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INTRODUCTION: Lower-limb prosthesis users (LLPUs) experience increased fall risk due to gait and balance impairments. Clinical outcome measures are useful for measuring balance impairment and fall risk screening but suffer from limited resolution and ceiling effects. Recent advances in wearable sensors that can measure different components of gait stability may address these limitations. This study assessed feasibility and construct validity of a wearable sensor system (APDM Mobility Lab) to measure postural control and gait stability. MATERIALS AND METHODS: Lower-limb prosthesis users (n=22) and able-bodied controls (n=24) completed an Instrumented Stand-and-Walk Test (ISAW) while wearing the wearable sensors. Known-groups analysis (prosthesis versus controls) and convergence analysis (Prosthetic Limb Users Survey of Mobility [PLUS-M] and Activity-specific Balance Confidence [ABC] Scale) were performed on 20 stability-related measures. RESULTS: The system was applied without complications; however missing anticipatory postural adjustment data points for nine subjects affected the analysis. Of the 20 analyzed measures output by the sensors, only three significantly differed (p≤.05) between cohorts, and two demonstrated statistically significant correlations with the self-report measures. CONCLUSIONS: The results of this study suggest the clinical feasibility but only partial construct validity of the wearable sensor system in conjunction with the ISAW test to measure LLPU stability and balance. The sample consisted of high-functioning LLPUs, so further research should evaluate a more representative sample with additional outcome measures and tasks.
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Sclerostin antibody has demonstrated a bone-forming effect in pre-clinical models of osteogenesis imperfecta, where mutations in collagen or collagen-associated proteins often result in high bone fragility in pediatric patients. Cessation studies in osteoporotic patients have demonstrated that sclerostin antibody, like intermittent PTH treatment, requires sequential anti-resorptive therapy to preserve the anabolic effects in adult populations. However, the persistence of anabolic gains from either drug has not been explored clinically in OI, or in any animal model. To determine whether cessation of sclerostin antibody therapy in a growing OI skeleton requires sequential anti-resorptive treatment to preserve anabolic gains in bone mass, we treated 3week old Brtl/+ and wild type mice for 5weeks with SclAb, and then withdrew treatment for an additional 6weeks. Trabecular bone loss was evident following cessation, but was preserved in a dose-dependent manner with single administration of pamidronate at the time of cessation. In vivo longitudinal near-infrared optical imaging of cathepsin K activation in the proximal tibia suggests an anti-resorptive effect of both SclAb and pamidronate which is reversed after three weeks of cessation. Cortical bone was considerably less susceptible to cessation effects, and showed no structural or functional deficits in the absence of pamidronate during this cessation period. In conclusion, while SclAb induces a considerable anabolic gain in the rapidly growing Brtl/+ murine model of OI, a single sequential dose of antiresorptive drug is required to maintain bone mass at trabecular sites for 6weeks following cessation.
