Patent Description:
A natural knee joint typically undergoes a degree of rotation between the tibia and the femur during flexion. Specifically, the femur can rotate in a transverse plane relative to the tibia. Thus, it can be desirable to replicate the natural rotational alignment of the tibia and femur when implanting one or more orthopedic femoral and tibial components.

Frequently the rotation of the tibial component is set independently of the femoral component, and solely based on tibial bony landmarks. In some cases, this can result in mal-rotation of the tibial component with respect to the femoral component. In these cases, if a highly conforming articulation design between femur and tibia is used, when the prosthesis is loaded, the mating tibial-femoral articulating surfaces will drive the tibial component into rotational alignment with the femoral component. This shifting of the tibial component will in turn rotate the entire tibial bone into a non-physiologic orientation with respect to the femur. This can result in pain, stiffness, and a knee that does not feel normal.

Some surgeons have attempted to match natural tibial rotation by a technique called "floating the tibia. " In this approach, the femoral trial can be placed and a trial reduction can be performed with the tibial bearing placed in a tibial sizing tray that is free to rotate and translate on the surface of the proximal tibial resection. The tibial sizing tray is thus free to "float" between the resected tibia and the femoral trial. The knee is taken through a range of motion and then out to full extension. The surgeon can then use a pen or Bovie to mark a point on the tibial bone corresponding to the front of the tibial sizing plate. The assumption inherent in this approach is that the conformity between the bearing and the femoral component will force the bearing (and thus the tibial sizing plate) to shift into rotational alignment with the femoral component.

Examples of prosthetic knee implants are described in <CIT> and <CIT>.

The present inventors have recognized, among other things, that there can be problems associated with attempting to match the natural rotation of the tibia to the femur using the "floating tibia" technique. First, when the knee is taken out to full extension, the tibial component can be under compressive load from the femur which can inhibit relative motion of the tibial component on the tibial bone. Second, contemporary total knee arthroplasty (TKA) articulations can be designed with a measure of rotational laxity. There can be insufficient conformity for the femoral component to drive movement of the tibial component, particularly when it is under compressive load. Third, when the surgeon marks the point on the anterior bone denoting the front of the tibial trial, there is typically no corresponding mark at the posterior tibia to define the axis of rotation. The surgeon can align to the front mark, but needs to estimate where the posterior of the tibial trial was oriented.

The present subject matter can help provide a solution to various problems associated with matching the natural rotation of the tibia to the femur when implanting prosthetic knee components.

In an example, the present subject matter can help provide a solution to these problems, such as by providing a tibial spacer paddle that can comprise a spacer block, first and second feet, first and second alignment chamfers, an alignment slot, and a handle. The spacer block can comprise a first bearing surface, a second bearing surface disposed opposite the first bearing surface, and an edge periphery region connecting the first bearing surface and the second bearing surface. The first foot can extend from the first bearing surface at the edge periphery region. The second foot can extend from the first bearing surface at the edge periphery region spaced from the first foot. The first alignment chamfer can extend into the edge periphery region and the second bearing surface opposite the first foot. The second alignment chamfer can extend into the edge periphery region and the second bearing surface opposite the second foot. The alignment slot can extend into the edge periphery region opposite the first and second feet. The handle can extend from the spacer block.

In another example, a tibial spacer system can comprise a spacer block, a first peg, a second peg, an alignment slot and a handle. The spacer block can comprise a first bearing surface, a second bearing surface disposed opposite the first bearing surface, and an edge periphery region connecting the first bearing surface and the second bearing surface. The first peg can extend from the first bearing surface. The second peg can extend from the first bearing surface spaced from the first peg. The alignment slot can extend into the edge periphery region. The handle can extend from the spacer block.

In still another example, a tibial spacer system can comprise a provisional component, a trial bearing and a pivot coupling. The provisional component can comprise an articulating surface configured to engage condylar surfaces of a femoral component, a first bearing surface disposed opposite the articulating surface, and a first edge periphery region connecting the articulating surface and the first bearing surface. The trial bearing can comprise a bone engagement surface, a second bearing surface disposed opposite the bone engagement surface, and a second edge periphery region connecting the bone engagement surface and the second bearing surface. The pivot coupling can connect the first bearing surface and the second bearing surface. The pivot coupling can be configured to permit the trial bearing to rotate relative to the provisional component.

The present invention is defined in claim <NUM> and concerns a tibial spacer system. The detailed description is included to provide further information about the present invention.

<FIG> is a perspective view of tibial spacer paddle <NUM> having alignment feet 12A and 12B and indicator groove <NUM> disposed in spacer block <NUM>. <FIG> is a side view of tibial spacer paddle <NUM> of <FIG> showing an angle of alignment feet 12A and 12B relative to bearing surface 18A. <FIG> is a top view of the tibial spacer paddle of <FIG> showing a location for the indicator groove <NUM>. <FIG> are discussed concurrently.

Spacer block <NUM> can include first bearing surface 18A, second bearing surface 18B, edge periphery surface <NUM>, notch <NUM> and handle <NUM>. Edge periphery surface <NUM> can include chamfers 26A and 26B opposite alignment feet 12A and 12B, respectively. Notch <NUM> and indicator groove <NUM> can extend into spacer block <NUM> to form first condylar portion 28A and second condylar portion 28B. Handle <NUM> can extend from edge periphery surface <NUM> of spacer block <NUM> and can include first segment 30A and second segment 30B.

