Medical instruments and procedures for simulation purposes in hip arthroplasty

Abstract

Medical instrumentation for simulation purposes in hip endoprosthetics, characterized by a simulation body (66) that can be tilted about a tilting axis (60) in a spatial reference system, a sensor unit (34) with which the magnitude and orientation of a tilting angle can be detected when the simulation body (66) is tilted, a data processing device (26) and a guidance unit (30), wherein the data processing device (26) is designed and programmed to simulate an inclination of a human pelvis (10) in a body reference system in which the pelvic inlet plane (B) of the pelvis (10) is inclined relative to a frontal plane (F) of the body by the tilting angle, and wherein the data processing device (26) outputs implantation information to the user at the guidance unit (30) that depends on the tilting angle.

Description

[0001] The invention relates to a medical instrument set and a method for simulation purposes in hip endoprosthetics.

[0002] During hip replacement surgery, an artificial hip socket is implanted in the pelvis to achieve the greatest possible range of motion (ROM) for the patient. It is known to align the hip socket with the pelvic inlet plane, which can be easily determined intraoperatively with the patient lying down, at predetermined angles. In practice, an anteversion angle and an inclination angle are typically used. These anteversion and inclination angles are, for example, related to an axis of the artificial hip socket, which is to be aligned with the axis of the acetabulum. The axis of the acetabulum is perpendicular to an inlet plane of the acetabulum; the anteversion and inclination angles also apply to the axis of the acetabulum.

[0003] The anteversion angle is defined, for example, as the angle of the acetabular axis in a transverse plane perpendicular to and relative to the pelvic inlet plane. The inclination angle is defined, for example, as the angle of the acetabular axis in a plane parallel to the pelvic inlet plane relative to a transverse plane perpendicular to the pelvic inlet plane. The inclination angle can also be defined, for example, as the angle that an inlet plane of the acetabulum (corresponding to the inlet plane of the acetabulum) forms with a transverse plane.

[0004] However, it should be noted that the specific definition of the anteversion and inclination angles does not restrict the present invention, but merely serves to improve understanding of the invention.

[0005] However, a problem can arise because the pelvic inlet plane typically has an inclination relative to the patient's frontal plane, which is vertically oriented when the patient is standing upright. Theoretically, the full range of motion achievable with correct positioning of the acetabulum relative to the pelvis cannot always be realized in practice, because the pelvic-femoral system cannot be considered in isolation; muscles and tendons, in particular, also influence the range of motion. Furthermore, the femur can be subject to so-called "impingement," where bone-on-bone or metal-on-metal contact occurs. This limited range of motion and impingement can lead to partial or complete dislocation of the femoral head from the acetabulum.

[0006] A disadvantage is that the inclination of the pelvic inlet plane to the frontal plane is a quantity that is not very intuitive for the surgeon and must be determined in order to correctly implant the acetabulum in the upright patient, since it differs in the lying patient from the inclination of the pelvic inlet plane to the frontal plane in the standing patient.

[0007] The object of the present invention is to provide a medical instrument set and a method to illustrate to a surgeon in a clear manner the importance of an inclination of the pelvic inlet plane to the frontal plane and to assist him in the implantation of an artificial hip joint.

[0008] This problem is solved according to the invention by a medical instrument set for simulation purposes in hip endoprosthetics, characterized by a simulation body that can be tilted about a tilting axis in a spatial reference system, a sensor unit with which the magnitude and orientation of a tilting angle can be detected when the simulation body is tilted, a data processing device and a guidance unit, wherein the data processing device is designed and programmed in such a way that it simulates an inclination of a human pelvis in a body reference system in which the pelvic inlet plane is inclined relative to a frontal plane of the body by the tilting angle, and wherein the data processing device outputs implantation information to the user at the guidance unit that depends on the tilting angle.

