Sliding Into the Reality of Posterior Pelvic Tilt

I have most certainly worked with a number of users who slide forward into posterior pelvic tilt. It is a posture which we commonly see when prescribing wheelchairs and seating, and a challenge which sometimes isn’t so straight forward.

When a MAT assessment reveals that the pelvis is flexible and a neutral position is tolerable, yet the user is still sliding forward, other factors should be considered. In this blog, I will cover some of the potential causes which may be contributing to the potential posterior pelvic tilt.

Common Causes and Solutions 

• Hamstring Tightness: Hamstring tightness or spasticity can pull the pelvis into posterior pelvic tilt. To alleviate this, consider decreasing the knee joint angle or potentially opening the seat to back angle.
  
  
• Limited Hip Range of Motion: If a user cannot achieve 90 degrees of hip flexion, they may slide forward to improve their comfort. This often occurs when the chair is fixed, rather than adjusted to the individual’s needs (e.g. a fixed 90 degree seat-to-back angle). The 2021 blog post by Stacey Mullis from the USA explores how the hip's range of motion can affect the sitting posture.
  
  
• Repetitive Movement: Strong extension tone or repeated rocking movements may cause a user to slide forward. Using contoured cushions and/or appropriate accessories may help improve pelvic control. 
  
  
• Ineffective Application of Postural Supports: Is the user wearing a pelvic belt? If so, does it provide sufficient pelvic support and is it anchored at the correct angle?
  
  
• Seat Depth: Is there excessive seat depth? Is this causing the person to slide forward because the seat is too long? 
  
  
• Cushion Considerations: Is the cushion the right size and supportive enough? Contouring or an ischial well can help to control the pelvis. The material of the cushion—foam, gel, air—should be chosen based on both pressure relief and positioning needs of the individual.
  
  
  
• Cushion Orientation: Ensure the cushion is correctly oriented. Incorrect orientation can lead to sliding forward into a posteriorly tilted sitting position.
  
  
• Backrest Considerations: Does the backrest have contouring or the ability to be shaped? A posterior pelvic block can help maintain a neutral pelvis position.

• Foot Support Height: Dropped foot supports, or foot supports not being used, can contribute to the pelvis moving into posterior pelvic tilt. Ensure accurate lower leg length measurements are taken to ensure the foot supports are positioned at an optimal height.

• Rough Terrain: Regularly navigating rough terrain can affect the user’s position over time. For power wheelchair users, consider adjusting suspension or drive settings to provide a smoother ride and reduce the likelihood of sliding forward. 

A combination of these factors is often responsible for a user sliding forward and multiple strategies are typically needed to overcome this problem to achieve optimal results. When in doubt, I would recommend that you complete a MAT assessment and a review of the wheelchair and seating. This should allow you to identify the potential cause/s and implement the individualised solutions to maximise comfort and function for the user!

If you are not sure where to start, I would encourage you to check out Permobil’s  Clinical Resources Page. A copy of the MAT assessment form can also be found here. If you have any further questions, please do not hesitate to reach out to the clinical services team directly at education.apac@permobil.com.

Author

Ben Gommers BAppSc/ MPT

Clinical Services Specialist