Patent Application
20220125440
This invention relates to a surgical device and method for performing a controlled resection of the neck of a femur during a hip replacement procedure.
Hip replacement is a surgical procedure in which the hip joint is replaced by a prosthetic implant. In total hip replacement surgery, a patient's natural hip is replaced by an acetabular cup component that replaces the acetabular socket and a femoral component that replaces the femoral head.
During such a surgical procedure, a diseased portion of the femur is excised, usually by removing the femoral head prior to milling of the calcar face. A prosthetic femoral component and a prosthetic femoral head replace the natural structures that are surgically removed. The positioning of the femoral component of the prosthesis is important to ensure proper fit and smooth rotation of the femoral head within its socket (i.e., the acetabular shell).
If the surgeon removes too much of the femur at the resection stage, joint tension will have to be manipulated during later stages of the surgical procedure. This can be achieved by increasing head offset or by switching to a high offset neck trial. Both of these approaches would deviate from the optimal surgical plan, potentially increasing the risk of poor post-surgery biomechanics and patient outcome.
Not removing enough bone can make it harder to mill the calcar face effectively, increase bone fragments in the wound space and reduce the performance and life of the calcar mill instrument. Additionally, this leads to inefficiency in the surgical process, associated costs and a reduction in the free space within the wound cavity.
When performing joint reconstruction, such as hip replacement surgery, it is important that the pre-surgical geometry of the bone structure is replicated in the post-surgical structure. It is important to maintain the natural joint biomechanics, ensuring proper joint and soft tissue balancing. If this is not achieved, the result can be higher joint forces, and overall joint instability.
It is therefore necessary to ensure that orthopedic implant structures are properly placed within a patient. In the case of hip joint prostheses, it is important that the native anatomic centre of rotation of the femoral head within the acetabular shell be located and maintained during the implantation of the replacement structure. Misplacement of the centre of rotation during implantation of the femoral component of the hip joint prosthesis can affect the patient's leg length, which can lead to a very unsatisfactory result for the patient.
It is important in primary total hip arthroplasty to determine the natural offset and neck length of the femoral head by measurement. Offset can be measured from a point on the greater trochanter to the centre of the femoral head. Neck length can be measured from a point of the lesser trochanter to the centre of the femoral head.
U.S. Pat. No. 6,258,097 discloses an orthopaedic instrument for comparing post-surgical joint geometry to pre-surgical joint geometry. The instrument includes a head chuck that can be secured to the ball of a ball joint, and an arm having reference indicia thereon. Markings indicative of the pre-surgical joint geometry are made on the bone with reference to the centre of the ball joint. After replacement with a prosthetic ball, the post-operative geometry is verified by securing the head chuck to the prosthetic ball, and comparing the location of the bone markings against the reference indicia on the arm. As needed, adjustments are made in the prosthetic components.
There remains a need for surgical instruments that will assist surgeons to resect the femoral neck at the appropriate resection plane in order to reproduce within the artificial joint the hip's anatomic centre of rotation. Furthermore, the current resection guides do not take into account the variety of head offsets that can be templated and so leaves the surgical procedure open to an increase risk of error.
According to a first aspect of the invention there is provided a surgical device for performing a controlled resection of the neck of a femur during a hip replacement procedure, the surgical device comprising:
The aperture may be dimensioned for receiving a femoral head of the femur. The aperture may be substantially oval or circular. In some constructions, the aperture may be dimensioned to receive a securing element, for example a bone pin, for securely mounting the template on an outer surface of the femoral head.
In some constructions, the frame comprises a base portion from which a single arm may extend in a proximal direction. The template is connected to the frame via the arm. For example, the arm may comprise a channel, with a portion of the template being slidably received within the channel. The portion of the template that may be slidably received within the channel may be a perimeter edge of the template.
In some constructions, the channel is an open ended slot extending from a free end of the arm along at least a part of the length of the arm in a distal direction towards the base portion. As such, the portion of the template that is received within the slot is sandwiched between an upper section of the arm and a lower section of the arm. In some constructions, the portion of the template that is received within the slot is a perimeter edge of the template.
In order to reduce inventory of surgical instruments, advantageously the surgical device of the invention is designed to be used on the right and left hip, and for a posterior approach or an anterior approach. Therefore, in some constructions the frame may include a pair of spaced apart arms, with each arm extending from the base portion in a proximal direction. The spaced apart arms may be substantially parallel. The frame may be generally U-shaped.
The template is connected to frame via the pair of arms.
Again, each arm of the pair of arms may comprise a channel, with a first portion of the template being slidably received within the channel within the first arm, and a second portion of the template being slidably received within the channel within the second arm. In some constructions, the channel is an open ended slot extending in a distal direction from a free end of each arm of the pair of arms, along at least a part of the length of each arm. The portion of the template that is received within the slot is therefore sandwiched between an upper section and a lower section of the arm. In some constructions, the portion of the template that is received within the slot is a perimeter edge of the template.
