Download The Zimmer Trabecular Metal Total Ankle System: Features and

CHAPTER
8
Stuart H. Myers
Lew C. Schon
The Zimmer Trabecular Metal ­
Total Ankle System: Features
and Techniques
INTRODUCTION
DESIGN FEATURES
The Zimmer Trabecular Metal (TM) total ankle implant has
numerous design features that distinguish it from other total
ankle systems. An essential difference of this system is that it
uses a lateral approach to reach the talocrural joint instead of
the standard anterior approach. The implant, its method of insertion, and the ability to address associated pathology and malalignment stem from the opportunities made possible with this
surgical vantage point. The altered perspective of the anatomic,
physiologic, and biomechanic properties of the native joint permits design opportunities in accordance with these elements
that may lead to a more versatile and enduring prosthesis.
Perhaps most demonstrative of this change from anterior
to lateral relates to the bony preparation to create the ideal
void for the TM device. Because of the lateral approach, each
surface can be milled with a router, following the natural contour of the concave distal tibia and convex dome of the talus.
The radius of the tibial and talar cuts based off the central
axis, roughly approximated by the tips of the malleoli, is reflective of their native geometry. This permits one curved cut
for each surface in higher-density bone with a greater surface
area than what could be achieved with a flat cut. Given this
preservation, the implant’s curved shape apposes the retained
denser bone, particularly on the anterior and posterior tibia.
On the medial aspect, these arches of maintained bone anteriorly and posteriorly act as buttresses to the medial malleolus,
strengthening the integrity of the mortise. This is another distinction from other ankle replacements, whose two converging flat cuts, one perpendicular to the axis of the tibia and the
other parallel to the medial malleolus, theoretically create a
greater stress concentration at the intersection of the planes.
The arched implants transmit their stresses perpendicularly to
the bony surfaces along the course of the anatomic macro- and
All figures © Lew C. Schon 2013. All rights reserved.
microtrabeculations, which may minimize bony remodeling in
accordance with Wolff’s law.
A principal advantage to the lateral approach is that it
­permits an extensile exposure to the ankle and subtalar joint in
a surgical plane between angiosomes. This may enhance wound
healing and could help to minimize the wound healing complications seen with the anterior approach. The incision can
be along a scar from a prior ankle procedure, such as an ankle
fracture fixation, an ankle ligament repair, or a peroneal recon­
struction. Dissection may also occur along the subtalar joint
distally to address pathology or perform a fusion. Using the
lateral approach, the anterior and posterior soft tissues can be
­protected by retraction as the router removes bone. The direction of the burring tool is from lateral to medial within a neurovascular safe zone. Thus, a consequence of the preparation of
the surfaces from the transfibular approach is the avoidance of
the anterior to posterior directed sawing, which may jeopardize
the tibial nerve, veins, and artery.
The device is semiconstrained, consisting of two components that correspond to the normal tibiotalar anatomy. The
components articulate plastic to metal with a bicondylar surface
that permits high contact even with rotation. These contours allow for stability and self-centering with the anticipated 2° to 4°
of internal and external rotations. Although the router cuts a
cylindrical shape, the talar implant is designed to have a lateral
sagittal radius larger than the medial radius. This mimics the
natural conical shape of the talus. The implant surface represents an oblique cone (in contrast to a right cone) in our design.
In neutral position with the two components of the ­implant on
top of each other at the coronal midline, the ­central axis is 8°
relative to the tibia or talus bone interface ­surfaces. The crosssectional thickness of the implants together at this midcoronal
plane is constant from lateral to medial. The conical nature of
our design is seen along the posterior half of the talar component, where the talar component progressively b
­ ecomes slightly
wider.
