NAVIO Surgical System Surgical Technique for Unicondylar Knee Replacement and Patellofemoral Arthroplasty Rev D Sept 2018

Contents Introduction...1 Overview...2 Patient and System Setup...3 Bone Tracking Hardware...6 Registration – UKR...8 Implant Planning – UKR...13 Bone Cutting – UKR...21 Trial Reduction – UKR...29 Registration – PFA...30 Implant Planning – PFA...32 Bone Cutting – PFA...34 Trial Reduction – PFA...39 Cement and Close...39 Recovery Procedure Guidelines...40

The following technique is for informational and educational purposes only. It is not intended to serve as medical advice. It is the responsibility of treating physicians to determine and utilize the appropriate products and techniques according to their own clinical judgment for each of their patients. For more information on the NAVIO™ Surgical System, including its indications for use, contraindications, and product safety information; please refer to the product’s label and the Instructions for Use packaged with the product.

Introduction This guide provides an overview of the recommended surgical technique for using the NAVIO™ Surgical System with the following supported implants: • JOURNEY™ UNI Unicompartmental Knee System (Figure 1) • ACCURIS™ Uni Knee System • STRIDE™ Unicondylar Knee System • DePuy Synthes SIGMA® High Performance Partial Knee System – UNI • ZUK™ Knee System • DJO Surgical EPIK® Knee System • StelKast Unicondylar Knee System • JOURNEY™ PFJ Patellofemoral Joint System (Figure 2) • DePuy Synthes SIGMA® High Performance Partial Knee System – PFJ

Figure 1. JOURNEY UNI Unicompartmental Knee System.

Smith & Nephew recommends that you review this guide prior to performing unicondylar knee replacement or patellofemoral arthroplasty utilizing the NAVIO Surgical System. This guide should be used in conjunction with, not replacing, the information contained within the User’s Manual that accompanied the purchase of the NAVIO Surgical System, and the Surgical Technique document that accompanied the purchase of the applicable implant. NOTE: Screenshots used in this guide are examples used for reference only. Actual screens may vary. WARNING The NAVIO™ Surgical System is a surgical tool designed to provide assistance to the surgeon; it is not a substitute for the surgeon’s experience and skill. The surgeon retains all responsibility for the planning and the conduct of the surgery during which the NAVIO™ Surgical System is being used

Intended Use The NAVIO Surgical System is intended to assist the surgeon in providing software-defined spatial boundaries for orientation and reference information to anatomical structures during orthopedic procedures.

Figure 2. JOURNEY PFJ Patellofemoral Joint System (3 views).

Indications for Use The NAVIO Surgical System is indicated for use in surgical knee procedures, in which the use of stereotactic surgery may be appropriate, and where reference to rigid anatomical bony structures can be determined. These procedures include unicondylar knee replacement (UKR), patellofemoral arthroplasty (PFA), and total knee arthroplasty (TKA). The NAVIO Surgical System is indicated for use with cemented implants only.

Contraindications The NAVIO Surgical System is not intended to be used on children, pregnant women, patients who have mental or neuromuscular disorders that do not allow control of the knee joint, morbidly obese patents, or any other patients contraindicated for unicondylar knee replacement, patellofemoral arthroplasty, or total knee arthroplasty. Consult the applicable implant labeling for its full intended use, indications and contraindications. WARNING: Please reference the implant manufacturer’s instructions for use and recommendations for the compatibility of implant system combinations. 1

Overview NAVIO™ Surgical System The NAVIO Surgical System is a surgical planning, navigation and intraoperative visualization system combined with a handheld smart instrument for bone sculpting. The camera cart communicates the relative position of the handpiece, the femur, and the tibia (via rigid tracker arrays) to the computer cart (Figure 3). The patient’s bone is prepared according to an intraoperative plan that combines soft-tissue balancing and collected anatomic information with controlled bone removal and predictable long-leg alignment. The NAVIO Surgical System’s UKR and PFA applications can be separated into the following stages: 1.

