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Total Hip ArthroplastyTaku Yoshida - Osaka City University Graduate School of Medicine - Osaka-City, Japan*Hiroyoshi Iwaki - Osaka City University Medical School - osaka, japanMitsuhiko Ikebuchi - Osaka City University Medical School - osaka, japanYukihide Minoda - Osaka - Osaka, JapanTakahiro Lida - Osaka City University Medical School - Osaka, JapanTessyu Ikawa - Osaka City University Medical School - osaka, japanHiroaki Nakamura - Osaka City University Medical School - osaka, japan*Email: h-iwaki@med.osaka-cu.ac.jpCup orientation of total hip arthroplasty (THA) is critical for dislocation, range of motion,polyethylene wear, pelvic osteolysis, and component migration. But, substantial error undermanual technique has been reported specially in revision THA due to a bone loss and pooranatomical landmark. We have used three kinds of navigation systems for cup positioning inprimary and revision THA. The purpose of this study is to evaluate the accuracy of navigationin revision THAs.Patients & Methods: Since 2005, consecutive 24 revision THAs were performed withvolumetric post-operative CT scan images to measure three dimensional positionings of cups.We implanted cementless hemispherical cups in 14 hips using fluoro-based navigation (FN)system (Stealth Station Tria), in 5 hips using a CT-based navigation (CTN) system(VectorVision CT Hip 3.1) and in 5 hips using fluoro-CT-based navigation (FCTN) system(VectorVision CT Hip 3.5). For all the patients, volumetric post-operative CT scan wasperformed to measure 3D cup orientation. Using 3D image-processing software (JMM, Japan)we converted all data to radiographic angles to compare different navigation system.Results: The difference from target angles of anteversion was 5.6 ± 4.9 degrees. The absolutevalue of difference from target angles of inclination was 6.5 ± 3.8 degrees. The system accuracywas 4.2±2.9 in inclination and 4.7 ± 4.1. Accuracy of three navigation system was notsignificantly different. No postoperative dislocation was observed in this series. Nocomplication related to navigation system was observed, either.Discussion: Cup malpositioning can easily occur with a conventional aligment guide especiallyin MIS THA due to complexity of a operation. In revision THAs, high incidence ofmalpositioning of cups and post operative dislocation were reported. We previously reportedthat navigation system improved the accuracy of acetabular component orientation in MIS THAcomparing to manual technique. Conventional CT-based navigation system in revision THAshad two problems. First, it was difficult to get accurate surface registration because a presenceof a bone loss prevented surface registration. Secondly, an artifact of CT images due toprevious implants during a preoperative planning. For surgical approach (removal of implants),damages of bone easily occurred before surface registration. Damages of bone changed thelandmarks for surface registration. These problems might lead the error of CT-based navigationsystem.On the other hand, FN and FCTN system does not need surface registration around acetabulum.This feature is great advantage to revision THA. Therefore, FN and FCTN system havetheoritically would be friendlier for revision THA than CTN system. We also reported FCTNsystem showed superior accuracy than CTN system [2]. In the present study, there were nosignificant differences between three kinds of navigation systems. But, our volume of patientswas too small to draw differences between systems. We need to continue this study to get morecases.However, in conclusion, an application of navigation system in revision THAs was effectiveand safe procedure to eliminates postoperative complications such as a malpositioning and postoperativedislocation,References[1] Inori F, et al. Trans ORS. 2007: 1682file:///E|/ISTA2010-Abstracts.htm[12/7/2011 3:15:47 PM]