Note: Descriptions are shown in the official language in which they were submitted.
CA 02545963 2013-04-30
Seat Cushion With Adjustable Contour and
Method of Adjusting the Contour of a Seat Cushion
Cross-Reference to Related Applications
This invention is a continuation in part of U.S. patent publication No.
2005/0022305, filed July 28, 2003 and published February 3, 2005, for a
Contoured Seat Cushion and Method for Offloading Pressure from Skeletal Bone
Prominences and Encouraging Proper Postural Alignment. This invention is also
related to other inventions made by at least one of the inventors herein for
Individually-Contoured Seat Cushion and Shape Capturing and Fabricating Method
for Seat Cushion described in U.S. patent publication No.2005/0025953,
published
on February 3, 2005, and for Modular Seat Cushion with Interlocking Human
Support and Base Portions and Method of Creating and Using a Seat Cushion
described in U.S. patent publication No. 2005/0023872, published on
February 3, 2005, and for Apparatus and Method for Evaluating Clearance from a
Contoured Seat Cushion described in U.S. patent publication No. 2005/0022406,
filed on July 28, 2003, published on February 3, 2005 and issued as U.S.
Patent
No. 6,990,744 on January 31, 2006, and for Reinforcing and Adjustable
Contoured
Seat Cushion and Method of Reinforcing and Adjusting the Contoured Seat
Cushion described in U.S. patent publication No. 2005/0022306, filed on
January
28, 2004 and published on February 3, 2005, all of which are assigned to the
assignee of the present invention.
Field of the Invention
This invention relates to seat cushions, and more particularly, to a new and
improved seat cushion having an adjustable support contour that provides a
range
of users with a proper orientation of posture while reducing or eliminating
the
incidence of pressure ulcers. The support contour offloads or isolates
pressure
and shear forces from skin tissue surrounding the bony prominences of the
pelvic
skeletal bone structure, such as the ischial tuberosities, greater
trochanters, coccyx
and sacrum, thereby removing pressure and shear forces from those areas which
are susceptible to injury from prolonged sitting. Proper postural alignment is
achieved by transferring the pressure from the offloaded areas to greater
masses
CA 02545963 2006-05-09
of tissue not associated with bony prominences, such as the proximal thighs
and
the posterior lateral buttocks. The additional support from these areas
encourages
improved postural alignment and control.
Background of the Invention
A wheelchair seat cushion must perform a number of important functions.
The seat cushion should be comfortable and capable of providing proper support
for optimal posture and posture control for a considerable length of time. The
seat
cushion should also assist, or at least not materially hinder, the user in
maneuvering the wheelchair, permit a useful range of motion from the pelvis
and
upper torso of the person, and create stability and security for the person
within the
wheelchair. Perhaps most importantly, the seat cushion should help prevent and
reduce the incidence of pressure ulcers created by prolonged sitting on the
cushion without adequate pressure relief. Pressure ulcers can become a very
serious health problem for individuals who must remain constantly in contact
with
the support cushion, and it is important to avoid such pressure ulcers.
Wheelchair users, like everyone, are of substantially different sizes, weights
and shapes. Many wheelchair users have physical disabilities and associated
posture and postural control impairments such as those typically caused by
congenital disorders. Other wheelchair users, such as those who have been
disabled by acquired or traumatic injuries, may have a more typical size and
shape. In all of these cases, the support contour of the wheelchair seat
cushion
must safely support the anatomy of the user, whether the anatomy is abnormal
or
more typical. Wheelchair seat cushions must fit and perform properly to
prevent
further physical impairment and pressure ulcers. The cushion must also enhance
the functional capabilities of the user by supporting independence in
activities of
daily living. There are a number of different theories or approaches for
configuring
the support contour of a wheelchair seat cushion to avoid pressure ulcers and
to
provide adequate postural alignment.
One approach to configuring the support contour of a wheelchair seat
cushion is a single generic support contour which attempts to accommodate all
types of pelvic bone-structure configurations, whether more abnormal or more
2
CA 02545963 2006-05-09
typical. In general, this generic approach involves using a soft, flowable or
adaptable material, such as air or gel, as the support material within the
wheelchair
cushion. This adaptable material adjusts and redistributes in response to the
weight and shape of the user to create a support contour which conforms to the
anatomy of the user. By conforming to the anatomy of the user, the pressure on
the skin of the user is usually distributed relatively evenly over the area of
contact.
The extent of the uniform pressure distribution depends on the capability of
the
cushion to accept and conform to the user's anatomy without displacing the
adaptable material and resulting in firm contact with a support structure.
The substantially equal pressure distribution is theorized to reduce the
incidence of pressure ulcers, by decreasing peak pressures on the skin in the
pelvic area associated with bony prominences, most notably the ischial
tuberosities, coccyx, sacrum, and greater trochanters. However, as individuals
age
with their disabilities, the quality of their skin is further compromised in
its ability to
tolerate pressure and shear forces. The decreased tolerance for pressure and
shear forces, no matter how well those forces are distributed, increases the
incidence of pressure ulcers.
Generic seat cushions which use flowable support material are usually
incapable of providing adequate postural alignment. In general terms, adequate
postural alignment is assisted by using the support contour of the seat
cushion to
encourage proper posture by providing a foundation for dynamic posture
control.
To do so, the support contour must have the capability of applying some
support
pressure to the pelvic area because alignment of the pelvic area is
fundamental for
proper posture. The adaptable support material of generic seat cushions is
intended to move and redistribute itself, and consequently, is generally
unstable
and incapable of applying the support pressure or force in certain areas of
the
pelvic anatomy to optimize postural control and alignment.
