Note: Descriptions are shown in the official language in which they were submitted.
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CONTINUOUS PASSIVE MOTION DEVICES FOR JOINTS
FIELD OF THE INVENTION
The present invention relates to continuous passive motion
devices for therapeutic exercise of joints, and more particularly, the
invention
relates to continuous passive motion devices for wrist and ankle joint
therapy.
BACKGROUND OF THE INVENTION
In recent years it has become evident that the rehabilitation and
treatment of injured joints can be expedited by use of continuous passive
motion (CPM) of the joint. Continuous passive motion entails inducing
movement of certain limb portions without requiring muscle coordination or
control by the patient. Numerous studies have shown the CPM of the different
joints accelerates healing or recovery time, promotes healing and very
importantly results in a fuller range of motion of the joint at the end of the
course of therapy. Therefore, the rehabilitation of joints through continuous
passive motion therapy has become an important method of treating joint
injuries.
There are several known types of devices or machines for
exercising wrist, ankle and elbow joints. United States Patent No. 4,538,595
discloses several passive exercise devices for ankle, wrist and elbow joints.
Figures 1 to 4 illustrate the wrist exercising embodiment comprising an
actuator
attached to a forearm brace assembly. An actuator arm extends from the
actuator to a hand brace and in operation the hand undergoes extension/flexion
movement. An embodiment for exercising the elbow joint is shown in Figures
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18-19 and Figure 24 shows a circumferential track used for adjusting the angle
of the forearm and hand relative to the longitudinal axis of the upper arm
during
movement of the elbow joint. The ankle exercising device is shown in Figures
8 to 11 wherein the actuator is attached to the upper leg brace and the
actuator
rod is attached to the foot support to provide dorsal flexion/extension. The
radial position of the foot relative to the longitudinal axis of the lower leg
can
be adjusted as shown in Figure 11.
United States Patent No. 4,650,183 discloses an exercise
apparatus for foot and ankle joints. This device is used for exercise
applications
and to evaluate pertormance of the ankle joint. The device comprises a bench
for the user to sit on during use, a pivotally mounted foot pedal and
hydraulic
cylinders attached to the foot pedal to provide resistance.
United States Patent No. 5,067,479 discloses a CPM device for
therapy of the wrist joint. The device comprises a telescopic rod slidably
movable in a tubular shaft which is pivotally mounted to a base. One end of
the
shaft is pivotally attached to an eccentric transmission which includes a
wheel
driven by a motor supported by the base, the base being strapped to the top
of the patient's wrist. The other end of the shaft is connected to a hand grip
which is grasped by the patient. In operation the wheel is rotated causing the
rod to telescope and pivot so that the hand undergoes movement at the wrist.
The different types of wrist movement are obtained by adjusting the alignment
of the motor housing assembly.
United States Patent No. 5,170,776 discloses a device directed
to passive articular mobilization of the foot. The device comprises a foot
rest
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interconnected with various guide rods, screws, bearings, and a motor and a
carriage.
United States Patent No. 5,352,185 discloses an ankle exercising
device including a frame with a support and a shoe attached thereto for
receiving a user's lower leg and foot respectively. This device requires two
motors (8, 9 in Figure 1 ) with one used to pivot part of the apparatus to
give
plantar flexion/dorsal extension and the other motor used to pivot another
part
of the device to produce supination/pronation of the foot relative to the
lower
leg.
It is very advantageous to provide a CPM device capable of
moving a joint through its full range of physiologic movement. This capability
would permit applications for the broadest possible range of indications and
patients. Most human joints move through more than one axis while some, like
the shoulder and hip, move through three. A major drawback to many of the
known CPM devices is that they can only be set up to move a joint through one
axis at a time. Utilizing more than one actuator in a CPM device to enable
joint
motion through more than one axis at a time becomes impractical due to bulk
and weight restrictions.
Therefore, there is a need for a device for therapeutic exercising
of joints which can be adapted for different types of joints and which
provides
a full range of joint motion through more than one axis at a time.
