DE102005003317A1 - Method for determining the neutral position of a femur relative to a pelvic bone and apparatus for carrying out this method - Google Patents

Abstract

A method for determining the neutral position of a femur relative to a pelvic bone is characterized by the following method steps: DOLLAR A È From the three points of the pelvic bone DOLLAR A 1) left anterior superior iliac spine (left iliac spine) DOLLAR A 2) right Spinal iliac anterior superior DOLLAR A 3) symphysis pubis (pubis) DOLLAR A the anterior pelvic plane. DOLLAR A È Determines the position of the hip joint center relative to the pelvic bone and relative to the femur. DOLLAR A È The position of the knee joint relative to the thighbone is determined. DOLLAR A È The lower leg bends about 90 ° to the thigh and then determines the position of the ankle relative to the femur. DOLLAR A È A femoral sagittal plane is determined from the position data of the hip joint center, the knee joint and the ankle in the angled lower leg. DOLLAR A È Calculate the angle changes necessary to bring the line connecting the hip joint center to the knee joint (mechanical axis of the femur) in a plane parallel to the anterior pelvic plane through the midpoint of the hip joint and perpendicular to the connecting line of the two spinae iliacae anteriores superiores runs. DOLLAR A È In addition, the angular changes necessary to orient the femoral sagittal plane perpendicular to the anterior pelvic plane are calculated.

Description

The The invention relates to a method for determining the neutral position of a femur relative to a pelvic bone.

at the implantation of an artificial hip joint It is necessary, among other things, the mobility of the femur relative to the pelvic bone after insertion of the implant components to be able to predict mathematically in order to predict whether the use of certain Implant components and their specific orientation and positioning in the bones to the desired lead maximum mobility. For example, it is checked whether the leg is stretched, a rotation of the femur inwards and outside in enough Dimensions is possible, also at angled leg pivoting inwards and outwards. The Rotary axes based on this review are relative to the pelvic bone fixed axes, and it is therefore essential that the Thigh and thus implanted implant parts for determination This mobility a certain orientation to the pelvic bone exhibit. It is believed that a neutral position suitable for it is a position that is essentially the orientation of the Thighs in a standing patient and stretched Leg corresponds.

Around this neutral position of the thigh relative to the pelvic bone In practice, one has the femur of a patient for example while an operation as possible placed exactly in this neutral position. This succeeds however only very imperfect, as the pelvic bones often swivel during surgery is and there are the body parts of the patient at surgery covered by surgical drapes and hard to access are, as well such a precise arrangement is problematic in a recumbent patient. For this reason, it was only approximately possible, a neutral position then from the starting then the desired simulation calculations carried out can be.

It Object of the invention to provide a method with which the Neutral position of the femur relative to the pelvic bone can be determined in a simpler way.

• • Man bestimmt aus den drei Punkten des Beckenknochens 1) linke spina iliaca anterior superior (linker oberer Darmbeinstachel) 2) rechte spina iliaca anterior superior (rechter oberer Darmbeinstachel) 3) symphysis pubis (Schambein) die anteriore Beckenebene.
• • Man bestimmt die Lage des Hüftgelenkmittelpunktes relativ zum Beckenknochen und relativ zum Oberschenkelknochen.
• • Man bestimmt die Lage des Kniegelenkes relativ zum Oberschenkelknochen.
• • Man beugt den Unterschenkel etwa um 90° gegenüber dem Oberschenkel und bestimmt dann die Lage des Sprunggelenks relativ zum Oberschenkelknochen.
• • Man bestimmt aus den Positionsdaten des Hüftgelenkmittelpunktes, des Kniegelenkes und des Sprunggelenkes bei abgewinkeltem Unterschenkel eine Femursagittalebene.
• • Man berechnet die Winkeländerungen, die notwendig sind, um die Verbindungslinie des Hüftgelenkmittelpunktes mit dem Kniegelenk (mechanische Femurachse) in eine Linie zu überführen, die in einer Parallelebene zur anterioren Beckenebene durch den Hüftgelenkmittelpunkt und senkrecht zur Verbindungslinie der beiden spinae iliacae anteriores superiores verläuft.
• • Und man berechnet zusätzlich die Winkeländerungen, die notwendig sind, um die Femursagittalebene senkrecht zur anterioren Beckenebene zu orientieren.

