A trigger wire release mechanism for selectively releasing a trigger wire (22, 24) from a prosthesis retaining device, includes an elongate body member (36) and a guide member (93, 94) slidably disposed on the body member, the guide member being moveable to disengage the trigger wire (22, 24) from the retaining device, and comprising a knob (100) disposed about the body member. A locking mechanism (120) is provided for limiting the axial position of the guide member (93, 94) along the elongate body member (36). The knob (100) comprises a body portion (102) and a head portion (104), the head portion and the body member having mutually engageable members which can be engaged by rotation of the head portion to prevent the knob from sliding along the body member.
