We have been using 3-dimensional CAD software for preoperative planning as a desktop tool daily. In ordinary cases, proper size stems and cups can be decided without much labor but in our population, many arthritic hip cases have dysplastic condition and they often come to see us for hip replacement after severe defects were created over the acetabulum. It is often the case that has Crowe's type III, IV hips with leg length difference. For those cases preoperative planning using 3D CAD is a very powerful tool.

Although we only have 2-dimensional display with our computer during preoperative planning, 3 dimensional geometries are not so difficult to be understood, because we can turn the objects with the mouse and can observer from different directions. We can also display their sections and can peep inside of the geometries. It is quite natural desire that a surgeon wishes to see the planed geometries as a 3-dimensional materials. For some complicated cases, we had prepared plastic model and observed at the theater for better understanding. When we ask for a model service, each model costs $2,500. We also have small scale desk top rapid processing tool too, however it takes 2 days to make one side of pelvis. Observation of the geometries using 3-dimensional display can be its substitute without much cost and without taking much time. The problem of using 3D display had been the special goggle to mask either eye alternatively.

In the present paper, we have used a 3D display which has micro arrays of powerful prism to deriver different image for each eye without using any goggle.

Dislocation after total hip arthroplasty (THA) is one of the most serious complications. We recently modified the design of Lateral Flare femoral component (RevelationV2) with six degrees lower anteversion to reproduce the normal hip condition in Japanese. In addition, we added 10-degree slope on the posterior neck to prevent dislocation especially aimed to high anteversion cases. The purpose of this study is to verify the clinical outcome after this design modification.

Hospital records and database were retrospectively reviewed. We investigated 46 consecutive hips in 43 patients who underwent primary total hip arthroplasty using RevelationV2 from September 2007 to August 2009. All patients implicated preoperative planning using CAT scan with their informed consents.

The mean age and BMI at surgery were 63 years old and 23.1. Preoperative diagnosis was osteoarthritis (40/46: 87%), rheumatoid arthritis (2/46: 4%) or avascular necrosis of femoral head (4/46: 9%). There were 41 hips (89.2%) of Crowe I, 3(6.5%) of Crowe II and 2(4.3%) of Crowe III. Preoperative femoral neck anteversion averaged 28 degrees, whereas postoperative combined anteversion (the sum of femoral neck anteversion and anterior cup inclination) averaged 46 degrees. During follow up, 5 complications, in details, 3 mild peroneal nerve palsy, 1 pulmonary embolism and 1 dislocation following deep infection were reported. In conclusion, although no ordinal dislocation was found in this series, longer observation will need to judge appropriateness of this new component.

One of the ironies in modern technology for arthroplasty is the stress shielding in cementless stems. The aim of the development of cementless stems had been reduction of stress shielding which cement stems are not free from. In healthy femur, trabecula start form the femoral head and reach at both medial and lateral cortex in rather narrow area around lesser trochanter. So the load from the femoral head is transferred at the level on both medial and lateral side. Cement stems should have binding to the cortical bone from collar to the tip of the stem where the cement interlays, and then the load is transferred gradually from the tip to the collar, which means mild stress shielding. When distal bonding is removed, the load could be transferred as normal femur. This should have been one of the biggest requests for cementless stem. But in realty many cementless stems have difficulty to obtain a load transfer at the level like normal femur.

Since 1990, we have been mainly using lateral flare stems to obtain contact on both medial and lateral side at proximal level. In the present study, different types and length of the designs were compared by 3-Dimensional fill, 3-Dimensional fit and Finite Element Analysis.