Inferring 3D Kinematics of Carpal Bones from Single View Fluoroscopic Sequences Xin Chen 1 , Jim Graham 1 , Charles Hutchinson 2 , and Lindsay Muir 3 1 ISBE, School of Cancer and Enabling Sciences, University of Manchester, Oxford Road, Manchester, M13 9PT, UK {xin.chen,jim.graham}@manchester.ac.uk 2 Clinical Sciences Research Institute, Clinical Sciences Building, University Hospital -Walsgrave Campus, Clifford Bridge Road, Coventry, CV2 2DX, UK 3 Consultant Orthopaedic Surgeon, Salford Royal Hospital NHS Foundation Trust, Stott Lane, Salford, M6 8HD, UK Abstract. We present a novel framework for inferring 3D carpal bone kinematics and bone shapes from a single view fluoroscopic sequence. A hybrid statistical model representing both the kinematics and shape variation of the carpal bones is built, based on a number of 3D CT data sets obtained from different subjects at different poses. Given a fluoroscopic sequence, the wrist pose, carpal bone kinematics and bone shapes are estimated iteratively by matching the statistical model with the 2D images. A specially designed cost function enables smoothed parameter estimation across frames. We have evaluated the proposed method on both simulated data and real fluoroscopic sequences. It was found that the relative positions between carpal bones can be accurately estimated, which is potentially useful for detection of conditions such as scapholunate dissociation. Keywords: Carpal bones kinematics, 2D 3D registration, Statistical model. 1 Introduction Chronic pain in the wrist arises due to a number of conditions, such as instability patterns, nonunion or malunion of fractures, primary osteoarthritis and inflammatory arthritis. The result for patients is a severe reduction in quality of life due to impairment of everyday functions, lost work time, increased morbidity and loss of the capacity to live independently. The current method of distinguishing between these conditions is by examining 2D video fluoroscopy sequences showing movement of the hand from full ulnar to full radial deviation and from full flexion to extension in two orthogonal views. From these images clinicians can infer the three-dimensional translations and rotations of the carpal bones that take place during wrist movement, and arrive at a differential diagnosis on the basis of variations from normal bone kinematics. The interpretation is difficult and the accuracy of diagnosis depends wholly on the experience of the practi- tioner. Currently, accurate diagnosis requires referral to a specialist hand consultant and treatment is often delayed to the detriment of the patient. The aim of the project is computer interpretation of the fluoroscopy sequences to attain a higher degree of objectivity and quantification in the diagnostic process. During G. Fichtinger, A. Martel, and T. Peters (Eds.): MICCAI 2011, Part II, LNCS 6892, pp. 680–687. c  Springer-Verlag Berlin Heidelberg 2011