CA2037089A1

CA2037089A1 - Testing the fit of a prosthesis socket

Info

Publication number: CA2037089A1
Application number: CA002037089A
Authority: CA
Inventors: Eduard Horvath
Original assignee: Eduard Horvath; Otto Bock Orthopadische Industrie Besitz- Und Verwaltungs Kg; Verwaltungs-Kg
Current assignee: VERWALTUNGS-KG; Otto Bock Orthopadische Industrie KG
Priority date: 1990-02-28
Filing date: 1991-02-26
Publication date: 1991-08-29
Also published as: JPH04220252A; BR9100806A; US5127420A; ATA47690A; AT393954B; CN1056411A; EP0449799A1

Abstract

Abstract of the Disclosure The service characteristics of a prosthesis shaft for a limb stump projecting from a pivotal articulation of a patient are determined by first fitting the shaft while engaged over the limb stump into a holder pivotal about a holder axis and then aligning the holder axis so that it generally traverses the articulation. The shaft and holder are then moved by the stump pivotally about the axis to establish extreme positions of the holder that cause discomfort to the patient. Movement within the extreme positions is established as an actual-value range and compared with a desired-value range. Then the fit of the shaft on the stump is adjusted and the first three steps are repeated until the actual-value range generally corresponds to the desired-value range. Normally the holder is pivotal about two generally perpendicular and coplanar holder axes and the intersection of the axes being set generally at the articulation.

Description

~}3 ~

1802 i TESTING THE FI~ OF A PROST~ESIS SOCKET

~EE5~~

Field o~ the Inventlon The present invent~on relate~ to a method of and apparatus for testing the fit o~ a prosthesis soc~et. More pa~ticularly this invent~on concerns a system for determining the useful move~ent range o~ a prosthesis socket on a limb st~mp for ad~usting the fit of the socket.

Xn the c~n truct~on ~f prosthesas, in particular false leg~, there are a variety o~ techniques. The primary cons~derations are of cour~e both technical and cosmetic.
Ahead of ever aspect, however, the main conslde~ation i5 service characteri~tic~, namely whe~her th~ device is comfortable and functions, ~ince if it does no~ satisfy both these requirement~ the patien~ will not use the pro~thesi~.

w 1 --2~3 '1'Q'~`~

1802~

Typically the conetruction of false l~mbs 15 the domain of special~sts whose decislons are ln part based on intuitlon and in part on experience. Even when compu~er ~echnology i5 applied to the pro~lem o~ artif~cial-lim~
de~ign, it i~ normally left to the designe~ to make up the most important part, namely the socalled soc~et shaft that fits over the patient's stump. Thl~ part must ~lt so that on the one hand it can ~upport the load of the limb and/or of the patient, but also so that when the stump is moved through ~he full normal ran~e o~ movement, it rema~ns comfortable. ~ypically the fitting of the socket entail~ a lengthy proces~ where the patient's ~ub~ective impress~ons o~ sUCCes~iYe ad~ustments to the fit are followed, along with direct ~bservation~ by the maker o~ the device.
At best su~h procedures are haphazard~ success~ve adju~tments of socke~ fit are freguently of~ the mark and sometimes even make thQ dev~ce less ~omfortable or reduce ~he useful range o~ t~e limb.

It is therefore an ohject of the pre~ent invent~on to provide an improved me~hod o~ and apparatus for determining the ~ervice characteristic~ for ~ pros~hes~ 5 ~haft ~or a lim~ stump.

2037~

Another object lS the provision of such an improved method of and apparatu~ for determinlng ~he servlce ~haracterlstic~ for A pros~he~ haft for a limb stump which overcomes the above-given dlsadvantages, that is which allows one to accuratel~ ~n~ 6cientlfi¢ally determine the rela~ionship between the ~it of the socket and the ran~e of movement that it will provide with a given fit.
A further ob~ect is to provide an improved system that allows a socket to b~ perfectly fit to ~ patient whlle giving him a near perfect or ideal range o~ movement of ~he limb to eventually ~e built on the socket.

