Pelvic support method and means

A method and means for providing pelvic support to improve posture and relieve lower back pain is provided. The method comprises pressing a convex pillow against the region of the ilia, sacrum, and fifth lumbar vertebra to produce a substantial sacral base angle and to fully oppose any moment tending to cause rotational shifting of the pelvis. Another way to define the invention is a back pillow which may be used in a chair having a seat member, wherein the back pillow includes a convexly shaped support pillow for maintaining the pelvis of the user at a sufficient sacral base angle that substantially the entire weight of the upper portion of the user's body is supported by the seat member. The invention may alternatively be described as a chair comprising a substantially horizontal convex seat for supporting the ischial tuberosities of the occupant in the vicinity of the apex thereof, and a substantially vertical, generally convex support means for supporting the posterior portion of the occupant's pelvis at a sacral base angle of from between 25 and 45 degrees, and so that a gravitational line drawn downwardly from the center of L-3 intersects the anterior one-third of the sacral base.

BACKGROUND AND SUMMARY OF THE INVENTION 
This invention relates to a method and means for providing pelvic support 
to improve posture and relieve lower back pain. 
Most so-called secretarial or working chairs include a substantially 
horizontal seat member and a substantially vertical back support member. 
This back support member is typically positioned substantially above the 
seat member, and is adapted to provide support to the small of the back or 
lumbar region of the occupant's spinal column. The typical lumbar support 
chair does not, however, support the pelvis of the occupant. Thus, as will 
be described in detail hereafter, the occupant's pelvis is permitted to 
shift posteriorly and inferiorly until the coccyx or tailbone contacts the 
seat of the chair. In order to counteract or prevent this shifting of the 
pelvis, the occupant must utilize muscles which are not intended for this 
purpose. The use of such muscles over an extended period results in 
fatigue and pain. It can also result in discomfort and damage to the 
lumbar vertebrae and the ligaments and tendons associated with such 
vertebrae, as will be described in detail below. 
Thus, the present invention has as its objects any one or more of the 
following, either taken individually or in combination with one another: 
(1) To provide a method and means for supporting the pelvis in order to 
promote proper posture and relieve lower back pain; 
(2) To provide a secretarial or working chair which will provide comfort to 
the occupant even after extended periods of use; 
(3) To provide pelvic support without the use of extraneous means which 
might restrict circulation of blood and/or lymphatic fluids to the lower 
extremities or result in discomfort to the occupant; 
(4) To provide a pelvic support chair having a seat which is high enough 
from the floor that the femur heads of the occupant are inclined at a 
slightly downward angle when the occupant's feet are resting flat on the 
floor, thus not only promoting circulation to the lower extremities but 
also relaxing the hamstring muscles of the occupant; 
(5) To provide a chair in which the ischial tuberosities of the occupant 
are positioned proximal the uppermost portion or apex of the seat pillow; 
(6) To provide a back pillow which may be used either with a conventional 
chair or as a supine support to produce a substantial sacral base angle in 
the pelvis of the user and to fully oppose any moment tending to cause 
rotational shifting of the pelvis. 
(7) To provide a combination of a seat pillow and back pillow which can be 
mounted to a conventional chair to provide appropriate pelvic support; and 
(8) To develop a chair which permits the occupant to achieve ligamentous 
posture, thereby reducing the amount of muscular and neurological exertion 
necessary to remain in an erect posture, and providing greater muscular 
control, tone, and strength for other activities undertaken while sitting 
in the chair; stated differently, this object is to keep the muscles of 
the body intact as determined by standard muscular tests. 
This invention responds to the problems presented in the prior art by 
providing a back pillow for use in a chair having a generally horizontal 
seat member, wherein the back pillow includes convexly shaped support 
means for maintaining the pelvis of the user at a sufficient sacral base 
angle that substantially the entire weight of the upper portion of the 
body of the user is supported by the chair seat member. The term "pillow" 
is used herein not in the sense of a soft bed pillow, but in the sense of 
a common dictionary definition: "a block or support used especially to 
equalize or distribute pressure." The phrase "substantially the entire 
weight" is intended to distinguish those prior art designs which include a 
rearwardly tilting back adapted to support a certain portion of the weight 
of the occupant. Rather, it is intended to define a chair or a pillow to 
be used with a chair in which the pillow or chair back provides support 
primarily in a horizontal direction. The "upper portion of the body" is 
intended to define the pelvis and everything thereabove. 
