CA2384683A1 - Dynamic splint for carpal tunnel syndrome treatment - Google Patents

Abstract

A method and apparatus for a splint appliance to apply dynamic pressure to t he transverse carpal, volar carpal, an intra carpal ligaments, tending to relie ve contractures of the ligaments and thus relieving the pain and correcting altered kinematics associated with carpal tunnel syndrome, thus increasing t he carpal volume, while providing free movement of the patient's wrist with minimal impediment during activities of daily living, both at home and at work. The apparatus consists of a forearm component (431) representing the splint body and designed to maintain alignment and support for a biasing mea ns (420) positioned on the ulnar side of the forearm (50), the biasing means (420) consisting of a spring (424) located at approximately the ulnar side o f the carpus and connected to a palmar component (410) fastened to the ulnar side of the hand. The biasing component (420) provides resistive force to volar glide in a manner which accurately models the kinematics of the carpus and forearm.

Description

DYNAMIC SPLINT FOR CARPAL TUNNEL SYNDROME TREATMENT
CROSS-REFERENCES TO RELATED APPLICATIONS
This application claims priority based on inventor' s following: U. S. Patent Application Ser. No . 09/391, 577 , filed on September 8, 1999; U. S. Provisional Patent Application Ser. No . 60/227, 225, filed on August 23, 2000.
TECHNICAL FIELD
This invention relates generally to me di cal therapeutic devices for treating and curing functional disorders of the carpal area of the arm. More particularly, the present invention provides a splint for providing dynamic pressure to the transverse carpal, volar carpal, and intra carpal ligaments, tending to relieve contractures of the ligaments and thus relieving the pain and correcting altered kinematics associated with carpal tunnel syndrome (CTS) by increasing the carpal volume, while providing free movement of the patient's wrist with minimal impediment during activities of daily living. Additionally, the device provides optional adjustable resistance in either direction for selective, preventative, and therapeutic impetus in reestablishing normal cocontraction for a more permanent, lasting solution.
BACKGROUND ART
A. General Description of the Condition Carpal tunnel syndrome (CTS) is a painful condition caused by compression of the median nerve of the forearm as it passes through the wrist canal, or carpal tunnel.
The median nerve and the flexor tendons pass from the forearm to the hand through the carpal tunnel;
compression can result from either a reduction in carpa 1 tunnel volume, swelling of tissues passing through the canal, or both. Prolonged exertion at a keyboard or manual labor are common, but by no means the only, associations of the syndrome. More specificall y, CTS is believed to be caused by a biomechanical ligament imbalance in the volar carpal ligaments, namely, a thickening of the palmer transverse carpal ligament (PTCL, also known as the retinacular ligament), a thickening of the volar intracarpal ligaments, and contraction of an assortment of volar carpal ligaments.
Note that throughout this specification, the term "volar" shall be interpreted as "in the direction of the palm of the hand" and "dorsal" shall be interpreted as the opposite of "volar", that is, in a direction away from the palm of the hand or directed outwardly from the back of the hand. Unless specifically stated otherwise, all descriptions and observations shall be made from the standpoint of an individual's right hand and forearm for consistency and ease of description. The discussion which follows applies equally well to either hand or forearm.
B. Kinematics of the Carpal/Forearm Complex The flexor muscle tendons of the forearm acting on the wrist, fingers and thumb exert a collective static force power many times greater, volarly, than the extensor muscle tendons acting to stabilize the same members of the wrist and hand dorsally. This interaction between the flexor muscles (antagonist) and the extensor muscles (agonist) which tends to hold the joint in a fixed and stable position is termed "cocontraction." The ratio of these opposing forces is normally four to one flexor to extensor. However, work demands often increase this ratio through hypertrophy of the flexor muscle tendon units by intensity and duration of tasks requiring dominantly finger, thumb, and wrist function.
The effect of the volar flexor forces, acting upon the PTCL as a pulley, attenuate the PTCL and apply force s anteriorly and medially. This places traction forces to the ligament ends of the carpus. Each night, while the muscles are at rest, the volar intracarpal segments restore their normal position grossly; however, some minute anteriomedial -deformity remains, and slack of the PTCL is concurrently taken up by contractile forces of this and the other ligament (s) . Numerous cycles of force followed by rest develop an established deforming characteristic which is manifested by narrowing the horseshoe ends of the carpal tunnel, which are held in position by a thickening PTCL and other volar carpal ligaments, resulting in a transverse deformity.
Simultaneously, the PTCL acting as a pulley concentrates the load of the finger and thumb function so that a volar glide is initiated, where volar glide is defined as movement of the carpal metacarpal complex as a unit in a volar direction. This volar glide of the carpa 1 metacarpal complex attenuates the predisposed thin dorsal carpal ligaments (DCL) originating from the distal radial ulna (DRU). Since the volar carpal ligaments collectively become less stressed, they begin to contract, thus encouraging the anteriomedial collapse of the intercarpal spaces simultaneous to a longitudinal deformity.
The long moment arm of the carpal muscle tendon units are only capable of stabilization of the carpus when the muscle tone is within normal limits, i.e.
approximately 4 to 1 flexor to extensor, respectively;
these forces acting on the carpus in flexion are convergent toward the muscle origin and are regulated by an interplay of antagonists, pulleys and j oint alignment .
A variation of one or more serves to simplify convergence towards a direct line to this point of origin and shorten the distance therebetween. This force results in a decreasing biomechanical advantage which is manifested by a volar shift of the axis of the proximal carpal row.
This may account for the propensity of patients with CTS
to develop odd compensatory behaviors like flexing the wrist during power grasping, conceivably to account for the change in position of the more volarly placed PTCL.
Carpal tunnel volume is further reduced and any other predisposition will hasten onset of the painful and crippling CTS condition.
Thus, the resistance of the PTCZ and related volar ligaments are encountered when returning the carpal metacarpal complex to a neutral position, i.e. dorsal glide, should be indicative of the severity of the condition of carpal tunnel syndrome or the propensity of the subject to incur the condition.

