DEFINITION

The INBONE II (Wright Medical Technology, Memphis, TN) total ankle system, like other total ankle systems, is indicated for end-stage ankle arthritis failing to respond to nonoperative intervention.

In contrast to essentially all other total ankle systems, however, the INBONE II total ankle system uses intramedullary rather than extramedullary referencing.

Although the intramedullary alignment guide passes through the plantar foot, calcaneus, talus, and tibia, it does so anterior to the posterior facet of the calcaneus and does not violate any articulations of the

subtalar joint. It may, however, interfere with the vascularity of the talus.1

To achieve reliable intramedullary alignment, the INBONE II total ankle system uses a leg frame that is initially cumbersome, demands more preincision preparation, and requires greater fluoroscopy time than other total ankle systems. However, with experience, this technique becomes manageable and allows the user to correct deformities prior to making bone cut.

The design of the INBONE I has been changed and is now called INBONE II.

The talus now has a sulcus designed superior surface with a V in the center and a corresponding matching polyethylene.

The talar component has two more anterior pegs on its inferior surface in addition to the central stem. The tibial base plate is now available as a long and a standard length.

The INBONE II has virtually completed replaced INBONE I because of the increased options for fixing the talar component to the talus, the increased stability with the V sulcus in the coronal plane and the increased coverage of the tibia when necessary.

Additionally, to obviate need of the leg holder, a new IN-BONE II is available, called the Prophecy. With this ankle, a computed tomography (CT) scan is sent to the manufacturer preoperatively and molds are created which allow placement of pins. Over these pins are placed the cutting blocks for the talus and tibia. This also allows separation of the cutting blocks to be placed individually on the tibia and talus.

Otherwise, the actual ankle replacement, IN-BONE II, is the same.

 

ANATOMY

 

Ankle

 

 

Tibial plafond with medial malleolus

 

 

 

Articulations with dorsal and medial talus In sagittal plane, slight posterior slope

 

In coronal plane, articular surface is 88 to 92 degrees relative to lateral tibial shaft axis.

 

Fibula

 

 

Articulation with lateral talus

 

 

Responsible for one-sixth of axial load distribution of the ankle Talus

 

 

Sixty percent of surface area covered by articular cartilage Dual radius of curvature

 

Distal tibiofibular syndesmosis

 

 

 

Anterior inferior tibiofibular ligament Interosseous membrane

 

Posterior tibiofibular ligament

 

 

Ankle functions as part of the ankle-hindfoot complex much like a mitered hinge.

 

PATHOGENESIS

 

Posttraumatic arthrosis

 

 

 

Most common cause Intra-articular fracture

 

 

Ankle fracture-dislocation with malunion Chronic ankle instability

 

Primary osteoarthrosis

 

 

 

Relatively rare compared to hip and knee arthrosis Inflammatory arthropathy

 

 

Most commonly rheumatoid arthritis Other

 

Hemochromatosis

 

 

 

Pigmented villonodular synovitis Charcot neuroarthropathy Septic arthritis

NATURAL HISTORY

 

Posttraumatic arthrosis

 

 

Malunion, chronic instability, intra-articular cartilage damage, or malalignment may lead to progressive articular cartilage wear.

 

Chronic lateral ankle instability may eventually be associated with the following:

 

 

Relative anterior subluxation of the talus

 

 

Varus tilt of the talus within the ankle mortise Hindfoot varus position

 

 

Primary osteoarthrosis of the ankle is rare and poorly understood. Inflammatory arthropathy

 

Progressive and proliferative synovial erosive changes failing to respond to medical management

 

May be associated with chronic posterior tibial tendinopathy and progressive valgus hindfoot deformity, eventual

 

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valgus tilt to the talus within the ankle mortise, potential lateral malleolar stress fracture, and compensatory forefoot varus

 

PATIENT HISTORY AND PHYSICAL FINDINGS

 

Patient history

 

 

Often a history of ankle trauma

 

 

 

Ankle fracture, particularly intra-articular Ankle fracture with malunion

 

Chronic ankle instability (recurrent ankle sprains)

 

 

Chronic anterior ankle pain, primarily with activity and weight bearing Ankle stiffness, particularly with dorsiflexion

 

Ankle swelling

 

 

Progressively increased pain with activity Physical findings

 

Limp

 

 

 

Patient externally rotates hip to externally rotated ankle to avoid painful push-off. Painful and limited ankle range of motion (ROM), particularly limited dorsiflexion Mild ankle edema

 

Potential associated foot deformity

 

 

Posttraumatic arthrosis secondary to chronic instability may be associated with varus ankle and hindfoot and compensatory forefoot varus.