The invention may alternatively be described as a chair comprising a 
substantially horizontal, generally convex seat means for supporting the 
ischial tuberosities of the occupant in the vicinity of the apex thereof, 
in combination with substantially vertical, generally convex support means 
for supporting the posterior portion of the occupant's pelvis at a sacral 
base angle of from between 25 and 45 degrees, and so that a gravitational 
line drawn downwardly from the center of L-3 intersects the anterior 
one-third of the sacral base. Yet another way to describe the invention is 
the combination of seat and back pillows for use in a chair having a 
substantially horizontal seat member and a substantially vertical back 
member, wherein the seat pillow includes means for mounting the seat 
pillow to the seat member and has an upper surface with an apex, and 
wherein the back pillow includes means for mounting the back pillow to the 
back member and has means for supporting the pelvis of the occupant in a 
position such that a gravitational line drawn downwardly from the center 
of L-3 intersects the anterior one-third of the sacral base.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The principles of this invention are particularly useful when embodied in a 
pelvic support chair such as that illustrated in FIGS. 1-3, generally 
indicated by the numeral 10. FIGS. 2-4 (and to some extent FIG. 5) 
schematically depict the pertinent skeletal components in phantom. The 
lumbar vertebrae are commonly designated L-1 through L-5, and are 
identified as such in the drawings. It can be seen that these vertebrae, 
along with those ligaments and tendons which hold them in place, define a 
forwardly convex curve. The sacrum S, in combination with the coccyx C, 
define a rearwardly convex curve positioned immediately below the lumbar 
curve. The sacrum S is centrally mounted to the ilia I by ligaments which 
provide a limited amount of movement therebetween. The so-called 
lumbosacral interspace (identified with the letters LSI) comprises the gap 
between the sacrum S and L-5. The relative movement between the sacrum S 
and L-5 at the lumbosacral interspace LSI is critical since the 
lumbosacral interspace LSI normally accounts for an estimated 75% of all 
lumbar flexion. Thus, unless support is provided to the pelvis, the 
inherent structural weakness of the spine produces the greatest kinetic 
strain potential at the lumbosacral interspace LSI. 
The ilia I are sometimes referred to as the pelvic bone, although the term 
"pelvis" as used herein (designated with the letter P) is intended to 
define the region of the body which encompasses the ilia I and the sacrum 
S. The two laterally spaced, downwardly extending points at the bottom of 
the ilia I are termed the ischial tuberosities, and are designated with 
the letters IT. The importance of the position of the ischial tuberosities 
IT in the chair 10 vis-a-vis prior art chairs will become evident as this 
discussion continues. 
In defining the position of the sacrum S, as well as the other elements of 
the pelvis P, the term "sacral base angle" will be utilized herein. This 
angle is defined between a line drawn across the superior base of the 
sacrum S, and the horizontal, as depicted in FIGS. 3 and 4 and identified 
with the letters SBA. A gravitational line GL drawn from the center of L-3 
is also helpful to identify the position of the components of the pelvis. 
For this reason, line GL is shown in FIGS. 3 and 4. 
FIG. 4 depicts the position of the pertinent skeletal components of a 
person sitting in a conventional lumbar-support chair. It can be seen that 
the back pillow in this chair merely provides support to the lumbar 
vertebrae and not to the pelvis P. The weight of the upper body on the 
posterior portions of the ilia I results in rotational shifting of the 
ilia I at the lumbosacral interspace LSI until the coccyx C of the person 
comes into contact with the seat pillow. As the pelvis P tilts posteriorly 
and inferiorly the sacral base angle SBA gets smaller. In the chair 
depicted in FIG. 4 the sacral base angle SBA is 3 degrees. At the same 
time, the gravitational line GL from L-3 moves posteriorly, increasing the 
moment on the ilia I. This rotation, which is in a counterclockwise 
direction as depicted in FIG. 4, causes a spastic flattening of the lumbar 
curve despite the presence of the back pillow. This, in turn, brings about 
alteration of the thoracic and cervical curves which further stresses the 
spinal musculature creating more fatigue and spasms. It also results in 
unlocking of the ligamentous joints of the spine and pelvis, thus causing 
stress to pelvic muscles which the person may utilize in an attempt to 
keep the pelvis in the proper position. This protracted muscular stress 
results in discomfort and strain due to fatigue. Additionally, irritation 
can arise from prolonged muscle spasms and, in the presence of disc 
degeneration among those persons with back problems, the spasms can 
constitute significant compressive force which can result in aberrant 
neuronal, vascular and lymphatic alteration. The effect of fatigue on 
concentration and productivity in the worker is obviously dramatic. 
