Introduction: Functional outcome measurements (FOMs) have been shown to be effective tools in diagnosing, planning treatments, and tracking outcomes in several subspecialties of medicine. FOMs often produce large volumes of complex data that require sophisticated collection, storage, and analytic techniques to generate functional measures of domains such as gait performance, postural stability, neuromuscular activity, and movement strategies. These complexities pose particular challenges for the application of FOMs in the clinical setting where the primary focus is on patient care. Unfortunately, there are capital and support costs associated with running and maintaining FOMs labs which pose additional hurdles that may inhibit otherwise interested surgeons. As interest in and use of clinically-derived functional evaluations of spine patients grow, so will the need for simple, objective measures that summarize complex data sets to create clinically-meaningful and actionable information. Therefore, the purpose of this study was to develop and validate low-cost FOMs generated from a wearable sensor that quantifies common movement in a home-based environment.

Methods: Twelves Lumbar Degenerative surgical candidates (LD; Age: 59.6, Height: 1.68 m, Weight: 71.5 kg) and 12 healthy controls (C; Age: 46.1, Height: 1.74 m, Weight: 80.1 kg) participated in this study. Controls wear a small sensor (30 x 44 x 8mm, weight: 12 grams) with a patch on T1 in addition to traditional Gait Lab sensors. Validation of the proposed sensor and common FOMs outcomes out of a gait lab were compared. Furthermore, subjects wore the wearable sensor for additional 24 hours. The sensor detected different types of activities during the day (I.e. standing, walking, sitting, etc.) and also capture the patient’s level of activity in the home-based environment (Figure 1). 

Results: In comparison to a gold standard human motion capture, the wearable sensor was able to reliably measure all trunk kinematic during standing, walking, and transition from sitting (p>0.05). Based on the sensor detection and algorithm, patients with degenerative lumbar spinal pathologies presented with a lower level of activity (Walking:4.7%, Standing: 11.6%, Sitting: 25.3%) in comparison to controls (Walking:7.9%, Standing: 21.7%, Sitting: 17.1%; Figure 1). Balance effort and the Cone of Economy dimensions were found to be significantly larger in LD patients (sagittal: 7.9°, coronal: 7.2°) compared to controls (sagittal: 5.8°, coronal: 3.2°; p<0.035; Figure 2).

Discussion: The underlying purpose of this study was to validate and prove the feasibility of home-based functional outcome measurements, which can provide relevant details in a digestible format that conveys the functional status of the patient and raises flags for areas of concern. Such insights may lead to changes in assessments of disability, treatment strategies, or modifications of rehabilitation regimens. Several benefits are anticipated from a wearable quantitative tool to assist with preoperative planning for patient-specific alignment objectives, which may assist in choosing the right surgical procedure for the right patient, recognition of red flags, leading to avoidance of surgery where it is not going to help, and also recovery monitoring, early detection of perioperative complications, prognostic information, and treatment data.