The talar component is composed of both TM and c­ obalt–
chrome with an intervening layer of titanium. The TM portion
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68 Total Ankle Replacement: An Operative Manual
interfaces with the cancellous bone, whereas the cobalt–chrome
portion interfaces with a high-density cross-linked tibial polyethylene tray locked into a tivanium (titanium alloy) tibial
housing. This titanium aspect is in turn bonded to a thin layer
of pure titanium connected to the TM tibial surface. The assembled tibial component is symmetrical and therefore has no
sidedness. There are six available sizes for all the implants. With
each size, the dimensions (width, length, and radius) all change
to maximize the coverage and to optimize surface-to-surface
transmission of stresses. No mismatching of sizes is permitted
given this optimized engineering. The highly cross-linked polyethylene comes in three thicknesses (0, 12, and 14 mm), and
has a central sagittal ridge that corresponds to the sulcus between the talar condyles.
To counteract shear forces and provide bone–implant interface stability with flexion/extension, anterior/posterior translation, and internal/external rotational forces, fixation rails are
arranged in the coronal plane perpendicular to the flexion/
extension axis, which is made possible by the lateral exposure.
This is distinct from the sagittally oriented implant protrusions
or the cylindrical central posts of most of the other systems. The
Zimmer TM system features a triple fixation strategy utilizing
coronally oriented rails, the surface TM–bone interface, and
strategically applied methylmethacrylate cement placed within
a small void adjacent to its four rails. The cement provides immediate fixation, and the trabecular tantalum metal facilitates
fixation over time.
A fibular osteotomy is required for the lateral approach
with the Zimmer TM ankle. Obviously, this permits the large
exposure. The fibula osteotomy must be performed about 2
cm above the joint to minimize syndesmotic instability. Also,
the fibula must be distally or posteriorly rotated on the intact
calcaneofibular ligament (CFL), posteriotalofibular ligament,
and, depending on the exposure, the distal peroneal retinaculum. For balancing the ankle, this osteotomy facilitates preservation of the deltoid ligament. During correction of deformity,
laminar spreaders are inserted medially or laterally to achieve
alignment out of varus or valgus, respectively, against the taut
deltoid. Rotational and translational corrections can be visualized and addressed through the exposure. With the fibula out
of the way, these corrections are achievable. Furthermore, the
osteotomy allows for deliberate fibular shortening/lengthening and rotational correction, as necessary, to help with coronal
plane balancing. The downsides of the osteotomy are the additional equipment and time it takes to perform and then repair
during the surgery. After the surgery, there may be risks for
delayed union, malunion, or nonunion.
A final distinguishing characteristic of the Zimmer TM ankle system is its rigid alignment frame and cutting assembly.
The frame is attached to the patient via two fixation pins in
the tibia: one fixation pin in the talus and a transfixion pin in
the calcaneus. The frame rigidly holds the tibial plafond and
talus in place while the burr removes the articular cartilage and
subchondral bone. For deformity correction, the alignment is
corrected first out of the frame through soft tissue and bony
releases. Then rotational, translational, and coronal malalignments are rigidly reduced with temporary intra-articular laminar spreaders and transarticular wires and are then held in
corrected position with the frame’s calcaneal, talar, and tibial
pins. In general, all corrections are performed with the deep
# 151733 Cust: LWW Au: DeOrio Pg. No. 68
and often the superficial deltoid ligament preserved and adjustments made by removing bone or altering fibular length.
This fixation of the alignment/cutting system to the bones is
conducive to accurate milling, whereby the part being milled is
secured as is the cutting tool, helping to minimize inaccuracies
from object or tool movement.
INDICATIONS
The indication for the use of the Zimmer TM total ankle system is end-stage tibiotalar arthritis. Etiologies of the degenerative arthritis include prior trauma, primary osteoarthritis,
congenital deformity, and rheumatoid and other inflammatory
arthropathies.
CONTRAINDICATIONS
Absolute contraindications to the implantation of the Zimmer
TM total ankle include dense sensorimotor neuropathy, spasticity/paresis, and malleolar insufficiency.
Relative contraindications include diabetes, obesity, severe
instability, severe deformity, a history of ankle joint infection,
severe osteoporosis, and severe peripheral vascular disease.