 

Inflammatory arthritis may be associated with progressively worsening flatfoot deformity, valgus tilt to the ankle and hindfoot, and equinus.

 

IMAGING AND OTHER DIAGNOSTIC STUDIES

 

Weight-bearing anteroposterior (AP) with contralateral ankle included, lateral, and mortise views of the ankle

 

Weight-bearing AP with contralateral foot included, lateral, and oblique views of the foot, particularly with associated foot deformity

 

With associated or suspected lower leg deformity, we routinely obtain weight-bearing AP and lateral tibia-fibula

views.

 

With deformity in the lower extremity, we occasionally obtain weight-bearing mechanical axis (hip-to-ankle) views of both extremities.

 

We occasionally evaluate complex or ill-defined anklehindfoot patterns of arthritis with or without deformity using CT of the ankle and hindfoot.

 

If we suspect avascular necrosis of the talus or distal tibia, we obtain a magnetic resonance imaging (MRI) of the ankle.

 

DIFFERENTIAL DIAGNOSIS

See the Pathogenesis section.

 

 

NONOPERATIVE MANAGEMENT

 

 

Activity modification Bracing

 

Ankle-foot orthosis

 

Double upright brace attached to shoe

 

 

 

 

Stiffer-soled shoe with a rocker bottom modification Nonsteroidal anti-inflammatories or COX-2 inhibitors Medications for systemic inflammatory arthropathy Corticosteroid injection

 

Viscosupplementation

 

SURGICAL MANAGEMENT

 

In contrast to essentially all other total ankle systems, the INBONE II total ankle system uses intramedullary rather than extramedullary referencing.

 

Although the intramedullary alignment guide passes through the plantar foot, calcaneus, talus, and tibia, it does so anterior to the posterior facet of the calcaneus and does not violate any articulations of the subtalar joint, albeit the vascularity of the talus has been shown to be at risk from the 6-mm drill hole from the calcaneus

through the talus and into the tibia.3

 

To achieve reliable intramedullary alignment, the INBONE II total ankle system uses a leg frame that is initially cumbersome, demands more pre-incision preparation, and requires greater fluoroscopy time than other total ankle systems. However, with experience, this technique becomes manageable and allows the user to correct deformities prior to making bone cut. As mentioned, there is now the option of obtaining a preoperative CT of the ankle, which can obviate use of the leg holder.

 

In our opinion, the INBONE II total ankle system is perhaps more stout than some other systems.

 

 

We have been able to correct coronal and sagittal plane deformities through the tibiotalar joint with appropriate soft tissue balancing and corrective osteotomies relying also on the durability of the implants, particularly the broad talar component and the tibial stem extensions to maintain correction.

Preoperative Planning

 

The surgeon must be sure the patient has satisfactory perfusion to support healing and is not neuropathic.

 

 

Noninvasive vascular studies and potential vascular surgery consultation if necessary

 

The surgeon must inspect the ankle for prior scars or surgical approaches that need to be considered in planning the surgical approach for total ankle arthroplasty.

 

 

The surgeon must understand the clinical and radiographic alignment of the lower extremity, ankle, and foot.

 

The surgeon must be prepared to balance and realign the ankle. Occasionally, this necessitates corrective osteotomies of the distal tibia or foot, hindfoot arthrodesis, ligament releases or stabilization, and tendon transfers.

 

The surgeon should determine whether coronal plane alignment is passively correctable; this provides some understanding as to whether ligament releases will be required.

 

Ankle ROM is determined.

 

 

Ankle stiffness, particularly lack of dorsiflexion, needs to be corrected.

 

 

 

Anterior tibiotalar exostectomy Posterior capsular release

 

Occasionally, tendo Achilles lengthening or gastrocnemius tendon lengthening

 

 

Instrumentation

 

 

These instruments facilitate total ankle arthroplasty:

 

 

Small oscillating and reciprocating saws for fine cuts as well as larger oscillating saw for broad bone cuts. The smaller

 

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saws make it easier to resect prominences with precision and easily morselize large bone fragments to be evacuated from the joint.

 

A rasp for final preparation of cut bony surfaces

 

A 90-degree angled curette, particularly to separate bone from the posterior capsule

 

A lamina spreader to distract the joint and aid in realignment of preoperative ankle deformity. Because the IN-BONE II prosthesis uses a monoblock cutting guide for tibial and talar resection, an intra-articular lamina spreader assists in limiting bone resection. A lamina spreader placed on the concave side of the joint also assists in realignment.