This object is achieved by a method of the type described above, which is characterized by the following process steps:

• 1) left anterior superior iliac spine (left upper iliac spine) 2) right anterior superior iliac spine (right iliac spine) 3) symphysis pubis (pubis) the anterior pelvic plane.
• • Determine the location of the hip joint center relative to the pelvic bone and relative to the femur.
• • Determine the position of the knee joint relative to the thighbone.
• • Flex the lower leg about 90 ° with respect to the thigh and then determine the position of the ankle relative to the thighbone.
• • A femoral sagittal plane is determined from the position data of the hip joint center, the knee joint and the ankle in the angled lower leg.
• • Calculate the angle changes necessary to bring the hip joint midline line (mechanical femur axis) into line parallel to the anterior pelvic plane through the midpoint of the hip joint and perpendicular to the connecting line of the two anterior superior iliac spine.
• • Additionally, one calculates the angle changes necessary to orient the femoral sagittal plane perpendicular to the anterior pelvic plane.

by virtue of these process steps are obtained So a record of location coordinate transformations that describe as the thigh swings ver and must be twisted in to reach the neutral position. This shift will not happen physically carry out, but only mathematically, whereby in this way also mathematically calculate the displacements and rotations of implant parts can, who are actually implanted in the thigh or even in a previous model theoretically assumed in the thigh become. One can therefore mathematically the implant parts in one position and convert position corresponding to the neutral position, and can starting from this relative position of the thigh-side implant parts on the one hand and the pelvic bone-side implant parts on the other hand, calculate their mobility to each other in the usual way.

Essential to the method described is that no opening of the body is necessary, all the described method steps can be found without intervention in the body simply by movements of the limbs and scanning certain marker points, regardless of which position the patient is in and in which position the limbs are arranged relative to the pelvic bone. It is sufficient in this method, in some position of the thigh to bend the lower leg approximately at right angles, and then to determine the position of the ankle relative to the thigh, all other steps are determinations of endogenous marking points and calculations, in particular, it is not necessary, the thigh actually to the neutral position.

Of the Determination of the femoral axis is based on the knowledge that at Angling the lower leg of the ankle in the femoral axis is pivoted, which in the neutral position of the thigh indeed perpendicular to the anterior pelvic plane and perpendicular to the connecting line the two spinae iliacae anteriores superiores lies.

It is beneficial when using the three pelvic bone points for determination of the anterior pelvic plane determined by palpation.

Of the Hip center let yourself by pivoting the femur relative to the hip joint determine. Assuming that it is the hip joint is a ball joint, all the points of the thigh move, at the distance to the hip joint center are arranged on a spherical shell around the hip joint center. These Ball cup can be determined by measurement, for example with Help a navigation system, and from it can be the center of the ball determine that with the hip joint center coincides.

The Position of the knee joint may also preferably by palpation the kneecap can be determined, and the position of the ankle can be also be determined by palpation, for example by palpation of both lateral ankle projections and / or bony prominences the front of the lower leg.

The The invention also relates to a device for carrying out this Procedure, at the pelvic bone and femur in each case a marking element is defined, these marking elements be in terms of their location, so in terms of position and Orientation in the room, monitored by a navigation system, so that in every moment the position of these marking elements in the room determined can be.

There set the marker on the pelvic bone and thigh There is a permanent relationship between the positional data the marking elements on the one hand and the position data of the above Marking points on the pelvic bone on the one hand and the mechanical Femoral axis and the sagittal plane on the femur, on the other hand, Once this relationship is established, it remains the same and by determining the position of the marking elements can then also the respective position of said marking points, connecting lines and calculate levels.

Cheap is if, for the determination of the marking points, one provided with a marking element Button is used, whose location is also monitored by the navigation system becomes. This is possible in a simple manner, the marking points described in terms of their location to be detected by the navigation system and create a corresponding record.

The following description of preferred embodiments of the invention used in conjunction with the drawings for further explanation. Show it:

1 a schematic view of the pelvic bone, the femur and the lower leg bone of a patient and a navigation system with data processing system for determining the location data of the body's own marking points and other geometric data;

2 : a view of the patient similar to the presentation of the 1 with additional indication of the mechanical femoral axis of the femur and

3 : A view of the pelvic bone, thighbone, and 90 ° angled lower leg of a patient, indicating the anterior pelvic plane, the mechanical femoral axis, and the femoral sagittal plane.