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SUMMARY OF THE INVENTION
The present invention is directed to a device for providing
continuous passive motion (CPM) of an anatomical joint. The device comprises
a first support member for supporting a first limb portion on one side of a
joint
and a second support member for supporting a second limb portion on the
other side of said joint. The CPM device is provided with an actuator and a
shaft with distal and proximal end portions with the shaft being pivotally
connected to the actuator at the proximal end portion of the shaft. The
actuator
pivots the shaft in sideways motion. The CPM device includes positioning
means attached to the actuator so the actuator can be positioned
circumferentially about the first limb portion with the pivotal connection
constrained to move in an arcuate path about the joint. The second support
member is adjustably attached at the distal end portion of the shaft so that
the
position of the second support member can be adjusted responsive to
positioning the actuator.
The present invention provides a device for producing continuous
passive motion of a wrist joint. The CPM device comprises an arm support
member for supporting a forearm and means for securing the forearm in the
arm support. An actuator is provided and a shaft with distal and proximal end
portions is pivotally connected to the actuator at the proximal end portion.
The
actuator pivots the shaft in sideways motion and the device includes an
arcuate
track attached to the arm support member. The arcuate track is sized to extend
at least partially around the forearm and the actuator is mounted on the
arcuate
track. The CPM device includes a hand support member including an arcuate
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ring with a bracket attached to the distal end portion of the shaft. The
arcuate
ring is adjustably mounted to the bracket so that the position of the hand
support member can be adjusted responsive to positioning the actuator. The
device includes second locking means for locking the arcuate ring to the
bracket.
In another aspect of the invention there is provided a device for
providing continuous passive motion of an ankle joint. The ankle CPM device
comprises a frame, a leg support member attached to the frame for supporting
a lower leg. The leg support member including means for securing the lower
leg therein. The device includes an actuator and a shaft with distal and
proximal end portions. The shaft is pivotally connected to the actuator at the
proximal end portion. The actuator is operable to pivot the shaft in sideways
motion. There is provided an arcuate track attached to the leg support member
which is sized to extend at least partially around the lower leg. The actuator
is
mounted on the arcuate track with the pivotal connection being constrained to
move in an arcuate path about the ankle joint. The device includes first
locking
means for locking the actuator at a selected position on the arcuate track.
The
ankle CPM device includes a foot support member adjustably mounted at the
distal end portion of the shaft so that the position of the foot support
member
can be adjusted responsive to positioning the actuator so the ankle can adopt
a neutral position.
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BRIEF DESCRIPTION OF THE DRAWINGS
The following is a description, by way of example only, of
continuous passive motion devices constructed in accordance with the present
invention, reference being had to the accompanying drawings, in which:
Figure 1 a is a perspective illustrational view of a continuous
passive motion (CPM) device for exercising the wrist joint showing a hand and
arm engaging the device, constructed in accordance with the present invention;
Figure 1 b is a view along arrow 1 b of Figure 1;
Figure 2 is a perspective view of an another embodiment of a
CPM device for the wrist absent the arm support showing the device in two
orientations, the solid lines showing the device in an orientation to provide
ulnar/radial deviation of the wrist joint, and the device shown in dashed line
providing extension and flexion of the wrist joint;
Figure 3 is a top view of the wrist CPM device of Figure 1
showing the relative positioning of the skeletal structure of the hand and
wrist
with the device in an orientation used to provide ulnar/radial deviation of
the
wrist joint;
Figure 4 is a side view of the wrist CPM device of Figure 1
showing the relative positioning of the skeletal structure of the hand and
wrist
with the device in an orientation used to provide extension and flexion of the
wrist joint;
Figure 5 is a front view taken in the direction of arrow 5 of Figure
3 with flesh covering the skeletal structure and the hand gripping a hand
grip;
Figure 6 is a front view taken in the direction of arrow 6 of Figure
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4 with flesh covering the skeletal structure and the hand gripping a hand
grip;
Figure 7 is a view similar to Figures 5 and 6 showing the CPM
wrist device in an orientation adapted to give a combination of