[0009] With this instrument, the surgeon can use the simulation model and tilt it around its axis within a spatial reference frame. This provides the surgeon with a tangible and clear way to simulate the inclination of the pelvic inlet plane relative to the frontal plane, particularly for pre- and intraoperative use. The data processing unit assumes that the tilt angle corresponds to a specific inclination angle and outputs implantation information that takes the inclination of the pelvic inlet plane to the frontal plane into account. This makes it possible, for example, to determine the influence of pelvic inclination on the range of motion of the femur when a hip socket is implanted at a predetermined anteversion and inclination angle, but the inclination of the pelvic inlet plane relative to the frontal plane is disregarded.

[0010] It is advantageous if the implantation information includes the angle and orientation at which the pelvic inlet plane is inclined relative to the frontal plane. This provides information, in particular, on whether the pelvic inlet plane is inclined anteriorly or posteriorly relative to the frontal plane.

[0011] Preferably, the information unit is an optical display unit, in particular a screen, and the implantation information is displayed on the display unit. This allows the implantation information to be perceived by the user in a particularly simple and clear way.

[0012] Advantageously, the implantation information includes at least one representation of the pelvis on the display unit, depending on the tilt angle, in a ventral and / or cranial and / or lateral viewing direction (ventral and / or cranial and / or lateral view). The plane of the display unit is preferably chosen to be parallel (ventral representation) or perpendicular (cranial and lateral representation) to the frontal plane. When the simulation body is tilted, the surgeon's viewing direction towards the plane of the display unit can be maintained, whether ventral, cranial, and / or lateral. The implantation information, including a representation of the pelvis, results in a tilted display relative to the plane of the display unit and is particularly clear for the user.

[0013] It is advantageous if at least one representation includes an axis of the acetabulum to be implanted, which axis is shown at a predetermined inclination angle and anteversion angle relative to the pelvic inlet plane, and / or an axis of the acetabulum of the pelvis. This allows the surgeon to directly observe the influence of an inclination of the pelvic inlet plane relative to the frontal plane on the axis of the acetabulum and / or the axis of the acetabulum, and to simulate the inclination by tilting the simulation body.

[0014] In the present case, the phrase "relative to the pelvic inlet plane" or "with respect to the pelvic inlet plane," insofar as it refers to the anteversion and inclination angles at which the artificial acetabulum is to be aligned and implanted, or insofar as it refers to the alignment of the acetabular axis, is to be understood as referring to a 0° pelvic tilt. The aforementioned transverse plane perpendicular to the pelvic inlet plane, which can be used to define the anteversion and inclination angles, is in this case an actual transverse plane of the body. If the pelvis is tilted relative to the frontal plane, the axis of the artificial acetabulum or the axis of the acetabulum has an actual anteversion angle and an actual inclination angle, to which reference is made here by "relative to the frontal plane" or "with respect to the frontal plane."This corresponds to an anteversion angle and an inclination angle, for the definition of which a frontal plane and an actual transverse plane of the body oriented perpendicular to this are used.

[0015] It is advantageous if the data processing device is designed and programmed to determine, based on the assumption that a hip socket to be implanted is positioned at a predetermined inclination angle and / or anteversion angle relative to the pelvic inlet plane, the actual inclination angle and / or anteversion angle of the hip socket relative to the frontal plane, depending on the tilt angle. Furthermore, the implantation information preferably includes information about the actual inclination angle and / or anteversion angle. For example, the data processing device can project the inclination and anteversion onto the frontal plane and calculate the magnitude of the inclination angle and / or anteversion angle relative to the frontal plane.This information is preferably provided as part of the implantation information, thus informing the surgeon of the actual inclination and anteversion. Based on this information, the surgeon can assess the influence of the pelvic tilt on the range of motion. If necessary, the surgeon can implant the acetabulum at a different anteversion and / or inclination angle.

[0016] Similarly, it is advantageous if the data processing device is designed and programmed to determine a value for the anteversion and / or inclination angle of the axis of the acetabulum depending on the tilt angle with respect to the frontal plane, and the implantation information includes information about this actual inclination angle and / or this actual anteversion angle.

