Tipping the Balance –evaluating centre of gravity in

manual wheelchair users to optimise propulsion and

stabilityMr Bill Contoyannis1, Mr Jesus Campo Uribe2, Mr Dale Robinson2,

Ms Kim Vien1, Ms Angela Rowe1

1Royal Melbourne Hospital (Melbourne Health), Specialist Wheelchair and Seating Clinic

2The University of Melbourne, Department of Biomedical Engineering

Centre of Gravityu What is it? - the balance point of the whole system – person and wheelchair

WHY?

• Stability• Propulsion Efficiency• Manoeuvrability

Tipping angle

PREVIOUS WORK DONE (CoG CALCULATION)

Tilting platform

Limited or Impractical to use in the

SW&SC Pendulum method

Acceleration method

Suspension method

METHOD

TIPPING ANGLE (TRIGONOMERIC ANALYSIS)

PLATFORM WITH SCALES (STATIC ANALYSIS)

CLINICAL TESTING

Anti - tippers

Clinical Assessment

Setting up a wheelchair to achieve other goals may lead to changes in the centre of gravity and therefore the self propulsion efficiency and stability of the client in their wheelchair.

International Classification of Functioning, Disability and Health (2017)

Clinical Assessment – Relevant to centre of gravity set up

u History: - Stability – Falls/near misses, mechanism of falls, direction- forwards/ backwards/sideways?

- Repair History

u Environment – Home/Community Assessment, gradients that the client typically uses.

u Wheelchair Skills (https://wheelchairskillsprogram.ca/en/)

u Transfer technique

- Side transfer: loading on the front of the wheelchair

- Loading on the footplate i.e. floor to wheelchair.

- Stand to sit – any momentum backwards.

u ADLs and Reach – understanding all of the required activities of daily living i.e. leaning back for catheterisation, leaning forwards for functional activities.

u Self Propulsion assessment:

- Dynamic movement analysis including joint biomechanics and type of stroke- Amount of wheel being utilized and shoulder/trunk position over wheel.- Ideally the height of the wheelchair should be set up so that when the hand is placed at the top centre of the pushrim, the elbow is flexed 60-80 degrees2

- Factors relating to the wheelchair ie. frame, tyres.

- There is evidence1 that the more forwards the rear wheel is positioned, the greater the improvement in pushrim biomechanics, shoulder joint forces, push frequency, speed, acceleration and stroke angle.

1Mulroy et al. 2005; Samuelsson et al. 2004; Boninger et al. 2000; Freixes et al. 2010 2 Consortium for Spinal Cord Medicine (2005). Preservation of Upper limb function following spinal cord injury: Clinical Practice Guidelines for Health Care Professionals

u Pain: Case study

u Spasticity:

Extensor/flexor patterning and movement in wheelchair (dynamic back canes, pushing through footplates) and impact on stability.

u Posture - Anterior pelvic tilt/lordosis vs Posterior pelvic tilt/kyphosis

- Improving posture – impact of sitting more upright

- Increased sagittal thigh angle/rake

Body Distribution

- Each body type is unique - Gluteal shelf- Amputees- Lower limb oedema- Changes over time - weight,

pregnancy.

Carer Assistance

u Attendant Propel

- Ease of pushing

- Ease of turning

Demonstration Session - Questions

In each scenario…

u Where does the centre of gravity move to?

u How does the weight distribution change (front to back)?

u How does the rearward stability change?

u How does the forward stability change?

u Is it easier to push and manoeuvre?

QUALITATIVE EFFECTS OF SOME ADJUSTMENTS MADE TO MANUAL WHEELCHAIRS3

Adapted from: Tomlinson JD. Managing maneuverability and rear stability of adjustable manual wheelchairs: an update. Physical therapy. 2000;80(9):904-11.AS/NZS ISO 7176.1:2015 Wheelchairs - Part 1: Determination of static stability.Prepared by Jesus Campo Uribe, Bill Contoyannis, Angela Rowe and Kim Vien. Wheelchair and Seating Clinic, The Royal Melbourne Hospital.

Conclusions: What is the ideal tipping angle?- Unique to each client

- Initially Measure in our Assessment – establish whether we are aiming to increase or decrease from baseline?

- Is the goal to increase self propulsion efficiency or stability?

- Impact of set up relating to other goals – clinical reasoning process. Have we changed the tipping angle while trying to address other goals?

Clinical Practice:

u Regularly measure tipping angle

u When comparing wheelchairs, make sure you are comparing like for like…

u When adjusting or modifying a wheelchair, ensure tipping angle is right for the client – minor changes can have a big effect

u Use and set up of anti-tippers

u Consider weight distribution over front and rear wheels

u Over time: Not static! Keep reviewing and changing centre of gravity positioning to meet the needs of your client. These needs may change!

Referencesu 1. Campo Uribe JA. Identification and Visualisation of the Centre of Gravity of a Wheelchair User [Biomedical Engineering Capstone

Project]. Melbourne, Vic: The University of Melbourne; 2018.

u 2. AS/NZS ISO 7176.1:2015 Wheelchairs - Part 1: Determination of static stability.

u 3. Tomlinson JD. Managing maneuverability and rear stability of adjustable manual wheelchairs: an update. Physical therapy. 2000;80(9):904-11.

u 4. Kotajarvi BR, Sabick MB, An K-N, Zhao KD. The effect of seat position on wheelchair propulsion biomechanics. Journal of rehabilitation research and development. 2004;41(3B):403.

u 5. Samuelsson KA, Tropp H, Nylander E, Gerdle B. The effect of rear-wheel position on seating ergonomics and mobility efficiency in wheelchair users with spinal cord injuries: a pilot study. Journal of rehabilitation research and development. 2004;41(1):65.

u 6. Asahara S, Yamamoto S. A method for the determination of center of gravity during manual wheelchair propulsion in different axle positions. Journal of Physical Therapy Science. 2007;19(1):57-63.

u International Classification of Functioning, Disability and Health (2017)

u Mulroy SJ, Newsam CJ, Gutierrez DD, et al. Effect of fore-aft seat position on shoulder demands during wheelchair propulsion: part 1. A kinetic analysis. J Spinal Cord Med 2005;28(3):214-21.

u Samuelsson KA, Tropp H, Nylander E, Gerdle B. The effect of rear-wheel position on seating ergonomics and mobility efficiency in wheelchair users with spinal cord injuries: a pilot study. J Rehabil Res Dev 2004;41(1):65-74.

u Boninger ML, Baldwin M, Cooper RA, Koontz A, Chan L. Manual wheelchair pushrim biomechanics and axle position. Arch Phys Med Rehabil 2000;81(5):608-13

u Freixes O, Fernandez SA, Gatti MA, Crespo MJ, Olmos LE, Rubel IF. Wheelchair axle position effect on start-up propulsion performance of persons with tetraplegia. J Rehab Research and Dev 2010;47(7):661-8.

u Consortium for Spinal Cord Medicine (2005). Preservation of Upper limb function following spinal cord injury: Clinical Practice Guidelines for Health Care Professionals