Summarv o~ the In~ntion According ~o the invention the limb s~ump is inserted into the prosthesis shaft whiCh has a ~ocket a~c~mmodating the stump and which 1~ adapted to receive the pro~hetic mechanism. The prosthesis shaft, receiving the limh stump, is ¢arried by a support device ad;usted ~o be swingable about an axis, preferabl~ ~wo mutually in~ersecting and especially mutuall~ perpend$cular axes, wherein the axis or the intersect~on point of the axes correspond in locatio~ to a center region of the natural ~oi~ o~ tho limb o~ the th~ust point thereof. Thereaf~e~
~he pros~hesis sha~t is moved by mean~ of the s~ump and the limits o~ mobilit~ of the ~haft wh~ ch do not result in pain ~aused by the pre~sure of the ~oc~et of the ~haft again~t `~

the stump are determlned. ~ se llmlts ~an be obtalned a~
coordinate values of a boundary of an actual value mobility range whieh is compared with standardized setpoin~ value~
o acceptable ranges to determine de~iations be~ween the actual and setpoint values. Then the shaft soc~et ls altered so as to reduce these deviations be~ween the actu~l values and setpoin~ values of shaft mobility.
Thus, a method of determining the ~ervice characteristics of a pro~thesis ~ha~ ~or a llmb 6tump pro~ecting from a pivotal a~ti~ulation of a patient according to ~he invention c~mprises f irB~ f ittlng the shaft while engaged over the limb ~tump into a holder pivotal about a holder axis and then aligning the holder a~i~ 60 that it generally t~aver6es the articulation. The lS shaf~ and holder a~e then moved by the stump pivota~ly a~out ~he axi~ to e6t~bli~h extreme positions of the holder that c~se discomfort to the patient. Movem~nt within the extreme positions is e~tablished as an actual-value ran~e and compared with a desired-valu~ range. Then the ~it o~
~0 the ~haft on the ~tump i-~ adjusted and the first three step~ o~ ing, all~in~, and tes~ing by moving are xepeated untll the actual~v~lue range generally corresponds to the desired-value range. Normally according to the invention the holder ~s pivot~l about two generally perpendicular and coplan~r holder a~es and the ~ntersection of ~he axe~ belng ~et generally at the articulation.

With this procedure, therefore, the range o~
movement oP the socket ~ tested and all ~he patlent need comment on is how the socket feels in any given po~ition.
~hus ~he patient ~ove~, ~or ex~mple, his upper-leg ~u~p forward un~il it can go no fux~her or until it i~ impeded ~y ~he socket, and this pocltion ~s marked. Then this is repeated for backw~rd, side-to-side, and all other movement~ for th~ stump ~o a~certain exactly what types of motion are inhibited ~y the socket. Onae thi~ is dsne the m~ker can shave ma~erial of~ or add material ~o ~he socket in the appropriate place~ in a scienti~ic manner, without a~fecting po~tions o~ the so~ke~ that are giv~ng no problems. The~e is no general ~uestion o~ comfort of ~eel, in~tead ~he pat~ent need merely recpond at a given point in ~he movement range ~o whether he or ~e is being impeded or hurt by the socket. Of cours~ i~ the patient i5 able to move to a given desired-value position, this aspect o~ the ~ocket i6 no~ in ne~d of ad~u~tment. The de~i~ed-value xan~e ~tself aan be empi~ically derived and typically compri~ a region on the flsor wher~ the ~oot o~ the patient would normally land during wal~lng.
~n order to comp~ete ~he prostheses ~he mechanical element~ o~ the pros~eses are then construc~ed on th~
~haft accordin~ to the data deri~ed a~c~ding to the method of this invention, whereby anomalies such as ~or exampl~ a bow-le~ged or knock-kneed condition can be taken in~o account. The pros~hesis ~an be provided with correcti~ns t~ a. ~ ra ~.~ o 2 ~ ~, ?` ' ~

