Patent Application
20200214684
THIS INVENTION relates to a device for use in knee surgery. In particular, the invention is directed to a spacer device for use in knee surgery on a subject and, in particular, total knee replacement that facilitates optimal soft tissue balancing via measurement of bone displacement and one or more forces exerted thereon.
Total knee replacement surgery is an increasingly common and expensive procedure. A successful outcome largely rests on the ability to match the flexion and extension gaps of the knee joint. True balance is reflected both by appropriate force being applied to the medial and lateral aspects of the knee joint as well as the excursion of the soft tissues on either side of the knee joint. These concepts are important if excessive excursion of the soft tissues is possible after knee replacement surgery. To this end, forces that may have been evenly distributed in a non-dynamic setting, may then cause uneven forces to be applied to the knee replacement prosthesis during the dynamic portion of movement. Similarly, if there is excessive lack of excursion (i.e., tightness) of the soft tissues then during dynamic movement the forces may be concentrated on one side of the joint. Alternatively, the forces within the knee joint may be equal or minimally different, but be too low or high.
Means of achieving a balanced knee in total knee replacement surgery currently exist, such as with the use of robotic surgical systems, computer assisted surgery or force registering sensors. Typically, these systems are complex and expensive. Furthermore, such systems generally achieve one but not both of: (a) measuring the total width of the flexion and extension gaps on both the medial and lateral sides of the knee; and (b) measuring the force that is present on the medial and lateral sides of the knee joint when the soft tissues are placed under tension. Accordingly, there remains a need for a simple, cheap and reproducible means for achieving both of these goals in total knee replacement surgery. As noted above, this is important for achieving an optimal patient outcome after a total knee replacement, as well as important generally to the healthcare system by providing a relatively cheap and cost efficient means of conducting surgery. As the cost of provision of healthcare rises more complex and expensive systems may not provide the necessary surgical outcomes in a cost-efficient manner.
The present invention is broadly directed to a spacer device for assisting a surgeon during knee surgery and, in particular, TKR, in a patient. The spacer device is preferably inexpensive and readily made. The spacer device may be used to not only measure the width of medial and/or lateral flexion and/or extension gaps during knee replacement surgery, but also assess medial and/or lateral forces in flexion and/or extension. This may facilitate appropriate tensioning of the soft tissue envelope of the knee joint. The invention is further directed to surgical system including said spacer device and methods of using the spacer device in knee surgery.
In a first aspect, the invention is directed to a spacer device for assisting a surgeon during knee surgery on a patient comprising:
In one embodiment, the outer surface of the lateral member, one or both of the side members, one or both of the first pair of lateral projections and/or the one or more spacer elements further comprise a force sensor. In an alternative embodiment, axial slidable movement of the support portion relative to the housing further defines an inner space between the inner surface of the lateral member and the second end portion for receiving a force sensor therein.
In one embodiment, the spacer device further comprises the one or more spacer elements and/or the force sensor. In an alternative embodiment, the force sensor is not disposed in or on or integral with the spacer device.
In particular embodiments, the force sensor is or comprises an electronic force sensor. Suitably, the electronic force sensor comprises a sensor element selected from the group consisting of a thin film sensor element, a thick film sensor element, a piezoelectric sensor element, a strain gauge sensor element and any combination thereof. Preferably, the sensor element is or comprises a thin film sensor element.
In particular embodiments, the electronic force sensor comprises an outer plate for contacting the resected distal femoral surface, the posterior femoral surface and/or the resected proximal tibial surface.
In one embodiment, the electronic force sensor comprises one or more transfer members for transferring forces imparted thereon to the sensor element associated therewith.
In one embodiment, the electronic force sensor further comprises a support member having one or more apertures for receiving the sensor element therein.
In one embodiment, the electronic force sensor further comprises a base member for receiving the transfer members, the support member, and/or the outer plate thereon. In one preferred embodiment, the base member is disposed with a channel in the outer surface of the lateral member.
Suitably, the electronic force sensor includes a display adapted for displaying a force measured thereby.
In one embodiment, the electronic force sensor is configured to measure first and second forces exerted on respective lateral and medial sides of the spacer device. In another embodiment, the electronic force sensor is configured to measure third and fourth forces exerted on respective anterior and posterior sides of the spacer device.
In certain embodiments, the force sensor is a mechanical or non-electronic force sensor.
Suitably, the posterior femoral surface is or comprises a resected posterior femoral surface.
In one embodiment, the spacer device further includes a guide member for assessing a degree of further resection of the resected distal femoral surface, the posterior femoral surface and/or the resected proximal tibial surface required. The guide member is suitably for facilitating placement of a resection member on a resected femur and/or a resected tibia for further resection of the resected distal femoral surface, the posterior femoral surface and/or the resected proximal tibial surface. Preferably, the guide member comprises an engagement member for reversibly engaging the spacer device, a guide portion and an extendible arm for connecting the engagement member and the guide portion.