[0017] It is advantageous if the data processing device is designed and programmed to check whether the actual inclination angle and / or the actual anteversion angle lie outside a predefined inclination angle range or anteversion angle range, and if so, if the implantation information includes a corresponding note. It is known that a relatively large range of motion with a simultaneously low risk of dislocation, luxation, and impingement can be achieved when the inclination and / or anteversion lie within their respective predefined ranges. Due to the inclination of the pelvic inlet plane to the frontal plane, it may occur that the actual inclination and / or anteversion lie outside these ranges.In this case, the data processing unit can issue a notification, such as a warning, as part of the implantation information. This notification may include information indicating that a limited range of motion is to be expected and that there is a risk of dislocation, luxation, or impingement.

[0018] Similarly, it is advantageous that the data processing device is designed and programmed to determine whether the actual inclination angle and / or the actual anteversion angle of the axis of the acetabulum (relative to the frontal plane) lies outside a predefinable inclination angle range or outside a predefinable anteversion angle range, and if so, that the implantation information includes a corresponding indication.

[0019] Preferably, the data processing device is designed and programmed to base the testing on the "safe zone" for the inclination angle and / or the anteversion angle according to Lewinnek. The angle ranges specified by Lewinnek are 45° ± 10° for inclination and 15° ± 10° for anteversion, with the pelvic inlet plane parallel to the frontal plane. These angle ranges define the so-called "safe zone," within which optimal freedom of movement with the lowest risk of dislocation is achieved.

[0020] Advantageously, the data processing device is designed and programmed such that, if the actual inclination angle and / or the actual anteversion angle of the acetabular axis and / or the acetabular axis lie outside a predefined inclination angle range or anteversion angle range, the implantation information includes a note to implant the acetabular cup at a different inclination angle and / or anteversion angle relative to the pelvic inlet plane. This provides the surgeon with a note to implant the acetabular cup at a different inclination and / or anteversion angle for the pelvic tilt simulated by the simulation body.The data processing unit can suggest to the surgeon a change in inclination and / or anteversion so that, taking into account the pelvic tilt, the greatest possible freedom of movement can be achieved while minimizing the risk of dislocation.

[0021] Ideally, the data processing unit is designed and programmed in such a way that, if the simulation body is tilted, the implantation information can be output and / or updated in real time at the guidance unit.

[0022] It is advantageous if the data processing unit is designed and programmed to receive a value for a patient's pelvic tilt. For example, the pelvic tilt can be determined pre- or intraoperatively using X-ray imaging, ultrasound, and / or palpation. Based on the determined pelvic tilt provided to the data processing unit, and assuming that the acetabulum is implanted at a predetermined inclination angle and / or anteversion angle relative to the pelvic inlet plane, the unit can determine the actual inclination angle and / or anteversion angle of the acetabulum relative to the frontal plane.Preferably, the implantation information includes information about the actual inclination angle and / or the actual anteversion angle, which can be calculated in particular by projection onto the frontal plane.

[0023] Even in the aforementioned advantageous embodiment, the data processing unit can check whether the actual inclination angle and / or actual anteversion angle lie outside a predefined inclination angle range or anteversion angle range, respectively. If so, a corresponding note can be issued as part of the implantation information, which in particular includes a suggestion for implanting the acetabular cup at a different inclination angle and / or anteversion angle relative to the pelvic inlet plane. The data processing unit can base this on the inclination and / or anteversion angle range according to Lewinnek.

[0024] Furthermore, it is advantageous if the data processing device is designed and programmed to receive an inclination and / or anteversion angle of the acetabular axis relative to the pelvic inlet plane. This allows, for example, deviations in the alignment of the acetabular axis from the usual values, such as those resulting from dysplasia, to be taken into account even in the absence of pelvic tilt in the patient. In this case as well, the data processing device can determine an actual inclination and / or anteversion angle relative to the frontal plane, as explained above. The implantation information can include the aforementioned indications regarding the inclination angle range and / or the anteversion angle range, as well as suggestions for different inclination angles and / or anteversion angles.

