Objectives: To have professional surgical instrumentational skills in a low-cost, readily available, personal wet lab, instead of having it on a real patient in the operation theatre or in the costly cadaveric workshops. This study was conducted to assess the feasibility of sheep's head as a valid ear, nose and throat (ENT) surgical training model and to establish a small yet comprehensive ENT wet laboratory. Methods: Sheep's heads, already checked by the veterinarian and safe to use, were collected from the abattoir. However, neck surgery specimens were specifically requested from butchery with more neck tissue and intact skin. Surgical instruments were collected from medical exhibitions, online and the industrial market. With the help of cheap functional industrial instruments, a personal surgical laboratory was established. Ovine specimens were evaluated for human simulation. Moreover, the applicability of most ENT procedures and operations was assessed by a team of six ENT surgeons including three junior surgeons and three senior ENT surgical consultants. Results: Utilising simple basic surgical instruments, a wide variety of surgeries performed with very similar conditions to human operations. Endoscopic procedures include middle ear surgeries, laryngeal fissure, tracheal resection and laryngotracheal reconstruction. Open surgeries, facial nerve decompression, dissection and repair were also performed. Moreover, fibre-optic intubation, fibre-optic bronchoscopy and foreign-body extraction training were tried. Some structures are very similar to human ones; some show mild-to-moderate differences, whereas few structures are totally absent in the sheep head. The consistency of, skin, subcutaneous tissues and bone are remarkably similar to that seen in humans. Lamb's heads are good and accepted substitute models for cadaveric specimens. This personal laboratory could be (at a certain level) a good substitute solution to repeated cadaveric workshops. Personal wet laboratories low-cost training improves surgical skills and if followed by few human cadaveric workshops, could enable the surgeon to start human operations with lower complication rate and shorter intervention time. Conclusion: Province otolaryngologist must build up his own experience before practicing on humans. Using sheep tissues do not carry any risks for disease transmission and are ethically defensible. Structural fresh, ovine heads provide a readily available, anatomically compatible, affordable, model for training. It could hone dexterity, surgical skills and teamwork behaviour well before venturing into real patient training. Anatomical variations in sheep's head such as mastoid, paranasal sinuses and skull base are minimal and do not affect the applicability of most of the procedures.
Keywords: Endoscopic ear surgery, endoscopic sinus surgery, ovine's head, reconstructive surgery, wet lab
| Introduction|| |
Surgery is a craft that relies on training, experience and extensive anatomic and physiologic knowledge. Surgeons continue to build up knowledge and experience throughout their career. However, surgical training is always a daunting issue in view of the scarcity of human cadavers and the unreal touch of simulation sessions.
Researchers have proposed a wide variety of models for the head-and-neck surgical training, ranging from virtual reality to live animals., However, none is ideal. Although fresh human cadavers offer the most obvious surrogate for living patients, this is very limited due to availability, cost and ethical issues. Furthermore, the risk of disease transmission cannot be overlooked.
On the other side, notwithstanding that simulation has gained wide acceptance in educational institutes that provide trainees with first-hand exposure to emergency situations and complex procedures to minimise risk to patients, this will not give the real tissue touch. Animal wet laboratory training is closer to real case practice and more effectively simulates life technical training., Moreover, animal rights concerns, anaesthesia and facility expenses significantly undermine the usefulness and applicability of live animals' training in surgical education.
Wet laboratory training could be the best compromise between the scarcity and risk of human cadavers and the unreal experience of simulation courses. Hence, the lamb's head validity was assessed for this purpose. Simple readily available instruments were collected from the online market, medical stores and even from the industrial market. Finally, a simple personal wet laboratory established to serve the core purpose of this personal training project.
This article describes a preliminary project of personal training wet laboratory. A team of six ear, nose and throat (ENT) surgeons including three junior surgeons and three senior ENT surgical consultants has evaluated several surgical procedures and techniques on ovine heads. Anatomic similarity, consistency and resemblance to real procedures were assessed by each one of them, separately and with the group. Detailed findings were discussed and elaborated in view of the recent literature on the utility of the ovine head as a model for surgery to show useful applications and limitations of it.
