23 research outputs found
Accuracy of biplane x-ray imaging combined with model-based tracking for measuring in-vivo patellofemoral joint motion
<p>Abstract</p> <p>Background</p> <p>Accurately measuring <it>in-vivo</it> motion of the knee's patellofemoral (PF) joint is challenging. Conventional measurement techniques have largely been unable to accurately measure three-dimensional, <it>in-vivo</it> motion of the patella during dynamic activities. The purpose of this study was to assess the accuracy of a new model-based technique for measuring PF joint motion.</p> <p>Methods</p> <p>To assess the accuracy of this technique, we implanted tantalum beads into the femur and patella of three cadaveric knee specimens and then recorded dynamic biplane radiographic images while manually flexing and extending the specimen. The position of the femur and patella were measured from the biplane images using both the model-based tracking system and a validated dynamic radiostereometric analysis (RSA) technique. Model-based tracking was compared to dynamic RSA by computing measures of bias, precision, and overall dynamic accuracy of four clinically-relevant kinematic parameters (patellar shift, flexion, tilt, and rotation).</p> <p>Results</p> <p>The model-based tracking technique results were in excellent agreement with the RSA technique. Overall dynamic accuracy indicated errors of less than 0.395 mm for patellar shift, 0.875° for flexion, 0.863° for tilt, and 0.877° for rotation.</p> <p>Conclusion</p> <p>This model-based tracking technique is a non-invasive method for accurately measuring dynamic PF joint motion under <it>in-vivo</it> conditions. The technique is sufficiently accurate in measuring clinically relevant changes in PF joint motion following conservative or surgical treatment.</p
Bilateral internuclear ophthalmoplegia and clivus fracture following head injury: case report
Perfusion significantly increases mineralized matrix production at the interior of 3-D PCL composite scaffolds
Proceedings of the 2005 Summer Bioengineering Conference2005333-33
Measuring dynamic in-vivo glenohumeral joint kinematics: Technique and preliminary results
Evaluation of the performance of a motion capture system for small displacement recording and a discussion for its application potential in bone deformation in vivo
The aim of this study is to evaluate the performance of a motion capture system and discuss the application potential of
the proposed system in in vivo bone-segment deformation measurements. In this study, the effects of the calibration procedure,
camera distance and marker size on the accuracy and precision of the motion capture system have been investigated
by comparing the captured movement of the markers with reference movement. The results indicated that the
system resolution is at least 20mm in a capture volume of 40033003300mm3, which mostly covers the range of
motion of the tibia during the stance phase of one gait cycle. Within this volume, the system accuracy and precision
decreased following the increase of camera distance along the optical axis of the cameras. With the best configuration,
the absolute error and precision for the range of 20mm displacement were 1.2–1.8mm and 1.5–2.5mm, respectively.
Small markers (Ø3–8 mm) yielded better accuracy and repeatability than the larger marker (Ø10.5mm). We conclude
that the proposed system is capable of recording minor displacements in a relative large volume