Fig. 1. Computational image-based design of 3D-printed tracheobronchial splints. (A) Stereolithography (.STL) representation (top) and virtual rendering (bottom) of the tracheobronchial splint demonstrating the bounded design parameters of the device. We used a fixed open angle of 90° to allow placement of the device over the airway. Inner diameter, length, wall thickness, and number and spacing of suture holes were adjusted according to patient anatomy (Table 1) and can be adjusted on the submillimeter scale. Bellow height and periodicity (ribbing) can be adjusted to allow additional flexion of the device in the z axis. (B) Mechanism of action of the tracheobronchial splint in treating tracheobronchial collapse in TBM. Solid arrows denote positive intrathoracic pressure generated on expiration. Hollow arrow denotes vector of tracheobronchial collapse. Dashed arrow denotes vector of opening wedge displacement of the tracheobronchial splint with airway growth. (C) Digital Imaging and Communications in Medicine (DICOM) images of the patient's CT scan were used to generate a 3D model of the patient's airway via segmentation in Mimics. A centerline was fit within the affected segment of the airway, and measurements of airway hydraulic diameter (DH) and length were used as design parameters to generate the device design. (D) Design parameters were input into MATLAB to generate an output as a series of 2D. TIFF image slices using Fourier series representation. Light and gray areas indicate structural components; dark areas are voids. The top image demonstrates a device bellow, and the bottom image demonstrates suture holes incorporated into the device design. The .TIFF images were imported into Mimics to generate an .STL of the final splint design. (E) Virtual assessment of fit of tracheobronchial splint over segmented primary airway model for all patients. (F) Final 3D-printed PCL tracheobronchial splint used to treat the left bronchus of patient 2. The splint incorporated a 90° spiral to the open angle of the device to accommodate concurrent use of a right bronchial splint and growth of the right bronchus.
Fig. 2. Pre- and postoperative imaging of patients. Black arrrows in all figures denote location of the malcic segment of the airway. White arrows designate the location/presence of the tracheobronchial splint. Asterisk denotes focal degradation of splint. All CT images are coronal minimum intensity projection (MinIP) reformatted images of the lung and airway on expiration. All MRI images are axial proton density turbospin echo MRI images of the chest. (A) Preoperative (top) and 1-month postoperative (upper middle) CT images of patient 1. Postoperative MRI (lower middle) demonstrated presence of splint around left bronchus in patient 1 at 12 months and focal fragmentation of splint due to degradation at 38 months (bottom). (B) Preoperative (top) and 1-month postoperative (upper middle) CT images of patient 2. Postoperative MRI (lower middle) demonstrated presence of splints around the left and right bronchi in patient 2 at 1 month. Note that the patient had bilateral mainstem bronchomalacia and received a tracheobronchial splint on both the left and right mainstem bronchus. (C) Preoperative (top) and 1-month postoperative (bottom) CT images of patient 3.
Fig. 3. PEEP, albumin, and immunoglobulin levels of patients after splint. Time 0 on the x axis of all graphs is the day of tracheobronchial splint implantation. (A) Control charts of PEEP ventilatory requirements for patients 1 to 3 over time. Solid line denotes the steady-state mean, and dashed lines denote upper and lower control limits. Comparison of pre- (Pre-) and postoperative (Post-op) PEEP requirements was performed using a Wilcoxon signed-rank test (α = 0.05, two-sided). (B) Control chart of PEEP ventilatory requirement, control chart of serum albumin measurement, and run chart of serum IgG measurement over time for patient 2. Solid lines denote the steady-state mean, and dashed lines denote upper and lower control limits. Red arrows denote days intravenous albumin or intravenous IgG was administered. Shaded areas denote normal range of values for albumin (middle) and IgG (bottom).
Fig. 4. Mean airway caliber over time. Patient airway DH was measured over time after implantation of the 3D-printed bioresorbable material. Solid lines denote bronchi that received the tracheobronchial splint. Dashed lines are normal, contralateral bronchi for patients 1 and 3. All caliber measurements were made on expiratory-phase CT imaging using the centerline function of each isolated bronchus in Mimics. The centerline function measures DH every 0.1 to 1.0 mm along the entire segment of the isolated model. Measurements are represented as averages of all measurements along the length of the isolated affected bronchus model ± SD. Pre-op, preoperative.
- Table 1. Design parameters for pediatric tracheobronchial splints.
Patient Side of
bronchusWall
thickness
(mm)Inner
diameter
(mm)Bellow
period
(mm)Length
(mm)Spiral 1 Left 2 7 2 19 No 2 Right 2 8 2 12 No Left 2 7 2 23 Yes 3 Left 2 6.5 2 11.5 No - Table 2. Airway caliber measurements before and after implantation in three pediatric patients.
