Patent Application
20140257501
1. Field of Endeavor
The present invention relates to devices, systems, and processes useful to absorb energy, and more specifically in application across a load-bearing joint of a patient.
2. Brief Description of the Related Art
Joint replacement is one of the most common and successful operations in modern orthopaedic surgery. It consists of replacing painful, arthritic, worn or diseased parts of a joint with artificial surfaces shaped in such a way as to allow joint movement. Osteoarthritis is a common diagnosis leading to joint replacement. Such procedures are a last resort treatment as they are highly invasive and require substantial periods of recovery. Total joint replacement, also known as total joint arthroplasty, is a procedure in which all articular surfaces at a joint are replaced. This contrasts with hemiarthroplasty (half arthroplasty) in which only one bone's articular surface at a joint is replaced and unincompartmental arthroplasty in which the articular surfaces of only one of multiple compartments at a joint (such as the surfaces of the thigh and shin bones on just the inner side or just the outer side at the knee) are replaced. Arthroplasty, as a general term, is an orthopaedic procedure which surgically alters the natural joint in some way. This includes procedures in which the arthritic or dysfunctional joint surface is replaced with something else, procedures which are undertaken to reshape or realign the joint by osteotomy or some other procedure. As with joint replacement, these other arthroplasty procedures are also characterized by relatively long recovery times and are highly invasive procedures. A previously popular form of arthroplasty was interpositional arthroplasty in which the joint was surgically altered by insertion of some other tissue like skin, muscle or tendon within the articular space to keep inflammatory surfaces apart. Another previously done arthroplasty was excisional arthroplasty in which articular surfaces were removed leaving scar tissue to fill in the gap. Among other types of arthroplasty are resection(al) arthroplasty, resurfacing arthroplasty, mold arthroplasty, cup arthroplasty, silicone replacement arthroplasty, and osteotomy to affect joint alignment or restore or modify joint congruity. When it is successful, arthroplasty results in new joint surfaces which serve the same function in the joint as did the surfaces that were removed. Any chondrocytes (cells that control the creation and maintenance of articular joint surfaces), however, are either removed as part of the arthroplasty, or left to contend with the resulting joint anatomy. Because of this, none of these currently available therapies are chondro-protective.
A widely-applied type of osteotomy is one in which bones are surgically cut to improve alignment. A misalignment due to injury or disease in a joint relative to the direction of load can result in an imbalance of forces and pain in the affected joint. The goal of osteotomy is to surgically realign the bones at a joint and thereby relieve pain by equalizing forces across the joint. This can also increase the lifespan of the joint. When addressing osteoarthritis in the knee joint, this procedure involves surgical realignment of the joint by cutting and reattaching part of one of the bones at the knee to change the joint alignment, and this procedure is often used in younger, more active or heavier patients. Most often, high tibial osteotomy (HTO) (the surgical realignment of the upper end of the shin bone (tibia) to address knee malalignment) is the osteotomy procedure done to address osteoarthritis and it often results in a decrease in pain and improved function. However, HTO addresses only mechanical alignment and not ligamentous instability. HTO is associated with good early results, but results deteriorate over time.
Other approaches to treating osteoarthritis involve an analysis of loads which exist at a joint. Both cartilage and bone are living tissues that respond and adapt to the loads they experience. Within a nominal range of loading, bone and cartilage remain healthy and viable. If the load falls below the nominal range for extended periods of time, bone and cartilage can become softer and weaker (atrophy). If the load rises above the nominal level for extended periods of time, bone can become stiffer and stronger (hypertrophy). Finally, if the load rises too high, then abrupt failure of bone, cartilage and other tissues can result. Accordingly, it has been concluded that the treatment of osteoarthritis and other bone and cartilage conditions is severely hampered when a surgeon is not able to precisely control and prescribe the levels of joint load. Furthermore, bone healing research has shown that some mechanical stimulation can enhance the healing response and it is likely that the optimum regime for a cartilage/bone graft or construct will involve different levels of load over time, e.g., during a particular treatment schedule. Thus, there is a need for devices which facilitate the control of load on a joint undergoing treatment or therapy, to thereby enable use of the joint within a healthy loading zone.