Spacer block <NUM> is configured to be inserted or otherwise disposed between surfaces, particularly resected surfaces, of a tibia and femur, as shown in <FIG>. First bearing surface 18A can be configured to face toward a tibia and second bearing surface 18B can be configured to face toward a femur. First segment 28A and second segment 28B can be configured to align with condyles of the femur. Edge periphery surface <NUM> can be shaped so that first segment 28A and second segment 28B can engage medial and lateral condyles of left and right leg femurs. In other examples, spacer block <NUM> can be configured specifically for a left or right leg knee. As will be discussed in greater detail below with reference to <FIG>, indicator groove <NUM> can provide an indication of the rotational alignment between the tibia and the femur as the tibia moves through extension and flexion in order to provide alignment information for implantation of prosthetic femoral and tibial components.

Alignment feet 12A and 12B can be located at edges of first segment 28A and second segment 28B, respectively, of bearing surface 18A so as to extend from edge periphery surface <NUM>. In examples, alignment feet 12A and 12B are positioned to be located at a posterior side of the tibia and femur. Chamfers 26A and 26B are disposed opposite feet 12A and 12B, respectively, in bearing surface 18B and remove a portion of spacer block <NUM> at edge periphery surface <NUM> so that the tibia can be rotated against second bearing surface 18B. Notch <NUM> can extend between first segment 28A and second segment 28B in order to provide visibility of the tibia. In an example, chamfers 26A and 26B can form an angle θ1 (<FIG>) with bearing surface 18B of approximately one-hundred-thirty-five degrees.

Handle <NUM> can extend from edge periphery surface <NUM> to provide structure for a surgeon to handle and manipulate spacer block <NUM>. Handle <NUM> can extend from an anterior portion of spacer block <NUM> so that tibial spacer paddle <NUM> can be inserted into an incision in an anterior portion of a knee joint. If desired, an instrument, such as a retractor, can be used to hold tibia T and femur F in a retracted position to allow for insertion of tibial spacer paddle <NUM>. Handle <NUM> can extend from edge periphery surface <NUM> offset from a center of spacer block <NUM> to provide space for placement of indicator groove <NUM>, which can be placed at the center of spacer block <NUM>. First segment 30A of handle <NUM> can extend from second portion 28B of spacer block <NUM> at posterior end 32A. First segment 30A can be curved toward indicator groove <NUM> so that anterior end 32B is brought closer to indicator groove <NUM>. Second segment 30B can be attached to anterior end 32B so that second segment 30B substantially aligns with alignment slot <NUM>. Anterior end 32B can be planar and can extend parallel to indicator groove <NUM>. Second segment 30B can comprise an elongate body having a central axis A1 that is configured to extend axially in the direction of indicator groove <NUM>. Handle <NUM> therefore provides an indication of the center of spacer block <NUM> and points in the direction of indicator groove <NUM> to provide a surgeon with tactile indicator for the orientation of tibial spacer paddle <NUM>. Second segment 30B can include access bores 34A and 34B that can provide various functions, such as to allow tools or instruments to be inserted through handle <NUM>.

Bearing surface 18A can be configured to face a resected tibia surface. Bearing surface 18B can be configured to face a resected femur surface. The resected tibia and femur surfaces can be planar or nearly planar. Bearing surfaces 18A and 18B can also be planar or nearly planar so as to readily slide against the resected tibia and femur surfaces. Indicator groove <NUM> can extend all the way through spacer block <NUM> from first bearing surface 18A to second bearing surface 18B so that the resected tibia can be accessed through indicator groove <NUM>. Indicator groove <NUM> can be tapered between first bearing surface 18A and second bearing surface 18B. Indicator groove <NUM> can be wider at first bearing surface 18A than at second bearing surface 18B. As such, indicator surface can be configured to guide an instrument, such as a pen, Bovie, marker, scalpel or pick, toward the tibia. The greater width of indicator groove <NUM> at first bearing surface 18A can facilitate insertion of the instrument by a surgeon into indicator groove <NUM>, while the narrower width of indicator groove <NUM> at second bearing surface 18B can facilitate guidance of the instrument to a more precise location on the tibia.

Alignment feet 12A and 12B can be configured to hold spacer block <NUM> into engagement with the resected femur. Posterior surfaces 36A and 36B can extend from first bearing surface 18A at right angles or near right angles. However, in other examples, posterior surfaces 36A and 36B can extend at other angles relative to bearing surface 18A for use with surgical procedures where the resected femur surface is not perpendicular to a resected flat anterior surface of the femur (as shown in <FIG>). Thus, bearing surface 18A can remain engaged with a distal resected surface of the femur while posterior surfaces 36A and 36B can remain engaged with posterior resected surfaces of the femur. If desired, a surgeon can grasp handle <NUM> to facilitate engagement of spacer block <NUM> and the femur. As the tibia moves from flexion to extension, the tibia can rotate against bearing surface 18B along vertical axis A2, as described in greater detail with reference to <FIG>.

<FIG> is a side view of tibial spacer paddle <NUM> of <FIG> inserted between resected tibia T and resected femur F in approximately sixty degrees of flexion as defined by angle θ2. Resected tibia T can include proximal surface S1. Resected femur F can include distal surface S2, first posterior surface S3A, second posterior surface S3B, angled anterior surface S4, first quarter surface S5A and second quarter surface S5B. Tibia T and femur F can be resected using any conventional resection process. Tibial spacer paddle <NUM> depicted in <FIG> is configured to be used with the resected surfaces shown in <FIG>. However, tibial spacer paddle <NUM> can be used with other resections. Additionally, tibial spacer paddle <NUM> can modified to be used with other resections. Tibial spacer paddle <NUM> can be configured in various embodiments to allow rotation of one of tibia T and femur F against tibial spacer paddle <NUM> while having surfaces that permit tibial spacer paddle <NUM> to be held in flush engagement with the other of tibia T and femur F.