extension/flexion
and ulnar/radial deviation of the wrist joint;
Figure 8 illustrates the various orientations of the CPM wrist
device with respect to a user's wrist showing the variation of wrist movement
from flexion/extension to deviation depending on the orientation of the
actuator
on the circumferential track forming part of the present invention;
Figure 9 is a perspective illustrative view of a CPM ankle device
constructed in accordance with the present invention in an orientation used to
provide plantarflexion/dorsiflexion range of ankle motion;
Figure 10 is a perspective illustrative view of the CPM ankle
device of Figure 9 partially disassembled and showing details of the shoe
assembly;
Figure 11 is a perspective view of a CPM ankle device
constructed in accordance with the present invention in an orientation used to
provide inversion/eversion range of motion of the ankle joint;
Figure 12 is a view of a control panel of a controller forming part
of the present invention;
Figure 13a is a diagrammatic view of a user's leg in the ankle
CPM device of Figure 9 showing the skeletal structure of the foot, ankle and
lower leg with respect to the device in an orientation used to provide
inversion/eversion range of motion of the ankle joint;
Figure 13b is a diagrammatic view similar to Figure 12a showing
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the skeletal structure of the foot, ankle and lower leg with respect to the
device
in an orientation used to provide plantarflexion/dorsiflexion range of ankle
motion; and
Figure 14 shows the type of ankle movement obtained for different
positions of an actuator mounted on an arcuate track according to the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
A) Wrist CPM Device
Referring to Figure 1 a, a continuous passive motion (CPM) device
for exercising the wrist joint is shown generally at 20. Wrist CPM device 20
includes an arm support member 22 to receive a user's forearm shown in
dashed line at 24. Forearm 24 defines a longitudinal axis. Support 22 includes
a flexible sleeve 26 which is secured around the forearm by two hook and loop-
type fastening straps 28 and 30 engaged with hooks 32 and 34 respectively.
CPM wrist device 20 includes an arcuate track 40 with support 22 secured to
the inside surface of track 40 by fasteners and standoffs (not shown). Arcuate
track 40 is a semi-circular track and in Figure 1 a is shown describing about
200° arc of a circle of sufficiently large diameter to extend around
the forearm
of the patient.
Wrist CPM device 20 includes a motorized drive actuator 42
having a housing 44 and a slotted bracket 46 rigidly attached to housing 44.
Bracket 46 is slidably mounted on track 40 so that the position of actuator 42
can be adjusted at any position on the track. Bracket 46 includes a position
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lock adjustment 48 for locking actuator 42 to track 40 in a desired position.
Indentations 49 provide lock positions for locking track 40 relative to
slotted
bracket 46. The position of the actuator on track 40 is set by disengaging
lock
adjustment 48 and sliding actuator 42 to the desired position and then
engaging
lock 48.
CPM wrist device 20 includes a shaft 50 attached at its proximal
end to a circular bracket 52 mounted on actuator 42 which in operation is
pivoted with respect thereto by a motor (not shown) enclosed within housing
44.
A controller/power supply 54 is connected to actuator 42 by power cord 56 and
may include rechargeable batteries and/or an electrical power adapter 58. The
motor within actuator housing 44 pivots shaft 50 side-to-side with respect to
housing 44.
A hand support member comprises a semi-circular ring 70
attached to a bracket 72 which is secured on the distal end of shaft 50.
Bracket
72 is slidably movable along shaft 50. Disposed between ring 70 and bracket
72 is a rubber pad or grommet 68 which acts as a flexible cushion between the
ring and bracket to allow ring 70 to flex with respect to bracket 72. A
locking
screw 74 is used to lock ring 70 with respect to bracket 72 at a desired
position
so that it cannot slide through the bracket but it can be flexed or rocked
back
and forth due to the flexible pad 68 pressed between the ring and bracket. The
hand support member includes a U-shaped cross member 76 attached at the
end portions thereof to a pair of struts 78 which are connected to the end
portions of semi-circular ring 70. Cross member 76 provides a hand grip and
a loop and hook-type fastening strap 80 covers the cross member and secures
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the user's hand 82 onto the cross member.
The range of pivotal motion of shaft 50 is set by adjusting two
range of motion (ROM) slide switches 53 (both shown in Figure 1 b) located in
slot 55 (Figure 1 a) operably coupled with a goniometer located within housing
44. Graduated markings 57 on the actuator are used as a reference for setting
the position of the range of motion stop limit switches 53. These switches 53
determine the angular limits in which shaft 50 operates by limiting the
pivotal
movement of shaft 50.
