Understanding the complex anatomy of the middle turbinate via educational origami *

Background: The middle turbinate is an important landmark during endoscopic sinus procedures. Well orientation of the appropriate planes, attachments and relations of the different parts of the middle turbinate helps achieve safe and effective endoscopic sinus surgery. Aim of work: To discuss the complex anatomy of the middle turbinate via a paper model of the middle turbinate and to validate its impact on clarifying the planes and attachments of the different parts of the middle turbinate. Study design: descriptive. Methods: Utilizing origami, a paper model of the middle turbinate was introduced by the author resembling its three parts. The model was used to demonstrate the planes and attachments of the different parts of the middle turbinate. Ten MCQs were administered to 76 candidates, prior and post demonstration, during three basic endoscopic sinus surgery courses. The pre and post scores were statistically analyzed. Results: The mean of pre-total score was 6.05 (range 0-10, SD 2.39) and the mean of the post-total score was 9.22 (range 7-10, SD 1.05). The difference of pre and post total score means was 3.17 (SD 2.32) which showed high statistical significance. Conclusion: The Kamel’s middle turbinate paper model is a valid educational tool. It is simple to assemble and useful to interpret the planes, attachments and relations of the different parts of MT. Moreover it has many fruitful clinical applications that may help achieve effective and safe endoscopic sinus surgery.

The middle turbinate (MT) is a vital anatomical landmark that guides the surgeon to perform safe and effective ESS (5,6,8,9) .It is composed mainly of three parts, that are oriented in different planes and have definite attachments to the lateral nasal wall, orbit and skull base (5,6,9) .
During basic ESS courses in a lot of countries within the last twenty years, the author noticed that many participants, especially young doctors, failed to understand and grasp easily the orientation and attachments of the different parts of MT.This is despite excellent lectures and/or demonstrations.This aroused the need for a simple model for the presentation of the MT and understanding its complex anatomy.
The aim of work is to demonstrate an original paper model of the MT that helps understand the planes, attachments and relations of the different parts of the MT and to validate its efficacy.1F).Then the model is used to demonstrate the following:

1-MT orientation and attachments:
The MT is composed of three parts; first, second and third parts.

2-Right and left layout of MT:
The first piece of paper only, namely short Ia & long Ib, is then rotated anticlockwise 180 o to change from the left to the right layout of the MT (Figure 2).

3-Location of bulla ethmoidalis and posterior ethmoid air cells:
Then one should be able to imagine the location of the bulla ethmoidalis anterior to the BL and the location of the posterior ethmoid behind the BL.

4-BL opening:
The model is then used to show where to penetrate the BL.The The same 10 MCQs were re-administered to the candidates.
Then the correct answers were displayed and the delegates were asked to make their own models.

Statistical analysis
Data were statistically described in terms of mean ± standard deviation (± SD), median and range, or frequencies (number of cases) and percentages when appropriate.

Results
Table 1 shows the range, mean and standard deviation of pre and post scores of each question separately and total scores.
The difference of pre and post total score means was 3.17 (SD 2.32) which showed high statistical significance (p value 0.000).
All questions, Q1-10, displayed significant statistical difference regarding pre and post scores (Figure 4).
After introduction to the model Q3 (posterior MT) and Q2

Discussion
The MT is an important landmark in ESS (5,6,8,9) .The most anterior and superior insertion of the MT is adjacent to the crista ethmoidalis of the maxilla.The posterior end is attached to the crista ethmoidalis of the perpendicular process of the palatine bone.
The area between comprises three parts.The anterior third of the MT inserts vertically into the skull base at the lateral edge of the lamina cribrosa.The middle third turns laterally across the skull base to the lamina papyracea, where it turns inferiorly.The most posterior segment becomes horizontal to form the roof of the posterior third of the middle meatus.The insertion of the MT thus lies in three different planes, sagittal, frontal and horizontal (5,6,9) .
A lot of tools have been presented to illustrate the MT including printed diagrams, plastic models, computer animation and 3D reconstruction, tri-planar and 3D CT reconstruction, virtual endoscopy, and dextroscope virtual reality, fresh cadavers and/ or dry skulls (5,10,11) .Unfortunately, many of these models do not reach final conclusion of MT anatomy regarding planes, attachments and/or relations of the different parts.Printed diagrams are helpful but two dimensions (6,9) .Computer animation and 3D reconstruction are informative but in most of the cases fail to achieve full awareness of the middle turbinate especially by young doctors.Tri-planar and 3D CT reconstruction are very beneficial but sometimes difficult to interpret by inexperienced surgeons (12,13) .The plastic models are useful but usually small in size and difficult to demonstrate all details of planes, attachments and relations of the MT (14) .Virtual endoscopy and dextroscope virtual reality are promising but expensive and looking for further developments (10,11) .Dry skulls are good especially when sagittally cut but unfortunately it is usually hard to obtain in many centers.Moreover, the bony skeleton of the middle turbinate is relatively friable and missing in many dry skulls (15) .
Fresh cadavers are exceptional, they offer true dimensions and configuration of the MT but they are expensive and not always available (5) .
The middle turbinate exhibiting three different plans, coronal, axial and sagittal and being attached to many nearby important structures including the skull base and orbit usually remains a big challenge to inexperienced endoscopic surgeons.Losing orientation during endoscopic surgery may lead to missed pathology and/or insult to skull base and /or orbit (5) .rior third part were 64.5%, 52.6 and 48.7% respectively.These awareness increased to 98.7%, 94.7 and 96.1% respectively after model presentation.The differences were statistically significant (p value 0.000, 0.000 and 0.000).

