Abstract: The present invention relates to an implantable prosthetic sphincter device defining a closed pressure-fluid system operable by a recipient to control a body duct. The device includes an inflatable cuff (10), a fluid reservoir (11), and pump and control assembly (12) for deflating the cuff and controlling its reinflation. The pump and control assembly (12) includes an elastomeric sleeve (23) resiliently engaged around a bead (24, 25) normally to effect a fluid seal therebetween, with such engagement being selectively deformable to allow fluid flow between the elastomeric sleeve (23) and the bead (24, 25). A one-way valve (35) is provided to prevent flow directly from the pump volume (22) to the cuff (10). The bead engagement within the elastomeric sleeve (23) may form a valve between the reservoir (11) and the cuff (10) and/or between the pump volume (22) and the reservoir (11). The invention has applications in controlling urinary or faecal incontinence.