Surgical saw guide

Abstract

Surgical saw guide (10) for determining a cutting plane (16) on a femur (18) for the implantation of a hip endoprosthesis stem, comprising a saw template (12), wherein the surgical saw guide comprises a holding device (14) for holding and minimally invasively inserting the saw template (12) into a patient body (20), characterized in that the saw template (12) has an outer contour that is similar to the hip endoprosthesis stem to be implanted.

Description

The present invention relates to a surgical saw jig for determining a sectional plane on a femur for the implantation of a hip joint endoprosthesis stem, comprising a saw jig, wherein the surgical saw jig comprises a holding device for holding and for minimally invasive insertion of the saw jig into a patient body.For the preparation of a femur, it is known to use a surgical saw jig of the type described at the beginning after opening the patient's body in order to define the cutting or resection plane where the femur head is to be cut off so that the hip joint endoprosthesis stem can be inserted into the medullary cavity of the femur forming a cavity.However, the known saw gauges are relatively large and are not suitable for minimally invasive surgical interventions for the implantation of a hip joint endoprosthesis.WO 2005 / 110250 A1 describes a patient-specific osteotomy template for the precise resection of the femur head within the scope of an operation for replacing a hip joint. An osteotomy guide for displaying the femoral head resection on a femur is disclosed in US 2007 / 0083214 A1. An endoscopic insertion instrument atrium is known from DE 198 51 370 C2. A patella reference device is described in DE 203 03 499 U1.It is therefore an object of the present invention to improve a surgical saw jig of the type described at the beginning in such a way that it can be better handled in particular for minimally invasive surgical interventions.This object is achieved according to the invention in a surgical saw jig of the type described at the beginning in that the saw jig has an outer contour which is similar to the hip joint endoprosthesis shank to be implanted.The provision of the holding device makes it possible to insert the saw template into the patient's body without the latter having to be held by an operator or a person assisting him. After the holding device has been detected by an operator, the saw template can thus be introduced into the patient's body, for example, through a small incision, in order to determine the optimum cutting plane or resection plane on the femur. In order to be able to easily and securely determine the cutting plane for removing the femur head with the sawing template, the sawing template according to the invention has an outer contour which is similar to the hip joint endoprosthesis stem to be implanted. Thus, the saw template can be easily brought from the outside to the femur into a position or with an orientation which corresponds to the later orientation of the hip joint endoprosthesis shaft to be implanted.Advantageously, the saw template and the holding device can be detachably connected to one another. This makes it possible to use the holding device optionally with different templates. In particular, differently shaped saw templates can be provided, which together form a saw template set. Together with the holding device, the saw templates thus overall form a saw template set comprising the holding device and a plurality of saw templates. It is thus sufficient to provide a single holding device also for a plurality of saw templates in order to be able to select these according to the size of the patient and of the hip joint endoprosthesis to be implanted and to connect them to the holding device. Furthermore, with a corresponding configuration of the saw template and the holding device, a connection in different positions can thus be possible, so that the saw template can be used in particular on the left as well as on the right for determining the cutting plane on the femur.The saw template and the holding device can be connected to one another in a particularly simple manner if a coupling device is provided for the detachable connection thereof.It is advantageous if the coupling device comprises first and second coupling elements which are arranged and / or formed on the one hand on the saw template and on the other hand on the holding device, and if the first and second coupling elements are in frictional and / or positive engagement in a connection position in which the saw template and the holding device are connected to one another and are out of engagement in a release position in which the saw template and the holding device are separated from one another. By providing the first and second coupling elements on the saw template or the holding device, respectively, these can be coupled or connected to one another in a simple and secure manner.The construction of the coupling device becomes particularly simple if one of the coupling elements is designed in the form of a coupling receptacle and if another coupling element is designed in the form of a coupling projection corresponding to the coupling receptacle. The coupling receptacle and the coupling projection can optionally be provided on the saw template or on the holding device.A defined connection between the saw template and the holding device can be