CA1224687A - Device for imparting continuous passive motion to human joints - Google Patents

Abstract

Abstract of the Disclosure An actuator for an apparatus for applying continuous passive motion to a human joint. An elongated support mounts 2 traveller for reciprocating movement relative thereto and for operative connection to a limb connected to a joint to be mobilized. A motor carried by the support drives the traveller through a reciprocating linear stroke, in a slow rhythmic cycle, whereby the limb is moved relative to the support and the joint is thus kept continually in motion. The motor embodies instrumentalities to reverse the direction of the traveller at any point in its stroke on encountering undue resistance. Preferably, the motor, traveller and associated mechanism is contained in a tubular housing slotted for access to the traveller of a connection to the body.

Description

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This invention relates to a prosthetic device used to treat a human joint by applying "continuous passive motion".
This application is a divisional of Application Serial No.
388,659, filed October 23, 1981.
The concept of "continuous passive motion" is described in the article "Joints Were Meant to Move - And Move Again" by Ohlendorf in "The Graduate", published by The Department of Information Services, University of Toronto, September/October 19~0.
Briefly, according to this concept, a human joint, for example, a knee, elbow, or finger joint, is kept under slow continuous con-strained motion as distinct from being held motionless or being moved intermittently. Keeping an injured or post-operative joint mobile rather than immobilizing it in a cast is beneficial to the cartilage.
Attempts which have been made to provide machines that exercise joints are designed for intermittent operation and do not supply continuous passive motion.
An apparatus, according to the invention, includes a support structure, usually a housing containing working parts. Harness means mounts the support structure on the patient's body or, in an alter-native arrangement, the support structure may be mounted on a crutchor bed. Traveller means is carried by the housing for reciprocating movement relative to it and is connected to an extremity of thc limb having the joint to be exercised so that the joint completes the linkage. Motor means in the housing drives the traveller means back and forth through a predetermined stroke with a slow rhythmic motion.
The present invention relates to an actuator for a prosthetic device. The actuator includes an elongated support, traveller means on the support for reciprocating linear movement relative thereto, and means connected to the traveller means for operatively engaging a limb of the body connected to a joint to be mobilized. There is motor means, preferably on the support, for driving the traveller means back and forth through a reciprocating linear stroke in a slow rhythmic cycle, 6~37 whereby the limb is moved relative to the support so that the joint is kept continually in motion. The motor means embodies means for revers-ing the direction of travel o~ the traveller means at any point in its path of travel responsive to a predetermined load.
In a preferred construction, the support is a housing having a longitudinal slot defining a guide track, a traveller mounted for back and forth motion relative to the housing, an inner tubular housing mounted in the support housing, a longitudinally extending slot offset relative to the guide track. A drive member is mounted inside the tubular housing to drive the traveller in said back and forth motion.
The traveller includes a travelling element mounted inside the support housing operatively connected through the longitudinally extending slot in the tubular housing to the drive member. The travelling element is, in turn, connected to a travel member mounted for travel along the guide track. Desirably, the motor means is contained inside the housing.
The housing may be centrally disposed in the support and the drive member centrally disposed in the housing.
The drive member may comprise a drive screw, mounted for rotation inside the tubular housing, with the travelling element mounted on the drive screw. The travelling element is restrained against rotary movement so that rotary movement of the drive screw is con-vertedintolongitudinal movement of the travelling element to move the travel member along the guide track. The travelling element preferably comprises nut means.
Desirably, the travelling element comprises an inner nut member mounted on the drive screw, inside the tubular housing, and an outer member held to the nut member by connecting means extending through the longitudinal slot in the tubular housing. The outer member is mounted to travel between the support housing and the tubular housing, and includes a pair of spaced-apart terminal stops in the support housing to define the predetermined normal stroke. The motor means is rever-sible so thatitdrives the traveller ~irst in one direction and then ~ ,r,l -- 2 -- .