[0025] Naturally, the data processing device can be designed and programmed in such a way that it can be provided with an inclination and / or anteversion angle chosen by the surgeon, under which he intends to implant the artificial hip socket.

[0026] Preferably, the sensor unit is integrated into the simulation body, or the simulation body encompasses the sensor unit. This allows for a structurally simple design of the instrumentation.

[0027] Advantageously, the sensor unit includes a tilt sensor, particularly for detecting tilt relative to the direction of gravity. When the simulated body is tilted, its change in tilt can be detected, and the magnitude and direction of the tilt angle can be determined from this.

[0028] Additionally or alternatively, the sensor unit may include a magnetic field sensor, in particular for detecting the direction or inclination of the Earth's magnetic field.

[0029] Additionally or alternatively, the sensor unit can include an optical camera, the signal from which the tilting of the simulated object can be determined by the data processing unit. The camera can be integrated into the simulated object and used to track stationary landmarks, determining the magnitude and orientation of the tilt angle based on changes in their position within the camera's field of view. Alternatively, the camera can be positioned externally and directed towards the simulated object to capture the orientation and magnitude of the tilt angle when the object tilts.

[0030] Preferably, the sensor unit is integrated into the data processing unit, which comprises or forms the simulation body. This allows for a particularly simple design.

[0031] The same advantage is preferably achieved by integrating the information unit, in particular the display unit, into the data processing device.

[0032] In a particularly advantageous embodiment of the instrument according to the invention, the data processing device is a tablet computer or a smartphone, and it comprises the guidance unit in the form of a display unit and the sensor unit. Simultaneously, the tablet computer or smartphone can form the simulation body. When the tablet computer or smartphone is tilted, the tilt angle can be determined by the device itself, and the implantation information can be displayed on its display unit.

[0033] It is advantageous if the instrumentation includes a holder for the simulation object, to which the simulation object is fixed or can be fixed. The holder defines the tilting axis, and the simulation object is mounted on the holder so that it can tilt around this axis. This allows for a user-friendly, precise, and reproducible simulation of the inclination of the pelvic inlet plane to the frontal plane. The tilting mounting of the simulation object, particularly a tablet computer or smartphone, on the holder allows it to be easily grasped and tilted.

[0034] The simulation body is preferably clamped and / or snapped into place on the holder, or can be fixed in this way.

[0035] It is advantageous if the mounting includes at least one actuating element that defines the tilting axis for tilting the simulation body. This actuating element engages, for example, with the simulation body or with a receiving element to which the simulation body is clamped and / or snapped into place. The simulation body can then be tilted user-friendly by rotating the actuating element.

[0036] In an advantageous embodiment of the instrument, the holder comprises a first holding element and a second holding element spaced apart from it, between which a receptacle for the simulation body is formed. For example, each holding element can include a rail-shaped receiving element into which the simulation body, such as a tablet computer or a smartphone, is partially inserted. The simulation body is then tiltably mounted between the receiving elements on the holding elements.

[0037] The mount preferably has at least one mounting element for placement on a surface. Preferably, the mount, including the simulation body, is portable and can be freely moved around the room and positioned on a surface by the operator. The mounting element is, for example, a base that defines a mounting level.

[0038] The tilting axis is preferably aligned parallel to a mounting plane defined by at least one mounting element. With a horizontally oriented mounting surface, the simulated body can thus be tilted about a horizontal tilting axis.

[0039] As mentioned at the outset, the invention also relates to a method. A method according to the invention for simulation purposes in hip endoprosthetics is characterized in that an instrument set of the aforementioned type is used, wherein a simulation body that can be tilted about a tilting axis in a spatial reference system is tilted, the magnitude and orientation of a tilting angle when the simulation body is tilted are detected by a sensor unit, a tilting inclination of a human pelvis is simulated in a body reference system in which the pelvic inlet plane of the pelvis is inclined relative to a frontal plane of the body by the tilting angle by a data processing device, and that implantation information dependent on the tilting angle is output to the user at a guidance unit.