PREOPERATIVE PREPARATION,
PLANNING, AND CONCEPTS
Anteroposterior (AP) and lateral radiographs can be used to
template the prosthesis and predict implant size. Tibial and
­talar components must be the same size.
Required equipment that might not be required with the
use of other prostheses include a radiolucent operating table
and a full-size C-arm.
STEPWISE TECHNIQUE
EXPOSURE
The patient is placed supine on a radiolucent table. A bump
or beanbag is placed under the hip to internally rotate the hip.
Ideally, the foot is positioned such that the coronal plane is parallel to the floor. A nonsterile tourniquet can be applied to the
thigh and used at the discretion of the surgeon. An ankle block
is also performed to reduce anesthetic requirements during the
procedure.
Incision is made along the posterior fibula, ending just distal
to the tip of the lateral malleolus. Take care to avoid injury to
the superficial peroneal nerve, which will exit the fascia near
the proximal extent of the incision. Section the anterior tibiofibular ligament (ATFL) and the anterior–inferior tibiofibular ligament (AITFL) (Fig. 8.1). Leave a cuff of ATFL attached
to the fibula to allow repair at the end of the case. Make an
oblique fibular osteotomy such that the medial border of the
proximal fragment is 1.0 to 1.5 cm proximal to the joint line
(Figs. 8.2 and 8.3). Reflect the distal fibular fragment, hinged
by the CFL and posterior talofibular ligament (PTFL). Incise
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Chapter 8 ■ The Zimmer Trabecular Metal ­Total Ankle System: Features and Techniques 69
Figure 8.1. The ATFL and the AITFL are sectioned before rotating the fibula and exposing the ankle joint.
the posteroinferior tibiofibular ligament (PITFL) and superior peroneal retinaculum incrementally while rotating the
lateral malleolus. Often, adequate exposure can be obtained
while leaving the distal fibers of the PITFL intact. Secure the
lateral malleolus to the calcaneus with a K-wire (Fig. 8.4). In
some cases, particularly when there is CFL insufficiency, it will
be possible to rotate the fibula posteriorly off the peroneal retinaculum. Expose the medial joint via a standard anteromedial
approach to the ankle, avoiding the saphenous vein. Remove
impinging medial osteophytes from the anterior aspect of the
medial malleolus and off the talar body and neck. Release the
posterior capsule for exposure and to correct deformity and
permit placement of posterior retractors. Perform gastrocnemius recession or Achilles tendon lengthening if needed to
achieve adequate dorsiflexion. Posterior tibial tendon fractional lengthening at the musculotendinous junction can be
performed for severe varus deformities as indicated.
MEDIAL–LATERAL SIZING
Use the medial/lateral sizer to assess talar width. Place the sizer
between the plafond and the talus such that it abuts the articular portion of the medial malleolus. Fluoroscopy should be
used to confirm proper placement (Fig. 8.5). If between sizes,
choose the smaller size.
FRAME ASSEMBLY AND ALIGNMENT
Place the leg into the alignment stand with the heel in the heel
cup. Adjust the heel cup placement so that the lateral ankle
view will not be obscured by the alignment rods. Adjust the calf
block supports so that the anterior tibial crest is parallel to the
longitudinal frame rods. To help determine the proper ankle
Figure 8.2. Exposure following fibular osteotomy. The elevator is
used to lever the distal fibula and expose the ankle joint.
Figure 8.3. Fluoroscopic image after fibular osteotomy.
Figure 8.4. Fluoroscopic image showing K-wire fixation of fibula.
The probe is resting on the anterior ankle. Its alignment with the
ankle joint confirms correct frame assembly and position.
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Figure 8.7. Image shows medial-to-lateral placement of the calcaneal transfixion pin.