in the other. Preferably, the means to reverse the direction of the motor is also actuatable by predetermined resistance of the screw member to rotation. Desirably, also, the motor means is housed inside the support housing and the tubular housing is centrally disposed in the support housing and the drive screw centrally disposed in the tubular housing. Preferably, the motor means is carried by the support. Pre-ferably, also, the motor means includes an electric motor, in which case the means for reversing may be means to monitor electrical power consumption as a measure of the appliecl load. The means reversing the motor may also include a switch operatively connected to the motor means to reverse the motor means responsive to the predetermined excessive load.
Having thus generally described the invention, it will be referred to more specifically by reference to the accompanying drawings, which illustrate preferred embodiments, and in which:
Fig. 1 is a perspective view showing a unit for treating an elbow ~oint;
Fig. 2 is a greatly enlarged fragmentary perspective view showing the wrist connection in the unit of Fig. 1;
Fig. 3 is a schematic perspective diagram, of an exploded nature, showing the arrangement of the parts in a unit;
Fig. 4 is a side elevation showing a unit for treating the knee joint in which the unit forms part of a crutch;
Fig. 5 is a side elevation of a variation of the unit of Fig. 4;
Fig. 6 is a fragmentary perspective view showing an operating unit for treating the knee joint and which is connected to a bed on which the patient is reclining;
Fig. 7 is a fragmentary perspective view showing a unit for treating a finger or thumb joint;
Fig. 8 is a perspective view of the unit shown in Fig. 7, illustrating the drive rnechanism.
Referring more particularly to Fig. 1, the device is made up of a support structure which, in this case is - 2a -~IL;;~2~
an elongated housing A connected to the shoulder by a harness B and to the waist by a belt D. Actuator or traveller means, movable relative to the housing, is connected to the wrist by a cuff C. The traveller means is supported by the housing for linear reciprocating movement relative to it. Motor meanS drives the traveller means back and forth through a ~ predetermined stroke in a slow rhythmic cycle. This imparts a corresponding reciprocating motion to the arm, thus impart-ing continuous passive motion to the elbow joint.
The speed of movement of the actuator means would, in the embodiment shown range from one-half foot to four feet per minute or from one-third to two cycles per minute.
In order to supply supination and pronation to the wrist, the cuf~ C is connected (see Fig. 2) to a special mechanism. Mo~nted for rotation on a U-shaped bracket 15 is a shaft 17, carrying a bevel gear 19, which meshes with a crown gear 21, carried on a hub 23, mounted on a plate 25 forming a part of the traveller means.
The plate 25 moves back and forth, along the housing A, and the flexing of the elbow causes rotation of the arm at the wrist, by virtue of its connection to the bevel gear 19 as it is ca~sed to ride around the crown gear 21. At the same time, the wrist is held to the plate 25 so that it makes longitudinal movements with the latter along the housing A.
Fig. 3 shows in detail the support housing, actuating means, motor mea~s and associated parts. A motor 31 drives an elongated screw 33 whose opposite end is rota-tably held in a recirculating ball-type nut 3~. ~A cylindri-cal slide 35 is connected to the nut 32 and moved linearlyunder the drive of the screw 33 between the limiting stops ; 37 and 39, which are locked to the housing A by thumb screws.