 

A toothless lamina spreader to judiciously distract the ankle to improve exposure even after preparing the surfaces of the tibia and talus

 

 

Large fluoroscopic scanner

 

 

Fluoroscopy confirms proper alignment of the cutting guide to the ankle.

 

 

The leg holder maintains the leg in position relative to the alignment guides and reference drill.

 

 

With the leg holder, the large scanner is necessary to straddle the leg and leg holder. Fluoroscopy through the operating table is necessary, so a little fluoroscopy unit is inadequate.

 

Foot pedals to make adjustments to the table position

 

 

With the foot secured in the leg holder, subtle adjustments to the table's rotation confirm ideal alignment relative to the alignment guides.

 

Subtle adjustments to the alignment guides relative to the ankle allow fine-tuning for the reference drill trajectory.

 

Positioning

 

The patient is placed supine with the plantar aspect of operated foot at end of operating table.

 

Foot and ankle well balanced with toes directed to the ceiling A bolster under the ipsilateral hip prevents undesired external rotation of the hip.

 

We routinely use a thigh tourniquet and regional anesthesia.

 

 

A popliteal block provides adequate pain relief postoperatively, particularly if a regional catheter is used. Moreover, hip and knee flexion-extension is not forfeited, facilitating safe immediate postoperative mobilization.

 

However, using a thigh tourniquet with a popliteal block typically requires a supplemental femoral nerve block (patient temporarily forfeits knee extension in the immediate postoperative period) or general anesthesia.

 

The operative extremity needs adequate space for the IN-BONE II leg holder. The surgeon should be sure the opposite extremity is not secured too close to the operative extremity.

 

Approach

 

 

Anterior approach to the ankle, using the interval between the tibialis anterior (TA) tendon and the extensor hallucis longus (EHL) tendon

 

TECHNIQUES

• Exposure

  Make a longitudinal midline incision over the anterior ankle, starting about 10 cm proximal to the tibiotalar joint and 1 cm lateral to the tibial crest.

  Continue the incision midline over the anterior ankle just distal to the talonavicular joint.

  At no point should direct tension be placed on the skin margins; we perform deep, full-thickness retraction as soon as possible to limit the risk of skin complications.

  Identify and protect the superficial peroneal nerve by retracting it laterally.

  In our experience, there is a consistent branch of the superficial peroneal nerve that crosses directly over or immediately proximal to the tibiotalar joint.

  We then expose the extensor retinaculum, identify the course of the EHL tendon, and sharply but carefully divide the retinaculum directly lateral to the anterior tibialis tendon.

  Some surgeons incise the retinaculum directly over the EHL tendon. However, that does not protect the neurovascular bundle from the deep retractor, and we believe it is better to leave a little retinaculum protecting the neurovascular bundle.

  We always attempt to maintain the TA tendon in its dedicated sheath if present.

  Preserving the retinaculum over the TA tendon prevents bowstringing of the tendon and thereby reduces the stress on the anterior wound. Should there be a wound dehiscence, then the TA is not directly

  exposed.

   

   

   

  TECH FIG 1 • In this case, there is no separate sheath for the TA tendon. Nonetheless, the retinaculum was opened lateral to the tendon, and upon closure, the TA will not be immediately up against the suture line.

   

   

  However, preserving the retinaculum over the TA tendon is not always possible. Frequently, only the retinaculum is present over the tendon and it will be free with the EHL tendon (TECH FIG 1).

   

  Use the interval between the TA and EHL tendons, with the TA and EHL tendons retracted medially and laterally, respectively.

   

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  Identify the deep neurovascular bundle (anterior tibial-dorsalis pedis artery and deep peroneal nerve) and carefully retract it laterally throughout the remainder of the procedure.

   

  Perform an anterior capsulotomy and elevate the tibial and dorsal talar periosteum to about 6 to 8 cm proximal to the tibial plafond and to the talonavicular joint, respectively.

   

  Elevate this separated capsule and periosteum medially and laterally to expose the ankle, access the

  medial and lateral gutters, and visualize the medial and lateral malleoli.

   

  Remove anterior tibial and talar osteophytes to facilitate exposure and avoid interference with the instrumentation.

   

  At this point, it is advisable to take a long 4-mm wide rongeur down the gutters. This will take away a little bone from the talus and malleoli and help prevent impingement and oversizing of the talar component.

• Tibiotalar Alignment

   

  Before placing the lower leg in the INBONE foot and ankle holder, we optimize ankle soft tissue balance and alignment.

  Varus Malalignment

   

  We routinely perform a comprehensive medial release for moderate to severe varus malalignment. This means peeling off all tissue from the medial malleolus circumferentially and not making a transverse cut in the deltoid ligament.