Figure 8.5. Fluoroscopy is used to confirm correct sizer
placement.
rotation, place a straight malleable retractor through the medial incision into the medial gutter. Rotate the leg such that the
tibial tubercle is oriented vertically. This should correspond to
5° to 10° of medial angulation of the malleable retractor. To
finalize rotation, use the flat end of the joint line tracer probe
in the cutting jig and place it against the anterior aspect of the
lateral articular body of the talus. If the rotational alignment is
correct, the probe end should be flush with or parallel to this
anatomic landmark. One other check is to obtain an AP radiograph to see a perfect mortise shot and a lateral radiograph to
see collinear arcs of the talus.
Attach foot plate brackets at the level of the metatarsophalangeal joints. Secure the foot to the plate by running an
elastic bandage through the foot plate brackets (Fig. 8.6). Do
Figure 8.6. The foot is secured to the foot plate with an elastic
bandage.
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not allow the foot brackets to compress the foot and create a
pressure point. Use the tibial alignment rod visually and radiographically to determine the axial alignment of the limb in
the coronal plane. Place a calcaneal transfixion pin from medial to lateral (Fig. 8.7). Ideal placement is 2.5 cm anterior to
the insertion of the Achilles tendon, avoiding injury to medial
structures. Attach the calcaneal transfixion pin to the foot plate
using pin hooks. Tighten the hooks symmetrically such that pin
bends slightly and then remove heel support cup.
Attach the talar pin connector to the foot plate talar pin
post. Thread the talar pin through the loosened pin connector so that pin connector placement can be adjusted to allow
proper talar pin trajectory (Fig. 8.8). Make a small incision
over the talar neck and advance the talar pin (already threaded
into pin connector) into the talar neck. The pin should begin
Figure 8.8. Flouroscopic image shows correct talar pin
placement.
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Chapter 8 ■ The Zimmer Trabecular Metal ­Total Ankle System: Features and Techniques 71
Figure 8.9. Frame assembly with attached tibial, talar, and calca-
neal pins.
below the midline of the talus neck, directed away from the
talar dome in a distal to proximal direction. Ensure on an AP
radiograph that the pin will not interfere with the talar cut and
on a lateral radiograph that the clamp does not block the view
of the dome. Tighten pin connector clamps (Fig. 8.9).
Again use the tibial alignment rod and fluoroscopy to ensure that the rod is parallel to the medial border of the tibia
(Fig. 8.10). If there is tibial deformity, this landmark may not be
ideal. Alignment at the joint line also can be determined using
the tibial alignment rod at the joint with the assistance of the
probe as a perpendicular cross-reference. Intra-articular deformity correction is performed using laminar spreaders to distract
the joint out of valgus (with a lateral laminar spreader) or out
of varus (with a medial laminar spreader). Also correct for any
translational or rotational deformities by manually shifting the
tibia. The correct alignment should be visualized by examining
the leg and joint. Use of the back of the probe against the anterior talus confirms the talar rotation if there is no talar lateral
shoulder deformity, and lining up the joint surfaces visually
helps determine the tibial rotation. Radiographs confirming
the proper alignment corrections should be obtained. If it is
difficult to hold the correction, transarticular K-wires can be
placed. Once the correction is visually and radiographically correct, the tibial pins are placed. Use two 5.0-mm pins to secure
the tibia to the medial upper frame rod. Unicortical fixation is
sufficient. Additional rigidity should be achieved by attaching
the carbon fiber rod to a tibial pin and the medical frame bar
with pin-to-rod clamps. If additional rigidity is still needed, particularly if correcting a valgus deformity, the distal tibial pin can
be locked with a carbon bar to the talar pin. Make sure that this
bar is removed later, before attempting to put the joint through
a trial range of motion. If there is a translational deformity, the
distal tibial pin can be placed from anterior to posterior in the
distal tibial metaphysis just medial to the anterior tibial tendon.
Again confirm that the deformity correction has been maintained in all planes visually, tactilely, and radiographically.
