Manual wheelchair downhill stability: an analysis of factors affecting tip probability.
Louise Thomas, Jaimie Borisoff, Carolyn J Sparrey
PMID 30400911WHAT IT FOUND
Bump height, speed, and rear axle position drove downhill wheelchair tipping in simulations.
Lowering the seat and reclining the backrest favoured rolling over or stopping, but recline increased backward tipping risk.
Key findings
01Bump height, wheelchair speed, and rear axle position were the most important factors affecting whether the modelled wheelchair rolled over, stopped, tipped forward, or tipped backward.
02Lowering the seat made the wheelchair more likely to roll over the bump or tip backward rather than tip forward; reclining the backrest also favoured rolling over or stopping over forward tipping, but greater recline could produce a backward tip.
03For modelled downhill wheeling, bumps of 1.5 cm or less were unlikely to be an issue, and reducing speed to 1 km/hr could help avoid forward tipping over higher bumps.
STILL TO COME
How it was doneWhat they foundWhat it means for PTsWhat it means for OTs
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What it does not show
No human participants were tested; the model used a wheelchair and a passive ISO dummy, so real user movement, balance, strength, and injury risk were not represented. The simulation was least reliable for backward tips in validation, with a positive predictive value of 64.3%. Wheel properties, especially caster unloading, had large sensitivity, and static wheel measurements may not match dynamic collisions. Results apply to the tested wheelchair model and slope/bump conditions, not all wheelchairs, surfaces, or users. The paper proposes training and configuration guidance from simulations, not tested clinical outcomes.
Declared interests
Funded by Natural Sciences and Engineering Research Council of Canada, Mitacs, Canada Foundation for Innovation, and Rick Hansen Foundation. The supplied text does not state author conflicts.
The easy way to misread this
Do not read the recommended seat lowering or backrest recline as proven clinical safety for your patient. The study used simulations and a dummy, and backward tipping was the least reliably predicted outcome.