WO2012077142A1

WO2012077142A1 - Method of analysis of the movement particularly of the walk of a person

Info

Publication number: WO2012077142A1
Application number: PCT/IT2010/000490
Authority: WO
Inventors: Michele Raggi; Andrea Giovanni Cutti
Original assignee: I.N.A.I.L. Instituto Nazionale Per L'assicurazione Contro Gli Infortuni Sul Lavoro
Priority date: 2010-12-07
Filing date: 2010-12-07
Publication date: 2012-06-14
Also published as: WO2012077142A8

Abstract

A method of analysis of the movement, particularly of the walk of a person, which consists in importing, in a step a., into an electronic processor a set of calibration parameters (Hth, Lth, NC) which comprises at least a first calibration parameter (Hth), a second calibration parameter (Lth) and a third calibration parameter (NC), and these calibration parameters (Hth, Lth, NC) are related to the movement of a leg of a person; subsequently, the method according to the invention detects, in a step b., moment (i) by moment (i), the respective value of the speed of rotation (D(i)) of the leg of the person about its lateral center axis, by means of an apparatus that is provided with suitable detection means and is associated with the processor, for a period of analysis, which corresponds to at least one footfall (p) of the person; lastly, the method according to the invention consists, in a step c, in determining, also in real time and on the basis of the speed values (D(i)) acquired and of the calibration parameters (Hth, Lth, NC), at least the moment of contact (IC_p) of the foot of the leg with the ground, for each of the footfalls (p) performed by the subject during the period of analysis.

Description

METHOD OF ANALYSIS OF THE MOVEMENT PARTICULARLY OF THE WALK OF A PERSON

Technical Field

The present invention relates to a method of analysis of the movement, particularly of the walk of a person.

Background Art

In the areas of clinical diagnostics, rehabilitation, legal medicine and sport, it is of considerable importance to be able to precisely measure the moment of initial contact of the foot with the ground and the moment of the final detachment, for example in order to detect any asymmetries during the walk between the movement of the left leg and that of the right leg.

Such asymmetries, in fact, can be the cause of the onset of various pathologies in persons. In the first place therefore the above mentioned analysis is very useful for any individual (including anyone who practices sports at amateur or professional level). In addition, the identification of any asymmetries becomes absolutely crucial for patients who are missing a limb, and for whom it is necessary to correct these problems (which have arisen following the adoption of a prosthesis simulating the missing lower limb), since asymmetries cause unwanted overloads on the healthy limb and considerably increase the risk of falling.

According to known methods, the detection of the above mentioned events is entrusted to what are known as "force platforms", i.e. platforms installed in the floor of a suitably equipped laboratory and provided with force sensors of various different types, which can thus detect the essential moments of the walk of a patient, who moves on the laboratory platform.

This solution is not, however, without drawbacks.

These platforms are very expensive to make and run, which strongly limits their application. Moreover, the possibility of using such solutions is further reduced by the difficulty (or impossibility) of transporting the platforms from one place to another. In addition, it should be noted that the reduced dimensions of the platform allow the measurement of only one foot/ground contact, which is often not sufficient for a correct analysis of the movement of a patient.

These problems have been partially remedied by applying force sensors or limit markers directly onto the patient, which are able to communicate the trajectory executed by the foot to computerized processors, which in turn are provided with suitable algorithms for determining such moments starting from the trajectories identified.

These solutions are also, however, not without drawbacks.

The use of force sensors worn by the patient brings with it problems of hygiene, and it also requires a considerable amount of calibration work on the specific person to be analyzed. What is more, such sensors are easily subject to breakage and wear and they do not provide information on the aerial phase of the walk (i.e. the phase during which the foot is not in contact with the ground).

Add to this the fact that, when resistive sensors are used (these are also known as "FSRs", for "Force Sensitive Resistors"), repeatability of the measurement is poor. By contrast, if capacitive sensors are used, these are very expensive and are often bothersome to the patient because they have a minimum thickness.

For a pathological walk disorder (for example drop foot or toe shuffling), the sensors may require complex protocols for their positioning.

It should also be noted that the adoption of limit markers (which are potentially ineffective in pathological populations) does not permit analysis in real time and requires a spatial sampling of such markers, which are moreover applicable in a very limited acquisition space.

Disclosure of the Invention

The aim of the present invention is to solve the above-mentioned problems, by providing a method that can simply and cheaply detect and determine the parameters relating to the walk of a person. Within this aim, an object of the present invention is to provide a method that can be adapted substantially automatically to the specific patient analyzed and recognize any pathologies of the patient.

Another object of the invention is to provide a method that can detect and provide the data required both in real time and at a later time.

Another object of the invention is to provide a method that makes it possible to analyze the walk and the movement of the patient cheaply and without using complex support instrumentation.

A further object of the invention is to provide a method that can be easily obtained from elements and materials that are easily sourced on the market.

A further object of the invention is to provide a method that ensures a high level of reliability in operation.

This aim and these objects are achieved by a method of analysis of the movement, particularly of the walk of a person, which consists in importing into an electronic processor a set of calibration parameters which comprises at least a first calibration parameter, a second calibration parameter and a third calibration parameter, said calibration parameters being related to the movement of a leg of a person; in detecting, moment by moment, the respective value of the speed of rotation of the leg of the person about its lateral center axis, by means of an apparatus that is provided with suitable detection means and is associated with said processor, for a period of analysis, which corresponds to at least one footfall of the person; in determining, also in real time and on the basis of the speed values acquired and of said calibration parameters, at least the moment of contact of the foot of the leg with the ground, for each of the footfalls performed by the subject during the period of analysis.

