Stem revision: special implant versus primary device.

The purpose of hip revision surgery is to relieve pain and restore hip function, while improving hip biomechanics and bone stock. The entity of bone stock impairment due to lysis indicates to the surgeon which revision stem he would preferably choose. Modern literature has described several options for stem revision, ranging from primary cemented/less implants in the case of limited proximal bone defects, to special revision stems where a massive femoral bone stock impairment is present. There are many classifications of the femoral bone-stock loss in the literature but most authors seem to agree that the treatment of minimal proximal defects should be performed with primary implant stems. The need to bridge a bigger bony gap makes distal fixation a good deal. Two options are described for this purpose: the Wagner stem and modular stems. Wagner's concept consists of a distal fixation based on the interference of the straight tapered titanium alloy stem at the level of the femoral isthmus, while longitudinal fins provide rotational stability. A wide variety of modular stems was lately developed to prevent major complication associated to the Wagner's stem, but some new problems arose from proximal overfill of the canal, difficult in assembly and fretting corrosion. Early experience with the new ZMR taper (Zimmer, Warsaw, IN, USA) modular revision stem is reported.