The mechanism is encased in an outer tube 41 and an inner concentric tube 42. m e tube 41 is provided with a longitudinal slot 43 and the concentric tube 42 with an elongated slot 45. The slot 43 accommoda-tes the flange connection 48 between the slide 35 and the plate 25~ The slot 45 accommodates the flange connection 46 between the ball nut 33 and the slide 35.
The motor 31 is powered by batteries 47 which operate through circuits on a circuit board 49 and is governed by controls 51. The tube 41 is provided with a gooseneck part 53 about which khere extends a bracket 55 connecting it to the harness B. The other end of the tube 41 has a terminal 56 provided with an eye 57 so that it can be hung from a suitable hook when required.
The motor 31 is a reversible motor. It will reverse as soon as an excessive load is applied~ This may be, for example, where the actuator or traveller reaches the end of its stroke and is halted by the stop 37 or 3g as the case may be. Or, it may be where there is some unplanned obstruction, for;example, sheets jamming in the mechanism or where the patient offers undue resistance. A
safety function is thus performed as well as a prime actuat-ing function.
Examples of suitable ~otors are geared D.C. Brush type motors made by Faulhaber, Escap, and Maxon Precision, all of Switzerland.
Fig. 4 describes an apparatus for flexing the knee joint. Similar numbers have been applied to similar parts, as on FigsO 1 and 3, with the excep-tion that they have been raised by 100 and the letters have been given a subscript 1.
In this case, the support housing Al forms part of a crutch for supporting the patient and embodies operating mechanism similar to~that shown in Fig. 3, except that the housing Al is straight instead of having a gooseneck end.
It has a rubber foot 157 taking the place of the terminal 56.
A handle Bl takes the place of the harness B and is provided with an armpit bar 159. The part Bl slides on the top end of the support housing Al. Taking the place of the plate 25 is a simple foot plate with straps, as compared with the supina-tion and pronation mechanism for rotating the wrist.
Fig. 5 shows an alternative arrangement in which a waistband B2 is employed to connect the top of a support housing A2 to the body. A separate crutch D supports the patient.
Fig. 6 illustrates a further form of leg exercising device. In this case, the support housing of Figs. 4 and 5 is connected to a bed. It is retained by spaced-apart brackets 61 and 62. The leg of a patient lying on the bed is connected to the foot plate as in Figs. 4 and-5.
Fig. 7 illustrates a device for flexing finger or thumb joints. Here aga~n a support housing A4 is connected to a cuff B4 mounted on the wrist and hand in place of the harness of Fig. 1. An actuator wire 425 moves back and forth from the housing A4, through a flexible guide tube`441, to a connection with the thumb.
The connection from the actuator wire ~25 to-the thumb is through a hinge 443 to a small plate 445, adhesively connected to the th~mbnail. Alternatively, the actuator member 445 can be connected to any of the fingers or several fingers at a time.
A mechanism for moving the actuator wire 425 is shown in Fig. 8. The support structure is fashioned from a hlock of plastic in which recesses have been made to accommo-date the various parts. A geared motor 447 drives a sprocket 3L~22~
432 about which there is trained a chain 433 which is also trained about a spaced-apart sprocket 435. The actuator wire 425 is connected at 437 to one of the links of the chain 433.
Batteries 446 are accommodated within the block as is an operating switch 451~ The motor moves the chain continuously so that the actuator wire 425 moves in one direction along the top run of the chain and then down along the bottom run in the other direction so as to impart substantially con-tinuous reciprocating movement to the wire 425 and conse-qu~ntly to the hand joint.
From this detailed description it will be evident that various modifications can be made within the spirit of the invention to treat various joints of the body under appropriate conditions~

SUPPLEMENTA~Y DISCLOSURE
This Disclosure and the Principal Disclosure are concerned with a portable apparatus for imparting continuous passive motion to a human joint~
Figs. 7 and 8 of the Parent Disclosure show a device specifically directed to mobiliziny joints of hand digits D
The applicant now aiscloses an apparatus within the broad concept of the Parent Disclosure, but having mechanism for mobilizing a plurality of digits of the hand, i~e. the fingers and/or thumb. This mechanism is made up of a support in the form of a cuff and means for mounting the support on the forearm. Motor and transmission means is carried by the support. Travelling means is movable by the transmission means through an elongated path in a reciprocatingimovement.
A connecting rod is connected at one end of the travelling means and connected to a manifold block or yoke. There is means for connecting the block to several fingers whereby their joints are mobilized as the manifold block is moved back and forward by the travelling means.
In a preferred construction, the connecting rod extends through an opening in the manifold to which it is held by a set screw. Beyond the manifold the connecting rod is pivotally connected to clevis means, mounted on a finger.
A separate wire connects the manifold bLock with clevis means connected to several other fingers and/or to the thumb, if desired.
A preferred way of connecting the clevis to the finger incLudes a plate which rests on the surface of the finger and a central lug extending -from it. An adhesive strip having a central slot for the lug to project through the slot surrounds the finger and holds the p:Late to it.