Figure 3. Computer cart nested with camera cart (left); Handpiece (right).

Patient and System Setup

2. Bone Tracking Hardware

Small Parts Sterilization Case

3. Registration (UKR/PFA)

Handpiece Tracker Array Handpiece

Femur Tracker Array

4. Implant Planning (UKR/PFA) 5. Bone Cutting (UKR/PFA) 6. Trial Reduction (UKR/PFA) 7.

Cement and Close

This surgical technique guide is separated into the same stages for clarity.

NAVIO Instrument Kit

Fomon Rasp

The NAVIO instrument kit (Figure 4) consists of a two-level tray that contains all of the required instrumentation for surgery using the NAVIO Surgical System.

Point Probe Long Attachment

Tibia Tracker Array Tracker Array Clamps (2)

Guards

NOTE: If the equipment breaks or fails during surgery, a sterile backup kit is on-site and can be unwrapped to replace a broken or dropped instrument.

T-Handle Wrench

Z Knee Retractor

Figure 4. Instrument kit.

2

Tissue Protector Anspach® eMAX® 2 Plus Handpiece

Bone Screw Driver

Patient and System Setup Patient Setup •• Avoid wrapping the ankle with bulky drapes or

coverings. Using bulky material in this area may make it difficult to locate the malleoli points during patient registration.

•• Use a leg positioner, like the IMP® De Mayo Knee

Positioner®, to elevate the femur to approximately 45° and flex the knee to approximately 90° (Figure 5).

•• If possible, remove the pad on the operative leg side

to allow the positioner to sit below hip-level. This will help to provide natural kinematics during positioning and flexion.

Figure 5. Initial leg setup.

System Draping and Positioning (Figure 6, 7) •• Apply the sterile drape to the monitor by following

the included Monitor Drape Instructions for Use. An additional drape may be used to cover the computer cart below the monitor drape.

•• Position the computer cart so that the surgeon can

clearly see and easily operate the graphical user interface at all times. The computer cart should be positioned on the opposite side of the leg to be operated. Rotate the monitor to cantilever over the patient, aimed diagonally at the surgeon’s line of sight.

•• The camera cart should also be placed on the

opposite side of the leg to be operated, with the camera approximately 1.5 m from the surgical site and 1.6 to 1.9 m high.

•• Use the laser pointer integrated into the faceplate

of the camera head to direct the laser beam at the knee joint to be operated.

•• Except during determination of the hip center, the

camera cart positioning may be adjusted at any point during the operation to meet the needs of the surgeon.

•• Guidance for camera positioning is provided in the

Figure 6. Monitor drape application.

Camera Orientation Adjustment stage of the NAVIO™ Surgical System’s UKR and PFA applications.

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System and Tool Preparation Refer to the NAVIO™ Surgical System User’s Manual for instructions on proper NAVIO handpiece assembly. The configurations found to be most conducive to bone removal and post hole/keel preparation for various NAVIO Surgical System supported implants are listed below: Implant

Bur

JOURNEY™ UNI

• 6 mm Spherical Bur • 5 mm Spherical Bur (post hole)

ACCURIS™

• 6 mm Spherical Bur • 5 mm Spherical Bur (femur post hole) • 6 mm Spherical Bur (tibia post hole)

STRIDE™

computer cart

monitor

camera cart

Left Knee OR Setup

• 6 mm Spherical Bur monitor

• 5 mm Spherical Bur SIGMA® – UNI • 5 mm Spherical Bur (tibia post hole) • 2 mm Spherical Bur (tibia keel) ZUK™

• 6 mm Spherical Bur • 6 mm Spherical Bur (post hole) • 2 mm Spherical Bur (keel)

EPIK®

• 5 mm Spherical Bur • 5 mm Spherical Bur (post hole) • 2 mm Spherical Bur (keel)

StelKast

• 5 mm Spherical Bur • 5 mm Spherical Bur (post hole) • 2 mm Spherical Bur (keel)

JOURNEY™ PFJ

• 6 mm Spherical Bur • 3 mm Spherical Bur (post hole)

SIGMA® – PFJ

• 5 mm Spherical Bur • 3 mm Spherical Bur (post hole)

computer cart camera cart

Right Knee OR Setup

Figure 7. Typical operating room (OR) setups.

