Original Contribution
Ex vivo ovine model for head and neck surgical simulation,☆☆,

https://doi.org/10.1016/j.amjoto.2016.01.015Get rights and content

Abstract

Objective

To evaluate a fresh, ovine/sheep head and neck tissue model to teach otolaryngology-head and neck surgical techniques.

Study design

Observational animal study.

Setting

A university animal resource facility.

Methods

Tissue was collected from pre-pubescent sheep (n = 10; mean age: 4 months; mean mass: 28 kg) following humane euthanasia at the end of an in vivo protocol. No live animals were used in this study. The head and neck of the sheep were disarticulated and stored at 5 °C for 1–5 days. The tissues were tested in a variety of simulated procedures by a medical student and four fellowship-trained otolaryngology faculty. Practicality and similarity to human surgeries were assessed.

Results

While ovine head and neck structures are proportionally different, the consistencies of skin, subcutaneous tissues and bone are remarkably similar to that seen in human dissection. Particularly useful were the eyelids and orbits, facial nerve and parotid gland, mandible, anterior neck and submandibular triangle. Surgeries performed included blepharoplasty, ptosis repair, orbital floor exploration, facial nerve dissection and repair, mandibular plating, tracheotomy, laryngofissure, tracheal resection and laryngectomy. The model was also useful for flexible and microsuspension laryngoscopy.

Conclusion

Fresh, ovine tissue provides a readily available, anatomically compatible, affordable, model for training in otolaryngology-head and neck surgery. The use of sheep tissues carries a low risk for disease transmission and is ethically defensible. Structural variations in the sheep temporal bone, paranasal sinuses and skull base anatomy limit the usefulness of the model for surgical training in these areas.

Introduction

Simulation has gained wide acceptance in medical student and resident education – providing trainees with first-hand exposure to emergency situations and complex procedures while minimizing risk to patients. This is particularly true for surgical training, where simulation allows students to acquire mechanical skills and teachers to document technical competence in standardized fashion [1]. The Consortium of American College of Surgeons–Accredited Education Institutes now supports simulation as a requirement for accreditation of surgical residency programs and the Accreditation Council on Graduate Medical Education lists simulation and skill laboratories as a core competency in surgery graduate medical education [1], [2].

Researchers have proposed a wide variety of models for head and neck surgical training, ranging from virtual reality to live animals [3]. None is ideal. Fresh human cadavers offer the most obvious surrogate for living patients. Unfortunately, the 2007 United States Safe Tissue Act has markedly limited access to human tissues [4]. Further, human tissues are expensive and pose the greatest risk of disease transmission of any proposed teaching model [5]. Animal rights concerns, and anesthesia and facility expenses limit the usefulness of live animals in surgical education [6].

Tissues from non-living laboratory or farm-raised animals thus have gained in popularity. Porcine and avian models for soft tissue surgery as well as goat, sheep and dog models for airway reconstruction have been explored with mixed results [7], [8], [9], [10]. Animal hides are structurally quite different from human integument. Endoscopy using excised, mounted larynges is useful for surgical manipulation, but this model does not contain the structure needed to learn suspension laryngoscopy and intubation skills [11], [12], [13], [14], [15], [16], [17], [18].

We have explored the use of a fresh, saline-perfused sheep head and neck model for surgical simulation. This article describes our initial experience including useful applications and limitations. We believe the ovine model will prove a versatile, flexible and inexpensive teaching tool for simulation of a wide range of otolaryngology-head and neck surgeries.

Section snippets

Methods

The ovine tissue collection was conducted at the Temple University Center for Inflammation, Translational and Clinical Lung Research. Storage, dissections and procedures were all conducted at the Temple University Laboratory Animal Resource Facility (ULAR). The tissues utilized were of pre-pubescent sheep (Ovis aries), collected at the completion of live animal non-survival lung research being concurrently conducted under Institutional Animal Care and Use Committee (IACUC) approval. The sheep

Facial plastic and reconstructive procedures

The model was used for the following facial plastics procedures: 1) upper and lower lid blepharoplasty, 2) lateral canthotomy and cantholysis, 3) transcutaneous, subciliary and trans-conjunctival approaches to the orbital floor, 4) open microplating of the mandibular body and ramus fractures, 5) superficial and total parotidectomy, 6) facial nerve dissection, division, and micro-anastomosis.

Assessment

For orbital procedures the soft tissues were very similar in thickness and consistency to human tissues.

Discussion

An ideal model for surgical simulation in otolaryngology-head neck surgery should: 1) be readily available to most training programs; 2) be inexpensive; 3) have a low risk of disease transmission; 4) avoid undo ethical concerns; 5) accurately reflect normal human anatomy; and 6) be useful for the full range of head neck surgical procedures. While no single model is ideal, the ovine head and neck preparation satisfies many of these requirements.

Acknowledgements

We would like to thank the following contributors to this study: Marla Wolfson, Ph.D. for kindly donating head and neck sheep tissue following her non-survival lung study at the Center for Inflammation, Translational and Clinical Lung Research and Barbara Grandstaff, Ph.D. for kindly reviewing veterinary anatomy for accuracy and suggestion of appropriate veterinary source materials.

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    Funding: Supported in part by Department of Defense/Office of Naval Research grants N000141210810 and N000141210597.

    ☆☆

    Financial disclosures: None.

    Conflicts of interest: None.

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