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A preferred form of this aspect of the invention is illustrated in the following drawings in which:
Fig. 9 is a perspective view showing a hand digit mobilizing device, according to the invention, mounted on the forearm of a patient and connected to several fingers;
Fig. 10 is an exploded perspective view showing the elements of the finger mounting means;
Fig. 11 is an enlarcJed plan view showing the relationship between the manifold, connecting rod and wire, Fig. 12 is an exploded perspective view looking at the top of the cuff and showing the interlocking fabric connecting it to the supporting housing, and Fig. 13 is a side elsvation, enlarged in compari-son with Fig. 12, illustrating particularly the construct on of the mounting arrange-ment on the ar~ and its relationship to the drive housing.
Referring more particularly to the drawin`gs, Figs.
9 through 13 show an alternative form of device for mobiliz-ing a joint of the hand as compared with that shown in Figs.
7 and 8.
The same reference numerals, in terms of tens and digits, have been used to identify like parts, as in Figs.
7 and 8, but they have been raised into 500's and the reference letters have been given the subscript S.
~he housing A5 is carried by a mounting arxangement, indicated generally by B5. The arrangement B5 is supported by the forearm and wrist.

g _ ~ _ This mounting arrangement includes an extensive ~oam pad 553, which engages the surface of the forearm and wrist. The pad 553 narrows to a neck part 555 which extends over the palm of the hand. For mounting the pad 553 is a saddle 554, of relatively rigid thin plastic, which also narrows to a neck 556 which overlies the neck 555~
Mounted above the saddle 554 is a plate 557, which narrows to a neck 559 which is held to the necks 555 and 556 by a--rivet 560.
la At its opposite or rearend, the plate 557 is spaced from the saddle 554 by a ~rop 580, which in the form shown is a tube having one end screwed to the plate 557 and having the other screwed to the saddle 559.
A fabric anchoring loop 563 is riveted to the margin of the saddle 554 midway along its length and carries a metal eye 565 to receive a belt/ for surrounding the fore-arm, which extends through an adjustable buckle anchored to the other side of the saddle 554.
A belt 569, to surround the hand, is riveted to the assembly of necks 555, 556 and 559. r~he belt 569 is provided at one end with a buckle 570. The belt 569 encircles the hand just in front of the root of thè thumb.
By this arrangement, the plate 557 is supported from the forearm with Its forepart strapped relatively firmly to the palm of ~he hand and its rear part held relatively firmly to the forearm. The plate is thus fully supported from the forearm in a position for mounting the housing A5~
To this end, the plate 557 carries a pad 551 of the well known VELCR0 (trade mark) fabric having a pile surface made up of a mass of small loops to engage a complementary pad 550 on the undersurface of the drive -- ~4 ~

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housing A5, having the VELCR0 fabric surface made up of a mass of hooks which anchor themselves to the loops of the pad 551. The ~ELCRO anchorage of the pad 550 to the pad 551 is adequate to hold the housing in place in normal usage.
But, the pads 550 and 551 may readily be peeled apaxt by pulling hard enough, for removal of the housing A5 from the mounting arrangement B5.
In accordance with this form of the invention, an actuator wire extends from reciprocating mechanism inside the housing A5 (as illustrated in Fig. 8). There is slidably mounted on the actuator wire 525 a cylindrical manifold block or yoke 560, the block 560 having an axial opening through it to accommodate the wire 525. There is a set screw 561 operating in a transverse tapped opening in the block 560 to engage the wire 525 and maintain it in position.
The end of the wire 525 carries a clevis 582 pro-vided with a tapped opening receiving the threaded end of the wire 525. The clevis has a slot 562 dividing its end into fingers 563 through which there extends a pin 564 to engage a connecting pin and finger connector, as will be described.
The connector includes a plate 565a which rests against the surface of the distal part of the finger and is held to it by an adhesive strip surrounding the finger. A
perforated lug 567 extends from the plate 565 through an opening 562 in the strip 566 into the slot 562 and is engaged by the pin 564. So with the strip 566 engaging the finger, the clevis is pivotally held to the distal end of the finger.
In a similar manner, the other fingers are connec-ted to the block 560 by respective wires 572 each having a threaded inner end, engaging a tapped opening in the b:Lock 1~

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560, and a threaded outer end engaging a tapped opening in a clevis similar to the clevis 582 and held to the finger in the same way.
A preferred actuator wire 525 is of 16 gauge solid music wire. Preferred wires 572 are of stranded 16 gauge metal, e.g. steel, wire to give them more flexibility.
The operation of the djevice is as previously described. The drive mechanism moves the actuator wire 525 back and forth in reciprocal movement which is trans-mitted to the fingers through the wires 525 and 572 so that the joints of all the fingers connected to the actuator are mobilized at the same time.
Likewise, the thumb may be linked to the manifold560 by another wire as can the little finger which is shown - free in the drawing.