The integrated irrigation system will administer continuous irrigation throughout bone removal.

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Exposure •• For exposure recommendations specified by the

implant system manufacturer, please consult their instructions for use and product documentation.

•• Upon making the incision, carefully debride

and inspect the joint. If any prominent spurs or osteophytes are present, especially in the area of the superior posterior femoral condyle, remove them with an osteotome or rongeur, as they could inhibit the leg motion.

•• With medial compartment disease, osteophytes are

typically found on the lateral aspect of the medial tibial eminence and anterior to the origin of the anterior cruciate ligament (ACL).

•• Remove the intracondylar osteophytes to avoid

impingement with the tibial spine or cruciate ligament; also remove the peripheral osteophytes that interfere with the collateral ligaments and capsule. In order to reliably assess mediolateral (ML) alignment and joint stability, it is crucial that all osteophytes are removed from the entire medial edges of the femur and tibia.

•• Resect the deep meniscotibial layer of the medial

capsule to provide access to any tibial osteophytes. Exposure also can be improved with excision of patellar osteophytes.

•• Avoid release of the collateral ligament. •• With the patient in the supine position, ensure the

knee is able to achieve 120° of flexion. A larger incision may be necessary to create sufficient exposure.

•• While cutting the bone near the collateral ligament,

insert a retractor between the tibia and the collateral ligament to protect the ligament from damage.

•• Final debridement will be performed before

component implantation.

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Bone Tracking Hardware Placing Tracking Hardware The NAVIO™ Surgical System utilizes a two-pin bicortical fixation system, comprised of the tools pictured in Figure 8. These tools allow for the tracking arrays (Figure 9) to be fixed to the bone and for the tracking markers to be oriented towards the optical tracking camera. With the operative leg in 90° of flexion, utilize the following procedure. WARNING: For bicompartmental surgery: If you intend to place both a patellofemoral prosthesis and a unicondylar prosthesis, ensure that the placement of the femoral bone hardware is far enough proximally on the femur, so as not to interfere with the camera’s visibility of the handpiece during either procedure. Figure 8. Hardware (from left: bone pins, tissue protector, tracker array clamp).

Femur Tracker Array Placement 1. Percutaneously place the first bone pin one hand’s breadth (four fingers) superior to the patella in the center of the femur (Figure 10), leaving room for the handpiece tracker to be fully visible to the camera during preparation of the femur. 2. Slowly drill the bone pin into the femur, perpendicular to the bony surface, taking care to engage the opposing cortex and stop. 3. Utilize the tissue protector to mark the position of the second bone pin inferior to the initial placement. Engage the second pin with the bone through the tissue protector to ensure the pins are placed parallel to each other. 4. Slide the tracker array clamp (with the clamp hardware oriented towards the camera) over the two bone pins until the bottom of the clamp is within 1 cm of the patient’s skin. Take care not to place the clamp touching the skin.

Figure 9. Bone tracking arrays: Femur (top) and tibia (bottom). Keep the smaller end of the array toward the operative site.

5. Clamp the tracker array into the tracker array clamp along the length of the bar on the array. Place the smaller side of the tracker array closest to the operative site. Orient the markers towards the camera and slide the array away from the incision site. 6. Use the T-handle wrench to tighten the screw on the top of the tracker array clamp to secure the assembly. Be sure to confirm the array visibility on the Camera Orientation Adjustment screen before tightening the assembly.

