Modular femoral fixation system.

An instrument (27) for use in inserting a surgical implant into a cavity in a patient's bone characterized in that said instrument (27) comprises:an elongated rod (21) having a first end and a second end, said rod (21) having an externally threaded portion (23) adjacent said first end and an externally smooth portion (29) extending from said externally threaded portion (23) towards said second end, and said rod (21) being axially cannulated over at least a portion of its length so as to be capable of fitting over a surgical guide wire;a hollow sleeve (31) receiving said elongated rod (21), said sleeve (31) being capable of sliding movement upon said externally smooth portion (29) of the rod (21); andmeans (35) for advancing the hollow sleeve (31) along the externally smooth portion (29) of the rod (21) towards said externally threaded portion (23),said advancing means (35) positively preventing movement of the sleeve (31) along the rod (21) in a direction away from said externally threaded portion (23) while it is engaged with the sleeve (31), whereby advancement of the sleeve (31) can be stopped without relaxing the force being placed upon it by said advancing means (35).