Certain other approaches to treating osteoarthritis contemplate external devices such as braces or fixators which attempt to control the motion of the bones at a joint or apply cross-loads at a joint to shift load from one side of the joint to the other. A number of these approaches have had some success in alleviating pain but have ultimately been unsuccessful due to lack of patient compliance or the inability of the devices to facilitate and support the natural motion and function of the diseased joint. The loads acting at any given joint and the motions of the bones at that joint are unique to the joint and to the person. For this reason, any proposed treatment based on those loads and motions must account for this variability to be universally successful. The mechanical approaches to treating osteoarthritis have not taken this into account and have consequently had limited success.
Prior approaches to treating osteoarthritis have also failed to account for all of the basic functions of the various structures of a joint in combination with its unique movement. In addition to addressing the loads and motions at a joint, an ultimately successful approach must also acknowledge the dampening and energy absorption functions of the anatomy, and be implantable via a minimally invasive technique. Prior devices designed to reduce the load transferred by the natural joint typically incorporate relatively rigid constructs that are incompressible. Mechanical energy (E) is the action of a force (F) through a distance (s) (i.e., E=F×s). Device constructs which are relatively rigid do not allow substantial energy storage as the forces acting on them do not produce substantial deformations—do not act through substantial distances—within them. For these relatively rigid constructs, energy is transferred rather than stored or absorbed relative to a joint. By contrast, the natural joint is a construct comprised of elements of different compliance characteristics such as bone, cartilage, synovial fluid, muscles, tendons, ligaments, etc. as described above. These dynamic elements include relatively compliant ones (ligaments, tendons, fluid, cartilage) which allow for substantial energy absorption and storage, and relatively stiffer ones (bone) that allow for efficient energy transfer. The cartilage in a joint compresses under applied force and the resultant force displacement product represents the energy absorbed by cartilage. The fluid content of cartilage also acts to stiffen its response to load applied quickly and dampen its response to loads applied slowly. In this way, cartilage acts to absorb and store, as well as to dissipate energy.
With the foregoing applications in mind, it has been found to be necessary to develop effective structures for mounting to body anatomy. Such structures should conform to body anatomy and cooperate with body anatomy to achieve desired load reduction, energy absorption, energy storage, and energy transfer. These structures should include mounting means for attachment of complementary structures across articulating joints.
Currently, an energy absorbing system developed by Moximed is implanted in two pieces. In that procedure: the surgeon gains access to the medial knee from the contralateral side; two 5-8 cm incisions are made, connected by a skin bridge and a subcutaneous tunnel; a femoral target, i.e., location for mounting the femoral base, is selected; the absorber alignment relative to the joint, is determined; a femoral base is selected and implanted; the energy absorber and the tibial base are connected ex-vivo; the absorber is inserted into the tissue tunnel; the absorber is connected to the femoral base; the tibial base is aligned and fixed; and the absorber is activated by releasing a restraining device.
For these implant structures to function optimally, they must not cause an adverse disturbance to joint motion. Therefore, what is needed is an approach which addresses both joint movement and varying loads as well as complements underlying or adjacent anatomy.
According to a first aspect of the invention, an implantable energy absorbing system useful for absorbing energy from a joint of a patient comprises a proximal base configured and arranged for implantation adjacent to said joint, a distal base configured and arranged for implantation adjacent to said joint on a side of said joint opposite said proximal base, and an energy absorbing device attached to both the proximal base and the distal base, the energy absorbing device comprising a spring having a hollow interior, and a piston at least partially located in said spring hollow interior, wherein the spring is a metallic spring and the piston is formed of a non-metallic material.
At least one of the spring and the piston can be formed of PAEK.
The energy absorbing device and the two bases can comprise two ball-and-socket connectors connecting together each base with the energy absorbing device.
The energy absorbing device can include proximal and distal ends, and each of said ball-and-socket connectors can comprise a socket on one of said bases and a ball on each of said absorbing device proximal and distal ends, each of said balls being rotatably received in one of said sockets.
At least one base can include a removable socket connector and a mating structure on said base, the mating structure being configured and arranged to receive said removable socket connector, the removable socket connector can include a socket body, a socket formed in said socket body configured to receive said ball, and a lumen extending from said socket, and the piston can comprise a ball and is sized so that said piston can be pushed through said lumen until said ball is captured in said socket.
At least one of the bases can comprise a lumen having two ends, said socket being located at one of said base lumen ends, and said piston can comprise a ball and is sized so that said piston can be pushed through said lumen until said ball is captured in said socket.