Many of the disadvantages associated with generic wheelchair cushions
may be overcome by using a custom wheelchair seat cushion having a support
contour constructed specifically to accommodate the individual anatomical
aspects
of a particular user. In such cases, it is necessary to capture the anatomical
shape
3
CA 02545963 2006-05-09
of the individual which will contact the custom seat cushion, and then use
that
anatomical shape to make the custom seat cushion.
The cost of fabricating a custom wheelchair seat cushion can be substantial,
for example, approximately $3000 or more. Much of the expense of a custom
wheelchair seat cushion results from the amount of time consumed, and the cost
of the relatively sophisticated equipment which must be used to capture and
transfer the anatomical shape of the user into the support contour of the seat
cushion. Moreover, despite the use of sophisticated equipment, it is
nevertheless
difficult to capture the anatomical shape of the user and transfer it into a
customized support contour. An appreciation of some of these difficulties in
creating customized wheelchair seat cushions is discussed in the above-
referenced U.S. patent application Serial No. 10/628,858.
Even if the support contour of the custom cushion is initially satisfactory to
the user, changes in tissue and musculature may dictate changes in the optimal
support contour of the custom seat cushion. Tissue will typically atrophy over
time,
particularly for first-time wheelchair users. Tissue atrophy and other tissue
changes alter the pressure distribution over the support contour. Those
changes
may result in increased pressure on tissues surrounding the bony prominences,
thereby ultimately increasing the risks of pressure ulcers. Moreover, as the
muscle
strength diminishes, the user relies more on the support contour of the seat
to hold
the proper posture. In doing so, parts of the pelvic anatomy press more
directly on
certain parts of the support contour as a foundation for postural alignment.
The
increased pressure from a change in tissue mass and postural alignment
increases
the pressure and shear forces on the skin in those areas, again increasing the
risk
of pressure ulcers.
In those types of existing wheelchair cushions having individualized support
contours intended to interact with the anatomy of a specific user, slight
discrepancies in capturing the shape of the individualized support may be
compensated for by adding shims or other additional external support
structures to
the seat cushion or to a structural base upon which the cushion resides. The
addition of shims or other support structures to an individualized support
contour is
4
CA 02545963 2006-05-09
relatively imprecise in achieving the desired effect, and requires
considerable time
and effort due to the number of trial fittings that are typically required. A
similar
situation exists with respect to anatomical changes that occur after the
individualized cushion has been used for some amount of time. In both
circumstances, the support capabilities of the cushion are inhibited by the
trial and
error approach to correcting for shape-capturing discrepancies and anatomical
changes. Furthermore, the added shims and external support structures
complicate the use of the cushion, because the added parts must be kept in
alignment with the cushion when in use.
In those types of existing wheelchair cushions which establish an
individualized or specific support contour, certain areas of the support
contour may
be subject to excessive deformation of the flexible support material from
which the
cushion is constructed. The wheelchair cushions must be constructed of
material
which offers some amount of flexibility or resiliency in order to function
adequately
as a cushion. The flexible or resilient material is subject to deformation in
areas of
significant curvature or areas which laterally support the anatomical
structure of the
user. These areas of the support contour may have generally thinner dimensions
than the portions of the seat cushion directly beneath the user, or there is
no
support from any lateral structure to reinforce these areas because of the
seat
support structure beneath the cushion. Excessively flexible portions of the
wheelchair cushion, or portions which may become excessively flexible through
use over time, are usually not capable of providing pelvic orientation and
alignment
as may be required by the wheelchair user.
Because of these and other deficiencies, seat cushions with inadequate
support may be used long past the time when they have become ineffective in
providing proper support, either because of the cost associated with
replacement
of the cushion or the failure of the user to recognize the problem until
pressure
ulcers or other difficulties appear.
Many of the same considerations applicable to wheelchair seat cushions
also apply with varying levels of criticality to other types of seat cushions
used in
other seating environments and applications. For example, seat cushions used
in
5
CA 02545963 2006-05-09
office environments are required to support the user in a comfortable manner
and
in a manner which encourages proper posture and without creating risks of
medical problems, for example inducing blood circulatory problems.
Summary of the Invention
The present invention involves adjusting a standard support contour of a
seat cushion to address the individual needs of a user and to obtain the best
conditions for isolating and offloading pressure and shear forces from the
skin
surrounding the bony prominences of the pelvic area skeletal structure and for
transferring greater pressure and providing firmer support to areas of the
anatomy
which have broader masses of soft and muscle tissue not surrounding bony
prominences. Offloading or isolating the pressure and shear force from the
skin
surrounding the bony prominences of the pelvic skeletal structure reduces the
risk
of pressure ulcers. Transferring pressure and providing pronounced support to
broad tissue masses encourages better balance and alignment. Greater support
pressure is applied to and maintained on those areas which bias, orient or
encourage alignment of the pelvic structure toward proper postural alignment.
By
offloading the pressure and shear forces from those areas which are prone to
skin
ulcers, and transferring support pressure to those areas which encourage
proper
postural alignment, the support contour of the seat cushion simultaneously
achieves the two most important wheelchair cushion functions: avoidance of
pressure ulcers, and postural alignment and control.
The adjustment capability of the support contour also makes the cushion
adaptable to a wider range of variations in the size and shape of the normal
human
anatomy, primarily as a result of the additional clearance in the areas of the
bony
prominences and the additional support in the areas of broader tissue and
muscular masses. The greater relief or clearance in the areas of the bony
prominences and the greater support in the areas of broader tissue and
muscular
mass, makes the support contour generally applicable to classes of individuals
having generally similar pelvic anatomies.
These and other features of the present invention are realized in an
adjustable contoured seat cushion for supporting a person in a seated
position.
6
CA 02545963 2006-05-09
The seat cushion includes a support structure having a top surface with a
support
contour, the support contour defining relief areas which are positioned to
align with
bony prominences of the person and support areas that are positioned to align
with
skin covering tissue masses spaced from the bony prominences. The seat
cushion also includes an insertion member and an opening or slits formed in
one
or both of the rear corners of the support structure to receive the insertion
member.