C. Standard Treatment of Carpal Tunnel Syndrome To date, CTS has been treated with wrist rests, anti-inflammatory medications, cortisone injections, surgery, or static wrist splints . Alone or combined, these treatments have met with varying degrees of minimal success. Symptom relief is short lived and compounded by surgical complications . Even after these treatments are applied, the patient's biomechanical configuration remains unchanged or complicated. Reduced grasp strength has been well documented. The obvious solution, i.e.
removing the cause of the injury by refraining from the manual labor believed to cause the problem, is not always practical since the cause of the injury is frequently the means by which the patient obtains his or her livelihood .
The next best choice, prevention through proper intervention, can be achieved by enlarging the carpal canal to maintain adequate space for the median nerve and thus avoid compression. However, the mechanism for correcting this condition long term does not exist.
The carpal canal can be enlarged by osteopathic manipulation and stretching maneuvers, thereby alleviating compression on the median nerve and resolving CTS. While severe cases may require other t re atment, manipulation is effective in the majority of cases and has the advantage of being prophylactic, i.e. a preventative. Optimum resolution of the symptoms requires frequent stretching and the assistance of another person, a physician or therapist to perform the manipulation. There is a need for an appliance which a patient can use to augment treatment by the physician or therapist . It is known from studies of rehabilitated knee joints and elbow joints that the longest period of low force stretching produces the greatest amount of permanent elongation of connective tissue. Ideally, tha stretching would be accomplished by means of an appliance which is adjusted by the physician or therapist to provide the appropriate force for stretching, preferably continuously.
However, there are a number of difficulties in the use of such appliances. First, simply prescribing the use of an appliance does not mean that the patient will use it properly. If a patient is expected to put on and remove an appliance, a properly adjusted appliance must not be able to be put on incorrectly or to inflict either too much or too little stretching. Proper use also refers to the compliance or self-discipline of the patient and how easy it is to use the appliance. In general, an appliance that is mechanically simple, easy to use, and comfortable to wear will more likel y be used as directed.

Second, the skin is sensitive to long term pressure, which can cause a localized loss of circulation and lead to ulceration. Obviously, a patient will not be comfortable if an appliance causes such irritation. On the other hand, sufficient pressure must be applied in order to be effective. Such an appliance must be comfortable to wear and not cause undue irritation or pressure on the skin.
Third, an appliance must not interfere with the normal activities of living. It must be comfortable in the sense that it does not interfere with the function of the arm, wrist, and hand. Otherwise, a patient is unlikely to wear the appliance long enough to be fully effective, preferably overnight, or when performing routine tasks which may irritate the median nerve or promote the deformities . An appliance duplicating the manipulation by a physician or therapist would obviously interfere with the patient's use of the hand. What is desired is an appliance which duplicates as much of the physician's treatment as possible without interfering with the use of the arm, wrist, or hand.
The prior art is replete with splint appliances which are designed to reduce CTS pain. One such appliance is described in U. S. Patent No. 5, 417, 645, entitled "Flexible Wrist Splint for Carpal Tunnel Syndrome Treatment", which issued to Lemmen on May 23, 1995. The '645 patent provides a splint with an elongated, flexible member having a palmar portion configured to extend from the middle of the forearm, across the volar carpal area, and across the palm to bias the palm in a dorsal direction. It also functions as a reminder of the proper positioning to relieve pressure on the median nerve associated with CTS. It is designed to allow use of the fingers and thumb and to permit near normal hand function.
Another such appliance is described in a series of patents by Davini, i.e. U. S. Patent Nos. 4, 966, 137 (issued Oct 30, 1990) and its reissue Re. 34, 627 (issued May 31, 1994) , and 5, 385, 527 (issued Jan 31, 1995) , each entitled "Splint System" . Each of these appliances is based upon essentially the same premise, namely, each functions to enlarge the carpal tunnel by compressing the radius and ulna together using an external clamp and bandage configuration which encircles the carpus, so that free use of the hand and fingers is permitted.
Stretching of the PTCL or other carpal ligaments is not addressed by these devices.
Still another such appliance is described in U. S.
Patent No. 5, 468, 220, entitled "Carpal Tunnel Bracelet" , which issued to Sucher on November 21, 1995. Like the '137 and '627 patents, it also relieves pressure on the median nerve by increasing the volume of the carpal tunnel. The appliance encircles the carpus and, using spring loaded pads, provides dorsal and volar pressure on the radius, ulna, and other carpal bones whi_ ch tends to increase tunnel volume. It can be removed by the user if long term use causes irritation or sensitivity to the skin.
Fourth, it is desirable to have an appliance which will not only promote the stretching of the carpal ligaments so as to relieve pressure on the nerve, but also to restore the proper ratio of cocontraction between the flexor and extensor muscles which tend t o hold the carpal joint in the proper alignment while c a rpal ligament stretching is being effected. This encouragement of cocontraction is missing from all existing devices . In order to achieve proper j oint stabilization, the device must allow the ligaments to re-engage and reestablish joint stability as we 11 as increasing muscle tone of the flexor and extensor muscle s around the perimeter of the joint.
Thus, what is needed is a splint appliance with the following characteristics:
1. The appliance must duplicate the stretching maneuver performed by a trained therapist to stretch the PTCL and collective volar carpal ligaments over time;

2. The appliance must be easily worn and removed by a patient with minimal or no training required for its use;
3 . The appliance must not present pre s sure point s to the patient or unduly irritate the skin;
4. The appliance must be easily worn during routine daily life with little or no interference with motion during supination and pronation or during manipulation o f the 10' fingers;
5. The appliance must both promote restoration of the carpal ligaments to their prop a r configuration as well as restore t he proper cocontraction of the stabilizing flexor and extensor muscle groups against the carpal joint; and, 6. The appliance must be able to accommodate individuals having different forearm and wrist measurements.
DISChOSURE OF THE INVENTION
It is therefore an obj ect of the present invention to provide a splint appliance for treating or preventing carpal tunnel syndrome.

