EFFECTS OF REAR-WHEEL CAMBER ON WHEELCHAIR STABILITY

Objectives: To evaluate how using a wheelchair with rear-wheel camber (when the bottoms of the wheels are farther apart than the tops) is as sociated with the risk of instability incidents, and to determine the effect of camber on wheelchair stability. Design, Setting, Patients: E pidemiologic data were analyzed from a sample of 576 users of manually propelled wheelchairs in Nova Scotia. A controlled trial was performe d using a representative wheelchair occupied by an anthropomorphic les t dummy, altering the camber in 5 degrees increments from -15 degrees to +15 degrees. Main Outcome Measures: For the epidemiologic study, un ivariate and multivariate analyses were used. To measure the static st ability, a tilting platform was used according to the guidelines of th e International Organization for Standardization. Results: Camber user s reported significantly more instability incidents; of these incident s, more were in the rear direction (40% vs 27%) and fewer in the later al direction (17% vs 28%) (p < .01). When controlling for other factor s, camber was associated with a 3.91-fold increased risk of sustaining an instability incident (p < .001). With increases in camber angle in the laboratory, lateral and forward stability increased and rear stab ility decreased (with the wheels unlocked and locked) (p < .001). Conc lusion: Camber use is negatively associated with instability incidents in the lateral direction and positively associated with incidents in the backward direction, probably due in part to the effects of camber on lateral and rear stability. (C) 1997 by the American Congress of Re habilitation Medicine and the American Academy of Physical Medicine an d Rehabilitation