ADDRESS / Dr. JYOTHI. K. C
POST GRADUATE STUDENT DEPARTMENT OF ANATOMY JSS MEDICAL COLLEGE S.S.NAGAR,
MYSORE-570015
2. / NAME OF THE INSTITUTION / JSS MEDICAL COLLEGE
S.S. NAGAR,
MYSORE-570015
3. / COURSE OF STUDY AND SUBJECT / M. D. (ANATOMY)
4. / DATE OF ADMISSION TO COURSE / 31ST MAY 2008
5. / TITLE OF THE TOPIC
A STUDY OF MORPHOLOGICAL AND MORPHOMETRICAL VARIATIONS OF HUMAN EAR OSSICLES.
RAJIV GANDHI UNIVERSITY OF HEALTH SCIENCES
BANGALORE, KARNATAKA
Annexure II
PROFORMA FOR REGISTRATION OF SUBJECTS FOR DISSERTATION
6. Brief resume of the intended work:
6.1 Need for the study:
In India incidence of deafness is 25000/million in rural areas and 7000/million in urban areas. Failure of transmission of sound from the ossicular chain to the inner ear causes an air-bone gap of 40db–60db. Various middle ear pathologies may fix or disassociate the chain leading to conductive deafness. To restore appropriate sound transmission, ossicular chain reconstruction (ossiculoplasty) is performed. Several factors have to be considered when selecting the material to use for ossiculoplasty. These include availability, stability, biocompatibility and cost effectiveness1.
The tympanic cavity or the middle ear is an irregular, laterally compressed space in the petrous part of the temporal bone. It contains three small bones, the malleus, incus and stapes, which are collectively called as auditory ossicles. These ossicles form an articulated chain, connecting the lateral and the medial walls of the tympanic cavity. They amplify and transmit the sound vibrations to the cochlear receptors in the inner ear2.
Congenital malformations of middle ear ossicles cause hearing problems3. Commonly they are absence of long process of incus and capitulum of stapes. In this case ossicular reconstruction can be carried out using incus long process homograft. This graft can be obtained from cadaver incus by drilling. Use of such grafts has resulted in an excellent improvement in hearing4.
In the present scenario with the advent of microsurgical operative techniques, it is possible to rectify these problems. Such reconstructive surgeries in early stage will help to restore the speech and hearing at the earliest, thereby help to overcome hearing disability and psychic trauma.
Precise measurements of stapes and incus are essential in the design of the middle ear implants and electromagnetic implants. The knowledge of variations of these ossicles and its morphometric data will help the otologist during reconstructive surgery and provide necessary information for the prosthesis designer5.
The ossicles attain adult size in foetal life at around six months. Ossicles obtained from new born cadaver can be preserved in ossicle bank for future use in ossiculoplasty6.
Successful ossicular repair remains a challenge, this success depends on precise dimensions of implants.
Hence in the present study an attempt is made to study the morphological and morphometrical analysis of ear ossicles.
6.2 Review of literature
A study done by Unur, Ulger and Ekinci on 40 sets of ossicles showed that incus was most stable and stapes was most variable of all. As a variation, one stapes did not have foramen obturator. The average of morphometric parameters showed that the malleus was 7.69 mm in total length, the manubrium mallei were 4.70 mm, and the incus had a total length of 6.47 mm, and the stapes had a total length of 3.22 mm with stapedial base being 2.57 mm in length and 1.29 mm in width3.
Wehrs reported congenital absence of long process of incus and capitulum of stapes in three successive generations. These three patients had identical history of hearing loss since birth with no history of ear infections and had normal tympanic membranes. All had marked conductive deafness bilaterally4.
Recently Farahani and Noornipour, in their study on twelve human stapes, showed considerable variation in size and shape, especially in the head and crura. The most constant findings were that anterior crus were straighter than the posterior crus, and the inferior arch was stronger than superior arch5.
Sarrat et al in his study on Morphological variations of human auditory ossicles in 100 cases revealed that malleus and stapes are more variable, and these variations could be related to age, sex, and race and could bring out peculiarities in the acoustic transmission7.
Anson and Bast suggested variations of malleus and incus are less frequent and less striking than in stapes. They reported that length of the malleus was 7.61-9.11 mm, length of handle 4.33-5.67 mm. Maximum width of incus was 1.73-2.49 mm and length of long process was 4.27-5.55 mm. average height of the stapes was 3.26 mm, average length anterior crura was 3.62 mm and posterior crura was 3.73 mm8.
Awengen et al in his study on stapes superstructure have found the mean diameter of the head to be 1.14 mm, mean width of anterior crus to be 0.58 mm and posterior crus 0.65 mm wide, maximum width of the footplate to be 2.48 mm and he has mentioned about study done by another author who has also measured the dimensions of stapes (mean height of the stapes- 3.55 mm, dimensions of foot plate- 1.37 X 3.00 mm) 9.
Olszewski discusses the developmental increase of distance between the ossicles, as well as the dimensions and masses of human ossicles from fetus to young adults10.