Brief description of the drawings

Further characteristics and advantages of the invention will become better apparent from the detailed description that follows of a preferred, but not exclusive, embodiment of the method according to the invention, illustrated by way of non-limiting example in the accompanying drawings, wherein:

Figure 1 is a block diagram that illustrates the method according to the invention;

Figure 2 is a block diagram that illustrates in detail a first step of the method according to the invention;

Figure 3 is a block diagram that illustrates in detail the step of determining the moment of contact;

Figure 4 is a block diagram that illustrates in detail a portion of the step of determining the moment of contact;

Figure 5 is a block diagram that illustrates in detail a further step of the method according to the invention;

Figure 6 schematically shows the trend of the speed of rotation of the leg as a function of the moment of detection.

Ways of carrying out the invention

With reference to the figures, the method according to the invention, which is schematically illustrated in Figure 1, makes it possible to analyze the movement of a person (whether healthy or affected by various pathologies), and in particular it makes it possible to obtain useful information and data (the significant moments in time) relating to the walk of such person.

These data make it possible to define and study the movements of the person and to identify any problems associated with the way in which he or she walks and in which he or she moves or places his or her limbs on the ground.

The method according to the invention consists, in a first step a., in importing into an electronic processor a set of calibration parameters Hth, Lth, NC which comprises at least a first calibration parameter Hth, a second calibration parameter Lth and a third calibration parameter NC: these calibration parameters Hth, Lth, NC, for which at least two different methods of determination will hereinafter be described, are related to the movement of a leg of a person and make it possible to analyze its kinematics, thus identifying any anomalies, in particular in the flexion of the knee, that are such as to make a different calibration necessary of the method described.

The method further consists in detecting, in a step b., at each moment (indicated with the letter "i"), the respective value of the speed of rotation of the leg of the person about its lateral center axis, such speed being indicated with the notation D(i): such detection is effected by virtue of an apparatus that is provided with suitable detection means (some of which are illustrated hereinbelow) and is associated with the electronic processor mentioned previously.

It should be observed that the electronic processor can be provided with means for converting the analog signal which is provided by the detection means into a digital signal.

The trend of the value of the speed of rotation of the leg, measured for example in radians per second, can be represented on a chart with Cartesian axes, thus obtaining substantially the trend illustrated in Figure 6.

The detection occurs for a period of analysis, which can be established and/or extended at will, and which corresponds to at least one footfall (indicated with the letter "p" hereinafter) of the person.

With the speed values D(i) and with the calibration parameters Hth, Lth and NC it is thus possible, in a step c, to determine at least the moment of contact ICp of the foot of the leg with the ground, for each of the footfalls p performed by the person during the period of analysis.

According to the preferred embodiment, the method consists, in the step c, in determining, also in real time (differently from what happens with the methods of the known type) and based on the speed values D(i) acquired and on the calibration parameters Hth, Lth, NC, both the moment of contact ICp of the foot with the ground and also at least the moment of detachment TC_P of the foot from the ground, for each of the footfalls p performed by the subject during the period of analysis.

The moments IC_P and TC_P thus detected (which constitute the two significant moments, and are representative of the walk of the patient), for each of the footfalls p performed by the person, thus make it possible to conduct, according to known methods, various different analyses: as mentioned, these significant moments, in fact, make it possible in the first place to develop studies of the movement of the person (and in particular of his or her walk), for example in order to identify anomalies or pathologies in the contacts with the ground, and this is of considerable interest especially (but not only) for individuals who are missing a limb, in order to highlight asymmetries in the movement, which are potential causes of overloading on the healthy limb and therefore of future pathologies.

Furthermore, the determination of the moments IC_P and TC_P (related to a succession of footfalls p) ensures the possibility of conducting analyses of sporting movements (in order to optimise performance, thus playing a role of considerable interest in professional or semiprofessional circles) of the ascent and descent of stairs.

In addition, it is possible to use the above data for electromyographic analyzes, for the general monitoring of activities performed by the analyzed person (known as "activity monitoring"), for bio-functional electrical stimulation applications (known by the acronym "FES"), and for biofeedback applications.

Lastly, the above data are particularly important to, and can therefore be advantageously used in, all protocols and applications of clinical, functional and biomechanical analysis, where it is necessary to know the moments IC_P and TC_P. The practical utility of such protocols and applications is however currently limited by the limits of the solutions of the known type. According to a . first embodiment of the method according to the invention, the set is loaded into a memory unit which is comprised in the electronic processor (in order to then be imported in the step a. and used for determining the data described above) and it is obtained by means of a preliminary analysis on a plurality of persons who are chosen by sampling populations of normally-endowed persons and otherwise.

Such preliminary analyses, conducted by the applicant, can for example lead to sets that contain the following values (which are cited purely for the purposes of non-limiting illustration of the embodiment of the method according to the invention):

Hth = 1.5;

Lth = -1 ;

NC = 6 samples (with sampling frequency of lOOHz).

Alternatively, according to a second embodiment of the method according to the invention, such method consists, before executing the step a. of importing, in executing a procedure d. of calibration (illustrated in detail in Figure 2) that is specific to the person to be analyzed, in order to calculate calibration parameters Hth, Lth, NC that are peculiar to the person upon which the analysis is conducted and which are obtained, as will be better illustrated hereinbelow, as a function of the trend over time of the speed of rotation D(i). This procedure d. of calibration, which is obtained by means of the detection, moment i by moment i, of the respective value of the speed of rotation D(i) of the leg, is continued for a predefined calibration period, which corresponds to the execution by the person of a predefined number n of footfalls p.