Suitably, the spacer device of the present aspect is for use in the method of the third aspect.
Suitably, the housing comprises first and second portions slidably connected to each other to allow for axial and/or sagittal movement of the first portion relative to the second portion.
In a second aspect, the invention provides a surgical system for assisting a surgeon during knee surgery on a patient comprising:
In one embodiment, the force sensor is disposed in or on the outer surface of the lateral member, one or both of the side members, one or both of the first pair of lateral projections and/or the one or more spacer elements. In an alternative embodiment, axial slidable movement of the support portion relative to the housing further defines an inner space between the inner surface of the lateral member and the second end portion for receiving the force sensor therein.
In particular embodiments, the force sensor is not disposed in or on or integral with the spacer device.
In certain embodiments, the force sensor is a mechanical or non-electronic force sensor.
In alternative embodiments, the force sensor is or comprises an electronic force sensor. Suitably, the electronic force sensor comprises a sensor element selected from the group consisting of a thin film sensor element, a thick film sensor element, a piezoelectric sensor element, a strain gauge sensor element and any combination thereof. Preferably, the sensor element is or comprises a thin film sensor element.
In particular embodiments, the electronic force sensor comprises an outer plate for contacting the resected distal femoral surface, the posterior femoral surface and/or the resected proximal tibial surface.
In one embodiment, the electronic force sensor comprises one or more transfer members for transferring forces imparted thereon to the sensor element associated therewith.
In one embodiment, the electronic force sensor further comprises a support member having one or more apertures for receiving the sensor element therein.
In one embodiment, the electronic force sensor further comprises a base member for receiving the transfer members, the support member, and/or the outer plate thereon. In one preferred embodiment, the base member is disposed with a channel in the outer surface of the lateral member.
Suitably, the electronic force sensor includes a display adapted for displaying a force measured thereby.
In one embodiment, the electronic force sensor is configured to measure first and second forces exerted on respective lateral and medial sides of the spacer device. In another embodiment, the electronic force sensor is configured to measure third and fourth forces exerted on respective anterior and posterior sides of the spacer device.
In certain embodiments, the force sensor is a mechanical or non-electronic force sensor.
In one embodiment, the force sensor includes one or more inflatable elements.
Suitably, the force sensor includes a display adapted for displaying the force measured by the force sensor.
With respect to the first and second aspects, the second end suitably comprises a second pair of lateral projections.
Referring to the first and second aspects, each of the side walls suitably comprises a medial projection at a distal end thereof for contacting the one or more spacer elements.
Suitably, for the invention of the first and second aspects, the posterior femoral surface is or comprises a resected posterior femoral surface.
In one embodiment, the surgical system further includes a guide member for assessing a degree of further resection of the resected distal femoral surface, the posterior femoral surface and/or the resected proximal tibial surface required. Suitably, the guide member is for facilitating placement of a resection member on a resected femur and/or a resected tibia for further resection of the resected distal femoral surface, the posterior femoral surface and/or the resected proximal tibial surface. Preferably, the guide member comprises an engagement member for reversibly engaging the spacer device, a guide portion and an extendible arm for connecting the engagement member and the guide portion.
Suitably, the system of the present aspect is for use in the method of the third aspect.
Suitably, the spacer device of the present aspect is that of the first aspect.
In a third aspect, the invention provides a method for assisting a surgeon during knee surgery on a patient including the steps of:
In one embodiment, the step of positioning a spacer device comprises positioning the spacer device adjacent:
Suitably, the posterior femoral surface is or comprises a resected posterior femoral surface.
In particular embodiments, the present method further includes the step of measuring an extension gap and/or a flexion gap between the resected femur and the resected tibia.
In one embodiment, one or both of the side members, one or both of the first pair of lateral projections and/or the one or more spacer elements further comprise a force sensor. With respect to this embodiment, the method suitably further includes the step of using the force sensor to measure a force exerted by the resected femur and the resected tibia on the spacer device.
In an alternative embodiment, axial slidable movement of the housing further defines an inner space between the inner surface of the lateral member and the second end portion for receiving a force sensor therein. With respect to this embodiment, the method of the present aspect suitably further includes the steps of:
Preferably, the force sensor is used to measure first and second forces exerted on respective lateral and medial sides of the spacer device.
Suitably, the method of the present aspect further includes the step of using:
In one embodiment, the method of the present aspect further includes the step of using a guide member connected to the spacer device to: (a) assess a degree of further resection of the resected distal femoral surface, the posterior femoral surface and/or the resected proximal tibial surface required; and/or (b) facilitate placement of a resection member on the resected femur and/or the resected tibia for further resection of the resected distal femoral surface, the posterior femoral surface and/or the resected proximal tibial surface. Preferably, the guide member comprises an engagement member for reversibly engaging the spacer device, a guide portion and an extendible arm for connecting the engagement member and the guide portion.