Another object of the invention is to provide a splint appliance which is comfortable and can be worn during the normal activities of daily living without undul y interfering with hand movement.
It is a further object of the invention to provide a means to relieve pressure on the median nerve by applying low intensity, extended volar pressure to the hand and thus stretch the palmer transverse carpal ligament.
It is a further object of the invention to promote restoration of the cocontractive forces of the flexor and extensor muscles on the carpal joint to allow the carpal ligaments to be properly stretched and/or contracted so as to achieve a normal configuration.
It is a further object of the invention to provide a splint appliance which can be worn and removed by an unskilled patient without misadjustment.
It is a further object of the invention to provide a splint appliance which will not bind while performing supination or pronation movements but will continue to provide restorative force to the carpus during such movements.
It is a further object of the invention to provide a splint appliance which is simple in construction.
It is a further object of the invention to provide a splint appliance which can be easily adjusted to provide variable tension against dorsal movement of the hand.

It is a further obj ect of the invention to provide a spl~.nt appliance which accurately models the kinematics of the carpal/metacarpal complex in order to permit dorsal force to be effectively applied against volar movement .
The invention described herein to satis fy these objects consists of a dynamic orthotic appliance designed to provide low level pressure on the PTCh over extended periods of time while at the same time allowing the user to execute the standard activities of daily living, as well as general activities particular to the user's occupation, without interference from the orthotic. It consists of three components - a biasing component, a forearm component, and a palmar component . The biasing component models the movement of the carpal/metacarpal and distal forearm/carpal j oints by employing a unique and innovative tensioning arrangement. It provides continuous, low pressure force which opposes movement of the wrist in a volar direction. The forearm component provides a platform for a biasing component and maintains the biasing component in particular relationship and alignment with the ulnar aspect of the forearm and carpus during all normal movements. The palmar component is positioned on the ulnar side of the hand and is designed to allow unobstructed flexion of the fingers and opposition of the thumb with the fingers; it also couples the biasing component to the hand. The three components are articulated in a novel manner which allows supination and pronation of the forearm without binding of the appliance or obstructing free movement. It is believed that the placement of the. biasing force on the ulnar side of the forearm and hand to avoid interference with daily activities of living and the provisions made to allow the biasing component to track the hand during complex maneuvers of the forearm and hand are novel and new to the prior art .
Further objects and advantages of this invention will become more readily apparent upon reference to the following detailed description of a preferred embodiment, as illustrated in the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a elevation view of the ulnar aspect of an embodiment of the dynamic splint as it relates to the right arm in accordance with the present invention with its maj or topological features, with the hand shown in a position where the spring is not applying tension agains t the hand.
FIG. 2 shows the same elevation view of the dynamic splint as in FIG. l, but with the spring applying dorsal tension against a volar movement of the hand.

FIG. 3 shows a plan view of the forearm component of the one embodiment of the dynamic splint illustrated in FIG. 1. with its major topological features.
FIG. 4 shows an elevation view of the radial aspect of the dynamic splint as it relates to the right arm in accordance with the present invention_ FIG. 5 shows a sectional view of the splint and forearm, illustrating the stabilizing mechanism used for positioning the spring along the ulnar side of the forearm.
FIG. 6 shows a dorsal view of the hand with the palmar component attached the ulnar side of the hand and the positioning of the springs with relationship to the carpus.
FIG. 7 shows the volar view of the hand with the palmar component attached to the ulnar side of the hand_ FIGS 8, 9, and 10 show three views of the connection block used for attaching the spring to the palmar component of the dynamic splint.
FIG. 11 shows the method of securing the end of th a spring to the palmar component of the dynamic splint using the connection block.
FIG. 12 shows a plan view of the radial side of the forearm component of the preferred embodiment of the dynamic splint with its major topological features.

FIG. 13 shows a plan view of the ulnar side of the forearm component of the preferred embodiment of the dynamic splint with its major topological features.
FIG. 14 shows a plan view of the forearm component of the preferred embodiment of the dynamic splint illustrated in FIGS . 12 and 13 with its maj or topologic al features .
FIG. 15 shows a sectional view of the splint and forearm taken from F IG. 12, illustrating how the dorsal block is employed in the preferred embodiment .
It is to be understood that the present invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments, and of being practiced or carried out in various ways within the scope of the claims . Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and not of limitation.
BEST MODES OF CARRYING OUT THE INVENTION
A. Definitions While several terms have been previously defined herein within the context of the discussion, the terminology to be used in the subsequent detailed description will now be set forth as an aid for those who may not be familiar with these terms as used by the inventor. The terms "volar" and "dorsal" indicate directions of movement or location, where a volar movement is in the direction of the palm of the hand and dorsal movement is in the direction of the back of the hand. Similarly the terms can indicate position, where, for example, a volar carpal ligament would be a ligament located in the carpal complex on the palmar side of the hand. The terms "proximal" and "distal" relate to the position of the described object with relationship to the trunk of the body. Thus, the radius and ulna each has a proximal end ( the elbow area ) and a distal end ( the wri s t end) . Similarly the carpus is composed of a proximal carpal row of five bones and a distal carpal row of five bones, where the proximal carpal row adj oins the distal end of the radius and ulna. "Supination" is defined as a rotational movement of the radius and ulna which results in a palm up position of the hand, whereas "pronation" i s defined as a similar rotational movement resulting in a palm down position of the hand. "Dorsiflexion' is defined as a movement of the hand which forms an arc by extending the wrist dorsally. "Cocontraction" is defined as the interaction between the flexor muscle tendons of the volar forearm acting on the wrist, fingers and thumb , with the dorsal extensor muscle tendons of the forearm, to stabilize the same members of the wrist and hand, thus tending to hold the carpal j oint in a fixed and stable position.
"Glide" is a term used to describe an involuntary movement of the carpal metacarpal complex, whereby the proximal carpal row is said to glide in a shear manner which maintains a parallel relationship with the distal forearm. A volar glide is observed when, with the fingers extended, the palmar plane has moved in a volar direction with relationship to the distal forearm carpal joint, such movement consisting of a shear movement in a volar direction of the proximal carpal row. The magnitude of volar glide is indicative of the severity of CTS . Similarly, a dorsal glide is observed when the dorsal plane of the hand is moved dorsally through a shear movement of the distal forearm carpal j oint, an opposite movement of volar glide. "Ulnar deviation" is defined as a movement of the hand in an ulnar direction without either dorsal or volar movement; the plane of ulnar movement is perpendicular to that of dorsal-volar movement. "Radial deviation" is defined as a movement of the hand in a radial direction opposite to that of ulnar deviation.
It has been observed in practice that there is a change is distance between the metacarpals and the distal ulna- radius during flexion and extension of the hand.
This change of distance results in an elliptical path being followed by the hand during its range of motion from flexion to extension. Furthermore, a differential motion has been observed during supination and pronation between the distal and proximal areas of the forearm. It is desirable in any dynamic splint design to mirror these kinematics so that a proper dorsal force can be applied by the splint appliance to resist volar glide.
B. Initial Embodiment FIG. 1 illustrates an embodiment for a dynamic splint appliance for use in the treatment and prevention of CTS in accordance with the present invent ion, generally designated by the numeral 10. The sp lint appliance 10 consists of a forearm component 20, a palmar component 30, and a biasing component 40 and is shown configured in FIG. 1 to the right forearm 50 and right hand 60 of a user with carpal tunnel syndrome. While subsequent descriptions will for consistency and clarity be directed towards use of the appliance 10 with the right forearm of a user, the same appliance can be used on the left forearm and hand of a user, with all elements of the appliance being mirror images of those elements for the right forearm and hand.