Such a system can further comprise a plug sized to at least partially fill said base lumen.
The base can comprise a socket body split in two portions, each of said portions including a mating portion which permits the two socket body portions to be removably connected together.
The spring can comprise a helical spring.
The spring hollow interior has a length, and said piston can extend within said spring hollow interior a distance less than said length.
The spring is not secured to opposite ends of the energy absorbing device and is floating on the piston.
The energy absorbing device can further comprise two ends, the piston and spring extending toward each other in opposite directions from each of said ends, and a piston guide tube extending within said spring and around said piston.
The energy absorbing device can further comprise two ends, the piston and spring extending toward each other in opposite directions from each of said ends, and a tubular sheath positioned on the outside of at least part of the spring, the sheath being connected to one of said two end.
The piston can comprise lateral cutouts.
The piston also comprise a base end adjacent one of said bases, a free end opposite said base end, and a blind bore extending along said piston from said free end.
The piston can also further comprise at least one lateral cutout extending between said blind bore and the exterior of said piston.
At least one lateral cutout can comprise at least one part-circumferential cutout.
At least one lateral cutout can comprises a plurality of part-circumferential cutouts spaced along said piston between said ends.
The piston can comprise a frustoconical taper along its length.
The piston can comprise at least one groove extending in a direction between said ends.
The piston can also comprise a base end adjacent one of said bases, a free end opposite said base end, wherein said free end comprises a metal tip, and wherein portions of said piston between said metal tip and said base end are formed of PAEK.
The piston can further also comprise a base end adjacent one of said bases, a free end opposite said base end, and a telescoping piston extension positioned around said free end.
The telescoping piston extension can include a blind bore having an inner diameter, and said piston free end has an outer diameter less than said blind bore inner diameter such that said telescoping piston extension can slide along said piston free end.
The telescoping piston extension can also include a lip on said blind bore, and said piston includes a lip adjacent said free end sized to catch on said telescoping piston extension lip and prevent said telescoping piston extension from sliding off said piston free end.
The piston can comprise at least one flattened exterior portion.
At least one of the bases can comprise a top surface and a periosteum-contacting surface, at least one screw hole extending through said base between said top surface and said bone-contacting surface, and at least one periosteum-contacting ring on and extending outward from said periosteum-contacting surface, adjacent to and surrounding said at least one screw hole.
At least one of the bases can also comprise a top surface and a periosteum-contacting surface, and at least one standoff extending from said periosteum-contacting surface.
At least one of said bases can comprise slots and/or lumens formed through the base.
Another aspect includes an implantable energy absorbing system useful for absorbing energy from a joint of a patient, the system comprising a proximal base configured and arranged for implantation adjacent to said joint, a distal base configured and arranged for implantation adjacent to said joint on a side of said joint opposite said proximal base, and an energy absorbing device attached to both the proximal base and the distal base, the energy absorbing device comprising a spring having a hollow interior, and a piston at least partially located in said spring hollow interior, wherein the energy absorbing device and the two bases comprise two ball-and-socket connectors connecting together each base with the energy absorbing device, at least one of the ball and socket is non-metallic.
Yet another aspect includes a base useful for implantation adjacent to a joint, the base comprising a top surface and a periosteum-contacting surface, at least one screw hole extending through said base between said top surface and said bone-contacting surface, and at least one periosteum-contacting ring on and extending outward from said periosteum-contacting surface, adjacent to and surrounding said at least one screw hole.
Another aspect includes an energy absorber spacer comprising a trough-shaped portion having two sidewalls, a bottom wall connected to each of the sidewalls, and an open top, and a handle extending from said trough-shaped portion and away from said bottom wall.
The bottom wall and said two sidewalls can define a trough with open ends.
Yet another aspect includes a tibial alignment guide comprising a base having base body and a pin receiver on said base body including a through lumen, and a post having a through lumen and first and second ends, and an indicator arm, wherein the post and the indicator arm comprise complementary mating structures which permit the indicator arm to be mounted adjacent to said post first end extending away from the post at a single fixed angular orientation, and wherein said post second end and said base together comprise a removable connector configured and arranged to permit the post to be connected to the base at a single, fixed angular orientation.
