Tissue changes in patients following spinal cord injury and implications for wheelchair cushions and tissue loading: a literature review.

Persons using wheelchairs, especially those with spinal cord injuries (SCI), may be susceptible to tissue changes that affect their risk for pressure ulcer (PU) development. To examine the complexity of the problem of designing, selecting, and prescribing an optimal cushioning solution to help prevent PUs, a literature search was conducted examining factors that affect the biomechanical interactions of the seated buttocks with the cushion and how these factors may change over time. The majority of publications retrieved were preclinical studies and case studies, and just a small fraction was randomized clinical trials. The literature indicates that external and internal anatomy and tissue structure and function change considerably in the months and years following the loss of sensation and mobility. Specifically, these changes typically include weight and fat mass gain, skeletal muscle atrophy and fat infiltration into muscles, bone loss and bone shape adaptation at the pelvis, vascular perfusion changes, and microstructural changes in skin and muscle that are associated with disuse and affect the biomechanical behavior of these tissues. Support surfaces, particularly wheelchair cushions, should be designed to accommodate microchanges that occur for a seated person throughout the day (eg, changes in posture and position or muscle tone) as well as macrochanges in anatomy, tissue composition, and longterm tissue (patho)physiological changes. Cushions must be tailored to, and adapted for, each individual patient on a regular basis. A promising and practical bioengineering approach to fit cushions to different patient conditions is to use computer simulations (finite element [FE] modeling). As understanding about PU risk in this population increases, study designs can be refined to develop a much-needed evidence-base for the appropriate use of support surfaces in general and wheelchair cushions in particular.