A SPLINT

Abstract: A splint (17) includes first and second collars (18, 19) pivotally supported on a body member (20) and adjustable so as to adjust the internal dimensions of the splint (17). A plurality of spaced resilient pads (21-27) are provided on the internal surfaces of the splint (17) so as to exert pressure on a limb (11) held in the splint (17) while allowing vascular flow. The splint (17) is provided with a support (36) for supporting the extremity of a limb, such as a hand (14) or foot. The support (36) allows some movement of the limb extremity to reduce swelling by promoting vascular flow.

Description: A Splint The present invention relates to a splint for a frac¬ tured limb and in particular to a more efficient method of holding a fractured limb, such as a wrist, in reduction. The most common used method of main¬ taining reduction of a stable Colles' Fracture is by the use of a plaster cast. It is inexpensive and can be efficiently applied to the patient's limb. Howev¬ er, it does not offer any indication to the clinician applying the cast of the intra-cast pressures that may lead to compartment syndrome. Once the cast is set it is difficult to adjust. If the clinician then finds the fracture site is misaligned the cast must be redone. There is no easily made adjustment that allows loosening to accommodate swelling of the fore¬ arm and wrist, or tightening of the cast as the swell¬ ing reduces. The proposed preferred method of maintaining of Colles 1 fracture, a specific type of fracture, involves the use of a modular adjustable outer casing. This casing has a locking mechanism which can easily be adjusted by the clinician, but tamperproof by the patient. The adjustment is in small steps to allow objective recording of the splint settings. There are preferably three sizes of casing, covering a similar anthropometric range to that of functional bracing commercially available. The common incidence of Colles' fracture across the population is a further factor in detailing the splint dimensions. The inter¬ nal contours of the casing are designed so as to avoid creating a complete collar around the limb. This feature gives a path for the flow of fluid from the trauma site, avoiding pressure build up. There is also preferred stepped adjustment of the hand support in the lateral and median planes. This sup¬ port incorporates some adjustment to allow limited movement of the hand in palmar flexion, but not dorsi- flexion, and lateral movement in both adduction and abduction. The flexibility of cast positioning gives the clinician more options to balance the maintenance of reduction of the fracture components and allowing movement of the forearm and hand promoting muscle tone. It can also reduce swelling conventionally occurring with Colles 1 fractures by promoting vascular flow induced by hand movement. Plaster casting is recognised as providing poor main¬ tenance of reduction. Other treatments, such as external and internal fixation, pose other post-reduc¬ tion problems especially in relation to the elderly who may have poor bone structure due to Osteoporosis which does not provide a suitable site to hold the fixtures. At points where the casing applies pressure to the limb, integral components indicate when safe intra- cast pressure levels have been exceeded that may build up during or after treatment. The indicator is appro¬ priate to alert both the patient and clinician of high pressures at the casing/limb interface, indicating unsafe intra-cast pressures. According to an aspect of the present invention, there is provided a splint for supporting a fractured limb comprising a rigid outer casing including a plurality of spaced pressure sites located at the inner surface or surfaces of the casing and operative to apply pressure to a limb to be supported whilst retaining a vascular flow path. This splint can be designed so as not to hinder tendon function and to allow space for free vascular flow, which can reduce swelling. It can also reduce reflex sympathetic dystrophy, nerve entrapment and compartment syndrome. The pressure sites are preferably provided by resilient pressure pads located on the inner surface or surfaces of the casing. Each pressure pad can be individually chosen or adjusted to provide the appropriate individual pressure for its particular point of application. For example, some points of the limb may benefit from more pressure than others and vice versa. This is not possible with a conventional cast. The casing preferably comprises at least first and second portions adjustable relative to one another so as to adjust the internal dimensions of the casing. The casing may comprise longitudinally spaced proximal and distal collars, each provided with one or more pressure sites. These collars can provide visual access to the limb. The collars are preferably individually adjustable to adjust the internal dimensions of the casing. In the preferred embodiment, the splint comprises means to support the limb so as to allow limited movement of the limb extremity or extremities. The term extremity is intended to include a hand or foot or the like. Allowing movement of these body segments can