WO2009118196A1

WO2009118196A1 - Test device for testing geometric properties of a prosthesis part

Info

Publication number: WO2009118196A1
Application number: PCT/EP2009/002272
Authority: WO
Inventors: Dirk Salomon
Original assignee: Mathys Ag Bettlach
Priority date: 2008-03-27
Filing date: 2009-03-27
Publication date: 2009-10-01
Also published as: DE102008015994A1; DE102008015994B4

Abstract

The invention relates to a test device (2) for testing geometric properties of a prosthesis part, which can be a shaft of a hip prosthesis for example, wherein the prosthesis part has a surface area (4) with a top surface and a cone surface (14). The test device (2) has a depression (10) with a side wall (6) which is shaped such that it defines a circular cone. The side wall (6) is provided for contact with the surface area (4) of the prosthesis part. Moreover, the test device (2) has first test means that are designed to detect the depth of insertion of the surface area (4) into the depression (10) in the contact state. The test device (2) can be used to test whether a specific head of a prosthesis is suitable for connection to the surface area (4) of the prosthesis part. On the depression (10) it is possible to provide an opening (12) at whose edge area a marking (20) is formed which indicates an upper limit and a lower limit of a depth of insertion suitable for connection between a specific head and the prosthesis part. Moreover, a tracing pin can also be provided, with the aid of which the cone angle (α), enclosed by the cone surface (14), can be detected.

Description

Testing device for testing geometric properties of a prosthetic part

The invention relates to a test device for testing geometric properties of a prosthetic part, which has a surface area with a top surface and a conical surface, wherein a straight truncated cone is defined by the top surface and the conical surface. Furthermore, the invention relates to a method for testing geometric properties of such a prosthesis part.

A modern hip endoprosthesis usually comprises a prosthesis part called a "shaft" designed to be inserted into a femur, and another part of the prosthesis called a "head" intended to replace a natural condyle of a hip joint in that the head is connected directly to the shaft, however, it can also be provided that the head is connected to the shaft via another part, for example an intermediate sleeve In the context of the present description, "head" denotes that part or optionally the part combination For the sake of simplicity, in the following, the head will be referred to as "a" part in this sense.

The two parts "shaft" and "head of the endoprosthesis lie before an operation, in which a prosthesis is to be implanted, as separate elements or parts before

Operation step of the shaft - usually introduced by means of an operation instrument - introduced into the femur and in a further, subsequent operation step, the head firmly connected to the shaft.

For connection between the shaft and the head, the shaft usually has an extension with a surface area, wherein the surface area has a top surface and a rotationally symmetrical conical surface, so that at least substantially a straight circular truncated cone is defined by these two surfaces. The head has a corresponding recess to the extension, the so is designed so that the extension introduced into the recess of the head and thereby a firm connection between the shaft and head can be made.

The depression usually has a lateral wall region, by means of which the shape of a circular cone is fixed, as well as a bottom directly adjoining this wall region, so that the depression as a whole is frustoconical.

For the connection between a head and an extension is usually provided that the introduced into the recess extension contacts the lateral wall portion of the recess. Therefore, for a suitable

Connection possibility, the recess of the head have an opening angle which is at least as large (within the tolerance fields) as the corresponding angle of the surface area. In addition, the recess must be so deep that the top surface of the extension can not be introduced to the bottom of the recess, because this would override the cone pairing.

According to the current state of affairs, a surgeon has many different shanks and different heads available. One of the reasons for this is that, with differently shaped and differently sized shafts and heads, individual framework conditions can be taken into consideration, which are given in the case of an implantation of a hip joint. For example, shafts are available in different sizes, which are accordingly suitable for use on different sized femurs. Furthermore, manufacturer-dependent differences in shape and size are common.

In general, it is possible for a surgeon, to some extent, to detect the conditions that should be taken into account for the selection of suitable prosthesis parts before the start of the operation in which a shaft and a head are to be implanted. For example, a statement can sometimes be made on the basis of suitable x-ray images as to which size of the shaft should have.

However, the conditions relevant to a suitable selection before the operation can generally not be detected as comprehensively or reliably that on this basis alone a definite decision on the parts to be selected would be possible. For example, bone quality in the area of the joint socket plays a role, for example. Therefore, it usually happens that it is only in the course of an operation, ie intraoperatively, to decide which part or parts are actually implanted.

