Loads on an internal spinal fixation device during sitting

Sitting is often assumed to involve high loads on the spine as well as on i mplants for stabilising the spine. Loads on internal spinal fixation device s were therefore measured in ten patients sitting on several types of seats , including a stool, a stool with a padded wedge, a chair, a physiotherapy ball, a knee-stool, and a bench. The patients also successively sat relaxed and erect on a stool. In addition. six of them sat on a special chair allo wing different inclinations of the backrest. Implant loads were also measur ed for standing up and sitting down. There were only minor differences in f ixator loads for sitting on the different types of seats. Sitting erect cau sed an average of 11% higher implant loads than sitting relaxed. Implant lo ads decreased with increasing inclination of the upper body while sitting o n a chair with an adjustable backrest. Implant loads were about 27% higher for standing up and sitting down than for sitting. (C) 2001 Elsevier Scienc e Ltd. All rights reserved.