Objective outcome evaluation using inertial sensors in subacromial impingement syndrome: a five-year follow-up study

Shoulder-related dysfunction is the second most common musculoskeletal disorder and is an increasing burden on health-care systems. Commonly used clinical questionnaires suffer from subjectivity, pain dominance and a ceiling effect. Objective functional measurement has been identified as a relevant issue in clinical rehabilitation. Inertia based motion analysis (IMA) is a new generation of objective outcome assessment tool; it can produce objective movement parameters while being fast, cheap and easy to operate. In this prospective study, an inertial sensor comprising a three-dimensional accelerometer and gyroscope is attached at the humerus to measure shoulder movements during two motion tasks in patients with subacromial impingement syndrome at baseline and at five-year after treatment. One hundred healthy subjects served as healthy reference database and 15 patients were measured pre- and post-treatment. IMA was better able to detect improvement in shoulder movements compared to the clinical questionnaires (Disability of Arm, Shoulder and Hand (DASH) and Simple Shoulder Test (SST); p < 0.05) and was hardly correlated with the clinical questionnaires (Pearson R = 0.39). It may therefore add an objective functional dimension to outcome assessment. The fast assessment (t < 5 min) of a simple motion test makes it suitable for routine clinical follow-up.