Thus, a surgeon is regularly faced with the task during surgery to decide which parts should be selected specifically for the implantation. This is difficult because there are many factors to consider. In addition to the relevant anatomical and other medical aspects, it has to be taken into account in particular that the head and the shaft must fit to one another in such a way that a connection between these two parts that is perfect in the sense of the operation can be established. For this, the extension of the shaft and the recess of the head must be in size and shape accordingly match. In this context, it should be noted that in general many different shanks are available, whose extensions are shaped differently and also many heads are available with differently shaped wells. Furthermore, it should be borne in mind that any manufacturer's information in this regard should be checked during surgery and before establishing a connection between a head and a stem as a precautionary measure; For example, it may be expected that there is damage to the extension of the shaft, as may occur, for example, in the course of an operation in which a head of a prosthesis is replaced.

The present invention is based on the object to provide a means by which the decision as to which parts of a corresponding multi-part prosthesis should be selected concretely for implantation can be facilitated.

This object is achieved according to the invention with the objects specified in the independent claims. Particular embodiments of the invention are indicated in the dependent claims. According to the invention, a test device for testing geometric properties of a prosthesis part is provided which has a surface area with a top surface and a (rotationally symmetrical) conical surface. The tester has a recess with a side wall which is shaped so that a circular cone is defined by them. The sidewall thus describes a part of a circular cone surface. In this case, the side wall is provided for contacting with the surface region of the prosthesis part. Furthermore, the tester on first test means, which are designed to capture the immersion depth of the surface area in the depression in the state of contact between the side wall and the surface area.

For contacting it is provided that the surface region of the prosthesis part is inserted as far as possible into the depression or is. In this state of contacting so the tester and the surface area of the prosthesis part are positioned in a certain way relative to each other. Hereinafter, this relative position will be referred to as a "test position" for the sake of simplicity.

With the tester can thus be easily checked whether the surface area is suitable in view of its immersion depth for connection to a particular head having a recess known form.

Advantageously, the recess further has a bottom surface, and the first checking means are adapted to detect, in the state of contacting between the side wall and the surface region - ie in the test position - a distance which results between the top surface of the surface region and the bottom surface.

Advantageously, the first checking means comprise a first scanning means, preferably a first scanning pin.

Advantageously, the test apparatus further comprises second test means, which are designed to detect a measure of the cone angle enclosed by the conical surface of the surface area. This also makes the decision on whether to certain head of a prosthesis fits on a particular shaft of a prosthesis, further facilitated.

Advantageously, the second Prüfrnittel thereby a second scanning means, preferably a second sensing pin, with which a further distance can be detected, in the state of contact between the side wall and the surface area - ie in test position - between a first position of the side wall and a second place of the conical surface results.

Advantageously, the first or optionally the second test means further comprise comparison means for comparing a distance detected with the first and second test means, respectively, or a depth of immersion detected with the first test means with a corresponding predetermined desired range. The desired range can therefore specify a size range in which the size of the detected distance or the detected immersion depth must be in terms of a suitable connection. The comparison means may include a marking, for example a vernier, which indicates the desired range. By means of such a marking, it is possible in a simple manner, in particular without reading a number, to make a decision as to whether the detected distance or the detected immersion depth lies within the desired range and thus a specific connection is suitable according to this criterion.

Advantageously, the side wall has at least one opening or at least one translucent or transparent subarea, such that in the state of contacting between the side wall and the surface area - ie in test position - the surface region of the prosthesis part at least partially from outside the testing device through the opening or through the Part area is recognizable.

Advantageously, the tester on a handle member that is provided for manually holding the tester, and a recess comprising the contact element. Advantageously, the grip element and the contact element via a resilient element, preferably connected to each other via a vibrating system. Farther Advantageously, the grip element and the contact element are connected to each other via a hinge.

Advantageously, the first and / or optionally the second test means comprise a sensor, preferably an optical, electromagnetic or acoustic sensor. Such a sensor is suitable for contactless detection of a corresponding distance. As a result, the risk of damage to the prosthesis part and in particular the surface area can be reduced. Advantageously, the sensor comprises an electronic pickup and amplifier.

According to a further aspect of the invention, a method for testing geometric properties of a prosthesis part is provided, which has a surface area with a top surface and a conical surface, wherein a straight truncated cone is defined by the top surface and the conical surface. The method is carried out with the aid of a test device according to the invention and comprises the following steps: (a) contacting the side wall of the depression with the surface region of the prosthesis part, and (b) detecting the immersion depth of the surface region into the depression.

The invention will be explained in more detail below with reference to an embodiment with reference to the drawings. Show it:

Fig. 1 is a perspective sketch of an embodiment of a test device according to the invention together with a circular frustoconical surface portion of a to be tested

Prosthetic part, and

Fig. 2 is a sketch for the possible arrangement of scanning pins of

Tester.

