Note: Descriptions are shown in the official language in which they were submitted.
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ORTHOPEDIC EXERCISER
FIELD OF THE INVENTION
The present invention relates to orthopedic exerciser for therapy, post-
surgery rehabilitation or healing of a knee or the muscles of a leg.
BACKGROUND OF THE INVENTION
Various surgical techniques have been known since the early 80's for the
treatment of articular disorders. The complete replacement of an
articulation of the knee is commonly practised nowadays. Rehabilitation of
operated knees has become needy and different new options have been
developed.
Several exercises have been proposed in different rehabilitation programs.
They all aim to recover the knee to the normal articular mobility to
disappearance of pain, to functional proprioception and to normal muscular
function.
Currently there are four main type of exercises to aid in the rehabilitation
of
the knee, namely, passive, active assisted, active and "against resistance".
The condition of the patient may determine the type of exercise to be
practised. Traditionally, passive movement is used to allow a gain of
amplitude in the articular movement by diminishing inflammatory reactions,
pain or muscular cramps. The exercises requiring active muscular
movement usually follow after disappearance of the pain.
A CPM (Continuous Passive Motion) apparatus is a commonly used
apparatus in knee rehabilitation. This apparatus allows execution of passive
flexion and extension movement during a long period of time and without
effort from the patient. CPM may be very efficient in terms of reducing pain
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in the knee, or leg in post-surgery rehabilitation treatment, reducing
hospitalization time and reducing a number of complications that may occur
during the rehabilitation period. However, CPM does not replace functional
activity and active movement.
Once the patient is able to execute contraction of muscles without
excessive pain, which may be very soon, active assisted movement of the
leg is practised. It is then possible to gain range of movement (ROM)
without any motorised assistance. In our experience, simple mechanical
assistance in either flexion or extension movement allows greater benefits
than a motorised device. Assistive active devices are necessary when
muscles are not functional enough to move the joint in the devised range.
The next step to undertake for allowing full recovery of the knee or leg, that
is for allowing their proper functioning, is to execute "against resistance"
exercises. Actually, this type of exercise allows restoration of
proprioceptive
neuromuscular facilitation. It is known that rehabilitation of a muscle and
maintenance of development of the muscle tone is possible from the
different reflex mechanisms generated by stretching of the muscle which
results from the physical action of the muscle itself.
Different publications and patents disclose an apparatus allowing
application of resistance during extension of the knee through a movement
of an arc of a circle. The thigh is maintained still or partially still,
whether the
patient is sitting or lying down. Other apparatuses comprise a simple
support for receiving a thigh and a resistance device which may be a bag of
sand attached to the foot. In other instances, the resistance device may be
an elastic band. In all cases, the foot usually lacks proper support and the
resistance is exercised on the wrong portion of the leg, for instance, in the
lower portion, i.e. the shank. All these apparatus challenge the muscles in a
wrong bio-mechanical way, and may damage the knee. These old-
fashioned exercises are so called "open circuit" type.
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Obviously, it is important to provide an apparatus that will allow execution
of
the exercise without causing tension on the knee. Recent data have shown
the best benefits of a new approach.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an apparatus allowing
execution of a wide range of exercises of a leg without causing excessive
tension on the knee.
It is a further object of the present invention to provide an apparatus
allowing execution of a complete combination of exercise that will result in
the complete recovery of the joint of exercises, performed in a normal
functional way, by applying resistance or assistance on the plantar part of
the foot. These exercises are called "closed circuit exercises", or "closed
kinetic chain" exercises. They challenge muscles and articulation in the
proper bio-mechanical way. One important feature of the apparatus
according to the invention lies in the use of the same mechanical device i.e.
a pair of pistons, to either assist active still movement, to gain range or
resist active movement to gain strength, in opposite directions of course,
but in both flexion and extension.
The apparatus according to the present invention comprises a main frame,
and a leg support member slidably mounted on the main frame. The
support member comprises a first portion designed to receive a thigh, a
second portion designed to receive a shank and a third portion designed to
receive a foot. The first and second portions each comprise two opposite
side edges defining the width of the support member. The first and second
portions are pivotably connected to each other and form a first rotation axis
for allowing flexion of a knee about a second rotational axis. The apparatus
is characterized in that it comprises:
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-a dynamic adjustment mechanism for minimizing tension on the
knee during extension or flexion of the leg, said mechanism allowing no
eccentricity between the first and second rotational axes.
The first and second portions are pivotally connected so that when the leg
is flexed and extended, the first and second axes are substantially
coincident throughout the range of motion.
As mentioned above, one advantage of having such a dynamic adjustment
mechanism is to allow proper resistive or assistive exercise of the leg
without running the risk of further injuring the knee.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1, is a front view of the orthopedic apparatus according to a
preferred embodiment of the present invention.