   

  The concept is similar to balancing the varus knee for total knee arthroplasty and was well described by Bonnin et al2 in their 2004 report of the Salto prosthesis.

   

  We routinely subperiosteally raise a continuous soft tissue sleeve from the distal medial tibia to the medial talus.

   

  There is no need to be aggressive on the medial talus, as this could compromise the deltoid branch of the posterior tibial artery that perfuses the medial talar dome.

   

  The superficial deltoid (medial collateral) ligament is elevated but left intact proximally and attached distally. The release of these fibers is complete when the posterior tibial tendon can be visualized.

   

  The deep deltoid (medial collateral) ligament may be peeled off the medial malleolus to balance the ankle appropriately.

   

  In severe varus deformity, the entire deep deltoid ligament must be released to achieve tibiotalar balance (TECH FIG 2A). Overrelease is theoretically possible, but in our experience, with severe varus deformity, the ankle will not collapse into valgus even with a complete release.

   

   

   

  TECH FIG 2 • A. In this varus ankle, a complete medial peel of the deltoid ligament has been performed and the ankle can be opened up with the lamina spreader. B. There was a large ossicle at the tip of the fibula representing an old avulsion fracture containing the anterior talofibular ligament. Hence, the bone

  was removed (C) and a Brostrom ligament reconstruction was performed (D). (continued)

   

   

  In our experience, with an appropriate medial release, optimal bony resection and metal component alignment, and proper sizing of the polyethylene, a lateral ligament reconstruction is only occasionally necessary. One exception is when there has been an avulsion fracture of the tip of the fibula: In that instance, it is difficult to obtain any ability to rotate the ankle against the lateral tissue and a Brostrom ligament reconstruction can be done at the beginning of the case (TECH FIG 2B-D). This marks a significant change from our initial practices in rebalancing the varus ankle. Doing the ligament reconstruction early allows the lamina spreader placed medially to rotate the talus.

   

  A lamina spreader placed in the medial tibiotalar joint maintains the correction.

  Valgus Malalignment

   

  Likewise, a valgus malalignment must be rebalanced.

   

  We seldom need to perform a ligament release. If, however, the patient has anterior subluxation of the talus on the preoperative lateral standing x-ray, the lateral ligament may indeed be

   

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  incompetent. Doing a modified Brostrom procedure is usually all that is required to balance the ankle.

   

   

   

  TECH FIG 2 • (continued) E. Valgus ankle with AP alignment guide properly rotated. However, the talus is not orthogonal to the guide or the tibia. F. In this view, the lamina spreader has been placed laterally on the concave side, and now, the talus is orthogonal to the tibia and the alignment guide.

   

   

  Often, valgus malalignment is secondary to lateral ankle joint collapse and some medial (deltoid) ligament attenuation. This may involve a component of lateral ankle ligament instability as well.

   

  Although the latter portion of this statement seems counterintuitive, this has been our experience in treating many patients with end-stage ankle arthritis and valgus malalignment.

   

  Moreover, lateral release in such situations may lead to paradoxical lateral instability.

   

  We use a lateral lamina spreader to realign the ankle and regain functional tension in the medial ligaments (TECH FIG 2E,F).

• Intramedullary Alignment

 

Be sure the foot and ankle frame is properly assembled and the alignment drill guide trajectory is calibrated. If unsure, you can assemble the cannula into the holder, put the drill in, and take a fluoroscopic

 

view to make sure they coincide (TECH FIG 3A). The foot and lower leg are secured in the leg holder.

 

With correction of the preoperative deformity, we transfer the leg into the foot and ankle holder with the lamina spreader in place (TECH FIG 3B).

 

If the foot and ankle are secured first, it may be difficult to position the lamina spreader effectively.

 

Proper rotation

 

We use a small straight osteotome in the medial gutter as a reference. The foot is rotated until the osteotome is parallel with the leg holder foot plate.

 

Plantigrade foot

 

The heel must be flush with the foot plate of the guide.

 

If it is not, then the talar cut will have a posterior slope, removing an excessive amount of the talar body and increasing the risk of posterior talar component subsidence. Be sure all anterior tibiotalar osteophytes are removed. Perform a gastrocnemius release or tendo Achilles lengthening if necessary.

 

Coronal plane alignment

 

 

In the mediolateral plane, center the heel over the starting point for the reference drill. We use the AP alignment guides to grossly set this alignment.

 

This position should also be in line with the tibial shaft axis so that minimal adjustments will be necessary.

 

Preoperative deformity complicates such preliminary alignment.