Suitably, the spacer device is that of the first aspect.
It will be appreciated that the indefinite articles “a” and “an” are not to be read as singular indefinite articles or as otherwise excluding more than one or more than a single subject to which the indefinite article refers.
As used herein, unless the context requires otherwise, the words “comprise”, “comprises” and “comprising” will be understood to mean the inclusion of a stated integer or group of integers but not the exclusion of any other non-stated integer or group of integers.
In order that the present invention may be readily understood and put into practical effect, reference will now be made to the accompanying illustrations, wherein like reference numerals are used to refer to like elements.
The present invention relates to a spacer device for use during surgery and, in particular, TKR/TKA, for determining appropriate soft tissue balance of the knee joint in extension and/or flexion. While the spacer device described herein is particularly suited for use in TKR/TKA, the present invention has general applicability to all types of joints (e.g., elbows, shoulders, wrists and fingers) and replacement surgery thereof that requires accurate gap balancing, joint alignment and/or soft tissue balancing.
Appropriate soft tissue balancing requires placing the soft tissues surrounding and/or interconnecting the bones of the knee at an approximately equal or similar tension relative to one another when the femur and its corresponding tibia are placed in a desired alignment as determined by the surgeon. Preferably, this tension is approximately equal or similar to the physiological tension of these soft tissues in the native knee at rest. Non-limiting examples of the soft tissues surrounding and/or interconnecting the bones of the knee include the medial and lateral collateral ligaments, the anterior and posterior cruciate ligaments, the posteromedial and posterolateral ligamentous structures and the posterior capsule.
While the principles described herein are based on methods of providing surgical devices for humans, this invention may also be extended to other mammals such as livestock (e.g. cattle, sheep), performance animals (e.g. racehorses) and domestic pets (e.g. dogs, cats), although without limitation thereto.
A spacer device 100 according to particular embodiments is adapted to be used during TKA for precise realignment and soft tissue tensioning of the knee joint 700 in flexion and/or extension by providing appropriate medial and/or lateral spacing between the respective resected surfaces 802, 902 of the distal femur 801 and the proximal tibia 901. Thus, the spacer device 100 is designed to result in appropriate forces being applied across the knee joint 700 after placement of an appropriately sized knee replacement prosthesis therein. Furthermore, in particular embodiments, the spacer device 100 is adapted to ensure that there is adequate space for the particular patient's replacement implant, as well as that the resection planes of the proximal tibia 901 and distal femur 801 are substantially parallel in the coronal and sagittal planes.
As noted above, various embodiments of the present invention provide spacer devices for assisting a surgeon during TKA. Referring to the figures and, in particular,
In the embodiment provided, the housing 110 includes a substantially planar upper wall 111 having an upper surface 111a and a lower surface 111b. As can be observed in
As shown in
It will be appreciated by the skilled artisan, however, that the spacer device 100 may be utilised without such movement or distraction of the first portion 110a relative to the second portion 110b. Accordingly, in alternative embodiments, the housing 110 of the spacer device 100 is of a single, unitary structure.
The inner support portion 120 has a first end portion 121 and a second end portion 122 connected by a central portion 123. The second end portion 122 and the central portion 123 are, at least partially, disposed between the side walls 112a-b of the housing 110 and are maintained in this position by virtue of the second end portion 122 having a second pair of radially extending tabs 125a-b, which may contact their respective and opposing inwardly projecting tab 113a-b of the housing 110 upon distraction of the spacer device 100 (i.e., axial movement of the inner support portion 120 relative to the housing 110). The first end portion 121 of the inner support portion 120 also includes a first pair of radially extending tabs 124a-b. As can be observed from
It will be appreciated that the spacer device 100 will preferably also function in the opposite orientation than that presented in
Suitably, the spacer device 100 described herein is for use when the knee joint 700 is in full extension (i.e., approximately 180 degrees). The skilled artisan, however, would appreciate that this may not be possible or feasible in all patients, owing, for example, to the presence of pre-existing disease or deformities of the limb. By way of example, a patient with a flexion deformity or contracture of the knee may be physically unable to fully straighten or extend the knee. Accordingly, in certain embodiments, the spacer device 100 provided herein is used when the knee joint 700 is not fully extended.
As used herein, the terms “approximately” and “about” refer to tolerances or variances associated with numerical values recited herein. The extent of such tolerances and variances are well understood by persons skilled in the art. Typically, such tolerances and variances do not compromise the structure, function and/or implementation of the devices and methods described herein.
Suitably, prior to insertion of the spacer device 100, the knee joint 700 is exposed and the distal femur 801 and the proximal tibia 901 are resected to thereby establish an appropriate extension gap 400 of the knee joint 700, as shown in
The collapsed two-part spacer device 100 is then inserted into the extension gap 400, as illustrated in
In a particular embodiment, the height of the spacer device 100 can be adjusted, such as by reversibly attaching or engaging a foot portion (not shown), such as via a mortise and tenon joint or other engagement member as are known in the art, with the first end 121 of the inner support portion 120. By virtue of this arrangement, the height of the spacer device 100 can be approximated to accommodate the extension gap 400 and/or flexion gap regardless of their dimensions and then this height can be fine tuned with the spacer elements 201, 202 as required.