In conclusion, the ovine model proves a versatile, flexible and inexpensive teaching tool for a wide range of otolaryngology–head-and-neck surgeries. Moreover, simple readily available instruments are enough and suitable to have personal ENT head-and-neck wet laboratory [Figure 1].
| Methods|| |
Ovine heads were prepared at the slaughter and butchery shop. It is a safe bi-product from healthy animals (weight: 40–50 kg), which is prepared for human consumption. However, storage, dissections and procedures were all conducted at the personal suitable place. These heads were used fresh or stored at 5c for 1–3 days in the classic kitchen refrigerator. Live animal was not used in this study. For temporal bone surgery, unskinned head from slaughter supermarket used. While for neck surgery, specimens from butchery with a lower cut level of were more suitable.
Simple readily available instruments were obtained from the online market, medical exhibitions, medical stores and even industrial instrument stores [Figure 2], [Figure 3], [Figure 4]. Details of the utilised instruments are in the accompanying [Table 1]. Six ENT surgeons including three junior surgeons and three senior ENT surgical consultants have evaluated several surgical procedures and techniques on the ovine heads.
For the ear endoscopic procedures, the ovine head was supported inside a plastic container on its side, with adhesive tape passed around the container. Ear endoscope 0° connected to screen and basic middle ear instruments were used.
Neck surgeries and other procedures were performed on a table with the ovine head and neck stabilised inside a plastic container and supported by sandbags and/or adhesive tape. Dissection was conducted with the naked eye, loupe magnification, or digital camera with an endoscope or digital microscope using basic surgical instruments.
| Results|| |
Microscopic endoscopic ear surgery
Ovine's heads were evaluated for several microscopic endoscopy operations. Meatoplasty, myringoplasty, ossiculoplasty, stapedectomy and round window array insertion performed. Detailed procedure process and anatomic comparison studied and recorded.
Ovine heads were sufficiently appropriate surrogate models for endoscopic ear surgery training. The overall similarity to human's ear is high. Moreover, the structure's real tactile feeling is very eminent. However, the proportional dimension ratio is around 2/3 to human ossicles. In addition, mastoid aeration differences facilitate better round window access through external canal exposure than through posterior tympanostomy.
Nevertheless, anatomically, several significant differences were noted. Thin perichondrium is closely attached to the cartilage, and the external canal is boot-like and narrower (3–4 mm) than human's external ear. Moreover, while clear annuals could not be detected, tympanic mucosal folds covering the incus and stapes were evident and consistent in all the studied samples.
Regarding middle ear ossicles, incus has an equal process, stapes has a big head and a footplate that is anchored to a calcified membrane and the malleus is flattened in the middle and has a lower density than humans [Figure 5] and [Figure 6].
|Figure 5: Endoscopic middle ear view: (1) Anterior malleolar fold. (2) Malleus head. (3) Malleus handle. (4) Incus short process. (5) Incus long process. (6) Facial nerve. (7) Posterior stapedius tendon|
Click here to view
|Figure 6: Round window view: (1) Round window niche. (2) Oval window. (3) Canal of facial nerve tympanic part|
Click here to view
Endoscopic sinus surgery, Haddad flap
Haddad flap, endoscopic turbinectomy, turbinoplasty, uncinectomy, anterior ethmoidectomy and maxillary antrostomy were performed on sheep sinuses. Procedure and anatomy were assessed by the team.
The ovine head is doing very well as a training simulator for Haddad flap and turbinate procedures due to high similarity to the human septum and the inside nasal structures.
The muzzle is longer and narrower compared to human one. Therefore, the anterior part must be excised for posterior sinus access. Ovine maxillary sinus consists of three cavities communicate at the maxillary orifice, which is superior and posterior to its human position. Therefore, sheep maxillary sinus access is more challenging [Figure 7].
|Figure 7: Maxillary sinus coronal section: (1) Septal cartilage. (2) Concha of inferior turbinate. (3) Meatus. (4 and 5) Maxillary room. (6) Infraorbital bundle. (7) Sulcus of vomer. (8) Nasal cavity. (9) Vomer|
Click here to view
Frontal sinuses are more posterior and inferior, with the orifice at the posterior end of the superior turbinate. Consequently, its access is less demanding than in humans. Although tubal-like anterior ethmoidal cells access is relatively easy, the procedure to the posterior ethmoid or sphenoid sinuses cannot be done as these sinuses are absent in sheep.
Several reconstruction surgeries were performed in unskinned ovine heads. Training on ovine head provides an invaluable chance for improving surgical dexterity and skills in septoplasty, facial nerve dissection and anastomosis, rhinoplasty (osteotomy and lower lateral cartilage [LLC]) and cleft palate repair.