With tibia T and femur F in flexion, tibial spacer paddle <NUM> can be inserted between distal surface S2 of Femur F and proximal surface S1 of tibia T. For example, tibia T and femur F can be positioned into approximately sixty degrees of flexion to receive tibial spacer paddle <NUM>, as defined by angle θ2, between femur axis AF and tibia axis AT. A surgeon can grasp handle <NUM> to insert spacer block <NUM> into an incision in a knee of a patient and further into a space between tibia T and femur F. Alignment feet 12A and 12B can be slipped around distal surface S2 to engage first and second posterior surfaces S3A and S3B. Bearing surface 18A can be positioned against distal surface S2. Chamfers 26A and 26B can be positioned to contact proximal surface S1. With femur F and tibia T disposed in sixty degrees of flexion, as shown in <FIG>, chamfers 26A and 26B will be slightly canted with respect to proximal surface S1 such that an edge of chamfers 26A and 26B and edge periphery surface <NUM> is engaged with proximal surface S1. In other words, if femur F and tibia T were disposed in forty-five degrees of flexion, chamfers 26A and 26B would be flush with proximal surface S1 due to angle θ1 being one-hundred-thirty-five degrees.

<FIG> is a posterior view of the tibial spacer paddle <NUM> of <FIG> showing alignment feet 12A and 12B engaged with first posterior surface S3A and second posterior surface S3B of femur F. Notch <NUM> is shown between feet 12A and 12B and shows proximal surface S1 therebetween. Bearing surface 18A is shown engaged with distal surface S2. As such, feet 12A and 12B can be rotated on proximal surface S1 as tibia T rotates relative to femur F as tibia T and femur F move between extension and flexion. Tibial spacer paddle <NUM> can remain engaged with tibia T due to pressure applied by tendons and ligaments connecting tibia T and femur F.

<FIG> is a side view of tibial spacer paddle <NUM> of <FIG> shown with tibia T in full extension. As tibia T moves into full extension from the flexion position of <FIG>, tibia T rotates so that bearing surface 18B engages proximal surface S1 of tibia T. With bearing surface 18A already engaged flush with distal surface S1, spacer block <NUM> can be positioned squarely between distal surface S1 and proximal surface S1. Feet 12A and 12B keep the rotational orientation of tibial spacer paddle <NUM> constant with respect to the axis of femur F, thereby allowing tibia T to rotate along the axis of tibia T against bearing surface 18B as tibia T moves into extension. Indicator groove <NUM> points to a portion of tibia T that shows where the center of femur F points to on proximal surface S1, thus showing the natural rotational position of tibia T relative to femur F.

Spacer block <NUM> can have a thickness between bearing surface 18A and bearing surface 18B that can be matched to various prosthetic devices. For example, the thickness can be equal to the total thickness of a femoral component and a tibial component intended to be implanted on femur F and tibia T, respectively. The thickness of spacer block <NUM> can allow the ligaments and tendons of femur F and tibia T to hold spacer block <NUM> in the natural tension of the knee joint. Different tibial spacer paddles <NUM> can be provided with different thicknesses in order to allow a surgeon to trial the knee joint for different prosthetic devices at a desired level of tension.

<FIG> is an anterior perspective view of tibial spacer paddle <NUM> of <FIG> illustrating natural rotation of tibia T. As mentioned, with bearing surface 18A flushly engaged with distal surface S2 of femur F and bearing surface 18B flushly engaged with proximal surface S1 of tibia T, tibia T is free to rotate against spacer block <NUM>, as shown by arrows of rotation R1 and R2. Resected surface S4 of femur F can allow access to indicator groove <NUM> for both visual inspection and insertion of a tool or instrument.

<FIG> is an anterior perspective view of tibial spacer paddle <NUM> of <FIG> with marking <NUM> of the resected tibial surface at indicator groove <NUM>. <FIG> is the same as <FIG> except for arrows of rotation R1 and R2 being removed and marking <NUM> being shown on proximal surface S1 within the bounds of indicator groove <NUM>. <FIG> is an anterior perspective view of resected tibia T of <FIG> showing proximal surface S1 including marking <NUM>. <FIG> shows tibia T in the same orientation as <FIG> but without tibial spacer paddle <NUM>.

Indicator groove <NUM> can align with the center of femur F, e.g. the center position between the medial and lateral condyles that is coincident with femur axis AF. However, tibia T can be offset from the orientation of femur F such that the center of tibia T coincident with tibia axis AT is not aligned with the center of femur F. Tibial spacer paddle <NUM> includes indicator groove <NUM> to allow a surgeon to visualize and mark the center of femur F relative to the rotational position of tibia T in order to prepare tibia T and femur F for implantation of prosthetic knee joint devices. An instrument or tool, such as a pen, Bovie, marker, scalpel or pick, can be inserted into indicator groove <NUM> at bearing surface 18A and pushed through indicator groove <NUM> to penetrate beyond bearing surface 18B to contact proximal surface S1 of tibia T.

Marking <NUM>, which can comprise a stripe of ink from a marker, a score in the surface of proximal surface S1 from a pick, or the like, can provide a fixed indicator on proximal surface S1 that points to where the center of femur F aligns on tibia T. As such, the center of a prosthetic tibial implant to be attached to proximal surface S1 of tibia T can be aligned with marking <NUM> upon implantation. Thus, for example, bearing surfaces of the prosthetic tibial implant configured to mate with condylar surfaces of a prosthetic femoral implant to be attached to femur F can be oriented so that tibia T will have the natural rotational orientation when in full extension. When properly aligned in extension, the prosthetic femoral and tibial components will not resist the natural orientation of the knee and joint pain and discomfort can be avoided.

Tibial spacer paddle <NUM> provides passive engagement with distal surface S2 of femur F. Tibial spacer paddle <NUM> is held in frictional engagement with femur F via feet 12A and 12B. Other embodiments of tibial spacer paddles can include features for providing positive engagement with femur F.