In certain embodiments, the spacer device 100 has a width dimension of about 50 mm to about 80 mm and a thickness or depth dimension of about 50 mm to about 80 mm. Therefore, the spacer device 100 may be at least as large as the leading edges of the resected femoral and tibial surfaces 802, 902. For instance, the spacer device 100 may be about 20 mm to about 50 mm in depth and width in order to substantially conform to the resected leading edges of the resected femoral and tibial surfaces 802, 902. As will be readily understood by the skilled artisan, the dimensions for the spacer device 100 described herein will depend to some degree on the size of the knee joint 700 to which the device 100 is to be applied.
It is further envisaged that particular embodiments of the spacer device 100 may be configured or of dimensions for use in unicompartmental knee replacement (i.e., on the lateral or medial side 701, 702 of the knee joint 700). Additionally, embodiments of the spacer device 100 may be adapted for use in bicruciate retaining total knee replacement surgery. In such an embodiment, the spacer device 100 would need a posterior channel adapted to receive the cruciate ligament that have been left in-situ therein and the medial and lateral sides of the spacer device 100 would be connected by an anterior bridge. Alternatively, two separate spacer devices 100 may be utilised in the medial and lateral sides 701, 702 of the knee joint 700.
During use, the spacer device 100 is typically positioned between the distal femur 801 and the proximal tibia 901 when the leg is fully extended (see
Once appropriately positioned within the knee joint 700, the spacer device 100 can now be extended or distracted along its longitudinal axis a. By way of example, the spacer device 100 can be distracted or extended by the action of one or more laminar spreaders inserted between the upper wall 111 of the housing 110 and the second end portion 122 of the inner support portion 120. An anterior face 125 of the inner support portion 120 may include gradations, such as millimetre gradations or degrees of rotation gradations, so as to indicate to the surgeon the distance of distraction of the housing 110 relative to the inner support portion 120 both laterally and medially thereto. In this regard, it will be appreciated that an anterior surface of one or both of the side walls 112a, 112b may also or alternatively include such gradations to assist the surgeon in this manner.
As can be observed in
In addition or alternatively to the above, it will be appreciated that one or both of the spacer elements 201, 202 could be inserted into the inner space 160 so as to maintain the spacer device 100 in the distracted position. Such an arrangement may be used in embodiments in which a force sensor, and more particularly, an electronic force sensor, is disposed on or in or is integral with, for example, the upper surface 111a of the upper wall 111 of the housing 110, an outer or lateral surface of one or both of the side walls 112a-b and/or an outer or lower surface of the first end 121 of the inner support portion 120.
In one particular embodiment not shown herein, the spacer elements 201, 202 comprise one or more rounded portions that are configured to internally engage or abut corresponding concave surfaces in the radially extending tabs 124a-b of the inner support portion 120 and/or the inwardly projecting tabs 113a-b of the housing 110. The opposite arrangement is also envisaged in which the spaced elements 201, 202 include one or more concave surfaces and the the radially extending tabs 124a-b and/or the inwardly projecting tabs 113a-b comprise the corresponding rounded portions for engagement therewith. Such an arrangement facilitates at least partial rotation of the inner support portion 120 relative to the housing 110 if required.
Preferably, the spacer elements 201, 202 provided herein for insertion into the first space 140 and/or the second space 150, as defined by the respective inwardly projecting tabs 113a-b of the side walls 112a-b and the first pair of radially extending tabs 124a-b, may include a range of dimensions so as to provide a surgeon with choice of spacer elements 201 in their attempts to at least partly facilitate return of the knee joint to an appropriate alignment and/or an appropriate soft tissue balance. By way of example, the spacer element 201, 202 of the spacer device 100 may come in a range of sizes, such as about 4 mm to about 20 mm and typically increase in one millimetre increments (e.g., about 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 mm and any range therein). The surgeon will generally continue inserting increasing sizes of the spacer elements 201, 202 into the first and second spaces 140, 150 until the soft tissue on the medial and lateral aspects of the extension gap 400 and flexion gap (not shown) have reached an optimal and preferably substantially matching or equivalent tension. In this regard, a different sized first spacer element 201 may be required for balancing the lateral side 701 of the knee joint 700 versus the second spacer element 202 used for the medial side 702 thereof. This may depend upon the individual's preoperative knee anatomy, which may be determined by, for example, magnetic resonance imaging (MRI) or computed tomography (CT), and the presence of any anatomical deformities and/or defects, such as varus or valgus.