Thus by making the subject perform a number n (preferably but not exclusively equal to 5) of footfalls p, it is possible to obtain calibration parameters Hth, Lth, NC for his or her specific way of walking, so that the subsequent analyses will be capable of providing results that take account of the person's specific characteristics. Obviously each set thus identified can be stored in a specific memory unit, so as to be reused at a later time in order to conduct further analyses on the same patient (or possibly in order to conduct analyses on different persons, who have similar physical structures, if it is not desired to repeat the calibration procedure d.).

Alternatively, as previously observed, such set can be based on preset values, which are identified and considered to be valid for most of the population.

Usefully, the calibration procedure d. consists, in a first step dl ., in acquiring, for each of the footfalls p performed by the person during the calibration period, a threshold moment i^swk in which the speed of rotation D(i) of the leg of the patient exceeds a predefined first threshold value SW1. This first threshold value SW1 is preferably equal to 2 rad/sec, but the possibility is not excluded of fixing a different value for it, as a function of the specific requirements.

Subsequently, the calibration procedure d. consists, in a step d2., in acquiring, for each of the footfalls p performed by the person during the calibration period, a zero moment i^zck, after i^swk, in which the value of the speed of rotation D(i) drops below 0.

It is thus possible to calculate, in a step d3., and for each of the n footfalls p performed by the subject during the calibration period, an interval of time Atk, preferably defined as

(with k assuming all the values comprised between 1 and n-1).

Based on the above-mentioned intervals of time Atk, the method then consists, in a step d4., in determining a first time window TWf_0rward and a ^•second time window TWbackward, which are respectively defined as TWforward=average(Atk)*0.2 and TWbackward=average(At_k)*0.3 (with k assuming all the values comprised between 1 and n).

Proceeding with the calibration procedure d., such procedure then consists in identifying, in a step d5., for each of the footfalls p performed by the person during the calibration period, a first local maximum LMk, a first local minimum Lmlk and a second local minimum Lm2k. The first local maximum LMk is defined as the maximum value assumed by D(i) between the threshold moment i^s and the zero moment i^zck, the first local minimum Lmlk is instead defined as the minimum value assumed by D(i) between the zero moment i^zck and the moment i that is equal to i^zck+TWf_orward, and lastly, the second local minimum Lm2k is defined as the minimum value assumed by D(i) between the moment i that is equal to i^zck-TWbackward and the zero moment i^zck, with k assuming all the values comprised between 1 and n.

For each of the first local maxima LMk, of the first local minima Lml_k and of the second local minima Lm2k, it is possible to obtain, in a step d6., the respective average values, which are correspondingly defined as LMm=average(LMk), Lmlm=average(Lmlk), Lm2m=average(Lm2k), with k assuming all the values comprised between 1 and n.

The calibration procedure d. thus makes it possible to compose, in a step d7., the desired set of calibration parameters (Hth, Lth, NC) based on the average values LMm, Lmlm and Lm2m and on the exceeding, by the Lm2m/Lmlm ratio, of a second predefined threshold value SW2, which is representative of the kinematic behaviour of the lower limb when placed on a surface, and in particular of the kinematics of the knee and of its capacity for flexion.

This second predefined threshold value SW2 is preferably (but not exclusively) equal to 1.55, and its being exceeded denotes a reduced capacity for flexion of the knee (and for this reason, as can be seen from the following paragraphs, the formulae used are varied), while a Lm2m/Lmlm ratio that is less than 1.55 is associated with a condition of flexion of the knee that is substantially physiological.

More specifically, for values of the Lm2m/Lmlm ratio that are higher than the second predefined threshold value SW2, the step d7. of composing the set consists in defining the calibration parameters Hth, Lth, NC preferably as Hth=LMm*0.5, Lth=Lm2m*0.6 and NC=average(At_k)*0.47, with k assuming all the values comprised between 1 and n. Differently, for values of the Lm2m/Lmlm ratio that are lower than the second predefined threshold value SW2, the composition step d7. consists in defining the calibration parameters Hth, Lth, NC preferably as Hth=LMm*0.5, Lth=Lm2m*0.57 and NOaverage(At_k)*0.5, with k assuming all the values comprised between 1 and n.

Based on the calibration parameters Hth, Lth, NC (which are calculated according to the methods shown above or are obtained from analyses of a sample population), it is thus possible, as mentioned previously, to determine in the step c. (which is shown in detail in Figure 3) at least the moment of contact IC_P, for each footfall p performed by the person.

In particular, the determination step c. consists in repeating a succession of operations for each footfall p, the first of which (defined as cl .) consists in waiting for the elapsing of an initial transition period, in order to then identify, in a step c2., the desired moment of contact IC_P with the first moment i wherein at least one of the following two conditions is met:

D(i)>D(i-l),

|(D(i-l)-D(i))/D(i-l)|* 100<ICth_;

with ICTh which is a fixed parameter and is preferably chosen to be equal to 5 and in any case can be reconfigured at will.

After having identified, in step c2., the moment of contact IC_P, the method consists, in a step c3., in observing, with the processor, a wait period of length equal to NC (or in waiting an equivalent number of samples of the signal D(i)).