advantageously achieved in that the coupling device is designed in the form of a latching connection device and in that the first and second coupling elements are designed in the form of first and second latching elements. In particular, the latching elements can be designed such that they can be brought into engagement with one another in defined positions and can thus also specify a relative position between the saw template and the holding device in a defined manner.Preferably, the coupling device is at least partially symmetrically designed such that the saw template and the holding device can be connected to one another in at least two different relative positions. This makes it possible, in particular if the saw template is formed similarly to a hip joint endoprosthesis stem at least in its outer contour and is therefore asymmetrically shaped, to connect the holding device to the saw template in two different ways, so that the saw template can be used selectively for the left or the right femur. However, it is even better if the coupling device specifies a symmetry which enables a connection of the saw template and the holding device in four or even more relative positions. This allows the holding device to be connected to the saw template in such a way that it can be selectively connected to an operator with a left hand or a right hand independently of a standing position of the operator relative to the patient.The construction of the coupling device becomes particularly simple if the first and / or the second coupling element are configured symmetrically. The higher the symmetry thereof, the greater the number of possible relative or connecting positions between the saw template and the holding device. In other words, this means that the number of possible connection positions depends on the degree of symmetry of the coupling elements.The first and / or the second coupling element are expediently configured symmetrically with respect to an axis of symmetry. Alternatively, they can also be formed symmetrically with respect to one or more planes of symmetry.Preferably, the axis of symmetry is an N-fold axis of symmetry. This is to be understood in the mathematical sense in such a way that a rotation of the coupling elements relative to one another about the axis of symmetry transfers the coupling elements which can be brought into engagement with one another into themselves. The required angle of rotation corresponds here to 360° / N, that is to say, in the case of a 2-fold axis of symmetry, a rotation of the coupling elements relative to one another about the axis of symmetry by 180°.Advantageously, the count N of the axis of symmetry has a value in a range from 2 to 12. The saw template and the holding device can thus be connected to one another in at least 2 and up to 12 different connection positions. By appropriate configuration of the coupling elements, the number can additionally be doubled, for example by the coupling elements also being formed mirror-symmetrically with respect to a mirror plane oriented perpendicularly to the axis of symmetry.It is advantageous if the saw template has a front and rear side and if the holding device can be arranged in the connecting position so as to project selectively from the front or from the rear side. This makes it possible to use the saw template optionally with one and the same holding device for determining the cutting plane on the left femur and on the right femur.In order to ensure that the saw template cannot be detached from the holding device, it is advantageous if the saw template comprises a securing device for defined securing of the coupling device in the connecting position.The construction of the securing device becomes particularly simple if it comprises first and second securing members which are arranged and / or formed on the one hand on the saw template and on the other hand on the holding device, and if the first and second securing members are in engagement in a non-positive and / or positive-locking manner in a securing position in which the saw template and the holding device assume the connecting position and are out of engagement in a decoupling position in which the first and second coupling elements can be disengaged. In order to release the coupling elements from one another, the securing device therefore only has to be transferred from the securing position into the decoupling position.The saw jig can be produced particularly easily if one of the securing members is designed in the form of a securing receptacle and if the other securing member is designed in the form of a corresponding securing projection.The saw template can be secured to the holding device in the connecting position in a simple and defined manner if the securing device is designed in the form of a latching connection device and if the first and second securing members are designed in the form of first and second latching elements.The construction of the surgical saw jig is possible in a particularly compact manner if the first and / or second securing members are arranged and / or formed on the first and / or second coupling elements. The coupling and securing functions of the saw jig can thus be realized in the smallest space.It is advantageous if the first and second securing members are movable relative to one another for transferring the securing device from the securing position into the disengagement