The slits are positioned between the top surface and a bottom surface of the
support structure. A support area of the support contour changes position
relative
to other support areas or relief areas when the insertion member is inserted
into
one of the slits.
Another aspect of the invention involves a method of manufacturing a
resilient seat cushion for supporting a person in a seated position. The
method
comprises forming a support structure by forming generally opposite front and
a
rear sides and generally opposite left and right sides. The rear side
intersects the
left and right sides at rear corners of the support structure. The support
structure
further includes a bottom surface extending between the front and rear sides
and
between the left and right sides, and a top surface generally opposite of the
bottom
surface and extending between the front and rear sides and the left and right
sides. The top surface defines a support contour of the support structure
which
has relief areas and support areas. The relief areas align with the bony
prominences of the person when the person is seated on the cushion and the
support areas align with skin covering tissue masses spaced from the bony
prominences including skin covering a posterior lateral buttocks of the
person. The
method involves forming an opening or slit in each of the rear corners. Each
opening is adapted to receive an insertion member, and when the insertion
member is inserted, the support contour is adjusted in a manner to better
support
the user.
Another aspect of the invention involves a method of adjusting a seat
cushion to support a person in a seated position on a resilient support
structure of
the seat cushion. The method involves inserting an insertion member into an
opening in a portion of the support structure.
7
CA 02545963 2013-04-30
A further aspect of the present invention involves a seat cushion kit which
includes a seat support structure having an upper support contour for
supporting a
user. The support structure includes a portion having an opening. The kit also
includes a cover which encases the support contour to protect the support
contour
and which resists outward deformation of the support structure. The kit also
includes a clearance measuring device for measuring clearance between the
user's anatomy and the support contour. The insertion member is inserted into
the
opening to adjust a position of a support area of the support structure to
better
support the user.
In accordance with one aspect then, there is provided a contoured seat
cushion for supporting a person in a seated position thereon, the person
having a
pelvic area with bony prominences and tissue masses spaced from the bony
prominences, the tissue masses including posterior lateral buttocks,
comprising: a
support structure made from a resilient material, the support structure
including
generally opposite front and rear sides, generally opposite left and right
sides, a
bottom surface extending between the front and rear sides and between the left
and right sides, and a top surface generally opposite of the bottom surface
and
extending between the front and rear sides and the left and right sides; the
top
surface configured as a support contour defining relief areas and support
areas,
the relief areas positioned to align with the bony prominences of a person
when the
person is seated on the cushion, and the support areas positioned to align
with the
tissue masses of the posterior lateral buttocks; an insertion member; openings
formed in each of the rear corners between the top surface and the bottom
surface
of the support structure to receive the insertion member, the openings
positioned
between the top surface and the bottom surface, and a support area of the
support
contour changing position relative to other support areas or relief areas when
the
8
CA 02545963 2013-04-30
insertion member is inserted into one of the openings; a cover made from a
substantially non-stretchable material, the cover sized to encase the support
structure to resist substantial outward deformation of the support structure
when
the person is seated on the seat cushion; and an expansion portion of the
cover
positioned adjacent to the rear corner to expand the cover at the corner to
fit
around the support structure when the insertion member is inserted in the
opening,
the expansion portion including a zipper and a gusset, the zipper opening to
allow
the gusset to expand, and the zipper closing to contract the gusset.
In accordance with another aspect, there is provided a contoured seat
cushion for supporting a person in a seated position thereon, the person
having a
pelvic area with bony prominences and tissue masses spaced from the bony
prominences; the bony prominences of the pelvic area include the ischial
tuberosities, the greater trochanters and the coccyx and sacrum; the tissue
masses of the pelvic area include the tissue masses on opposite lateral sides
of
the posterior buttocks and beneath the proximal thigh bones; the cushion
comprising: a support structure made from a resilient material, the support
structure including generally opposite front and rear sides, generally
opposite left
and right sides, a bottom surface extending between the front and rear sides
and
between the left and right sides, and a top surface generally opposite of the
bottom
surface and extending between the front and rear sides and the left and right
sides; and wherein: the top surface is configured as a support contour
defining
relief areas and support areas; the support areas and relief areas are
separate
from one another; the relief areas are positioned to align with the bony
prominences of a person when the person is seated on the cushion, the support
areas are positioned to align with the tissue masses of the posterior lateral
buttocks; the support areas are at locations adapted to be adjacent to skin at
the
8a
CA 02545963 2013-04-30
tissue masses on the opposite lateral sides of the posterior buttocks and
beneath
the proximal thigh bones; the relief areas are at locations adapted to be
adjacent to
skin covering the ischial tuberosities, the greater trochanters and the coccyx
and
sacrum; and the support areas and the relief areas are spaced relatively more
toward and relatively more away from the anatomical shape of the pelvic area
of
the person when the person is seated on and supported by the support contour;
and wherein the cushion further comprises: an insertion member; and openings
to
receive the insertion member, the openings formed in each of the rear corners
between the top surface and the bottom surface of the support structure, the
openings positioned between the top surface and the bottom surface, and
wherein:
at least one support area of the support contour changing position relative to
other
support areas and relief areas when the insertion member is inserted into one
of
the openings.
In accordance with a further aspect, there is provided a method of adjusting
the contoured seat cushion described above to support a person in a seated
position on the support structure, comprising: inserting the insertion member
into
the opening in the corner of the support structure; and adjusting a position
of the
support area of the support contour by inserting the insertion member into the
opening.