The resection guide may extend distally from the base portion of the frame. The resection guide may include a first surface that indicates a resection plane for a standard offset neck. The resection guide may also include a second surface that indicates a resection plane for a high offset neck.
The resection guide may comprise a foot that extends distally from the base portion of the frame.
In order to reduce inventory of surgical instruments, advantageously the surgical device of the invention is designed to be used on the right and left hip, and for a posterior approach or an anterior approach. Therefore, in some constructions the frame includes two resection guides that are mirror images of each other. For example, the frame may include a first resection guide that comprises a first foot, and a second resection guide that comprises a second foot. Each foot may include a first surface that indicates a resection plane for a standard offset neck, and a second surface that indicates a resection plane for a high offset neck.
Prior to resecting the femoral neck, it may be advantageous for a surgeon to be able to easily establish the location of the resection plane along the femoral neck axis that will result in a distinct femoral head offset. This distinct femoral head offset may correspond to the anatomical femoral head offset. Accordingly, the surgical device according to the invention may include a slidable connection that is indexed such that resection guide can be located at plurality of discrete positions along the femoral neck axis. Each discrete position may relate to a distinct femoral head offset.
As a non-limiting example, the slidable connection may be indexed such that the resection guide can be located along the femoral neck axis at three discrete positions. Positioning of the resection guide on the femoral neck at the first discrete position will indicate to the surgeon the location of a resection plane that will provide a first femoral head offset. Positioning of the resection guide on the femoral neck at the second discrete position will indicate to the surgeon the location of a resection plane that will provide a second femoral head offset, this being different to the first femoral head offset. Positioning of the resection guide on the femoral neck at the third discrete position will indicate to the surgeon the location of a resection plane that will provide a third femoral head offset, this being different from both the first and second femoral head offsets.
As the resection guide is moved more medially along the femoral neck axis there will be a concomitant reduction in the femoral head offset of the trial or definitive femoral head relative to the femoral shaft axis, if the surgeon resects the femoral neck along the resection plane indicated by the resection guide.
In an exemplary hip implant system, the first femoral head offset may be −2 mm, the second femoral head offset may be +5 mm, and the third femoral head offset may be +12 mm.
The indexing of the slidable connection between the template and the frame may comprise a plurality of calibration elements. Each calibration element corresponds to a distinct femoral head offset. The plurality of calibration elements may be arranged along the length of the arm or at least one arm of the pair of arms. The single head offset selector may be provided on the template. Positioning of the single femoral head offset selector relative to one of the plurality of calibration elements locates the resection guide at a discrete position along the femoral axis. This discrete position defines a resection plane that corresponds to the selected distinct femoral head offset.
It is envisaged that in some constructions of the surgical device, the plurality of calibration elements provided on the arm or at least on one arm of the pair of arms may comprise markings or indicia. These markings or indicia may be etched into or laser marked onto the surface of the arm. The single head offset selector provided on the template may also comprise a single marking or indicium. It is envisaged that this marking or indicia may be etched into, laser marked onto, mechanically engraved into, or moulded into the surface of the template.
Each arm has a longitudinal axis extending along its length. The markings or indicia on the arm or on at least one arm of the pair of arms may comprise a set of lines arranged along the length of the arm, with each line extending perpendicular to the longitudinal axis of the arm. The spacing between each line and the resection guide is calibrated so as to locate the resection guide along the femoral neck axis at a discrete position that indicates a resection plane corresponding to a distinct femoral head offset.
The single marking on the template may be a line.
The surgeon may slide the template relative to the frame until the single line on the template is aligned with a chosen line on the arm. This will locate the resection guide at a discrete position along the femoral neck axis that defines a resection plane corresponding to a distinct femoral head offset.
It is envisaged that in alternative constructions of the device, each of the plurality of calibration elements provided on the frame comprises a cut-out formed within the upper surface of the arm or at least one arm of the pair of arms. The plurality of cut-outs are spaced along the length of the arm.
In a specific construction of the device, each cut-out extends from an internally located edge of the or each arm. The cut-out is substantially semi-circular. Visually the upper surface of the channel is scalloped. The single projection on the template is substantially semi-circular.
The spacing between each cut-out and the resection guide is calibrated so as to locate the resection guide along the femoral neck axis at a discrete position that indicates a resection plane corresponding to a distinct femoral head offset.
In this construction, the single femoral head offset selector provided on the template comprises a single projection configured for alignment with any one of said plurality of cut-outs.
The surgeon may slide the template relative to the frame until the single semi-circular projection is aligned with a chosen cut-out. This will locate the resection guide at a discrete position along the femoral neck axis that defines a resection plane corresponding to a distinct femoral head offset.