[0040] The advantages already mentioned in connection with the explanation of the instrumentation according to the invention can also be achieved with the method according to the invention. To avoid repetition, reference is therefore made to the preceding explanations.

[0041] Advantageous embodiments of the method according to the invention result from the features of the aforementioned advantageous embodiments of the instrumentation according to the invention. These features can be used to define advantageous embodiments of the method, so reference is also made to the preceding explanations in this regard.

[0042] The following description of a preferred embodiment of the invention, in conjunction with the drawing, serves to explain the invention in more detail. The drawing shows: Fig. 1: A perspective view of a human pelvis, illustrating the inclination angle of a hip socket at 0° pelvic tilt; Fig. 2: a perspective view of a human pelvis, which is used to explain the anteversion angle of a hip socket at 0° pelvic tilt; Fig. 3: a lateral view of the pelvis and leg skeleton, with the pelvic inlet plane aligned parallel to a frontal plane; Fig. 4: a lateral view of the pelvis and leg skeleton, with the pelvic inlet plane inclined relative to the frontal plane (anterior); Fig. 5: a perspective view of an instrument set according to the invention, comprising a simulation body, for carrying out the method according to the invention; Fig. 6: another perspective view of the instrument set from Fig. 5 after tilting the simulation body; Fig. 7: the instruments Fig. 5, partly in exploded view; Fig. 8: Views from the ventral, lateral and cranial perspective of a pelvis on a display unit of the simulation body at 0° pelvic tilt; Fig. 9: Views from the ventral, lateral and cranial sides of a pelvis on a display unit of the simulation body at 30° anterior pelvic tilt and Fig. 10: Views from the ventral, lateral and cranial sides of a pelvis on a display unit of the simulation body at 30° posterior pelvic tilt;

[0043] The Fig. 1 and Fig. Figure 2 schematically shows a perspective representation of a human pelvis 10 and its pelvic inlet plane B.

[0044] Fig. Figure 1 further shows a transverse plane T oriented perpendicular to the pelvic inlet plane B and an inclination plane I. The inclination plane I is inclined at an inclination angle 12 relative to the transverse plane and is oriented perpendicular to the pelvic inlet plane B.

[0045] Fig. Figure 2 further shows an anteversion plane A, which is inclined relative to the pelvic inlet plane B by an anteversion angle 14 and is oriented perpendicular to the transverse plane T.

[0046] During implantation, an artificial acetabular cup 16 is typically positioned at a specific inclination angle 12 and anteversion angle 14 with respect to the pelvic inlet plane B to maximize femoral mobility 17 after implantation. This also aims to prevent partial or complete dislocation of the femoral head from the acetabular cup 16 and impingement (bone-on-bone or metal-on-metal contact). For this purpose, Lewinnek recommends inclination angle ranges of 45° ± 10° for the inclination angle 12 and 15° ± 10° for the anteversion angle 14. These angle ranges facilitate the subsequent explanation of the present invention, which, however, is not limited to these definitions.

[0047] The above definition assumes that the pelvic inlet plane B is aligned parallel to a frontal plane F, with this parallelism referring to the standing patient. In this context, the inclination angle 12 refers to an inlet plane of the acetabulum 16 and the anteversion angle 14 to an axis of the acetabulum.

[0048] If the pelvic inlet plane B is parallel to the frontal plane F, the femur 17 has a range of motion to the pelvis 10 which is given by a flexion angle 18 and an extension angle 20 ( Fig. 3).

[0049] However, the pelvic inlet plane B is usually inclined relative to the frontal plane F by a pelvic tilt angle 22 (hereinafter also pelvic tilt), as in Fig. Figure 4 illustrates this. This impairs the range of motion of the femur 17 to such an extent that, for example, in the case of an anterior pelvic tilt 22, the flexion angle 18 is reduced. The extension angle 20 is usually not increased, since the system of pelvis 10 and femur 17 cannot be considered in isolation, but rather muscles and tendons must also be taken into account.

