a maximum of 2.5 mm at 6 V for 3 minutes. CONCLUSIONS AND RELEVANCE Electromechanical reshaping produced shape change in intact pinnae of rabbits in this expanded in vivo study. A short application of 4 to 6 V can achieve adequate reshaping of the pinnae. Tissue injury around the electrodes increases with the amount of total current transferred into the tissue and is modest in spatial distribution. This study is a critical step toward evaluation of EMR in clinical trials. LEVEL OF EVIDENCE NA.

Ex Vivo Electromechanical Reshaping of Costal Cartilage in the New Zealand White Rabbit Model

Determine the effective electromechanical reshaping (EMR) parameters for shape change and cell viability in the ex vivo rabbit costal cartilage model.

Mechanical analysis of cartilage graft reinforced with PDS plate.

This study attempts to characterize the biomechanical properties of a PDS‐cartilage composite graft for use in septorhinoplasty.

Electrosurgical tissue resection: a numerical and experimental study

The optimization of electrosurgical procedures requires a rigorous understanding of the electrical, thermal, mechanical and chemical events accompanying the ablation process. Modeling is indispensable and is needed to further advance this technology. This study introduces a novel tissue electrosurgical ablation model based on interstitial vapor nucleation and expansion. The model describes interstitial vapor nucleation and bubble growth using a homogeneous nulceation theory and Rayleigh equation. Electrosurgical incisions were made on beef muscle while equivalent electrical circuit patameters were monitored as a function of power settings and scalpel geometries. Thermal damage was measured using light and polarization microscopy. Results were compared with predictions produced by a numerical simulation, which modeled the tissue and electrosurgical scalpel interaction as a function of power settings and scalpel geometry.

Mechanical properties of porcine cartilage after uniform RF heating

Thermally mediated modalities of cartilage reshaping utilize localized heating of cartilage combined with mechanical deformation to achieve new geometries. We sought to determine the steady state elastic modulus of thermally modified cartilage without deformation, as this provides a constraint in mechanical models of the shape change process.

In vivo laser cartilage reshaping with carbon dioxide spray cooling in a rabbit ear model: A pilot study

Similar to conventional cryogen spray cooling, carbon dioxide (CO2) spray may be used in combination with laser cartilage reshaping (LCR) to produce cartilage shape change while minimizing cutaneous thermal injury. Recent ex vivo evaluation of LCR with CO2 cooling in a rabbit model has identified a promising initial parameter space for in vivo safety and efficacy evaluation. This pilot study aimed to evaluate shape change and cutaneous injury following LCR with CO2 cooling in 5 live rabbits.

Effect of bath water temperature and immersion time on bend angle during cartilage thermoforming

Much interest has been placed on the permanent reshaping of cartilage for facial reconstructive surgery using lasers. An alternate way to reshape cartilage is to heat the tissue in a water bath while maintaining the specimen in mechanical deformation. The objective of this study was to measure the circular bend angle of a cartilage specimen produced by varying the temperature and immersion time in a water bath. Rectangular cartilage specimens (18 x 4 x 1.5 mm) were bent in a semicircular jig (diameter 11 mm) and then immersed in a saline bath at temperatures between 50 - 80°C. The immersion times were 5, 20, 80, 160 and 320 seconds at each temperature. The distance between the ends of each specimen was measured before reshaping and at 15 minutes and 24 hours after immersion in order to calculate the resulting bend angle. The largest bend angle occurred in the specimen immersed in saline at 74°C for 320 seconds, illustrating a definite thermal influence on the physical shape of the cartilage sample. The critical immersion times and bath temperatures where definite shape change occurred were determined.

Monitoring of electrical peoperties during cartilage reshaping

A new non-thermal method of altering the shape of cartilage to create mechanically stable new morphologies was developed using low DC voltage electric fields (electroforming). In cartilage electroforming, voltage is applied to the surfaces of cartilage specimens held in mechanical deformation by a jig made of two large surface area electrodes for 2-5 minutes. Following removal of the specimen from the jig, permanent shape change is observed. Electric resistance and mechanical stress were monitoring during electroforming. Strong correlation between resistance and stress was observed suggesting that the mechanism of stress relaxation is electrically mediated and may provide a mean to monitor electroforming.

Ultrasound monitoring of stress relaxation during laser cartilage reshaping: preliminary investigations

We used 5.0 MHz ultrasonic pulses to monitor stress relaxation in Nd:YAG (λ = 1.32 μm) laser irradiated porcine nasal septal cartilage. Cartilage is irradiated in both uniaxial compression and curved deformation. A thin beam load cell and IR thermocouple measure strain (Vpp) and temperature (°C), respectively. We show that the propagation speed of the ultrasonic pulse is indicative of permanent stress relaxation in porcine nasal septal cartilage.