Inertial measurement units for the detection of the effects of simulated leg length inequalities

Can external work during walking in scoliosis patients be estimated from spatiotemporal parameters?

BACKGROUND

Patients with scoliosis present gait impairments compared to healthy subjects. Clinically, spine deformity is evaluated with Cobb angle, a standard measurement to determine and track the progression of scoliosis. Scoliosis is a biomechanical trouble, dependant of external forces and muscular activity. External work is currently analyzed in patients with scoliosis because this work sums up consequences and evolutions of spine deformity. Habitually, biomechanics approach is used to compute this work. For asymptomatic subjects, a regression model let to compute external work. So, considering the area of research to facilitate the follow-up at lower cost, this regression function could be applied to patients with scoliosis but need to be validated.

RESEARCH QUESTION

can external work during walking in scoliosis patients be estimated from spatiotemporal parameters with a regression model?

METHOD

This retrospective study included twenty untreated patients with idiopathic scoliosis and sixteen asymptomatic participants. We used a regression model defined in case of asymptomatic subjects in literature and proposed a new specific model in case of patients with scoliosis.

FINDINGS

The external work in patients with scoliosis calculated with the Wirta's regression eq. (0.23 ± 0.04 J.kg-1.m-1) was underestimated compared to the external work calculated using a biomechanical method (0.33 ± 0.06 J.kg-1.m-1). A new regression model including Cobb angle and spatio-temporal parameter presents a high coefficient of determination.

INTERPRETATION

In opposition to biomechanical method, our new model let to compute external work without expensive gait laboratory. This specific model is more reliable than the model developed from asymptomatic subjects.

An Ergonomic Assessment of Different Postures and Children Risk during Evacuations

Crawling is recommended for avoiding high heat and toxic fumes and for obtaining more breathable air during evacuations. Few studies have evaluated the effects of crawling on physical joints and velocity, especially in children. Based on motion capture technology, this study proposes a novel method of using wearable sensors to collect exposure (e.g., mean duration, frequency) on children’s joints to objectively quantify the impacts of different locomotion methods on physical characteristics. An on-site experiment was conducted in a kindergarten with 28 children (13 boys and 15 girls) of different ages (4–6 years old) who traveled up to 22 m in three different postures: upright walking (UW), stoop walking (SW), and knee and hand crawling (KHC). The results showed that: (1) The level of joint fatigue for KHC was heavier than bipedal walking (p < 0.05), which was evidenced by higher mean duration and frequency. There was no significant difference between UW and SW (p > 0.05). (2) The physical characteristics of the children in the different postures observed in this study were different (p < 0.05). The ankle was more fatigued than other joints during bipedal walking. Unlike infants, the wrists and hips of the children became fatigued while crawling. The key actions flexion/extension are more likely to induce joint fatigue vs. other actions. (3) Crawling velocity was significantly slower than the bipedal velocities, and UW was 10.6% faster than SW (p < 0.05). The bipedal walking velocity started to decrease after the children had travelled up to 13 m, while the KHC velocity started to decrease after traveling up to 11.6 m. (4) In a severe fire, the adoption of SW is suggested, as the evacuees can both evacuate quickly and avoid overworking their joints. (5) There were no significant differences in the age (p > 0.05) and gender (p > 0.05) of the children on the joints in any of the three postures. To conclude, KHC causes more damage to body joints compared to bipedal walking, as evidenced by higher exposure (mean duration, frequency), whereas UW and SW are similar in terms of the level of joint fatigue. The above findings are expected to provide a useful reference for future applications in the children’s risk assessment and in the prevention design of buildings.