To the Editor:
The treatment of stenosis with malacia usually depends on stent insertion if surgery has been recused. The choice of dimensions for the stent is essential, since a stent that is too large will eventually cause granulomatous reaction and, if too small, it may migrate. These measurements are however sometimes difficult to obtain, depending on the approximate scanographic data, and on bronchoscopic data when the stenosis can be passed. Successful treatment of an anatomically complex stenosis is more difficult to obtain compared with simple cases (70% vs. 100% success rates, respectively1). All these elements suggest a potential interest in three-dimensional printing (3DP) technology to better understand the anatomy and mechanisms of airway stenosis, and to plan interventional bronchoscopy. We report herein a case of impassable complex tracheal stenosis that was efficiently treated with a stent insertion guided using a 3D printed model.
A 63-year-old woman was admitted into our center for the management of severe inspiratory dyspnea. A computed tomographic scan showed anatomically complex tracheal stenosis and also, at the same level, an infiltration of the esophageal wall. Flexible bronchoscopy showed severe inflammatory stenosis and malacia starting ∼15 mm below the vocal cords, which was impassable by a 6-mm diameter flexible bronchoscope. The precise mechanism and anatomy of the stenosis could not thus be precisely analyzed. An esophageal biopsy was performed in the area of infiltration, which showed ectopic gastric mucosa, suggesting severe gastric reflux as the etiology for this stenosis. We, thus, decided to delay an eventual surgery and proceed to temporary airway stenting, assuming an efficiency of antiacid treatment. We, therefore, realized a 3D reconstruction of the airways (VGStudioMax 2.2 software, Volume Graphics GmbH) (Fig. 1A) and then entered these data into a 3D printer (Builder Premium Medium) to build a printed model of the trachea (Fig. 1B). From this prototype, we could choose a stent that was suited to the particular anatomy of the trachea before the interventional bronchoscopy, and cover the entire area of the stenosis and distortion (Dumon BD 12/40, Novatech) (Fig. 1C).
A stent was thus efficiently inserted after balloon dilatation under rigid bronchoscopy (Fig. 1D) and the patient’s condition greatly improved after the procedure, the peak expiratory flow rose from 31% of normal readings before the procedure to 65% after.
3DP technology is progressively entering the medical field. The usefulness of this new tool has been reported in many surgical fields, but only once in interventional pulmonology. Miyazaki et al2 used a 3D-printed airway model to manage a stenosis of the bronchus intermedius quickly and efficiently using a modified Y-shaped stent in a lung-transplant recipient. Zopf et al3 and Morrison et al4 have described the surgical management of 4 successive premature children suffering from severe bronchomalacia who were treated with the aid of external 3D-printed bioresorbable airway splints.
Herein, we report the first case of impassable tracheal stenosis that was efficiently covered with a stent whose characteristics were chosen based on a printed model of the trachea. This 3D-printed prototype indicated precisely the distance between the vocal cords and the stenosis and allowed better understanding of the anatomy and extension of this stenosis. Because of the great risk of transient aggravation after dilatation and passage of the rigid bronchoscope through this inflammatory stenosis, the correct stent needed to be placed at the first attempt.
We believe 3DP represents a useful technology that can help in the management of airway diseases in selected cases. Printed models of tracheobronchial trees represent ideal tools, complementary with a computed tomographic scan data, particularly in cases of impassable stenoses. The use of this technology represents additional time and cost and is inapplicable in an emergency setting, but can shorten intervention and reduce the risk of placing a stent of inappropriate dimensions.
In the future, further applications can be advocated in the bronchoscopic area. Custom-made 3D-printed stents, perfectly adapted to a patient’s anatomy would considerably improve tolerance and reduce complication rates (migration, granulomatous reaction), particularly in cases of complex stenoses. Nevertheless, to the best of our knowledge, at this time, no 3D printer can print using a silicone that is approved for surgical use.
In conclusion, we report herein the first case of impassable tracheal complex stenosis that was efficiently managed by interventional bronchoscopy with stent insertion planned using a 3D-printed model of the trachea. This model allowed better understanding of the mechanism, the anatomy, and the extension of the stenosis, leading to precise choice of the stent and resulted in a faster and more efficient procedure.
Nicolas Guibert, MD*
Benjamin Moreno, PhD†
Christophe Hermant, MD*
*Pulmonology Department Toulouse University Hospital
†AnatomikModeling Society Toulouse, France
1. Dalar L, Karasulu L, Abul Y, et al. Bronchoscopic treatment in the management of benign tracheal stenosis: choices for simple and complex tracheal stenosis. Ann Thorac Surg. 2016;101:1310–1317.
2. Miyazaki T, Yamasaki N, Tsuchiya T, et al. Airway stent insertion simulated with a three-dimensional printed airway model. Ann Thorac Surg. 2015;99:e21–e23.
3. Zopf DA, Hollister SJ, Nelson ME, et al. Bioresorbable airway splint created with a three-dimensional printer. N Engl J Med. 2013;368:2043–2045.
4. Morrison RJ, Hollister SJ, Niedner MF, et al. Mitigation of tracheobronchomalacia with 3D-printed personalized medical devices in pediatric patients. Sci Transl Med. 2015;7:285–264.