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Original Investigation |

Treatment of Severe Porcine Tracheomalacia With a 3-Dimensionally Printed, Bioresorbable, External Airway Splint

David A. Zopf, MD, MS1; Colleen L. Flanagan, MSE2; Matthew Wheeler, PhD3; Scott J. Hollister, PhD2; Glenn E. Green, MD1
[+] Author Affiliations
1Division of Pediatric Otolaryngology, Department of Otolaryngology–Head and Neck Surgery, University of Michigan, Ann Arbor
2Departments of Biomedical Engineering, Mechanical Engineering, and Surgery, University of Michigan, Ann Arbor
3Institute for Genomic Biology and Department of Animal Sciences, University of Illinois, Urbana-Champaign
JAMA Otolaryngol Head Neck Surg. 2014;140(1):66-71. doi:10.1001/jamaoto.2013.5644.
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Published online

Importance  The study demonstrates use of a novel intervention for severe tracheobronchomalacia (TBM).

Objective  To test a novel, 3-dimensionally (3D) printed, bioresorbable airway splint for efficacy in extending survival in a porcine model of severe, life-threatening TBM.

Design and Participants  A randomized, prospective animal trial was used to evaluate an external airway splint as treatment of severe, life-threatening TBM in a multi-institutional, multidisciplinary collaboration between a biomedical engineering department and an academic animal surgery center. Six 2-month-old Yorkshire pigs underwent tracheal cartilage division and inner tracheal lumen dissociation and were randomly assigned to splint treatment (n = 3) or control groups (n = 3). Two additional pigs had the splint placed over their normal trachea.

Interventions  A 3D-printed, bioresorbable airway splint was assessed in a porcine animal model of life-threatening TBM. The open-cylindrical, bellow-shaped, porous polycaprolactone splint was placed externally and designed to suspend the underlying collapsed airway. Two additional animals were splinted without model creation.

Main Outcomes and Measures  The observer-based Westley Clinical Croup Scale was used to assess the clinical condition of animals postoperatively. Animal survival time was noted.

Results  Complete or nearly complete tracheal lumen collapse was observed in each animal, with resolution of symptoms in all of the experimental animals after splint placement. Using our severe TBM animal model, survival was significantly longer in the experimental group receiving the airway splint after model creation than in the control group (P = .0495).

Conclusions and Relevance  A multidisciplinary effort producing a computer-aided designed, computer-aided manufactured bioresorbable tracheobronchial splint was tested in a porcine model of severe TBM and was found to extend survival time. Mortality in the splinted group was ascribed to the TBM model based on the lack of respiratory distress in splinted pigs, long-term survival in animals implanted with the splint without TBM, and necropsy findings.

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Figure 1.
Airway Splint Computer-Aided Design (CAD) With 3-Dimensional Production Via Laser Sintering

A-C, Finite element analysis: A, compression, 50 Newtons (N); maximum displacement, 1.05 mm. B, Three-point bending, 50 N; maximum displacement, 2.5 mm. C, Growth load, total of 50 N; maximum displacement, 33.4 mm. D, Posterior view shows 90° splint opening. E, Oblique view highlights predesigned needle hole placement. F, Laser-sintered polycaprolactone splint.

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Figure 2.
Detailed Illustration of Surgical Development of Severe Tracheomalacia in Control Animals and Splint Placement in Experimental Animals

A, Exposure of trachea. B, Subperichondrial dissociation of internal tracheal mucosa. C, Division of overlying tracheal cartilaginous rings. D, Depiction of inferiorly based tracheal cartilage with intervening outer mucosa. E, Overlying splint sutured in place. F and G, Intraoperative photographs of severe tracheomalacia model (F) and model with splint in place (G).

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Figure 3.
Postoperative Cumulative Westley Clinical Croup Scale Score in Splinted Animals

Each line represents an individual experimental animal, each geometric figure a measurement point. X indicates death at the time of measurement or during previous time interval. The X at postoperative day 1 represents all control animals (n = 3), indicating that no control animal survived beyond 24 hours. The rightward pointing arrow across the top of the graph represents long-term survival in the 2 animals with implanted splints placed without tracheomalacia.

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