Figure 19: The Ischial Tuberosities
Figure 21: 60° Pelvic Positioning Belt
Note . From Gray’s Anatomy: Male Pelvis, by Henry Gray, 1918, retrieved from http://commons.wikimedia.org/wiki/Human_pelvis#/ media/File:Gray241.png. Posterior pelvic tilt may be caused by low tone in the trunk, tight hamstrings, decreased hip flexion range, an overlong seat depth, or the client simply sliding forward or actively extending on the seat. For some users, such as those with spinal cord injury, a posterior pelvic tilt provides improved stability for upright trunk control and assists with reducing the protrusion of the ITs into the seat cushion, which reduces the risk for pressure injuries. However, pressure risk to the sacrum is increased. Providing adequate posterior support to the pelvis to prevent further rearward movement is one option for correction. A biangular back (Figure 20a) is sometimes used to keep the pelvis in an upright, neutral, or – if necessary, to accommodate range limitation – in a posterior tilt while allowing the trunk to extend posterior to the pelvis. Figure 20: Biangular Back and Antithrust Cushion
Note . From “Pelvic Support User’s Guide,” by Bodypoint.com, 2011, retrieved from http://bodypoint.com/data/default/assets/public/ BMM044%20Pelvic%20Support%20Users%20Guide_low.pdf . © Bodypoint. Reprinted with permission. The goals of correcting a posterior pelvic tilt include promoting neutral alignment of the pelvis to support the anatomical curvatures of the spine for upright trunk and head control, promoting immersion of the ITs in the cushion materials to reduce pressure injury risk, providing optimal alignment for biomechanical function, and increasing proximal stability for function. Anterior pelvic tilt An anterior pelvic tilt is when the top of the pelvis moves forward. When an anterior pelvic tilt is present, the spine is a more lordotic (hyperextended lumbar area; Minkel, 2018). An anterior pelvic tilt may be caused by postural collapse secondary to muscle paralysis, weakness, or low tone. Clients with the diagnosis of Duchenne muscular dystrophy may have overactive lumbar extension. Clients with a diagnosis of cerebral palsy may demonstrate an anterior tilt resulting from increased extensor tone in the lumbar area. Spinal fusion to the level of the sacrum may also cause an anterior pelvic tilt that cannot be corrected. Activity idea: Sit on your hands and feel for two bony prominences called the ITs (Figure 19). Move your pelvis into an anterior pelvic tilt. The ITs move rearward off of your hands. For correction of this position, the pelvic positioning belt may be placed directly over the anterior superior iliac spine (ASIS) to pull the pelvis back into a neutral position (Figure 22). This is typically achieved by mounting the belt at 30°, using a 4-point pelvic positioning belt. The primary belt position (in this case, 30°) is maintained by a secondary belt (in this case, mounted at between 60° and 90°). This secondary belt prevents the primary belt from moving above the ASISs onto soft tissue. Another option is to use an abdominal panel (sometimes called a belly binder or corset ; Figure 23). This panel should contact the top of the pelvis and lower ribs to prevent undue pressure to soft tissue. The panel reduces lordosis and, as a result, anterior pelvic tilt. The goals of addressing an anterior pelvic tilt are to reduce the accompanying lordosis and achieve neutral alignment of the pelvis for weight-bearing on the ITs, biomechanical function, and proximal stability for function.
Note. From “Pelvic Support User’s Guide,” by Bodypoint.com, 2011, retrieved from http://bodypoint.com/data/default/assets/public/ BMM044%20Pelvic%20Support%20Users%20Guide_low.pdf . © Bodypoint. Reprinted with permission. This shape is often found in off-the-shelf backs. If the hamstrings are tight, the pull on this muscle can be alleviated by either opening the seat-to-back angle or decreasing the thigh-to-calf angle (Sutherland, 2018). If hip flexion is limited, flexing the hip will push the pelvis into a posterior tilt. The seat-to- back angle must not exceed the available hip flexion range. For clients who slide and extend, two solutions are often used in tandem. An antithrust cushion uses a curb (Figure 20b) just in front of the ITs to prevent forward migration. This antithrust contour is often found in off-the- shelf cushions. A pelvic positioning belt can also prevent this movement if placed at a 60° angle to the client (Figure 21). A more typical angle of 45° allows the pelvis to rotate under the belt.
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Book Code: PTNC1023
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