Using the above-described device and procedures, a method for determining rotation between a femur and a tibia can include the following steps: resect a femur and a tibia; position the tibia into approximately sixty degrees of flexion; insert a tibial spacer paddle into an anterior opening between resections of the tibia and femur; engage medial and lateral paddle feet with posterior surfaces of the femur so that the tibial spacer paddle is linked to the femur; extend the tibia into extension so the tibia rotates against the tibial spacer paddle; evaluate joint tension between the tibia and femur; insert tibial spacer paddles of different thicknesses into the anterior opening until a desired joint tension is achieved; making sure the medial and lateral paddle feet are engaged with posterior surface of femur, allow the tibia to rotate into a natural position against the tibial spacer paddle; identify a center of the femur at an indicator groove in the center of the tibial spacer paddle; and mark the center of the femur on the tibia using the indicator groove.

<FIG> is a perspective view of tibial spacer paddle <NUM> having alignment pegs 112A and 112B and indicator groove <NUM> disposed in spacer block <NUM>. <FIG> is a top view of tibial spacer paddle <NUM> of <FIG> showing a location for indicator groove <NUM> relative to bearing surface 118A. <FIG> are discussed concurrently. Alignment pegs 112A and 112B can be configured to provide positive engagement with a femoral prosthetic component attached to femur F.

Spacer block <NUM> can include first bearing surface 118A, second bearing surface 118B, edge periphery surface <NUM>, notch <NUM> and handle <NUM>. Spacer block <NUM> can have a thickness between bearing surface 118A and bearing surface 118B that can differ in different embodiments in order to trial the tension in the knee joint. Spacer block <NUM> can generally be thinner than spacer block <NUM> due to spacer block <NUM> being configured to mate with femoral component <NUM>. Edge periphery surface <NUM> can include edge chamfers 126A and 126B. Notch <NUM> and indicator groove <NUM> can extend into space block <NUM> to form first condylar portion 128A and second condylar portion 128B. Handle <NUM> can extend from edge periphery surface <NUM> of spacer block <NUM> and can include first segment 130A and second segment 130B. Second segment 130B can comprise an elongate body having a central axis A3 that is configured to extend axially in the direction of indicator groove <NUM>.

Tibial spacer paddle <NUM> is configured similarly as tibial spacer paddle <NUM> of <FIG> except feet 12A and 12B are replaced by alignment pegs 112A and 112B and chamfers 26A and 26B are replaced by edge chamfers 126A and 126B. Additionally, posterior surfaces 36A and 36B are replaced by proximal surfaces 136A and 136B. All other elements are numbered similarly as <NUM> series numbers.

Alignment pegs 112A and 112B can be configured to hold spacer block <NUM> into engagement with femoral implant <NUM> (<FIG>) attached to a resected femur. Proximal surfaces 136A and 136B can protrude or project from first bearing surface 118A so that pegs 112A and 112B are perpendicular to bearing surface 118A. However, in other examples, superior surfaces 136A and 136B can extend at other angles relative to bearing surface 118A for use with different femoral implants than the one shown in <FIG>. Thus, alignment pegs 112A and 112B can remain engaged with femoral component <NUM> as the knee joint is moved through flexion. If desired, a surgeon can grasp handle <NUM> to facilitate engagement of spacer block <NUM> and the femur. As the tibia moves from flexion to extension, the tibia can rotate against bearing surface 118B along vertical axis A4, as described in greater detail with reference to <FIG>.

<FIG> is a perspective view of tibial spacer paddle <NUM> of <FIG> and femoral component <NUM> engaged with alignment pegs 112A and 112B. Femoral component <NUM> can comprise a femoral trial component that has distal surfaces for engaging a tibial component and proximal surfaces for engaging a resected femur. A plurality of femoral components can be provided with each of the femoral components having different parameters, such as thicknesses, varus/valgus angles, etc., for trialing with the anatomy of a patient. Femoral component <NUM> can be held in place against femur F using bone cement, fasteners or by force fit with the resected surfaces.

Femoral component <NUM> can comprise tibia-facing surface <NUM> formed along the outer periphery of femoral component <NUM> and can include lateral condyle 144A and medial condyle 144B. Lateral condyle 144A and medial condyle 144B can be configured for articulation with a prosthetic tibial component. Femoral component <NUM> can include anterior flange <NUM> having trochlear groove <NUM>. Trochlear groove <NUM> can extend from a generally anterior and proximal starting point to a generally posterior and distal terminus. Trochlear groove <NUM> can form an anterior articular surface of femoral component <NUM> for articulation with a natural or prosthetic patella.

Femoral component <NUM> can define a transverse plane that can be a plane tangent to distal-most points of lateral and medial condyles 144A and 144B. Femoral component <NUM> can also define a coronal plane that can be a plane tangent to the posterior-most points of the lateral and medial condyles 144A and 144B, when viewed from a lateral side of femoral component <NUM>, can be perpendicular to the transverse plane.

Femoral component <NUM> can include peg ports 150A and 150B that can be configured to engage alignment pegs 112A and 112B, respectively. Peg ports 150A and 150B can be positioned in the transverse plane at the distal-most points of lateral and medial condyles 144A and 144B, respectively.

Femoral component <NUM> can comprise femur-contacting portion <NUM> formed along the inner periphery of femoral component <NUM> and can include distal surface <NUM>, first posterior surface 156A, second posterior surface 156B, angled anterior surface <NUM>, first quarter surface 160A and second quarter surface 160B. Distal surface <NUM>, first posterior surface 156A, second posterior surface 156B, angled anterior surface <NUM>, first quarter surface 160A and second quarter surface 160B can be configured to align and mate with distal surface S2, first posterior surface S3A, second posterior surface S3B, angled anterior surface S4, first quarter surface S5A and second quarter surface S5B, respectively, of tibia T in <FIG>.