The forearm component 20 is shown more generally in the plans of FIGS . 1, 2, and 4 . The forearm component 20 is configured as a generally semicircular splint body 100 shown contoured around the dorsal side of the forearm 50 in FIG. 1 and in a flattened plan in FIG. 3. The splint body 100 is oriented on the forearm 50 with its distal edge 120 generally covering the distal radius and ulna, its proximal edge 130 in the direction of the elbow, and its ulnar edge 110 oriented so that it is generally parallel to the ulna (not shown) of forearm 50. The proximal strap support 140 and the transverse strap fulcrum 160 are wrapped over the dorsum of the forearm 50 so that both extend to points generally adj acent to the radius bone of the forearm 50, so as to capture only the dorsum of the forearm 50.
Supination and pronation of the forearm ordinarily cause the biasing component to bind and the forearm component to buckle at the dorsum of the forearm. Cutout 150 on the dorsum of splint body 100 is provided to solve the binding problem. It is generally centered on the dorsum of the forearm 50 and functions to prevent binding of the appliance during supination and pronation.
Allowing the distal and proximal ends of splint 100 to move relatively independently of each other while being connected only along the ulnar edge 110 provides a two point stabilization of the ulnar edge 110 during supination and pronation and maintains alignment of the ulnar edge 110 along the ulnar side of the forearm. The proximal edge 130 of splint body 100 is convexly contoured on forearm 50 along the dorsum towards the distal radial end and away from the proximal radial end so that the extensor muscle group of the forearm is left uncovered and ergonomically accommodated without binding .
Splint body 100 consists of a thin metal core material cut to the shape seen in FIG. 3 and enclosed by a covering material composed of a neoprene external nylon or other anti-perspiration material, such material as i s in common use and knowledge among physical therapists, so that the splint body 100 can be molded and customized t o individual forearms and trimmed to accommodate individual differences in forearm length and circumference . The exterior of the covering material should is sensitive to attachment by the hook component of an industry standard hook-and-loop system of the type sold under the trademark "VELCRO", so that transverse strap 190 can be removably attached to appropriate areas of the splint body 100, a s described below.
Splint body 100 is secured to the forearm 50 by distal forearm strap 170, proximal forearm strap 180, and transverse strap 190. Distal forearm strap 170 is secured to the splint body 100 by one or more rivets 172, of which a single representation is shown. The rivet 172 as shown also serves to prevent the biasing component 4 0 from significant movement either distally or proximally along the ulnar side of the forearm. Distal forearm strap 170 is of sufficient length to allow end 174 having an attached hook and loop fastener strip 177 to be brought around the ulnar side of the forearm, across the distal end of the volar forearm, and over the radial forearm, where end 174 passes through distal buckle 175 and back onto distal forearm strap 170, where a cooperating hook and loop fastener strip (not shown) is fixed so that end 174 is removably secured to distal forearm strap 170.
Proximal forearm strap 180 is secured to the proximal strap support 140 by one or more rivets 182.
Proximal forearm strap 180 is of sufficient length to allow end 184 having an attached hook and loop fastener strip 185 to be passed around the radial side of the forearm, across the proximal end of the volar forearm, and over the ulnar forearm, where end 184 passes through proximal buckle 188 and back onto proximal forearm strap 180, where a cooperating hook and loop fastene r strip (not shown) is fixed so that end 184 is removably secured to proximal forearm. strap 180. As shown in this embodiment, proximal buckle 188 is fixedly attached to the fixed end 186 of transverse strap 190 which is fastened to the splint body 100 by rivet 189. However, two separate straps could be employed and fastened with separate rivets as required.
Transverse strap 190 is secured to the splint body 100 by rivet 189. As seen from FIGS 1 and 4, transverse strap 190 follows a line from the proximal ulnar edge o f the splint body, across the volar forearm, and over the transverse strap fulcrum 160, where end 192 having a hook and loop fastener strip 193 is removably secured to the distal strap 170 at an arbitrary point, either by using a cooperating hook and loop fastening strip (not shown) or preferably by attachment directly to the material comprising the distal strap 170 which is sensitive to attachment by the hook component of a standard hook-and-loop fastening means . Transverse strap 190 moves to a limited extent across the transverse strap fulcrum 160, a portion of splint body 100 which provides a platform for transverse strap 190 against the forearm and prevents it from rubbing or binding during supination and pronation.
Because of a differential rotation between the distal end and the proximal ends of the forearm during supination/pronation, the transverse strap 190 tends to stabilize the splint body 100 by translating this differential rotation motion to the ulnar edge 110, thus maintaining alignment of the ulnar edge 110 with the ulna .
Referring to FIGS 1, 3, and 5, the biasing component 40 is constructed of a formed wire 200 having a supporting end 202 and a torquing end 204. The formed wire 200 is preferably made from a length of 2 4 gauge 3 04 stainless steel with a B2 finish, as is commonly known to physical therapists in the construction of orthopedic appliances . A plurality of spring loops 206 are formed near the torquing end 204 with each comprised of one or more turns of wire as needed to produce a suitable tensioning force at the torquing end 204 of approximately 8 pounds . Formed wire 202 is enclosed in the covering material 208 along the ulnar edge 110 of splint body 100 , wherein the proximal end of supporting end 202 is allowed to rotate freely within the sheath formed by the covering material as the forearm moves in supination and pronation. Optionally, rivets (not shown) may be placed at the proximal end of the splint body 100 at the ulnar edge 110, wherein the proximal end of the supporting end 202 is captured between the ulnar edge 110 and the rivet and prevented from migrating within the covering material away from the ulnar edge 110. An ulnar saddle 210 is formed in the formed wire 200 and positioned over the distal ulna 52 to rotationally stabilize the formed wire 200 during pronation and supination of the forearm. Rivet 172, around which the ulnar saddle 210 is positioned, serves to stabilize the formed wire 200 from significant proximal or distal movement . As seen more particularly in FIG. 5, the ulnar saddle 210 curves from the ulnar side of the forearm 50 up to a point on the dorsum of the forearm and then back to the plane of the ulnar edge 110 of splint body 100.
The spring loops 206 are formed and positioned along formed wire 200 so that they are located laterally on the ulnar side of the ulnar-radial/metacarpal joint and the intra-metacarpal joint and are not covered by distal strap 170. It is believed that each spring to op 206 models the action of the corresponding joint. This double loop spring arrangement has been found to provide sufficient proximal-distal tolerance to accommodate changing distance between the metacarpals and the distal ulna-radius during flexion and extension of the hand, and it thus prevents binding of the palmar component 30 when connected to the torquing end 204. The torquing end 204 of formed wire 200 is shaped so that, when connected with the palmar component 30 and attached to a hand, the hand at substantially 20° of dorsiflexion does not encounter resistance from the biasing component 40.

