An anterior pelvic tilt occurs when the top of the pelvis is tipped or rotated anteriorly. This leads to extension of the lower spine (lordosis). In a significant anterior tilt, pressure may occur on the coccyx (against the back of the seating system) and even the pubic symphysis (against the cushion). As the position of the pelvis impacts the position of the trunk and subsequently the head, we need to reduce this tendency, as much as possible.
What Causes an Anterior Pelvic Tilt?
• An anterior pelvic tilt may be caused by low tone or muscle weakness in the trunk, leading to forward collapse.
• Lordosis may present initially, pulling the pelvis into an anterior tilt.
• Anterior pelvic tilt is common in boys with Duchenne Muscular Dystrophy as the body leans further and further forward in an attempt to balance the head.
• If the hip flexors are very tight, extending the hips will pull the pelvis into an anterior tilt.
So, What Can We Do?
The angle of the pelvic positioning belt is critical. In a posterior pelvic tilt, a 60 degree angle of attachment is recommended. In an anterior pelvic tilt, a 30 degree angle is recommended. This angle places the pelvic belt across the Anterior Superior Iliac Spine (ASIS), pulling the pelvis back into a neutral position. It is easy for this pelvic belt to slip above the ASIS onto soft tissue, and so a 4 point pelvic belt is often used in these circumstances. The primary belt is placed at 30 degrees and the secondary belt is positioned at 60 or 90 degrees to maintain the angle of the primary belt.
Another option is a Belly Binder, also referred to as an abdominal panel or corset. This is typically custom made to an individual and must fit closely to the lateral trunk. The binder spans the lower rib cage and upper pelvis so as to avoid pressure on abdominal soft tissue. This pressure reduces a pelvic anterior tilt and lordosis and may even provide some diaphragmic support for clients with muscle weakness.
If the hip flexors are tight, the seat to back angle must be closed to match the range limitation, preventing the pelvis from being pulled into an anterior tilt. If the seat to back angle must be less than 90 degrees, a wedge shaped cushion can be used to achieve the necessary angle.
If an anterior tilt is not fully reducible, molded seating may be required to distribute pressure and minimize further progression.
The goals of reducing an anterior pelvic tilt are to reduce the accompanying lordosis, achieve a neutral pelvic rotation, promote weight bearing on the ischial tuberosities, and to provide alignment and stability for function.
Michelle L. Lange, OTR/L, ABDA, ATP/SMS