OSTEOMETRIC ANALYSIS OF EAR OSSICLES IN POPULATION OF RAJASTHAN.

Background: It has been long known fact that mammalian ear ossicles have evolved from transformation of hyomandibular cartilage, quadrate and articular bone which transmits sound waves to inner ear. Aims and objectives: This study was an attempt to analyse morphometry of three ear ossicles and to deduce a correlation between their dimensions. Material and methods: 30 human cadavers were dissected to extract the temporal bones of both the sides and the ear ossicles were procured and all the ear ossicles were analysed for their osteometric dimensions using medcalc software. Observation and conclusion: The distance between the tympanic part of facial nerve and the ossicles were also noted approximately 3.02 mm as it is an important structure to be preserved in ossiculoplasty. A positive correlation was found between the dimensions and the respective weights of the ossicles which is useful for designing the ossicular implants. Key words: Ear ossicles, facial nerve, Osteometric analysis, middle ear, digital vernier calliper Introduction: Middle ear bones have evolved from hyomandibular cartilage of amphibians, reptiles and birds which suspends upper jaw from skull. These transmits sound wave into inner ear. In mammals two ear ossicles malleus and incus have been derived from quadrate and articular bone which in lower land vertebrates intervene between lower jaw and skull bone [1].Thus any deformity or damage to the ossicles may lead to conductive hearing loss which may be corrected by using middle ear prosthesis. Thus this study was an attempt to analyse morphometry of the three ear ossicles and also to deduce any correlation between their dimensions so as to aid the prosthesis design and its manufacture. Material and method:- Present study was performed in 30 human cadavers. The skull bone was confiscated and brain was removed carefully according to Cunningham’s manual of practical anatomy. The tegmen tympani was chipped off by using micro motor, chisel and hammer and the three ear ossicles were removed and the dimensions were taken by digital vernier calliper with resolution of 0.01mm. Weight was taken by digital analytical balance with the sensitivity of 0.01mg. The course of facial nerve was also observed and its distance with the ossicles was also measured with digital vernier calliper. All the results which were obtained were analysed using medcalc software. The angle of incus was measured using sketch up pro 2014 software. Result and observation: Mean distance was calculated from head of malleus to the tympanic part of facial nerve as 3.02 mm(fig 1).