position and vice versa. By a simple relative movement, for example a displacement or pivoting, of the securing members relative to one another, the surgical saw jig can thus be transferred from the securing position into the coupling position and vice versa.Preferably, the saw template and the holding device are held prestressed against one another in the connecting position. For example, they can be positioned relative to one another in a defined manner.The saw template and the holding device can be prestressed against one another in a particularly simple manner in the connecting position if a prestressing device is provided for prestressed holding of the same.The construction of the pretensioning device becomes particularly simple if it comprises at least one pretensioning member for the pretensioning holding of the saw template and the holding device against one another in the connecting position.Preferably, the at least one prestressing element is designed to be elastic. It is advantageous if it is designed in the form of a spring element. All forms of springs, for example leaf springs or spiral springs, are conceivable.The construction of the surgical saw jig becomes particularly compact if the at least one prestressing element comprises or carries the first or the second securing element. This makes it possible to press the securing members against one another in the securing position in a manner pre-tensioned by means of the at least one pre-tensioning member.The surgical saw jig can be handled easily and reliably if the holding device comprises a grip region. The holding device can be easily and securely held on the grip region. The grip region can be designed in particular ergonomically.The holding device advantageously comprises a shank portion extending away from the grip region. The shaft section allows a distance between the grip region and the saw template to be selected to be sufficiently large so that sufficient space remains for further instruments in the region of the incision through which the saw template is to be introduced into the patient's body. The hand of an operator of the saw jig can be held away from the incision as far as possible.In order to improve the ergonomicness of the saw jig, it is advantageous if the shank portion is curved at least in sections.The shaft section advantageously comprises or carries at one end one of the coupling elements. The shank portion can thus carry the grip region at one end and a coupling element at the other end, by means of which coupling element the shank portion can be connected to the saw template.In order to identify an orientation of the saw template in a simple and reliable manner, even if it is inserted into the patient's body and is no longer visible, it is advantageous if the grip region, in the connecting position, extends parallel or substantially parallel to a plane defined by the saw template.It is furthermore advantageous if the saw template defines a prosthesis socket longitudinal axis and if the grip region extends parallel or substantially parallel to the prosthesis socket longitudinal axis in the connection position. Thus, an orientation of the saw template can be derived directly from an orientation of the grip region.Preferably, the saw template comprises a scale portion. It is advantageous if this protrudes from the saw template on the proximal side. The scale section can have markings, in particular, which enable an operator to determine a section plane in a reproducible manner depending, for example or with respect to structures of the femur to be machined. The saw template may further comprise further scale portions which may be formed, for example, by applying corresponding markings to outer edges of the saw template.It is advantageous if the scale section extends parallel or substantially parallel to the prosthesis socket longitudinal axis. Thus, again, an orientation of the saw template can also be deduced from an orientation of the scale section.Preferably, the sawing template is plate-shaped. This allows the saw template to be inserted into the patient's body through a minimally small incision. Furthermore, it can also be produced in a simple manner.The following description of preferred embodiments of the invention serves to explain it in more detail in conjunction with the drawing. The following are shown: FIG. 1 is a schematic illustration of the use of a surgical saw jig on a patient; FIG. 2 : a perspective illustration of the surgical saw jig from FIG. 1 ; FIG. 3 : an enlarged perspective view of the saw template and of a distal end of the holding device separated from the saw template; FIG. 4 is a sectional view taken along line 4- 4 in FIG. 3 ; FIG. 5 : an enlarged view of the detail A in FIG. 5 ; FIG. 6 is a sectional view taken along line 6- 6 in FIG. 5 ; FIG. 7 shows a schematic illustration of the saw template when it is placed on the femur to be partially re-resected; and FIG. 8 : shows a schematic illustration of a total of four possible connection positions between the saw template and the holding device.FIGS. 1 and 2 show by way of example a surgical saw jig, which is provided overall with the reference numeral 10 and comprises a saw jig 12 and a holding device 14. The saw template 12 serves for determining a cutting plane 16 on a femur 18 for the implantation of a hip joint endoprosthesis shaft, not shown in the figures. This forms