Figure 2, is a rear view of the orthopedic apparatus of Figure 1.
Figure 3 is a side view of the orthopedic apparatus of Figure 1.
Figure 4 is a top view of the orthopedic apparatus of Figure 1.
Figure 5 is a perspective view from the back of the orthopedic apparatus of
Figure 1.
Figure 6 is a perspective view from the front of the orthopedic apparatus of
Figure 1.
Figure 7 is an exploded view of a dynamic adjustment mechanism
according to a preferred embodiment of the orthopedic apparatus of the
present invention.
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Figure 8 is a longitudinal section view of a static adjustment mechanism
according to a preferred embodiment of the orthopedic apparatus of the
present invention.
Figure 9 is a side view of a blocking mechanism according to a preferred
5 embodiment of the orthopedic apparatus of the present invention at a
blocking position for the extension movement.
Figure 10 is a side view of the blocking mechanism of Figure 9 at a
complete blocking position.
Figure 11 is a side view of the blocking mechanism of Figure 9 at a blocking
position for the flexion movement.
Figure 12 is a side view of the blocking mechanism of Figure 9 at a
disengaged position.
Figures 13a, b, c and d are schematic representations of the alignment
between the first and second axes of rotation throughout the range of
motion for legs of different lengths.
DETAILED DESCRIPTION OF THE INVENTION
As can be seen in Figures 1 to 6, the orthopedic apparatus (10) according
to the present invention comprises a main frame (12) which has a pair of
rails (16) . The main frame is designed to receive a leg support member
(14). The leg support member (14) has two opposite ends, one of which is
fixedly secured to an end on the leg support member (14), the other
opposite end being slidably secured on the rails (16) of the main frame (12).
The leg support member (14) can be divided into three portions. A first
portion (18) is designed to receive a thigh, a second portion (20) is adapted
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to receive a shank and a third portion (22) adapted to receive a foot, so as
to furnish a proper support for the whole leg. The first and second portions
(18, 20) are pivotally connected about a second rotational axis so to allow
flexion and extension of the leg about a first rotational axis.
The width of the leg support member (14) is defined by two opposite side
edges (24, 26).
The orthopedic apparatus (10) comprises a dynamic adjustment
mechanism, shown on Figure 7 for minimizing tension on the knee during
extension and flexion of the leg. The dynamic adjustment mechanism allow
tension-free movement of the knee by always maintaining the eccentricity
between the rotational angle of the leg support member (14) and the knee
nil. The dynamic adjustment mechanism may be any mechanism that yields
such result. One of the main purposes of the dynamic adjustment
mechanism is to prevent for a slight friction between the leg and the
apparatus during flexion and extension, due mostly to the accumulation of
flesh directly under the knee, and due partly to an additional movement of
rotation and translation of the shank with respect to the thigh.
In a preferred embodiment, the dynamic adjustment mechanism consists of
an indented hinge (28).
The indented hinge (28) is designed to allow a dynamic adjustment of the
leg in length during movement of same, that is during flexion and extension.
The rotational axis of the indented hinge (28) follows the rotational axis of
the knee so to minimize the eccentricity between the leg and the hinge (28).
The indented hinge (28) pivotally connects the first and second portions
(18, 20) of the leg support member (14) so that when the first and second
portions (18, 20) are brought up to form a horizontal plane, the rotational
axis of the hinge (28) is protruding from the plane. This result in that when
the leg is at the extended or flexed position, the rotational axis of the
hinge
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(28) and that of the leg coincide. In other words, the proposed mechanism
follows closely the actual movement of the rotational axis of the knee either
during extension or flexion of the leg, resulting in almost complete absence
of friction between the leg of the patient and the portions of the leg support
member (14) all the while keeping the leg of the patient uniformly and
properly supported on the leg support member (14).
Hence, the main purpose of a dynamic adjustment mechanism is to provide
a hinge (28) having a rotational axis adjacent to the one of the leg so that
the eccentricity between the knee and hinge is insignificant, thereby
significantly reducing the tension that may be applied on the knee during
the movement of the leg. The hinge is different from prior art machines in
that its axis of rotation, when the leg is flexed, coincides with the axis of
rotation of the knee throughout the range of motion, as best seen in Figs.
13a, b, c and d. In these figures, the intersections of the dashed lines
corresponds to the instantaneous center of rotation of the indented hinge,
whereas the intersection of the full lines corresponds to the instantaneous
center of rotation of the knee of a patient. The distance between the two
points is minimal, so that the first and second axes of rotation are
substantially coincident throughout the range of motion, for legs of various
lengths. One should note that the lengths stated in Figs. 13a, b, c, d are:
for
the thigh, the distance between the pubic area (lower part) and the knee,
and for the shank, the distance between the knee and the bottom of the
heel. One will note a slight degradation when at maximal flexion, which is
due to mechanical constraints. Consequently, the apparatus according to
the present invention follows very closely the real movement of the knee
during flexion and extension, and results in very little friction between the
legs of a patient and the apparatus, with constant and uniform contact of
the heel on the third portion (22) of the apparatus. One will also note that
the figures show an unrealistic movement below the plane of the apparatus,
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and these are included in the figures as the representations are based on
mathematical modelling.
