Introduction:
According to the World Health Organisation, tympanic membrane (TM) perforation rates are the highest for Australian Aboriginal and Torres Strait Islander (ATSI) children1. TM perforations in ATSI children become an ongoing problem into adulthood2 and previous work from our group in remote ATSI communities in South Australia demonstrated perforation rates of 31-50% with up to 30% of individuals demonstrating activity at any one time3. TM perforations can result in hearing losses as high as 50dB4. Within Australia, ATSI children are particularly affected as data from the Australian Bureau of Statistics showed ATSI children experienced 3 times the rates of chronic otitis media (COM) as non-Indigenous Australian children3, creating a devastating public health problem and secondary educational disadvantage in this particularly vulnerable population5.
It has been generally accepted that hearing loss (HL) is greater with an increase in size of the TM perforation6. However, perforation site and the effect on hearing is more controversial with contradictory evidence regarding this6-12. Whilst early work showed worse hearing with posteroinferior based perforations13, 14, others have found posterosuperior defects to be worse11, 15and more recent work demonstrated no difference between sites4, 6, 7, 12. Theories such as loss of the round window baffle effect resulting in phase-cancellation, as well as an increase in ossicular chain abnormalities have been proposed to explain increases in HL with posterior perforations. The association between an increase in size and severity of HL4, 6, 10, 12, 16 is reinforced by bio-mechanical studies confirming the progressive loss of catenary lever ratio with enlarging perforations17.