Figure 10. Femur and tibia tracking array positions. 6

Tibia Tracker Array Placement (not applicable for PFA)

1. Percutaneously place the first bone pin one hand’s breadth (four fingers) inferior to the tibial tubercle on the medial side of the tibial crest (Figure 10). 2. Slowly drill the bone pin into the tibia, perpendicular to the bony surface, taking care to engage the opposing cortex and stop. 3. Refer to steps 3 through 6 of the Femur Tracker Array Placement section in this guide.

Confirm Array Visibility Confirm that the position of the camera cart and tracker arrays allow for full, uninterrupted visibility throughout the registration and cutting processes using the Camera Orientation Adjustment screen (Figure 11).

near-to-far range

•• Confirm visibility of the Femur (F) and Tibia (T) tracker

arrays in the following three positions:

field of view area

1. With the leg in deep flexion, ensure that the (F) is visible in the camera’s field of view. 2. With the leg in approximately 20° of flexion, ensure that the (F) is visible while rotating the leg at the hip. Figure 11. Tracker array visibility.

3. With the leg in full extension, ensure that the (T) is visible in the camera’s field of view. Both (F) and (T) icons should be located in the lower third in the field of view area, and in the farther right third of the near-to-far range. NOTE: The tibia tracker array is not applicable for PFA.

Checkpoint Verification Pins •• Checkpoint verification pins (Figure 12) should be

placed in both the femur and the tibia (if applicable), in positions where they will not be disturbed during bone removal. These points are referenced using the point probe at defined stages throughout the procedure to determine if either tracker array has moved. WARNING: Ensure that the checkpoint verification pins are placed away from the bone to be removed to avoid cutting through or dislocating the checkpoint verification pins. Figure 12. Checkpoint definition.

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Registration – UKR NOTE: If performing a PFA procedure, please proceed to the Registration – PFA section in this guide.

CT-free Registration The NAVIO™ Surgical System’s CT-free registration process for UKR utilizes standard image-free principles to construct a virtual representation of a patient’s anatomy and kinematics.

Ankle Center •• Using the point probe, input the locations of the

medial and lateral malleoli points (Figure 13). Ensure that the point probe is visible throughout the point collection. If the probe is not visible, check that the tracking markers on the point probe array are not overlapping (in front, or behind) the tracking markers on the tibia tracker array.

Figure 13. Collect the medial and lateral malleoli points to calculate the ankle center.

Hip Center The Hip Center Calculation stage will follow the femoral tracker array, and is collected through circular movements at the hip. These circular movements should be unrestricted and unhindered by holding or fixing equipment. Avoid pelvic movement, which can be a source of error. •• Prior to beginning collection, the femur should

start at approximately 20° of hip flexion, in order to provide enough room to rotate the hip.

•• Slowly rotate the leg at the hip until all sectors of the

Figure 14. Rotate the leg at the hip to collect the hip center.

graphic have changed to green (Figure 14).

NOTE: Stay as close as possible to the center when collecting these sectors. •• There should be no transmission of force from the

femur onto the pelvis. Avoid a hip flexion angle greater than 45°.

Femur Kinematics •• Place the leg in full extension, applying slight axial

pressure to both compartments and collect the neutral position (Figure 15). Support the leg below the knee with one hand to avoid hyper-extension. This position will be utilized when calculating the patient’s preoperative varus/valgus deformity.

Figure 15. Collect the leg in full extension.

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•• The next step will record normal flexion motion and

calculate the femoral kinematic rotational axis. Slowly move the leg through a normal (unstressed) rangeof-motion to maximum flexion (Figure 16). Flex and extend the leg until all of the green bars read fully green (100%).

Ligament Tension •• Apply constant stress to the operative ligament (e.g.

valgus stress to the medial collateral ligament, MCL, when performing a medial UKR procedure) and collect the data throughout flexion. Input can either be continuous (Figure 17) which requires constant application of stress throughout flexion, or in discrete poses (Figure 18) which some users find easier to stabilize a flexion position and record the ligament stress.

Figure 16. Input the femoral kinematic axis.