reduce swelling commonly occurring with Colles' fractures by promoting vascular flow through movement of the extremity. The splint may include pressure sensing means for sensing pressure exerted on one or more of the pressure sites. The pressure sensing means may be incorporated in one or more pressure pads. In an embodiment, the pressure sites are adjustable in dependence upon the sensed pressure to adjust the pressure produced thereby. According to another aspect of the present invention, there is provided a splint for a fractured limb comprising longitudinally-spaced proximal and distal collars and means for supporting a hand, foot or other body segment in relation to another as appropriate at the side of the distal collar remote from the proximal collar. In preferred arrangements the collars are individually adjustable; in addition there are rigid interconnec¬ tions between the collars and between the distal collar and the hand, foot or other body segment support. According to another aspect of the present invention there is provided a splint for a fractured limb comprising at least one collar, the collar comprising an internal pad or cell, and means for sensing the pressure exerted on said pad or cell. Preferably there are at least two collars and each collar has a plurality of pressure sensing means. In the light of the pressure sensed, the size of the collars and/or the pressure applied by said pads or cells may be individually adjusted. According to another aspect of the present invention there is provided a method of adjusting a splint in accordance with the second aspect wherein the adjust¬ ment is made in dependence upon the sensed pressures. This method may be used during development of a splint, to determine the pressure to be applied at the various pressure sites. Subsequent splints may then omit any pressure sensing means. Preferred embodiments may have one or more of the following features: A rigid outer casing which is adjustable by a measured amount to accommodate a variation in dimensions within a section of the anthropometric range of the popula¬ tion. A number of standard component sections which may be added to for specific holding positions after treat¬ ment . These sections may be removed as part of rehabilitation therapy. One or more axes of adjustment dependant upon the holding position required. A measurable adjustment achieved through the use of a spigot locating within a number of recess options available. This will result in a change in dimension of the splint by a known amount. This allows objec¬ tive records to be kept of treatment given to a patient. An outer casing which can be adjusted and a pressure indicator/alarm which can be reset without removal or replacement of the splint. Incorporated within the outer casing are a number of pressure indicators. These are located where the holding pressures will be applied to the fracture site and the surrounding areas where the splint is support¬ ed on the body. The pressure indicator may comprise a small electronic pressure sensor, a mechanical diaphragm, or a reservoir with liquid which above a specified pressure, transfers to another container where it can be seen, or any other appropriate sensing or indicating device. The indicator will also act as a warning alarm to the patient or clinician that excessive pressure has built up at the splint-body interface. The patient can then seek medical assistance to adjust the splint. The alarm may be given by an audible/visible or a vibratory method, or by a combination of these. The splint will be made of materials that will allow radiographs to be taken with the splint in place. Splints in accordance with the present invention may be based on the use of a modular outer casing and an option for the inner wall to be customised to the forearm or any other limb or body part using mechani¬ cal adjustable of the circumference of the splint collars or using air cells which can be inflated or deflated to take up the space between the outer casing and the body. The valve through which the air cell is inflated/deflated may also fasten the air cell in position within the casing of the splint. Previous studies into plaster casting techniques for Colles' fracture show a potential for excessive pres¬ sure to build up within conventional plaster casts, leading to compartmental syndrome. Plaster casts have a limited ability to be adjusted once set. The clini¬ cian relies heavily on experience to feel the cast wall is applying the correct pressure, and is in the correct position. There is a lack of objective infor¬ mation available to the clinician when applying the splint to maintain reduction. A commercially avail¬ able system which incorporates such feedback has not yet been found. An earlier splint for Colles' fracture of the wrist that incorporated a pressure interface is known as the Aberdeen Brace. This system of splinting produces localised high interface pressures. It comprises a commercially available functional brace modified to accept monitoring components. The flexibility of the splint wall and a lack of a hand support contributes to the high intra-cast pressures. The hand support of the