NEW THREE DIMENSIONAL PREOPERATIVE PLANNING SOFTWARE WITH DIGITAL X-RAY AND CT FOR TOTAL HIP ARTHROPLASTY

Abstract

Introduction: Preoperative planning is an important issue for total hip arthroplasty (THA). We normally use a traditional handwritten method with X-ray and two-dimensional (2-D) template. This method is simple and easy to plan the THA. However the 2-D planning is not accurately analyzed for especially DDH or severe deformity. New three-dimensional (3-D) preoperative planning software (ATHENA, Soft Cube) was developed for total knee replacement. The method of this software is based on roentogen stereophotogrammetoric analysis (RSA). The software can superimpose the 3-D CT and the prosthetic CAD model onto 2 X-rays. We hypothesized that this software would improve the accuracy of preoperative THA planning compared to the 2-D planning.

Materials and Methods: Fifty patients (male/female = 2/48) underwent THA using cementless stem and cementless acetabular component. Preoperatively, two different planning Methods: were done for all hips. The conventional 2-D handwritten planning was done with a template of the total hip system based on a standard AP X-ray of the hip (Group 1). Each patient had 2 directions X-ray with a particular marker and CT around only hip. The software calculated the source position of X-ray in each view by the marker and the angle between 2 X-rays based on RSA. The software superimposed the 3-D CT hip model and the proper size prosthetic CAD model onto 2 X-rays (Group 2).

Results: The acetabular component implanted was the same as that planned in 78% (Group 1) and 90% (Group2). The stem implanted was the same as that planned in 38% (Group 1) and 68% (Group2). The stem planning with the software improved significantly compared to the 2-D templating (P< 0.05, Chi-square for independence test).

Discussion and Conclusions: CT based computer preoperative planning was introduced to improve the accuracy of THA planning and reported good results in recent years. However the CT based method depends on high quality CT and cannot use effectively X-ray. This 3-D preoperative planning software can synchronize both digital X-ray and CT and define proper 3-D space. The software corrects the CAD model’s angles such as ante-version and torsional abnormalities accurately and easily in the same space. We can confirm those data simultaneously and get a lot of accurate information before the surgery. This method improves the accuracy of THA.