Controller 54 contains control circuitry including a three position
switch 59, position 1 corresponding to on/off; position 2 corresponding to 50%
of full load; and positron 3 corresponding to 100% of full load. Controller 54
contains the reverse-on-load technology to monitor the motor current which is
disclosed in United States Patent No. 4,716,889. The actuator pivoting shaft
50
operates within preset values and if a preset value is exceeded, the motor
changes direction to move shaft 50 in the opposite direction. If a patient
resists
the motion of shaft 50 the motor current increases and once the threshold
current is exceeded the unit reverses direction.
Figure 2 illustrates an alternative embodiment of a wrist CPM
device 90 in which the arm support is not shown. CPM device 90 includes a
track 92 which is circular in shape as compared to the semi-circular track 40
of the embodiment of Figure 1 a. Indentations 94 provide lock positions for
locking track 92 relative to slotted bracket 46. When the motor pivots shaft
50
on actuator 42 shown in solid in Figure 2 the drive bar pivots about axis 96,
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and for the actuator repositioned on track 90 shown in dashed line the drive
bar
pivots about axis 98. The distance that the distal end portion of shaft 50
pivots
relative to the track 92 is adjusted or preset by the user or operator to
accommodate the limitations of the wrist undergoing therapy so that either
full
range of extension, flexion, ulnar and radial deviation or a limited range for
each motion is obtained as desired.
Human joints (articulations) can move in a single plane,
perpendicular planes or in a combination of the planes. The range of motion
(ROM) principle embodying the present invention allows a single axis drive to
be positioned along a track, the center of which is concentric with the joint
being manipulated and providing the joint with its full range of motion. The
principle of operation of wrist CPM devices 20 and 90 are the same.
Referring to Figure 2, arrow 100 indicates the virtual center of the
CPM mechanism, which in use is coincident with the anatomical center of the
wrist joint. The virtual center of CPM device 20 is also is coincident with
the
anatomical center of the wrist joint. The user straps his or her arm to
support
22 (Figure 1 a) with the wrist joint aligned with the virtual center 100 of
the CPM
mechanism wherein the wrist joint is in registration with the pivot point or
connection between shaft 50 and the rest of actuator 42. The relative
positions
of the wrist joint and track remain fixed while the position of actuator 42 is
varied along track 92. Figure 2 shows that the relative position of the wrist
and
virtual center 100 remains fixed as actuator 42 slides along track 92.
Actuator
42 is shown in dashed line after being displaced about 90° along track
92. The
pivotal connection of shaft 50 to actuator 42 is constrained to move in an
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arcuate path about the wrist joint in a plane substantially perpendicular to
the
longitudinal axis of the forearm with the wrist joint floating in the plane
thereby
decreasing tension and compression on the joint. In this way the joint
alignment
is maintained throughout the range of motion of the joint.
When actuator 42 is moved from the position producing deviation
indicated by the solid line in Figure 2 to the position producing flexion in
the
wrist, shown by the dashed lines in Figure 2, it is moved 90° along
track 92.
However, because cross member 76 is fixed to bracket 72 it also rotates
90°
through the same axis. Ring 70 is counter-rotated back to the neutral position
where cross member 76 can be gripped by the user. This is accomplished by
loosening knob 74 and rotating semi-circular ring 70 back to its original
position.
Therefore, when actuator 42 is moved along track 40, the hand support can be
moved in the opposite direction to maintain the wrist joint in the neutral
position.
The hand support members are constructed so that they can float
with respect to the pivotal center of the actuator by the presence of rubber
pad
68 between ring 70 and bracket 72.. This displacement accommodates the
differences in the concentric pivoting motion of the actuator and the non-
concentric pivoting motion of the anatomic joint. This small amount of
displacement prevents compression or tension being applied to the anatomical
joint while the joint moves through the preset range of motion. Therefore, in
use
with the patient gripping the hand grip member as the joint undergoes the
different types of movement the floating nature of the hand grip prevents
unwanted stresses being placed on the joint. This floating hand support is
very
advantageous over known devices in which the hand grip is rigidly attached to
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the drive. The present invention allows anatomical alignment to be maintained
when changing planes of motion.
