The cause of the failure of the Nucleus CI500 range, particularly the CI512 implants, remains unclear, according to Cochlear Chief Executive Chris Roberts. He said fewer than 1 percent broke. Failure causes the device to shut down without causing injury.

There is an estimated 25,000 users of the CI500 implants worldwide, including up to 1,500 users in Australia. Devices that are already implanted are not to be recalled but these could be replaced with Nucleus Freedom model implants.

Cochlear supplies 65 percent of the world market for hearing implants making it one of Australia's most successful and trusted medical brands. The Nucleus CI500 range comprise 70 percent of the company's implant sales in the current fiscal year.
The recall caused shares of Cochlear to slid 20 percent at $57.60 on Monday afternoon.

The Nucleus CI500 has helped children like three-year-old Amelie Lampard, who was born deaf and blind. At 15 months old, she was implanted with the device. Along with intervention therapy, the implant has enabled her to attend school and play more easily with her brothers.

The Royal Institute for Deaf and Blind Children said there is no need to remove implants on Australian children. Chris Rehn, the institute's chief executive, the recall covers implants that are yet to be implanted.