Ten studies (n=175) were included in the review. The sample sizes ranged from 1 to 61 participants. One study included children aged between 3 and 18 months; the remaining studies included children aged 2 to 16 years.
The studies provided conflicting evidence on the effects of seat inclination on function in children with CP.
Nine studies measured postural control. Three of the studies measuring this outcome recommended the use of posterior tilt, two of which reported improved head control. Two studies reported that back and trunk extension increased on an anterior seat base, which supported the findings of 2 studies that had reported that this helped improve the child's ability to sit up straighter. Three studies by the same group of authors reported that postural control was improved and pathological movements reduced by placing the line of gravity of the body anterior to the axis of rotation.
Three studies measured muscle activity. One study reported that lower extremity muscle activity was highest in the reclined position and lower in horizontal and anterior positions. A second study recommended a 10° anterior tilt, but also found that a 15° anterior tilt increased erector spinae muscle activity.
Five studies measured upper extremity function. Two studies by the same group of authors reported significantly improved hand and arm function for children seated in a functional sitting position with a forward-tilted pelvis. In contrast, one study recommended a semi-reclined position to improve upper extremity function. However, a later study by the same authors in normally developing children found the forward tilting position was more efficient than horizontal or backward-tilted positions. One study reported that tilting of the seat surface did not significantly impact on performance of upper extremity motor tasks.