<FIG> is a perspective view of femoral component <NUM> of <FIG> attached to resected femur F and tibial spacer paddle <NUM> of <FIG> inserted between femoral component <NUM> and resected tibia T in approximately sixty degrees of flexion.

With the knee joint in flexion, tibial spacer paddle <NUM> can be inserted into an incision in an anterior portion of a knee joint so that handle <NUM> can extend out of the incision. Second bearing surface 118B can be positioned against resected proximal surface S1. Femur F and tibia T of the knee joint can be pushed or pulled apart, such as by using a retractor, to provide space for tibial spacer paddle <NUM>. Edge chamfers 126A and 126B can facilitate insertion of tibial spacer paddle <NUM> by narrowing spacer block <NUM> and can eliminate sharp edges that could potentially interfere with or damage ligaments in the knee joint. Tibial spacer paddle <NUM> can be positioned so that alignment pegs 112A and 112B align with peg ports 150A and 150B, respectively, in femoral component <NUM>.

<FIG> is a side view of femoral component <NUM> and tibial spacer paddle <NUM> of <FIG> being moved toward full extension so that alignment pegs 112A and 112B align with and are inserted into corresponding peg ports 150A and 150B in femoral component <NUM>. As tibia T moves into extension, indicated by arrow E, handle <NUM> can be used by a surgeon to guide alignment pegs 112A and 112B into peg ports 150A and 150B. As pegs 112A and 112B engage femoral component <NUM>, proximal surface S1 of tibia T can slide against bearing surface 118B and tibia T undergoes natural rotation into extension.

<FIG> is a perspective view of femoral component <NUM> and tibial spacer paddle <NUM> of <FIG> in full extension with tibia T rotated into a natural alignment position so that resected proximal surface S1 can be marked at the indicator groove <NUM>. With bearing surface 118A flushly engaged with femoral component <NUM> and bearing surface 118B flushly engaged with proximal surface S1 of tibia T, tibia T is free to rotate against spacer block <NUM>, as shown by arrows of rotation R3 and R4. Pegs 112A and 112B hold tibial spacer paddle <NUM> in positive engagement with femoral component <NUM> at peg ports 150A and 150B. This engagement can reduce or eliminate slippage of tibial spacer paddle <NUM> relative to femur F, which can help provide an accurate indication of the natural rotational position of tibia T relative to femur F when in extension. Indicator groove <NUM> can be visible between lateral and medial condyles 144A and 144B of femoral component <NUM> for both visual inspection and insertion of a tool or instrument.

Marking <NUM>, which can comprise a stripe of ink from a marker, a score in the surface of proximal surface S1 from a pick, or the like, provides a fixed indicator on proximal surface S1 that points to where the center of femur F aligns on tibia T. As such, the center of a prosthetic tibial implant to be attached to proximal surface S1 of tibia T can be aligned with marking <NUM> upon implantation.

Using the above-described device and procedures, a method for determining rotation between a femur and a tibia can include the following steps: resect a femur and a tibia; position the tibia into approximately sixty degrees of flexion; attach a femoral component to the resected femur; insert a tibial spacer paddle into an anterior opening between resections of the tibia and femur; guide tibial spacer paddle pegs into corresponding ports in the femoral component to link the tibial spacer paddle and the femoral component; extend the tibia into extension so the tibia rotates against the tibial spacer paddle; evaluate joint tension between the tibia and femur; insert tibial spacer paddles of different thicknesses into the anterior opening until a desired joint tension is achieved; allow the tibia to rotate against the tibial spacer paddle into a natural position; identify a center of the femur at an indicator groove in the center of the tibial spacer paddle; and mark the center of the femur on the tibia using the indicator groove.

<FIG> is a perspective view of tibial sizing system <NUM> according to the invention comprising provisional component <NUM> and sizing plate <NUM> aligned for insertion onto resected tibia T. Provisional component <NUM> includes condyle bearing surfaces (or articulating surfaces) 216A and 216B, an opposing engagement (bearing) surface <NUM>, socket <NUM> and engagement tab <NUM>. Engagement tab <NUM> can include body <NUM> and notch <NUM>. Sizing plate <NUM> comprises bone-facing (bone-engaging) surface <NUM>, engagement surface <NUM>, socket <NUM> and etch lines 234A and 234B. Sizing plate <NUM> is discussed further with reference to <FIG>. In examples, provisional component <NUM> can comprise a one-piece Tibial Articular Surface Provisional (TASP), commercially available from Zimmer Biomet under the Persona brand, modified to include engagement tab <NUM>. In examples, sizing plate <NUM> can comprise a tibial sizing plate as described in <CIT>, modified to include etch lines 234A and 234B.

<FIG> also shows femoral component <NUM> attached to resected femur F. Femoral component <NUM> can be similar to that of femoral component <NUM> of <FIG>, except for the addition of pin port <NUM>. All other elements are numbered similarly as <NUM> series numbers. For example, femoral component <NUM> can comprise tibia-facing surface <NUM> formed along the outer periphery of femoral component <NUM>, which can include lateral condyle 244A and medial condyle 244B, anterior flange <NUM> having trochlear groove <NUM>, and femur-contacting portion <NUM> formed along the inner periphery of femoral component <NUM>, which can include distal surface <NUM>, first posterior surface 256A, second posterior surface 256B, angled anterior surface <NUM>, first quarter surface 260A and second quarter surface 260B.

Femoral component <NUM> can also include pin bore <NUM> for the reception of pin <NUM>. Pin <NUM>, such as a trocar pin, can be inserted into pin bore <NUM>. Pin bore <NUM> can be positioned to align with engagement tab <NUM> when the centers of femoral component <NUM> and provisional component <NUM> are aligned.