Figures 3 and 4 show the relative positioning of the wrist joint with
the wrist CPM mechanism 20 and 90 of Figure 1 and 2, respectively, showing
the anatomical center of the wrist joint coincident with the virtual center
100 of
the CPM mechanism. The orientation shown in Figure 3 corresponds to the
orientation in Figure 1 in which actuator 42 is positioned directly below the
wrist
and forearm and bracket 72 is positioned directly below the fingers gripping
cross member 76. In this position when the motor pivots shaft 50, the wrist is
forced to undergo radial deviation in direction of arrow 110 and ulnar
deviation
in direction of arrow 112 as shown. The position of the actuator 42 shown in
dashed line in Figure 2 provides extension and flexion motion of the wrist and
hand with a user's forearm in the device, as shown in Figure 4. In this
position,
when shaft 50 is pivoted, extension of the wrist is achieved in the direction
of
arrow 114 and flexion of the wrist is obtained in the direction of arrow 116.
Figures 5 and 6 are front views as seen from arrows 5 and 6 in
Figures 3 and 4, respectively, showing the positioning of actuator 42 with
respect to the wrist to give pure ulnar/radial deviation (Figure 5) and pure
extension/flexion motion (Figure 6). Figure 7 illustrates actuator 42
positioned
at 45° between the planes of motion for pure flexion and deviation so
that when
shaft 50 is actuated the wrist undergoes combined flexion/extension and
deviation movement. Figure 8 summarizes the types of wrist movement
corresponding to the various positions of actuator 42 on track 92.
The CPM wrist device of the present invention provides a number
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of advantages over known CPM devices. It allows for a full range of motion for
flexion (0 to 90°), extension (0 to 90°), full ulnar and radial
deviation of the wrist
joint, and an adjustable range of each motion. The device provides for
combined axis motion of the wrist by simply positioning the actuator anywhere
in between the positions for each pure motion and no reassembly is required
to change from flexion to deviation. This advantage is obtained by the
actuator
positioning mechanism comprising the arcuate track which maintains the wrist
joint in registration with the pivot point of the actuator and actuator shaft
as the
actuator is repositioned around the limb and joint.
B) Ankle CPM Device
Referring now to Figures 9 to 11, a CPM device for passive
motion of an ankle joint is shown generally at 150. Ankle CPM device 150
includes a frame 152 to which a lower leg harness 154 and a shoe 158 are
attached for receiving a user's lower leg 158 and foot 160 shown in dashed
line. Harness 154 comprises a flexible sleeve 162 with a pair of hook and loop-
type fastening straps 164 for securing lower leg 158 in the harness. An
arcuate
track 170 which is preferably semi-circular, is attached to frame 152 at the
upper end portions shown at 171 in Figure 11. A contoured leg support 172,
seen only in Figure 10, is attached at one end thereof to the inner concave
surface of track 170 and at the other end to the top of a vertical support
strut
174, shown in Figure 11. This strut provides support to leg support 172 and
the
lower leg 158 when secured in the harness 162.
An actuator 180 is provided with a slotted bracket 182 which is
slidably mounted on track 170. With reference to Figure 9 and 10, a spring
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loaded lever handle 178 engages indentations (not shown) disposed along
surface 173 of track 170 every 10 degrees from 0 to 90° to lock
actuator 180 in
the desired position on the track. Actuator 180 houses a motor (not shown)
pivotally connected to a shaft 184 with the pivotal connection shown at 187 in
Figure 11 only. When the actuator is operating the motor pivots the L-shaped
shaft in the direction of arrows A and B. Actuator 180 includes two
forward/reverse buttons 185 and 193 respectively for the motor, one located on
each side of the actuator. In Figure 9, depressing button 185 drives shaft 184
upward in direction of arrow A and depressing button 193 drives shaft 184
downwardly in direction of arrow B. A goniometer 210 is mounted on actuator
180 to provide an angular reference used to set and monitor the range of
pivotal
motion of shaft 184 with respect to the actuator.
The L-shaped shaft 184 comprises two leaves 186 and 188 with
a TEFLONT"" disc 190 interposed between the leaves. Shoe 156 includes a sole
or footplate 192 pivotally attached to leaves 186 and 188. A locking knob 194
is
used to tighten leaves 186 and 188 together. By loosening knob 194 the angle
of shoe 156 with respect to shaft 184 can be changed and tightening knob 194
locks the shoe at the selected angle. Referring to the partial enlarged view
in
Figure 10, shoe 156 is installed by aligning posts 157 with holes 159 and
applying pressure to register the posts in the keyholes and then sliding the
shoe
relative to the footplate to engage the posts.