ao27 ~y mea~s o~ a ~nown auxiliary device ~i.e. a digitizer, I can generate digitallzed data providing a computer-true description of the 6tump bed or ~haft so~ket, pr~fera~ly in An orien~ation of ~he ~haft ln whlch tho a~tual-v~lue curve i~ determlned.
The limits of movement are ~herefore that an~le to which the ~haft can be ~oved wl~hout paln for the patient~
Use of the method allows the patient to input to the measurin~ ~ystem, witho~t infl~encing or observing the resultQ, his pain feellngs ~o that ~he limit~ o~ the pxostheses are established in the re.levant movement di~ections with greater scien~ific preaision.
The apparat~ for ~ar~ying out this method comprises a base, normally one on which the patient stand~ and that is provided with a support ~olumn carrying th~ plvotal holder~ Sensors are provided for detecting pivoting o~ the holder about it~ axe~ and the po~ition o~ the holder when pl~oted relative to the ba~e and for generating output~
~orresponding there~o and some mean~ iB provided for registerlng ex~reme position~ when the holder causes di~aomfort to the patient, typically in the form o~ a handle or grip th~ patient move~ ln theee extreme positions. ~ compu~er-type con~roller is connected to the sen~or means and to the mean~ for registering for ~stablish~ng ~o~ement within ~he e~reme positlons as ~n actual-value range and ~omparing it with a desired-value range in accordance with a pre~et pro~ram. Then o~ cour6e the fit of the shaft on ~he stump can ~e ad~usted untll the ~r~r~ r~ n~ t~ t~e 180~7 According to a feature o~ thi~ invention the holder include~ an inner par~ pivotal about one o~ the axes on the base and an outer part pivotal a~out the ~ther of the axes on the inner part. The ~older ~urther includes a seat ~nugly engagea~le aro~nd the shaft and the ~eat can be shifted and po~itioned on the outer part, typieally by means of a pair of transversely oriented cross ~lides.
Furthermore the seat i9 pivotal on the lnner part abo~t a third axis general~y perpendicular ~o the plane o~ the fir~t t~o axes at the inter8ect~0n thereo~.
At least one sensor iQ provided on at least one of the part~ or producing an output cor~esponding to the rot~tion of the respeotive par~ about ~he respective axis ~o that the exact angular position at which the patient ~tarts tb experience disaomPort can be ac~urately ~etermined. F~rthermore 6ens~rs can include means for detectlng the tor~ue applied by the patient to tne holder in the extreme positions, Thus ~he ~ontroller can know how much pressure the patlen~ i3 exertlng on shaf~ at any o~
its critiG~l extreme positions. In thia manner it is pos~ible to determin~ ~ust how much force the patient must exext ln ~ particular po~ition to experience discomfort or pain, thereby ~urther dellmiting the effe~tive range o~ a given sha f t.

!

According to a iurther feature o this invention a b~ake, typically a brake (or braXe generator) and~or a motor i~ conne~ted to ~ le~st one of the part~ for inh~bit~ng and/or ef~ecting rotation thereof about the respective axis. Thi~ ma~es it pos~ihle to accurately imitate ~he forces which apply ln actu~l use o~ the prosthe~io limb.
The motor at the relatlvely rotata~le parts at an a~is or the motors between the relatively xotatable parts At the respective axes permit the requ~site movements una~sisted by the patient and the brake or brakes can be used to e~tablish the torques required at each axis ~ox movement in the respective direction or to hinder ~uch movement. Meana can be ~d~ltlonally provided for imparting ~hock loa~ to the shaft.
Further according to this invention the ba~e o~ the appar~tus is provided with me~n~ ~or weighing the patient and th~ support is equipped with means for measuring the amo~nt o~ for~e the patient bear~ down on ~he ~upport with~ ~hu~ the amount of weight being applied to the s~aft, whiGh should periodically be the patien~ ntire weight, can be monitored~ In order to, ~or in~tance, simul~te the shock of walking, a device is provided for administering 6hoaks to the suppo~t. Thi~ device delivers upward blows to the support so that they are transmitted therethrough to the sh~ft. Such shocks can correspond to the shocks transmitted ~o the leg when the shoe strikes the ~8021 ~he above and other objects, features, and advantages will become more readlly apparent from the following, re~erence being made to the acco~panying drawing in which:
FIG~ 1 is a pa~tly d~agrammatic lsome~ric view o~
the apparatus for carrying out the method of the inve~tion;
FIG. 2 is a top vlew partly in se~tion taken along line II ~ Or Fig. 1:
~o FIG. 3 is ~ large-Qcale ~ertical section showing ~he socket holder of thi~ lnventions and FIG. 4 is a block diagram of a clrcuit used with the appara~us o~ FIGS. 1 - 3.