By way of example, in
Additionally, the spacer device 100 facilitates measurement of not only maximal displacement of the knee joint 700 and one or more forces at this point, but also the forces present at submaximal displacement of the knee joint 700. By way of example, maximal displacement of the knee joint 700 may indicate via the spacer elements 201, 202 that the medial side 702 will accommodate an 11 mm polyethylene component of the knee joint prosthesis, whilst the lateral side 701 will conversely accommodate a 13 mm polyethylene component. The spacer elements 201, 202 of dimensions that correspond to the 11 mm polyethylene component can then be inserted into the first and second spaces 140, 150 and the forces associated with this degree of displacement or distraction of the knee joint 700 can be measured. Accordingly, it will then be known what the maximal or peak force/s are and what particular forces will be associated with a specific sized polyethylene insert or indeed the knee joint prosthesis itself. Such measurements will allow surgical determination of whether or not the current resections of the proximal tibia 901 and/or distal femur 801 require adjustment so as to achieve substantially parallel resection planes thereof in the coronal and sagittal planes as well as substantially equivalent soft tissue balancing or tensioning across the knee joint 700.
Accordingly, following placement of the spacer elements 201, 202 to achieve an appropriate soft tissue balance (i.e., substantially equalise medial and lateral forces in the knee joint), the surgeon is then able to assess the extension gap 400 across both the medial and lateral aspects 701, 702 of the knee joint 700. Accordingly, this allows for both a minimum appropriate extension gap 400 to be provided and the determination of any discrepancy in the extension gap 400 between the medial and lateral aspects 701, 702 of the knee joint 700. This may also allow for the surgeon to further assess any tilting of the upper surface 111a of the upper wall 111 and/or the first end 121 of the inner support portion 120 relative to the resected distal femoral surface 802 or resected proximal tibial surface 902 they are contacting or abutting in situ as well as any tilting of the housing 110 and/or the inner support portion 120 in relation to the spacer elements 201, 202. It will be appreciated that such an assessment provides an indication of whether an appropriately matched anteroposterior slope of the resected proximal tibial surface 902 has been achieved.
As shown in
In other embodiments, the force sensor 300 may include a block member with one or more force sensing elements or pads thereon together with a force readout device or display, such as a pressure gauge or a force gauge. The force sensing elements can be, for example, any suitable sensing element capable of detecting and acquiring data indicative of forces applied by each of the resected femur 800 and tibia 900 on the spacer device 100. Suitable force sensing elements include, for example, a piezoelectric sensor, a strain gauge, a transducer, a load cell, or the like, as are known in the art. In one particular embodiment, the one or more force sensing elements may include one or more inflatable elements in fluid communication with a syringe or the like so as to be inflated with air or saline upon insertion into the inner space 160. It will be apparent that such force sensors 300 may capable or designed for multiple uses. The force sensor 300 can include an array of force sensing elements which may, for example, be arranged in a grid or other suitable geometrical arrangement. Preferably, the force sensor 300 is arranged or configured to measure a first force on a lateral side 701 of the knee joint 700 and a second force on a medial side 702 of the knee joint 700.
Once the force sensor 300 has been inserted into the inner space 160, preferably in a manner so as to assess soft tissue tension in both the medial and lateral sides 701, 702 of the knee joint 700, the spacer elements 201, 202 are removed and the amount of force exerted on the force sensor 300 can be assessed. Alternatively, and with particular respect to the aforementioned force sensor 300 comprising inflatable elements, sufficient pressure or force may be generated within the inner space 160 by the force sensor 300, such as by inflation of the inflatable elements, to the threshold that just allows for removal of the spacer elements 201, 202 from their respective first and second spaces 140, 150 thereby providing an indication of the force on the medial and lateral sides 701, 702 of the knee joint 700. Regardless of the method chosen, the spacer device 100 allows for a thorough assessment of the extension gap 400 in terms of both its actual dimensions as well as the soft tissue tension on either side thereof (i.e., both medial and lateral sides 701, 702 of the knee joint 700) at a distracted position of the spacer device 100 that the surgeon has determined to be optimal in this regard.
After assessing the extension gap 400, as hereinbefore described and illustrated in
In an alternative embodiment to that described above, the force sensor 300 is, for example, an electronic force sensor disposed in or on or connected to: (a) an upper and/or lower surface of the one or both of the first pair of radially extending tabs 124a-b of the inner support portion 120; (b) a lower surface of one or both of the inwardly projecting tabs 113a-b of the side walls 112a-b of the housing 110; (c) the upper surface 111a of the upper wall 111 of the housing 110; (d) an outer or lateral surface of one or both of the side walls 112a-b, (e) an outer or lower surface of the first end 121 of the inner support portion 120; and/or (f) one or more of the spacer elements 201, 202. With respect to this embodiment, there is no longer the need to insert the force sensor 300 into the inner space 160. Instead, force measurements can be made directly after insertion of the spacer elements 201, 202 into the first and/or second spaces 140, 150. Further to this, it is envisaged that the force sensor 300 could be disposed on or in any surface of the spacer device 100, including lateral and medial surfaces thereof. By virtue of this arrangement, the force sensor 300 can be capable of measuring not only those axial or longitudinal forces exerted on, for example, upper and/or lower surfaces of the housing 110 and the inner support portion 120 during distraction of the spacer device 100, but also pressure from the soft tissue positioned immediately around or adjacent the spacer device 100, such as the collateral ligaments and cruciate ligaments.
