Continuous passive motion devices for joints

The present invention provides continuous passive motion (CPM) devices for joints. An ankle CPM device includes a lower leg support attached at its lower end to a semi-circular track. An actuator slides along the track and can be locked in any desired position on the track. A shaft is pivotally connected at one end thereof to the actuator and a shoe is attached at the other end thereof. When the actuator is positioned at the bottom of the track the ankle joint of the patient undergoes inversion/eversion motion. When the motor housing is rotated 90.degree. and positioned near the top of the track plantar/dorsi flexion movement is obtained. A combination of both types of joint movement are obtained for the actuator in intermediate positions. A wrist CPM device includes a brace for the forearm attached to a semi-circular track on which an actuator is mounted. A hand grip is mounted on a semi-circular bracket and a shaft extends between the actuator and a coupling slidably mounted on the semi-circular bracket. With the actuator positioned below the forearm, when the actuator pivots the shaft the wrist joint undergoes ulnar/radial deviation movement and when the motor is rotated 90.degree. and positioned at the side of the arm extension/flexion movement of the wrist joint is obtained. Positioning the actuator in intermediate positions produces wrist movement which is a combination of extension/flexion and ulnar/radial deviation of the wrist joint.

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. U.S. Pat. No. 4,538,595 discloses several passive 
exercise devices for ankle, wrist and elbow joints. FIGS. 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 FIGS. 
18-19 and FIG. 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 FIGS. 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 FIG. 11. 
U.S. Pat. No. 4,650,183 discloses an exercise apparatus for foot and ankle 
joints. This device is used for exercise applications and to evaluate 
performance 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. 
U.S. Pat. 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. 
U.S. Pat. No. 5,170,776 discloses a device directed to passive articular 
mobilization of the foot. The device comprises a foot rest interconnected 
with various guide rods, screws, bearings, and a motor and a carriage. 
U.S. Pat. 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 
FIG. 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. 
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 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 them 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. Them 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.

DETAILED DESCRIPTION OF THE INVENTION 
A) Wrist CPM Device 
Referring to FIG. 1a, 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 
FIG. 1a is shown describing about 200.degree. 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 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 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 FIG. 1b) located in slot 55 
(FIG. 1a) 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 position 3 corresponding to 100% of full load. Controller 
54 contains the reverse-on-load technology to monitor the motor current 
which is disclosed in U.S. Pat. No. 4,716,889 and incorporated herein by 
reference. 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. 
FIG. 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 FIG. 1a. 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 FIG. 2 the drive bar pivots 
about axis 96, 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 FIG. 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 (FIG. 1a) 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. FIG. 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.degree. along track 92. The 
pivotal connection of shaft 50 to actuator 42 is constrained to move in an 
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 FIG. 2 to the position producing flexion in the 
wrist, shown by the dashed lines in FIG. 2, it is moved 90.degree. along 
track 92. However, because cross member 76 is fixed to bracket 72 it also 
rotates 90.degree. 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 
nonconcentric 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 the drive. The present invention allows 
anatomical alignment to be maintained when changing planes of motion. 
FIGS. 3 and 4 show the relative positioning of the wrist joint with the 
wrist CPM mechanism 20 and 90 of FIG. 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 FIG. 3 corresponds to 
the orientation in FIG. 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 FIG. 2 
provides extension and flexion motion of the wrist and hand with a user's 
forearm in the device, as shown in FIG. 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. 
FIGS. 5 and 6 are front views as seen from arrows 5 and 6 in FIGS. 3 and 4, 
respectively, showing the positioning of actuator 42 with respect to the 
wrist to give pure ulnar/radial deviation (FIG. 5) and pure 
extension/flexion motion (FIG. 6). FIG. 7 illustrates actuator 42 
positioned at 45.degree. 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. FIG. 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 of 
advantages over known CPM devices. It allows for a full range of motion 
for flexion (0.degree. to 90.degree.), extension (0.degree. to 
90.degree.), 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 FIGS. 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 156 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 FIG. 11. A contoured leg support 
172, seen only in FIG. 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 FIG. 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 FIG. 9 and 10, a spring loaded 
lever handle 178 engages indentations (not shown) disposed along surface 
173 of track 170 every 10 degrees from 0.degree. to 90.degree. 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 FIG. 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 187 respectively 
for the motor, one located on each side of the actuator. In FIG. 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 "TEFLON" 
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 FIG. 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 (FIG. 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 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). 
FIG. 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 FIGS. 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 187 until 
shaft 184 reaches the second limit 2 and then releasing button 187 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 FIG. 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. Referring specifically to FIG. 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 (FIG. 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.degree. and 90.degree. and pivoting the 
foot plate to the vertical position and locking the shoe in the vertical 
position. 
FIGS. 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 FIG. 13a, 
corresponding to FIG. 11 provides inversion/eversion range of motion of 
the 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 FIG. 13b to give 
plantarflexion/dorsiflexion range of ankle motion shows the ankle joint is 
still in registration with the pivot point. 
FIG. 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.