Accurate measurements of in-vivo hip kinematics may elucidate the mechanisms responsible for impaired function and chondrolabral damage in hips with femoroacetabular impingement (FAI). The objectives of this study were to quantify the accuracy and demonstrate the feasibility of using dual fluoroscopy to measure in-vivo hip kinematics during clinical exams used in the assessment of FAI. Steel beads were implanted into the pelvis and femur of two cadavers. Specimens were imaged under dual fluoroscopy during the impingement exam, FABER test, and rotational profile. Bead locations measured with model-based tracking were compared with those measured using dynamic radiostereometric analysis. Error was quantified by bias and precision, defined as the average and standard deviation of the differences between tracking methods, respectively. A normal male volunteer was also imaged during clinical exams. Bias and precision along a single axis did not exceed 0.17 and 0.21 mm, respectively. Comparing kinematics, positional error was less than 0.48 mm and rotational error was less than 0.58°. For the volunteer, kinematics were reported as joint angles and bone-bone distance. These results demonstrate that dual fluoroscopy and model-based tracking can accurately measure hip kinematics in living subjects during clinical exams of the hip.
Ashley L. Kapron is with the Department of Orthopaedics and the Department of Bioengineering, University of Utah, Salt Lake City, UT. Stephen K. Aoki and Christopher L. Peters are each with Department of Orthopaedics, University of Utah, Salt Lake City, UT. Steve A. Maas is with the Department of Bioengineering and with the Scientific Computing and Imaging Institute, University of Utah, Salt Lake City, UT. Michael J. Bey and Roger Zauel are each with Bone and Joint Center, Department of Orthopaedics, Henry Ford Hospital, Detroit, MI. Andrew E. Anderson is with the Departments of Orthopaedics, Bioengineering, and Physical Therapy and with the Scientific Computing and Imaging Institute, all at the University of Utah, Salt Lake City, UT. Address author correspondence to Andrew E. Anderson at firstname.lastname@example.org.