1 shows an exemplary embodiment of a test device 2 according to the invention for testing geometric properties of a prosthesis part, which has a surface area which substantially describes the shape of a straight circular truncated cone, sketched in perspective. In Fig. 1 is the Surface region of the prosthetic part to be tested with the reference numeral 4 provided. The surface region 4 has a lateral surface or conical surface 14, which is rotationally symmetrical and shaped like a straight section of a circular cone. The surface region 4 can also be seen in the sketch of FIG. 2. Furthermore, the surface region 4 has a cover surface, which is provided in FIG. 2 with the reference numeral 5. The top surface 5 is oriented normal to the axis of symmetry of the conical surface 14, so that therefore a straight truncated cone is determined by the top surface 5 and the conical surface 14.

The prosthesis part to be tested may, for example, be a shaft of an artificial human or animal hip joint, the shaft having an extension, for example a "neck area", which encompasses the surface area mentioned, but other cases of conical connections of prosthesis parts are also conceivable For example, it could in principle also be prosthesis parts of other joints (joints of the upper and lower extremities,

Spine ...) act. The decisive factor with regard to the suitability of the test device is merely that the prosthesis part to be tested has the said surface area.

The test device 2 has a recess 10 with a side wall 6 and a circular edge region 16, wherein the inner diameter of the edge region 16 is greater than the diameter of the top surface 5 of the surface region 4 of a prosthesis part suitable for testing. Therefore, the surface region 4 can be received by the depression 10 at least in a region around the cover surface 5, so that the surface region 4 can "dip" into the depression 10.

The side wall 6 is shaped so as to define a "further" circular cone, as compared to the circular cone mentioned above in connection with the surface area 4. The side wall 6 of the recess 10 is shaped like a section of this "further" circular cone , The side wall 6 is for immediate

Contacting with the surface portion 4 of the prosthetic part provided. FIG. 1 shows the state in which the surface region 4 contacts the side wall 6 as intended. In this case, the surface area 4 is immersed as far as possible in the recess 10 in the state of the intended contact. As As already mentioned above, this relative arrangement between the test apparatus 2 and the surface area 4 is also referred to simply as the "test position." In this case, it depends in particular on the geometric properties of the surface area 4 how far the surface area 4 dives into the recess 10 in the test position The immersion depth of the surface area 4 into the recess 10 thus depends on the geometric properties of the surface area 4. For example, under otherwise identical conditions, the surface area 4 in the test position dips less into the recess 10 the larger its top surface 5 is.

Furthermore, the test device has first test means which are designed to be in

Test position to detect the immersion depth of the surface region 4 in the recess 10. Since the side wall 6 of the recess 10 describes a circular cone, the immersion depth is a measure of the distance that results in test position between the top surface 5 of the surface portion 4 and the top of this circular cone.

For a suitable connection between a head and the surface region 4 is a prerequisite that in the connected state, a certain minimum distance between the top surface 5 of the surface portion 4 and the bottom of the corresponding recess of this head exists. Therefore, said immersion depth can be a criterion for the suitability of a particular head to connect to the surface area 4 being tested.

By way of example, the first checking means may comprise first comparing means with which a depth of immersion detected by the first checking means can be compared with a corresponding setpoint range. The target range indicates a range in which the size of the immersion depth must be in terms of a suitable connection option. The desired range may be indicated by a mark 20, for example.

Alternatively or additionally, it can be provided that the recess 10 a

Floor surface 18 and the first test means are further adapted to detect in the test position, a distance which results between the top surface 5 of the surface portion 4 and the bottom surface 18 of the Vertierung 10. For this purpose, it can be provided, for example, that the first checking means comprise a first scanning means, For example, have a first scan pin 36. Such a direct detection of the distance between the top surface 5 and the bottom surface 18 has the advantage that this test is direct and particularly accurate insofar as it is independent of the geometric design of the surface region 4 in the transition region between the cone surface 14 and the top surface 5. For example, the

Surface area 4 at the said transition have a chamfer or chamfer, which in general a sole examination using the above-mentioned mark 20 may be associated with a certain degree of inaccuracy.

It is particularly advantageous if the depression 10 as a whole - that is to say including the base 18 - is shaped in the same way as the depression of a head to be assessed for its suitability. This makes it particularly easy to check whether a minimum distance between the top surface 5 and the bottom of the recess of the head is maintained at a designated connection.

As can be seen from Fig. 1, in the embodiment, the side wall 6 at least one opening 12 which is shaped such that the surface portion 4 of the prosthesis part is at least partially visible from outside the tester 2 through the opening 12, if - as well as shown in Fig. 1 - the side wall 6 is in contact with the surface portion 4 of the prosthesis part - ie in test position. The opening 12 may for example be given in the form of a fenestration, recess or franking. Through the opening 12, a contact between the surface region 4 and the side wall 6 can be checked directly visually.