Femoral component <NUM> can be attached to femur F in any suitable manner, as described above. Likewise, provisional component <NUM> can be attached to sizing plate <NUM> in a releasable manner. For example, provisional component <NUM> can be snap fit into sizing plate <NUM>, as described below. Sizing plate <NUM> is configured to slide against proximal surface S1 of tibia T. Because femoral components <NUM> and tibial provisional component <NUM> can be configured as trialing components, femoral components <NUM> and provisional component <NUM> can be removably attached to the respective surfaces.

In <FIG>, tibia T and femur F can be resected to have surfaces as described with reference to <FIG>. Femoral component <NUM> can be attached to femur F and then tibial sizing system <NUM> can be inserted, as indicated by arrow I1, between femoral component <NUM> and resected proximal surface S1 of tibia T.

<FIG> is perspective view of femoral component <NUM> and tibial sizing system <NUM> of <FIG> with tibial sizing system <NUM> inserted between femoral component <NUM> and resected tibia T in extension. As shown, both pin bore <NUM> and engagement tab <NUM> are positioned on the same side of femoral component <NUM> and tibial sizing system <NUM>, respectively. As tibia T is moved into full extension, tibial sizing system <NUM> can be positioned so that notch <NUM> can align with pin <NUM>, as proximal surface S1 of tibia T rotates against bone-facing surface <NUM> of sizing plate <NUM>. With pin <NUM> engaged with notch <NUM>, provisional component <NUM> can be swapped out for provisional components of similar construction, but with different thicknesses. For example, the thickness between bearing surfaces 216A and 216B and engagement surface <NUM> can be different in different embodiments of sizing plates <NUM>. The different thicknesses can be used to set the desired ligament tension between tibia T and femur F.

<FIG> is perspective view of femoral component <NUM> and tibial sizing system <NUM> of <FIG> with femur F in full extension and tibia T rotated so pin <NUM> extending into femoral component <NUM> aligns with tab <NUM> on tibial provisional component <NUM>. Once the desired tension is set, tibia T and femur F can be set into extension so that pin <NUM> aligns with notch <NUM>. Tibia T can find a natural rotational position in extension with respect to femur F, as shown by arrows of rotation R5 and R6. For example, proximal surface S1 of tibia T can rotate against bone-facing surface <NUM> of sizing plate <NUM>.

<FIG> is a perspective view of femoral component <NUM> and tibial sizing system <NUM> of <FIG> with pin <NUM> extending along tab <NUM> and alignment markings 266A and 266B on the tibia T. Etch lines 234A and 234B can be positioned along tibia T adjacent proximal surface S1. Markings 266A and 266B, which can comprise a stripe of ink from a pen, a Bovie, a marker, a score in the surface of proximal surface S1 from a pick, or the like, provides a fixed indicator on proximal surface S1 that points to where the center of femur F and a secondary reference point align on tibia T. For example, marking 266B can indicate the center of femur F and marking 266A can be used to verify rotation of tibia T and provide a secondary reference point. As such, the center of a prosthetic tibial implant to be attached to proximal surface S1 of tibia T can be aligned with marking 266B upon implantation and a secondary mark corresponding to etch line 234B on the prosthetic tibial implant can be aligned with marking 266A.

<FIG> is a perspective view of resected tibia T of <FIG> showing sizing plate <NUM> of the tibial sizing system <NUM> disposed on the resected tibia surface T. Sizing plate <NUM> can include wall <NUM>, keel socket <NUM> and fixation bores <NUM>. Fixation bores <NUM> can comprise openings in engagement surface <NUM> into which fasteners can be inserted to retain sizing plate <NUM> against proximal surface S1 of tibia T. Keel socket <NUM> can comprise an opening in engagement surface <NUM> into which a fixation feature, such as a keel, of a prosthetic tibial component can be inserted. Wall <NUM> can comprise a flange extending from engagement surface <NUM> that can function to retain provisional component <NUM>. For example, provisional component <NUM> can include corresponding features (e.g., cutback <NUM> and cutback <NUM> of <FIG>) that allow provisional component <NUM> to be snap fit into wall <NUM>. Etch lines 234A and 234B and markings 266A and 266B can be used to orient keel socket <NUM> relative to proximal surface S1 to provide rotational orientation of the prosthetic tibial component relative to the mechanical axis (e.g., vertical axis A2 of <FIG> or tibial axis AT of <FIG>) of tibia T. Further description of sizing plate <NUM> can be found in the aforementioned '<NUM> patent to Houston et al.

Using the above-described device and procedures, a method for determining rotation between a femur and a tibia can include the following steps: resect a femur and a tibia; position the tibia into approximately sixty degrees of flexion; attach a femoral component to the resected femur; insert a pin into the femoral component; connect a tibial sizing plate to tibial provisional component; insert the connected tibial sizing plate and tibial provisional component into an anterior opening between resections of the tibia and femur; extend the tibia into extension so the tibia rotates against the tibial sizing plate; guide the pin into a notch in the tibial provisional component to link the tibial provisional component and the femoral component; evaluate joint tension between the tibia and femur; connect tibial provisional components of different thicknesses to the tibial sizing plate until a desired joint tension is achieved; allow the tibia to rotate against the tibial sizing plate into a natural position; identify a center of the femur at an indicator in the center of the tibial sizing plate; and mark the center of the femur on the tibia using the indicator.

