Wheelchair related injuries treated in US emergency departments

OBJECTIVE

To characterize the trend of wheelchair related injuries over time, and describe the demographics and characteristics of wheelchair users' injuries by age group.

METHODS

Data from the National Electronic Injury Surveillance System (NEISS) were analyzed.

RESULTS

In 2003, more than 100,000 wheelchair related injuries were treated in emergency departments in the US, double the number reported in 1991. Tips and falls accounted for 65-80% of injuries across all age groups of wheelchair users. The majority of children's injuries occurred at locations outside of homes and institutions/hospitals in environments with stairs, ramps, and curbs (57.3%). In contrast, injuries among adult users were more likely to occur in homes, hospitals, and institutions (45-90%).

CONCLUSIONS

Wheelchair related injuries may have increased in the US during the past decade. Prevention efforts should address the interacting complex factors that influence risk of injury while using a wheelchair.

Spine loading as a function of lift frequency, exposure duration, and work experience

BACKGROUND

Physiological and psychophysical studies of the effects of lifting frequency have focused on whole-body measurements of fatigue or subjective acceptance of the task and have not considered how spine loads may change as a function of lift frequency or lift time exposure. Our understanding of biomechanical spine loading has been extrapolated from short lifting bouts to the entire work day and may have led us to incorrect assumptions. The objective of this project was to document how spine loading changes as a function of experience, lift frequency, and lift duration while repetitively lifting over the course of an 8-h workday.

METHODS

Twelve novice and twelve experienced manual materials handlers performed repetitive, asymmetric lifts at different load and lift frequency levels throughout an 8-h exposure period. Compression, anterior-posterior shear, and lateral shear were evaluated over the lifting period using an EMG-assisted biomechanical model.

RESULTS

Spinal loads increased after the first 2 h of lifting exposure regardless of the lift frequency. Loading was also greater for the inexperienced subjects compared to experienced lifters. The greatest spine loads occurred at those lift frequencies and weights to which the workers were unaccustomed.

INTERPRETATION

Increases in spine loading were tracked back to the changes in muscle recruitment patterns that typically involved increased muscle coactivation. The results emphasize the importance of previous motor programming in defining spine loads during repetitive lifting. These results indicate a very different influence of frequency and lift time exposure compared to physiologic and psychophysical assessments. This study has shown that it is not sufficient to extrapolate from short lift periods to extended exposure periods if the biomechanical loading implications of the task are of interest.