GB2472168A

GB2472168A - Medical instrument to apply stimulus force to test area of body part for neuropathy testing

Info

Publication number: GB2472168A
Application number: GB1018620A
Authority: GB
Inventors: Ian James Spruce
Original assignee: Individual
Current assignee: Individual
Priority date: 2008-11-05
Filing date: 2008-11-05
Publication date: 2011-01-26
Anticipated expiration: 2028-11-05
Also published as: GB2472168B; GB201018620D0

Abstract

A medical instrument 1200 comprises a force transducer operable to apply a predetermined force at a position selected from an array of predetermined possible positions 1205 as a stimulus to a test area of a body part, such as the feet, of a patient. The instrument comprises a detector operable to detect a location of the test area of the body part with respect to a current position of the force transducer and the array of predetermined possible positions. A translation element moves the force transducer to one or more positions in the array closest to the location of the test area as detected by the detector. The instrument includes a sample surface 1201 against which the body part of the patient may be placed; the sample surface comprising the array of predetermined possible positions 1205. The detector is operable to detect regions of the sample surface which correspond to a position of the body part with respect to the sample surface. The detector is operable to detect regions of the sample surface which are in physical contact with the body part and to generate a pressure map indicative of pressure at those regions of the sample surface which are detected as being in physical contact with the body part. The instrument is preferably used to apply stimulus force to the surface of the feet for diabetic neuropathy testing.

Description

FORCE TRANSDUCER, MEDICAL INSTRUMENT, AND MACHINE IMPLEMENTED

METHOD

The present invention relates to a force transducer, medical instrument, and machine implemented method.

11. 11 _it-O1/ :__.-,-,4-However, given the apparent variability in fibre length and diameter of the monofilament, in addition to the differences in crystalline structure between grades of nnlvrnide and ahove all, the material's suscentibility to changes in humidity (hydroscopic In a third aspect, there is provided a machine implemented method of detecting an increased risk of diabetic neuropathic ulceration using a force transducer operable to apply a predetermined force to a test area of a body part of a patient, the method comprising: detecting a location of the test area with respect to a position of the force transducer; moving the force transducer to the location of the test area; applying a predetermined force to the test area using the force transducer; and recording whether a response is received from the patient regarding touch sensation at the test area, Accordingly, automated testing by applying a predetermined force to different target sites (test areas) may be carried out thus allowing a patient to selfmonitor for any degree of sensory neuropathy on a regular basis.

Further aspects and respective features of the invention are defined in the appended claims.

Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 shows a prior art monofilament testing device for testing for the presence of diabetic peripheral neuropathy in patients; Figure 2 shows a prior art monofilarnent with an applied lOg-force load with a deflection of 10mm; Figure 3 shows a plot of the mean buckling force in g4orce (i.e. lOmN) against the number of compressions of four commercially available prior art "1Ogforce load" mono filaments Figure 4 shows a schematic perspective view of a force transducer according to an embodiment of the present invention; Figure 5 shows a schematic cross-sectional view of a force transducer according to an embodiment of the invention shown in Figure 4; Figure 6 shows a schematic view of circuitry associated with the force transducer of Figure 4; Figure 7 shows a schematic view of a display and user controls associated with the force transducer of Figure 4; Figure 8 is a schematic view of a display in accordance with an embodiment of the present invention for indicating to a user a position at which the force transducer should be applied to a body part; Figure 9 shows the force transducer according to an embodiment of the invention being applied to the back of an operator's hand during initialisation of a test routine when a I Ogforce is applied; 1 - - 4+1--.

A force transducer, medical instrument, and method are disclosed. In the following description, a number of specific details are presented in order to provide a thorough nndergtindini nf embodiments of the oresent invention. It will he apparent however to a Preferably, the compression spring is precision wound and acts as a biasing element.

However, it will be appreciated that other suitable biasing elements could he used.

The actuator and sensor module 501 comprises a sensor 513 operable to detect a although it will he appreciated that other suitable fittings may be used. This enables the probe to be removed and replaced with a new and/or different probe. This improves hygiene and ;f rnacl w11 1irwrincr -iiffereiit sh2nel When an axial force is applied to the probe 407 (for example by pressing the probe 407 against a test area on a patient's foot), the axial force is translated to the compression in fl7 hrmi th cnmnyessipn snrinc 507 is in force transmittina communication with power from the power source 505 via the voltage regulator 603. The voltage regulator 603 is also operable to provide power to the actuator and sensor module 501 and to the display 409.