present invention when applied to Colles' fracture of the wrist was found to reduce the forces applied to the forearm and wrist necessary to hold the position of the splint over the fracture site using the hand support as a locator and to reduce the effectiveness of forces generated by the muscles of the forearm that may cause misalignment. Plaster casting is still the most popular method of maintaining reduction of Colles' fracture. Yet it has been acknowledged that this method is limited in its usefulness. There are commercially available air splints for use in emergency situations, which apply a uniform pressure over the whole forearm. These are not designed to maintain a holding pressure on specif¬ ic areas of the forearm over a six week period. Thermoformed splinting materials are difficult to apply to Colles 1 fracture due to the heat of the material on the patient and the short manipulation time before the material cools and stiffens. It then requires reheating. Preferred embodiments of the present invention as applied to Colles' fracture of the wrist will now be described, by way of example only, with reference to the accompanying drawings, of which: Fig.l shows the forces necessary to maintain reduction of a Colles' fracture of the wrist; Fig.2a and 2b indicate the locations of the applied holding pressures necessary on two perpendicular axes; Fig.3a and 3b show a splint in accordance with a first embodiment of the present invention; Fig.4 shows a cross section of the splint of Fig. 3. Fig.5 shows the splint of Fig.3 about to be applied to a wrist; Fig.6 shows a splint of Fig. 3 in its closed configu¬ ration applied to a patients arm; Fig. 7 shows a schematic view of the splint of Fig.3 with various parts omitted to show the flow of blood; and Fig. 8 shows a splint in accordance with a second embodiment of the present invention. Colles' fracture is diagnosed as occurring 25mm from the distal end of the radial bone. The vectorial components a, and b, resulting in the holding force R, that are required to maintain reduction of the frac¬ ture are shown in Figure 1. The three point loading technique used to apply the holding pressure at points 11 to 16 are shown in Figures 2a and 2b. A first embodiment of the present invention is shown in Fig.3. A splint 17 comprising two collars 18 and 19 made of engineering plastic and a main body 20. These are contoured to apply pressure at the prede- termined positions only via closed cell foam pads 21 to 27 or alternatively via air cells which are adjust¬ able in pressure 54 and 55 as shown in Figure 8. The pressure indicators 30 to 33 are used to warn the patient and clinician when excessive intra-cast pres¬ sures occur during application of the splint and during use. The two collars are connected to the main body 20 that locates along the axis of the distal end of the ulna bone of the forearm. The two collars pivot at the attachment point to the main body on two flat hinges 34 and 35. A second feature relating to the pressure sensing indicator/alarm and their location within the collars of the splint is shown in Fig. 4. The positions of the sensors/pads of the splint in position are shown in cross-section on the distal collar and defined as follows. The pressure sensors 30 and 31 are incorporated into the rigid outer casing of the collar 19 under the closed cell foam pads 21 and 22. The position and configuration of the pads in relation to the wrist and forearm provide the holding force in the directions of a and b shown in Fig. 1. Opposing the applied force from the pads 21, 22 on collar 19 are pads 23, 27 set opposite and are attached to the main body of the splint 20. The range of adjustment within the collar around the hinge does not affect the positioning of the pads enough to require repositioning of them. The holding pressure is applied to the bone fragment and the proximal shaft of the radial bone. The configura¬ tion of the pads 24, 25, 26 and integral sensors 32, 33 is repeated in the proximal collar 18. When a predetermined safe pressure threshold has been exceed¬ ed the sensor will trigger an alarm. The alarm may be visible, audible or vibration or a combination of two or more. The alarm and pressure sensor may be inte¬ gral in the form of a diaphragm which is moved to allow a peg to be visible above the surface of the casing, or a coloured liquid reservoir that is compressed forcing the liquid into a restricted tube which passes the outer surface of the casing where it can be seen. Alternatively, the alarm and sensor may be separate in the form of a strain gauge and minia¬ ture loudspeaker with a microprocessor that would be powered by a watch battery. The pads 21 and 22 are 37mm x 40mm long and apply a holding pressure that overlaps the fragment and shaft giving support to the realignment of the bone. The pads avoid applying pressure over the medial, radial or ulna nerve which pass through the wrist. Applica¬ tion of pressure over the dorsal and volar aspects of the forearm is kept to a minimum to allow free move¬ ment of the tendons promoting early mobilisation of the hand and digits. Fluid can drain back into the body from the fracture site through