AP SIZING
Select AP sizing guide that corresponds to the medial–lateral
size already selected. Compare curvature and size of AP sizing
guide (silhouette) to the talotibial articulation. Avoid excessive
overhang by rounding down between sizes. The medial–lateral
size must match the AP size. If the implant is oversized, the tibial
milling may need to pass medial to Hardy’s notch at the corner
of the medial malleolus and the distal tibial plafond. Also, if this
is insufficient to accommodate the width, then the prosthesis
may overhang laterally, requiring some grooving of the fibula
when performing the fibular osteotomy reduction and fixation.
POSITIONING
Figure 8.10. The tibial alignment rod should be parallel to the
medial border of the tibia.
Attach the cutting guide with cutting guide pin peg oriented
distally to lock position the guide. Use the probe to assess position. The probe should touch the talus at the apex of the
articular arc. Rotate the cutting guide pin 180° to allow free rotation. Adjust anterior/posterior and proximal/distal position
so that the probe traces an arc that is concentric with the talar
articulation and intersects the talar articulation arc at its apex
(Fig. 8.11). If there is a low dome talus or flatter top talus, it is
recommended to choose a height of the new joint line above
the talus line. In a standard arthritic joint, a joint line 2 mm
above the arc is recommended to maintain the height of the
talus dome. Lock the lateral cutting assembly into place.
It is useful to place a probe into the cutting jig holes marked
“TALUS” and “TIBIA #1” to visualize bone cuts (Fig. 8.12). Placing the thicker end of the probe through any of the cutting jig
holes and resting it anterior to the tissues allows fluoroscopic
and direct visualization of the coronal orientation (varus/valgus) of the new joint line (Figs. 8.13 and 8.14). The ability to
assess surfaces of the tibia and talus relative to this horizontal
probe assists in alignment, especially in conjunction with the
vertically oriented alignment rod. Final adjustment for varus,
valgus, translation, and rotation should occur before p
­ repping
the bone. This requires an AP and a lateral radiograph. If
­necessary, the half pin orientations are altered.
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72 Total Ankle Replacement: An Operative Manual
Figure 8.11. Sweeping an arc with the probe in the POSITION
hole traces the joint line.
Figure 8.14. Fluoroscopic examination of the guide pin relationship with the ankle joint.
BONE PREPARATION
Attach the precutting guide (select correct size) to the cutting assembly. The cutting guide pin should be oriented distally (locked). Tighten anterior and posterior stops to further
secure the cutting guide. Drill each of the holes over either
the talus or the tibia (Fig. 8.15). Use a “pecking” or “tapping”
technique with contacting the cortex to avoid drill deflection.
If there is deflection, use the open end of a wrench as a guide
to capture the drill near the bone to help minimize the deflection. The drill should be buried up to the drill bit etch mark
that corresponds to implant size. Fluoroscopy must be used to
help prevent drilling past the corner of the mortise (Fig. 8.16).
Chuck the drill bit at this depth or use a surgical marker to note
Figure 8.12. Sweeping an arc with the probe in the TALUS hole
traces the talar bone resection.
Figure 8.13. Visual inspection of the guide pin relationship with
the lower leg alignment. The guide pin indicates the coronal plane
alignment of the bone cuts.
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Figure 8.15. Drilling the talus holes before milling minimizes the
amount of bone milled and increases the precision of the milling.
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Chapter 8 ■ The Zimmer Trabecular Metal ­Total Ankle System: Features and Techniques 73
Figure 8.18. Use of a trial implant to set the guard stop at the
correct place on the burr shaft.
Figure 8.16. Fluoroscopy should be used during milling to reduce the risk of weakening the medial malleolus.
the proper depth. Next unlock the precutting guide and use
the drill through the guide holes to remove more bone.
Remove the precutting guide and attach the cutting guide.
Insert the cutting guide pin such that it is oriented proximally
(unlocked). Insert the burr into the burr guard and then into
the “TALUS” hole in the cutting guide (Fig. 8.17). Advance
the burr tip until it is resting on the lateral talus. Rest the ­talar
trial implant on the burr guard such that the burr guard stop
can be attached at a distance equal to the width of the implant
(Fig. 8.18). This prevents burring into the medial malleolus.