Although the general loop configuration is the preferred embodiment, other tensioning shapes may be used to provide resistance to movement of the torquing end of the biasing component and still remain within the spirit of the invention, namely, to apply a low force load oppo sing volar glide over long intervals of time. For example, during testing of the device, an arrangement was formulated (not shown) consisting of slotte d bars comprising the support end and torquing end of the biasing component, with a coiled spring wound around a spool, similar to that found in clocks, fixedly connected to the support end. The torquing end rotated about the axis of the coiled spring as the end of the coiled spring applied pressure opposing dorsiflexion. It was found that this arrangement did not track the change in distance between the metacarpals and the distal ulna-radius during flexion and extension of the hand, although this could be accommodated by fashioning a pin in the palmar component that would travel along a slot in the bar comprising the torquing end during flexion . Howeve r, a rigid bar of such a configuration would interfere with ulnar and radial deviation during the normal activities of daily living.
It should be noted that normally the range of deviation for a hand is approximately 35° in a radial direction and 45° in an ulnar direction, but much less range is required to achieve the activities of daily living. The biasing component in the form of a shaped wire 200 allows 20° ulnar deviation, but less restriction on radial deviation, thus permitting a more natural movement of the hand.
Referring now to FIGS . 6 and 7, the palmar component 30 is illustrated as having a rigid ulnar gutter 300 enclosing the ulnar side of the hand and serving as a platform for the fixed attachment of connection block 310. Ulnar gutter 300 is preferably comprised of a plastic material of any suitable composition to enable it to be custom fitted and shaped to the individual hand.
Connection block 310 is permanently affixed to ulnar gutter 300 by any suitable means known to the art, including rivets, screws, glue, or capture in a molded channel in ulnar gutter 300. Palm strap 320 is permanently affixed to the volar end 302 of the ulnar gutter 300 by means, of a rivet 322, although any suitable means known to the art can be employed. The volar end 302 of ulnar gutter 300 and the volar end 324 of palm strap 320 are shaped so that they are substantially confined between the thenar crease 62 and the MCP joint crease 64 of a typical hand 60 so as to permit unimpeded use of, the hand during normal activities of daily living .
Palm strap 320 narrows as it passes over the thenar web 66 in order to prevent interference with normal activities . This contouring of palm strap 320 allows unobstructed flexion of the fingers and opposition movement of thumb with that of fingers. The dorsal end 326 of palm strap 320 is removably secured to the dorsal end 304 of the ulnar gutter 300 by cooperating hook and loop attachment strips 328 attached to the palm strap 320 and ulnar gutter 300 by any suitable means . An alternate embodiment (not shown) for palm strap 320 would be to employ the buckling arrangement as described for distal forearm strap 170, while contouring the shape of the strap to accommodate the thenar crease, the MCP joint crease, and the thenar web as described above.
The construction of connection block 310 is given in FIGS 8, 9, 10, and 11 . Connection block 310 is formed o f a rectangular block of material, preferably of metal composition, having a top side 319 as shown in FIG. 10, a receiving end 317 as shown in FIG. 9, and a clamping end 318 as shown in FIG. 10. Receiving end 317 has a centrally located horizontal bore 311 which is colinear with the longitudinal axis of connection blo ck 310. An inclined bore 312 in the same axial plane as the horizontal bore 311 is slantingly positioned so that at receiving end 317 inclined bore 312 does not intersect horizontal bore 311. Incline bore 312 is s1 ant ingly disposed towards the clamping end 318 and horizontal bore 311. Inclined bore 312 gradually approaches horizontal bore 311 so that it~ intersects horizontal bore 311 forming notch 313, which gradually becomes wider as inclined bore 312 fully intersects and terminates before exiting horizontal bore 311 on its opposite si de.
Vertical bore 314 intersecting two opposing faces of connection block 310 is perpendicular to the axis of both inclined bore 312 and horizontal bore 311. and is located at the widest point of notch 313. Vertical bore 314 is threaded to receive set screw 315. A dado is formed between the inclined bore 312 and the top side 319 of connection block 310 . Top side 319 is fixedly j oined to ulnar gutter 300 with its receiving end 317 oriented proximally and its clamping end 318 oriented dorsally as described previously.
During appliance use, the torquing end 204 of formed wire 200 is inserted into the horizontal bore 3 11 on the receiving end 317 and made to protrude from the clamping end 318. The ulnar gutter 300 is positioned and strapped to the ulnar side of the hand. Set screw 315 is then tightened against formed wire 200 to force formed wire 200 into notch 313 which clamps the connection block 310 to the formed wire 200, so that connection block 310, and consequently the ulnar gutter 300 and the ent ire palmar component 30, is constrained from rotational movement about formed wire 200 and from longitudinal motion along formed wire 200 by the clamping action of notch 313 on formed wire 200.
This embodiment of the invention has been described to illustrate one way-in which the theory of the invention is implemented in a dynamic orthot ic. This embodiment, while effective in treating CTS, has not proven to be conducive to mass manufacture, but it has been presented to show how the problems of preventing binding during supination and pronation and of providing a biasing component with the proper characteristics can be solved without departing from the basic concept of the invention.
C. Preferred Embodiment The preferred embodiment of the invention is shown in FIGS . 12 through 15 . This embodiment has been found to be more manufacturable than the previous embodiment and illustrates how the implementation of bias ing component and the solution to prevent binding of the biasing component can differ from the first embodiment and still be within the concept of the invent i on.
Referring to FIGS. 13 and 14 which illustrate in perspective the ulnar and radial aspect of the orthotic as it is worn on the right forearm 50, and to FIG 15 which shows the pattern of the forearm component, the preferred embodiment of the invention consists of orthotic 400 which is also composed of a palmar component 410, a biasing component 420, and a forearm component 430. The palmar component 410 is essentially the same as palmar component 30 described previously.
In describing the forearm component 430 of the preferred embodiment as shown in FIG. 14, it is instructive to compare it with the forearm component 20 of the first embodiment as shown in FIG. 3. Both figures are oriented in the same manner to the right forearm.