According to the previously mentioned preferred embodiment, for each footfall p performed by the person during the period of analysis, at the end of the respective step c3. of observing a wait period, the method according to the invention consists in waiting, in a step c4., for the value of the speed of rotation D(i) to be less than Lth, in order to then identify, in a step c5., the moment of detachment TC_P, for each footfall p performed by the person, with the first moment (i-3) which simultaneously verifies the following four conditions:

100*|(Ρ(ΐ-3)|-Ρ(ΐ-2)|)|/|Ο(ΐ-3)|>ΤΟ_ώ1 ,

100*|(|D(i-2)|-|D(i-l)|)|/|D(i-2)|>TOt_h2,

100*i(|D(i-l)|-|D(i)|)|/|D(i-l)|>TO_th3,

D(i)>D(i- 1 )>D(i-2)>D(i-3).

It should be noted that TO_thl is a first characterization constant of the behaviour of the leg and preferably assumes a value equal to 1 , ΤΟ¾2 is a second characterization constant of the behaviour of the leg and preferably assumes a value equal to 5, and TOth3 is a third characterization constant of the behaviour of the leg and preferably assumes a value equal to 10.

Such characterization constants can therefore be obtained following analysis and optimisation of the trend over time of the speed D(i) signal.

More specifically, the above mentioned step cl . of waiting for the elapsing of a transition period (which is illustrated in detail in Figure 4) consists, in a step cla., in maintaining the electronic processor in a state of waiting for the value of the speed of rotation D(i) to be higher than Hth. Subsequently, the method consists in checking, in a step clb., for the presence of at least three consecutive detections of the value of the speed of rotation D(i) that are higher than Hth. If this does not occur, then the method according to the invention repeats the step of maintaining the wait state cla. (and the following steps).

When the step clb. has a positive outcome, the method waits, in a step clc, for the value of the speed of rotation D(i) to assume a value of less than 0 in order to consider as terminated the step cl . of maintaining the wait state, and pass to the the subsequent operations, which are described in the preceding paragraphs. Of the steps described above, it moreover appears evident that, by means of the method according to the invention, it is possible to arrive at the determination of the moment of contact IC_P and of the moment of detachment TC_P (for each footfall p) also in real time, thus achieving a result that is entirely new in respect of the solutions and methods of the known type.

Usefully, the method according to the invention comprises a procedure e. of checking and recahbration, which is shown graphically in an embodiment thereof in Figure 5: the procedure e. of checking and recahbration can be executed automatically by the electronic processor, in order to check and update, continuously and in real time, during the period of analysis of the person, the calibration parameters Hth, Lth, NC which were initially determined.

In particular, according to a possible embodiment, at each footfall p performed by the person during the period of analysis, the checking and recahbration procedure e. consists firstly in saving, in a step el ., the values of the speed of rotation D(i) in a suitable transit memory region SWb (also known as buffer) of the electronic processor.

Subsequently, and at the end of the respective step cl . of waiting for the elapsing of the transition period, the checking and recahbration procedure e. consists in storing, in a step e2., a respective second local maximum Ζ(¾ which is defined as the maximum value recorded in the buffer SWb, in a first shift register ZCr which is comprised in the electronic processor: preferably, this first shift register ZCr is adapted to store preferably three values (the average of which will hereinafter be identified with average(ZCr)).

After having stored at least three values, on the first shift register ZCr (and therefore after the person has performed at least three footfalls p), then, in a step e3., the first calibration parameter HTh can be recalculated according to the formula Hth=average(ZCr)*0.5, in order to then delete, in a step e4., the data that are comprised in the buffer SWb.

Subsequently, the checking and recalibration procedure e. consists in storing, in a step e5. after each step c2. of identifying the respective moment of contact IC_P, the corresponding value of the speed of rotation D(IC_P) in a second shift register ICar which is comprised in the electronic processor, and this second shift register ICar is also adapted to store preferably three values (the average of which will hereinafter be indicated with average(ICAr)).

Furthermore, in a step e6., the value of the moment of contact IC_P is also stored in a third shift register ICTr which is comprised in the electronic processor; again, this third shift register ICTr is also adapted to store preferably three values.

After having stored three values in the third shift register ICTr (and therefore after having performed three steps c2. of identifying respective moments of contact IC_P and therefore after the person has performed three footfalls p), the checking and recalibration procedure e. consists, in a step el., in recalculating the third calibration parameter NC according to the formula:

NC=0.5*((ICTr₂-ICTri)+(ICTr3-ICTr₂))/2, for the values of the Lm2m/Lmlm ratio that are higher than the second predefined threshold value SW2.

If the value of the Lm2m/Lmlm ratio is instead lower than the second predefined threshold value SW2, then the third calibration parameter NC can be recalculated according to the formula:

NC=0.45*((ICTr₂-ICTr₁)+(ICTr₃-ICTr₂))/2.

Subsequently, it is possible to store, in a step e8. after each of the steps c5. of identifying the respective moment of detachment TC_P, the corresponding value of the speed of rotation D(TC_P) in a fourth shift register TCAr which is comprised in the electronic processor: this fourth shift register ZCr, too, is adapted to store preferably three values (the average of which will hereinafter be identified with average(TCAr)).

After having stored three values in the fourth shift register TCAr, it is possible to determine, in a step e9., a third predefined threshold value SW3, which is representative of the kinematic behaviour of the knee, and in particular of the capacity for flexion of the knee, and which is obtained, as can be seen from the foregoing explanation, directly from the footfalls p performed by the person up to that moment in the period of analysis.