In accordance with a still further aspect, there is provided a method of
adjusting the contoured seat cushion described above to support a person in a
seated position on the support structure, comprising: inserting the insertion
member into the opening in the support structure; adjusting a position of the
support area of the support contour by inserting the insertion member into the
opening; restraining the support structure and the support area against
outward
8b
CA 02545963 2013-04-30
deformation away from the pelvic area by surrounding the support structure
with
the cover; and expanding a portion of the cover to fit over the support
structure
after the insertion member has been inserted.
A more complete appreciation of the scope of the invention and the manner
in which it achieves the above-noted and other improvements can be obtained by
reference to the following detailed description of presently preferred
embodiments
taken in connection with the accompanying drawings, which are briefly
summarized below, and by reference to the appended claims.
Brief Description of the Drawings
Fig. us an upper perspective view of a contoured wheelchair or other seat
cushion which incorporates the present invention, shown with a portion of a
cover
broken away to reveal a support structure with an insert member positioned in
a
slit.
Fig. 2 is a perspective view of the seat cushion shown in Fig. 1, with shading
and crosshatching to illustrate areas of the support contour where pressure is
offloaded and areas where additional support is provided to support a user.
Fig. 3 is a perspective view of the seat cushion shown in Figs. 1 and 2,
showing a typical human pelvic and thigh skeletal structure superimposed over
the
support contour of the seat cushion.
Fig. 4 is a midline longitudinal and vertical cross-sectional view taken
substantially in the plane of line 4-4 of Fig. 3.
Fig. 5 is a transverse and vertical cross-sectional view taken substantially
in
the plane of line 5-5 of Fig. 3.
8c
CA 02545963 2006-05-09
Fig. 6 is a vertical cross-sectional view of a portion of the support contour
and skeletal structure shown in Fig. 3, taken substantially in the plane of
line 6-6 of
Fig. 3.
Fig. 7 is a longitudinal and vertical cross-sectional view taken substantially
in
the plane of line 7-7 of Fig. 3.
Fig. 8 is a transverse and substantially horizontal cross-sectional view taken
substantially in the plane of line 8-8 of Fig. 4.
Fig. 9 is a lower perspective view of the contoured seat cushion shown in
Fig. 1, shown with an access zipper open and the cover partially removed from
the
support contour to reveal the slit and the insert member.
Fig. 10 is a rear elevation view of the seat cushion shown in Fig. 1, showing
the cushion on a flat seat support structure of a wheelchair in an adjusted
position
shown by the solid lines as compared to the unadjusted position of the
position
illustrated by the dashed lines, with portions of the cover broken away to
reveal the
slits and insert members in both rear corners of the support structure.
Fig. 11 is a side elevation view of the seat cushion shown in Fig. 10.
Fig. 12 is top plan view of the seat cushion shown in Fig. 10, with dashed
lines also showing the position of the insert members within the support
structure.
Fig. 13 is a rear elevation view of the seat cushion similar to that shown in
Fig. 10, showing the cushion positioned on a sling type of seat support
structure of
a wheelchair and with a single insert member positioned in the slit in one
corner
and the other corner lacking an insert member.
Fig. 14 is a perspective view of one embodiment of a clearance measuring
device for use with the seat cushion shown in Fig. 1, with a portion broken
away.
Fig. 15 is a midline longitudinal and vertical cross-sectional view taken
substantially in the plane of line 4-4 of Fig. 3, showing use of the clearance
measuring device shown in Fig. 14.
Fig. 16 is a transverse and vertical cross-sectional view taken substantially
in the plane of line 5-5 of Fig. 3, showing use of the clearance measuring
device
shown in Fig. 14.
Detailed Description
9
CA 02545963 2006-05-09
A wheelchair seat cushion 20 which incorporates the present invention is
shown in Fig. 1. The seat cushion 20 includes a resilient seat support
structure 22
which is constructed of resilient plastic foam material and a breathable
material
cover 24 which together are capable of providing the necessary support to the
wheelchair user. A support contour 26 is preferably constructed or otherwise
formed as a part of the support structure 22. Preferably, the resilient
plastic foam
material from which the support structure 22 is formed is a matrix of
polypropylene,
polyurethane, polyethylene or other plastic beads which have been adhered
together during a molding process in which the support contour 26 is formed
simultaneously with the support structure 22, as described more completely in
the
above-referenced U.S. patent application Serial No. 10/628,858.
The support contour 26 is formed, as shown in Fig. 2, with relief areas 28,
30 and 32 which align with skin covering bony prominences of the users pelvic
area, as shown in Fig. 3. Clearances between the bony prominences of the
ischial
tuberosities 34, the greater trochanters 36, and the coccyx 38 and the sacrum
40
and the support contour 26 at the relief areas 28, 30 and 32, respectively,
offload
pressure and shear forces from the skin surrounding these bony prominences.
The support contour 26 is also formed with support areas 42, 44, 46 and 48
which
align with anatomical features of the users pelvic area to support the user by
contacting the skin over muscular portions of the pelvic area. The support
areas
42, 44, 46 and 48 compensate for the increased clearance in the areas 28, 30
and
32, by providing greater protrusion for enhanced support where there are
relatively
large and broad masses of tissue and muscle upon which the greater pressure
can
be applied without creating localized pressure points.
The support contour 26 faces upward to contact and support the tissues of
the user which surround the skeletal structure of the pelvic area 50 and the
thigh
bones 52 of the user, as shown in Figs. 2-8. The support contour 26 includes a
relatively deep center cavity 54 which is positioned in the support contour 26
to be
located directly below ischial tuberosities 34 of the skeletal structure of
the pelvic
area 50, when the user is seated on the cushion 20, as shown in Fig. 4.
CA 02545963 2006-05-09
In the support contour 26, the vertical depth and horizontal dimensions of
the cavity 54 are sufficient to offload pressure and shear force from the skin
surrounding the ischial tuberosities 34. The depth of the cavity 54 is
sufficient to
establish clearances 56, 58 and 60 between the lower ends of the ischial
tuberosities 34 and the lowermost surface area 28, as shown in Figs. 4 and 5.