T1-nrinfr rri1 brd cn' kn o1ectriflv nnnootM to the disnlav 409 and the innut probe 407 is greater than a "pressure" threshold or whether the force is greater than an "over pressure" threshold.

The display 409 used in embodiments of the present invention is illustrated with respect to Figure 7.

1 1 1 I ArC All fll mi ii The CPU 605 then compares the generated force value with the pressure threshold value and the overpressure threshold value to detect whether the generated force value is rpter thrni these values In the embodiments described with reference to Figures 4 to 7, the being applied to the probe 407 as well as being operable to control the bar chart indicator 705 and the threshold marker so as to indicate a proportion of the threshold force which is 1x11n( ginEptj f flip irnh 407 This enables a user to annlv the force Drobe to a test indicating to a user that the probe should be applied to the calcaneurn of the patient's left foot.

The test procedure will be described in more detail later below, As described above, the force transducer 401 may also be used in an active mode in -. -. 1 1 1 4\1 is sent from the CPU 605 to the actuator and sensor module 501 via the actuator controller 609.

For example, if the probe is displaced axially with respect to the nose 405 and the 1-r mrn f1,pn th fnre inn1ieA tn the nrnhe 407 is 49rnN (Se. Therefore in provided so as to indicate that the predetermined force has been applied between the probe 407 and the housing.

The CPU 605 can then cause the display 409 to request from the user an indication, 1 1 1 4 1 I 1 4-n4- 1n1,+ f1t *h illuminated green (passive mode). Alternatively, in the active mode, the operator applies the tip 517 of the probe 407 to back of their hand so as to displace the probe from the preload position. The force transducer then placed in a supine position, and should remove any shoes and hosiery, allowing a clinician ready access to the plantar surface of both feet.

When the force is applied to the plantar surface of the foot in a random maimer to the weight hearing points (referred to as test areas or test sites), the patient is asked to say "yes", if any sensation is felt during the process. The clinician should not prompt the patient at any time, but should note any abnormal response. The patient's responses, both positive (ic.

"yes") and negative can be recorded on a data collection sheet.

Areas of callus are to be avoided during testing. If callus does exist at the test site, an alternative area located distally (towards the toes) from the original should be sought.

Furthermore, areas of poor tissue vitality and/or open lesions are also to be avoided.

Once the test has been carried on a patient the used tip should be discarded in a suitable clinical waste dispenser.

Figure 11 shows a flow diagram for operating the force transducer 401 in the passive mode.

In a Step Si, the tip 517 of the probe 407 is brought into contact with the plantar surface of the patient's foot at one of the selected weight bearing sites, as shown in Figures lOB to 1 OC. The probe 407 is brought into contact with the plantar surface of the foot perpendicular the plantar surface.

In a Step S2, the force transducer is moved towards the patient's foot by the operator (i.e. clinician) at a rate of approximately 10mm s1, which is translated into a force being applied to the plantar surface of the foot. As the force is applied, the force loading on the weight bearing site is indicated by the force transducer 401 on the display 409.

In a Step S3, the illumination state of the visual indicator (i.e. the LED) is monitored to see it if is green. If the LED is not illuminated green, then the process flow jumps to a Step SlO. If the LED is illuminate green, then the process flow jumps to a Step S4.

In a Step S4, the response to the applied load at the selected weight bearing site is noted. Both positive and negative responses are noted.

In a Step S5, the pressure is released from the force probe, thus removing the loading from the weight bearing site.

In a Step S6, if all of the selected weight bearing sites have been tested the process flow jumps to Step 8. If there are still weight bearing sites that are untested, the process flow jumps to a Step Si, In a Step S7, all of the selected weight bearing sites are tested and the procedure is terminated. The force probe can then be switched to off. Once the test has been carried out on fl th Qhr111C1 h d rded in sutah1e linicn1 waste disnenser, test sites on, for example, a patient's foot, Figure i 2 shows a floor mounted test device 1200 (medical instrument) upon which a patient may place a selected body part, such as one or both f rrrr n'iiye,nit1w Th +kirr mniintM test devic'e I 700 cornnrises a Figure 14 shows a plan view of the force transducer 1305 mounted on a translation stage 1401. The translation stage 1401 comprises a pair of xrai1s 1403 and pair of yrai1s 1 flfl A11 iinir rnn nffhe fcrce trnsjimer 1 05 is cantured between the xrails 1403 and Figure 16 is a schematic diagram of functional units of the floor mounted test device 1200 illustrated in Figure 12. In particular, Figure 16 shows a power source 1601 which is (nnnec',tM in i vo1tae reii1ator 1603 via a main nower switch 1605. The voltage used. A user interacting with the user transponder 1701 and the floor mounted test device 1200 is illustrated in Figure 18.