[0050] If the pelvic inclination 22 is disregarded during the implantation of the acetabular cup 16, this can undesirably lead to a restriction of the femoral head's range of motion 17. There is a risk of femoral head dislocation and impingement. Therefore, if the inclination angle 12 and the anteversion angle are aligned solely with respect to the pelvic inlet plane B during the implantation of the acetabular cup 16, the implantation proves to be suboptimal despite adherence to the aforementioned angle ranges for inclination and anteversion, which define the so-called "safe zone".

[0051] In order to clearly demonstrate to a surgeon how the pelvic tilt 22 influences the inclination and anteversion of the acetabulum 16 with respect to the frontal plane F and thus the range of motion, the present invention proposes an instrument set according to the invention, of which in the Fig. Figures 5 to 7 show an advantageous embodiment designated by reference numeral 24, with which the method according to the invention can be carried out as explained below.

[0052] The instrument 24 comprises a preferably portable data processing device 26, which in this case is configured as a tablet computer 28. The data processing device 26 could, for example, also be a smartphone. The tablet computer 28 includes a notification unit 30, which is configured as an optical display unit 32. Furthermore, the tablet computer 28 includes a sensor unit 34, which comprises at least one sensor 36. A signal from the sensor unit 34, based on the at least one sensor 36, can be provided to a processing unit 38 of the data processing device 26. The processing unit 38 comprises, for example, a microprocessor.

[0053] The display unit 32 can show implantation information, as explained above and below. This includes, in particular, representations of the pelvis 10 and information about inclination and anteversion angles depending on a tilt angle of the tablet computer 28.

[0054] The at least one sensor 36 is designed to detect a tilt of the tablet computer 28 in a spatial reference system. For example, the sensor 36 is an inclination sensor that detects tilt and changes in tilt relative to the direction of gravity. The sensor 36 can also be a magnetic field sensor to detect the direction and / or inclination of the Earth's magnetic field. Alternatively, the sensor 36 can be an optical camera pointed at landmarks in the space where the tablet computer 28 is located. When the tablet computer is tilted, the position of the landmarks in the camera's field of view changes, allowing the processing unit 38 to detect a tilt of the tablet computer.

[0055] The instrument set 24 further comprises a holder 40 associated with the tablet computer 28, which in this case comprises two preferably identical holding parts 42, 44. As can be seen in particular from Fig. As can be seen from Figure 7, each holding part 42, 44 has a mounting element 46 for placement on a mounting surface 48. The mounting element 46 accordingly forms a base with a foot section 50 and a holding section 52. The foot sections 50 define a common mounting plane which coincides with a plane formed by the mounting surface 48.

[0056] The foot section 50 is C-shaped. The support section 52 is aligned perpendicular to the foot section 50 (perpendicular to the installation plane) and has a through opening 54 on its side facing away from the foot section 50.

[0057] The through-opening 54 is penetrated by an actuating element 56 in the form of an adjusting screw 58. The adjusting screw 58 defines a tilting axis 60, wherein the retaining parts 42, 44 are positioned and aligned such that a common tilting axis 60 is defined.

[0058] A receiving element 62 is fixed to the adjusting screw 58 on the opposite side of the retaining section 52 and is rotationally fixed to the adjusting screw 58. The receiving element 62 is designed as a C-shaped rail 64 in cross-section.

[0059] The retaining elements 42, 44 are positioned on the mounting surface 48 such that a receptacle for the tablet computer 28 is formed between them and the tilting axes 60 coincide. The tablet computer 28 can be inserted into the receptacle and held clamped between the retaining elements 62. Alternatively, the adjusting screws 58 can be engaged with the tablet computer 28.

[0060] By grasping the tablet computer 28 or by operating one of the adjusting screws 58, the tablet computer 28 can be tilted about the tilting axis 60 ( Fig. 5 and Fig. 6) The magnitude and orientation (forward or backward) of the corresponding tilt angle can be determined using the sensor unit 34.