The removable connector can comprise an enlarged bearing and a protrusion extending laterally from said bearing, a toroidal receiver including an interior surface sized and configured to receive said enlarged bearing, and a tapered slot in said toroidal receiver sized to receive said protrusion, such that when said enlarged bearing is positioned in said toroidal receiver with said protrusion located in said tapered slot, said indicator arm is oriented in a single fixed angular orientation relative to said post lumen and said base pin receiver.
A further aspect relates to a method of implanting an energy absorbing system into a patient having a joint with a joint line, the method comprising forming a femoral incision that begins slightly distal to a midpoint of Blumensaat's line and extends away from the joint line, forming a tibial incision that begins at a posterior tibial K-wire hole and extends through the location of the distal tibial K-wire hole, forming a tissue tunnel from the tibial incision to the femoral incision, aligning a tibial positioning guide with a femoral trial indicator to correctly align the tibia and femur, inserting a K-wire through a hole in a distal portion of the tibial positioning guide, positioning two femoral and two tibial K-wires in the femur and tibia, respectively, removing the femoral trial and the tibial positioning guide, and inserting a femoral end of an energy absorbing system, including a femoral base, an absorber, and a tibial base, connected together, through the tibial incision and bringing the femoral base through the tunnel posterior to the femoral K-wires.
Such a method can further comprise engaging the femoral Base with the two femoral K-wires and stabilizing the femoral base by inserting a K-wire through a hole in the femoral base.
Such a method can further comprise setting a minimum spacing between the absorber and the patient's tissues, including introducing an absorber spacer through the femoral incision and beneath the absorber.
Such a method can further comprise positioning the absorber parallel to the tibial shaft.
Such a method can further comprise mounting the femoral base to the femur, and mounting the tibial base to the tibia.
Such a method can further comprise activating the absorber.
Yet a further aspect includes a method of implanting an energy absorbing system in a patient, the method comprising inserting, as a single interconnected unit, a femoral base, a tibial base, and an absorber rotatably connected to the femoral and tibial bases, positioning the femoral base on the distal end of a femur, positioning the tibial base on the proximal end of the tibia, positioning the absorber across the knee joint to absorb load ordinarily carried by the knee joint, and securing the femoral and tibial bases to the bone with bone screws.
The inserting step can include inserting through a tissue tunnel from an incision adjacent the tibia.
The step of positioning the absorber can include positioning the absorber substantially parallel to the tibial axis when the knee joint is at full extension.
Still other aspects, features, and attendant advantages of the present invention will become apparent to those skilled in the art from a reading of the following detailed description of embodiments constructed in accordance therewith, taken in conjunction with the accompanying drawings.
The invention of the present application will now be described in more detail with reference to exemplary embodiments of the apparatus and method, given only by way of example, and with reference to the accompanying drawings, in which:
Referring now to the drawing figures, like reference numerals designate identical or corresponding elements throughout the several figures. The drawings, which are provided by way of example and not limitation, illustrate disclosed embodiments which are directed towards apparatus and methods for treating the knee joint. However, these embodiments may also be used in treating other body joints, and to alleviate pain associated with the function of diseased or misaligned members forming a body joint without limiting the range of motion of the joint. The embodiments described below relate to apparatuses and methods for adjusting the amount of load an energy absorbing device can manipulate. Some embodiments include an energy absorbing device including the use of a single spring member, however other number of spring members may also be used.
Certain of the embodiments include energy absorbing devices designed to minimize and complement the dampening effect and energy absorption provided by the anatomy of the body, such as that found at a body joint. It has been postulated that to minimize pain, load manipulation or absorption of 1-40% of forces, in varying degrees, may be necessary. Variable load manipulation or energy absorption in the range of 5-20% can be a target for certain applications.
In body anatomy incorporating energy absorbing systems as described below, less forces are transferred to the bones and cartilage of the members defining the joint, and a degree of the forces between body members is absorbed by the energy absorbing system. In one embodiment, the energy absorbing system can be initially configured to eliminate, variably reduce or manipulate loads to a desired degree, and to be later adjusted or altered as patient needs are better determined or change.