Origami is the
The BL is the second part of the MT (5,6,8,9) .Question 4 aiming this point was answered correctly by 71.1% of the participants before model demonstration and by 100% after.The difference was statistically significant (p value 0.000) The BL is rectangular in shape (8) .Question 5 which targeted this point was already known by 61.8% of participants before the model being presented and by 94.7% after.The difference was statistically significant (p value 0.000).
Most literature usually stress upon the fact that the BL is attached to the lamina papyracea, a fact concentrated upon to avoid insult to the orbit during ESS (5,6,8,9) .Unfortunately, this usually gives the false impression that the BL has only one attachment.
Question 6 addressed the fact that the BL has four different attachments and was correctly answered by 69.7% before model presentation and increased to 96.1% after.The difference was statistically significant (p value 0.000).
Few references highlight that the BL is attached superiorly to the skull base (6,8) .And unfortunately most anatomical and endoscopic references do not emphasize the medial and inferior attachments of the BL, being to the first and third parts of the MT respectively.This was emphasized before model presentati- In general all questions (Q1-10) disclosed significant statistical difference regarding pre and post scores separately.And the difference of pre and post total score means was 3.17 (SD 2.32) which showed high statistical significance (p value 0.000).This emphasizes the efficacy of the MT paper model in increasing the awareness of the orientation, planes of the different parts of the MT, location and shape of BL and the four attachments of the BL.
Moreover the current novel paper model of the MT offers some more clinical applications.The BL separates the bulla ethmoidalis anteriorly and the posterior ethmoid air cells posteriorly (5,6,8,9) .This is smartly demonstrated by the MT model.
The BL is the corridor through which one can proceed from the anterior ethmoids to the posterior ethmoids.This should begin by opening of the BL inferior and medial and never superior and/or lateral (5.6.9) .The paper model is used to demonstrate this step simply.The insult to the orbit and/or skull base are amongst the possible most serious major complications during ESS (4,5,7,9) .
The model is utilized to demonstrate how to perform safe surgery.This is achieved by clarifying the possibility of the insult to the skull base and/or orbit in case of superior and/or lateral opening of the BL.Furthermore, floppy MT may lead to synechia formation and the recurrence of sinusitis (16) .It is worthy to mention that some anatomical variations and/ or pathological abnormalities may obviate making full use of the MT as a landmark (6,17) .Moreover, in recurrent cases, the MT may be mutilated, amputated, cut or adherent to lateral nasal wall.This may preclude utilizing the MT as a navigator in many revision surgeries.

Conclusion
The Kamel's MT paper model is a valid educational tool.It is simple to assemble and useful to interpret the planes, attachments and relations of different parts of MT.Moreover it has many fruitful clinical applications to achieve safe and effective ESS.

