Method and apparatus for physiological testing

CA 02534366 2006-02-06

WO 2005/013821

PCT/AU2004/001038

Method and apparatus for physiological testing

Field of the Invention

This invention relates to a method and apparatus for measuring the performance of human joints.

Background of the Invention

The present invention is concerned with measuring the performance of a joint or combination of such in the human body and, in particular, to measuring the effort exerted by a patient during the performance testing process.

When persons suffer injuries in accidents such as those which commonly occur in the workplace, and in road traffic accidents, it is usually necessary for the extent of the injured person's injuries to be determined in order to assess the correct amount of compensation which may be payable to the injured person as a result of the accident. Typically the compensation payable will be related to the extent of the person's injuries and the loss of use or performance of parts of the person's body due to the accident. For example, if a person injures their arm in an accident the compensation payable will depend on the extent to which that person's use of their arm has been impaired. Further, an accurate assessment of an injury allows a rehabilitation programme to be monitored and varied if necessary.

However, there is currently no satisfactory repeatable scientific method of assessing a person's joint performance to determine to what extent the performance of the joint has been impaired due to injury or accident or the like. Currently, most injuries are assessed subjectively by doctors or physiotherapists. The assessment process is generally unscientific and open to inaccuracies. One particular problem occurs when patients pretend to be more seriously injured than they are for example by pretending to be unable to do particular tasks or by only providing a sub-maximal effort when tested.

This is a major problem for organisations which provide insurance payments related to injuries, particularly insurance companies.

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A further related problem arises, in that since it is not possible to accurately measure joint performance, it is not possible to accurately measure improvement in joint performance. Thus if a patient is undergoing physiotherapy or other treatment for injuries associated with a joint it is not, for example, possible to accurately plot 5 improvement or lack of fit in the joint on a week by week basis.

The present invention aims to provide a device for repeatedly and accurately measuring the performance of a joint in the body and which preferably includes means for determining whether the patient whose joint performance is being measured is 10 making a minimal or at least sub-maximal effort, when tested.

Throughout this specification the word comprise, or variations such as comprises or comprising, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of 15 any other element, integer or step, or group of elements, integers or steps.

Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is solely for the purpose of providing a context for the present invention. It is not to be taken as an admission that any or all of 20 these matters form part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed before the priority date of each claim of this application.

Summary of the Invention

In one aspect, the present invention provides a device for performance testing comprising:

a moveable member;

a sensor for measuring force applied to the moveable member; and a resistance means to vary the resistance to movement of the moveable member.

The moveable member may be a shaft or a lever.

Where the moveable member is a shaft, the shaft may be rotatable. In this 35 embodiment, the sensor may comprise a torque sensor for measuring torque applied to the shaft.

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The resistance means may comprise a coupling means that variably couples the shaft to the torque sensor. Such variable coupling of shaft and torque sensor varies the resistance to the turning of the shaft. An example of such a resistance means is an electric brake, eddy coupling, servo motor or the like.

Where the resistance means comprises a coupling means, typically the resistance is variable between a state where there is no coupling and no resistance is applied and the shaft is free to rotate relative to the torque sensor and a state in which the shaft is fully coupled to the torque sensor.

It is preferred that the device includes an encoder for measuring the position of the shaft. The device may also include a control means for receiving input data from the torque sensor. The control means may also be arranged to input control signals to the resistance means and to determine the relationship between the resistance applied to the shaft and the torque measured by the torque sensor. Further, the control means may receive signals from the encoder in relation to the angular position of the shaft.

In a further aspect, the present invention provides a device for performance testing comprising:

a shaft;

a torque sensor for measuring the torque applied to the shaft; and a coupling means for variably coupling the shaft to the torque sensor to vary the resistance to turning of the shaft.

Where the moveable member comprises a lever, said lever may be connected to a resistance means. The resistance means may comprise a pump member. The pump member typically has a control valve to vary resistance to the lever. Further, the pump member of this embodiment may be connected to a sensor, said sensor measuring the force applied to the lever. The sensor may comprise a pressure gauge to measure the pressure change of fluid in the pump as force is applied to the lever.

In one broad related aspect, the present invention provides a method of sincerity of effort testing of a person's joint performance by repeatedly measuring the response of that joint to a varying load.

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More specifically, the present invention provides a method of measuring the torque applied to a shaft by a person's joint comprising the steps of:

applying a varying resistive force to turning of the shaft; measuring the torque applied to the shaft;

recording the resistive force applied; and measuring the relationship between the resistive force applied and the measured torque.

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Brief Description of the Drawings

A specific example of the present invention will now be described by way of example only and with reference to the accompanying drawings in which:

Figure 1 is a schematic drawing of a device for repeated performance measuring to gauge sincerity of effort; and

Figures 2 and 3 are graphs comparing the resistive load applied to the device 10 against measured torque.