The need to support the pelvis is increased as the distance from the floor 
to the seat is decreased as is the case with automobile seats, deep sofas, 
and small school seat-desks where the legs of the occupant are extended. 
As the hamstrings elongate, they pull on the pelvis, thus exerting 
additional force, compounding the insult to the ligamentous and muscular 
support structures. 
One attempt to avoid the aforedescribed problems with conventional lumbar 
support chairs is described in West German Pat. No. 1,273,761 issued to 
Ackermann. FIG. 5 is a copy of a drawing included in Ackermann's patent. 
In this patent Ackermann discloses a chair having a lumbar support cushion 
which extends downwardly sufficiently far to contact the posterior of the 
ilia. While Ackermann's drawing is not anatomically correct, it is clear 
that the back of his chair is rearwardly inclined so that the head of the 
occupant is substantially posterior of his or her pelvis. This results in 
a moment being applied about the pelvis. To prevent anterior slippage of 
the ischial tuberosities as a result of this moment, Ackermann utilizes a 
raised cushion positioned anteriorly of the ischial tuberosities. This 
raised cushion exerts a posterior force on the ischial tuberosities in the 
direction of the arrow, thereby locking them in place. 
While Ackermann recognized the related problems of rotational shifting of 
the pelvis and restriction on circulation to the lower extremities, he 
went about solving these problems in the wrong way. In order for his 
raised cushion to be of any assistance in holding the ischial tuberosities 
in place, it must be of substantial size. However, this would inherently 
result in localized pressure on the posterior surface of the thighs, 
thereby restricting circulation of blood and lymphatic fluids to the lower 
extremities. If the raised cushion is reduced in size to promote 
circulation, it would be too small to provide support to the ischial 
tuberosities. 
A second drawing in the Ackermann patent discloses the use of firm plates 
covered with soft padding which is compressed by the weight of the pelvic 
bones. For this reason, the pelvis of the occupant could not be supported 
by the padding. 
A Swiss patent to Garrett discloses a backrest having adjustable back 
support means. However, this patent is even less pertinent than the 
Ackermann German patent. 
The present invention overcomes these problems by providing a chair 10 
comprised essentially of a substantially horizontal seat pillow 12 and a 
substantially vertical back pillow 14. Both seat and back pillows 12 and 
14 are of generally convex configuration. The term "convex" as used herein 
is intended to define any outwardly curved surface. The surface need not 
be symmetrical in any way. The pillows 12 and 14 of chair 10 are 
preferably made up of resilient material having substantially the same 
degree of firmness. This firmness is ordinarily in the range of 70-80 ILD. 
An 80 ILD pillow, for example, exhibits a one inch deflection under an 80 
pound load applied over a one square foot area. This, incidentally, is a 
far greater firmness value than most conventional chair pillows. 
Seat pillow 12 is relatively short in length and is downwardly sloping 
toward the front in order to force the occupant to sit back into chair 10 
so that the ischial tuberosities IT are positioned proximal the apex 12a 
of the convexly curved seat pillow. A person sitting in this or any other 
chair cannot slouch unless the posterior portion of the pelvis P first 
shifts posteriorly and inferiorly. This pelvic movement is possible in the 
conventional lumbar support chair, but is not possible in chair 10 because 
the back pillow 14 contacts the posterior of pelvis P, thereby supporting 
same. For this reason, back pillow 14 is sometimes referred to as pelvic 
support means. More precisely, it can be seen that the apex 14a of the 
convexly curved back pillow 14 contacts the ilia I, the sacrum S, and in 
some instances, L-5. The word "contacts" as used herein, of course, merely 
means that back pillow 14 touches the skin and the fleshy portions of the 
body immediately behind the ilia I, sacrum S, and L-5. Thus, the only way 
for the pelvis P to shift to a slouching position is for the ischial 
tuberosities IT to slide anteriorly and inferiorly down the seat pillow 
12. However, due to the short down-sloping configuration of seat pillow 
12, such movement of the ischial tuberosities IT would tend to cause the 
occupant to actually slide out of the chair 10. Thus, by inducing the 
occupant to sit all the way back with the ischial tuberosities proximal 
apex 12a, rotational shifting of the pelvis P and the slouching made 
possible by such movement of the pelvis P is effectively discouraged. 