In particular, the third predefined threshold value SW3 is preferably calculated according to the formula SW3=average(TCAr)/average(ICAr).

The third threshold value SW3 thus determined can thus be stored, in a step elO., in an area of binary memory that is comprised in the electronic processor. Subsequently, it is possible to recalculate, in a step el l ., the second calibration parameter Lth according to the formula Lth=average(ICAr)*0.6, for SW3>=1.55, or according to the formula Lth=average(ICAr)*0.57, for SW3<1.55.

Usefully, the possibility exists that the checking and calibration procedure e. consists, after the step el l . of recalculating the second calibration parameter Lth, in executing a diagnostic step el 2., which is aimed at checking for the presence of possible anomalies in the detected values of the calibration parameters Hth, Lth, NC: if such anomalies are found, the calibration parameters Hth, Lth, N are not updated (again, by means of an action in real time and for each footfall p performed).

The device according to the invention, for the analysis of movement, and in particular of the walk of a person, comprises an apparatus that is provided with means for detecting the instantaneous value of the speed of rotation D(i) of a leg of the person about its lateral center axis, for a period of analysis that corresponds to at least one footfall p of the person.

The apparatus is associated with an electronic processor, which is adapted at least to the determination, also in real time, of the moment of contact IC_P of the foot of the leg with the ground, for each of the footfalls p performed by the person during the period of analysis: such determination is executed as a function of a set of calibration parameters Hth, Lth, NC which comprises at least a first calibration parameter Hth, a second calibration parameter Lth and a third calibration parameter NC, with these calibration parameters Hth, Lth, NC being related to the movement of the leg of the person.

More specifically, the apparatus is associated with an electronic processor that is adapted, by virtue of the calibration parameters Hth, Lth, NC indicated above, to determine, also (and preferably) in real time, the moment of contact IC_P of the foot of the leg with the ground and at least to determine the moment of detachment TC_P of the foot from the ground.

Usefully, according to a first possible embodiment, the detection means comprise at least one gyroscopic sensor, which can be applied to the leg of the person and operatively associated with the electronic processor: such gyroscopic sensor is adapted to instantaneously detect the value of the speed of rotation D(i) of the leg of the person about its lateral center axis.

The choice to use gyroscopic sensors makes it possible to adopt a simple solution that can be easily implemented: the gyroscopic sensors can in fact be easily applied to the person to be analyzed and they do not cause him or her annoyance (given their reduced size and light weight).

Alternatively, according to a different embodiment, the detection means comprise a first device (a video camera for example) which is connected to the electronic processor, and is adapted to acquire images, and the like (and more generally any device that is adapted to provide images and similar measurements). It is thus possible to determine the value of the speed of rotation D(i), by means of the segmental kinematic analysis of the movement of the leg, such movement being acquired by means of such device.

This solution, too, is easily implemented, without being the cause of annoyance for the patient. The possibility also exists of using detection means that comprise a second device arid/or a third device, which are connected to the electronic processor, and are respectively adapted to measure the induced electromagnetic field and the acoustic response of an induced field, in order to be able to thus determine the value of the speed of rotation (D(i)) of the leg of the person, about its lateral central axis.

More specifically, both of the embodiments proposed (which do not exhaust the possible solutions that come under the scope of protection that is claimed herein) are not at all invasive, thus guarding against the danger of possible alterations of the measurements owing to, for example, functional limitations caused by the excessive encumbrance of the instrumentation used (as sometimes happens with the solutions of the known type).

Moreover, such embodiments feature low costs, high repeatability of measurement, high reliability (including in the long term, since they are not significantly subject to wear and breakage) and they do not require, for the electronic processor, high calculation power and/or a high number of instructions.

The electronic processor, which is comprised in the device according to the invention, is therefore adapted to implement the method that has been described in detail in the previous pages, for determining the moment of contact ICp of the foot of the leg with the ground and the moment of detachment TC_P of the foot of the leg from the ground, for each of the footfalls p performed by the person during the period of analysis.

The method according to the invention (and also the device according to the invention) thus makes it possible to detect and exactly measure (both in real time, and at a later time) the moment of contact IC_P of the foot of the leg with the ground and the moment of detachment TC_P of the foot from the ground: the data thus obtained can be used in diagnostics, rehabilitation, sport and legal medicine.

By means of the measurements described above, it is thus possible to perform assessments on the times of "step", "stance", "stride" and "swing", as well as on the variability and symmetry (between the two limbs) thereof.

In this regard, the term "step" (monopodalic support) is used to mean the phase of the walk of the person that intervenes between an initial contact (in a footfall p) and the subsequent controlateral initial contact (in a footfall p+1); the term "stance" (support) is used to mean the phase of the walk of the person that intervenes between an initial contact and the subsequent homolateral final detachment (in the same footfall p); the term "stride" (double support) is used to mean the phase of the walk of the person that intervenes between an initial contact (in a footfall p) and the subsequent homolateral initial contact (in the subsequent footfall p+1); the term "swing" (fly or fling phase) is used to mean the phase of the walk of the person that intervenes between a terminal contact (in a footfall p) and the subsequent homolateral initial contact (in the subsequent footfall p+1).

Such measurements (with the exception of measurements of symmetry) can moreover be executed both for both limbs, and for one only, and they can be obtained both for healthy patients and for pathological patients (for example unilateral transfemoral amputees).

