A cochlear implant system is described which includes an implant housing containing a stimulation processor for processing externally produced communications signals to generate electrical stimulation signals for the cochlea of an implant patient. The implant housing lies substantially in a plane and has an outer perimeter adapted to fit within a surgically prepared housing recess in skull bone of the implant patient. Multiple housing fixation features are located on the outer perimeter and cooperate to develop lateral force in the plane of the implant housing between the implant housing and adjacent skull bone of the housing recess to fixedly secure the implant housing within the housing recess.