Attachment of the 5-mm spacer to the burr guard will further protect the medial malleolus. Set the anterior and posterior ­excursions by adjusting the corresponding stops. Retract
Figure 8.17. Several sweeps should be made with the burr, each
sweep cutting slightly deeper and removing the bone in a controlled
fashion.
anterior and posterior soft tissues with an army/navy retractor
and posterior soft tissue retractor, respectively. Use the end-­
cutting portion of the burr initially by overdrilling previous drill
holes. Be sure to irrigate while burring to prevent overheating
of the bone (Fig. 8.19). Begin in the anterior talus and “peck
drill” a nest of tunnels from lateral to medial. Once down to
the 5-mm spacer, remove the spacer and proceed to the final
depth, checking the images. The most medial talar articular
surface should be intact if the medial-to-lateral width (ML)
is slightly undersized. If the ML is fully sized and especially if
there are osteophytes in the gutter, advance to the lateral cortex of the medial malleolus. Next go to the posterior talus and
“peck drill” a nest of tunnels, again checking the images at the
end to ensure that the proper depth is reached. Finally “peck
drill” the center. Then, use the side-cutting portion of the burr
to sweep out the arc defined by the cutting guide (Fig. 8.20).
Make several sweeps, each one removing sequentially more
bone (Fig. 8.21). Do not attempt to make the entire talar cut in
one full-thickness arc.
Figure 8.19. The adjustable anterior and posterior stops on the
cutting assembly prevent excessive excursion of the burr.
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Figure 8.22. Following the bone cuts, a rongeur removes any
remaining bone debris.
Insert the burr through the hole marked “TIBIA #1.” A 5-mm
spacer should not be used at this time. Reset the anterior and
posterior excursions by adjusting the respective stops. Burr the
tibia with the “peck-drilling” nest technique in a fashion similar
to that used for the talus. Sweep the burr in a counterclockwise
direction to maximize control. Remove any remaining bone
with a rongeur (Fig. 8.22). Irrigate the joint to remove debris.
Remove the burr and replace it into the “TIBIA #2” hole. Adjust
the anterior and posterior stops and repeat the tibial cutting
sequence (Fig. 8.23).
Make a clockwise pass with the burr flush against the cutting guide. Under direct visualization or via fluoroscopy, serially
­adjust the burr guard in order to remove 1 to 2 mm of bone at
a time.
Inspect the medial gutter and remove any impinging bone.
Irrigate to remove any bony debris (Fig. 8.24). Assemble rail
hole drill guides and link them by aligning the tibial guide key
and the talar guide slot.
Insert the linked drill guides (Fig. 8.25). The hub of the
guides should be flush against the lateral tibia and lateral talus
(Fig. 8.26). If the drill guides do not seat properly, return to the
tibial cutting stage and deepen the tibial cuts. The drill guide’s
two pieces move along a sagittal rail “link” in dorsiflexion and
plantar flexion to maintain their congruency but permit the
rails to be cut independently in the sagittal plane into the tibia
and talus for optimal alignment.
Insert the smallest spreader pin between the drill guides
(Fig. 8.27). Upsize the spreader pin size if necessary to achieve
tight fit of guides in the tibiotalar cavity. With the spreader pin
pushing the guides axially into the bone surfaces, the metal
should be flush with the bone. It is recommended to jiggle
the guide components to allow them to sit more congruently
against the bone so as to maximize contact area with the tibial
and talar cuts.
Figure 8.21. Multiple sweeps are made with the side-cutting burr
to ensure precision.
the talar cut.
Figure 8.20. The side-cutting burr is used for the final bone cuts
after the bone has been drilled.
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Figure 8.23. The tibial cut is made in a fashion similar to that of
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Figure 8.24. The ankle joint, following bone resections.