Figure 18 shows a schematic view of a patient using the floor mounted test device - +-T 1 2 The CPU 1609 is then operable to detect, by analysis of the pressure map, a location of suitable test areas with respect to the through holes of the pressure sensing matrix 1201 so +r, lic,t effpf ttd In FmlhfldjrnellfS of the nresent invention. this is If. at the step S 140, the signal from the user transponder 1701 indicates that there was a positive patient response to the stimulus provided by the predetermined force applied by the 1,rv, L- flT I I iZrfl, iifr n t1ifrn i fb In an embodiment, at the step S200, the CPU may cause the display 1617 to display an indication prompting the user to indicate whether they would like the correlation log to be trcrnsmitted tn an external device such as a nersonal computer or analysis server. The user may range of 5g to 50g (49mN to 49OmN), although it will be appreciated that any or all of the above described embodiments could be used to apply any suitable force as appropriate, subject to the necessary modifications. it will be appreciated that, where a force is referred to in terms of grams (g), what is meant is the force which would be exerted if an object having that mass were allowed to accelerate freely under the force of gravity. In other words, Fma (according to Newton's second law of motion), where m is the mass of the object, and a 9.8 ms2 so as to give the force in Newtons (N).

Furthermore, in the above described embodiments, the material of the nose of the force transducer is selected so as to provide a coefficient of friction which is substantially constant between the static regime and kinetic regime. Therefore, the predetermined force can typically be applied with a tolerance of �5%.

CLAUSES

1. A force transducer comprising: a handle operably connected to a probe having an elongate tip; a biasing element arranged with respect to the handle, in force transmitting communication with the probe; a detector operable to detect a degree of force applied between the probe and the handle; and an actuator operable to exert a force on the biasing element in dependence upon the degree of force detected by the detector so as to cause a predetermined force to be transmitted from the handle to the probe.

2. A force transducer according to clause 1, comprising a sensory indicator, the force transducer being operable to actuate the sensory indicator when the predetermined force is transmitted from the actuator to the probe.

3. A force transducer according to clause 2, in which the handle is a housing and the probe is movable through an aperture in the housing so that a first end of the probe extends outside the housing and a second end of the probe remains inside the housing.

4. A force transducer according to clause 3, in which the biasing element is arranged with respect to the housing and the probe so that the first end of probe is biased away from the housing.

5. A force transducer according to clause 3 or 4, in which the detector is operable to: detect a relative displacement between the second end of the probe and the aperture; and detect an amount of force being applied between the first end of the probe and the handle in dependence upon the detected relative displacement.

6. A force transducer according to clause 5, in which the force transducer is operable to cause the sensory indicator to output a signal when a force greater than an overload force is applied between the first end of the probe and the handle, the overload force being greater than the predetermined force.

7. A force transducer according to any of the preceding clauses, comprising an actuator controller operable to control the amount of displacement between the probe and the biasing element so as to cause the predetermined force to be transmitted from the actuator to the probe; and a user input operable to allow a user to define a value indicative of the predetermined force to be transmitted from the handle to the probe.

8. A force transducer according to any of the preceding clauses, comprising a display operable to indicate to a user a position on a patient's body to which the probe should be applied.

9. A force transducer according to clause 8, in which the display is operable to display an indication of the amount of force being applied between the probe and the handle.

10. A force transducer according to any preceding clause, in which the detector is operable to: detect motion of the probe with respect to the handle; and cause power to be supplied from a power source to the force transducer in dependence upon the detection of motion of the probe with respect to the handle.

11 A force transducer according to any preceding clause, in which the biasing element is operable to exert a preload force on the probe which is less than the predetermined force.

