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. Relevance. Obtaining 3D descriptions of shoulder motions of patients suffering from various pathologies as the impingement syndrome, glenohumeral (sub) luxation, capsulitis adhesiva and shoulder function after arthroplasty is of vital importance in the search for etiology and pathogenesis of these disorders and for clinical evaluation.