<FIG> is a perspective view of another embodiment of tibial sizing system <NUM>' of <FIG>, which is also according to the invention, wherein provisional component <NUM>' and sizing plate <NUM>' are integrated into monolithic component <NUM>. Monolithic component <NUM> can function the same as the combination of provisional component <NUM> and sizing plate <NUM>, except for being a single, unitary component. Thus, a plurality of monolithic components <NUM> can be provided with different thicknesses in order to trial the desired ligament tension between tibia T and femur F. Certain features can be eliminated from tibial sizing system <NUM>' for simplicity, such as socket <NUM>. Additionally, engagement surface <NUM> and engagement surface <NUM> can be eliminated because monolithic component <NUM> is fused along this planar intersection as compared to tibial sizing system <NUM>.

Using the above-described device and procedures, a method for determining rotation between a femur and a tibia can include the following steps: resect a femur and a tibia; position the tibia into approximately sixty degrees of flexion; attach a femoral component to the resected femur; insert a pin into the femoral component; insert a tibial provisional component into an anterior opening between resections of the tibia and femur; extend the tibia into extension so the tibia rotates against the tibial provisional component; guide the pin into a notch in the tibial provisional component to link the tibial provisional component and the femoral component; evaluate joint tension between the tibia and femur; insert tibial provisional components of different thicknesses into the anterior opening until a desired joint tension is achieved; allow the tibia to rotate against the tibial provisional component into a natural position; identify a center of the femur at an indicator in the center of the tibial provisional component; and mark the center of the femur on the tibia using the indicator.

<FIG> is a perspective view of femoral component <NUM> attached to resected femur F and tibial sizing system <NUM> comprising provisional component <NUM> and tibial plate <NUM> with pivot mount <NUM> (<FIG>) inserted between femoral component <NUM> and resected tibia T. Provisional component <NUM> can include pivot port <NUM> (<FIG>) that can receive pivot mount <NUM> such that provisional component <NUM> can rotate or pivot relative to tibial plate <NUM>.

Femur F and tibia T can be resected as described herein. Femoral component <NUM> can be configured the same as femoral component <NUM> of <FIG> to include pin bore <NUM> for the reception of pin <NUM>. Provisional component <NUM> can be similar to that of provisional component <NUM> of <FIG>, except for the addition of pivot port <NUM> and etch lines 278A and 278B. All other elements are numbered the same.

As mentioned, pivot port <NUM> and pivot mount <NUM> can connect in a rotational engagement. Tibial plate <NUM> can engage tibia T in a free manner and provisional component <NUM> can slide against tibial plate <NUM> to facilitate determination of the natural rotation of tibia T.

<FIG> is a perspective view of tibial plate <NUM> with pivot mount <NUM> of <FIG> that can be configured to extend from bearing surface <NUM>. Additionally, tibial plate <NUM> can include bone-facing (bone-engaging) surface <NUM> and edge periphery region <NUM>, which can connect bearing surface <NUM> and bone-facing surface <NUM>. Pivot mount <NUM> can comprise a cylindrical peg extending perpendicularly from bearing surface <NUM>. Bearing surface <NUM> can have a smooth finish to reduce frictional engagement with engagement surface <NUM>. For example, tibial plate <NUM> can be finished, such as via a polishing operation, to reduce the coefficient of friction of bearing surface <NUM>.

<FIG> is a top perspective view of provisional component <NUM> of <FIG> showing the construction of engagement tab <NUM> and socket <NUM>. Engagement tab <NUM> can include body <NUM> and notch <NUM>. Socket <NUM> can include bores 284A and 284B and through-port <NUM>.

Notch <NUM> can include bottom portion <NUM> and sidewalls 282A and 282B. Notch <NUM> can be configured to receive a pin, rod or other member extending form femoral component <NUM>, such as pin <NUM>. For example, bottom portion <NUM> can form a semicircular wall. Pin <NUM> can be cylindrical and bottom portion <NUM> can be configured to have a matching diameter to flushly receive pin <NUM>. Sidewalls 282A and 282B can extend from bottom portion <NUM> upward away from the remainder of body <NUM> and the distance between sidewalls 282A and 282B can increase as sidewalls 282A and 282B extend further away from bottom portion <NUM>. In other words, portions of body <NUM> forming sidewalls 282A and 282B can taper as sidewalls 282A and 282B extend away from bottom portion <NUM>. As such, the wider portion of notch <NUM> in the proximal direction can guide pin <NUM> into engagement with bottom portion <NUM> as tibia T is moved into full extension.

Socket <NUM> can be configured to receive a tool to facilitate insertion and removal of provisional component <NUM>. In examples, bores 284A and 284B can be configured to receive pins of a tibial insertion handle. Through-port <NUM> can thereafter be configured to receive a tooth of a spring-loaded slide on the handle that locks the handle to provisional component <NUM>. In examples, socket <NUM> can be configured to operate with the pins and the tooth described in <CIT>.

<FIG> is a bottom perspective view of provisional component <NUM> of <FIG> showing engagement surface <NUM>, pivot port <NUM>, anterior cutback <NUM> and posterior cutback <NUM>. Engagement surface (or bearing surface) <NUM> can be smooth to slide against bearing surface <NUM>. Pivot port <NUM> can be located in engagement surface <NUM> and can be positioned to align with pivot mount <NUM>. Pivot port <NUM> can comprise a cylindrical bore to receive pivot mount <NUM>. Anterior cutback <NUM> and posterior cutback <NUM> can be recesses into engagement surface <NUM> that extend all the way to edge periphery surface <NUM>. Edge periphery surface <NUM> connects engagement surface <NUM> and condyle bearing surfaces 216A and 216B. Edge periphery surface <NUM> can also include etch lines 278A and 278B. Anterior cutback <NUM> and posterior cutback <NUM> can be configured to engage wall <NUM> of sizing plate <NUM> (<FIG>) to assist in retaining provisional component <NUM> in engagement with sizing plate <NUM>. Additionally, anterior cutback <NUM> and posterior cutback <NUM> can allow engagement surface <NUM> to sit down into wall <NUM>.