In the exemplary embodiment, the test device 2 has a jacket-like wall region 32, through which the depression 10 is formed. The opening 12 is formed as an opening in the wall portion 32. Instead of or in addition to the at least one opening 12, it is possible to provide at least one transparent or at least translucent subregion of the wall region 32. The wall region 32 can also be formed as a whole transparent or translucent.

As shown in Fig. 1, the above-mentioned mark 20 may be disposed in the edge region of the opening 12. The mark 20 can be two Marking lines 22 and 24, which represent a lower and an upper limit value of the desired depth of immersion amount setpoint 5, are included. In this case, the setpoint region can be chosen in particular such that the surface region 4 is suitable for a specific connection with regard to the immersion depth when the cover surface 5 between the two lines 22 and 24 is positioned in the test position. In other words, the desired range can be selected such that it indicates tolerances for an immersion depth within which the detected immersion depth must lie, so that a specific head is suitable for connection to the prosthesis part to be tested.

The described arrangement of the marking 20 a particularly easy and simple test is possible. In particular, no absolute determination of the immersion depth is required. In particular, it is not necessary for a numerical value to be read.

Optionally, an analogous marking of a corresponding desired range for a distance between the top surface 5 and the bottom 18 of the recess 10 may also be provided on the first scanning pin 36.

As best seen in Fig. 2, the tester 2 according to the

Embodiment further comprises second test means which are adapted to detect a measure of the cone angle enclosed by the conical surface 14 of the surface region 4 or short angle α. In the exemplary embodiment, the second checking means have a second scanning means in the form of a second scanning pin 30, wherein the second scanning pin 30 is arranged displaceably in the wall region 32 so that it pierces the side wall 6 at a specific point 38. The second scanning pin 30 is displaceable relative to the wall region 32 in such a way that it can be moved toward and away from the axis of symmetry S of the cone surface 14.

The scanning pin 30 can be arranged so that it - starting from a position to be oriented on the symmetry axis S - upon movement of the tester 2 in the test position by contact with the surface region 4 to the outside, ie away U is displaced from the symmetry axis S. It is also possible to provide a plurality of such scanning pins 30.

With the second scanning pin 30 can be easily closed on the basis of the insertion depth of the Abtaststiftes 30, which results when the scanning pin 30 in the test position, the surface region 4 and the conical surface 14, the cone angle α. The cone angle α can therefore be checked in the recess 10 by means of gap or gap measurement with a firm fit of the surface region. In general terms, therefore, a length dimension can be detected with the second test means, which is representative in test position for the distance between the point 38 and the surface area 4 and thus for the cone angle α.

For a particularly simple assessment of the question of whether the tested surface area 4 with respect to its cone angle α for the intended

Compound is suitable, the second test means may comprise second comparison means. These may comprise a corresponding further marking 26 on the scanning pin 30, which indicates a nominal range for the size of the angle α, which is analogous to the abovementioned desired range for the size of the immersion depth.

As an alternative to the first sensing pin 36 and / or to the second sensing pin 30, a corresponding length sensor may also be provided, for example an optical or otherwise electromagnetically acting sensor, as known per se from the prior art. Such a sensor may include, for example, an electronic pickup and amplifier. With a sensor, non-contact length measurement is possible, so that the risk of damage to the surface region 4 can be further reduced by the use of a sensor.

In the embodiment, the tester is designed as a handheld device. It instructs

Handle member 40, which is provided for manually holding the tester 2, and a contact element 42, wherein the contact element 42, in particular the recess 10 with the side wall 6 includes. According to a variant not shown in the figures, the grip element 40 and the contact element 42 can be connected to one another via a resilient element, preferably via a vibration system. This makes it possible that the force or the pressure, which is transmitted during a test of the tester 2 on the surface region 4, can be limited to the top. Too strong placement of the tester 2 on the surface region 4 can thus be reliably prevented.

Furthermore, the grip element 40 and the contact element 42 can be connected to one another via a joint (also not shown in the figures), preferably a resilient joint. As a result, tilting when placing the test device 2 on the surface region 4 can be prevented. This is advantageous because it reduces the risk of prints, which in principle can be caused by handling the tester 2 on the surface region 4.