The fact that the seat pillow 12 is short and downwardly sloping also 
serves to reduce any possible restriction upon circulation to the lower 
extremities, not only due to the lack of any members which would cause 
localized pressure points on the posterior surfaces of the thighs, but 
also because the femur heads F are slightly downwardly inclined. In order 
to provide for this downward inclination, the height of the seat pillow 12 
above the floor 16 should be adjusted properly, as will be described 
hereafter. 
In the depicted preferred embodiment, the thickness of back pillow 14 
increases toward its bottom edge. Another way to describe this 
configuration is to say that the apex 14a of the convex curvature of back 
pillow 14 is positioned below the transverse centerline thereof. It should 
be appreciated, however, that various configurations in back pillow 14 may 
be utilized, as long as the proper support is provided to the pelvis P of 
the user. 
It can be seen that back pillow 14 supports the pelvis P in a generally 
upright position, which results in a sacral base angle SBA of from between 
25 to 45 degrees. This approximates the sacral base angle SBA when an 
average person is in an erect, physiologic, standing position. In the 
depicted embodiment, the sacral base angle SBA equals 27 degrees, which is 
within the normal range of ligamentous posture. The term "ligamentous" as 
it relates to posture is used herein to mean that physiologic posture 
which permits the joints of the body to rely upon their surrounding 
ligaments for support, requiring only intermittent, minor muscular 
contractions triggered by the reflexes of the joints and ligaments; that 
is, substantial, continuous muscular effort is not required when 
ligamentous posture has been achieved. 
The gravitational line from L-3 provides a second, and perhaps an even 
better, indication of whether ligamentous posture has been achieved. A 
close study of FIG. 3 reveals that the gravitational line GL from L-3 
intersects the anterior one-third of the sacral base. When this occurs, 
the pelvis P is in a ligamentous position. When line GL does not intersect 
the anterior one-third of the sacral base, such as in the prior art design 
of FIG. 4, then unlocking of the ligamentous joints results, and muscular 
effort is necessitated. 
With the pelvis P supported in the depicted physiologic position, the 
lumbosacral interspace LSI is firmly held in position, thereby limiting 
the amount of movement between the sacrum S and L-5. This is an important 
feature of the invention, because, as mentioned above, the lumbosacral 
interspace LSI accounts for as much as 75% of all lumbar flexion. In this 
physiologic pelvic position, the spine is also physiologic, erect and 
static, requiring minimum muscular effort on the part of the occupant of 
the chair. It should be appreciated that this low degree of muscular 
effort is made possible because physiologic erect balance is essentially a 
ligamentous function. Such ligamentous posture is, as mentioned above, 
effortless and therefore non-fatiguing. This feature of the invention 
would clearly be of great importance to persons in sedentary occupations 
who spend long hours or perhaps the entire work day in a chair. 
As shown in FIG. 2, back pillow 14 is mounted to seat pillow 12 by support 
member 18 which extends therebetween. As depicted, this typically 
positions back pillow 14 posteriorly of the apex 12a of seat pillow 12. It 
may be desirable to certain applications that there be a certain amount of 
flexion between back pillow 14 and seat pillow 12. For this purpose, the 
chair 10 includes a first control knob 20 which, through appropriate 
springs and linkages, controls the degree of flexion between support 
member 18 and seat pillow 12 mounted thereto. Normally, it is desirable 
that only a limited amount of flexion be provided in order to ensure 
proper and sufficient pelvic support. A second control knob 22 may also be 
provided adjacent the sub-frame 32 of chair 10 in order to provide for 
vertical adjustability of support member 18 and back pillow 14 carried 
thereby. Again, only a limited amount of adjustability need be provided, 
since the anatomical differences in the heights of the pelvises of various 
persons is not that substantial. A third control knob 23 is normally also 
provided, mounted adjacent sub-frame 32 to permit support member 18 and 
back pillow 14 mounted thereto to be adjusted posteriorly and anteriorly 
to accommodate persons of widely varying weight and build. Since all three 
of these adjustability features are of conventional design, they have not 
been depicted in detail, nor will they be described furthur. 