Detailed Description of a Preferred Embodiment

Referring to the drawings, the device generally indicated at 10, includes a 15 rectangular box-like casing 12. One side of a torque sensor 14 is mounted to one interior wall 15 of the casing. Fixed to the opposite side of the torque sensor 14 is a mounting plate 16 defining a central hole 18 through which one end of an elongate shaft 20 extends. The end of the shaft 20 is free to rotate relative to the mounting plate and the torque sensor 14. The shaft 20 extends from the mounting plate 16 co-axial 20 with the torque sensor 14 and defines a free end 21 which projects through an aperture 22 defined in a wall 24 of the casing opposite to the wall 15 to which the torque sensor 14 is mounted.

The free end 21 of the shaft 20 defines a coupling 26 which can be attached to various joint testing interfaces for testing any joints or combinations of such which can be used to produce rotary motion about an axis, which most if not all joints are capable of.

A brake stator coil 28 defining a central bore 30 which is of greater diameter 30 than the shaft is fixed to the mounting plate 16. The shaft 20 extends through that central bore 30. A brake rotor 32 is mounted on the shaft 20 and defines a friction surface 34 facing the brake stator coil 28 and in conjunction with the brake stator coil 28 defines an electric brake. Increasing the current supplied to the brake rotor 32 increases the resistance between the brake rotor 32 and the brake stator coil 28 and 35 hence the coupling between the two. When the current is a maximum and the brake is fully on any torque applied to the shaft 20 is transmitted directly to the torque sensor

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14. When the brake is fully disengaged, the shaft 20 spins freely and no torque is applied to torque sensor 14. A shaft encoder 36 mounted on the wall 24 of the casing measures the angular position of the shaft 20.

A computer control means in the form of a micro .controller 50 is connected to the torque sensor 14 and the shaft encoder 36 and receives input signals indicative of the torque measured by the torque sensor and the angular position of the shaft as measured by the shaft encoder. The micro controller also controls the current applied to the electric brake via a feedback loop.

When a torque is applied to the shaft 20 to turn the shaft in the direction A, that torque is measured by the torque sensor 14.

It will be appreciated that the device 10 works by using the brake rotor 32 and brake stator coil 28 to provide increasing resistance to the turning of the shaft 20 about its longitudinal axis which is measured by the torque sensor 14. The resistance can be quickly and accurately controlled by varying the current applied to the brake rotor 32. The torque applied to the shaft 20 is measured by the torque sensor 14 and this therefore gives a measurement of the performance of a patient's joint or combination.

The performance of virtually any joint can be measured using a flexible rope and a capstan fitted to coupling 26 to monitor movement of the joint.

However, simply measuring the performance of the joint as described above, by measuring the torque a joint may generate will not measure true joint performance unless a patient is trying as hard as they can i.e. giving maximal effort. Also simply measuring performance based on application of a fixed load does not provide an indication of the sincerity of effort that a patient is applying to the task.

Thus, in order to make it more difficult to misrepresent the true performance test by making a sub-maximal effort, in a particularly preferred embodiment, the computer control means 50 is programmed to vary the resistive load provided by the electric brake, whilst the shaft 20 is being turned by the patient. This makes it much more difficult for a patient to misrepresent the test since whilst it is relatively straightforward to decide to make a 50% effort, say, when moving against an unchanging resistance, when the resistance changes continuously, the patient is unable to accurately and

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PCT/AU2004/001038 quickly calculate the changing level of effort they need to apply to be consistent with their original level of effort.

The system thus varies the resistive load applied to the electric brake, changing the resistance to turning of the shaft by the patient. The device 10 measures the torque applied to the shaft 20 by the patient and correlates the measured torque with the resistance applied to the turning of the shaft 20..

The device 10 rapidly varies the resistance to the turning of the shaft 20 during a single exercise performed by the patient. Thus, if the patient is asked to, say, pull his/her fist up to his shoulder, in that one movement, the resistance to the turning of the shaft would vary several times.

Several patterns of resistance may be applied including sinusoidal, saw tooth and non-uniform patterns. The patterns depicted in Figures 2 and 3 are of a step change nature.

With reference to Figure 2 for a patient who is making a 100% effort each time, the relationship L between the measured torque 52 and the resistance applied 54 is shown to be fairly constant. If however, a patient is attempting to cheat the test by making only a 50% effort, then they will not be able to maintain that sub-maximal 50% effort consistently as the load is varied and a greater variation/standard deviation in the relationship L of the measured torque and the resistive force will be measured, as shown in Figure 3. The tests may also be repeated, with variations in the patient's performance further indicating sub-maximal effort.

The variation of the resistive load may be based on position of the shaft as measured by either the encoder or time. The variation may be continuously varied for example by a ramped load or a stepped load or both. The variation may be increasing or decreasing or consistent stopping.

The electric brake may be replaced by an equivalent element such as an eddy current coupling or similar controlled coupling device or servomotor. Further, the method of providing a variable resistance could be a hydraulic motor or actuator with a variable flow control so that the oil flow could be restricted to provide a controlled resistive torque.

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The system may be active or passive. For example, in an active system, the resistive electric brake could be replaced by a variable torque servo drive.

Because the device provides a repeatable way of measuring joint performance, it is possible to measure improvement in joint performance, for example, the performance of an elbow could be measured on a weekly basis and increases in the strength and range of movement of the joint performance measured and tracked.