To determine the neutral position of the thigh of a patient is a navigation system 1 used, which has three spaced-apart transmitter 2 . 3 . 4 emits an infrared radiation that is on reflector elements of marking elements 5 . 6 . 7 impinges and from there to the transmitter also working as a receiver 2 . 3 . 4 is backblasted. From the transit time differences and the directions of the reflected radiation, the navigation system at any time the exact position and orientation, ie the location of each individual marking element 5 . 6 . 7 determine in space and generate a corresponding record, which then a data processing system 8th can be supplied for further processing. The data processing is among other things a display unit in the form of a screen 9 assigned.

such Navigation systems are known per se and can also be used in a familiar way be deviating, for example, instead of infrared radiation electromagnetic radiation or ultrasonic radiation used etc. It is essential only that the navigation system the Determine the location of the marking elements in the room at any time and from it can generate a record.

A first marking element 5 is stuck with a thigh bone 10 a patient connected, for example by means of a bone screw screwed into the bone, to which the marking element 5 is rigidly attached. Similarly, the marker is 6 firmly with the pelvic bone 11 connected to a patient, and finally is the marker 7 rigid with a palpation instrument 12 connected, which, for example, a needle-shaped stylus tip 13 having. With this probe tip 13 can be approached striking points on the body of a patient, and from the position of the Tastinstruments and the geometric data of the Tastinstruments, ie the relative position of the probe tip 13 relative to the marking element 7 , then the exact location of the probe tip in the room and thus one of the probe tip 13 approached point of the patient can be determined.

To determine the neutral position of the thigh relative to the pelvic bone, the following parameters are recorded:
With the feeler instrument 12 At the pelvic bone, three landmarks are approached, namely the left anterior superior iliac spine 14 (left iliac spine), the right anterior superior iliac spine 15 (right iliac spine) and the symphysis pubis 16 (Pubic bone). The data processing system calculates from the datasets that describe the location of these three landmarks 8th a plane, referred to below as the anterior pelvic plane. This is arranged almost vertically in a standing patient and forms a reference plane for the pelvic bone.

In a further step, the location of the hip joint center 17 certainly. This will be the thigh bone 10 opposite the pelvic bone 11 pivoted. During this pivoting movement, the marking element moves 5 on a ball cup around the hip joint center 17 , This spherical shell is measured by the navigation system, and the data processing system 8th it can determine the location of the hip joint 17 determine, relative to the femur 10 that is to the marking element 5 , and relative to the pelvic bone 11 that is to the marking element 6 ,

In a further step, the position of the knee joint is determined. Since this is not initially opened in the operation, this position is approximately determined by the fact that a certain point on the kneecap 18 and defines this as a knee center.

The data processing system 8th calculated from the position data of the hip joint center 17 and the knee joint a connecting line, as a mechanical femoral axis 19 referred to as ( 2 ). This is also the orientation of this mechanical femoral axis relative to the femur 10 and thus with respect to the marking element 5 certainly.

In a further step, the lower leg of the patient is angled relative to the thigh by about 90 °, as in 3 is shown. In this position of the lower leg becomes the position of the ankle 20 certainly. Again this can be done by palpation with the palpation instrument 12 For example, the most prominent points of the two hocks of the foot or on the front of the leg, a prominent bone point in the ankle are palpated and from these data, the position of the ankle is determined. The data processing system 8th calculated from the position data of the hip joint center 17 , the knee joint and the ankle joint, this is called a femoral sagittal plane 21 designated. The geometric data of this femoral axis 21 relative to the femur 10 are known, and thus also relative to the marking element 5 ,

at The measurement described will normally be the patient's leg not be aligned relative to the pelvic bone, that is, it will be not in the neutral position.

It is now assumed that the neutral position is characterized in that the mechanical axis of the femur 19 parallel to the anterior pelvic plane 22 and perpendicular to the connecting line 23 the two spinae iliacae anteriores superiores runs and that the Fursuragittalenbene 21 perpendicular to the anterior pelvic plane 22 is arranged. This assumption is essentially true in most patients, so this description is a very good representation of the neutral position.