In applications to the knee joint, the energy absorbing system can be designed to absorb medial compartment loads in a manner that completely preserves the articulating joint and capsular structures. One embodiment of the present invention is a load bypassing knee support system comprised of a kinematic load absorber, two contoured base components and a set of bone screws. The implanted system is both extra articular and extra capsular and resides in the subcutaneous tissue on the medial (or lateral) aspect of the knee. The device is inserted through two small incisions above the medial femoral and tibial condyles. The base components are fixed to the medial cortices of the femur and tibia using bone screws. The energy absorber having a spring value of about twenty to thirty pounds can provide therapeutic benefit for patients of 275 pounds or less. Higher spring forces would provide greater reduction in joint load and may correlate to greater symptom (i.e., pain) relief.
It has been recognized that knee forces have multiple components. There are a quadriceps force FQ and a ground reaction force FG directed generally longitudinally along a leg and there are lateral compartment forces FL and medial compartment forces FM. There is, however, no conventional clinical measure of FM or FL. On the other hand, there are non-axial knee forces which result in a moment being applied across the joint referred to as a knee adduction moment. The knee adduction moment (KAM) can be measured clinically. The measurements are useful as KAM can be considered to be a clinical surrogate measure for knee forces.
It has been further observed that a high knee adduction moment correlates with pain. That is, it would be expected that a group of people with diseased joints having lower KAM may not have pain whereas individuals with a relatively higher KAM would experience pain. Thus, an active reduction of knee adduction moment can reduce pain. The system of the present invention reduces the KAM of the patient.
It has also been found that a medial compartment of a knee of an average person with osteoarthritis can benefit from an absorber set for compression between 1 mm and 10 mm, and preferably 3-6 mm with a spring or absorber element that accommodates a range from 20-60 pounds. In a preferred embodiment, the absorber is set for about 4 mm of such compression and a pre-determined load of about 30 pounds.
In each of the disclosed embodiments, various features can be incorporated from other of the disclosed embodiments. Moreover, each of the contemplated embodiments can include springs formed to provide desirable energy absorbing which varies as the spring is compressed during various degrees of flexion and extension of joint markers to which the energy absorbing device is attached. The term “spring” is used throughout the description but it is contemplated to include other energy absorbing and compliant structures can be used to accomplish the functions of the invention as described in more detail below.
In certain situations, it has been found to be a benefit to implant the energy absorbing device in an inactivated condition, only later taking steps, perhaps several weeks later, to place the device into an activated state. In this way, the device can become further affixed to bone as the bone and surrounding tissue grows over portions of the device. Accordingly, each of the disclosed embodiments can be so implanted and later activated and adjusted through a patient's skin.
Further, various approaches to adjusting the energy absorbing device are contemplated and disclosed below. That is, various approaches to adjusting structure between piston and arbor structure as well as adjusting mounts to which the piston and arbor structures are configured to engage are disclosed. In the former regard, adjustable collars and adjustable link ends are contemplated approaches. Additionally, any of a variety of approaches to achieving adjustment through a patient's skin or through an incision, either through direct engagement with the energy absorbing device with a tool or by applying forces to the device through the surface of the skin, can be incorporated to fill a perceived need.
The singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a hole” includes reference to one or more of such holes, and reference to “the shaft” includes reference to one or more of such shafts.
Concentrations, amounts, and other numerical data may be presented herein in a range format. It is to be understood that such range format is used merely for convenience and brevity and should be interpreted flexibly to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited.
For example, a range of 1 to 5 should be interpreted to include not only the explicitly recited limits of 1 and 5, but also to include individual values such as 2, 2.7, 3.6, 4.2, and sub-ranges such as 1-2.5, 1.8-3.2, 2.6-4.9, etc. This interpretation should apply regardless of the breadth of the range or the characteristic being described, and also applies to open-ended ranges reciting only one end point, such as “greater than 25,” or “less than 10.”
Turning now to the drawing figures, several exemplary embodiments are illustrated.
