58 Materials and methods The senior surgeon began using the Zweymuller (Allo- Classic) (Zimmer, Warsaw, IN) stem design in January 1988. This stem design was extended to revision THAs in March, 1988. The senior surgeon performed 210 femoral revisions between March 1988 and November 1992 using a variety of stems. 166 of these revisions were performed using cementless ﬁxation; of these, 28 were done using the Zweymuller stem design. This particular stem design was chosen for femoral revision in cases with an intact femoral meta-diaphyseal junction based upon preoperative tem- plating and intraoperative assessment of femoral bone stock, and in cases in which reconstruction of leg length and femoral offset could be preformed with this stem design. The current study was conducted to review all the revisions done using the Zweymuller stem, which repre- sented a consecutive, unselected series using this particular stem design. Demographics There were 18 men and 10 women. The mean age was 66 years (range 48–83 years). The mean BMI was 29 kg/ m2 (range 24.6–37.4 kg/m2). On average, the patients had 1.8 previous hip surgeries prior to the latest revision. Femoral revision was indicated for: failed cemented stems (18 hips), failed cementless stems (9 hips), and failed bipolar hemiarthroplasty (1 hip). The mean interval between the index hip surgery and the most recent revision was 10.2 years. Femoral bone deﬁciency was graded by a single obser- ver using the AAOS classiﬁcation system using preoperative AP and lateral radiographs [7]. Eight (29%) of the patients had no signiﬁcant femoral bone deﬁciency. Sixteen patients (57%) had only small cavitary and seg- mental bone deﬁciency near the calcar or the greater trochanter, whereas, four patients (14%) did have seg- mental deﬁciency of [2.5 cm. Stem design The Zweymuller stem design is unique in its biomaterial, geometry, and surface texture. The biomaterial is a tita- nium-alloy composed of titanium with 6% aluminum and 4% niobium (Ti-6Al-4N) used to fabricate the femoral stems. It has a rectangular cross-section. It is a wedge- shape tapered design with single-plane taper in the lateral- medial dimension while the anterior-posterior dimension remains constant. Inventory included 12 stem sizes ranging from 110 to 168 mm in length. The stem surface is not porous. The texture is slightly roughened with a mean interspace size ranging from 4 to 6 microns. It offers a 123 J Orthopaed Traumatol (2008) 9:57–62 Morse taper neck design that can accept modular femoral head components with either Co-Cr-alloy or ceramic surface. Surgical technique All revisions were done using the modiﬁed anterior approach developed by the senior surgeon [8]. This ver- satile approach can be used for either minimal-incision technique, or more extensile exposure. It has been utilized in over 7,000 THAs. We have reported the clinical efﬁcacy and outcome of revision THAs [8, 9]. This muscle splitting approach utilizes the interval between the sartorius medially, and the tensor fasciae lata laterally. The abductor mechanism is left undisturbed. Capsular release is done to expose the upper femur and the acetabulum. Acetabular revision was done in 23 patients. Femoral stem and cement removal were done by standard techniques, without the need for femoral shaft osteotomy. Femoral canal preparation was performed using rasps alone. The stem size was determined by ﬁt within the canal. In selected cases, if lengthening was required from pre- operative planning, a larger stem size was selected to achieve seating at a more proximal position within the canal to restore soft tissue tension, offset, and leg length. All patients received identical prophylaxis protocol for antibiotics and thromboembolism. All patients were allowed to begin full-weight activity immediately follow- ing surgery. Follow-up All patients were entered into a prospective database. They were followed routinely at 4–6 weeks after surgery, at 6 months, 1 year, and annually thereafter. Clinical evalu- ation was done using the Harris hip scale [10]. All radiographs were taken using identical protocol with non- digital technique by the same technicians over the study period. Radiographic evaluation was done following the criteria previously published by our group [11]. Statistical analysis was done using Student t test to assess the signiﬁcance of continuous variables, and a Pearson chi-square test to assess the signiﬁcance of cate- gorical variables. Signiﬁcance was deﬁned as P value less than 0.05. All patients did give consent for inclusion in this study. Results Four patients (4 hips) did not return for a minimum 2-year follow-up, thus were excluded. The ﬁnal analysis was therefore done in the remaining 24 hips (Table 1, 2). No