Since this position of the leg was not taken when taking the measurement, there are deviations, and these deviations can the data processing system 8th It is readily calculated, that is, the coordinate transformations necessary to derive from the actually measured orientations of the femoral axis plane are calculated 21 and the mechanical Fe murachse 19 to get into the appropriate positions at the neutral position. From this transformation data can then also calculate the transformation data, the transition of the position of the marking element 5 describe from the actual measurement position in the neutral position or the transition of an inserted into the thigh bone and fixedly connected to this implant. The location of this implant in the femur 10 is either mathematically simulated before surgery, it is said that a certain position of the implant in the femur, for example, using image data of the femur and image data of the implant part, which are copied one above the other, or you get the position of the implant part after implantation characterized in that the implant part is also navigated, for example by a marking element which is at times rigidly connected to the implant part. In any case, it is the data processing system that way 8th possible, from the actual position of the implant, by determining the location of the thigh bone marking element 5 can be determined at any time to calculate the position of the implant in the neutral position of the femur, relative to the pelvic bone 11 ,

Without the thighbone 10 In fact, to have brought this neutral position, a position of the implant part in the femur relative to the pelvic bone corresponding to the neutral position of the femur can be specified for the simulation of the movement sequences, and thus the simulation of the mobility can be carried out in a realistic manner. For this procedure, it is not necessary to make any interventions on the body, nor must the leg be brought into the neutral position. The measured values described are easy for the surgeon to record and lead to reliable, well reproducible values for the determination of the neutral position of the thigh.

Claims (6)

Method for determining the neutral position of a femur relative to a pelvic bone through the following process steps: • One determines from the three Points of the pelvic bone 1) left spina iliaca anterior superior (left upper iliac spine) 2) right spina iliaca anterior superior (right upper iliac spine) 3) symphysis pubis (Pubic bone) the anterior pelvic plane. • One determines the location of the hip joint center relative to the pelvic bone and relative to the femur. • One determines the position of the knee joint relative to the femur. • You bow the lower leg about 90 ° opposite to the Thighs and then determines the location of the ankle relatively to the thighbone. • Man determined from the position data of the hip joint center, Knee joint and the ankle in angled lower leg one Femursagittalebene. • Man calculates the angle changes, which may be necessary to the connecting line of the hip joint center with the knee joint (mechanical femur axis) into a line, the in a parallel plane to the anterior pelvic plane through the hip joint midpoint and perpendicular to the connecting line of the two spinae iliacae anteriores superiores runs. • And you calculated additionally the angle changes, which are necessary to the femoral sagittal plane perpendicular to the anterior Orient the pelvic plane. Method according to claim 1, characterized in that that he the three pelvic bone points to determine the anterior pelvic plane determined by palpation. Method according to claim 1 or 2, characterized that he the hip joint center Swiveling the femur relative to the hip joint certainly. Method according to one of the preceding claims, characterized characterized in that the position of the knee joint is determined by palpation of the kneecap. Method according to one of the preceding claims, characterized characterized in that The position of the ankle is determined by palpation. Device for carrying out the method of one of claims 1 to 5 with a navigation system, with the thigh bone and the pelvic bone of a patient defined marking elements, the position and orientation of which can be determined by the navigation system, with a connected to a marking element probe element and with a data processing system for processing the Position data supplied by the navigation system of the marking elements and thus of the femur, the pelvic bone and the palpation instrument, characterized in that the data processing system is programmed so that it from the three points of the pelvic bone ( 11 ) left spina iliaca anterior superior ( 14 ), right spina iliaca anterior superior ( 15 ) and symphysis pubis ( 16 ) the anterior pelvic plane ( 22 ) and that from the location of the hip joint ( 17 ) relative to the pelvic bone ( 11 ) and relative to the femur ( 10 ), the position of the knee joint relative to the femur ( 10 ) and the position of the ankle ( 20 ) relative to the femur ( 10 ) at about 90 ° Angewinkel tem lower leg a femoral sagittal plane ( 21 ) determines that it calculates the angle changes necessary to make the connecting line ( 19 ) of the hip joint center ( 17 ) with the knee joint (mechanical axis of the femur) in a line parallel to the anterior pelvic plane ( 22 ) through the hip joint center ( 17 ) and perpendicular to the connecting line of the two spinae iliacae anteriores superiores ( 14 . 15 ) and that it additionally calculates the angle changes necessary to move the femoral 21 ) perpendicular to the anterior pelvic plane ( 22 ).