All measurements were made on expiratory scans using the centerline function of each isolated treated or contralateral normal mainstem bronchus in Mimics. (A and B) The centerline function measures DH (A) and A2 (B) every 0.1 to 1.0 mm along the entire segment of the isolated model (in this case, the mainstem bronchus). Data are means ± SD. The n listed under each mean is the number of measurements performed on each bronchus by the centerline function.
Time after operation Patient 1 Patient 2 Patient 3 Treated
sideNormal
sideTreated
left sideTreated
right sideTreated
sideNormal
side(A) Airway DH (mm) Preoperative 1.7 ± 1.3
n = 283.2 ± 0.4
n = 72.2 ± 1.0
n = 204.0 ± 0.6
n = 111.7 ± 1.3
n = 194.0 ± 1.2
n = 181 month 2.5 ± 0.4*
n = 282.9 ± 0.4
n = 74.8 ± 0.5*
n = 205.4 ± 0.6*
n = 113.6 ± 1.2*
n = 193.7 ± 1.1
n = 183 months 4.6 ± 0.3
n = 174.4 ± 0.4
n = 9— — 4.0 ± 0.1
n = 74.5 ± 0.4
n = 156 months 3.8 ± 0.4
n = 223.6 ± 0.5
n = 7— — — — 12 months 3.5 ± 0.5
n = 203.9 ± 0.5
n = 10— — — — 30 months 4.0 ± 0.9#
n = 204.5 ± 1.2
n = 10— — — — (B) Airway A2 (mm) Preoperative 4.7 ± 4.2
n = 289.8 ± 2.2
n = 79.9 ± 8.3
n = 2020.3 ± 2.6
n = 114.2 ± 4.1
n = 1915.7 ± 6.4
n = 91 month 6.9 ± 0.8*
n = 288.0 ± 2.1
n = 721.8 ± 3.1*
n = 2030.8 ± 6.0*
n = 1113.9 ± 7.0*
n = 1914.1 ± 6.4
n = 183 months 17.5 ± 2.1
n = 1716.5 ± 3.4
n = 9— — 14.9 ± 1.0
n = 722.0 ± 5.3
n = 156 months 12.1 ± 2.9
n = 2211.4 ± 3.2
n = 7— — — — 12 months 10.9 ± 2.4
n = 2011.6 ± 3.9
n = 10— — — — 30 months
Postoperative15.0 ± 6.8#
n = 2023.1 ± 11.0
n = 10— — — — *P < 0.01 versus preoperative.
#P < 0.01 versus 1 month, Student’s t test (paired, two-sided, α = 0.05).
Supplementary Materials
www.sciencetranslationalmedicine.org/cgi/content/full/7/285/285ra64/DC1
Materials and Methods
Fig. S1. Contour plot of opening displacement of the tracheobronchial splint under 15-N opening load.
Fig. S2. In vivo placement of tracheobronchial splint.
Fig. S3. Isolation and segmentation of tracheobronchial tree in Mimics.
Fig. S4. Opening displacement testing of the tracheobronchial splint on the MTS RT/30 Alliance machine.
Table S1. Compression, three-point bending, and opening displacement mechanical testing for tracheobronchial splint designs.
Table S2. Predicted changes in tracheal diameter with growth.
Table S3. Venous blood gases before and after splint implantation in patient 1.
Movie S1. Nonlinear finite element analysis demonstration of the tracheobronchial splint response to airway growth.
Additional Files
- Supplementary Material for:
Mitigation of tracheobronchomalacia with 3D-printed personalized medical devices in pediatric patients
Robert J. Morrison, Scott J. Hollister, Matthew F. Niedner, Maryam Ghadimi Mahani, Albert H. Park, Deepak K. Mehta, Richard G. Ohye, Glenn E. Green*
*Corresponding author. E-mail: gegreen{at}med.umich.edu
Published 29 April 2015, Sci. Transl. Med. 7, 285ra64 (2015)
DOI: 10.1126/scitranslmed.3010825This PDF file includes:
- Materials and Methods
- Fig. S1. Contour plot of opening displacement of the tracheobronchial splint under 15-N opening load.
- Fig. S2. In vivo placement of tracheobronchial splint.
- Fig. S3. Isolation and segmentation of tracheobronchial tree in Mimics.
- Fig. S4. Opening displacement testing of the tracheobronchial splint on the MTS RT/30 Alliance machine.
- Table S1. Compression, three-point bending, and opening displacement mechanical testing for tracheobronchial splint designs.
- Table S2. Predicted changes in tracheal diameter with growth.
- Table S3. Venous blood gases before and after splint implantation in patient 1.
- Legend for movie S1
Other Supplementary Material for this manuscript includes the following:
- Movie S1. Nonlinear finite element analysis demonstration of the tracheobronchial splint response to airway growth.