By
offloading the pressure and shear force from the skin surrounding the ischial
tuberosities 34 due to the clearances 56, 58 and 60, the risk of pressure
ulcers on
the skin surrounding the ischial tuberosities 34 is reduced substantially.
The support contour 26 rises from the lowermost surface area 28 on
opposite transverse sides of the cavity 54 to the relief areas 30, as shown in
Figs.
2 and 3. The relief areas 30 are positioned directly below and transversely to
the
outside of the greater trochanters 36 on both transverse sides of the support
contour 26, when the user is seated on the cushion 20. The relief areas 30
establish vertical and transverse clearances 62 with respect to the greater
trochanters 36 to offload pressure and shear force from the skin surrounding
the
greater trochanters 36, as shown in Fig. 5.
The support contour 26 also includes a recessed channel area 32 which
extends vertically upward from the lowermost surface area 28 of the cavity 54
to an
upper rear edge of the support contour 26, as shown in Figs. 4 and 8. The
channel area 32 is located on a rear wall 66 and extends downwardly and
longitudinally forward from the rear wall 66 toward the lowermost surface area
28
of the cavity 54 at a transverse midline of the support contour 26, as shown
in Fig.
8. The channel area 32 is positioned in the support contour 26 to be located
directly behind the coccyx 38 and the sacrum 40 of the pelvic skeletal
structure 50,
when the user is seated in the cushion 20. The channel area 32 establishes a
vertical and horizontal clearance 68 between the channel area 32 and the
coccyx
38 and sacrum 40, as shown in Fig. 4. The channel area 32 also establishes a
transverse clearance 70 which extends beyond each opposite lateral side of the
coccyx 38 and sacrum 40, as shown in Fig. 8. The amount of the clearances 68
and 70 is sufficient to offload pressure and shear force from the skin
surrounding
the coccyx 38 and sacrum 40.
11
CA 02545963 2006-05-09
The support contour 26 includes the two support areas 42 and 44 which are
located on the rear wall 66 in positions on opposite transverse sides of a
longitudinal midline 72, as shown in Figs. 2, 3 and 8. The support areas 42
and 44
extend forwardly from a midline contour line 74 (Fig. 8), and therefore
provide
more projections to create exaggerated pressure and support on the tissue and
musculature at the posterior lateral buttocks of the pelvic area which is
contacted
by the support areas 42 and 44. As shown in Fig. 6, the support area 42 (the
support area 44 is similar, but not shown in Fig. 6) generally curves
vertically
downwardly and transversely and longitudinally forwardly from an upper
position
on the rear wall 66 toward the lowermost surface area 28. The support areas 42
(and 44, not shown in Fig. 6) terminate vertically above the lowermost surface
area
28. Oriented in this manner, the support areas 42 and 44 define forwardly and
upwardly facing contact surfaces to contact the skin covering the tissue
masses
surrounding the pelvic bones 50 at the lateral posterior buttocks. The
posterior
lateral buttocks tissue and musculature are devoid of any underlying prominent
bone structure. Instead, the considerable mass of posterior lateral buttocks
tissue
and musculature defines a relatively broad and substantial contact area which
is
able to accept and transfer the force into the pelvic skeletal structure which
does
not elevate the risk of developing pressure ulcers at those locations.
The upward component of curvature from the support areas 42 and 44 (Fig.
3) tends to induce an upward lifting force on the posterior/lateral pelvic
area, which
assists in offloading the pressure from the relief areas 28, 30 and 32. The
lateral
buttocks support areas 42 and 44 also provide lateral stability which helps
retain
the user in contact with the support contour 26 of the seat cushion 20. The
lateral
support stability is applied from the opposite sides of the rear portion of
the users
body, and thus tends to inhibit the user from tipping backward or to the side
within
the cushion. The support areas 42 and 44 bias or orient the pelvic area 50 in
a
slightly forward pivoted position (counterclockwise as shown in Fig. 4) to
encourage the user to maintain his or her pelvic area 50 in a proper postural
alignment position.
12
CA 02545963 2006-05-09
The support contour 26 also provides enhanced support from areas 46 and
48 which are located beneath the thigh bone 52 proximal to the greater
trochanters
36, as shown in Figs. 2, 3 and 7. The enhanced support areas 46 and 48 contact
a relatively broad mass of tissue and muscle extending along the posterior
thigh
bone 52. The posterior thigh bone 52 extends generally longitudinally and has
no
prominences in the area where the support areas 46 and 48 contact the tissue
surrounding the posterior thigh bones 52. The support areas 46 and 48 are able
to
transfer a relatively significant amount of pressure into the relatively broad
mass of
posterior thigh tissue and musculature to thereby support the skeletal
structure.
The transfer of significant force into the posterior thigh tissue and
musculature at the location of the support areas 46 and 48 complements the
additional support from the areas 42 and 44 to maintain alignment for proper
postural position of the pelvic area. The location of the support areas 42,
44, 46
and 48, as shown in Fig. 2, is approximately at four lateral and longitudinal
positions surrounding the pelvic structure to facilitate holding the pelvic
structure
into a position of proper postural alignment and to stabilize the user when
seated
on the support contour.
By offloading pressure from the bony prominence areas 28, 30 and 32, and
by applying the exaggerated support in the broad tissue and musculature areas
42,
44, 46 and 48, atrophy changes are less likely to have a significant negative
impact. In general, the added clearance in the areas of the bony prominences
provides an additional tolerance for tissue atrophy.
As described in the referenced U.S. patent application Serial No.
