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Journal of Bone and Joint Surgery - British Volume, Vol 90-B, Issue 3,
308-313.
doi: 10.1302/0301-620X.90B3.19548 Copyright © 2008 by British Editorial Society of Bone and Joint Surgery Variations in acetabular anatomy with reference to total hip replacementP. E. Murtha, PhD, Research Scientist1; M. A. Hafez, FRCSEd, MD, Orthopaedic Surgeon1; B. Jaramaz, PhD, Director1; and A. M. DiGioia, III, MD, Orthopaedic Surgeon2
1 Institute for Computer Assisted Orthopaedic Surgery, The Western Pennsylvania Hospital, Suite 242, Mellon Pavillion, 4815 Liberty Avenue, Pittsburgh, Pennsylvania 15224, USA. Correspondence should be sent to Dr P. E. Murtha; e-mail: pmurtha{at}icaos.org
Three-dimensional surface models of the normal hemipelvis derived from volumetric CT data on 42 patients were used to determine the radius, depth and orientation of the native acetabulum. A sphere fitted to the lunate surface and a plane matched to the acetabular rim were used to calculate the radius, depth and anatomical orientation of the acetabulum. For the 22 females the mean acetabular abduction, anteversion, radius and normalised depth were 57.1° (50.7° to 66.8°), 24.1° (14.0° to 33.3°), 25 mm (21.7 to 30.3) and 0.79 mm (0.56 to 1.04), respectively. The same parameters for the 20 males were 55.5° (47.7° to 65.9°), 19.3° (8.5° to 32.3°), 26.7 mm (24.5 to 28.7) and 0.85 mm (0.65 to 0.99), respectively. The orientation of the native acetabulum did not match the safe zone for acetabular component placement described by Lewinnek. During total hip replacement surgeons should be aware that the average abduction angle of the native acetabulum exceeds that of the safe zone angle. If the concept of the safe zone angle is followed, abduction of the acetabular component should be less than the abduction of the native acetabulum by approximately 10°.
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