[0061] The tablet computer 28 forms a simulation body 66 with which the surgeon can simulate an inclination of the pelvic inlet plane B relative to the frontal plane F in a particularly clear manner. In particular, the tablet computer 28 is designed and programmed such that the influence of the pelvic inclination 22 on the inclination and anteversion of the acetabulum 16 can be calculated and clearly displayed on the display unit 32. For further explanation, particular reference is made below to the Fig. 8 to 10 referred.

[0062] The tablet computer 28 can be moved from an initial relative position to the holder 40 ( Fig. 5) be tilted around the tilting axis 60 ( Fig. 6) The invention is not limited to the assumption that the initial relative orientation corresponds to a 0° pelvic tilt 22, in which the pelvic inlet plane B is parallel to the frontal plane F. The user can preferably define which relative orientation of the tablet computer 28 and the mount 40 corresponds to the tilting axis 60 using appropriate simulation software stored on the tablet computer 28.

[0063] Before tilting the tablet computer 28, the display unit 32 presents a model of the pelvis 10 at 0° pelvic tilt, specifically in the ventral, lateral and cranial viewing directions ( Fig. 8) Furthermore, an axis 68 of the acetabulum 69 is displayed on the display unit 32. It is assumed that the acetabulum 16 is implanted at an inclination angle 12 and anteversion angle 14 specified by the surgeon with respect to the pelvic inlet plane B, for example, the aforementioned 45° and 15° respectively, with the axis of the acetabulum 16 being aligned with the axis 68 of the acetabulum 69. The display unit 32 can show the inclination and anteversion with respect to the frontal plane F, which in this case are identical, on an output field 70.

[0064] After tilting the simulation body 66 formed by the tablet computer 28 in the spatial reference frame, a pelvic tilt 22 can be simulated in magnitude and orientation, corresponding in magnitude and orientation to the tilt angle of the simulation body 66 about the tilt axis 60. Accordingly, a pelvic tilt 22 is simulated depending on the tilt angle, whereby the pelvis 10 is, in effect, computationally tilted.

[0065] The display unit 32 shows a model of the pelvis 10 again in ventral, lateral and cranial views, which is displayed according to Fig. 9 exhibits an anterior pelvic tilt of +30°. This pelvic tilt is simulated by tilting the simulation body 66 forward by a tilt angle of 30° around the tilt axis 60 towards the surgeon. The axis 68 is represented accordingly, and it is assumed that the acetabular cup 16 is still implanted at the specified inclination angle 12 and the specified anteversion angle 14 with respect to the pelvic inlet plane B.

[0066] The simulated pelvic tilt 22 can be displayed on the display unit 32 in terms of magnitude and orientation. Furthermore, the tablet computer 28 can calculate the influence of the pelvic tilt on the inclination and anteversion of the acetabulum 16 with respect to the frontal plane F. For example, the inclination and anteversion are calculated by projection onto the frontal plane F. The corresponding angles can be displayed on the output field 70.

[0067] In particular, the tablet computer 28 can determine whether the calculated inclination and anteversion lie outside the specified angle range for inclination and anteversion, respectively, with the angle ranges being defined in relation to the frontal plane F. This allows the surgeon to receive a notification that the acetabular cup 16 is being implanted in the pelvis 10 in such a way that it is outside the "safe zone." The surgeon can thus determine that if the selected inclination angle 12 and anteversion angle 14 are maintained, restricted freedom of movement is likely. Furthermore, there is a risk of dislocation and impingement.

[0068] Since the axis 68 is also displayed on the display unit 32, this is particularly clear for the surgeon; an experienced surgeon can already recognize the influence of the pelvic tilt 32 on the freedom of movement by the position of the axis 68 on the display unit 32.