The data can be collected in real time, while the person is still engaged in performing the footfalls p for the period of analysis, and such data can be obtained in any context, without requiring the analysis to be executed in a suitably equipped laboratory, since it is sufficient to fit out the subject, for example, with one or more gyroscopic sensors in order to permit the calibration and the subsequent analysis substantially in any environment (or alternatively to transport the image acquisition device described above to the chosen environment).

As illustrated, the method according to the invention usefully includes a calibration procedure d. (which runs, for example, for five footfalls p of the person), during which the data collected are used in order to determine specific values for the calibration parameters Hth, Lth and NC. It should be noted that the possibility exists of providing the electronic processor and/or the device according to the invention with audible and/or visual signalling elements in order to inform the patient and/or the operator that the acquisition of the required calibration parameters Hth, Lth and NC is concluded. Moreover, by means of a suitable interface which is associated with the electronic processor, the device according to the invention can provide information on the measurements made and on the correct outcome of the calibration procedure d., as well as the state of progress (partial number of footfalls p performed over the total number n planned) of the calibration procedure d. (or indeed the number of footfalls p performed during the period of analysis).

It should further be noted that all the time parameters of the method according to the invention are determined as a function of the sampling frequency, therefore it is not necessary to observe a pre-established sampling frequency.

In addition, as noted, the checking and recalibration procedure e. (which is subjected to diagnostics in order to assess the presence of anomalies) makes it possible to automatically adapt the method according to the invention to the walk of the patient: after having acquired the necessary data for the first three footfalls p performed, the electronic processor is capable of recognising, continuously and in real time, for example, the changes in pace and speed, modifying the calibration parameters Hth, Lth, NC as a consequence.

The possibilities of adapting the method according to the invention further extend, as has been seen in the previous pages, to also cover possible pathological conditions of the patient (such as for example reduced capacity for flexion of the knee), thus ensuring correct measurement in these cases too.

It is also advantageous to note that the parameters presented in the previous paragraphs, for example the predefined threshold values SW1 , SW2 and SW3 (but also the formulas themselves), can be manually reconfigured at will by the user.

In practice it has been observed that the method according to the invention fully achieves the intended aim and objects, in that the choice to detect, moment by moment, the value of the rotation speed of the leg of the person (patient), by means of an apparatus that is provided with suitable means of detection that are associated with an electronic processor, in order to then determine, on the basis of the values of the speed thus acquired and the previously imported calibration parameters, at least the moment of^" contact of the foot of the leg with the ground, for each of the footfalls performed by the person during the period of analysis, makes it possible to detect and analyze simply and cheaply the parameters relating to the walk of such person.

The invention thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the appended claims. In addition, all the details may be replaced by other, technically equivalent elements.

In the embodiments illustrated, individual characteristics shown in relation to specific examples may in reality be interchanged with other, different characteristics, existing in other embodiments.

In addition, it should be noted that anything found to be already known during the patenting process is understood not to be claimed and to be the subject of a disclaimer.

In practice the materials employed, as well as the dimensions, may be any according to requirements and to the state of the art.

Where the technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly, such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.

Claims

1. A method of analysis of the movement, particularly of the walk of a person, which consists in:

a) importing into an electronic processor a set of calibration parameters (Hth, Lth, NC) which comprises at least a first calibration parameter (Hth), a second calibration parameter (Lth) and a third calibration parameter (NC), said calibration parameters (Hth, Lth, NC) being related to the movement of a leg of a person;

b) detecting, moment (i) by moment (i), the respective value of the speed of rotation (D(i)) of the leg of the person about its lateral central axis, by means of an apparatus that is provided with suitable means of detection that are associated with said processor, for a period of analysis, which corresponds to at least one footfall (p) of the person;

c) determining, also in real time and on the basis of the speed values (D(i)) acquired and of said calibration parameters (Hth, Lth, NC), at least the moment of contact (IC_P) of the foot of the leg with the ground, for each of the footfalls (p) performed by the person during the period of analysis.

2. The method according to claim 1 , which consists in determining, in said step (c), on the basis of the speed values (D(i)) acquired and of said calibration parameters (Hth, Lth, NC), the moment of contact (IC_P) of the foot of the leg with the ground and at least the moment of detachment (TC_P) of the foot of the leg from the ground, for each of the footfalls (p) performed by the person during the period of analysis.

3. The method according to claims 1 and 2, characterized in that said set, which is loaded into a memory unit which is comprised in said electronic processor, is obtained by means of a preliminary analysis on a plurality of persons who are chosen by sampling.

4. The method according to claims 1 and 2, and in alternative to claim 3, which consists, before the step (a.) of importing, in executing a procedure (d.) of calibration, that is specific for the person to be analyzed, in order to calculate said calibration parameters (Hth, Lth, NC), by means of the detection, moment (i) by moment (i), of the respective value of the speed of rotation (D(i)) of the leg, for a predefined calibration period, which corresponds to the execution by the person of a predefined number (n) of footfalls (p).

5. The method according to claim 4, characterized in that said predefined number (n) of footfalls (p) is preferably equal to 5.