This data is collected for use during the Gap Planning stage. You want to identify how much room the ligaments have. This will inform how much gap (laxity) will be built into the joint balance. NOTE: Do not over-tension ligaments and force alignment into the unresurfaced compartment of the knee. Varus knees should be kept in slight varus, and valgus knees in slight valgus. Avoid correcting beyond neutral. Figure 17. Stressed ROM (range of motion) Collection screen with continuous input.

Figure 18. Stressed ROM Collection screen with discrete position input.

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Femur Landmarks – UKR There are four femoral landmark points to collect for UKR (Figure 19). These points are to be used as visual references during Implant Planning. Using the point probe, collect the following: •• Tidemark Point

The Tidemark point is the expected anterior termination of the femoral implant component. This point can be identified with the leg in full extension, referencing where the anterior tibia meets the femoral condyle. •• Knee Center

Collect the center of the knee, which will be referenced as part of the HKA (hip-knee-ankle) weight bearing axis. This point is typically found in the trochlear groove, anterior to the posterior cruciate ligament attachment.

Figure 19. Femur landmark point collection for UKR.

•• Most Distal Point

Place the probe on the most distal part of the femoral condyle, centered mediolaterally. During Implant Planning, the software will use the most distal point to center the initial implant placement. •• Most Posterior Point

Hyper-flex the leg to access the most posterior point on the femoral condyle, marking the inflection point as the condyle curves posterior. The software will use the Tidemark and most posterior points to present an initial implant component size.

Femoral Surface Mapping The Femur Free Collection stage (Figure 20) offers a visualization of the previously collected femoral mechanical axis and rotational axis (blue lines), as well as the discrete femur landmark points (yellow dots). •• Digitize the femoral condyle by moving the point

probe over the entire surface, while holding down the footpedal. Use both hands to ensure constant contact of the point probe with the bone surface. Start by outlining the surface you want to digitize, then fill in the entire surface.

•• You must input enough information into the system

to appropriately localize the implant during planning.

Figure 20. The software presents a virtual representation of the bone surface, generated from the collected free points. Manipulate the visualization to view in 3D.

•• Hyperflex the leg to map the posterior portion.

Manipulate the touchscreen to view the collected virtual bone surface in 3D (three dimensions).

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Tibial Condyle There are six tibial landmark points to collect (Figure 21). These points will be used as a visual reference during Implant Planning. Using the point probe, collect the following: •• Knee Center

Collect the tibial knee center at the origin of the ACL. •• Low Point

Collect the singular low-point of cartilage wear on the tibial plateau. This point will be used to calculate the ‘resection depth’ during the Implant Planning stage. •• Most Posterior Point

Figure 21. Tibial landmark point collection.

This is the most challenging point to reliably capture. Attempt to access the posterior of the tibial condyle by flexing the leg, externally rotating the tibia and manually distracting the joint. Alternatively, pushing the point probe down the tibial spine and feeling for tactile feedback of the posterior end of the condyle has been effective in some cases. •• Most Anterior Point

Collect the most anterior point on the tibial condyle. This point will be referenced to place the anterior position of the tibial implant component during the Implant Planning stage. •• Most Medial (or Lateral) Point

Collect the most medial (or lateral) point on the tibial condyle that can be referenced to size the ML aspect of the component during the Implant Planning stage. Ensure that the point is referenced on the bony side of the collateral ligament. •• Intercondylar Eminence Ridge

While all of the other collections listed above are singular points marked by the tip of the point probe, this collection will reference the axis of the point probe. Lay the probe approximately half-way up the tibial spine to represent the sagittal cut (Figure 22). The probe’s rotation will set the initial component rotation during the Implant Planning stage. Consider the placement of this reference to protect the ACL, so as not to undermine it during bone preparation. NOTE: This step is critical to establish the rotational axis of the tibial preparation in line with the tibial spine and the central-most edge of the component. Figure 22. Utilize the axis of the point probe to set both the rotation of the tibial component and the sagittal wall.