Spe~i~ic ~e~ ion As seen in the drawing a socket 1, here intendPd to receive an upper-leg 5tump, iB seaured in a holde~ 2 itself carried on an outer L-~haped support a~m 3 suspended from a curved bracket 16 carried on a main ~upport arm 4. The bracket 16 and axm 3 can ~vot about a normally horizon~al axis 5 relative to the arm 4 and thi6 arm 4 can in turn pivot about a normally horizontal ~xis 6 perpendicular to the axi~ 5 on a 6~ppoxt slide 7. A base plate ~ has an uprish~ column ~ to which the 61 ide 7 is ~ecura~le a~ ~ny o~ a mul~iplicity of vertically o~set position~.

~ ~ ~ O ~ ~J ~,f 1~027 The holder arm 3 is connected as seen in Fig. 3 to 51ide block lo in whi~h the arm 3 can move vertically and can be locked in any posttion by ~crew~ 17. Th~ block 10 can also slide hoxizontally al~ng the bracket 1~ and be 5 locked in position by another ~U~h screw 18. The holder 2 has a colla~ 47 that ~an ~e tigh~ened around ~he ~ocket ~haft 1 and a seat 49 into which the end of the socket 1 is seated. This holder 2 is pivo~al about a vertical axis ll on the support arm 3 but ls connected thereto via two mutually perpendicular cross sllde~ 13 and 14 intercon-necting an uppe~ plate 12a havlng the ~eat 4~, and intermediate plate 12~ connected via the side-to-side cross slide 14 to the plate 12a, and a lowe~ plate 12c oonnected the front-to-~ack cros~ slide 13 to the intermediate plate l2b and itself p~otal on the lower end of the arm 3 about the axis ll. Respect~ve ad~ustmen~ screwR such a~ ~hown at 50 fo~ the ~llde 13 are provided for relatively ~etting the positions of the cross slides 13 and 14.
Re~pective sensors l~, 20, and ~1 are provided ~or determining the ~ngular posltions o~ the arm 4 relative ~o ~he axis ~ a~d the holder 2 relative to the axe~ 5 and 11.
The outputs fxom these 6ensor~ 19, 20, and 21 are fed via xespe~tive line~ 2Z, ~3, and 24 to a ~ont~oller indicated sch~matically at ~8 in ~g~ 1. In addi~lon a ~otor and/or bra~e 25, 26, and ~7 i8 assoc~ted w~th eac~ o~ ~hes~
~ensors lg, 20, and 21 ~or e~fectin~ or retard~ng rotatlon ~ v ~3 ~ `

about the respective ax~s 5, ~, and 11. These devices 25, 26, and 27 are in turn assooiated with tor$ue aensors 31, 32, and 33 connected v~a lines 34, 35, and 36 to the controlle~ 48 to supply samè with output~ indlcatlng ~he force ~pplied relati~e ~o the rèspecti~e axes.
The base plate 8 is constructed as a ~cale with a weight 6ensor 45 conneoted to the controller 48, and pendant handles 43 ~nd 44 are provided that hang f~om the top of the column above and to elther slde o~ the ~upport 2. These handles 43 and 44 are also con~tituted as sensors which can be ~ueezed by the u5er to furnish an output to the controller 48 as described below.
The slide 7 iB ~onnected via link5 37, 38, 39, and 40 to a ~uppor~ 41 on whiah the pivot for the arm 4 a~out the axis 6 le carried. The link~ 37 through 40 ~orm parallelogrammatic linkage~ whlch permit limited vertical movement of ~he support block 4~ relative to the ætationary slide 7. A com~ined ~en60r and shoc~ generator 15 is provided on the ~lide 7 to detect the vertical po~ition of th~ block 41 rela~ive to the ~lide 7 a~d the weight being appl~ed d~wnward to the block 41 and ~o furnieh an ou~put corresponding thereto via a lin~ 42 to the ~ontroller 48.
The sen~or lS als~ functions ~ a ~hock generator ~or transmit~in~ shocks t~ ~h~ so~ket shaft 1 ~ia the arm 4.
2S The shock generator i~ thus fixed on tho column ~ or on the ~lide 7 an~ i5 supplied with ele~trical energy f~om a ~our~e 15~ in order to transmit ~h~cks vla the ~lock 41 h~ ; C ~ ~V ~e~ns of a verticallv displaceable pln ~J~c ~

