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State Spinal Cord Injury Service

Spinal Seating Modules

The purpose of specific body measurements

A well-fitted seating and wheeled mobility system requires a ‘made-to-measure’ solution. Generally, the more seating surface that is in contact with the client, the more body measurements need to be obtained for a wheelchair prescription.

Measurements for cushions

For all cushion trials and prescriptions, the mandatory body measurements required are:

  • Hip width
  • Thigh depth
  • Lower leg length*

* The profile/height of the cushion can change the sitting surface height of the seating and mobility system. The foot support should be adjusted, based on lower leg length, in order for the cushion to provide optimum pressure distribution and pelvic stability.

Measurements for back supports

For all posterior/back support prescriptions, the mandatory body measurements required are:

  • Hip width (for low backrest)
  • Scapular height (for low backrest)
  • Chest width (for higher back support)

Additional measurements for back support with thoracic lateral supports are:

  • Chest depth
  • Axilla height

Body measurement from front
Figure 1: Common linear body measures.
Original image from Zollars2, modified by C. Turnbull, used with permission. While A & B are nominally measured at the same place A is a measure of the external aspect of the skin/tissue and B is a measure of the underlying pelvic bone. It may be necessary to apply firm pressure to get an accurate reading.

Linear body measurements

MWC

PWC

Purpose

A

Hip width
(External width across the hips)

**

**

To estimate cushion width, seat width or width between side hip supports

B

GT width
(Distance between the lateral aspect of the greater trochanters)

-

-

To determine relevant cushion width for GT supports / offloading design cushions such as Jay 2 and Jay 2 deep contour cushions

C

External knee   width / width across knees

*

*

To adjust seat width or consider various styles footplate hanger/leg rest options

D

Chest width

**

*

To estimate distance between lateral trunk supports or select appropriate backrest width

To review seat width of MWC - distance between the backcanes at thoracic height is equal/ greater than measure of client's chest width

E

Shoulder width

*

*

To determine distance between arm supports if upper limb positioning and arm supports are required

I

Foot width   (also consider shoe width  for tapered frame)

*

-

To determine minimum width for tapered frame/ single foot support size. (I X2 - for left and right)

* Usefulness for this type of wheeled mobility
Please also refer to Module 5 - description of seating and wheeled mobility for terminology used in the ‘Purpose’ column.

Body measurement from side

Figure 2: Common linear body measures.
Original image from Zollars2, modified by C. Turnbull, used with permission.

Linear body measurements

MWC

PWC

Purpose

F

Thigh depth (most rearward point/sacrum to popliteal fossa)

**

**

To estimate seat depth by deducting:

- ~25mm (1 inch) if  thigh to lower leg angle is >90o

- ~50mm (2 inches) if thigh to lower leg angle is <90o

(prevent seat base contacting calf muscles)

G

Lower leg   length
(Popliteal fossa to  heel / shoe)

**

**

To estimate distance between wheelchair front seat surface to foot support, deduct cushion height from “G”, and add shoe height

H

Foot depth:
(heel to toe & with shoe)

*

*

To select foot support /footplate style, size & accessories, considering the impact of  footplate interference on front castor spins

J

Scapula height:
(Sitting surface to inferior angle of scapula)
For hands-free/hands-dependent sitter only

*

-

To estimate maximum back support height to cushion/sitting surface for unhindered scapulae movement in MWC propulsion

K

Axilla height:
(Sitting surface to axilla)

*

*

The maximum height of the lateral trunk supports from cushion/sitting surface should be 25mm (1 inch) less than this measurement to prevent impingement of axillary nerve.

L

Elbow height:
(Sitting surface to hanging elbow)

*

**

To estimate arm support or lap tray height from seat surface

M

Forearm Depth

*

**

To estimate armrest pad size and approximate joystick mounting position.

N

Shoulder height
(Sitting surface to shoulder)

-

*

Approximated backrest height from cushion/sitting surface for :

-those who use tilt / recline for pressure management

-for the mounting of anterior shoulder / trunk support to provide effective line of pull.

O

Occipital height:
(Sitting surface to occipital ridge)

-

*

To note head support height from sitting surface - particularly important for those with poor head control/use significant amount of tilt

P

Maximum sitting   height:
(Sitting surface to top of head)

*

*

Consider clearance above the head while entering /being transported in vehicles. Overall head to floor height = P + cushion height at ITs + seat to floor height

Q

Trunk depth:
(for backrest style & lateral trunk support)

-

-

To provide optimum support, the depth of lateral trunk supports should be ~ approx. 2/3 of trunk depth for ‘dependant sitters’

* Usefulness for this type of wheeled mobility

References

  1. Babinec M., 2004. Translating evaluation measurements to wheelchair dimensions. Invacare United States. Online article: http://www.invacare.com.au/index.cfm/3,168,522/measurements-to-wc-geometries.pdf Accessed 25/02/16.
  2. Zollars, J.A., (Illus. Knezevich, J.), 1996. Special seating: An illustrated guide. Otto Bock Orthopaedic Indus., Inc., pp120.