With respect to the above, force data measured or acquired by the force sensor 300 may be transmitted by any wired means and/or wirelessly to an external or remotely located computer device or display screen. In typical embodiments, the force data can be transmitted by way of a conventional data transmission protocol as are known in the art, such as BlueTooth or the like. In an alternative embodiment, the force data measured or acquired by the force sensor 300 is transmitted wired and/or wirelessly to display screen disposed in or on the spacer device 100 itself.
Prior to insertion of the spacer device 100 into the flexed knee joint, bony resections, such as of the posterior femoral condyles, may be undertaken as per standard surgical techniques known in the art. The spacer device 100 is then inserted into the flexed knee joint, so as to be positioned adjacent the resected proximal tibial surface 902 and a resected posterior femoral surface (not shown). Distraction of the spacer device 100 is then performed as per the method described for the extended knee joint 700 above, so as to allow for assessment of the flexion gap in terms of both dimensions and soft tissue tension on the medial and lateral aspects thereof. Surgery can then continue with adjustments occurring as necessary for any discrepancy of significance that is noted in terms of a mismatch between: (a) the respective dimensions of the extension and flexion gaps; (b) soft tissue tension between the medial and lateral sides of the joint in either flexion or extension.
In an alternative embodiment for assessing the flexion gap, the spacer device 100 is inserted into the flexed knee joint prior to resection of the posterior femoral condyles. Accordingly, the spacer device 100 is preferably of a thickness or depth dimension (e.g., about 8 mm to about 10 mm) so as to extend under the posterior condyles of the femur 800. Alternatively, the spacer device 100 may include paddle-like projections that extend under the posterior condyles. Longer spacer elements 201, 202 may then be used to provide tension between the tibia 900 and the posterior condyles of the femur 800 so as to facilitate distraction of the femur 800 relative to the tibia 900. Additionally, a smaller anterior portion (not shown) contacting the anterior face of the femur 800 may further be distracted by the appropriate residual amount to match the extension gap 400.
This would allow for distraction of the knee joint 700 by the spacer device 100 and assessment of soft tissue tension prior to resection of the posterior femoral condyles. To this end, the degree of distraction of the spacer device 100 in the flexed knee would be preferably matched or equivalent to that previously determined for the corresponding extension gap 400. When such a distracted position has been attained by the spacer device 100, the proposed posterior femoral resection plane may be marked and the force sensor 300 is again inserted into the inner space 160 between the housing 110 and the inner support portion 120 to assess whether the proposed resection would produce optimal flexion forces both medially and laterally as well as substantially match those already measured for the extension gap 400.
In the event that the spacer device 100 indicates that the flexion gap and/or the extension gap 400 are not substantially balanced (i.e., when one aspect or side of the extension or flexion gap is narrower than the other and/or when one of the extension or flexion gap is of smaller dimensions than its corresponding flexion or extension gap), a resection guide member 130 may then be utilised to correct for any mismatch therebetween. In this regard, when spacer elements 201, 202 of differing dimensions are inserted into the first and second spaces 140, 150 respectively, the housing 110 is not parallel or square relative to the inner support portion 120.
In the embodiment provided in
The resection guide member 130 is then oriented such that an adjustable guide 134 at a distal end thereof is preferenced or adjacent to the particular bone (i.e., femur or tibia) that requires correction. For example, if the extension gap 400 is considered too narrow or tight, the resection guide member 130 would be placed on the tibial side of the spacer device 100 so as to be directed towards or adjacent the distal femur 801. The guide 133 of the resection guide member 130 further includes a guide aperture 134, which can then be set or adjusted so as to overlie a level of the extension gap 400 or flexion gap (not shown) that is considered to be of optimal dimensions by the surgeon.
In the embodiment provided in
By way of example, if the medial side of the extension gap 400 and/or the flexion gap was narrower and/or tighter (i.e., has a greater soft tissue tension and hence more force as measured by the spacer device 100) than the lateral side, more bone would be removed or resected from the medial side than the lateral side. Preferably, the amount of bone that is removed is such so as to produce extension and flexion gaps of substantially equal dimensions. In this regard, it may be possible to accept a small degree of mismatch between the flexion and extension gaps. A standard tibial or femoral resection member may then be suitably placed or slid under the guide aperture 134 of the guide 133 of the resection guide member 130 and pinned into place to the femur 800 or tibia 900 so as to facilitate recutting of the distal femoral resection surface 802, the posterior femoral resection surface or the proximal tibial resection surface 902. To this end, an osteotome blade or similar may be used to hold the tibial or femoral resection member in position while it is pinned in place. The spacer device 100 and the resection guide member 300 can then be removed so as to allow for resection of the femur 800 or tibia 900 to proceed in the standard fashion. This mechanism of balancing the flexion and/or extension gaps typically allows for any variation in bone resection or correction as required rather than the typical +2;+4 type resection fine-tuning that is available with particular systems known in the art. The extension and flexion gaps and soft tissue balance of the patient's knee joint 700 may then be reassessed by the spacer device 100 to confirm correction of any previous imbalance thereof.
