Can Recovery Foot Placement Affect Older Adults’ Slip-Fall Severity?

Abstract

Following a slip occurred in the overground walking, a fall can be classified into two exclusive categories: feet-forward fall or split fall. The purposes of this study were to investigate whether the placement of the recovery foot would determine the slip types, the likelihood of fall, and the severity of fall. The fall severity was estimated based on the impact velocity of body segments or trunk orientation upon fall arrest. One hundred ninety-five participants experienced a novel, unannounced slip while walking on a 7-meter walkway. Kinematics of a full-body marker set was collected by a motion capture system which was synchronized with the force plates and loadcell. The results showed that the recovery foot landing position relative to the projected center of mass position at the recovery foot touchdown determined the slip type by 90.8%. Feet-forward slips led to significantly lower rate of falls than did split slips (47.6% vs. 67.8%, p < 0.01). Yet, feet-forward falls were much more dangerous because they were associated with significantly greater estimated maximum hip impact velocity (p < 0.001) and trunk backward leaning angle (p < 0.001) in comparison to split falls.

Severity of Unconstrained Simultaneous Bilateral Slips: The Impact of Frontal Plane Feet Velocities Relative to the Center of Mass to Classify Slip-Related Falls and Recoveries

“…Frontal plane lower body models revealed two biomechanical behaviors that were associated with falls: (1) frontal plane sliding feet, where both feet travel in the same direction (ipsilaterally/contralaterally) and opposite to the CoM, and (2) frontal plane split feet, where both feet travel faster than the CoM and opposite to each other. Sagittal plane lower body models, on the other hand, revealed two biomechanical behaviors that are similar to those described in past literature ( 17 , 19 , 21 ): (1) sagittal plane split feet, where the leading foot travels faster than the CoM and opposite to the trailing foot, which travels opposite to both, and (2) sagittal plane forward sliding mechanism, where both feet travel with a velocity similar to that of the CoM. However, we believe that foot motion relative to the CoM is not the only contributor to falls and recoveries, and that upper body biomechanics play a crucial role in redistributing sagittal and frontal plane angular momentum from the trunk to the arms.…”

“…Hence, we presented our second hypothesis and demonstrated that the peak sagittal and frontal plane angular momentum of the trunk and non-dominant arm during the slipping timeline, respectively, were significant in classifying falls and recoveries. Despite extensive literature on the significance of peak trunk extension angle to both falls and recoveries (9,13,17,19,23,29,(42)(43)(44)(45), our variable selection process generated a model based on arm adduction angular momentum. This would indicate that bracing for impact by increasing arm adduction angular momentum is associated with higher fall probability.…”

“…Troy et al ( 21 ) showed an increased probability of recovery when lateral foot velocity and displacement are closer to that of the CoM. Wang et al ( 17 ) also showed that foot placement relative to the CoM affects the probability of a fall . Therefore, we incorporated lower body biomechanics in the form of feet velocities relative to the CoM into our models since keeping the base of support under the CoM is likely vital to avoid a fall, especially when individuals transition from a walking to a sliding technique.…”

“…However, some common methods for simulating slips in the lab do not generate unconstrained slips. Treadmill-belt perturbations (13)(14)(15)(16) or sliding platforms embedded in the floor (9,15,(17)(18)(19) during over-ground locomotion restrict motion of the slipping foot to the anteroposterior direction and therefore may not reproduce the diversity of slip mechanics across both sagittal and frontal planes. Other slip simulation methods employing low friction sheets or lubricants applied unexpectedly in a person's walking path (9,10,(20)(21)(22) do produce unconstrained slips, however the location of the slip is predictable after the first occurrence, making the delivery of repeated unpredictable slips challenging.…”

Limb Collapse or Instability? Assessment on Cause of Falls

“…The purposes of this study were to address these questions by developing a causal-based assessment method, and investigate the causation of 97 falls (out of 195 communitydwelling older adults participated in this study) based on this method 24,34 . We first hypothesized that these participants were equally susceptible to the above-stated causal factors (null hypothesis).…”