Claims (18)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An actuator for a continuous passive motion apparatus for mobilizing a human joint, comprising, an elongated support, traveller means on the support for reciprocating linear move-ment relative thereto, and means connected to the traveller means for operatively engaging a limb of the body connected to a joint to be mobilized, motor means for driving the traveller means back and forth through a reciprocating linear stroke in a slow rhythmic cycle whereby the limb is moved relative to the support so that said joint is kept continually in motion, the motor means embodying means for reversing the direction of travel of the traveller means at any point in its stroke responsive to a predetermined load.

2. An actuator, as defined in claim 1, in which the motor means is carried by the support.

3. An actuator, as defined in claim 1 or 2, in which the motor means includes an electric motor.

4. An actuator, as defined in claim 1 or 2, wherein the motor means includes an electric motor and said means for reversing comprises means to monitor electrical power consumption as a measure of the applied load.

5. An actuator for imparting back and forth motion in a slow rhythmic cycle, comprising, a support housing having a longitudinal slot defining a guide track, a traveller mounted for back and forth motion relative to said housing, a tubular housing mounted in said support housing, said tubular housing having a lontigudinally extending slot offset relative to said guide track, and a drive member mounted inside said tubular housing adapted to drive said traveller with said back and forth motion, said traveller including a travel element mounted inside said support housing operatively connected through the longitudinally extending slot in said tubular housing to said drive member, said travel element being connected to a travel member mounted for travel along said guide track.

6. An actuator, according to claim 5, further including motor means to drive said drive member, said motor means being contained in said housing.

7. An actuator, according to claim 5, wherein said tubular housing is centrally disposed in said support housing and said drive member is centrally disposed in said tubular housing.

8. An actuator, according to claim 5, wherein said drive member comprises a drive screw having a screw thread mounted for rotation inside said tubular housing, andsaid travel element is mounted on said drive screw for movement relative to said thread, said travel element being restrained against rotary movement with said drive screw such that rotary movement of said drive screw is converted into longi-tudinal movement of said travel element whereby said travel member moves along said guide track.

9. An actuator, according to claim 8, wherein said travel element comprises nut means mounted on said drive screw.

10. An actuator, according to claim 8, wherein said travel element comprises an inner nut member mounted on said drive screw, inside said tubular housing, and an outer member held to said nut member by connecting means extending through said longitudinal slot in said tubular housing, said outer member being mounted to travel between said support housing and said tubular housing, and including a pair of spaced-apart terminal stops in said support housing to define said predetermined stroke.

11. An actuator, according to claim 10, further including motor means to drive said drive screw, said motor being reversible, whereby it drives the traveller first in one direction and then in the other to cause reciprocating movement of the traveller.

12. An actuator, according to claim 11, including means to reverse the direction of the motor within said predetermined stroke, when a predetermined excessive load is applied to said motor means during said travel stroke.

13. An actuator, according to claim 12, wherein said means to reverse the direction is actuatable by predetermined resistance of the screw member to rotation.

14. An actuator, according to claim 13, wherein said motor means is housed inside said support housing.

15. An actuator, according to claim 8, wherein said tubular housing is centrally disposed in said support housing and said drive screw is centrally disposed in said tubular housing.

16. An actuator, according to claim 5, further including means for reversing the direction of travel of said traveller, when a pre-determined load is applied to said traveller, during said back and forth motion.

17. An actuator, according to claim 16, including an electric motor to drive said drive member and wherein said means for reversing comprises means to monitor electrical power consumption of said motor as a measure of the applied load.

18. An actuator, according to claim 16, including motor means to drive said drive member and wherein said means for reversing com-prises a switch operably connected to said motor means, to reverse the motor means responsive to said predetermined excessive load.