It is also envisaged that in alternative constructions of the device, each of the plurality of calibration elements provided on the arm comprises an arm aperture formed within the upper surface of at least one arm. The plurality of arm apertures are spaced along the length of the arm.
The spacing between each arm aperture and the resection guide is calibrated so as to locate the resection guide along the femoral neck axis at a discrete position that indicates a resection plane corresponding to a distinct femoral head offset.
The single femoral head offset selector provided on the template comprises a single template aperture configured for alignment with any one of the plurality of arm apertures.
The surgeon may slide the template along the channel until the single template aperture is aligned with a chosen arm aperture. This will locate the resection guide at a discrete position along the femoral neck axis that defines a resection plane corresponding to a distinct femoral head offset.
It is envisaged that a locking element may be used to lock the template relative to the frame. This locking element may comprise a dowel. Accordingly, each one of the plurality of arm apertures, and the single template aperture are dimensioned to removably receive a dowel.
In order to reduce inventory of surgical instruments, advantageously the surgical device of the invention is designed to be used on the right and left hip, and for a posterior approach or an anterior approach. Accordingly a first plurality of calibration elements may be provided on an upper surface of the first arm, and a second plurality of calibration elements may be provided on a lower surface of the second arm. The first plurality of calibration elements may be duplicated by the second plurality of calibration elements. This means that the device can simply be flipped over, allowing the same device to be used regardless of which hip is being operated on, or which surgical approach is being used.
In an exemplary device, the first plurality of calibration elements may comprise a first calibration element that corresponds to a −2 mm femoral head offset, a second calibration element that corresponds to a +5 mm femoral head offset, and a third calibration element that corresponds to a +12 mm femoral head offset. Likewise, the second plurality of calibration elements may comprise a fourth calibration element that corresponds to a −2 mm femoral head offset, a fifth calibration element that corresponds to a +5 mm femoral calibration head offset, and a sixth calibration element that corresponds to a +12 mm femoral head offset.
In another construction, the first plurality of calibration elements and the second plurality of calibration elements are not duplicates.
In an exemplary device, the first plurality of calibration elements may correspond to a −2 mm, +5 mm, and +8 mm femoral head offset, and the second plurality of calibration elements may correspond to a +12 mm, +15 mm, and +17.5 mm femoral head offset. This means that when a surgeon flips the device over, s/he is presented with a different range of distinct femoral head offsets.
In a further alternative construction of the device, the indexable slidable connection between the template and the frame is achieved via a threaded connection, for example a thumbwheel connection. As a skilled artisan will understand, a thumbwheel is a control mechanism that consist of a partially exposed wheel that can be turned by moving the exposed edge with a thumb or finger.
It is envisaged that in any of the constructions of the femoral neck resection guide as described herein, a straight edge or a marked straight line may be provided on at least one of the template or the frame. This straight edge or marked straight line may be used to indicate the location of the femoral neck axis.
According to a second aspect of the invention there is provided a kit for use in orthopaedic surgery, comprising:
According to a third aspect of the invention there is provided a method of performing a controlled resection of a femoral neck comprising the steps of:
The step of positioning the resection guide along the femoral neck axis at a discrete resection plane may comprise the step of the surgeon aligning a single head offset selector provided the template with one of a plurality of calibration elements arranged along the length of the arm or at least one arm of the pair of arms, wherein each calibration element corresponds to distinct femoral head offset.
Although particular constructions of this disclosure have been described, it will be appreciated that many modifications/additions and/or substitutions may be made within the scope of the claims.
Constructions of this disclosure will be described hereinafter, by way of example only, with reference to the accompanying drawings in which like reference signs relate to like elements and in which:
Constructions of this disclosure are described in the following with reference to the accompanying drawings.
A first construction of the device 100 is shown in
The aperture 104 is substantially circular.
As shown in
The projecting rim or collar shown in
The frame includes a base portion 110 from which a pair of spaced apart arms 112a, 112b extend in a proximal direction. Each arm has a free proximal end 114a, 114b. The pair of arms and base portion form a generally U-shaped frame.
In the construction shown, a distally located edge of the arms 112a, 112b is defined by a straight edge 115a, 115b. Each straight edge 115a, 115b is angled in relation to the longitudinal axis of each arm. Each straight edge 115a, 115b can be used to indicated the location of the femoral axis.
A channel (not shown) is formed in each arm and is open along the internal edge 116a, 116b of each arm. The slot is dimensioned for slidable receipt of the template. In this construction, an opposing perimeter edge 117a, 117b of the template is slidably received within the slot.