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Tibial Condyle Surface Mapping The Tibia Free Collection stage (Figure 23) offers a visualization of the tibial mechanical axis and rotational axis previously collected (blue lines) as well as these discrete tibial landmark points (yellow dots). •• Digitize the tibial condyle similarly to the Femur Free

Collection stage.

•• Define anterior and medial edges of the condyle as

far posterior as is accessible. Map the intercondylar eminence along the axis of the point probe. Fill in the surface, moving anterior to posterior as space allows.

•• Externally rotate the tibia, apply valgus stress,

or hyperflex to access additional portions of the articulating condylar anatomy. Collect points approximately 8 to 10 mm down the anterior and medial side of the condyle, so that overhang can be identified during the Implant Planning stage. It is important to work the probe around the medial side of the bone, past the medial point, in order to digitize the anatomic shape for component sizing during the Implant Planning stage.

Figure 23. Digitize the tibial condyle for utilization during the Implant Planning stage; you can always return to this stage to define more points if needed.

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Implant Planning – UKR The Implant Planning stage for UKR presents you with a virtual representation of the patient’s femoral and tibial anatomy. It visualizes soft-tissue ligament tension to aid in joint balance and demonstrates component-on-component contact points for load transfer and wear patterns. There are two view modes for prosthesis placement: Solid Surface view (Figure 24), and Cross Section view (Figure 25). The Solid Surface view allows you to manipulate these views in 3D space and they will always snap back to their original plane of view. The Cross Section view allows you to drag a finger vertically over the active window to view cross sectional slices of the bone in either the sagittal, coronal or transverse planes, and visualize the position of the implant in that particular slice within the plane.

Figure 24. Femoral prosthesis placement in Solid Surface view.

The goal of the Implant Planning stage is to allow you to localize the components and balance key metrics along the way. You should be able to visualize the postoperative X-Ray before any cuts are made. There are three steps in the Implant Planning stage for UKR: • Prosthesis Sizing and Placement • Gap Planning

Figure 25. Femoral prosthesis placement in Cross Section view.

• Component M-L Position Adjustment

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Screen Overview: Prosthesis Placement (Femur and Tibia) The screen displays four primary viewscreens used to manipulate the implant component. Counterclockwise from upper right are standard sagittal, coronal and transverse planes of view. The lower right view is a 3D “sticky” view that will hold its orientation when manipulated. The following buttons on these screens (Figures 26 and 27) are particularly critical to understand.

1 4 2 3

6 7

1 – Checkpoint Verification button is used to manually force a verification of the defined checkpoint positions on the femur and tibia. This button should be utilized if there is any concern that either of the tracker arrays has moved during registration or planning. 2 – Green Dots button is used to show or hide the cloud of discrete green points collected during Free Collection stages. It is generally helpful to hide the green points in order to view the virtual bone surface unobstructed. 3 – Virtual Bone button is used to show or hide the virtual bone surface. 4 – FEMUR/TIBIA Size arrows will size up (right) or size down (left) the selected component size and display the size currently selected. This sizing option will correspond with the manufacturer’s available sizes.

Figure 26. Prosthesis Placement (Femur) screen.

1 4 5

2 3

6 7

5 – TIBIA Thickness arrows will increase (right) or decrease (left) the bearing component thickness and display the bearing thickness currently selected.

Figure 27. Prosthesis Placement (Tibia) screen.

6 – Solid Surface and Cross Section buttons allow you to choose between a 2D and 3D view of the virtual implant placement with respect to the virtual bone surface. 7 – Add Femur/Tibia Points button may be selected to navigate directly back to the Femur/Tibia Free Collection stage, where additional surface points may be collected.

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Step 1. Prosthesis Sizing and Placement Femoral Component The NAVIO™ Surgical System software will provide a starting size and initial placement of the femoral component, utilizing the landmark points that were collected during the Registration stage. The default coronal alignment of the femoral component is 0° relative to the mechanical axis of the femur, and can be adjusted to accommodate your preference. From the initial placement, you have the ability to adjust the size and placement of the component. When localizing the femoral component on the digitized surface, the following are key metrics to review: •• In the sagittal plane of view, confirm that the size

provides full coverage from the Tidemark point to the posterior point.