Accordingly, following use of the spacer device 100 the distal femoral resection plane is preferably substantially parallel to the proximal tibial resection plane when the knee joint 700 is in extension, such that an extension gap 400 from the tibia 900 to the femur 800 is substantially rectangular after performing distal and proximal resections. Further, with respect to the knee joint 700 in flexion, the proximal tibial resection plane is preferably substantially parallel to the posterior femoral resection plane, such that a flexion gap from the tibia 900 to the femur 800 is substantially rectangular after performing proximal and posterior resections. Additionally, the extension gap is preferably of substantially equal dimensions to that of the flexion gap.
It would be appreciated that the spacer device 100 may further assist in joint line restoration in a subject in the knee joint 700 in both flexion and extension. By way of example, this may be achieved by noting the meniscal bodies and/or remnants thereof and whether they approximately correspond to a central portion of the spacer device 100 once it is in a distracted position.
A further embodiment of a spacer device 500 is provided in
The housing 510 is divided into approximately equally dimensioned first and second portions 510a-b that comprise a respective portion of a substantially planar upper wall 511′, 511″, one of a side wall 512a-b and one of first and second central axial projections 517a-b that each extend axially and distally from respective end portions of the upper walls 511′, 511″. As illustrated in
As each of the first and second portions 510a-b are distracted relative to the other, stability of the housing 510 is maintained, at least in part, by the respective side walls of the first and second central axial projections 517a-b abutting each other as well as the respective opposed side walls of the central channel 528.
By virtue of this arrangement, the first and second portions 510a-b of the housing 510 are configured to allow for independent axial and/or sagittal distraction or movement of the first portion 510a relative to the second portion 510b so as to allow for the generation of a lateral inner space (not shown) and a medial inner space (not shown).
The upper wall 511′, 511″ of the housing 510 has first and second upper surfaces 511a′, 511a″ and first and second lower surfaces 511b′, 511b″. As can be observed in
As shown in
In alternative embodiments, it will be understood that different sensor elements 590a-d as are known in the art, such as thick-film sensors and piezoresistive sensors, may be included in the present invention. In one particular embodiment, one or both of the support plates 572a-b comprises a thin metal plate having one or a plurality of strain gauges disposed thereon.
The upper plates 571a-b and the support plates 572a-b each include laterally and medially positioned and downwardly projecting mating elements or projections 578a-f, 579a-f that are adapted to be matingly received within corresponding mating channels 580a-f, 581a-f provided in upper portions of both medial and lateral surfaces of the side wall 512a-b. These mating channels 580a-f, 581a-f and their corresponding mating projections 578a-f, 579a-f function to stabilize and align the aforementioned components of the force sensor units 570a-b during use.
As noted earlier, the housing 510 comprises a pair of directly opposed side walls 512a-b. Each of the side walls 512a-b extends axially and distally from a respective end portion of the lower surfaces 511b′, 511b″ of the upper wall 511′, 511″ so as to form a pair of channels 514a-b in which to receive the inner support portion 520. The side walls 512a-b further include a respective inwardly projecting tab 513a-b at a distal end thereof that assist in maintaining the inner support portion 520 disposed within the housing 510.
As illustrated in
Once appropriately positioned within the knee joint 700, the first and second portions 510a-b of the housing 510 of the spacer device 500 can now be extended or distracted along its longitudinal axis a relative to the inner support portion 520. Similar to that described for the previous embodiment, axial movement of the first and second portions 510a-b relative to the inner support portion 520 results in the generation of the lateral and medial inner spaces (not shown) that are defined by the respective lower surfaces 511b′, 511b″ of the upper wall 511′, 511″, the side walls 512a-b and the central axial projections 517a-b of the housing 510 and the second end portion 522 of the inner support portion 520. Additionally, such axial movement results in the formation of a first space (not shown) and a second space (not shown), each located between or defined by their respective inwardly projecting tab 513a-b of the side walls 512a-b and the opposing first pair of radially extending tabs 524a-b. Each of the first and second spaces (not shown) and/or the lateral and medial inner spaces (not shown) may then be utilised for receiving a suitably dimensioned spacer element (not shown) so as to maintain the spacer device 500 in the desired distracted position and allow for measurement of soft tissue tension by one or both of the electronic force sensor units 570a-b as well as assessment of dimensions of the extension and/or flexion gap as previously described for the spacer device 100.