The resection guide 108 extends distally from the base portion 110 of the frame. In this construction, the resection guide comprises a first foot 118a and a second foot 118b, with each foot being a mirror image of the other foot. Each foot has a first resection surface 120 that corresponds to a standard offset resection plane, and a second (more distally placed) resection surface 122 that corresponds to a high offset resection plane.
The slidable connection between the template and the frame is indexed. In this construction, the arm 112a includes a plurality of calibration elements spaced provided along its length. Each calibration element 124 is defined by a laser marking in the form of a horizontally oriented line. Each horizontal line extends from the internal edge 116a, 116b approximately half-way to the external edge 126a, 126b of each arm.
In the construction shown in
The calibration elements/secondary indicia shown on this first construction of the surgical device relate to an exemplary hip system, in which the most distally placed calibration element 124a corresponds to a −2 mm femoral head offset; the centrally placed calibration element 124b corresponds to a +5 mm femoral head offset, and the most proximally placed calibration element 124c corresponds to a +12 mm femoral head offset.
A single femoral head offset selector 128 is provided on the template. In this construction, the single femoral head offset selector 128 is defined by a laser marking in the form of a horizontal line, identical in design to the calibration elements 124a-c.
In use, when a surgeon has mounted the device 100 on a femoral head (not shown), s/he is able to slide the frame in a distal direction relative to the mounted template in order to place the resection guide 108 in one of three different positions along the femoral neck axis (not shown). The positioning of the resection guide 108 depends on which line of the plurality of lines 124a-c (i.e., the calibration elements) the surgeon chooses to align the single line 126 (i.e., the femoral head offset selector) with.
In the construction shown in
It is envisaged that the calibration elements 124a-c are duplicated on the underside of arm 112b. These are shown as ghost dotted lines in
Turning to
In this construction, each of the plurality of calibration elements 224 is defined by a semi-circular cut-out formed within the upper surface of each arm 212a, 212b. Each cut-out extends from an internally located edge 216a, 216b of the arm. Visually the upper surface of the channel is scalloped.
In the construction shown in
The calibration elements/secondary indicia shown on this second construction of the surgical device relate to an exemplary hip system, in which the most distally placed calibration element 224a corresponds to a −2 mm femoral head offset; the centrally placed calibration element 224b corresponds to a +5 mm femoral head offset, and the most proximally placed calibration element 224c corresponds to a +12 mm femoral head offset.
In this construction, the single femoral head offset selector 228 provided on the template is defined by a single semi-circular projection extending from opposing perimeters edges 217a, 217b of the template.
In use, when a surgeon has mounted the device 200 on a femoral head (not shown), s/he is able to slide the frame in a distal direction relative to the mounted template in order to place the resection guide 208 in one of three different positions along the femoral neck axis (not shown). The positioning of the resection guide 208 depends on which of the semi-circular recesses 224a-c (i.e., the calibration elements) the surgeon chooses to align the single semi-circular projection 228 (i.e., the femoral head offset selector) with.
In the construction shown in
Turning to
In this construction, each of the plurality of calibration elements 324a-c is defined by a circular aperture formed within the upper surface of each arm 312a, 312b.
The calibration elements 324a-c provided on this third construction of the surgical device relate to an exemplary hip system, in which the most distally placed calibration element 324a corresponds to a −2 mm femoral head offset; the centrally placed calibration element 324b corresponds to a +5 mm femoral head offset, and the most proximally placed calibration element 324c corresponds to a +12 mm femoral head offset.
In this construction, the single femoral head offset selector 328 provided on the template is defined by a single circular aperture.
In use, when a surgeon has mounted the device 300 on a femoral head (not shown), s/he is able to slide the frame in a distal direction relative to the mounted template in order to place the resection guide 308 in one of three different positions along the femoral neck axis (not shown). The positioning of the resection guide 308 depends on which of the circular apertures 324a-c (i.e., the calibration elements) the surgeon chooses to align the single aperture 328 (i.e., the femoral head offset selector) with.
In the construction shown in
Turning now to
Finally, in
In an exemplary hip system, the stem size ranges from size 1 to size 12, that can be subdivided into four groups:
The surgical device 500 template can be used in four different orientations, as shown in
Positioning the semi-circular protrusion 528 (i.e., the single femoral head offset selector) in relation to one of the semi-circular cut outs 524a-c (i.e., the plurality of calibration elements) will position the resection guide 508 in a discrete resection plane along the femoral neck axis for a combination of a selected stem size and a selected femoral head offset. The asymmetric positioning of the semi-circular protrusions working with the asymmetric position of the semi-circular cut out allows for the ascending size and offset range to be accommodated.
As shown in
By rotating the template about 180°, as shown in
If the template is flipped over, as shown in
By rotating the template about 180°, as shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| 1905459.2 | Apr 2019 | GB | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2020/060789 | 4/16/2020 | WO | 00 |