12. A medical instrument comprising: a force transducer operable to apply a predetermined force at a position selected from an array of predetermined possible positions as a stimulus to a test area of a body part of a patient; a detector operable to detect a location of the test area of the body part with respect to a current position of the force transducer and the array of predetermined possible positions; and a translation element operable to move the force transducer to one or more positions in the array closest to the location of the test area as detected by the detector.

13. An instrument according to clause 12, comprising: a sample surface against which the body part of the patient may be placed, the sample surface comprising the array of predetermined possible positions; in which the detector is operable to detect regions of the sample surface which correspond to a position of the body part with respect to the sample surface.

14. An instrument according to clause 13, in which the detector is operable to detect regions of the sample surface which are in physical contact with the body part and to generate a pressure map indicative of pressure at those regions of the sample surface which are detected as being in physical contact with the body part.

15. An instrument according to clause 14, in which the detector is operable to detect the location of the test area with respect to the sample surface by detecting regions of pressure of the pressure map which have a pressure greater than a threshold pressure.

16, An instrument according to clause 15, in which the detector is operable to control the translation element so as to cause the force transducer to move to respective locations in the array of predetermined possible positions which substantially correspond to a plurality of respective test areas of the body part as indicated by analysis of the pressure map.

17. An instrument according to any clauses 12 to 16, comprising a vibrating element arranged so as to apply vibrations to the body part as a stimulus to the body part.

18. An instrument according to any of clauses 12 to 17, comprising a receiver operable to receive, from a user input device associated with the patient, a signal indicative that the patient is aware of the stimulus provided by the instrument.

19. An instrument according to clause 18, comprising a user input device associated with the patient, the user input device being operable to transmit, to the receiver in response to input by the patient, the signal indicative that the patient is aware of stimuli provided by the instrument.

20. An instrument according to clause 18, in which the detector is operable to generate a correlation log indicating a correlation between reception of the stimulus signal and administration of the stimulus provided by the instrument.

21. An instrument according to clause 20, in which the controller is operable to generate the correlation log in respect of correlation between stimuli administered by the instrument at a plurality of test areas of the body part and the associated stimulus signals received from the user input device.

22. An instrument according to clause 20 or 21, comprising a memory operable to store the correlation log for analysis by a user.

23. An instrument according to any of clauses 20 to 22, comprising a transmitter operable to transmit the correlation log to an analysis server for analysis.

24, An instrument according to any of clauses 12 to 23, in which the body part of the patient is a foot of the patient, and the test area corresponds to a region on a plantar surface of the patient's foot.

25. An instrument according to any of clauses 12 to 24, in which the force transducer is a force transducer in accordance with any of clauses 1 to 9.

26. A machine implemented method of detecting an increased risk of diabetic neuropathic ulceration using a force transducer operable to apply a predetermined force to a test area of a body part of a patient, the method comprising: detecting a location of the test area with respect to a position of the force transducer; moving the force transducer to the location of the test area; applying a predetermined force to the test area using the force transducer; and recording whether a response is received from the patient regarding touch sensation at the test area.

27. A method according to clause 26, comprising carrying out the method in respect of a plurality of selected test areas.

28. A method according to clause 26 or 27, in which the test area or selected test areas are on plantar surfaces of the patient's feet.

29. A method according to any of clauses 26 to 28, in which the force transducer is operable to apply the predetennined force at a position selected from an array of predetermined possible positions and the force transducer is moved to one or more positions in the array closest to the detected location of the test area.

30. A method according to any of clauses 26 to 29, in which the force transducer is a force transducer according to any of clauses 1 to 9.

31. A method according to any of clauses 26 to 29, in which the method is carried out using the instniment according to any of clauses 12 to 25.

32. Use of a force transducer according to any of clauses 1 to 9 in detection of an increased risk of diabetic neuropathic ulceration.

33. Use of a medical instrument according to any of clauses 12 to 25 in detection of an increased risk of diabetic neuropathic ulceration.

34. A force transducer substantially as hereinbefore described with reference to Figures 4 to 11 of the accompanying drawings.

35. A medical instrument for detecting an increased risk of diabetic neuropathic ulceration substantially as hereinbefore described with reference to Figures 12 to 20 of the accompanying drawings.

36. A machine implemented method for detecting an increased risk of diabetic neuropathic ulceration substantially as hereinbefore described with reference to Figures 4 to 20 of the accompanying drawings.