The base of the depicted chair 10 includes a plurality of evenly spaced, 
radially extending support spokes 24 having wheels 26 mounted at the ends 
thereof. These support spokes 24 are mounted to a centrally disposed post 
28. A height-adjustment member 30 extends upwardly from post 28 to the 
sub-frame 32 of seat pillow 12. This height-adjustment member 30 is 
threaded into post 28 so that by rotating seat pillow 12 with respect to 
post 28 and support spokes 24, the height of seat pillow 12 with respect 
to the floor 16 may be varied. As mentioned above, the adjustability of 
the height of seat pillow 12 with respect to the floor 16 is desirable in 
order to permit the chair 10 to be specifically adjusted to the individual 
occupant. When the occupant is in the chair, his or her feet should be 
permitted to rest flat on the floor 16. With the feet in this position, 
femur heads F should be in a slightly downwardly inclined position, as 
shown in FIG. 2. With the occupant positioned thusly, the ischial 
tuberosities IT rest proximal the apex 12a of seat pillow 12 which is 
substantially centered over post 28. 
The position of the pelvis P may be described in another way if reference 
is made to FIG. 3. This figure shows that the gravitational line GL drawn 
from L-3 intersects seat pillow 12 immediately to the posterior, but still 
in the general vicinity of the apex 12a thereof. Under some conditions it 
may be desirable to provide a substantially horizontal apex plane (not 
shown) extending immediately posteriorly of the depicted apex 12a. With 
this configuration of seat pillow, line GL would intersect this apex 
plane. 
The stability of the depicted chair is ensured by the fact that, first, L-3 
and the upper portion of the body generally are positioned substantially 
over apex 12a, and, second, apex 12a is centrally disposed over post 28. 
This stability is enhanced by the fact that there is tripod support 
between the chair and the two feet of the occupant. Moreover, since the 
feet are resting on the floor, thus carrying the weight of the lower 
extremities, there is virtually no restriction of circulation to the lower 
extremities which could result if the feet where held in an elevated 
position by seat pillow 12. This manner of positioning the occupant in a 
tripod fashion has the additional advantage of making it extremely easy 
for the occupant to get up out of the chair. While in the chair, the 
occupant has great mobility since the feet may be easily utilized to swing 
the chair 10 around in a circle, or to roll it across the floor 16. 
In view of the broad definition of "pillow" used herein, it is clear that 
the principles of the invention may also be applied to rigid chairs and 
seats, such as folding chairs, school seats, vehicle seats, church pews, 
and auditorium and stadium seats. 
Under certain conditions, it may be desirable to provide a removable back 
pillow (not shown) which could be adapted to be positioned on a 
conventional chair. Like the depicted back pillow 14, this removable 
pillow would usually be convexly shaped in order to maintain the pelvis of 
the user at a sufficient sacral base angle that substantially the entire 
weight of the upper portion of the user's body is supported by the chair 
seat member. Stated another way, the removable back pillow may be said to 
include support means for producing a substantial sacral base angle in the 
pelvis of the user, and to fully oppose any moment tending to cause 
rotational shifting of the pelvis. The term "substantial sacral base 
angle" is intended to cover an angle of at least 25 degrees. 
This removable pillow may also be placed in the appropriate position under 
a person's back when that person is in the supine position, thus 
encouraging a ligamentous pelvic position and lumbar curvature. Without 
such support, the pelvis has a tendency to shift rotationally in a 
posterior direction, carrying with it the lumbar vertebrae, much as 
described above. 
Of course, it should be understood that various changes and modifications 
of the preferred embodiments described herein will be apparent to those 
skilled in the art. Such changes and modifications can be made without 
departing from the spirit and scope of the present invention and without 
diminishing its attended advantages. It is, therefore, intended that such 
changes and modifications be covered by the following claims.