The body 431 of the preferred embodiment consists of two pieces of a substantial external nylon or other anti-perspiration material, such material as is in common us a and knowledge among physical therapists, cut to the shape seen in FIG. 14 and enclosing a core pad of neoprene.
Also enclosed within the two layers of covering material are several metal portions which shall be described presently. The covering material should be sensitive to attachment by the hook component of an industry standard hook-and-loop system of the type sold under the trademark "VELCRO" , so that distal buckle 175 and proximal buckle 188 of the previous embodiment can be eliminated and transverse strap 440 and distal carpal strap 460 can be removably attached to appropriate areas of splint body 431, as described below.
The ulnar support plate 470, radial support plate 480, and block plate 490 are sandwiched between the two layers of material composing the splint body 431. Each plate defines a reinforced area on the orthotic to assist strap attachment to body 431 and to position and orient biasing component 420 to the forearm.
Ulnar support plate 470 is positioned on the ulnar portion 432 of body 431 and radial support plate 480 is positioned on the radial portion 433 of body 431 and in opposing relation to ulnar support plate 470. Both are composed of plastic, dead soft aluminum (a term familiar to persons knowledgeable in the art ) , or some other suitable material which is relatively rigid. Dorsal gap 434 separates the ulnar and radial portions of body 431, with the dorsal strap spanning dorsal gap 434. A first end of dorsal strap 450 is attached to ulnar support plate 470 by means of rivet 500 inserted through washer 501, the outer fabric covering of body 431, ulnar support plate 470, the inner fabric covering of body 431, another washer (not shown) , and secured in place in the manner o f rivets . A second end of dorsal strap 450 is attached to radial support plate 480 in the same manner as the first end and secured by rivet 502 and washer 503. Dorsal strap 450 is positioned on the dorsum of forearm 50 (FIG.
12) . It is composed of the same material as body 431 and may also contain an expandable portion (not shown) if desired to allow dorsal strap 450 to expand and contract during supination and pronation of forearm 50. It serves to couple the ulnar and radial portions of body 431 to each other in a manner to allow independent movement of said portions without binding but maintaining a general orientation of the portions to forearm 50.
The first end of transverse strap 440 is fixedly attached to radial support plate 480 by means of rivet 504 and washer 505 in the same manner as described previously. The second end of transverse strap 440 has a hook portion 441 sewn thereto and on one side so that it can be wrapped about the volar forearm and attached to the surface of the ulnar distal portion of body 431.
Transverse strap 440 corresponds to transverse strap 190 of the first embodiment (FIG. 3) , but passes from the radial proximal side of the forearm to the distal ulnar side, rather than from the ulnar proximal side of the forearm to the distal radial side as shown in FIG. 3.
Like transverse strap 190, transverse strap 440 stabilizes body 431 by translating differential rotation motion observed in supination and pronation to the radia 1 portion 433 to maintain alignment of radial portion 433 with the radius of forearm 50. In both cases, transverse strap 190, 440 loads the supporting end of the biasing comp onent 40, 420.
Referring again to FIG. 14, block plate 4 90 is located on the distal edge 435 of splint body 431 and sandwiched between the two layers of material composing the splint body 431. It may be composed of a rigid material which may be appropriately formed, such as plastic, dead soft aluminum, and the like. Its function is to provide support for distal carpal strap 460 and to provide a platform for the biasing component 420. Block plate 490 is comprised of the following three portions curved portion 491, horizontal portion 492, and vertical portion 493. These portions are shown more c1 early in the cross-sectional view shown in FIG. 15. Vertical portion 493 forms a ninety degree angle with horizontal portion 492 at bend 497; curved portion 491 begins its curvature at bend 496 and continues around the carpus for an arbitrary distance . Construction of block plate 490 out of dead soft aluminum permits curved portion 491 to be easily molded to each individual carpus . Horizontal portion 492 is parallel to the plane 55 defined by the centers of the ulna and radius of forearm 50. It has been found by experimentation and measurement that the ninety degree orientation between portions 493 and 492 remains invariant over the range of supination and pronation. Along the angled proximal edge 498 of block plate 490 are two tabs 494 and 495 to accommodate the biasing component which shall be presently described.
Tabs 494, 495 are bent back over portion 492 to capture a section of the biasing component 420 therebetween for rotational movement of biasing component 420. The first end of distal carpal strap 460 is fixedly attached to block plate 490 by means of rivet 506 and washer 507 in the same manner as previously described for the first end of the dorsal strap. The second end of distal carpal strap 460 has a hook portion 461 sewn thereto and on one side so that it can be wrapped about the carpus and attached to the surface of the distal portion of body 431 to hold body 431 in close contact and orientation with the forearm.
The preferred embodiment of the biasing component 420 is illustrated in FIG. 14. It is comprised spring wire and divided into a torquing end 423, a middle segment 422, and a support end 421, with middle segment 422 and support end 421 being sandwiched between the two layers of fabric comprising the splint body 431 and with torquing end 423 exposed. Torquing end 423 extends from the within body 431 to attach to the palmar component 410 in the same manner as described previously. Along its extent are two spring loops 424 positioned along the wire so that they are located laterally on the ulnar side o f the distal forearm/carpal joint and the carpal/metacarpal joint and slightly dorsal to the axis of the carpus. The two spring loops 424 may optionally be enclosed in a pouch (not shown) composed of the same material comprising the splint body 431 in order to prevent chafing of the ulnar side of the hand and to provide a comfortable pad. Middle segment 422 is loosely captured by tabs 494, 495 on block plate 491 so that torquing end 423 may swing vertically along portion 493 of block plate 491 without binding. Middle segment 422 is positioned to rotationally stabilize and maintain the position of the formed wire comprising the biasing component 420 during pronation and supination of the forearm. Support end 421 extends along the radial side of forearm 50 so that its end is captured between radial support plate 480 and the outer layer of fabric comprising body 431. Support end 421 may be bent slightly from the plane formed by torquing end 423 and middle segment 422 to better conform to the radial side of the forearm. To additionally stabilize the biasing component 420, an ulnar arm 425 formed of spring wire is loosely attached to the wire at the apex of the angle formed by the torqueing end 423 and middle segment 422 by means of a simple loop in its end.

