title: Digital correction of magnification in pelvic x rays for preoperative planning of hip joint replacements: theoretical development and clinical results of a new protocol.
abstract: The introduction of digital radiological facilities leads to the necessity of digital preoperative planning, which is an essential part of joint replacement surgery. To avoid errors in the preparation and execution of hip surgery, reliable correction of the magnification of the projected hip is a prerequisite. So far, no validated method exists to accomplish this. We present validated geometrical models of the x-ray projection of spheres, relevant for the calibration procedure to correct for the radiographic magnification. With help of these models a new calibration protocol was developed. The validity and precision of this procedure was determined in clinical practice. Magnification factors could be predicted with a maximal margin of error of 1.5%. The new calibration protocol is valid and reliable. The clinical tests revealed that correction of magnification has a 95% margin of error of -3% to +3%. Future research might clarify if a strict calibration protocol, as presented in this study, results in more accurate preoperative planning of hip joint replacements.
authors.affiliation: Department of Orthopedic Surgery, University Medical Center Groningen, Hanzeplein 1, 9700 RB, Groningen, The Netherlands. b.the@orth.umcg.nl
authors.forename: B
authors.initials: B
authors.lastname: The
authors.forename: R L
authors.initials: RL
authors.lastname: Diercks
authors.forename: R E
authors.initials: RE
authors.lastname: Stewart
authors.forename: P M A
authors.initials: PM
authors.lastname: van Ooijen
authors.forename: J R
authors.initials: JR
authors.lastname: van Horn
mesh_terms: D000465:Algorithms; D019644:Arthroplasty, Replacement, Hip / Q000379:methods*; D002138:Calibration; D006621:Hip Joint / Q000000981:diagnostic imaging* / Q000601:surgery*; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D010388:Pelvis / Q000000981:diagnostic imaging; D010818:Practice Patterns, Physicians'; D011300:Preoperative Care / Q000379:methods*; D017755:Prosthesis Fitting / Q000379:methods; D011856:Radiographic Image Enhancement / Q000379:methods* / Q000592:standards; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D025321:Surgery, Computer-Assisted / Q000379:methods