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Poster: 27Accuracy of Acetabular Cup Positioning by Using a New AcetabularReaming Guide in Total Hip Arthroplasty*Atsushi Funayama - Keio University - Shinjyuku, JapanKenji Yamaguchi - Keio University - Shinjuku, JapanMasashi Okubo - Keio University - Shinjuku, JapanTaro Fujinaka - Keio University - Shinjuku, JapanHidenori Shimizu - Keio University - Shinjuku, JapanRiichiro Ichikawa - Keio University/Department of Orthopaedic Surgery - Tokyo, JAPANShigeru Yanagimoto - Keio University - Shinjuku, JapanYoshiaki Toyama - Keio University - Shinjuku, Japan*Email: funayama@muc.biglobe.ne.jpIntroduction: The goal of total hip arthroplasty (THA) should be to reconstruct the acetabulumby positioning the hip center as close as possible to the anatomical hip center. However, thetrue position of the anatomic hip center can be difficult to determine during surgery on anindividual basis. In 2005, we designed and produced an acetabular reaming guide to enable cupplacement in the ideal anatomical position during THA. The purpose of the present study was toexamine the accuracy of acetabular cup positioning using our acetabular reaming guide in 230cases of THA.Methods: At planning, the distance from acetabular edge to reaming center and from the centerto perpendicular of inter tear drop line by AP X-ray was measured. In operation, each of caseswas adjusted this reaming guide, indicated the reaming center and reaming with the processreamer. This guide was applied in 230 patients undergoing primary THA between April 2005and June 2009. According to the Crowe classification, 188 patients were classified as Group I,28 patients were classified as Group II, 10 patients were classified as Group III, and fourpatients were classified as Group IV.Results: At planning, the position of hip center by AP X-ray was 18.1 ± 3.5 mm in verticaloffset ( VO : the vertical height to hip center from inter tear drop line ) and 29.6 ± 3.9 mm inhorizontal offset ( HO : the horizontal distance to hip center from the vertical line through themiddle of tear drop). After operation, the position of hip center was 18.1 ± 3.8 mm in VO and29.9 ± 4.7 mm in HO. The absolute error beween planning and post-operation was 2.7 ± 3.1mm in VO and 2.9 ± 2.2 mm in HO. 199 cases (86.5%) were less than 5mm error with HO. 204cases (89.6%) were less than 5mm error with VO. The vertical height from tear drop line toinferior edge of acetabular cup was 0.5±3.5 mm. The cup inclination angle was 43.4 ± 3.5 °.The cup anteversion angle was 17.1 ± 6.7°.Discussion and conclusion: The use of our new reaming guide enabled an acetabular cupposition to be obtained during THA that closely reproduced the preoperative planning positionand the clinically ideal implantation position. Our original acetabular reaming guide is a veryuseful tool for performing reaming during THA and for ensuring accurate cup placement at theanatomical hip center.file:///E|/ISTA2010-Abstracts.htm[12/7/2011 3:15:47 PM]