The act of a wheelchair user sliding or slumping forward, often referred to as “sacral sitting,” is a common problem that poses significant health risks. This poor posture shifts the user’s weight from the sitting bones (ischial tuberosities) onto the sacrum and tailbone. This weight distribution increases the potential for pressure injuries, leading to skin breakdown and infection.
Preventing this forward migration maintains skin integrity and overall physical function. Sliding forward forces the spine into a rounded, kyphotic posture, which restricts the chest and abdomen. This constriction can compromise respiratory function and put pressure on internal organs.
Identifying Why Sliding Occurs
Sliding is usually a symptom of a deeper issue, often related to an improperly fitted chair or changes in the user’s physical condition. A common cause is a seat that is too deep, preventing the user from sitting all the way back and causing them to slide forward to relieve pressure behind the knees. A seat that is too wide encourages the user to lean to one side, destabilizing the pelvis and promoting slumping.
Insufficient foot support is another frequent contributor. Users will slide forward to place their feet on the floor if the footrests are too high or if their feet are dangling. This movement is often an attempt to seek stability. Physical factors such as fatigue, muscle weakness, involuntary movements like spasticity, or tight hamstrings can also pull the pelvis forward into a posterior tilt, initiating the slide.
Immediate Positional and Postural Techniques
Before resorting to specialized equipment, several adjustments can be made using the chair’s existing features to improve posture. The goal is to ensure the pelvis is positioned as far back as possible against the backrest to achieve a neutral or slightly anterior tilt. A caregiver can physically guide the user’s pelvis back into the seat, confirming they are sitting on their sitting bones rather than their tailbone.
If the wheelchair has a tilt-in-space function, utilizing this feature can immediately counteract the effects of gravity. Tilting the user backward by a few degrees shifts the center of gravity and helps keep the pelvis against the backrest, serving as an easy solution for repositioning. Proper footrest height is also important; they should be adjusted so the user’s knees are roughly at a 90-degree angle, allowing the feet to rest flat and stable.
Armrests should be set at a height that allows the shoulders to relax naturally, providing a stable base of support for the trunk. If the armrests are too low, the user may slump; if too high, they may shrug their shoulders. For individuals with upper body strength, using the armrests to push down provides trunk stability, indirectly discouraging forward sliding.
Essential Seating Support Devices
When positional changes alone are insufficient, specialized equipment is necessary to maintain long-term seating stability. Anti-thrust cushions are designed to prevent forward migration. They feature a contoured shape that is lower at the rear and includes a raised pommel in front of the sitting bones. This contour creates a physical barrier, keeping the hips positioned slightly lower than the knees, promoting upright posture and reducing pressure on the sacrum.
Pelvic positioning belts are a direct way to stabilize the pelvis, but they must be used correctly. The belt should be placed low across the pelvis, over the hip bones, and not across the soft abdomen, to secure the bony structure. For optimal positioning, the belt should be angled at approximately 45 to 60 degrees relative to the seat surface, applying backward and downward pressure to lock the pelvis into the seat.
For users who slide due to poor trunk control or leaning, lateral supports and chest harnesses stabilize the upper body. Lateral thoracic supports attach to the backrest and hug the sides of the ribcage, preventing side-to-side leaning and slumping. Improving trunk stability with these devices indirectly reduces the need to slide forward.
Adductor and abductor wedges manage the position of the legs and hips. An abductor wedge, or pommel, is placed between the knees to prevent the legs from coming together, which helps maintain hip alignment. Conversely, adductor supports keep the knees from splaying outward, stabilizing the thighs and pelvis.
When Professional Assessment is Needed
If sliding persists despite careful adjustment and the use of positioning devices, seek a professional seating assessment. Professionals such as Occupational Therapists, Physical Therapists, or certified Assistive Technology Professionals specialize in complex seating issues. They conduct a comprehensive physical evaluation, including a mat assessment, to identify fixed postural deformities, muscle length restrictions, or range of motion limitations that equipment cannot overcome.
Assessment is also necessary if the user has significant changes in their physical status, such as increased spasticity, new contractures, or recurrent skin breakdown. These experts determine if the current wheelchair is the wrong fit or if a more advanced seating system is required. The goal of this specialized evaluation is to match the mobility device to the user’s specific biomechanical needs, ensuring long-term health and functional stability.