6. The method according to claims 4 and 5, characterized in that said procedure (d.) of calibration consists in:

dl . acquiring a threshold moment (i^sw _k) in which the value of the speed of rotation (D(i)) exceeds a first predefined threshold value (SW1), for each of the footfalls (p) performed by the person during the calibration period;

d2. acquiring a zero moment (i^zck), after said threshold moment (i^swk), in which the value of the speed of rotation (D(i)) drops below 0, for each of the footfalls (p) performed by the person during the calibration period;

d3. calculating, for each of the footfalls (p) performed by the subject during the calibration period, an interval of time (Atk), said interval of time (Atk) being preferably defined as

with k assuming all the values comprised between 1 and n-1 ;

d4. determining, based on said intervals of time (Atk), a first time window (TWforward) and a second time window (TWbackward), said first time window being defined as TWf_Orward⁼average(At_k)*0.2 and said second time window being defined as TWbackward=average(Atk)*0.3, with k assuming all the values comprised between 1 and n;

d5. identifying, for each of the footfalls (p) performed by the person during the calibration period, a first local maximum (LM_k), a first local minimum (Lml_k) and a second local minimum (Lm2k), said first local maximum (LMk) being defined as the maximum value assumed by D(i) between said threshold moment (i^sw _k) and said zero moment (i^zck), said first local minimum (Lmlk) being defined as the minimum value assumed by D(i) between said zero moment (i^zck) and the moment (i) that is equal to i^zck+TWforward, said second local minimum (Lm2k) being defined as the minimum value assumed by D(i) between the moment (i) that is equal to i^zV TWbackward and said zero moment (i^zck), with k assuming all the values comprised between 1 and n;

d6. obtaining, for each of said first local maxima (LMk), first local minima (Lmlk) and second local minima (Lm2k), the respective average values, which are correspondingly defined as LMm=average(LMk), Lmlm=average(Lmlk), Lm2m=average(Lm2k), with k assuming all the values comprised between 1 and n;

d7. composing said set of calibration parameters (Hth, Lth, NC) based on LMm, Lmlm and Lm2m and on the exceeding, by the Lm2m/Lmlm ratio, of a second predefined threshold value (SW2), which is representative of the kinematic behaviour of the lower limb when placed on a surface, and in particular of the kinematics of the knee and of its capacity for flexion.

7. The method according to claim 6, characterized in that said first predefined threshold value (SW1 ) is preferably equal to 2 rad/sec.

8. The method according to claim 6, characterized in that said second predefined threshold value (SW2) is preferably equal to 1.55.

9. The method according to claim 6, characterized in that, for values of the Lm2m/Lmlm ratio that are higher than said second predefined threshold value (SW2), said composition step (d7.) consists in defining said calibration parameters (Hth, Lth, NC) preferably as Hth=LMm*0.5, Lth=Lm2m*0.6 and NC=average(Atk)*0.45, with k assuming all the values comprised between 1 and n, for values of the Lm2m/Lmlm ratio that are lower than said second predefined threshold value (SW2), said composition step (d7.) consisting in defining said calibration parameters (Hth, Lth, NC) preferably as Hth=LMm*0.5, Lth=Lm2m*0.57 and NC=average(At_k)*0.5, with k assuming all the values comprised between 1 and n.

10. The method according to one or more of the preceding claims, characterized in that, for each of the footfalls (p) performed by the person during the period of analysis, said step (c.) of determining the value corresponding to the moment of contact (IC_P) consists in:

cl . waiting for the elapsing of a transition period;

c2. identifying said moment of contact (IC_P) with the first moment (i) wherein at least one between the condition D(i)>D(i-l) and the condition |(D(i-l)-D(i))/D(i-l)|* 100<ICth is met, ICth being a fixed parameter, preferably chosen to be equal to 5 and reconfigurable at will;

c3. observing, with the electronic processor, a wait period of length equal to NC.

1 1. The method according to claim 10, which consists, at the end of each of said steps (c3.) of observation of a wait period and for each of the footfalls (p) performed by the person during the period of analysis, in:

c4. waiting for the value of the speed of rotation (D(i) to be less than

Lth;

. c5. identifying, for each respective footfall (p) performed by the person, said moment of detachment (TC_P) with the first moment (i-3) wherein the condition 100*|(|D(i-3)|-|D(i-2)|)|/|D(i-3)|>TOthl is met, the condition 100*|(|D(i-2)|-|D(i-l)|)|/|D(i-2)|>TO_th2 is met, the condition 100*|(| D(i-l)|-|D(i)|)|/|D(i-l)|>TO_th3 is met, and the condition D(i)>D(i-l)>D(i-2)>D(i-3) is met, TOthl being a first characterization constant of the behaviour of the leg that preferably assumes a value equal to 1 , TO_th2 being a second characterization constant of the behaviour of the leg that preferably assumes a value equal to 5, TO_th3 being a third characterization constant of the behaviour of the leg that preferably assumes a value equal to 10.

12. The method according to claims 10 and 1 1, characterized in that said step (cl .) of waiting for the elapsing of the transition period consists in: cla. maintaining the electronic processor in a state of waiting for the value of the speed of rotation (D(i)) to be higher than Hth;

clb. checking for the presence of at least three consecutive detections of the value of the speed of rotation (D(i)) that are higher than Hth;

clc. waiting for the value of the speed of rotation (D(i)) to be less than 0.

13. The method according to claim 12, which consists, if said step (clb.) of checking has a negative outcome, in repeating said step (cla.) of maintaining the wait state.

14. The method according to one or more of the preceding claims, characterized in that it comprises a procedure (e.) of checking and recalibration, which can be executed automatically by said electronic processor, in order to check and update, continuously and in real time, during the period of analysis of the person, said calibration parameters (Hth, Lth, NC).