•• For a medial surgery, the posterior surface of the

femoral implant should be approximately 1.5 mm anterior of the native posterior cartilage in order to achieve the target flexion gap in Gap Planning. This helps to avoid an excessively tight gap in flexion. For a lateral surgery, position the component flush with the posterior cartilage which is generally well preserved.

•• Adjust component flexion (use the Rotation arrows

in the viewscreen) to achieve desired anterior transition within the virtual condylar surface (Figure 28). The supported implants are designed to be implanted at the following degrees of flexion: Implant

°

Flexion Definition

JOURNEY™ UNI 45°

Angle between the posterior femoral implant post and the femur mechanical axis.

ACCURIS™

0°

Distal cut is perpendicular to the femur mechanical axis.

STRIDE™

25°

Angle of the post holes to the femur mechanical axis.

ZUK™

25°

Angle between the posterior femoral implant post and the femur mechanical axis.

EPIK®

10°

Angle of the post holes to the femur mechanical axis.

StelKast

0°

Angle of the post holes to the femur mechanical axis.

0°

Angle between the axis perpendicular to the distal portion of the femoral implant and the femur mechanical axis.

SIGMA®

Figure 28. Confirm proper anterior transition to minimize risk of patella impingement (upper right, sagittal plane of view).

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NOTE (For SIGMA): The anterior tip of the SIGMA High Performance Partial Knee femoral component should be inset approximately 3 mm beneath the native femur cartilage surface. For reference, it is important to note that the SIGMA High Performance Partial Knee mechanical instruments are designed to make the distal femoral resection perpendicular to the intramedullary (IM) axis of the femur through constrained flexing of the knee, and resecting with the guidance of the tibial preparation. NOTE (For ZUK): To plan the ZUK implant in a manner similar to the manual instrumentation, plan the posterior femoral component flush with the native cartilage and then move the component anteriorly 2 mm. Four clicks is approximately equivalent to 2 mm on the planning screens. At this stage, confirm that the anterior portion of the femoral component is in the desired position in relation to the Tidemark point. •• If the virtual bone surface is behind the implant (on

the cement side, as opposed to the articulating side) this is indicative of a shallow bone-resection, or little-to-no bone/cartilage resection, and you should consider burying the component deeper.

•• Utilize the transverse plane of view (lower left) to

ensure that the component is localized properly on the condyle (Figure 29). The software will provide the starting position for the implant component centered on the distal landmark point that was collected on the femur during the Registration stage. For condyles that are wider than the implant, the prosthesis should be biased laterally (or medially) to optimize tracking on the tibial component.

•• Confirm that the component is not overhanging

medially or laterally, which will be evident if the dark gray of the virtual implant is breaking through the virtual bone surface. If required, you can apply external rotation to the component using the Rotation arrows in the active viewscreen. The software will indicate how much rotation you are applying.

Figure 29. Confirm proper positioning (lower left, transverse plane of view). Distal landmark point is circled.

NOTE: The default rotational value is 0°. Refer to the applicable implant Surgical Technique for recommended implant component rotational constraints. NOTE (For SIGMA):The allowance for angular orientation variation between the femur and the tibia with the SIGMA High Performance Partial Knee components is ± 10°.

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•• You may also evaluate implant placement using the

Cross Section view. Switch to this view by selecting Cross Section on the right side of the screen. Activate the desired plane of view and slide a finger vertically on the viewscreen to navigate through cross sectional views. NOTE: If at any point during Implant Planning you feel as if the current virtualization of the femoral condyle is not sufficient, press the Add Femur Points button in the lower right portion of the screen. Collect additional points in Femur Free Collection in the deficient areas. Continuing forward from this screen will bring you right back to the Implant Planning stage. Tibial Component The NAVIO™ Surgical System software will provide a starting size and initial placement of the tibial component, utilizing the medial landmark point and intercondylar eminence ridge collection to size the component mediolaterally and place the anterior portion of the component on the most anterior point collected. From the initial placement, you have the ability to adjust the size and placement of the component.