Sheep's nose bony and cartilaginous parts are longer, LLC lateral crus is shorter, upper lateral cartilages are different and septal cartilage is very similar to its human counterpart. However, as ovine septum is mostly cartilaginous the chance to harvest a big graft and do all kinds of grafting is quite better than in human. Moreover, with the larger area for mucopericonderium flaps dissection, drawing lines for osteotomies and practicing it could give a great training experience.
Cleft operation could be performed as well. Palate anatomy (including flap, neurovascular bundles, bony holes and hamulus) is perfectly comparable, although ovine jaw is longer, and the anterior bone is thinner. This gives a good chance for more dissection which is easier than in infants.
Intubation and laryngobronchoscopy
To maintain airway continuity, the trachea was shortened to about 15 cm then sutured to cricoid. Fibre-optic intubation, diagnostic laryngobronchoscopy and removal of foreign body were carried out.
Ovine upper respiratory tract anatomy bears significant comparison with live humans. Hence, training on intubation and bronchoscopy is very fruitful [Figure 8]. Even natural human difficulties could be simulated and dealt with effectively. However, few discrepancies are appreciable, namely, long jaws, sharp nasopharyngeal angulation and different location of secondary carinas. This unique training experience is not possible even in the most sophisticated manikin intubation models.
Larynx and trachea
Sheep head-and-neck model was evaluated for these laryngotracheal surgeries, including cricothyrotomy, cordectomy, partial laryngectomy, tracheostomy, laryngotracheoplasty with anterior cartilage grafting and tracheal resection with repair [Figure 9].
Ovine neck showed a very high similarity with a teenage boy neck. Although few differences from human anatomy were noted, such as larger arytenoid cartilage and absent thyroid incisura, these variations do not distort the procedures. For all these procedures, the model was an excellent proxy for surgical training. Dimensions, structure and consistency of larynx and trachea were a perfect match to human ones.
| Discussion|| |
Ovine specimens enable beginners to practice handling instruments and endoscope on natural tissues and anatomy. Moreover, simultaneously, manoeuvring endoscopic instruments and procedure observation on the screen could be safely first practiced on the natural sheep anatomy. It bypasses the confusion and frustration of the first confrontation with endoscopy procedures. Especially with difficult tracing of the instrument tip in the operative field with angled endoscopes. Surgical skills in handling instruments and eye–hand-brain coordination could be improved, especially for beginners.
Moreover, most critical airway maintaining procedures, such as fibre-optic tracheal intubation, could be practiced in a calm stress less setting of a personal wet laboratory. Forbes et al. have reported quick development of fibre-optic manipulation and control confidence in residents after training on life pigs. This was replicated in our study. Although life pigs training is more natural, better chance of repeated and time unbound procedures is the privilege of the non-living animal wet laboratory.
Ovine heads are widely available in abattoirs and slaughterhouses in UAE and worldwide. Being a common human food, it is easy to get clean and ready to use. Unlike live animals or cadavers, sheep heads do not require special precautions. In addition, obtaining and transporting ovine specimens are practical, easy and safe.
Sheep heads are cost affective, affordable models for training, with a price tag of only about 6 USD each.
Fortunately, ovine samples are human food products investigated and approved by slaughterhouse vets for human consumption. Therefore, the risk of contracting zoonotic diseases is very minimal or even negligible.
Using non-living fresh ovine tissue ready to be transported to the butchery for improving surgical training purposes is highly acceptable. When compared with the living animal training, wet laboratory training is plausible alternative, more ethical, yet easier, cheaper and with almost equal training perspective.
Reflection on human anatomy
When compared with human head-and-neck structure, sheep has few prominent differences. The long muzzle and spatial position of all structures hinder easy surgical access. The jaw dimensions and the quadruped positioning of the head do not match human head and jaw. Although nasal septum is almost identical to the human septum. Sinuses hold few significant shape and size differences. These differences in addition to the modification of larynx to respiration are significant surgical obstacles. Moreover, few ENT operations are not applicable due to the absence of the structure (sphenoid sinus and posterior ethmoid). Notwithstanding that, the ovine structure is valid for most of the ENT surgeries and procedures.
The ovine ear is an excellent surrogate to human counterpart. It enables surgeons to do most of the ear surgeries both endoscopically and microscopically. However, ovine mastoid has special aeration leading to change in facial nerve map. Therefore, posterior tympanostomy is not applicable.