The orthopedic apparatus also preferably comprises a resistance
mechanism best seen on Figures 3, 5 and 6 for allowing the execution of
resistive movement of the leg. More precisely, this mechanism allows the
adjustment of different degrees of tension during extension and flexion of
the leg. The resistance mechanism consists of a pair of pistons (30). Each
piston (30) has an end connected to a portion of the side edge (24) of the
leg support member (14) and an opposite end connected to a portion of the
main frame (12). The best feature of this mechanism is to offer a linear type
resistance during the complete range of movement, which is constant and
unvariable like body weight in functional activity.
A blocking mechanism may also be provided for allowing instant pause of
the extension and flexion of the leg and prevent reversal of movement
direction when desired. The blocking mechanism comprises a ratchet wheel
(30) and a rack (32). The ratchet (30) further comprises a first and second
lever (34, 36). This system allows instant pause at different position of the
leg.
As shown in Figure 9, for blocking the extension of the leg, the left lever
(36) is disengaged, the right lever (34) is engaged.
As shown in Figure 10, for a complete block of the movement (extension or
flexion), the ratchet wheel (30) is turned anticlockwise so that both levers
(34, 36) are engaged in the rack (32).
When the ratchet wheel (30) is further rotated anticlockwise, the blocking
mechanism attains a third position shown in Figure 11. This is the blocking
position for the flexion movement. At this position, the left lever (36)
remains engaged in the rack and the right lever (34) is disengaged.
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Still turning anticlockwise, the right lever (34) tip over the left lever (36)
thereby disengaging it from the rack (32). This position is the free position
and is shown in Figure 12.
As shown in Figure 8, the orthopedic apparatus (10) may further be
provided with a static adjustment mechanism for adjusting the first and
second portions (18, 20) of the leg support member (14) to a
predetermined length. The static adjustment mechanism may consist of a
spring-knob (38, 40) on an internal tube (42) and a plurality of holes (46) at
the corresponding end of the side edges (24, 26) of the first and second
portions (18, 20). Hence to adjust the length of the exerciser (10), the user
simply needs to push in the knob (38) downwards and pull the internal tube
(42) in or out of the external tube (44) to the hole (46) corresponding to the
desired position/length. Accordingly, the first and second portions 18, 20
are further provided with means 19, 21 (see Figs. 3 and 4) to allow for this
variation in length while all the same supporting the leg properly.
Another feature of the apparatus according to the invention is that it may
include stoppers 51, 52 within each of the rails. These stoppers can be
used to limit the range of motion of the leg during flexion and extension, so
that the leg, instead of rotating between approximately 0° to
180°, can be
made to rotate within a smaller range by bringing the stoppers closer
together, either independently or together. As shown in Fig. 3, stopper 51
limits flexion and stopper 52 limits extension. The stoppers can be any type
of mechanism which can be locked into place at the desired position along
the rail, so that the stopper effectively stops the motion of the second and
third portions of the apparatus along the rails and does not translate once it
has been fixed in a predetermined position.
Preferably, stoppers 51 (one in each rail) and stoppers 52 (one in each rail)
are moved simultaneously. To that effect, stoppers 51 could be
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mechanically connected together, and stoppers 52 could be mechanically
connected together.
As can be appreciated, the orthopedic apparatus (10) according to the
present invention provides a compact and portable exerciser that is easy to
5 andle. This apparatus is as complete as going to a gymnasium. It allows
the execution of a wide range of exercise in the comfort of the bed.
Furthermore, it is easily adjustable to the patient's proportion, i.e.
different
patients will have thighs and shanks of different lengths. It is easy to use
since all the functions are integrated in the apparatus and do not require
10 additional assistance from a nurse or a helper.
Hence, the present apparatus is complete since it incorporates all the
physiological principles that allow fast recovery of the knee without adding
stress to the same. Specifically, the first and second axes of rotation are
substantially coincident throughout the range of motion. Furthermore, the
apparatus according to the invention allows the use of the same
mechanical device (i.e. the pistons 30) to either assist active movement to
gain range or to resist active movement to gain strength.
Although the present invention has been explained hereinabove by way of
a preferred embodiment thereof, it should be pointed out that any
modifications to this preferred embodiment within the scope of the present
description is not deemed to alter or change the nature and scope of the
present invention.