Figure 30. Consult the lateral radiograph and X-Ray templates prior to surgery.

Identifying the posterior aspect of the tibia may be difficult in a tight knee. If applicable, use a lateral radiograph (Figure 30) to help determine the size of the tibial component prior to conducting a UKR procedure. When localizing the tibial component on the digitized surface, the following are key metrics to review: •• Confirm the size of the implant component, using

Figure 31. Check component sizing (lower left, transverse plane of view). Assess for medial and anterior overhang (red lines) by identifying breakthrough of the tibial component model through the virtual bone surface.

the transverse plane of view (lower left), along with the TIBIA Size arrows in the control panel on the right side of the screen. Adjust as necessary, paying close attention to avoid medial and anterior overhang (Figure 31).

•• Confirm the posterior slope, utilizing the sagittal

plane of view (upper right). The software will display the posterior slope within this viewscreen (Figure 32), which reflects the slope of the tibial implant component with respect to the mechanical axis defined during the Registration stage. NOTE: The angle of posterior slope will default to the angle recommended by the manufacturer for that specific tibial implant system.

•• The rotation of the tibial component is set in parallel

with the rotation of the point probe used to define the intercondylar eminence ridge that was collected during the Registration stage. This rotation can be adjusted using the arrows in the transverse plane of view.

Figure 32. Confirm posterior slope is appropriate for patient (upper right, sagittal plane of view). 17

•• Confirm that the tibial component is flush with the

bone anteriorly, utilizing the sagittal plane of view (upper right).

•• The tibial component will default to the thinnest

bearing. This thickness can be adjusted by changing the component using the TIBIA Thickness arrows in the control panel on the right side of the screen. The component position will default to place the top of the bearing 3 mm above the previously defined low point collected on the tibia during the Registration stage. Using the arrows in that viewscreen, you may move the component superior, decreasing resection depth. NOTE (For Inlay Style Uni Implants): Refer to the applicable implant Surgical Technique for recommended resection depth.

•• You may also evaluate implant placement using the

Cross Section view. Switch to this view by selecting Cross Section on the right side of the screen. Activate the desired plane of view and slide a finger vertically on the viewscreen to navigate through cross sectional views. NOTE: If at any point during Implant Planning you feel as if the current virtualization of the tibial condyle is not sufficient, press the Add Tibia Points button in the lower right portion of the screen. Collect additional points in Tibia Free Collection in deficient areas. Continuing forward from this screen will bring you right back to the Implant Planning stage.

Step 2. Gap Planning This stage provides you with the ability to balance soft-tissue laxity (gap) throughout the patient’s range of motion. The soft-tissue gap planning is predicated on the stressed range of motion input from the Registration stage. During the Stressed ROM (range of motion) stage, you applied valgus stress (for a medial condyle) to the operative-side collateral ligament in order to plot how much ligament laxity the compartment has. •• The Gap Planning screen (Figure 33) has four

Ligament button

interactive viewscreens for translating and rotating the components with respect to the patient’s virtualized joint. Beneath those viewscreens is a graph from 0 through 120° of flexion. The x-axis represents the flexion (degrees). The y-axis represents millimeters of either the relative gap/laxity (+) or the overlap/tightness (-).

Figure 33. Run a finger over the flexion gap graph at bottom of screen to visualize the theoretical articulation of the femur and tibia implant components throughout the ROM in the viewscreens.

•• The orange graph line represents discrete points of

flexion input from the Stressed ROM screen. If an orange point is above the zero line, this represents “Gap” in the joint. If an orange point is below the zero line, this represents “Overlap” of the theoretical joint. You want to avoid overlap, which may over-stuff the joint and load the contralateral compartment.

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