Continuous Activity Tracking Using a Wrist-Mounted Device in Adult Spinal Deformity: A Proof of Concept Study

Sagittal imbalance in adult spinal deformity (ASD) likely influences balance and ambulatory capacity because of muscular demand, pain, and disability. Disability measures for ASD rely heavily on ambulatory function; however, current metrics may fail to fully capture its contribution. We sought 1) to determine the utility of continuous remote step count monitoring and activity tracking in ASD using a consumer-friendly accelerometer, and 2) to investigate trends and patterns both before and after surgical intervention.

One patient with progressive ASD was enrolled. Daily step count (SC), distance traveled (DT), and levels of activity were measured using a wrist-mounted device for 17 months. Spinopelvic parameters were measured from standing radiographs. The patient underwent T4-ilium long-segment fusion for correction of progressive deformity (coronal cobb angle: 8°; sagittal vertical axis: 4 cm; coronal vertical axis: 2 cm); recovery was uneventful. The device was worn for 216 of 520 (41%) recorded days during waking hours, with an average SC of 5254 ± 2696 per day. SC (P < 0.001), DT (P < 0.001), and minutes of light activity (LA) (P < 0.001) declined over the 9-month preoperative course, whereas sedentary activity increased (P < 0.001). After surgery, SC, DT, and LA decreased in the early postoperative period, with a significant increase at 7-8 months compared with the preoperative period (P < 0.001).

Wrist-mounted devices are a noninvasive and effective measure to track daily activity and ambulatory capacity of patients with spinal deformity. In a single case, progressive deformity correlated with worsening activity levels, whereas deformity correction improved SC and activity level. These results support remote activity monitoring as an exploratory outcome for future studies.