An eight-year-old boy with Treacher Collins syndrome was fitted with a bone-anchored hearing aid. The audiometric result was excellent. Two years later, the abutment began to loosen and could not be tightened. It was thought that a new fixture would be required, with loss of use of the aid for three months. At surgery, bone was found to be growing over the hexagonal joint between fixture and abutment. A simple and rapid solution to this problem is described.