Actuator 180 is electrically connected to a controller 200 (Figure 9)
provided with a manually operated wand 202. Patient activated wand 202
contains a thumb activated button 204 for turning the unit on and off.
Controller
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200 may be battery operated or an adapter 206 can be used for providing power
from a wall socket. Controller 200 contains the control electronics and a
rechargeable battery (not shown).
Figure 12 shows the front panel of a preferred embodiment of
controller 200 provided with an on/off button 240, a first limit switch 242, a
second limit switch 244 and light emitting diode indicators 246 associated
with
each. The user depresses switch 204 to provide the ankle movement. Switch
204 is released to stop actuator 180 or to program the range of motion.
Referring
to Figures 9 and 12, to set the range of motion for actuator 180 requires the
programming of only two points, the beginning point of the range of motion
(limit
1 ) and the end point of the range of motion (limit 2). The first position or
limit is
set by depressing button 185 until the shaft reaches the first limit 1 and
then
releasing button 185 and pressing limit button 242. The second limit is set by
depressing button 193 until shaft 184 reaches the second limit 2 and then
releasing button 193 and pressing limit button 244. The controller stores
these
two ROM limits which are manually set by the patient or therapist. Once the
limit
values are programmed and stored arm 184 travels between the two preselected
limits. Controller 200 utilizes the reverse-on-load technology described
above.
In operation the user secures his or her foot and leg into ankle
CPM device 150. Referring to Figure 9, with actuator 180 mounted on track 170
at an upper end thereof on either the right or left side, once the power is
turned
on, shaft 184 and shoe 156 pivot up and down in the direction of arrows A and
B respectively. This provides a plantarflexion/dorsiflexion range of motion.
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Referring specifically to Figure 11, for subtalar joint complex mobility,
actuator
180 is located at the bottom of track 170. This provides an inversion/eversion
range of ankle motion as represented by arrows C and D. The pivotal
connection 187 of shaft 184 to actuator 180 is constrained to move in an
arcuate path about the ankle joint in a plane substantially perpendicular to
the
longitudinal axis of the lower leg. In this way the joint alignment is
maintained
throughout the range of motion of the joint.
The range of motion of the CPM ankle device is dependent on the
position of actuator 180 along the arcuate track 170 and the range of motion
operating limits set with motion controller 200 described previously. In order
to
change the range of motion of CPM ankle device 150 from flexion to
inversion/eversion, the user depresses lever handle 178 (Figure 9) on actuator
180 and slides the actuator along track 170 to the desired position. Lever
handle 178 is released thereby locking the actuator in this position. With the
actuator assembly in the selected position footplate 192 and shoe 156 are
rotated to the vertical orientation and knob 194 is tightened. Ankle joint
movement comprising a combination of inversion/eversion and flexion/extension
is obtained by positioning actuator 180 at an angle between 0 and 90°
and
pivoting the foot plate to the vertical position and locking the shoe in the
vertical
position.
Figures 13a and 13b illustrate the positioning of a leg of a patient
showing the relative positioning of the lower leg 250, ankle joint 252 and
foot
254 with respect to actuator 180. The positioning shown in Figure 13a,
corresponding to Figure 11 provides inversion/eversion range of motion of the
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ankle joint and shows the virtual center 260 of the ankle CPM device
coincident
with ankle joint 252 in which the ankle joint is in registration with the
pivotal
connection between shaft 184 and actuator 180. Movement of actuator 180 to
the position shown in Figure 13b to give plantartlexion/dorsiflexion range of
ankle motion shows the ankle joint is still in registration with the pivot
point.
Figure 14 illustrates the transition from one type of ankle
movement to the other as a function of the position of actuator 180 on track
170. Therefore, similar to the wrist CPM devices disclosed above, the actuator
slidably mounted on the semi-circular track maintains the pivot point
circumferentially disposed about the ankle joint with different
circumferential
positions giving different combinations of ankle joint movement.
Those skilled in the art will appreciate that the devices disclosed
herein can be adapted for other joints in which passive motion in more than
one plane is beneficial. Thus, while the CPM devices for wrist and ankle
joints
have been described and illustrated with respect to the preferred and
alternative
embodiments, it is intended that the scope of the invention be defined by all
of
the embodiments within the ambit of the claims and their equivalents.
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