15. The method according to claim 14, characterized in that, for each of the footfalls (p) performed by the person during the period of analysis, said checking and recalibration procedure (e.) consists in:

el . saving, in a transit memory region (buffer) (SWb) of said electronic processor, the values of the speed of rotation (D(i)) detected;

e2. storing, at the end of each of said steps (cl .) of waiting for the elapsing of the transition period, a respective second local maximum (ZCrk), which is defined as the maximum value recorded in said buffer (SWb), in a first shift register (ZCr) which is comprised in said electronic processor, said first shift register (ZCr) being adapted to store preferably three values; e3. with three values stored in said first shift register (ZCr), recalculating said first calibration parameter (HTh) according to the formula Hth=average(ZCr)*0.5;

e4. deleting the data that are comprised in the buffer (SWb);

e5. storing, at the end of each of said steps (c2.) of identifying the respective moment of contact (IC_P), the corresponding value of the speed of rotation (D(IC_P)) in a second shift register (ICar) which is comprised in said electronic processor, said second shift register (ICar) being adapted to store preferably three values;

e6. storing the value of said moment of contact (IC_P) in a third shift register (ICTr) which is comprised in said electronic processor, said third shift register (ICTr) being adapted to store preferably three values;

e7. with three values stored in said third shift register (ICTr), recalculating said third calibration parameter (NC) according to the formula NC=0.45*((ICTr₂-ICTri)+(ICTr₃-ICTr₂))/2, for values of the Lm2m/Lmlm ratio that are higher than said second predefined threshold value (SW2), said third calibration parameter (NC) being recalculate according to the formula NC=0.5*((IC r₂-ICTri)+(ICTr₃-ICTr2))/2₉ for values of the Lm2m/ Lmlm ratio that are lower than said second predefined threshold value (SW2);

e8. storing, at the end of each of said steps (c5.) of identifying the respective moment of detachment (TC_P), the corresponding value of the speed of rotation (D(TC_P)) in a fourth shift register (TCar) which is comprised in said electronic processor, said fourth shift register (TCar) being adapted to store preferably three values;

e9. with three values stored in said fourth shift register (TCAr), determining a third predefined threshold value (SW3), which is representative of the kinematic behaviour of the knee, and in particular of the capacity for flexion of the knee;

elO. storing said third predefined threshold value (SW3) in an area of binary memory that is comprised in said electronic processor;

el l . recalculating said second calibration parameter (Lth) according to the formula Lth=average(ICAr)*0.6, for (SW3)>=1.55, said second calibration parameter being recalculate according to the formula Lth=average(ICAr)*0.57, for (SW3)<1.55.

16. The method according to claim 15, characterized in that said third predefined threshold value (SW3) is preferably calculated according to the formula SW3=average(TCAr)/average(ICAr).

17. The method according to claims 15 and 16, characterized in that said checking and recalibration procedure (e.) consists, after the step (el l .) of recalculating said second calibration parameter (Lth), in a diagnostic step (el 2.), for checking for possible anomalies in the detected values of said calibration parameters (Hth, Lth, NC).

18. A device for analysing the movement, and in particular the walk of a person, characterized in that it comprises an apparatus that is provided with means for detecting the instantaneous value of the speed of rotation (D(i)) of a leg of the person about its lateral center axis, for a period of analysis that corresponds to at least one footfall (p) of the person, said apparatus being associated with an electronic processor that is adapted at least to determine, also in real time, the moment of contact (IC_P) of the foot of the leg with the ground, for each of the footfalls (p) performed by the person during the period of analysis, said determination being executed as a function of a set of calibration parameters (Hth, Lth, NC) which comprises at least a first calibration parameter (Hth), a second calibration parameter (Lth) and a third calibration parameter (NC), said calibration parameters (Hth, Lth, NC) being related to the movement of the leg of the person.

19. The device according to claim 18, characterized in that said apparatus is associated with an electronic processor that is adapted, by virtue of said calibration parameters (Hth, Lth, NC), to determine the moment of contact (IC_P) of the foot of the leg with the ground and at least to determine the moment of detachment (TC_P) of the foot from the ground.

20. The device according to claims 18 and 19, characterized in that said detection means comprise at least one gyroscopic sensor, which can be applied to the leg of the person and operatively associated with said electronic processor, said at least one gyroscopic sensor being adapted to instantaneously detect the value of the speed of rotation (D(i)) of the leg of the person, about its lateral center axis.

21. The device according to claims 18 and 19, characterized in that said detection means comprise a first device, which is connected to said electronic processor, and is adapted to acquire images, for determining said value of the speed of rotation (D(i)) of the leg of the person, about its lateral center axis, by means of the segmental kinematic analysis of the movement of the leg, said movement being acquired by means of said first device.

22. The device according to claims 18 and 19, characterized in that said detection means comprise a second device, which is connected to said electronic processor, and is adapted to measure the induced electromagnetic field, for determining said value of the speed of rotation (D(i)) of the leg of the person, about its lateral center axis.

23. The device according to claims 18 and 19, characterized in that said detection means comprise a third device, which is connected to said electronic processor, and is adapted to measure the acoustic response of an induced field, for determining said value of the speed of rotation (D(i)) of the leg of the person, about its lateral center axis.

24. The device according to one or more of the preceding claims, characterized in that said electronic processor is adapted to implement said method,- for determining said moment of contact (IC_P) of the foot of the leg with the ground and of said moment of detachment (TC_P) of the foot of the leg from the ground, for each of the footfalls (p) performed by the person during the period of analysis.