In FIG. 4 I ha~e shown, in bloc~ diagram form a circuit which can be used wlth the system o~ FIGS. 1 - 3.
The ~ontroller ox computer ~8 ha~ ~nputs 50 representing the sensor ou~puts of the apparatu~ and oUtpUtB 51 to the motors or generating torque about the axe~ and to ths shock-pulse generator 15. An additional input 52 represents the pain signal transmit~ed by the patient when experiencing pai~.
The computer 48 i~ connected with a scanner 53 by m~ans of which a ~etpo$nt movemen~ ~race 54, v~ible on a monitor display 55, ~an be inputted. ~ata as to the setpoint latitude~ of movement in any direction can also be inputted b~ a keyboard 56 and a printer 57 can display data obtained by the apparatu~ and correction~ of the socket which may be i~dicat~d. The Computer i~ a~sociated with a memory 58 which can 6tore e~pixically derived data equating a particular dif~e~ence in coo~dinate~ of a ~etpoint and a~tual value with ~ particular correction ln the shape of the stump socket~ Thus if the actual value trace 5~ is obtained, for a spe~ifi¢ moment ve~tor 60, the actual value point ~ can have the cooxdinate~ (n, n ) whereas ~he cor~espondin~ ~etpo$nt ~ would have the coordina~e~
(n ~ e, n ) in pola~ ~oordin~te-~. The difference e is determined b~ the com~uter and the p~in~out would indicate that a correotion e would require modification o~ the socket at a part~¢ular l~cation and to a given de~ree to increase mobility ln that direction. After reshaping of the socket the measurement can be repeated as will be 2 ~ rJ ~

In u~e a patlent P stand~ with his or her good le~
on the plate ~ ~acing ~orward along a vertical symmetry plane ~ bisecting the column 9 and perpend~cular ko the axl~ 5. The patlent'~ stump is ~itted in~o his or her own ~ocket 1 which is clamped in the holder 2 that is ad~usted via the screws 17, 18, and 50 until it is in a comfortable and natural po~ition with the axi~ 6 extending through ~he patient's hip joint. The patient P a~plies weight to the ~ocke~ 1 and c~n in fact support his or her entire weight thereon, which ~act can readily be determi~ed by compar~ng the weiqht readout of th~ ~ensor~ 15 and 45 tha~ are connected to the controller 48.
Once thus in place the patient P moves his stump and ~he socket 1 from front to back and from ~ide to side, al~
of which movement~ are of ~ouxse pivoted on ~ point 0 lying at the interse~tion of the ~xes 5 And 6 ln thc pati~nt~
hip ~oint. Whenever thç patient P experiences dlscom~ort he or she pushes the handle~ 43 apart to signal this to the ~ontroller 4~.
20 Thus ~he con~roller 48 will be a~le to determine the po~ition a~ which movemen~ in any directlon ~ecomes uncomfortable, and the force being exerted by the patient P
at this pos$tlon on the s~aft 1. The controller 4~ is therefore able to establlsh an im~gina~y pro~ection or field I tFl~. 2) ~orrespond~ng to the actual ~omfortable range of movement fox the pa~ient, and compare it to another such field S that represents the desired maximum ~`
1~027 movement range. When the actual-~alue field I is short of the desired-value field S thi~ i8 an indication that ~he socket l is binding the patient and lnhibiting his or her movemen~. ~hus the socket l can be wor~ed on, either s having material removed or added as appropriate, and the test can be xerun to determlne if the ~orrection actually does improve the range o~ movement. To ~tart with, the a~tual-value field I is normally centered ln the desired-value field S by ad~ustment of the screws 50 and o~
~ourse the block 10 i8 adjusted to set the point O right in the patient'~ h~p artlculatlon. Th~s 6tart~n~up a~justment also help6 later ~ett~n~ of the position o~ the socket 1 in the leg prosthesis to ~e ~Uil~.
Clearly this arrangement can also ~e adapted for use with other limbs. In the case, for $nstance, o~ use with lower-~r~ ~tump, the center 0 ls set at the el~ow and o~
course th~ axe~ 5 and 6 are set to corre~pond to normal arm movement~.

