Accuracy of scapular motion by double calibration

摘要

Scapular kinematics is difficult to measure using skin-marker-based methods due to the sliding of the scapula under the skin and muscles. Among the recent publications, an acromion marker method coupled to a single calibration (SC) of the scapula (calibrated anatomical system technic-method) seems to be the best simple method to estimate real scapular motion (Meskers et al. 2007; van Andel et al. 2009; Brochard et al. 2011). However, above 90° of humeral elevation, movement of the muscles and the skin on the acromion creates an artefact yielding inaccurate results. To improve accuracy and allow exploration of large ranges of arm motion, we developed an algorithm based on a double calibration (DC) technique carried out at both extremes of the movement studied. This technique consists in coupling a rest calibration of the scapula (in the reference of the acromion marker set) and a high-angle calibration. We evaluated the accuracy of SC and DC comparing these methods to a scapula palpation procedure.