As illustrated in
Again, it is envisaged that one or more further electronic force sensor units (not shown) could be disposed on or in one or more additional surfaces of the spacer device 500. By way of example, a further electronic force sensor unit (not shown) may be disposed within the hemi-cylindrical channel 595 or a posterior surface of, for example, the inner support portion 520, so as to assess soft tissue tension in respect of the posterior cruciate ligament. Additionally, one or more further electronic force sensor units (not shown) could be disposed in or on one or more of the lateral surfaces of the spacer device 500, such as the side walls 512a-b, in order to facilitate assessment of soft tissue tension in relation to the collateral ligaments adjacent thereto.
An alternative embodiment of a spacer device 1000 is provided in
Similar to that for the spacer device 100, 500 previously described, the spacer device 1000 is for assisting a surgeon during knee replacement surgery, which includes a T-shaped open-sided housing 1010 that defines a longitudinal axis a and an inner support portion 1020. The inner support portion 1020 has a first end portion 1021 and a second end portion 1022 connected by a central portion 1023. The housing 1010 includes a central axial projection 1017a-b that extends axially and distally from a substantially planar upper wall 1011a-b thereof and is disposed within an open-sided central channel 1028 at a second end 1022 of the inner support portion 1020 so as to be configured to allow for axial slidable movement thereof relative to the inner support portion 1020.
As shown in
As each of the first and second portions 1010a-b are distracted relative to the other, stability of the housing 1010 is maintained, at least in part, by the respective side walls of the projection 1019b and the channel 1019a abutting each other. This is further assisted by the central axial projection 1017a-b abutting respective side walls of the central channel 1028. Rather than simply contacting or abutting, it will be appreciated that the central axial projection 1017a-b may alternatively be slidably engaged with the respective side walls of the central channel 1028.
The upper wall 1011′, 1011″ of the housing 1010 has first and second upper surfaces 1011a′, 1011a″ and first and second lower surfaces 1011b′, 1011b″. As can be observed in
As illustrated in
The first end 1021 of the inner support portion 1020 further includes a distal channel 1029. To this end, the height of the spacer device 1000 can be adjusted, such as by reversibly attaching or engaging a foot portion (not shown) to the distal channel 1029. As a result of this arrangement, the overall height of the spacer device 1000 can be approximated to accommodate the extension gap 400 and/or flexion gap regardless of their dimensions and then this height can be fine tuned with spacer elements (not shown) as required.
Once appropriately positioned within the knee joint 700, the first and second portions 1010a-b of the housing 1010 of the spacer device 1000 can now be extended or distracted along its longitudinal axis a relative to the inner support portion 1020. Similar to that described for the previous embodiment, axial movement of the first and second portions 1010a-b relative to the inner support portion 1020 results in the generation of the lateral and medial inner spaces 1060a-b for receiving a force sensor (not shown) therein. Alternatively and as hereinbefore described, the force sensor can be an electronic force sensor disposed in or on: (a) an upper and/or lower surface of the one or both of the first pair of radially extending tabs 1024a-b of the inner support portion 1020; (b) a lower surface of one or both of the inwardly projecting tabs 1013a-b of the side walls 1012a-b of the housing 1010; (c) the upper surface 1011a of the upper wall 1011 of the housing 1010; (d) an outer or lateral surface of one or both of the side walls 1012a-b, (e) an outer or lower surface of the first end 1021 of the inner support portion 1020; and/or (f) one or more of the spacer elements (not shown).
Additionally, such axial movement results in the formation of a first space 1040 and a second space 1050, each located between or defined by their respective inwardly projecting tab 1013a-b of the side walls 1012a-b and the opposing first pair of radially extending tabs 1024a-b. Each of the first and second spaces 1040, 1050 may then be utilised for receiving a suitably dimensioned spacer element (not shown) so as to maintain the spacer device 1000 in the desired distracted position and allow for measurement of soft tissue tension as well as assessment of dimensions of the extension and/or flexion gap as previously described for the spacer device 100, 500.
The spacer devices 100, 500 and 1000 hereinbefore described may be constructed from a variety of materials, including a surgical grade material, such as surgical grade plastic or metal (e.g., surgical grade stainless steel, titanium, or cobalt-chrome), that is capable of withstanding the forces applied by the femur and tibia thereon, while also preferably being biocompatible and resistant to corrosion.
Throughout the specification the aim has been to describe the preferred embodiments of the invention without limiting the invention to any one embodiment or specific collection of features. It will therefore be appreciated by those of skill in the art that, in light of the instant disclosure, various modifications and changes can be made in the particular embodiments exemplified without departing from the scope of the present invention.
All computer programs, algorithms, patent and scientific literature referred to herein is incorporated herein by reference.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2017900783 | Mar 2017 | AU | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/AU2018/050208 | 3/7/2018 | WO | 00 |