The opposite end of ulnar arm 425 is captured between ulnar support plate 470 and the outer layer of fabric comp rising body 431.
The preferred specifications for the biasing component are as follows . The distance between the proximal spring loop 424 and the bend between middle segment 422 and the torqueing end 423 has been found to be 0 . 65 inches . The obtuse angle between the middle segment 422 and torquing end 423 should be between 125 °
and 130°, and the angled proximal edge 498 of block plate 490 should therefore mirror this angle. The obtuse angle between the middle segment 422 and support end 421 should be between 125° and 135°.
D. Use of the Orthotic The invention is designed to realisticall y mirror the movement of the hand without interfering with the normal activities of daily living . The bias 'ing component is positioned by the palmar component and the forearm component to reside laterally on the ulnar side of the distal forearm/carpal joint and the carpal/metacarpal joint, and slightly dorsal to the axis of the carpus.
This positioning allows the appliance to correctly trac k the elliptical path that the hand follows during extension and flexion. It is adjusted by the therapist or at the factory so that force applied by the biasing component is neutral when the palm is at approximately 20° dorsiflexion. When the palm is moved in a volar direction, the biasing component tends to force the palm back to the neutral position at 20° dorsiflexion. This force is resisted by the extensor muscles of forearm 50 which further tends to strengthen the extensors and restore a normal four to one flexor to extensor ratio, which tends to stabilize the carpal-metacarpal joint. At the same time the dorsal attitude of the palm tends to apply a long-term low force against the PTCh and over time will lengthen the ligament and relieve the symptoms of carpal tunnel syndrome.
In the preferred embodiment, the support end of the biasing component sets the tension of the dual springs at the carpus by tightening or loosening the transverse strap, which loads the springs to the desired tension.
This permits the tension on the biasing component to be easily adjusted. Furthermore, the design of the biasing component in the preferred embodiment enables the orthotic to fit more individuals because it will accommodate varying sizes of forearm and wrist .
Measurable improvement in the patient' s condition should be observed in about three to four weeks of continuous use.

