3D shoulder position measurements using a six-degree-of-freedom electromagnetic tracking device.

OBJECTIVE: To describe a recording and processing methodology for obtaining kinematic data of the shoulder which meets three more criteria besides usual requirements regarding precision and accuracy: sufficient speed, obtaining complete 3D kinematics including joint rotations, and usage of coordinate systems based on reference points. DESIGN: Static recordings of shoulder bone orientations during standardized humerus elevations based on the palpation technique using a six-degree-of-freedom electromagnetic tracking device. BACKGROUND: An easy, fast, well standardized measurement methodology for obtaining complete 3D shoulder kinematic data is urgently needed for fundamental musculoskeletal and clinical research. METHODS: A measurement methodology was designed and developed. Shoulder kinematics were obtained from repeated measurements on 15 healthy subjects performed by two observers. Inter-trial, inter-day, inter-observer and inter-subject variability were established. Results were compared to literature. RESULTS: Complete kinematic descriptions were obtained. A measurement speed of about one position per second could be reached. The measured kinematics and accuracy of the measurements were found to be in concordance with the literature. CONCLUSION: All previously formulated criteria for a clinical useful method for obtaining shoulder kinematics have been met.

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