10/628,860, the support contour 26 can be configured to fit the particular
anatomical shape of a user. However, the support contour 26 is preferably
configured with a standardized shape that is suitable to provide improved
support
characteristics for a range of users. In some circumstances it may be
necessary to
make adjustments to the support areas 42 and 44 of the support contour 26 to
adapt a standardized support contour 26 to the individual anatomical shape of
the
user to achieve the maximum benefit. Moreover, because of changes which occur
over time in the anatomical structure of the user, adjustments to the support
13
CA 02545963 2006-05-09
contour 26 may be necessary at different times during the use of the seat
cushion
20.
The present invention offers an improved capability to adjust the support
areas 42 and 44 of the standardized support contour 26 of the seat cushion 20.
As
shown in Figs. 1 and 9-13, adjustment of these support areas is accomplished
by
the insertion of one or more insertion members, such as wedges 76 and 78 into
slits 80 and/or 82. The introduction of the wedges 76 and 78 forces the slits
80 or
82 open and thereby increases a vertical dimension of the support structure 22
in
the locations of the wedges 76 and 78. The expansion of the support structure
22
in these locations, deforms the support structure 22 and changes the shape of
the
support contour 26. As shown in Figs. 10 and 12, the insertion of a wedge 76
into
each of the slits 80 and 82 causes the support areas 42 and 44 to move upward
and transversely inward toward one another. The wedges 76 and 78, as shown in
Figs. 11 and 12, also move the support areas 42 and 44 longitudinally forward.
Changing the shape of the support contour 26 provides the ability to adjust
the contour 26 to the particular needs of an individual user. By inserting one
or
more wedges 76, as shown in Figs 1 and 9-13, the positions of the support
areas
42 and 44 are adjusted and the positions of the user's ischial tuberosities
34,
greater trochanters 36, coccyx 38 and sacrum 40 relative to the support
contour 22
of the seat cushion 20 are adjusted. Inserting wedges 76 and 78 in the slits
80
and 82 moves the support areas 42 and 44 relatively more forward and inward
which causes an increase in the vertical clearance 56 between the ischial
tuberosities 34 and the lower surface area 28 of the support contour 26 as
well as
an increase in the transverse clearance 60. The forward change in the position
of
the support areas 42 and 44 caused by the wedges 76 and 78 pushes the pelvic
bones 50 forward to counteract the tendency of a user to slouch.
The left and right slits 80 and 82 are preferably cut or formed into opposite
transverse rear corners 84 and 86 of the support structure 22, as shown in
Fig. 9.
The left slit 80 extends from a rear transversely-extending side 90 of the
seat
cushion 20 to a longitudinally-extending left side 92 of the cushion (Figs. 9
and 10)
and the right slit 82 extends from the rear side 90 to a longitudinally-
extending right
14
CA 02545963 2006-05-09
side 94 of the cushion 20. The slits 80 and 82 extend in a plane that is
generally
parallel to a bottom surface 96 of the support structure 22. The slits 80 and
82 are
generally triangularly shaped (Fig. 12) and resiliently open to receive the
wedges
76 and 78 by resiliently deforming the portions of the support structure 22
above
and below the slits 80 and 82.
The wedges 76 and 78, as shown in Figs. 10 and 11, fit into the slits 80 and
82 with the thin edge facing inwardly toward the center of the support
structure 22
and the relatively thick corner aligned with a corner of the support structure
22.
When the wedge 76 is inserted in the slit 80, the wedge 76 is flush with the
left
side 92 and rear side 90 of the support structure 22. Similarly, when the
wedge 78
is inserted in the slit 82, the wedge 78 is flush with the right side 94 and
the rear
side 90 of the support structure 22. The wedges 76 and 78 are retained in the
slits
80 and 82 frictionally or by the use of hook and loop fasteners 138 and 140
and
are also held in positioned by the cover 24.
The hook and loop fasteners 138 and 140 are preferably connected to the
interior of the slits 80 and 82 and to the wedges 76 and 78, as shown in Figs.
8
and 10-12. The slit includes a hook fastener 138 on one side and a loop
fastener
140 on the opposite side. In this configuration, the slits 80 and 82 are held
together and maintained against shear forces by the hook and loop fasteners
138
and 140 even when a wedge 76 and 78 is not inserted. The wedges 76 and 78
preferably have corresponding hook and loop fasteners 138 and 140 which align
with the hook and loop fasteners 138 and 140 of the slits 80 and 82 when the
wedges 76 and 78 are inserted.
The wedges 76 and 78 are preferably formed from a higher density or less
compressible foam material than the material used for the support structure
22.
The wedges 76 and 78 have a generally triangular shape in a plan view (Fig.
12)
and have one edge 98 is relatively thin and an opposite corner 100 from the
edge
is thicker than the other corners, preferably about Y2" to 1", although other
wedge
sizes can also be used. Inserting relatively larger wedges 76 and 78, or
inserting
more than one wedge 76 and 78 in a slit 80 and/or 82 causes relatively more
CA 02545963 2006-05-09
articulation of the support areas 42 and 44 than is accomplished with a
relatively
smaller wedge 76.
In addition to providing the capability of adjusting the support contour 26
symmetrically by inserting equally-sized wedges 76 into each of the slits 80
and 82,
the support contour 26 can also be adjusted asymmetrically, as shown in Fig.
13.
Asymmetric adjustment is where one corner of the support structure 22 is
articulated forward and inward more than the other corner of the support
structure
22. In some circumstances a user's anatomy can atrophy on one side more than
the other side. To accommodate this condition the support contour 26 can be
adjusted asymmetrically by inserting more wedges 76 and 78, or a larger wedge
76
and 78 into one side, than the other side. This has the effect of articulating
one of
the support areas 42 or 44 relatively more upward, forward and transversely
inward
than the other one of the support areas 42 or 44 to contact the user's anatomy
with
both support areas 42 and 44.
