f you’re going to attend the International Seating Symposium, make sure to visit the Vicair booth. You’ll find us at booth 708.

Max Rogmans and Carlos Kramer will also be presenting two of the Symposium sessions: “Volumetric Strain Distribution: A Parameter for Tissue Injury Risk” and “Reach out for stability”.

Wednesday March 20 – Session PS1.2 – 10:15 AM
Max Rogmans & Alexander Siefert – 
“Volumetric Strain Distribution: A Parameter for Tissue Injury Risk”

Course Description:

To select the best cushion for a wheelchair few tools are available. The choice is often based on clinical experience in combination with wheelchair user feedback. In order to make evidence based decisions, more information on what happens inside the body is required e.g. what stresses, tissue deformation occur. The Finite Element Method (FEM) is a standard tool providing this capability in many industries. 3D Human Body Models (HBM) have been used for a number of years by car manufacturers such as Daimler or GM to evaluate car seats using data of pressure distribution or the stresses in the lumbar spine. Wölfel has improved existing models for the application into the medical field via a detailed verification process in comparison to MRI data of individuals. This model makes it possible to assess tissue stresses and deformation on different seating surfaces for varying postures. In a case study the Vicair air cell technology was modelled in detail for its effectiveness in combination with the HBM. Finally, the FEM approach was used to compare the Vicair technology with a standard foam by analyzing differences in immersion, pressure distribution and envelopment. In addition, the quantity Volumetric Strain Distribution (VSD) was introduced evaluating the internal tissue state and showing its dependence on posture variations. In combination sound clinical decision making, VSD could be used as a parameter to determine tissue injury risk.

Learning Objectives:

  • List at least three applications of FEM and 3D Human Body Modelling for clinical decision making
  • List at least three applications of where VSD can be used to help determine tissue injury risk
  • Define the link between FEM and tissue injury risk

Presenters: Max Rogmans, MD Netherlands

Max finished a degree as a Medical Doctor at the Free University in Amsterdam in 1986. He founded Vicair BV in 1993, a company dedicated to the design of high end air wheelchair cushions. He is also the inventor of the iShear: a device that measures total shear in the seat plane in order to improve the wheelchair set up.

Alexander Siefert, PhD
Wölfel Engineering GmbH &, Germany

Alexander Siefert is working at Wölfel since 2003 at leads currently the seating department as an engineering director. He made his PHD at the TU Darmstadt about the topic: “Numerical modelling of mechanical properties of the human tissue and its implementation in a whole body model”. He published several papers in the field of human body modelling and made a lot of presentation on international conferences about seating, human modelling and pressure sores.


  1. Siefert et al (2012). FE-model CASIMIR enhanced muscle tissue approach, International Journal of Human Factors, Volume 3, Issue 3-4
  2. Siefert et al (2016). Occupant Comfort – A mixture of Joint Angles, Seat Pressure and Tissue Loads, SAE Technical Paper 2016-01-1438
  3. Siefert et al (2018). Virtual Human Model CASIMIR – A Chance and a Challenge for the Aetiology Understanding of Pressure Injury Development, Proceedings Science of Experience Conference, Boston

Friday March 22 –  Session PS15.3 – 08:30 AM
Carlos Kramer – 
“Reach out for stability”

Course Description:

For people in wheelchairs, it is essential to be mobile. An important aspect of a wheelchair is the seat cushion, which should provide positioning, pressure redistribution, comfort and stability. Stability depends on different aspects, such as the amount of immersion, addressing different pelvic loading areas and increased support surface. Cushions with the ideal set-up of these aspects, in combination with the biggest reaction force, are considered as offering the most stability. Stability in this study is defined as the amount in which a wheelchair cushion is able to prevent the person from falling over during reaching. A Modified Functional Reach Test is the method used to get insight in the limits of stability in this study. Six cushions of different support mediums are being compared in the distance in which people can reach sideways down, sideways horizontally and sideways up. The measurements are taken in front of a camera on an adjustable chair designed for this study. There were two participant groups, one able body group and one wheelchair user group (spina bifida/spinal cord injury, level L2 or lower). A video-analysis was statistically processed with Kinovea and SPSS. Results of the study show that there are significant differences between different wheelchair cushions in both groups when reaching sideways horizontally and sideways up. There were no significant differences between the different wheelchair cushions in both groups when reaching sideways down.

Learning Objectives:

  • Define three different types of stability
  • Explain the difference in stability caused by different seating surfaces
  • Describe stability related to different pelvic loading areas (PLA)

Presenters: Carlos Kramer, Head of Education at Vicair, is a Dutch Seating & Positioning specialist. He specialized in seating and positioning through working for care and rehabilitation centres, rehab vendors, and through working with internationally renowned seating specialists. Carlos has an educational background in physics and teaching secondary schools. As Vicair’s Head of Education, he combines his expertise in teaching and passion for seating to provide high quality education in the field worldwide.

  1. Field-Fotte, E.C., Ray, S.S. (2010). Seated Reach Distance and Trunk Excursion Accurately Reflect Dynamic Postural Control in Individuals with Motor-incomplete Spinal Cord Injury. Spinal Cord, Volume48(10)
  2. Gao, K.L., Chan, K.M., Purves, S., Tsang, W.N. (2015). Reliability of dynamic sitting balance tests and their correlations with functional mobility for wheelchair users with chronic spinal cord injury. Journal of Orthopaedic Translation, Volume 3(1), 44-49.
  3. Karimi, T.M., Solomonidis, S. (2011). The relationship between parameters of static and dynamic stability tests. Journal of Research in Medical Sciences, Volume 16(4).

Make sure you attend when you’re there! Bring your friends & colleagues ?