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Why Don’t We Use Sub-ASIS Bars Anymore?

Why Don’t We Use Sub-ASIS Bars Anymore?

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

seating dynamics blog sub-asis bar

Sub-ASIS bar

Ok, I have a confession to make, I used to recommend sub-ASIS bars.

For those of you who are not familiar with this seating component, it is basically a padded bar that is mounted in front of the pelvis, just under (sub) the anterior superior iliac spine (ASIS). This was used instead of a pelvic positioning belt when nothing, and I mean nothing, could keep the pelvis in position. It had to be mounted just right so that it could be latched closed after the client was placed in the wheelchair seating system.

Now, sub-ASIS bars are still available, though certainly not used frequently. To the point that a seating and wheeled mobility specialist could be shunned for using one. Why? What changed?

Why did we use sub-ASIS bars in the past?

When sub-ASIS bars first became available, there was no such thing as ‘tone management.’ We were seeing clients with extremely increased muscle tone. And those clients were breaking equipment and hurting themselves. One strategy to control extension was to keep the hips flexed. A sub-ASIS bar did so. If this component was positioned correctly, the pelvis couldn’t move out of position – at all.

Why have we transitioned away from sub-ASIS bar use?

seating dynamics baclofen pump

Baclofen Pump

Over time, a number of concerns arose with sub-ASIS bar use:

  • As the client couldn’t move, there was unrelieved pressure on the ischial tuberosities (ITs). A tilt could be used to redistribute some of this pressure from the buttocks and posterior thighs to the posterior trunk.
  • A sub-ASIS bar could not be used with a reclining back due to shear concerns.
  • If the sub-ASIS bar wasn’t mounted just right, pressure and friction could occur over the ASIS.
  • And, did I mention, the client couldn’t move?

One of the main reasons this component was slowly abandoned with the rise of Tone Management. Physiatrists began using oral medications, injections, and eventually Baclofen intrathecal pumps to reduce muscle tone in different ways. Suddenly, clients who were breaking equipment and injuring themselves were demonstrating reduced hypertonicity and a pelvic positioning belt was often enough, in combination with other seating strategies, to control the position of the pelvis. Better yet, returning to a pelvic positioning belt addressed many of the sub-ASIS concerns listed above.

Tone Management and Wheelchair Seating

While Tone Management had a significant impact on positioning people with increased muscle tone, it was not a panacea for wheelchair seating challenges. When overall muscle tone was reduced, tone was often too low in the trunk and neck, leading to reduced trunk and head control. Side effects, such as drowsiness and increased secretions were an issue. Depending on the type of tone intervention, impact on muscle tone could vary throughout a day (with oral tone medications) or over time (as a Botox injection wore off). Tone medications are notorious for lowering the seizure threshold and some clients simply could not tolerate these interventions at all or at an effective dose.

Even with Tone management interventions, clients still needed to move. This movement often led to a loss of position of the pelvis and an increase in hypertonicity.

Dynamic Seating and Hypertonicity

Many people who have a Tone Management plan will also benefit from Dynamic Seating at the back, legs, and/or head. Dynamic Seating moves in response to client force and, in the case of hypertonicity, diffuses those forces. Dynamic backs are designed to allow movement at the pelvis without a loss of position. By raising the pivot point to be as close as possible to the natural pivot point of the hip, the pelvis can move into a posterior tilt during hip extension and yet return to a neutral starting position.

We’ve come a long ways since sub-ASIS bars first became available. Sub-ASIS bars immobilized the hips in flexion to inhibit extension. Tone management reduced overall tone or tone in specific areas. Dynamic Seating diffuses extensor tone through movement and prevents loss of client position through design.

Let’s keep moving forward and meeting the needs of clients with increased muscle tone through appropriate wheelchair seating!


  1. Missy Ball on March 16, 2023 at 10:31 am

    well written article

    • Michelle Lange on March 20, 2023 at 12:41 pm

      Thanks Missy!

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