areas where pres¬ sure is not applied as shown in Fig. 7. The two collars are separated by a 15mm gap 53. The position¬ ing of holding pressures on to the forearm in differ¬ ent axial planes avoids isolating sections of the circulatory system. The gap allows fluid flow between the pressure zones of the two collars 18 and 19. If a hand support is not used it is envisaged the proximal pads would need to exert a greater holding pressure on to the forearm to maintain stability of position. It would also be advantageous to maintain a three point loading on the fracture site. As the proximal forearm is not so badly affected by the fracture there are more options for the positioning of the holding pressure. The range of travel within the casing had been deter¬ mined from the previously mentioned anthropometric and commercial information. It was determined a 10mm change in diameter of the splint collars was necessary to cover the variation of wrist dimensions across the proposed three sizes of splint casing. An alternative to the preferred pad and sensor config¬ uration is the use of air cells as sensors and adjust¬ ment Fig. 8. The air cells 28 and 29 replace the foam pads and sensors within the proximal collar, shown in Fig. 8, and the distal collar of the splint. Valves 54, 55 are used to inflate and deflate the bellows arrangement of the individual cells to fill the gap between the casing and the forearm/wrist. The air will be inserted through a hand pump that may have an integral pressure indicator 56. When pressure is applied to the cell that exceeds the safe threshold an alarm will be triggered that is audible, visual or vibratory or any suitable combination. A third feature, shown in Fig. 3a, is the adjustment of the collars 18 and 19. The spigot for the distal collar 46 and two ridges on either side at 47 are part of the main body 20. The collar 19 has measured grooves 49 in the tongue 48 that overlaps the main body and spigot. Once the collar circumference has been set by the clinician the collar can be fixed in position using a tamperproof nut 50. This configura¬ tion is repeated on the proximal collar 18. There is a detachable hand support 36 that limits movement in palmar and dorsiflexion, ulna and radial deviation. The hand support does not immobilise the hand completely. It allows a few millimetres of movement in all directions to avoid joint stiffness and to promote vascular flow. The support is adjust¬ able laterally along the axis of the forearm using the same configuration of a locating spigot 38 on the main body of the splint into indentations at measured intervals on the hand support 37. The support locked into position using a tamperproof nut 39. The cross bar support 40 is adjustable to accommodate varying hand widths when the hand support 36 is being set by the clinician. The cross bar 40 sleeve onto the main hand support section 41 and is fixed in position using a tamperproof screw 42. The bar is covered in an inert closed cell foam 43 that helps to distribute the support load over a larger area just behind the metacarpophalangeal joints of the fingers. Where the thumb joins the hand, at the carpo-metacar- pal joint, this area is used to locate the cross bar 40 and so avoid slippage of the splint along the axis of the forearm which would cause the splint to give an inappropriate support to the fracture site. The hand support has an option to allow adjustment to the fixed holding angle of the hand 36a. The main hand support would have the lateral adjustment bar 43 and the cross bar support 41. The cross bar support will pivot on pin 44 and use grooves 51 and a spigot to give measured angular adjustment that is locked by a screw 45 and a tamperproof nut 52. Figs. 5 and 6 show splint 20 that is preferably applied as follows: 1. The uninjured forearm/wrist is used to gauge which of the three sizes of brace or solint 20 will be fitted. 2. The hand support 36 with the correct degree of palmar flexion/ulna deviation pre-set is attached to the brace making sure the cross bar 40, 41 lies just behind the metacarpophalangeal joints of the fingers. 3. Manipulation and reduction is carried out by the doctor. 4. The underlying stockinette is applied to the forearm. 5. The splint/brace 20 is applied whilst the forearm is held in reduction. 6. The hand is located into the cross bar 41, which can be adjusted to fit different hand widths and thicknesses. 7. The proximal collar 18 is then closed around the arm until the collar "feels" to be at the correct pressure, and fastened together with the nut provided. 8. The above sequence is repeated with the distal collar 19. 9. Alternatively if the air cells 28, 29 are used the proximal and distal collars could be set close to the forearm/wrist. A pressure evaluation as made by Talley Ltd. 59 could be used to inflate the air cells to a pre-set pressure which would be achieved once the space had been filled between the casing and the forearm/wrist. 10. The radial bone is then checked to ensure reduction is being maintained properly . 11. The splint position and pressures are reviewed . 