part of a hip joint endoprosthesis which is to be inserted into the body of a patient 20 for replacing a damaged hip joint 22 thereof.The saw template 12 and the holding device 14 can be detachably connected to one another by means of a coupling device 24.The sawing template 12 is plate-shaped and has an outer contour 26 which is similar or approximately similar to the outer contour of the hip joint endoprosthesis shank to be implanted. It defines a prosthesis shaft longitudinal axis 28. A distal end 30 of the saw template 12 is rounded and widens in a wedge-shaped manner in the proximal direction. A longitudinal edge 32 extends substantially parallel to the prosthesis longitudinal axis 28, a further lateral edge 34 is slightly concavely curved and inclined relative to the prosthesis socket longitudinal axis 28, wherein its distance from the longitudinal edge 32 increases in the proximal direction. A plurality of markings 36 for forming a scale section 38 are provided on the side edge 34, namely both on a front side 40 and on a rear side 42 of the saw template 12, the longitudinal edge 32 forming part of a further, flat, cuboidal scale section 44 which extends parallel to the prosthesis socket longitudinal axis 28 in the proximal direction and defines a proximal end 46 of the saw template 12. Further markings 48 are provided on the scale section 44. Distances between the markings 36 and 48 are each preferably 1 mm. The length of the scale section 44 is about 2 cm. The markings 36 and 48 are formed by laser marking on the sawing template, which is preferably produced from a sterilizable metal.The coupling device 24 comprises a first coupling element 50 and a second coupling element 52. The first coupling element 50 is formed on the saw template 12 in the form of a slot-shaped coupling receptacle 54 which extends perpendicularly to the prosthesis socket longitudinal axis 28 starting from the longitudinal edge 32. The second coupling element 52 is formed on a cuboidal coupling body 56 of the holding device 14. The coupling body 56 forms a distal end of the holding device 14. The second coupling element 52 is designed in the form of a cuboidal coupling projection 58, which can be introduced in a positive fit into the coupling receptacle 54 in a direction transverse to the prosthesis socket longitudinal axis 28. The coupling projection 58 is defined by two mirror-symmetrically formed grooves 60 on the coupling body 56 which point away from each other. The lateral surfaces which delimit the grooves 60 and extend parallel to each other define upper and lower guide surfaces 62, 64, the distance between which corresponds to the thickness of the saw template 12. The upper and lower guide surfaces 62, 64 abut the front 40 and rear 42 sides, respectively, when the coupling elements 50 and 52 are engaged. The coupling projection 58 is furthermore guided on two side surfaces 66 and 68 of the coupling receptacle 54 running parallel to one another.Both coupling elements 50 and 52 are configured symmetrically, namely with respect to an axis of symmetry 70 which runs perpendicular to a plane defined by the saw template 12. The axis of symmetry 70 is a 2-fold axis of symmetry 70. this means that the coupling elements 50 and 52 are furthermore also designed mirror-symmetrically to two mirror planes which are perpendicular to one another and contain the axis of symmetry 70.When the coupling elements 50 and 52 are in engagement in a force-fit and / or form-fit manner, they assume the so-called connecting position. For defined securing of the coupling device 24 in the connecting position, the saw jig 10 further comprises a securing device 72. The securing device 72 comprises first and second securing members 74 and 76, which are arranged or formed on the saw template 12 on the one hand and on the holding device 14 on the other hand. Two first securing members 74 are designed in the form of securing receptacles 78 on the second coupling element 52 in the form of flat depressions. They are likewise formed symmetrically with respect to the axis of symmetry 70 and point away from one another in opposite directions. The second securing member 76 is designed in the form of a securing projection 80. The securing device 72 is configured overall in the form of a latching connection device 82, wherein the first and second securing members 74 and 76 each form latching elements corresponding to one another.The first and second securing members 74 and 76 are movable relative to each other for transferring the securing device 72 from a securing position, in which the saw template 12 and the holding device 14 assume the connecting position, into a disengagement position, in which the first and second securing members 74 and 76 are disengaged and the first and second coupling elements can be disengaged.The saw jig 10 further comprises a biasing device 84 for biasingly holding the saw jig 12 and the holding device 14 against each other in the connecting position. The biasing device 84 comprises a biasing member 86 in the form of a spring element 88, the spring element 88 being in the form of a leaf spring and extending parallel to the coupling receptacle 54 in an L-shaped slot formed in the saw template 12 and open in the direction of the coupling receptacle 54. As a result, the side surface 66 is partially perforated. At one end, the spring element 88 carries the spherical securing