To protect the surface area 4, the side wall 6 of the test apparatus 2 may be modified such that damage to the active surface of the surface area 4 can be virtually ruled out. On the one hand, measuring points, for example a contact point between the second scanning pin 30 and the lateral surface 14 of the surface region 4, can be provided outside the active contact zone between head and shaft, ie outside the region around the peripheral edge of the top surface 5. Furthermore, suitable coatings or a suitable choice of material can have an advantageous effect in this respect; For example, plastics, metals or ceramics can be used for this purpose.

To test geometric properties of the prosthesis part with the aid of a test device according to the invention, the following two steps are provided: (a) contacting the side wall 6 of the depression 10 with the surface region 4 of the prosthesis part, and (b) detecting the immersion depth of the surface region 4 into the depression 10 Furthermore, it can be advantageously provided that a measure of the cone angle α is detected. Furthermore advantageously, the immersion depth and optionally the measure of the cone angle α (in each case) are compared with a corresponding desired range. Advantageously, step (a) and / or step (b) are performed by means of a contact or non-contact length measurement. A touching length measurement can be done for example by means of a Abtaststiftes. A non-contact length measurement can be done for example by means of a sensor.

LIST OF REFERENCE NUMBERS

2 Tester 4 Surface area of the prosthetic part to be tested

5 top surface of the surface area

6 side wall of the recess 10 recess

12 opening 14 cone surface of the surface area

16 edge area of the recess

18 bottom of the depression

20 Marking of a nominal range

22 Mark for a lower limit of the target range 24 Mark for an upper limit of the target range

26 more markings

30 second scanning pin

32 wall portion through which the recess is formed

36 first scan pin 38 location on the sidewall

40 handle element

42 contact element

α cone angle; Angle enclosed by the cone surface of the surface area

S symmetry axis of the surface area of the prosthetic part

Claims

claims

1. testing device for testing geometric properties of a prosthetic part, which has a surface area (4) with a top surface (5) and a conical surface

(14), characterized by

- A Vertierung (10) with a side wall (6) which is shaped so that a circular cone is defined by them, wherein the side wall (6) for a contact with the surface region

(4) of the prosthetic part is provided, and

- First test means, which are designed to detect the immersion depth of the surface region (4) in the recess (10) in the state of contact between the side wall (6) and the surface region (4).

2. Testing device according to claim 1, wherein the recess (10) further comprises a bottom surface (18) and the first test means are adapted to detect in the state of contact between the side wall (6) and the surface region (4) a distance, the between the top surface (5) of the surface region (4) and the

Floor surface (18) results.

3. Testing device according to claim 1 or 2, wherein the first checking means comprise a first scanning means, preferably a first scanning pin (36).

4. Testing device according to one of the preceding claims, further comprising:

second test means adapted to provide a measure of the cone angle included by the conical surface (14) of the surface region (4)

(α) to capture.

5. Testing device according to claim 4, wherein the second test means a second scanning means, preferably a second scanning pin (30), with which a further distance can be detected, which is in the state of contacting between the side wall (6) and the surface region (4) between a first location (38) of the side wall (6) and a second location (39) of the conical surface (14).

6. Test device according to one of the preceding claims, wherein the first and optionally the second test means further comprising comparing means for comparing a detected with the first and second test means distance or detected with the first test means immersion depth with a corresponding predetermined target range.

7. Testing device according to claim 6, wherein the comparison means comprise a mark (20) indicating the desired range.

8. Testing device according to one of the preceding claims, wherein the side wall (6) has at least one opening (12) or at least one translucent or transparent portion such that in the state of contact between the side wall (6) and the

Surface region (4) of the surface region (4) of the prosthesis part is at least partially visible from outside of the testing device (2) through the opening (12) or through the partial area.

9. Test device according to one of the preceding claims, comprising a grip element (40), which is provided for manually holding the tester (2), and a recess (10) comprehensive contact element (42).

10. Testing device according to claim 9, wherein the grip element (40) and the contact element (42) via a resilient

Element, preferably via a vibration system, are interconnected.

1 1. Test device according to claim 9 or 10, wherein the handle element (40) and the contact element (42) via a hinge connected to each other.

12. Test device according to one of the preceding claims, wherein the first and / or optionally the second test means comprise a sensor, preferably an optical, electromagnetic or acoustic sensor.

13. A tester according to claim 12, wherein the sensor comprises an electronic pickup and amplifier.

14. A method for testing geometric properties of a prosthetic part, which has a surface area (4) with a top surface (5) and a conical surface (14), wherein by the top surface (5) and the conical surface (14) is fixed a straight truncated cone, said the method is carried out with the aid of a test device according to one of the preceding claims, characterized by the steps:

(a) contacting the side wall (6) of the recess (10) with the

Surface area (4) of the prosthetic part, and (b) detecting the immersion depth of the surface area (4) in the recess

(10).