Comparison Of Revision Total Hip Replacement With Fluted, Tapered, Modular Stem And Cylindrical, Nonmodular Cobalt Chrome Stem

Objective To compare the clinical and iconography results of revision total hip replacement with fluted, tapered, modular stem(TFMT) and cylindrical, nonmodular cobalt chrome stem(CNCC),and summarize the advantages and disadvantages of these two different type stems. Provide clinical evidence in prosthesis selecting.Methods we retrospectively reviewed 36 patients (38 hips) diagnosed as aseptic loosening since May1993 to August 2005. And the patients were divided into two groups according to prosthesis selecting: TFMT group include 19 patients (21 hips), 13 women and 6 men with mean age 67.32±8.19 (range, 47-86 years), CNCC group include 17 patients (17 hips), 8 women and 9 men with the mean age 63.53±6.32 (range, 45-71 years). There was no statistical discrepancy in age between two groups(P>0.05). The pre-revision femoral defects were classified according to the system of Paprosky. TFMT group: 4(19%),14(67%) and 3(14%) of the hips had typeⅡ,typeⅢa,typeⅢb femoral bone loss, CNCC group: 5(30%),10(58%) and 2(12%) of the hips had typeⅡ,typeⅢa,typeⅢb femoral bone loss.Results The mean follow-up was 8 years (5-11 years). There was no infection, dislocation and nerve or vascular injury occurred in our group. 7 hips in TFMT group and 5 hips in CNCC group got femoral fracture when clearing the femoral canal or joint reduction after stem insertion. The average leg length discrepancy improved from 3cm preoperative to 0.5cm postoperative in TFMT group and 2.5cm to 1.0cm in CNCC group. The Harris Hip Score of TFMT group improved from preoperative 46.2±8.6 to 92.2±3.5 at the latest follow-up, and CNCC group from 42.9±8.1 to 89.2±4.9 . 3 patients complain slightly thigh pain after revision but disappeared 1 year post-operation in TFMT group, and 5 hips in CNCC groups with 1 hip developed into continuous thigh pain. The X-ray showed bony fixation in 20 hips (95%) and 1(5%) with fibrous fixation in TFMT group, 14 hips (82%) with bony fixation and 3 hips (18%) with fibrous fixation in CNCC group. Osteolysis occurred in 2 hips in TFMT group with metal on polyethylene head-cup interfaces, and 4 hips in CNCC group. The average subsidence was 2.4mm (range, 0-10mm) in TFMT group and 5.0mm (range, 3-12mm) in CNCC group. There were no re-revisions of the femoral stem for any reason up to latest follow-up. Conclusions The midterm results of both fluted, tapered, modular stem and cylindrical, nonmodular cobalt chrome stem in revision total hip replacement with Paprosky typeⅡfemoral defect was encouraging. But for design and fixation principle difference, the TFMT stem got obvious superiority in leg discrepancy, Harris score, thigh pain, subsidence and stress shielding compare to CNCC stem, especially when the femoral combined with typeⅢa orⅢb defect.