projection 88, which projects somewhat into the coupling receptacle 54 in a basic position. The other end of the spring element 88 is connected to the sawing template 12. Overall, the saw template 12 is formed in one piece and thus comprises the second coupling element 52 and the prestressing device 84 and the second securing member 76.When the coupling projection 58 is introduced into the coupling receptacle 54, the securing projection 80 slides on the coupling projection 58 and is moved out of the coupling receptacle 54 counter to an action of the spring element 88. Due to the prestress, the securing projection 80 is pressed into the securing receptacle 78 as soon as the coupling body 56 has been moved forward to such an extent that the securing receptacle 78 is situated opposite the securing projection 80 so that the latter can enter the securing receptacle 78. The saw jig then assumes the securing position which is illustrated in FIG. 6.The holding device 14 comprises a handle 92 which defines a grip region 94 for holding the holding device 14 and forms a proximal end of the holding device 14. A shaft 98 forming a holding section 96 extends between the coupling body 56 and the handle 92, and the shaft 98 has a straight shaft section 100 which directly adjoins the coupling body 56 and is inclined by approximately 10° to 15° with respect to the axis of symmetry 70. On the proximal side, the shank portion 100 is adjoined by a curved curved curved portion 102, which in turn merges into a rectilinear shank portion 104, which is adjoined by the grip 92 on the proximal side. The curved section 102 has a curvature such that a longitudinal axis 106 of the handle 92 extends parallel to the prosthesis socket longitudinal axis 28.Due to the special design of the coupling device 24, the holding device 14 can be connected to the saw template 12 in a total of four different connection positions, namely in such a way that in two connection positions the shank 98 protrudes from the front side 40 and in two further positions protrudes from the rear side 42. Further, the handle portion 94 may optionally face toward or away from the end 30 when the retainer 14 and the saw template 12 are connected together. The four connection positions described are schematically shown in FIG. 8.The surgical saw jig 10 enables the saw jig 12 to be used to determine the cutting plane 16 on both the left and right femurs of the patient 20. An operator can also optionally connect the holding device 14 to the saw template 12 in such a way that, after the saw template 12 has been introduced into the body of the patient 20 and up to the femur 18, the handle 92 points either toward the feet of the patient 20 or in the direction of the head thereof. Due to the bending of the shank portion 100 relative to the axis of symmetry 70, the incision for inserting the saw template 12 on the body of the patient 20 remains substantially freely accessible. Due to the parallel orientation of the handle 92 to the prosthesis socket longitudinal axis 28, it is possible to draw a conclusion directly from the orientation of the handle 92 as to the orientation of the saw template 12 in the interior of the body of the patient 20, even if the saw template 12 should no longer be visible.All parts of the saw jig 10 are preferably made of steam-sterilizable materials.

Claims

Surgical saw jig (10) for determining a cutting plane (16) on a femur (18) for the implantation of a hip joint endoprosthesis stem, comprising a saw jig (12), wherein the surgical saw jig comprises a holding device (14) for holding and minimally invasive insertion of the saw jig (12) into a patient body (20), characterized in that the saw jig (12) has an outer contour which is similar to the hip joint endoprosthesis stem to be implanted.Surgical sawing jig according to Claim 1, characterized in that the sawing jig (12) and the holding device (14) can be detachably connected to one another.Surgical saw jig according to claim 1 or 2, characterised bya coupling device (24) for releasably connecting the saw jig (12) and the holding device (14).Surgical saw jig according to claim 3, characterised in that the coupling device (24) comprises first and second coupling elements (50, 52) which are arranged and / or formed on the one hand on the saw jig (12) and on the other hand on the holding device (14), and in that the first and second coupling elements (50, 52) are in frictional and / or positive engagement in a connection position in which the saw jig (12) and the holding device (14) are connected to one another and are out of engagement in a release position in which the saw jig (12) and the holding device (14) are separated from one another.Surgical saw jig according to claim 4, characterised in that one of the coupling elements (50) is designed in the form of a coupling receptacle (54) and in that another coupling element (52) is designed in the form of a coupling projection (58) corresponding to the coupling receptacle (54).Surgical saw jig according to claim 4 or 5, characterised in that the coupling device (24) is designed in the form of a latching connection device and in that the first and second coupling elements (50, 52) are designed in the form of first and second latching elements.Surgical saw jig according to one of Claims 3 to 6, characterized in that the coupling device (24) is at least partially of symmetrical design in such