A
paper model of the MT was introduced by the author to resemble its three parts via origami.The model was utilized to demonstrate the planes and attachments of the MT.Before and after the demonstration, 10 MCQs (Appendix 1) were administered to 76 candidates during three basic ESS courses held in Egypt (21, 31 and 24 delegates respectively).Questions 1-3 aim the orientation and planes of the three parts of the MT, Questions 4-5 target the location and shape of basal lamella (BL) and questions 6-10 address the different attachments of the BL.Correct answer was scored one and the incorrect zero.Each candidate supplied his/her age, degree, position, province, years of experience of ENT and ESS and number of previous ESS courses attended.Candidates with missing personal data and/or incomplete answers were excluded.The paper model of the three parts of the MT: A sheet of paper (A4) is cut longitudinally into two equal parts, namely I and II (Figure 1A).Each piece of paper is then bent perpendicularly into two unequal parts, one-third and two-thirds namely short Ia & long Ib and short IIa & long IIb, respectively (Figure 1B & C).The short parts of both pieces of paper namely Ia and IIa are applied on each other, in a coronal plane whereas the long part of paper I (Ib) is rendered in a sagittal plane and the long part of paper II (IIb) is rendered in a transverse plane (Figure 1D & E).The sagittal oriented part (Ib) simulates the first anterior part of the left MT, the transversally oriented part (IIb) resembles the third posterior part of MT, and the middle duplicated coronal oriented part (Ia & IIa) resembles the BL or second middle part of MT (Figure

Figure 1 .FFigure 2 .
Figure 1.A, B) A sheet of paper (A4) is cut longitudinally into two equal parts, namely I and II.C) Each piece is bent perpendicularly into two unequal parts, one-third and two-thirds, namely short Ia & long Ib and short IIa & long IIb respectively.D,E) The short parts of both pieces of paper namely Ia and IIa are applied on each other, in a coronal plane whereas the long part of paper I (Ib) is rendered in a sagittal plane and the long part of paper II (IIb) is rendered in a transverse plane.This resembles the left MT.F) The MT is composed of three parts; first, second and third parts.The first anterior sagittal oriented first part (Ib) is perpendicular and attached to skull base (SB) superiorly.The third posterior transversely oriented part (IIb) is perpendicular and adherent to lateral nasal wall laterally (LNW).The basal lamella is the second part of the MT and is coronal oriented (Ia & IIa) and perpendicular to both the skull base superiorly and the lamina papyracea laterally.

Figure 3 .
Figure 3.The left basal lamella, visualized from front, is opened inferior and medial which is the safest location.This is away from the superior skull base and lateral lamina papyracea.
The first anterior sagittal oriented part (Ib) is parallel to lamina papyracea laterally and the nasal septum medially and perpendicular and attached to the skull base superiorly.The third posterior transversely oriented part (IIb) is parallel to nasal floor inferiorly and skull base superiorly and perpendicular and adherent to lateral nasal wall laterally.There should be a changing part between the two differently oriented first and third parts of the MT.It is the second middle part which is the BL of the MT.It is coronal oriented (Ia & IIa) and perpendicular to both the skull base superiorly and the lamina papyracea laterally.Accordingly, the BL is generally rectangular in shape and has four borders and attachments.It is attached superiorly to the skull base, laterally to the lamina papyracea, medially to the first part of the MT and inferiorly to the third part of the MT (Figure1F).
BL is penetrated inferior and medial which is the safest site.A pen is used to follow the lateral aspect of the first sagittal part of MT from anterior to posterior and one should appreciate the change from the sagittal plane to coronal plane of BL.Then the pen is used to follow the inferior aspect of the third transverse part of MT from posterior to anterior and one should appreciate the change from the transverse to the coronal plane of BL.The meeting point is the safest and optimum site of opening of the BL which is then done by the tip of the pen.Then the hole is widened superior and lateral towards skull base and lamina papyracea respectively (Figure3).Opening of BL superior and/or lateral may induce skull base and/or orbit complications.
Japanese art of folding paper into decorative shapes and figures.The author utilized the art of paper folding in making a MT model.10 MCQ were designed to validate the usefulness of the MT paper model.Question 1-3 aimed the orientation of the three parts of the MT.Before model presentation, the awareness of the sagittal orientation of the first anterior part, the coronal orientation of the second middle part and the axial orientation of the poste-

Figure 4 .
Figure 4. Pre and post scores before and after demonstration of the Kamel's paper model of middle turbinate.
The importance of the integrity of the first sagittal and third transverse parts of MT are well shown by the model to avoid floppy MT.The new Kamel's MT model is easy to assemble by both the instructors and trainees.There is no need for any special materials and/or tools, just a sheet of A4 paper.It is practical, cheap and reproducible.It is simple and an onsite demo, anytime and anywhere.It can easily be interchanged between right and left layout.It is exceptional in case of beginners.In fact it is an unconventional method of MT demonstration being an interactive part during courses and/or lectures.Nonetheless, the Kamal's paper model needs training to master.It does not reflect the true dimensions, exact shape and/or precise orientation of the MT.It should be considered as a supplementary tool and does not replace other illustrative tools, cadaver dissection and/or intraoperative integration.

Table 1 .
The range, mean and standard deviation of pre and post scores of each question separately and total scores.