6.3 Objectives of the study:
1. To study the morphometric details (dimensions and weight) of ear ossicles of both the sides.
2. To study the morphological features and variations of ear ossicles of both the sides.
7. Materials and methods:
7.1 Source of data
1. Ear ossicles will be collected from cadavers, Department of anatomy, JSS . Medical College, Mysore.
2. Specimen will also be obtained from the dry skulls from the Department of
Anatomy, JSS Medical College, Mysore.
7.2 Method of collection of Materials:
a) Dissection method: Specimens will be collected from formalin fixed temporal bones. After removing the brain and the durameter, the middle cranial fossa will be properly exposed, the portion of arcuate eminence of petrous part of the temporal bone is removed, middle ear cavity is exposed by removing thin plate of tegmen tympani (roof of the middle ear cavity) with the help of chisel and hammer till the ear ossicles are clearly visualized and they are extracted carefully. The morphological and morphometrical aspects of the ossicles will be studied and the data will be recorded. The ossicles will then be plastinated using the method designed by Dr. N. M. Shamasundar and preserved for further study.
Number of specimens - 50.
b) Morphological and Morphometrical analysis of ear ossicles:
Specimen no:
BONE / RIGHT / LEFTMALLEUS:
a) Total length
b) Length of maubrium
c) Maximum width of head
INCUS:
a) Total length
b) Total width
c) Length of long process.
STAPES:
a) Total height
b) Length of footplate
c) Width of footplate
d) Length of Anterior crus
e) Length of Posterior crus
f) Width of head
MISCELLANEOUS:
The ear ossicle is placed on the graph paper (Graph paper has large square measuring 1cm x 1 cm, this is further divided into 100 small squares, each small square measures 1 mm x 1 mm). A good quality digital photograph is taken with the graph paper as a background using a digital camera (10 mega pixel CANON POWER SHOT). This image is transferred to the computer and magnified. Using the measuring tool (a facility in the software – ADOBE PHOTOSHOP, to measure the distance between two points) the above mentioned parameters will be recorded and analyzed. The accuracy with this method is 0.01 mm.
c) Using electronic weighing machine (SARTORIUS CP 1245), weight of individual ossicles will be measured. The accuracy with this method is 0.1 mg.
Statistical analysis:
Mean and standard deviation will be worked out to assess the average dimensions of the ear ossicles. Number and proportions will be worked out to present other morphological features. student‘t’ test will be applied to test the significance of difference in the dimensions. Chi square test will be applied to test the difference in proportions between two sides.
7.3 Does this study require any investigations or interventions to be conducted on patients or other human or animals? If so, please describe briefly;
No
7.4 Has ethical clearance been obtained from your institution in case 7.3?
Yes
8. List of references:
1. Austin D F. Acoustic mechanisms in middle ear sound transfer. Otolaryngologic
Clinics of North America.1994; 27(4): 641-652pp
2. Berkovitz B K. External and middle ear. Gray’s Anatomy. standring. 39th ed;
Elsevier Churchill Livingston. 2005; 649-661pp
3. Unur E, Ulger H, Ekinci N. Morphometrical and morphological variations in the
middle ear ossicles in the newborn. Erciyes Medical Journal. 2002; 24(2): 57-63pp
4. Wehrs R E. Congenital absence of long process of incus. Laryngoscope. 1999; 109:
192-197pp
5. Farahani R M, Nooranipour M. Anatomy and Anthropometry of human stapes.
American Journal of Otolaryngology. 2008; 29: 42-47pp
6. Rodriguez K, Shah R K, Kenna M. Anomalies of the middle and inner ear.
Otolaryngologic clinics of North America. 2007; 40: 81-96pp
7. Sarrat R, Guzman G A, Torres A. Morphological variation of human ossicular
tympani. Acta Anat.1988; 131(2):146-149pp
8. Bast T H, Anson B J. Surgical anatomy of temporal bone and ear.3rd ed;
Springfield. 1949: 337-377pp
9. Awengen D F, Kurokawa H, Nishihara S, Goode R .L. Measurements of the stapes
Super structure. Ann Otol Rhinol Laryngol. 1995; 104: 311 – 316pp
10. Olszewski. The morphometry of the ear ossicles in humans during development.
Anat anz. 1990; 171(3): 187-191pp
9. / Signature of Candidate10. / Remarks of the guide / This unique study of Morphological and morphometrical analysis of ear ossicles, done by only a few investigators in the world, will be very useful for manufacturing ear ossicle prosthesis.
11. / 11.1 Name and designation of guide / Dr. N. M. SHAMA SUNDAR
BSc., MBBS, MS, MISP
Professor & Head, Dept. of Anatomy
J.S.S. Medical College & Hospital
Mysore – 570015
11.3 Co-guide
11.4 Signature / Dr. BHARATHI. M. B.
BSc., MBBS, MS, DNB
Professor, Dept. of ENT
J.S.S. Medical College & Hospital
Mysore – 570015
11.5 Head of the Department
11.6 Signature / Dr. N. M. SHAMA SUNDAR
BSc., MBBS, MS, MISP
Professor & Head
Dept. of Anatomy
J.S.S. Medical College & Hospital
Mysore – 570015
12. / 12.1 Remarks of the Chairman and The Principal
12.2 Signature
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