a way that the saw jig (12) and the holding device (14) can be connected to one another in at least two different relative positions.Surgical saw jig according to one of Claims 4 to 7, characterized in that the first and / or the second coupling element (50, 52) are of symmetrical design.Surgical saw jig according to claim 8, characterised in that the first and / or the second coupling element (50, 52) are formed symmetrically with respect to an axis of symmetry (70).Surgical saw jig according to claim 9, characterised in that the axis of symmetry (70) is an N-fold axis of symmetry (70).Surgical saw jig according to claim 10, characterised in that the count N of the axis of symmetry (70) has a value in a range from 2 to 12.Surgical saw jig according to one of the preceding claims, characterized in that the saw jig (12) has a front side and a rear side (40, 42), and in that the holding device (14) can be arranged in the connecting position so as to project selectively from the front side or from the rear side (40, 42).Surgical saw jig according to one of Claims 3 to 12, characterized bya securing device (72) for the defined securing of the coupling device (24) in the connecting position.Surgical saw jig according to claim 13, characterised in that the securing device (72) comprises first and second securing members (74, 76) which are arranged and / or formed on the one hand on the saw jig (12) and on the other hand on the holding device (14), and in that the first and second securing members (74, 76) are in frictional and / or positive engagement in a securing position in which the saw jig (12) and the holding device (14) assume the connecting position and are out of engagement in a disengagement position in which the first and second coupling elements (50, 52) can be disengaged.Surgical saw jig according to claim 14, characterised in that one of the securing members (74) is designed in the form of a securing receptacle (78) and in that the other securing member (76) is designed in the form of a corresponding securing projection (80).Surgical saw jig according to claim 14 or 15, characterised in that the securing device (72) is designed in the form of a latching connection device (82), and in that the first and second securing members (74, 76) are designed in the form of first and second latching elements.Surgical saw jig according to one of Claims 14 to 16, characterized in that the first and / or second securing members (74, 76) are arranged and / or formed on the first and / or second coupling elements (50, 52).Surgical saw jig according to one of Claims 14 to 17, characterized in that the first and second securing members (74, 76) can be moved relative to one another in order to transfer the securing device (72) from the securing position into the decoupling position and vice versa.Surgical saw jig according to one of Claims 4 to 18, characterized in that the saw jig (12) and the holding device (14) are held prestressed with respect to one another in the connecting position.Surgical saw jig according to one of Claims 4 to 19, characterized bya prestressing device (84) for prestressed holding of the saw jig (12) and the holding device (14) with respect to one another in the connecting position.Surgical saw jig according to claim 20, characterised in that the biasing device (84) comprises at least one biasing member (86) for biasingly holding the saw jig (12) and the holding device (14) against each other in the connecting position.Surgical saw jig according to claim 21, characterised in that the at least one prestressing element (86) is designed in the form of a spring element (88).Surgical saw jig according to claim 21 or 22, characterised in that the at least one prestressing member (86) comprises or carries the first or the second securing member (76).Surgical saw jig according to one of the preceding claims, characterized in that the holding device (14) comprises a grip region (94).Surgical saw jig according to claim 24, characterised in that the holding device (14) comprises a shank portion (96) extending away from the grip region (94).Surgical saw jig according to claim 25, characterised in that the shank portion (96) is curved at least in sections.Surgical saw jig according to claim 25 or 26, characterised in that the shank portion (96) comprises or carries at one end one of the coupling elements (52).Surgical saw jig according to one of Claims 24 to 27, characterized in that, in the connecting position, the grip region (94) extends parallel or substantially parallel to a plane defined by the saw jig (12).Surgical saw jig according to one of the preceding claims, characterized in that the saw jig (12) defines a prosthesis shaft longitudinal axis (28), and in that the grip region (94) extends parallel or substantially parallel to the prosthesis shaft longitudinal axis (28) in the connecting position.Surgical sawing jig according to one of the preceding claims, characterized in that the sawing jig (12) comprises a scale section (44) which projects proximally from the sawing jig (12).Surgical saw jig according to claim 30, characterised in that the scale section (44) extends parallel or substantially parallel to the prosthesis shaft longitudinal axis (28).Surgical sawing jig according to one of the preceding claims, characterized in that the sawing jig (12) is of plate-shaped design.

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