Mechanical Modeling of the Human Cricoid Cartilage Using Computer-Aided Design

Abstract

Objectives: Balloon dilation is generally considered first-line treatment for airway stenosis. Some dilation systems utilize a compliant balloon that can conform around rigid structures. Others use a noncompliant balloon that does not conform, allowing for dilation of more rigid stenoses. We hypothesized that subglottic dilation with a noncompliant balloon increases the likelihood of fracture of the cricoid when compared to a compliant balloon. Methods: Three fresh human cricoid cartilages were placed in a universal testing system to determine the expansile force necessary for cricoid fracture. Using these data, a 3D printer was used to construct a synthetic cricoid model possessing near identical physical characteristics to the human cricoid. Simulated dilation was then performed on the model using a compliant and a noncompliant balloon. Results: Human cricoid fracture occurred at 97.25 N (SD = 8.34), and the synthetic cricoid model fractured at 100.10 N (SD = 7.32). Both balloons fractured the model in every replicate experiment. Mean balloon internal pressure at fracture was 7.67 ATM (SD = 1.21) for the compliant balloon and 11.34 ATM (SD = 1.29) for the noncompliant balloon. Conclusions: These data show that fracture of the cricoid is a valid concern in balloon dilation procedures where the balloon spans the subglottis. Furthermore, the hypothesis was rejected in that the compliant balloon system was at least as likely to fracture the cricoid model as the noncompliant.

Surgical applications of three-dimensional printing: a review of the current literature & how to get started

“…In Otolaryngology, 3D printing has been used to print temporal bone models for otologic surgery simulation (77,78) as well as cricoid cartilage models that nearly identically represent the physical characteristics of human cricoid cartilage in vivo. The later models were used to assess the likelihood of cricoid fracture with balloon dilation procedures (79).…”

Effects of supramaximal balloon dilatation pressures on adult cricoid and tracheal cartilage: A cadaveric study

“…In a similar study on live rabbits, the authors proposed that balloon diameters 2.6 mm or greater than the airway can result in anterior cricoid fractures, and that inflation pressure alone had no direct correlation with mucosal injury or the probability of cricoid fracture . Studies utilized computer‐aided designs to evaluate the adult human cricoid cartilage and determined that the balloon size is the deciding factor for cricoid fracture . The anterior segment seems to be most vulnerable to dilatation, likely due to its thin and weaker framework relative to the posterior segment, although soft tissue support may also play a role.…”

“…3 Studies utilized computer-aided designs to evaluate the adult human cricoid cartilage and determined that the balloon size is the deciding factor for cricoid fracture. 7 The anterior segment seems to be most vulnerable to dilatation, likely due to its thin and weaker framework relative to the posterior segment, although soft tissue support may also play a role.…”

“…Noncompliant balloons were used in this study as it was felt that the rigid balloons were more likely to cause injury. Johnson et al 7 studied computer-designed adult cricoid cartilage without its surrounding soft tissue and concluded that both compliant and noncompliant balloons may cause cricoid fractures with equal probability. They noted that the compliant and noncompliant balloons behaved differently with increasing intraluminal pressures.…”

“…The latter is most likely vulnerable to fracture during dilatation. However, there is very little information regarding the effects of varying balloon dilatation pressures and diameters on human cricoid integrity apart from animal model studies and a computer‐designed model, all suggesting that oversized balloons may cause cricoid fractures. Although the risk of cricoid fracture is a serious concern, no study has assessed the risk of rupture with balloon dilatation of the trachea.…”