Due to the reduced physical abilities of persons with SCI, they require wheelchair and seating equipment. This equipment includes wheelchair frames and specialized seating components including back supports, cushions, armrests, and footrests. The relationships between wheelchair configuration, sitting balance, and the ability to perform functional activities in persons with an SCI have been studied.
The above studies demonstrate aspects of equipment options and the impact on the SCI person’s functional abilities, specifically reaching and controlled perturbations.
In the Gabison et al. (2017) study, there was not a significant correlation between isometric trunk strength and ischial offloading. However, it reinforces the importance of assessing reaching abilities and trunk muscle activation for development of rehabilitation strategies for offloading pressure of the bilateral ischial tuberositis in those SCI individuals that lack sufficient trunk strength.
No single back support option studied by May et al. (2004) consistently facilitated performance in four functional tasks (i.e., forward wheeling, forward vertical reach, ramp ascent, and 1-stroke push). However, reaching activity differed significantly among back supports with SCI persons able to reach higher when using the Jay2 back (p=0.01) compared to the sling back (p=0.015).
Janssen-Potten et al. (2000) studied balance control and postural muscle use with four different chair configurations manipulating tilt angle of the chair and reclining angle of the backrest. No significant difference in controlled reach was found in controls or in subjects with low SCI. Sitting balance and ability to control displacement of arms and trunk during reaching improved in all chairs compared to the standard chair. Among SCI subjects with high levels of tetraplegia, sitting balance did not improve because they were unable to control body mass shift.
In a study of the effects of footrests on the sitting balance in individuals with paraplegia found that absence of a solid footrest did not decrease maximal unsupported reaching distance. Solid footrests contribute to sitting balance in persons without SCI and persons with lumbar SCI but not for persons with thoracic SCI. Persons with thoracic SCI can benefit from an elastic footrest to perform activities of daily living. Changes in muscle activity were noted when a solid footrest was replaced by an elastic footrest in persons without SCI but not in persons with SCI performing activities of daily living. Footrest conditions affect how activities of daily living are performed but not the range of activities (Janssen-Potten et al. 2002).
Kamper et al. (1999) studied the lateral postural stability of seated individuals with SCI in a dynamic environment. All SCI subjects were stable under static conditions but became unstable in a dynamic environment. Instability of SCI subjects resulted from inability to prevent rotation of the pelvis and lower torso. Rotation of the lower torso to upper torso was significantly greater in SCI subjects. The kinematics responses of able-bodied and SCI revealed that rotation of the lower torso and pelvis was greater in the SCI subjects and rotation in direction of fall preceded the rest of the body. All SCI subjects could have benefited from lateral support.
Hastings et al. (2003) investigated the postural alignment and maximal reach of individuals with C6-T10 level of SCI. The authors found that when sitting in a chair with a positive seat angle of 14° and with a low back support perpendicular to the floor, the subject’s vertical postural alignment was improved as compared to standard chairs. The alternate chair configurations also produced greater reach ability.
The upper extremity function of wheelchair users is impacted by seated posture and trunk control. Finding a balance between adequate trunk support and trunk mobility can impact functional ranges of motion and upper extremity function. Sprigle et al. (2003) revealed that upper extremity reach for wheelchair users was affected by posture but not influenced by the cushion type or backrest height. A wheelchair user’s posture is more functionally important than the supportive devices used for therapists prescribing cushions and backrest height. A posterior tilted pelvis enhances function and the position of pelvic tilt is an important predictor in measures of reach. The torso angle impacted bilateral reach, not unilateral reaching tasks. Monitoring of posture is an important factor when assessing seating and function of wheelchair users.
There is level 3 evidence (from three repeated measures studies and one case control study: May et al. 2004; Hastings et al. 2003; Sprigle et al. 2003; Janssen-Potten et al. 2002) to support the evaluation of functional performance to facilitate the decision making process for assessment and prescription of wheelchair and seating equipment options providing objective information about performance.
There is level 4 evidence (from one post-test study: Gabison et al. 2017) to suggest that reaching does not consistently provide offloading at the ischial tuberosities and not equaly between left and right.
There is level 2 evidence (from one prospective controlled trial and one case control study: Kamper et al. 1999; Janssen-Potten et al. 2000) to support that pelvic positioning especially related to pelvic tilt and the relationship between the pelvis on the trunk, affects upper extremity and reaching activities, performance of activities of daily living and postural stability.