Multi-Day Recordings of Wearable Sensors Are Valid and Sensitive Measures of Function and Independence in Human Spinal Cord Injury

Abstract

Wearable sensor assessment tools have proven to be reliable in measuring function in normal and impaired movement disorders during well-defined assessment protocols. While such assessments can provide valid and sensitive measures of upper limb activity in spinal cord injury (SCI), no assessment tool has yet been introduced into unsupervised daily recordings to complement clinical assessments during rehabilitation. The objective of this study was to measure the overall amount of upper-limb activity in subjects with acute SCI using wearable sensors and relate this to lesion characteristics, independence, and function. The overall amount of upper extremity activity counts, measures of wheeling (speed and distance), and limb-use laterality were measured in 30 in-patients with an acute cervical or thoracic SCI three months after injury. The findings were related to the international standards for neurological classification of SCI, the spinal cord independence measure, and the upper extremity motor scores of the Graded and Redefined Assessment of Strength, Sensibility, and Prehension. Overall upper extremity activity counts were successfully recorded in all patients and correlated with the neurological level of injury and independence. Clinical measures of proximal muscle strength were related to overall activity count and peak velocity of wheeling. Compared with paraplegics, tetraplegics showed significantly lower activity counts and increased limb-use laterality. This is the first cross-sectional study showing the feasibility and clinical value of sensor recordings during unsupervised daily activities in rehabilitation. The strong relationship between sensor-based measures and clinical outcomes supports the application of such technology to assess and track changes in function during rehabilitation and in clinical trials.

Monitoring Upper Limb Recovery after Cervical Spinal Cord Injury: Insights beyond Assessment Scores

“…We arbitrarily chose a Z -score of 2 as 95.4% of the values fall within 2 SDs from the mean of paraplegic subjects. This is because we have previously shown that paraplegic subjects do not show any limb-use laterality (22) and their limb-use laterality indexes are similar to healthy subjects (43). In analyzing only the lateralized-group, we showed that lateralized cervical subjects significantly decreased limb-use laterality but remained impaired with limb-use laterality values in the same range as a group of chronic tetraplegic subjects who we measured previously (31).…”

“…Previously, we have shown that proximal muscle function was strongly related to overall AC during acute inpatient rehabilitation (22). In the present study, we extend these findings and show that this relationship becomes weaker over time.…”

“…The scores range from 0 to 50 per arm, and the scores of both arms were summed together. In a previous study, we showed that proximal motor scores of the GRASSP are strongly related to overall UL activity in acute inpatients (22); therefore, distal muscle scores were omitted from the analysis, resulting in a proximal score range from 0 to 20 per arm. Strength tests with a hand-held dynamometer (HHD) of four key groups of UL muscles were performed: elbow flexors (biceps brachii, brachialis, and brachioradialis), elbow extensors (triceps brachii), shoulder flexors (deltoid anterior part, pectoralis major upper and middle part), and extensors (latissimus dorsi and teres major) (26).…”

“…In order to track changes in UL activity, we used sensor-based metrics [overall activity counts (ACs), distance wheeled, peak wheeling velocity, and limb-use laterality index] that allow a comprehensive evaluation of UL recovery as they have been shown to be closely related to UL motor function and independence in an acute cross-sectional study (22). …”

“…However, as these studies focused exclusively on measuring physical activity rather than assessing functional recovery, they were not performed within standardized time frames and the activity outcomes were not compared with standardized clinical outcomes (19–21). For this reason, in a previous study, we showed the feasibility and validity of sensor-based outcome metrics in measuring UL function and independence during cross-sectional recordings (22). Given the validity and sensitivity of these measures, the purpose of this study was to assess the quantity of upper limb (UL) activity and its changes during acute rehabilitation in a cohort of tetraplegic and paraplegic patients in standardized SCI-specific time frames.…”