Figure 8.26. Fluoroscopic view of the linked drill guides.
Figure 8.25. The linked drill guides have been inserted into the
ankle joint.
Use fluoroscopy to assess placement of the drill guides. The
notch on the tibial drill guide should be along the mechanical
axis of the tibia (Fig. 8.28). No space should be visible between
the bone and the rail hole drill guides. Drill guide holes should
also be perpendicular to the frame rods.
Secure the rail hole drill guides to the tibia and the talus
with four 1.6-mm K-wires. Drill the rail holes sequentially, inserting a rail hole stabilizer into each hole before drilling the
next hole (Fig. 8.29). Ensure no loss of alignment with orthogonal fluoroscopic views. Remove the K-wires, spreader pin, and
rail hole drill guides. Inspect the rail holes. By design, they will
extend neither to the medial talus nor to the medial tibia.
TRIAL
Insert the appropriately sided and sized trial implants. Tibial
provisional implants come in 10-, 12-, and 14-mm sizes. These
correspond to the three available polyethylene inserts, which
are also identified and sized in 2-mm increments. Remove the
K-wire securing the fibula and reduce the lateral malleolus to
assess lateral impingement. If there is a carbon bar crossing the
Figure 8.27. Placement of a spreader pin between the drill
guides prior to drilling.
ankle joint (such as one between the lower tibia and the talus to
add further stability in the face of a deformity correction), this
should be disconnected for the trial.
Remove the metal foot plate support. Assess range of motion
and valgus stability. Varus stability cannot be assessed prior to
fixation of the fibular osteotomy. If valgus laxity is present, consider re-trialing with larger tibial provisional implant.
If dorsiflexion is limited to less than 5°, consider Achilles
tendon lengthening or gastrocnemius recession.
IMPLANT INSERTION
Thoroughly irrigate joint space and remove any debris. Tighten
all clamps except the foot plate’s angle-locking pins. Leaving the
angle-locking pins out permits some mild joint distraction when
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Figure 8.28. The notch on the
tibial drill guide should overlie the
­mechanical axis of the tibia.
plantarflexed and joint compression when dorsiflexed. Assemble the talar implant/inserter with the Zimmer logo oriented
toward the inserter handle. Insertion of tibial provisional prior
to insertion of talar component facilitates proper insertion.
Insert the talar component, keeping the inserter handle perpendicular to the alignment rods (Fig. 8.30). Gentle impaction
with a mallet can be used then once the rail has been engaged
and the path of the rail established. Continue impaction while
dorsiflexing the ankle to permit the implant to sit flushly on
the surface. Vigorous impaction risks medial malleolar fracture.
Fluoroscopy can be used to assist implant insertion (Fig. 8.31).
Care must be taken to remove the inserter so as not to shift or
rock the prosthesis.
Use the tibial poly assembly tool (with protective sleeve) to
join the tibial component and the tibial poly insert. This should
snap securely into place. Load the tibial component assembly
into tibial inserter, ensuring that the Zimmer logo is oriented
toward the inserter handle. Remove the tibial trial component
Figure 8.29. The drill guides are sequentially drilled and then
filled with rail hole stabilizer pins.
Figure 8.30. Placement of the talar component is accomplished
with a tibial trial component in place.
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Chapter 8 ■ The Zimmer Trabecular Metal ­Total Ankle System: Features and Techniques 77
harden, check anteriorly, posteriorly, medially, and laterally for
residual cement or bone debris and remove it.
REPAIR AND CLOSURE
Figure 8.31. Fluoroscopic view of the talar component in place
along with a tibial trial component.
and insert the tibial implant assembly. Initially insert it with the
ankle in mild plantar flexion to allow the implant to seat on the
surface of the tibia and past the edge of the talar implant. Then
dorsiflex the foot to apply compressive forces while inserting
the tibial component. Vigorous impaction places the medial
malleolus at risk of fracture and should be avoided. Fine tune
the position after removing the inserter with the impactor under fluoroscopic guidance (Fig. 8.32).
