Positioning the Pelvis: addressing Pelvic Rotation

In previous blogs, we have discussed posterior and anterior pelvic tilt causes, interventions, and goals. In this blog we will address rotation of the pelvis. When the pelvis is rotated, one anterior superior iliac spine (ASIS) is forward of the other. As a result, the client may appear to have a leg length discrepancy as one knee may be more forward of the other. The client will most likely face forward and the spine may rotate with the pelvis as our brain is wired to view the world face-on – rotating the spine in relation to the pelvis.

Stealth Products Medial and Lateral knee supports
Stealth Products medial and
lateral knee supports

Causes and Interventions

Range of Motion Limitations Pelvic rotation is most often caused by range of motion limitations in the hips, specifically in hip adduction and abduction leading to a windswept tendency. In a windswept tendency, one leg is adducted and internally rotated and the other leg is abducted and externally rotated. It is tempting to grab the client’s knees and swing those legs into a neutral alignment – but doing so results in pelvic rotation. We need to align the pelvis in neutral rotation and accommodate the windswept tendency. How? Place a lateral knee block at the abducted leg and a medial knee block on the adducted leg to prevent movement beyond which the pelvis can be placed at neutral.

It is tempting to grab the client’s knees and swing those legs into a neutral alignment – but doing so results in pelvic rotation. We need to align the pelvis in neutral rotation and accommodate the windswept tendency. How? Place a lateral knee block at the abducted leg and a medial knee block on the adducted leg to prevent movement beyond which the pelvis can be placed at neutral.

Another consideration in this scenario is nighttime positioning. Nearly all of the clients I work with who demonstrate a windswept tendency have lost range due to their sleep position. In the photos below, you can see that Brady sleeps with his legs in a windswept position. Lacking full hip and knee extension, his legs ‘fall’ to one side during sleep, leading to loss of range. After using sleep positioning interventions to keep his legs in better alignment with his hips during sleep, he regained most of this range. For more information on nighttime positioning, keep an eye out for our next blog!

Invacare Matrx InTouch Stabilite OM cushion with right leg wedge
Invacare Matrx InTouch Stabilite OM cushion with right leg wedge

If hip flexion is more limited on one side, pulling this leg downward may pull that side of the pelvis forward into rotation. In this case, it is important to accommodate the range limitation by closing the seat to back angle at the affected hip. There are cushions available that can accommodate the need for more flexion on one side of the cushion, sometimes called a split angle cushion.

If the range limitations are non-reducible, it may not be possible to place the pelvis in neutral without rotating the spine. It is critical that the client face forward and so the pelvis may have to be accommodated in a rotated position. This may require molded seating for pressure distribution along the posterior pelvis and trunk.

Leg Length Discrepancies

If  a client has an actual or apparent leg length discrepancy, using a standard cushion may pull the shorter leg forward, and the pelvis along with it, into rotation. The femurs may actually be of differing lengths, but often a dislocated hip can give the appearance of a leg length discrepancy. The client requires an asymmetrical seat depth so that both legs are well supported without creating pelvic rotation.

Discomfort

If a hip is painful, the client may seek out a position that is more comfortable and this may result in pelvic rotation. It is important to determine if discomfort is present and work with the medical team to remedy the situation.

Tone and Reflexes

Extensor tone or “extensor thrust” can push the pelvis into a rotated position. An Asymmetrical Tonic Neck Reflex (ATNR) leads to increased flexion on one side of the body and increased extension on the other which can also cause pelvic rotation. General positioning strategies which can reduce overall extension include hip flexion and abduction, knee flexion, and ankle dorsiflexion. Positioning strategies to address a posterior pelvic tilt can be used to limit forward movement of one side of the pelvis.


A simple strategy that can reduce rotation is to mount the pelvic positioning belt so that this pulls down on the forward side. This reduces pelvic rotation each time the client is placed in the seating system.

Goals

The goal of addressing pelvic rotation is to achieve a neutral pelvic position, if possible, which will in turn support the anatomical curvatures of the spine, distribute weight over the ischial tuberosities and posterior trunk, and provide optimal alignment for stability and function. If the pelvic rotation is non-reducible, our goal is to provide a forward facing position for the client and to distribute pressure.

Michelle L. Lange, OTR/L, ABDA, ATP/SMS

Kent: Using Anterior Trunk Support to Improve Head Position

Kent is a 14 year old young man with the diagnosis of cerebral palsy. He was referred for evaluation of his wheelchair positioning and access to a communication device. Kent was seen at school with his mother, school team, and supplier.


Mat exam:
Kent had adequate range of motion for sitting, though he had significant internal rotation of his right lower extremity and external rotation of the left lower extremity. He demonstrated significant tone and posturing. His postures were influenced by a strong ATNR and included neck hyperextension and generalized extension and rotation. He appeared to have a kyphotic area of his mid-thoracic spine.


Posture in Manual Wheelchair:
Kent was seated in a linear seating system in a tilt in space manual wheelchair. He reportedly only spent one third of his school day in the wheelchair as he was not positioned well in this system. The linear seating system included a biangular back (though the angle was flattened and so acted as a plain linear surface), antithrust seat, pelvic positioning belt, lateral chest pads, shoulder harness, lateral knee supports, medial knee support, and Stealth Products Comfort Plus head support.


In the seating system, Kent displayed a pelvic posterior tilt, pelvic obliquity (left high), pelvic rotation (left forward), trunk kyphosis, and lateral trunk flexion (shortened on right). He also exhibited lower extremity internal rotation on the right and external rotation on the left. It was possible to reposition Kent to achieve a neutral pelvic position within the seating system, though the pelvic belt needed to be closer to a 60 degree attachment angle to better control his tendency toward posterior pelvic tilt.


Kent was positioned in significant neck hyperextension in this seating system. This led to an upward gaze which limited his ability to see the environment around him, including his communication device display. Kent also frequently aspirated and this hyperextension increased this risk significantly.


Solution:
We repositioned Kent within the seating system, moving the pelvic belt to 60 degrees and adjusting the footrests and shoeholders to accommodate his lower extremity rotation. Although his position was already greatly improved, his neck remained very hyperextended.

Take a look at figure 1 below. Look how far Kent’s shoulder is from the back of the seating system. He was over 6” forward of the back. This was because he tended to ‘pivot’ his head against the head support, pushing his trunk forward. The anterior trunk support was tightened and the head support brought forward to provide counter-pressure to achieve a more neutral neck alignment (see figure 2 – his Mom is brushing the hair out of his eyes, not holding his head up).

Much of wheelchair positioning involves force and counterforce. Only providing force / point of contact behind the head was inadequate to prevent Kent’s neck hyperextension. By providing a counterforce / point of contact at the anterior trunk, his neck could be successfully aligned. Kent’s line of vision was vastly improved and safety in swallow was increased.

So why hadn’t anyone tightened the shoulder straps before? First, Kent’s Mom was convinced that this would cause him pain. We discussed this at length before making the change. Second, his Mom was sure that the head support just needed to be moved forward. As a matter of fact, we took these photos to compare his positioning to convince his Mom that tightening the anterior trunk support would address this issue, not moving the head support forward.

Access:
Once Kent’s head position was addressed, finding a successful switch site for accessing the communication device via scanning was fairly straight forward. He was able to successfully use a Microlight switch mounted on a swing-away assembly (off of the Comfort Plus head support) by his left cheek bone (see figure 3). (Kent now uses a Microlight switch by his left cheek bone)

Many times, improving head position means improving overall body position first. I’m so glad Kent is better positioned and can access his communication device!

Positioning the Pelvis: addressing Anterior Pelvic Tilt

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