Tracking high speed arthrokinematics using a new and high resolution Biplane Dynamic Roentgen Stereogrammetric method

Conventional motion measurement techniques are unable to measure knee arthrokinematics during dynamic knee motion to clinically significant levels of accuracy. Assessment with Biplane Dynamic Roentgen Stereogrammetric Analysis (DRSA) overcomes the problem but previous attempts report challenges with motion blur, dynamic accuracy, image quality, excessive radiation exposure, motion tracking artifacts and computational load. The quality of measurement is also affected by image occlusion from body segments appearing synchronously in the imaging volume due to small field of view. These disadvantages translate into reduced accuracy and excessive labor to export the kinematics. A new highly accurate three-dimensional marker-based tracking (MBT) method to estimate in-vivo arthrokinematics of high-speed sequences of biplane radiographs from a new DRSA system is presented here. Data acquired with imaging phantoms and patients (with embedded tantalum bone markers) moving at very-high speeds were analyzed for static and dynamic errors. Combination of the new DRSA instrumentation and the MBT method increases accuracy (Average dynamic error: ±0.1 mm) without loss of information and reduces significantly patient radiation exposure and the time to export joint kinematics. The method is effective with high-speed motion data acquired at much lower (reduced by 70%) radiation exposure without information loss from blurring effects due to motion. Dynamic errors were greatly reduced with increasing image resolution and acquisition rate. The interplay between accuracy, brightness, contrast, exposure and resolution for the bone markers is demonstrated for high-speed movement. The method is one order of magnitude more accurate than conventional motion analysis techniques in tracking high-speed arthrokinematics.