Claims

1. A method of determining the service characteristics of a prosthesis shaft for a limb stump projecting from a pivotal articulation of a patient, the method comprising the steps of:
a) fitting the shaft while engaged over the limb stump into a holder pivotal about a holder axis;
b) aligning the holder axis so that it generally traverses the articulation;
c) moving the shaft and holder by means of the stump pivotally about the axis and establishing extreme positions of the holder that cause discomfort to the patient;
d) establishing movement within the extreme positions as an actual-value range and comparing it with a desired-value range; and e) adjusting the fit of the shaft on the stump and then repeating step a) through c) until the actual-value range generally corresponds to the desired-value range.

2. The method defined in claim 1 wherein the holder is pivotal about two generally perpendicular and coplanar holder axes, the intersection of the axes being set in step b) generally at the articulation.

3. An apparatus for determining the service characteristics of a prosthesis shaft for a limb stump projecting from a pivotal articulation of a patient, the apparatus comprising:
a base:
a holder provided with means for snugly holding the prosthesis shaft while engaged on the stump of the patient;
means supporting the holder on the base for pivoting thereon about two generally perpendicular and coplanar axes;
means for aligning the intersection of the holder axes so that they generally traverse the articulation of the patient whose limb stump is fitted to the shaft engaged in the holder;
sensor means for detecting pivoting of the holder about its axes and the position of the holder when pivoted relative to the base;
means for registering extreme positions when the holder causes discomfort to the patient; and control means connected for the sensor means and to the means for registering for establishing movement within the extreme positions as an actual-value range and comparing it with a desired-value range, whereby the fit of the shaft on the stump can be adjusted until the actual-value range generally corresponds to the desired-value range.

4. The apparatus defined in claim 3 wherein the holder includes an inner part pivotal about one of the axes on the base and an outer part pivotal about the other of the axes on the inner part.

5. The apparatus defined in claim 4 wherein the holder includes a seat snugly engageable around the shaft and the means for aligning includes means for shifting and positioning the seat on the outer part.

6. The apparatus defined in claim 5 wherein the seat is pivotal on the inner part about a third axis generally perpendicular to the plane of the first two axes at the intersection thereof.

7. The apparatus defined in claim 5 wherein the means for shifting includes a pair of transversely oriented cross slides.

8. The apparatus defined in claim 4 wherein the sensor means includes at least one sensor on at least one of the parts for producing an output corresponding to the rotation of the respective part about the respective axis.

9. The apparatus defined in claim 4 wherein the sensor means includes means for detecting the torque applied by the patient to the holder in the extreme positions, the torque-detecting means being connected to the control means.

10. The apparatus defined in claim 4, further comprising brake means connected to at least one of the parts for inhibiting rotation thereof about the respective axis.

11. The apparatus defined in claim 4, further comprising motor means connected to at least one of the parts for rotating same about the respective axis.

12. The apparatus defined in claim 4 wherein the base is equipped with means for weighing the patient and the support is equipped with means for measuring the amount of force the patient bears down on the support with.

13. The apparatus defined in claim 4, further comprising means for administering shocks to the support.

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