As shown in Fig. 9 and 10, the cover 24 includes an access zipper 104 to
provide access to the slits 80 and 82 to insert and remove the wedges 76 and
78
and for inserting and removing the support structure 22 from the cover 24. The
cover 24 has a continuous sidewall 112 which fits tightly along longitudinally-
extending right and left sides 92 and 94, and around transversely-extending
front
and rear sides 88 and 90 of the support structure 22. A top portion 108 of the
cover 24, as shown in Fig. 1, is positioned over the support contour 26. A
bottom
portion 110 of the cover 24 is positioned below the bottom surface 96 of the
support structure 22. The top and bottom portions 108 and 110 attach to the
sidewall 112 adjoining the longitudinally-extending right and left sides 92
and 94
and along the transversely-extending front and rear walls 88 and 90.
The access zipper 104 is connected between the bottom portion 110 of the
cover 24 and the continuous sidewall 112. When the cover 24 is on the support
structure 22, the zipper 104 extends from the rear of the longitudinally-
extending
left side 92 around the entire rear side 90 to the rear of the longitudinally-
extending
right side 94 of the support structure 22 (Fig. 1). The access zipper 104 also
includes a handle 106 for opening and closing the zipper 104.
16
CA 02545963 2006-05-09
The sidewall 112 of the cover 24 includes expansion portions 114 and 116
having an expansion capability at the rear corners 84 and 86 to accommodate
the
expanded vertical dimension at the corners 84 and 86 when the wedges 76 and 78
are inserted in the slits 80 and 82 in the corners of the support structure
22. The
expansion capability of the cover 24 allows the cover 24 to expand over the
corners 84 and 86 when the wedges 76 and 78 are inserted, as shown in Fig. 10.
In this way the cover 24 has the capability to enclose the support structure
22.
Left and right zippers 118 and 120 in the sidewall 112 are openable to
provide the expansion capability by increasing a vertical dimension of the
sidewall
112 at the corners 84 and 86. Gussets 122 and 124 are attached to the sidewall
112 adjacent to the upper teeth to the lower teeth of the zippers 118 and 120,
respectively, to limit the increase in vertical dimension of the sidewall 112
when the
zippers 118 and 120 are opened. The gussets 122 and 124 are folded into the
interior of the cover 24 when the zippers 118 and 120 are closed. The gussets
122
and 124 are preferably made from the same material as the sidewall 112.
The zipper 118 and the gusset 122 extend from the left side 92 of the
support structure 22 to the rear 90 of the support structure 22, and the
zipper 120
and the gusset 124 extend from the right side 94 of the support structure 22
to the
rear 90. The zippers 118 and 120 are conventional zippers that have pull
handles
106 which slide in one direction to close the zipper 118 and 120 by securing
the
teeth in an upper half of the zipper to the teeth in a lower half of the
zipper, and
slide in another direction to open the zipper 118 and 120 by separating the
teeth in
the upper half from the teeth in the lower half of the zipper 118 and 120.
The zippers 118 and 120 preferably end at a point near the transverse
center of the rear 90 of the support structure 22 so that a vertical dimension
of the
sidewall 112 at that location does not change regardless of whether the
zippers
118 and 120 are opened or closed. Positioning the zippers 118 and 120 in this
way ensures that the cover 24 remains taut in the transverse rear center of
the
support structure 22.
By keeping the cover 24 taut in the transverse rear center of the support
structure 22, support areas 42 and 44 are maintained in a lateral dimension
from
17
CA 02545963 2006-05-09
one another before and while the user is seated. The tautness of the cover 24
in
this area ensures that the insertion of the insertion members 76 and 78 into
the
slits 80 and 82 causes adjustment to the position of the support areas 42 and
44
rather than causing a change in the shape of the bottom surface 96.
The cover 24 helps the support structure 22 to maintain the position of the
support areas 42 and 44 by fitting taut over the support structure 22. The
sidewall
112 of the cover 24 fits tautly over the right and left sides 92 and 94 and
the front
and rear sides 88 and 90 of the support structure 22 to keep the front and
rear
sides of the support structure 22 from deforming away from one another. The
sidewall 112 of the cover 24, including the expandable portions 114 and 116,
fits
tautly over the rear side of the support structure 22 and holds that portion
of the
support structure 22 from deforming backwardly.
The top portion 108 of the cover 24 is preferably made of a conventional
spacer mesh material. The spacer mesh has a padding characteristic and is
breathable without permitting substantial stretching in either a longitudinal
or
transverse direction. The remaining bottom portion 110 of the cover 24 is
preferably made of a substantially non-stretchable nylon material that is also
breathable and which covers the seat support structure 22 other than the
support
contour 26. The sidewall 112 is also made of non-stretchable breathable nylon
material. Since the top, bottom and sidewall portions of the cover 24 are non-
stretchable, the cover 24 resists outward deflection of the sides 88, 90, 92
and 94
of the support structure 22. In this way the non-stretchable characteristic of
the
cover 24 assists in maintaining the shape of the support contour 26 even when
the
wheelchair user is seated on the cushion 20.
The support structure 22 has a bottom surface 28 with a generally convex
shape, as shown in Fig. 9, that curves slightly between the left and right
sides 92
and 94. The shape of the bottom surface 28 is a compromise between a flat or
planar shape that complements a flat seat support structure 126 (Fig. 10) of
some
types of wheelchairs and a generally downward convex shape with a larger curve
that complements a sling type seat support structure 128 (shown in Fig. 13) of
other types of wheelchairs.
