Abstract
Summary
Upper extremity activity was similar in patients and healthy subjects, showing no significant asymmetry between arms within subjects. Further improvements (e.g. thresholds, filters, inclinometer function) are needed to show the clinical value of AM for patients suffering shoulder complaints.
Introduction
Activity monitoring is becoming a popular outcome tool especially in orthopaedics. The suitability of a single 3D acceleration-based activity monitor (AM) for patients with lower-extremity problems has been shown. However less is known about its feasibility to monitor upper-extremity activity. Insight into the amount and intensity of upper-extremity activity of the affected and non-affected arm (asymmetry) may be of added value for diagnostics, therapy choice and evaluating treatment effects. This study investigates the feasibility of a single AM to evaluate (asymmetry in) upper-extremity activity in daily life.
Methods
Upper-extremity activity was measured in 12 patients with subacromial impingent syndrome (59±12yr) and 10 healthy subjects (29±11yrs). Subjects wore a single 3D accelerometer at both arms, just above the base of the Hueter triangle, for one day (min. 8 hours). Specific algorithms were used to derive quantity (activity duration, rest periods) and intensity (low-high) activity parameters (% of the day). The ratio in % activity between non-affected (dominant) and affected (non-dominant) arm was calculated. Asymmetry was expressed as the %-difference in activity between arms with regards to the non-affected (dominant) arm. Also popular PROMs were completed: DASH score (range 0–100;0=best) and SST score (range 0–12; 0=best). Independent t-test, Mann-Whitney U test, Pearson's r correlations were performed.
Results
No significant differences in activity duration (Healthy: 50%, patients: 57% of the day) and intensity of upper-extremity activity were found between patients and healthy subjects, although PROMs were significantly worse in patients. Patients and healthy subjects use both arms in similar amounts of time per day. This corresponds to the ratio which almost equals 1 and the low asymmetry values (<10%) in both groups. Also the amount activity in low and high intensity was comparable between affected (non-dominant) and non-affected (dominant) arm. No correlations were found between AM data and PROMs.
Discussion and Conclusion
Patients and healthy subjects move their upper arms approximately 53% of the day. No differences in amount and intensity of upper-extremity activity were found between healthy subjects and patients, neither between both arms. This suggests that subjects perform daily activities independent of pain, complaints or arm dominance. It could also hint at the algorithm operating with a too low activity threshold to include shuffling or misclassifying excitations from walking as intense arm movement. Both issues can be adjusted by adjusting thresholds and filter settings. The asymmetry in upper-extremity activity of healthy subjects (9.1%) assumes that a 10% asymmetry in arm activity seems natural, which coincides with similar values reported for functional shoulder tests (Koerver et al. CORS 2010). The lack of correlations between AM and PROMs suggests that both measure different outcome dimensions. The AM has some limitations which should be considered when improving the clinical feasibility of upper-extremity activity monitoring. The AM only allows to measure acceleration-related activities (speed, intensity), while upper-extremity activity often involves static force-related activities. However, the inclinometer capacity of accelerometers allows to measure upper-extremity activity at different elevations (upper arm above/below shoulder). This may add qualitative information, relevant for clinical purposes.