Unwrap the self-adhesive bandage from the foot and remove
all pins. Remove the alignment stand assembly from the field.
Apply the tourniquet and mix cement using the cement delivery system assembly. Load the cement into a syringe and inject
into each rail hole. Use a retrograde fill technique to ensure
complete filling. Approximately 0.5 to 1 cc of cement is needed
to fill each rail hole completely. After the cement begins to
Figure 8.32. Tibial and talar components in place before fibular
reconstruction.
Reduce the fibula and assess lateral joint congruency/impingement and varus ankle stability. If impingement is present,
­remove some of the articular surface of the lateral ­malleolus.
The fibula may be lengthened/shortened, angulated, or
­rotated in order to restore the mortise and to obtain proper
lateral ankle ligament tension.
Fibular fixation can be achieved with lateral plating. Plate
design and usage of a lag screw or an axial screw from the tip of
the fibula are at the surgeon’s discretion. Perform an external
rotation stress test of the syndesmosis following fibular fixation.
If indicated, trans-syndesmotic fixation can be added and later
removed according to the surgeon’s preferred practice. Apply
bone graft harvested from the rail hole drillings in and around
the fibula osteotomy site.
Repair the ATFL in an end-to-end fashion or as a ligamentous periosteal sleeve. Close the joint capsule of the medial
ankle arthrotomy. The ankle should be stable to testing. Next,
close the subcutaneous tissue and skin in standard fashion.
­Apply a bulky cotton and plaster splint with the ankle in neutral
dorsiflexion.
PEARLS AND PITFALLS
Use of the burr assembly requires some adjustment on the part
of the surgeon. The constrained cutting technique is not used
by some other systems. Skiving of the burr can occur when cutting surfaces that are not perpendicular to the axis of the burr.
A “pecking” technique can be very effective in minimizing skiving. A wrench can also be used to achieve this (Fig. 8.33).
The medial arthrotomy and cleanout is important in minimizing the risk of medial impingement. Aggressive decompression is important, but must be balanced in order to minimize
the risk of medial malleolus fracture.
If the 14-mm tibial trial provides the best soft tissue balance,
additional distraction might be necessary for final implantation.
Figure 8.33. Use of a wrench to prevent drill skiving.
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78 Total Ankle Replacement: An Operative Manual
Accomplish this by loosening the rod ends of the alignment
rod pin-to-rod clamps and slide the alignment stand distally.
Retighten clamps in distracted position.
When cementing, make sure the cement does not extrude
out of the rail holes medially.
many different opinions exist, including the use of mechanical
compression devices, enoxaparin, coumadin, or aspirin.
POSTOPERATIVE MANAGEMENT
As a relatively new implant system, the Zimmer TM total ankle
system has an evolving complication profile. Potential difficulties are in the areas of fibular nonunion/malunion, medial malleolar fracture, and medial impingement.
• First 2 weeks: No weight bearing/splinted.
• Weeks 2 to 6: Walking boot with rocker sole, gentle ROM,
partial WB. Deep knee bends out of the boot with weightbearing ankle dorsiflexion may be instituted at the surgeon’s
discretion five times a day for 20 minutes at a time. The boot
may be removed at night and for bathing.
• Weeks 6 to 10: Full weight bearing in boot unless fibula healing delayed.
• Weeks 101: Wean off the boot and begin resistance training.
Because a standard protocol for deep vein thrombosis prophylaxis has not been established in total ankle arthroplasty,
# 151733 Cust: LWW Au: DeOrio Pg. No. 78
COMPLICATIONS
RESULTS
As with describing this system’s complication profile, a discussion of results is limited by the product’s design features and
method of implantation. As of the writing of this chapter, 140
implants have been inserted worldwide. The complication profile appears to be low. Overall, the designers and early adaptors
are satisfied with the implant and its technique.
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