While prior devices have been formed of biocompatible metals, the inventors herein have determined that other materials which are biocompatible, have high wear resistance, are durable, non-interfering with MRI scanning, and are capable of being manufactured into complex geometries, are advantageously used to form some or all of the subcomponents of an energy absorbing system as described herein. Examples of materials include, but are not limited to: PAEK, PAEK composites, polycarbonate urethanes (PCU), PCU composites, ceramics, and pyrocarbon. PAEK (poly aryl ether ketone), e.g., PEEK (poly ether ether ketone), is a significantly advantageous material out of which to form some or all of the subcomponents of an energy absorbing system described herein. More specifically, each of the bases, which connect the system to a patient's bone, and the energy absorbing device there between, can perform significantly better than when those structures are formed of metals, for a number of reasons. Without being limited to a particular justification, when formed of PEEK, structures which move relative to each other (i.e., PEEK-on-PEEK articulation), for example ball-and-socket joints, do not pose the risk of the generation of metal particles when in vivo, that prior devices pose. Furthermore, PAEK is MRI compatible, which metal subcomponents generally are not, yet are radiographically invisible. According to an exemplary, yet further advantageous embodiment, CFR (carbon fiber reinforced) PEEK is used for some or all of the subcomponents described herein, with preferably 30% fiber, although other amounts and methods of reinforcement are also contemplated for portions of the device which are to be more rigid. Fibers used for reinforcement may include continuous fibers, chopped or milled fibers or other types of reinforcement. Portions, such as the spring, which are to flex in use, are advantageously formed of neat (unfilled) PEEK. Although PEEK or CFR PEEK are described as preferred materials for the subcomponents of the energy absorbing system other non-metallic materials including ceramics, biocompatible polymers and filled polymer materials can also achieve many of the advantages described herein and are useable in the energy absorbing systems.
Yet another advantageous aspect of devices described herein includes that the pistons can be formed to include flexibility enhancements, which permit the energy absorbing device to have improved lateral or transverse flexibility relative to prior devices, which assists in avoiding tissue impingement when implanted.
The energy absorbing device 106 includes a spring base or arbor 108, a piston base 110, a spring connected to the arbor 108, and a piston 114 connected to the piston base 110 and inside of the spring 112. As illustrated in
With more detailed reference to
Each end of the energy absorbing device 106 includes a structure which is configured to mate with corresponding structures on each base 102, 104, and permit relative rotational motion between them, while restricting or preventing the mating structures from becoming disassembled. In the exemplary embodiment of
With continued reference to
Turning now to
Turning now to
The flexible pistons described in
The base also advantageously includes a stand-off 624 extending downwardly and away from a socket connector 626, which is configured to receive a ball connector of an energy absorbing device as described elsewhere herein. The stand-off 624 assists in stabilizing the base relative to the bone to which the base 640 is mounted, and to a connected energy absorbing device. The stand-off 624 assists in maintaining a sufficient distance between the ball and socket connection and the underlying tissue to limit impingement of the tissue on the energy absorbing device. The base 640 also may include one or more through holes for temporarily receiving a K-wire or other securing member during positioning and securing of the implant to the bone. The term K-wire as used herein is intended to mean any guide pin, Steinmann pin or Kirschner wire.
One other example of a manner for engaging a ball and a socket is to provide an internally threaded ball similar to the ball 150 shown in
The post 904 includes an elongate tubular portion 912, including a lumen 914 extending entirely through the portion 912 from a top opening 918 to a bottom opening 916, which is sized to receive a K-wire therethrough. The bottom of the post 904 includes an enlarged bearing 922, from which a locator protrusion 924 laterally extends. While the post 904 is illustrated as being generally tapered, it may be formed of other shapes.
The base 906 includes a base body 930 which is generally shaped similar to a tibial base (e.g., 102). The base 906 includes a toroidal receiver 932 at one end, which is configured to receive the bearing 922 therein and hold the bearing on a downwardly tapered inner surface 934 of the toroid. A slot 936 is formed in the side of the receiver 932 and into the body 930, the portion at the receiver being sized to receive the protrusion 924 and prevent it from moving side-to-side. Thus, when the arm 902 and post 904 are inserted into the base 906, the slot 936 receives the protrusion 924 and accurately orients the straight portion 908 of the indicator arm 902 in a predetermined direction relative to the base 906.
The base 906 also includes a wire receiver 940, formed on a medial side of the base body 930 near an end of the body away from the receiver 932. The wire receiver 940 includes a lumen 942 extending entirely from a top opening 944 to a bottom opening 946, and is sized to receive a K-wire therein, for reasons explained in greater detail elsewhere herein. Alternatively, the receiver 932 and slot 936, and the bearing 922, can be reversed, that is, formed on the other of the post 904 and the base 906.