Sheep neck fresh soft-tissue matches human neck consistency, thickness and surgical handling properties, and the hard palate has all components of human parts. In addition, the larynx with its respiratory type has the most important components of human larynx. Subglottis and trachea match human anatomy in both calibre and consistency.
Versatility for training in otolaryngology procedures
Several head-and-neck surgeries performed on the ovine head. Ovine tissues were highly matching human ones, and the training was very effective for most of the surgeries and procedures, particularly middle ear surgeries, septoplasty, haddad flap, intubation and bronchoscopy [Table 2]. Few other surgeries (maxillary, turbinate, nasal bone and parotid) could also be performed, yet not identical to human procedures. On the other hand, some surgeries are not applicable such as mastoid surgery (posterior tympanostomy), sphenoid sinus and frontal recess approach.
Simple instruments used were good, efficient and suitable for training purposes [Table 1].
No licence or academic accreditation is needed for the wet laboratory, as it is personal type and not for commercial use. However, wet laboratory holds a great potential for widespread utilisation in education and surgical training. Therefore, academic license and appropriate quality approval for wider utilisation are definitely required.
| Conclusion|| |
Ovine-based personal wet laboratory holds a promising perspective for effective surgical training and education purposes. This pilot project is meant to be the groundbreaking step into establishing a wet laboratory for beginner surgeons. It is not a substitute for human or cadaveric training. Nevertheless, it leads the way for early surgical training and knowledge. However, before formal adoption, further detailed studies for each surgery or procedure on different animals with a wider range of participants are needed.
New surgical or endoscopic techniques could be first tried in wet laboratories. It is an invaluable tool for initial training junior as well as senior surgeons. Moreover, ovine heads should prove very useful in testing and training on new instruments or surgical inventions before venturing on real human patients. With available cheap instruments, it enables the otolaryngologist to build up his own wet laboratory and start honing his practical skills.
Highly appreciating the support of Dubai municipality, especially providing safe and as requested sheep's heads. However, the continuous help and support of family and colleagues were the secret of success of such a novel project.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
| References|| |
Sadideen H, Alvand A, Saadeddin M, Kneebone R. Surgical experts: Born or made? Int J Surg 2013;11:773-8.
Ianacone DC, Gnadt BJ, Isaacson G. Ex vivo
ovine model for head and neck surgical simulation. Am J Otolaryngol 2016;37:272-8.
Javia L, Deutsch ES. A systematic review of simulators in otolaryngology. Otolaryngol Head Neck Surg 2012;147:999-1011.
Noda M, Mizuma M, Maeda S, Sakurada A, Hoshikawa Y, Endo C, et al.
Presented at the 64th
Annual Scientific Meeting of the Japanese Association for Thoracic Surgery: Wet-lab training for thoracic surgery at the laboratory animal facilities. Gen Thorac Cardiovasc Surg 2012;60:756-9.
Martinic G. The use of animals in live-tissue trauma training and military medical research. Lab Anim (NY) 2011;40:319-22.
Mladina R, Castelnuovo P, Locatelli D, Ðurić Vuković K, Skitarelić N. Training cerebrospinal fluid leak repair with nasoseptal flap on the lamb's head. ORL J Otorhinolaryngol Relat Spec 2013;75:32-6.
Forbes RB, Murray DJ, Albanese MA. Evaluation of an animal model for teaching fibreoptic tracheal intubation. Can J Anaesth 1989;36:141-4.
Delgado-Vargas B, Romero-Salazar AL, Reyes Burneo PM, Vásquez Hincapie C, de Los Santos Granado G, Del Castillo López R, et al.
Evaluation of resident's training for endoscopic sinus surgery using a sheep's head. Eur Arch Otorhinolaryngol 2016;273:2085-9.
Sisson S, Grossman JD. The Anatomy of the Domestic Animals. 4th
Revised ed. Philadelphia: Saunders; 1953.
Cordero A, Benítez S, Reyes P, Vaca M, Polo R, Pérez C, et al.
Ovine ear model for fully endoscopic stapedectomy training. Eur Arch Otorhinolaryngol 2015;272:2167-74.
Hunter EJ, Titze IR. Individual subject laryngeal dimensions of multiple mammalian species for biomechanical models. Ann Otol Rhinol Laryngol 2005;114:809-18.
Ammar Mohammed Haidar Shehadeh,
Hatta Hospital, Dubai
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9]
[Table 1], [Table 2]