18
CA 02545963 2006-05-09
When the cushion 20 is placed on a flat seat support structure 126 (Fig. 10)
the cushion 20 tends to flatten out to conform to the seat support structure
126,
and in doing so, the support areas 42 and 44 will generally move away from one
another. In order to compensate for this change in the support contour 26, the
wedges 76 and 78 may be inserted to move the support areas 42 and 44
relatively
closer to one another. On the other hand, when the cushion 20 is placed on a
sling type seat support structure 128, Fig. 13, the cushion 20 tends to assume
a
more curved shape to match the seat support structure 128. In this instance,
the
support areas 42 and 44 are articulated closer to one another by the
downwardly
convex curve of the cushion 20. Because of this articulation, the cushion 20
may
be utilized for some individuals without the addition of wedges 76.
The support structure 22 and the wedges 76 and 78 preferably have a
generally vertically aligned rear channels 102 that allow conventional upright
bars
(not shown) of the wheelchair to be positioned in the corners of the cushion
20.
The cover 24 fits over the rear channels 102 but allows the bars to push into
the
channels 102 when the cushion 20 is positioned on the wheelchair. Positioning
the
cushion 20 on the wheelchair in this way also has the effect of retaining the
wedges 76 positioned in the slits 80 and 82.
As described in the above-referenced U.S. patent application Serial No.
10/628,890, support and pressure relief characteristics of the support contour
26
can be determined and adjusted by the technique using an impression foam or
clearance measuring device 130. The clearance measuring device 130 allows a
therapist to determine whether the users bony prominences have adequate
clearance from the surface of the cushion 20. This provides the therapist with
information that is used to determine the degree of adjustment needed, if any,
to fit
the cushion 20 to a particular user.
The clearance measuring device 130, shown in Fig. 14, is used in
accordance with the present invention to measure the clearance between the
contacting portion of the individual's anatomy and the support contour 26 of
the
seat cushion 20 (Fig. 1). The clearance measuring device 130 comprises a pad
132 of collapsible impression foam confined within a clear flexible
envelope134.
19
CA 02545963 2006-05-09
The foam pad 132 generally has a longitudinal and transverse horizontal
dimensions (as shown in Fig. 14) which are sufficient to cover each of the
areas
28, 30 or 32 of the support contour 26 (Fig. 2) in which clearance is provided
to
offload pressure and shear forces from the anatomy in those areas. However,
the
longitudinal and transverse horizontal dimensions (as shown in Fig. 14) may
also
be sufficient to cover only a portion of one of the areas 28, 30 and 32 (Fig.
2). The
vertical thickness dimension (as shown in Fig. 14) of the foam pad 132 is
approximately the thickness necessary to achieve a desired degree of collapse
of
the impression foam, but not to fully collapse the impression foam, when the
The clearance measuring device 130 is used as shown generally in Figs.15-
16. The device 130 is placed at a desired location on the support contour 26
where a clearance is to be measured. In the case of the support contour 26
shown
in Fig. 2, the device would normally be placed to cover all or part of one of
the
The cushion 20 can be supplied to a therapist in a seat cushion adjusting kit
CA 02545963 2006-05-09
clearance measuring device 130 on the cushion 20 before seating the user on
the
cushion, the therapist is able to determine if the cushion 20, as it is
currently
configured, is suitable to provide proper postural alignment and pelvic
support for
the user. If the bony prominences of the seated user are too close to the
surface
of the support contour 26, or other conditions exist where the support contour
26 is
not configured correctly for the user, then the therapist can open the access
zipper
104 and insert one or more wedges 76 and/or 78 into one or both of the left or
right
slits 80 or 82 to adjust the position of the support areas 42 and/or 44 so
that more
support is provided by these areas to support the user.
The kit makes it possible for the therapist to stock only one cushion to fit a
variety of different users, which saves storage space and eliminates confusion
over
selecting one of many seating solutions. The adaptability of the cushion 20
provides the therapist with a broader range of applicability than is available
with
some other seating devices. The inclusion of the clearance measuring device
130
and the wedges 76 and 78 along with the cushion 20 provides that therapist
with
the necessary tools to adjust the cushion 20 to benefit users with a variety
of
anatomical configurations. The adjustable nature of the cushion 20 allows the
cushion 20 to be adjusted to fit the user over a period of time past when
conventional non-adjustable cushions must be replaced because of changed user
anatomical features or the onset of physical deterioration.
The cushion 20 is preferably less than two pounds in weight which is
believed to be half of the weight of any other cushion currently on the
market. The
reduced weight of the cushion 20 makes it an ideal candidate for self-
propelled
wheelchair where weight is an issue. The cushion 20 is also ideal for use by
wheelchair athletes because of the support given by the cushion 20 over a
range
of movements of the pelvic area 50 and because of the light weight of the
cushion
20.
The cover 24, as well as the support structure 22, are made of material that
allows air flow around the tissue of the user. This feature is important in
the
prevention of pressure ulcers since increased temperature and the retention of
moisture next to the skin can cause increased stress on the user's skin.
21
CA 02545963 2006-05-09
The cover 24 is also removable from the support structure 22 so that the
cover 24 can be washed in a conventional washing machine. The support contour
22 and the wedges 76 can be rinsed off with running water since the material
of
the support contour 22 and the wedges 76 do not absorb or retain water. The
washable nature of the cushion 20 is especially of benefit to a user who is
suffering
from problems with incontinence.
The cost of the cushion 20 to the user is relatively inexpensive in
comparison to some other cushions. This is due to the relatively inexpensive
nature of the materials used to manufacture the cushion 20 and the reduced
number of hours to produce the cushion 20 because of the simple yet elegant
design. Many other advantages and improvements will be apparent after gaining
a
full appreciation of the present invention.
A presently preferred embodiment of the present invention and many of its
improvements have been described with a degree of particularity. This
description
is a preferred example of implementing the invention, and is not necessarily
intended to limit the scope of the invention. The scope of the invention is
defined
by the following claims.
22