[0069] The tablet computer 28 can also calculate the inclination angle 12 and the anteversion angle 14 at which the acetabulum 16 is to be implanted with respect to the pelvic inlet plane B for a given pelvic tilt angle 22, so that the acetabulum 16 is implanted within the "safe zone" taking the pelvic tilt 22 into account. Corresponding suggestions for the inclination angle 12 and the anteversion angle 14, as well as corresponding angle ranges, can be displayed on the display unit 32, for example, on the output field 70.

[0070] Fig. Figure 10 shows the implantation information on the display unit 32. The implantation information includes the model of the pelvis 10 in ventral, lateral, and cranial views, assuming a posterior pelvic tilt of -30°. This pelvic tilt is simulated by tilting the simulation body 66 posteriorly about the tilt axis 60 away from the surgeon by a tilt angle of -30°. The axis 68 is also shown, and it is also assumed that the acetabulum 16 is implanted at the specified inclination angle 12 and the specified anteversion angle 14 with respect to the pelvic inlet plane B.

[0071] In this case, too, the tablet computer 28 can determine the influence of the pelvic tilt on the inclination and anteversion with respect to the frontal plane F and display the corresponding values ​​on the display unit 32, for example in the output field 70. It can also determine whether the calculated inclination and the calculated anteversion are outside the specified respective angle ranges, and if necessary, a notification can be issued regarding the need to change the inclination angle 12 or the anteversion angle 14 for the implantation of the acetabular cup 16.

[0072] The Fig. 8, Fig. 9 and Fig. Figure 10 illustrates, using exemplary pelvic tilts of 0°, +30° and -30°, that pelvic tilt can significantly influence inclination and anteversion.

[0073] Assuming an anteversion angle of 15° and an inclination angle of 45° at 0° pelvic tilt, a 30° anterior pelvic tilt with respect to the frontal plane F results in an anteversion angle of approximately -16° and an inclination angle of approximately 42°. Therefore, retroversion is already present, and the anteversion is far outside the "safe zone".

[0074] With a posterior pelvic tilt of -30°, the anteversion is approximately 39° and the inclination approximately 57° with respect to the frontal plane F. The anteversion is therefore well outside the "safe zone", and the inclination is already close to the edge of the "safe zone".

[0075] The instrument set 24 according to the invention allows the user to determine, in a clear and non-invasive manner, particularly pre- and intraoperatively, the influence of the pelvic tilt 22 on the inclination and anteversion of a hip socket 16 to be implanted. This is possible in real time and for minimal tilt angles.

[0076] It is also conceivable that the surgeon transmits experimentally determined values ​​for the pelvic tilt 22 to the tablet computer 28 before the simulation and does not assume a 0° pelvic tilt 22 during the simulation. The tablet computer 28 can be provided with the patient's pelvic tilt, which can be determined, for example, pre- or intraoperatively by X-ray (e.g., a sagittal view), by ultrasound, or by palpation of the standing or supine patient.

[0077] Even without simulating the pelvic tilt, the tablet computer 28 can determine the influence of this pelvic tilt on the anteversion and inclination at the display unit 32 and display corresponding implantation information on the display unit 32. Specifically, the pelvis 10 with axis 68 and the anteversion and inclination with respect to the frontal plane F are displayed on the display unit 32. Furthermore, instructions can be displayed if the anteversion and / or inclination are outside the respective angular range of the "safe zone" and, if necessary, a different inclination angle 12 or anteversion angle 14 can be suggested.

[0078] It is also conceivable that the surgeon specifies to the tablet computer 28 the inclination angle 12 and the anteversion angle 14 with respect to the pelvic inlet plane B at which the acetabular cup 16 is to be implanted, these values ​​differing from the aforementioned 45° and 15°, respectively. This is particularly advantageous if a pelvic tilt other than 0° has already been determined for the patient, allowing the surgeon to take the pelvic tilt and its influence on a change in the "safe zones" with respect to the frontal plane F into account. In this case as well, the instrument set 24 can assist the surgeon in determining whether, considering the pelvic tilt, the selected anteversion and inclination allow for a sufficient range of motion after implantation of the acetabular cup 16.

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