12 . All nuts are tightened and locked . Although the above-described modular splints are similar in weight to a plaster cast , and initially more expensive the benefits will be as follows : Less incidence of compartment syndrome by the use of the intra-cast pressure monitor/alarm. This avoids surgery to restore some function to the hand when the median nerve is damaged through blood occlusion . Patients can have an indicator that tells them when high pressures are occurring, and to return to the hospital . Less incidence of misalignment of the distal fragment and the proximal shaft of the radius . This may involve surgery to reset the original frac¬ ture where function of the hand has been severely affected . Obj ective information may be available to the clini ¬ cian during application of the splint . This should help less experienced staf f apply the splint more accurately . Records can be kept of the splint settings . Thi s information will be useful to the clinician if compli¬ cations arise after treatment . Adjustments to the spl int can then be more obj ectively monitored and evaluated as part of assessment of the efficiency of the treatment . The casing can be adjusted easily if the condition of the trauma site changes. An increase, or decrease in swelling will affect the compartment pressure and the holding pressure applied to hand and forearm. Adjustment of the hand support allows an appropriate amount of movement to the hand. The time taken to apply and monitor the splint and that taken using plaster treatment is similar. The skill of the clinician is enhanced by the objective feedback from the interface pressure indicator provid¬ ing more considered treatment. Physiotherapy time is also reduced due to improved function post-cast. The large potential market allows mass production techniques to be used to produce the finished product. This should bring the cost of the splint to within the cost of functional bracing, normally used post-cast. The use of a hand support reduces the hand's ability to produce a force against the splint. It also acts as a locator for the splint casing onto the forearm/wrist. Various modificati'ons may be made to the above- described splints. They may comprise only a single collar or more than two collars. They may be designed for the upper arm in which case the hand support may be omitted. They may be modified to be applied to a leg or ankle with or without an appropriate foot support. They may also be modified for the limbs of animals. The disclosures in U.K. patent application no. 94/11445.1, from which this application claims priori¬ ty, and in the abstract accompanying this application are incorporated herein by reference.

Claims: CLAIMS 1. A splint for supporting a fractured limb comprising a rigid outer casing including a plurality of spaced pressure sites located at the inner surface or surfaces of the casing and operative to apply pressure to a limb to be supported whilst retaining a vascular flow path. 2. A splint according to claim 1, wherein the pressure sites are provided by resilient pressure pads located on the inner surface or surfaces of the casing. 3. A splint according to claim 1 or 2, wherein the casing comprises at least first and second portions adjustable relative to one another so as to adjust the internal dimensions of the casing. 4. A splint according to claim 1, 2 or 3, wherein the casing comprises longitudinally spaced proximal and distal collars, each provided with one or more pressure sites. 5. A splint according to claim 4, wherein the collars are individually adjustable to adjust the internal dimensions of the casing. 6. A splint according to any preceding claim, comprising means to support the limb so as to allow limited movement of the limb extremity or extremities. 7. A splint according to claim 6, wherein the extremity support means includes a support structure extending beyond the casing and including stops positioned either side of a passage for the extremity. 8. A splint according to claim 7, wherein the stops are adjustable relative to one another for adjusting the size of the passage. 9. A splint according to any preceding claim comprising pressure sensing means for sensing pressure exerted on one or more of the pressure sites. 10. A splint according to claim 9, wherein the pressure sensing means is incorporated in one or more pressure pads. 11. A splint according to claim 9 or 10, wherein the pressure sites are adjustable in dependence upon the sensed pressure to adjust the pressure produced thereby. 12. A splint for a fractured limb comprising longitudinally spaced proximal and distal collars and means for supporting a limb extremity as the side of the distal collar remote from the proximal collar. 13. A splint for a fractured limb comprising at least one collar which includes an internal pad or cell, and means for sensing the pressure exerted on said pad or cell. 14. A method of adjusting a splint according to claim 13, the adjustment being made in dependence upon the sensed pressure or pressures.

Inventors: TORRENS GEORGE EDWARD, TORRENS, GEORGE, EDWARD
Applicants: TORRENS GEORGE EDWARD, UNIV BRUNEL, BRUNEL UNIVERSITY, TORRENS, GEORGE, EDWARD
Application year: 1995
Main classification: A61F5
IPC codes: A61F5