Elderly femoral neck fractures are often treated with cemented stems according to the reason that bone quality of the patients is not good enough to obtain the initial stability for supporting press fit cementless stem. Some elderly patients also have medullary expanding so called stovepipe canals which make initial stability of press fit stems difficult. Stems with lateral flare have some mechanical advantages to obtain proximal fixation compare to the straight stems without lateral flare. Concerning to initial stability, their vertical loads can be supported not only by proximal medial cortex but also by proximal lateral cortex. The stems also have rotational stability because of the proximal high fit and fill. As lateral flare is a transverse extension in axial section, the stem occupies the proximal canal widely. So it provides strong rotational stability. The purpose of this study was to evaluate the outcome of press fit cementless stem with lateral flare for elderly femoral neck fractures with poor bone quality and with medullary expanding.

We performed a retrospective review of the clinical records and radiograghs of consecutive 42 patients (42 hips) of femoral neck fracture operated with cement-less stems with lateral flare in 2005 and 2006. In this period, all displaced femoral neck fractures were operated using cementless stems with lateral flare (Revelation Hip System, DJO, USA) in our hospital. We could follow 24 patients for over one year. 12 of 24 patients had so called stovepipe canals according to Canal Flare Index< 3.0 (Noble et al). Minimum follow up duration was one year. The mean age of the patients at the time of operation was 78.2 years. The mean duration of follow-up was one year and three month. At the time of final follow-up, stem subsidence, stem fixation, spot welds and demarcation line at distal part of stem are assessed on radiograph. And operation time, blood loss at operation and complaint of thigh pain through all the follow up period are also investigated on clinical record.

There was no stem subsidence over 2mm and demarcation line in two cases. All stems were assessed bone-grown fixation. We could find at least one spot welds in all patients around porous coated part of the stem. The mean operation time was 60.1 min. and mean blood loss was 240.5 ml. There was no patient who complaints of thigh pain after operation.

Cementless stems with lateral flare were seemed to obtain good initial stem fixation for elderly femoral neck fracture patients even they have poor bone quality and medullary expanding.

Introduction: The success of cemenntless THA (total hip arthroplasty) mainly depends on the choices of stem, its size and accuracy of stem orientation. Selection of the optimal stem judging only by plain X-ray is not so easy. Because deformity varies in each case and it is impossible to obtain profile view of the hip. As osteoarthritic patients tend to develop external rotation contractures, radiographic position of the patients with correct rotation is very difficult. To override these problems, we have been using 3-D preoperative planning system. As for the stem selection, we have been mainly using Revelation stem, because it has a structure called lateral flare that provide proximal physiological load transfer. In the present study, the usefulness of our preoperative planning system especially for the determination of the size and stem orientation with Revelation stem.

Materials and Method: Pre-operative planning was performed in 55 osteoarthritic hips in 50 patients (10 male and 40 females), and the mean age at the operation was 64.05 years old. The 3-dimensinal geometries of the femora femora were reconstructed from the CAT scan DICOM data. The geometry of femur and components were placed on the same coordinate. Cross-sectional images from many directions were observed, and the optimal location and the size of the stem were selected. According to the result, actual operations were done. Planed sizes and selected sizes at the surgeries were compared. For several patients, post-operative CAT scans were performed, then planed stem position and actual stem position were compared.

Result: Stems preoperatively defined were used in 50hips (90.9%),1 size large ones were used in 2 hips (3.6%) and 1 size large ones were used in 3 hips (5.5%).

Discussion: As Revelation stems have very high proximal fit-and-fill, the end point of the stem insertion is very definite. The characteristics made the accuracy of the preoperative planning. So it was not so difficult to perform THA according to the preoperative planning as it had been imagined.