<FIG> is a perspective view of femoral component <NUM> of <FIG> attached to resected femur F and tibial sizing system <NUM> in accordance with the invention exploded from resected tibia T. As shown by arrow C1, tibial plate <NUM> can be connected to provisional component <NUM> by inserting pivot mount <NUM> into pivot port <NUM> (<FIG>) to form assembled tibial sizing system <NUM>. A biocompatible lubricant can be positioned between tibial plate <NUM> and provisional component <NUM> to facilitate relative rotation therebetween. As shown by arrow C2, the assembled tibial sizing system <NUM> can be inserted into a knee joint between tibia T and femur F so that surface <NUM> faces proximal surface S1 of tibia T. As such, bearing surfaces 216A and 216B can face toward femoral component <NUM>. Different provisional components <NUM> of different thicknesses can be trialed between tibia T and femur F to find the proper tension.

<FIG> is a perspective view of assembled tibial sizing system <NUM> of <FIG> inserted between femoral component <NUM> and resected tibia T. Pin <NUM> can be inserted into pin bore <NUM> in femoral component <NUM>. With pin <NUM> engaged with engagement tab <NUM> to lock relative rotation between femoral component <NUM> and provisional component <NUM>, tibia T can rotate into natural alignment, as shown by arrows of rotation R7 and R8, as proximal surface S1 rotates against surface <NUM>. Attachment of tibial plate <NUM> to provisional component <NUM> via pivot mount <NUM> allows tibial plate <NUM> to rotate with tibia T while sliding against proximal surface S1 to provide a better indication of the natural rotational position of tibia T relative to femur F when in extension. For example, tibia T can be less encumbered by resistance from tibial sizing system <NUM> to facilitate true rotation of tibia T.

<FIG> is a perspective view of tibia T of <FIG> in full extension so that pin <NUM> is fully seated in engagement tab <NUM> and resected tibia T is marked with alignment markings 310A and 310B. As with markings 266A and 266B, markings 310A and 310B can provide reference marks for aligning with features of a prosthetic tibial component that provide rotational alignment of the prosthetic tibial component so that the prosthetic tibial component will not stress the knee joint when in extension, e.g., tibia T will find its natural rotational position without pushback from the prosthetic tibial component against a prosthetic femoral component. In various examples, tibial plate <NUM> can include cutouts or windows (not shown) that permit proximal surface S1 to be viewed through tibial plate <NUM>.

Using the above-described device and procedures, a method for determining rotation between a femur and a tibia can include the following steps: resect a femur and a tibia; position the tibia into approximately sixty degrees of flexion; attach a femoral component to the resected femur; insert a pin into the femoral component; connect a tibial plate to tibial provisional component at a pivot coupling; insert the coupled tibial plate and tibial provisional component into an anterior opening between resections of the tibia and femur; extend the tibia into extension so the tibia rotates against the tibial plate; guide the pin into a notch in the tibial provisional component to link the tibial provisional component and the femoral component; evaluate joint tension between the tibia and femur; connect tibial provisional components of different thicknesses to the tibial plate until a desired joint tension is achieved; allow the tibia to rotate against the tibial plate into a natural position while the tibial plate rotates against the tibial provisional component; identify a center of the femur at an indicator in the center of the tibial provisional component; and mark the center of the femur on the tibia using the indicator.

<FIG> is a top perspective view of another example of provisional component <NUM> of <FIG>, but without alignment tab <NUM> and therefore not in accordance with the invention. <FIG> is a bottom perspective view of the embodiment of provisional component <NUM> of <FIG>. Alignment tab <NUM> can be omitted to simplify the construction of provisional component <NUM> and to simplify the method of trialing the tibial component. In some circumstances, it may be sufficient to determine the natural rotational position of tibia T without preventing relative rotation between femoral component <NUM> and provisional component <NUM>. For example, the frictional engagement between lateral condyle 244A and medial condyle 244B with bearing surface 216A and bearing surface 216B, respectively, may be sufficient to immobilize provisional component <NUM>. In examples, bearing surfaces 216A and 216B can be provided with texturing, such as knurling, pyramids, spikes or other projections to facilitate linked rotation.

Using the above-described device and procedures, a method for determining rotation between a femur and a tibia can include the following steps: resect a femur and a tibia; position the tibia into approximately sixty degrees of flexion; attach a femoral component to the resected femur; connect a tibial plate to tibial provisional component at a pivot coupling; insert the coupled tibial plate and tibial provisional component into an anterior opening between resections of the tibia and femur; extend the tibia into extension so the tibia rotates against the tibial plate; evaluate joint tension between the tibia and femur; connect tibial provisional components of different thicknesses to the tibial plate until a desired joint tension is achieved; allow the tibia to rotate against the tibial plate into a natural position while the tibial plate rotates against the tibial provisional component; identify a center of the femur at an indicator in the center of the tibial provisional component; and mark the center of the femur on the tibia using the indicator.

Claim 1:
A tibial spacer system comprising:
a provisional component (<NUM>, <NUM>') comprising:
a body;
an articulating surface (216A, 216B) positioned on the body configured to engage condylar surfaces of a femoral component;
a first bearing surface disposed opposite the articulating surface;
a first edge periphery region connecting the articulating surface and the first bearing surface; and
a sizing extension (<NUM>) extending from the body opposite the articulating surface, the sizing extension comprising:
a bone engagement surface (<NUM>);
an edge periphery region extending from the bone engagement surface; and
a first alignment indicator (234B, 234B', 278A) located on the edge periphery region of the sizing extension, characterised in that an alignment tab (<NUM>) extends from the first edge periphery region of the body.