Exemplary methods of treating a patient with devices as described herein are similar in some respects to those described in the aforementioned co-pending U.S. patent applications. More specifically, once a system, such as system 100, is implanted across a patient's joint, e.g., knee, the system can absorb energy that would otherwise be transmitted through the structures of the joint. When the joint is flexed, the piston 114 slides inside the spring 112, with the proximal end of the piston moving relatively towards the distal end of the spring. This relative distal movement of the piston is unimpeded, because there are no structures of the system 100 which inhibit this motion; however, because the length of the piston is selected to extend most or all of the way along the interior of the spring, and because flexion of the joint is naturally limited, the piston remains inside the spring. When the joint is straightened, or nearly straightened, the shoulder 122 (see
According to an exemplary embodiment, a method of implanting an energy absorbing system, extracapsularly, includes a number of steps in an orthopedic procedure.
The surgeon accesses the medial aspect of the operative knee with two 5-8 cm incisions connected by a subcutaneous tissue tunnel. The femoral base is placed sub-vastus on the femur, and the tibial base is placed anterior to the insertion of the pes anserinus. The tibial base placement is on the anterior-medial aspect of the tibia in the following procedure. As shown in
The targeting tool 1000 can then be used to place a Kirschner wire (K-wire). When the K-wire appears as a dot within the rings of the targeting tool this confirms that the K-wire is entering the femur at the correct angle and the K-wire can be inserted into the bone for use in positioning the femoral base. With the knee in full extension, a femoral alignment guide 1010 as shown by way of example in U.S. patent application Ser. No. 13/564,095, can be placed over the K-wire shown in Step 2 of
With the femoral trial device 1020 over the target femoral K-wire, an indicator of the femoral trial device is aligned with the distal tibial K-wire placed in Step 2. The indicator 1022 of the femoral trial device represents the correct orientation of the absorber 1030. Two K-wires can be inserted through the holes in the upper portion of the femoral trial 1020 in Step 3 to located the femoral base 1040 in Step 5.
With the femoral trial still in place, Step 4 shows the insertion of the tibial positioning guide 900 (described elsewhere herein) over the distal tibial K-wire. The indicator 908 of the tibial positioning guide 900 is positioned parallel to the femoral trial indicator 1022. The indicator of the tibial positioning guide represents the correct orientation of the absorber 1030 in Steps 5 and 6. A K-wire is then inserted through the hole in the distal portion of the tibial positioning guide 900. This K-wire will guide tibial base orientation during implantation.
The femoral trial 1020 and the tibial positioning guide 900 can then be removed in preparation for insertion of the implant.
In one example, the implant including a femoral base, an absorber, and a tibial base, all connected together; is then inserted through the tibial incision to bring the femoral base 1040 through the tunnel posterior to the femoral K-wires. The femoral base 1040 includes slots which allow the base to be slid onto the two femoral K-wires to position the base. The femoral base 1040 can also be stabilized by inserting a K-wire through the hole in the femoral base.
The absorber spacer 800 (described elsewhere herein) can be inserted in through the femoral or tibial incision and beneath the absorber 1030. The absorber spacer 800 assists in setting a minimum spacing between the absorber and the patient's tissues, so there is less of a possibility of tissue impingement by the absorber.
One or more K-wires may be placed next to the absorber to stabilize the absorber during implantation of the bases. For example, a K-wire may be placed on each side of the distal end of the absorber 1030. As shown in Step 5, the tibial base 1050 can be positioned by placing the distal posterior edge of the base against the distal-most tibial K-wire positioned in Step 4. The posterior border of the tibial base may contact the pes anserinus. The pes may be slightly elevated prior to tibial base fixation. With the tibial base stabilized with K-wires, the femoral and tibial bases are secured to the bone with bone screws. The order of screw insertion and length of screws is at the discretion of the surgeon.
In a final step shown in Step 6, any restraining device which prevents the energy absorbing device of the system from operation, e.g., a restraining cable is cut and removed and the absorber spacer 800 is removed. After confirming operation of the implant throughout full range of flexion/extension and varus/valgus motion, the incision can be closed.
While the invention has been described in detail with reference to exemplary embodiments thereof, it will be apparent to one skilled in the art that various changes can be made, and equivalents employed, without departing from the scope of the invention. The foregoing description of the preferred embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. The embodiments were chosen and described in order to explain the principles of the invention and its practical application to enable one skilled in the art to utilize the invention in various embodiments as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto, and their equivalents. The entirety of each of the aforementioned documents is incorporated by reference herein.
| Number | Date | Country | |
|---|---|---|---|
| 61775365 | Mar 2013 | US |