While only two embodiments have been illustrated and described, they serve to illustrate obvious modifications which are contemplated within the scope of this invention and the following claims . Accordingly, the scope of the invention should be determined not by the embodiments illustrated but by the appended claims and their legal equivalents.

Claims (16)

What is claimed is:

1. An orthopedic appliance adapted to be worn on a forearm and a hand of a person exhibiting symptoms of carpal tunnel syndrome, said appliance comprising:
a. a biasing component means having a supporting end and a torquing end, said torquing end disposed to apply a continuous, low level force to the hand over time and in a direction encouraging dorsal glide;
b. a palmar component means coupling said torquing end to the carpal-metacarpal complex of the hand; and c. a forearm component means rigidly but removably attached to the forearm, said forearm component means providing a stable platform for said supporting end and maintaining alignment of said torquing end with the ulnar side of the carpal-metacarpal complex during movement of the forearm and hand;
whereby contractatures of the volar carpal ligaments are relieved and the cocontraction ratio is restored between the flexors and extensors of the forearm, without interfering with normal activities of daily living.

2. The orthopedic appliance described in claim 1, wherein said palmar component means comprises the following:
a. an ulnar gutter clasp having a dorsal end and a palmar end, said dorsal end extending from the ulnar side of the hand to approximately the midpoint of the dorsal side of the hand, said palmar end extending from the ulnar side of the hand to approximately the midpoint of the palm;
b. a palmar strap having a fixed end and a attachable end, said fixed end permanently secured to said palmar end of said ulnar gutter clasp, said attachable end passing from said palmar end across the thenar web between the thumb and forefinger to said dorsal end and being removably secured to said dorsal end so as to secure said ulnar gutter clasp firmly to the ulnar side of the hand, and c. a connection means fixedly attached to said ulnar gutter clasp at a point proximal to the ulnar side of the hand, whereby said torquing end of said biasing component means is coupled to said palmar component means at a point outboard of the ulnar side of the hand so as not to interfere with normal activities of daily living.

3. The orthopedic appliance described in claim 2, wherein said said palmar end is confined within the area of the palm delineated by and interior to the thenar crease of the palm and the MCP joint crease of the palm.

4. The orthopedic appliance described in claim 1, wherein said forearm component means comprises the following:
a. a body of semirigid material substantially conforming to the dorsum and sides of the forearm, said body having a distal end, a proximal end, an ulnar edge between said distal end and said proximal end, a radial edge between said distal end and said proximal end, and a dorsal portion extending from said distal end to said proximal end and between said radial edge and said ulnar edge; and b. a distal forearm strap attached to said distal end, encircling the distal forearm, and removably secured by any suitable means.

5. The orthopedic appliance described in claim 4, wherein said forearm component means further comprises a proximal forearm strap attached to said proximal end, encircling the proximal forearm, and removably secured by any suitable means.

6. The orthopedic appliance described in claim 5, wherein said forearm component means further comprises a transverse strap having a first end and a second end, said first end fixedly secured proximally to said ulnar edge of said body, said second end passing transversely across the volar forearm to be removably secured distally to said radial edge of said body, whereby said transverse strap maintains alignment of the ulnar edge of said body with the ulna of the forearm during supination and pronation.

7. The orthopedic appliance described in claim 5, wherein said proximal end of said body is recessed to permit unimpeded movement of the extensor muscle group on the dorsal side of the forearm.

8. The orthopedic appliance described in claim 6, wherein said body further comprises a radial gap extending from said radial edge a distance into said dorsal portion, said radial gap defining a proximal portion and a distal portion, whereby said proximal portion can move relatively independently of said distal portion while both said proximal and distal portions maintain alignment of said ulnar edge with the ulna of the forearm during supination and pronation.

9. The orthopedic appliance described in claim 8, further comprising a transverse tab extending proximally from said distal portion a distance generally along the path of said transverse strap and along said radial edge, said transverse tab providing a fulcrum for said transverse strap during supination and pronation of the forearm.

10. The orthopedic appliance described in claim 4, wherein said forearm component means further comprises the following:
a. a dorsal gap on said dorsal portion, said dorsal gap extending distally a distance from said proximal end and terminating a distance from said distal end, said dorsal gap defining an ulnar portion and a radial portion extending from said proximal edge, each said portion extending a distance from said proximal end of said body and unconnected along said distance;
and b. a dorsal strap spanning said dorsal gap and extending over the dorsum of the forearm, said dorsal strap having a third end fixedly connected to said ulnar portion and a fourth end fixedly connected to said radial portion, whereby said radial portion and said ulnar portion move independently within the confines of said dorsal strap.

11. The orthopedic appliance described in claim 10, wherein said forearm component means further comprises a transverse strap having a first end and a second end, said first end fixedly secured proximally to said radial edge of said body, said second end passing transversely across the volar forearm to be removably secured distally to said ulnar edge of said body.

12. The orthopedic appliance described in claim 11, wherein said biasing component means is a continuous wire from which said supporting end and said torquing end are composed with a middle segment therebetween, said torquing end positioned along the ulnar side of the forearm and hand, said torquing end having at least two adjoining coils fabricated along the length of said torquing end, said adjoining coils positioned laterally to the distal forearm/carpal and the carpal/metacarpal joints and slightly dorsal to the axis of the carpus, said middle segment passing over the dorsum of the forearm, said supporting end positioned along the radial side of the forearm in attachment with said radial portion, said middle segment serving as an axis of rotation for said support end and said torquing end, said transverse strap controlling the dorsal attitude of said torquing end through tension applied to said radial portion and therefore said support end.

13. The orthopedic appliance described in claim 12, wherein a first obtuse angle is formed between said middle segment and said support end and a second obtuse angle is formed between said middle segment and said torquing end, whereby said torquing end provides both a force resisting volar glide and simultaneously a slight force promoting ulnar deviation as tension is volarly increased against said support end by said transverse strap.

14. The orthopedic appliance described in claim 1, wherein said biasing component means comprises a spring having an axis associated with said supporting end, such that said supporting end of said spring is attached to said forearm component means and aligned with the ulnar side of the forearm while said axis is distally positioned on the ulnar side of the forearm, said torquing end of said spring attached to said ulnar side of said palmar component means to provide torque opposing volar movement of said palmar component means at substantially 20° of dorsiflexion or less, said support end of said biasing component means maintaining orientation of and stabilizing said biasing component means along the ulnar aspect of the forearm during supination and pronation.

15. The orthopedic appliance described in claim 14, wherein said axis of said spring is approximately positioned on the ulnar side of the distal forearm/carpal and carpal/metacarpal joints and slightly dorsal to the axis of the carpus, whereby an elliptical arc is formed that maintains placement of said palmar component means throughout extension and flexion of the hand.

16. A method of relieving the pain associated with carpal tunnel syndrome by increasing the carpal volume, while providing minimal impediment to the patient's carpal-metacarpal complex during activities of daily living, said method comprising the steps of a. positioning the metacarpal complex of an individual at approximately 20° dorsiflexion, whereby the said 20° dorsiflexion serves as a reference frame for movement;
b. providing resistance against volarly directed movement diverging from said reference frame by use of a biasing means approximately positioned on the ulnar side of the distal forearm/carpal and carpal/metacarpal joints and slightly dorsal to the axis of the carpus;
c. maintaining alignment of the biasing means during supination and pronation of the forearm;
and d. permitting unobstructed flexion of the fingers and opposition of the thumb with the fingers;
and e. permitting ulnar deviation of the distal forearm carpal joint.