 

Sagittal plane alignment

 

We use the lateral alignment guides to grossly set this alignment.

 

The calf and Achilles rests need to be adjusted to optimize the lower leg's position relative to the foot (talus) (TECH FIG 3C).

 

In our experience, proper heel position, optimal tibial alignment, and ideal rotation may make the foot appear internally rotated relative to the lower leg.

 

Fluoroscopic confirmation of proper alignment

 

A large fluoroscopic scanner is needed (TECH FIG 3D,E).

 

Foot pedals to make adjustments to the table position (TECH FIG 3F)

 

With the foot secured in the leg holder, subtle adjustments to the table's rotation confirm ideal alignment relative to the alignment guides.

 

Subtle adjustments to the alignment guides relative to the ankle to allow fine-tuning for the reference drill trajectory may be made with the foot pedal.

 

Reference drill

 

Make a horizontally oriented 1-cm incision in the plantar foot, directly in the opening in the foot frame for passing the reference drill.

 

One centimeter allows for subtle adjustments to the medial and lateral position of the reference drill, even

 

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when its drill sleeve has been positioned on the plantar calcaneus.

 

 

 

TECH FIG 3 • A. Fluoroscopic view being obtained of leg holder with cannula and drill in place to ensure correct assembly of leg holder. B. Gelpi retractor holding deep tissue aside with lamina spreader on concave medial side of varus ankle. C. Leg positioned in leg holder with Achilles and calf rests supporting leg. D. C-arm coming in to obtain AP view of ankle on ipsilateral side. E. Overhead view of lamina spreader in place and deep Gelpi retractor holding deep tissue apart. C-arm to the left is coming in for lateral view. F. Foot pedals are used to control tilting of the table to get the alignment sites exactly parallel to one another.

 

 

The incision should not be more than a 5 mm deep because, otherwise, it could injure the lateral plantar nerve.

 

Insert the drill guide to contact the plantar calcaneus.

 

Avoid holding the frame while inserting this guide, as this could allow the drill to bend, achieving a different trajectory than the guide.

 

Secure the drill guide.

 

Advance the reference drill from calcaneus to tibia.

 

Because the trajectory may change when the drill hits the plantar medial calcaneus, we typically start the drill in reverse and “peck drill” (tap drill) to gradually penetrate the plantar calcaneal cortex without veering from the planned trajectory.

 

Once the plantar cortex is penetrated, the drill is run in forward.

 

Because drilling may shift the frame slightly, fluoroscopic confirmation of proper alignment must be reestablished, after which proper alignment of the reference drill may be confirmed.

 

Advance the drill into the distal tibia, about 8 to 10 cm.

 

Confirm appropriate reference drill position fluoroscopically in both the coronal and sagittal planes.

 

 

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• Tibiotalar Joint Preparation

Sizing

 

Approximate sizing for the component may be performed on preoperative radiographs of either the involved side or the uninvolved opposite ankle.

 

Position the cutting block in roughly the correct position by using the reference drill guide to estimate its position.

 

Fine-tune the cutting block using the reference drill guide under fluoroscopy.

 

In the AP plane, we align the cutting guide with the reference drill guide (TECH FIG 4A).

 

In the lateral plane, we use saw blades through the cutting guide to determine the resection level (TECH FIG 4B). Cutting too low on the talar head may also damage the vascularity to the head of the talus.

 

The position of the cutting block should be finalized only if proper alignment has been confirmed fluoroscopically with the alignment guides.

 

It is important that the guide is centered medially and laterally and no more than 1 mm of bone is removed from the medial malleolus.

Pinning the Cutting Block

 

Once proper position of the cutting block is established, the block is pinned, tibial pins first and talar pins next.

 

Occasionally, the talar pins will skive and not engage the talus, particularly if a lamina spreader is being used to distract the joint or if the talar dome is sclerotic.

 

A toothless lamina spreader may be used to gently keep the talar pins in position as they are driven into the bone, but do this carefully because too much pressure may cause the pins to permanently bind in the cutting guide.

 

Two more pins are placed in the medial and lateral gutter.

 

 

Their mediolateral position is determined on the fluoroscopic image of the final cutting block position. These pins protect the malleoli.

 

 

 

TECH FIG 4 • A. The cutting guide has been placed over the ankle and centered on the drill. B. A lateral view of the cutting guides with the saw and “dummy” blade in place gives the surgeon the amount of bone resected on the top of the talus and the bottom of the tibia.

 

 

If a lamina spreader was used to distract the joint, it will interfere with the pin placement.

 

Try to keep it in place long enough to get enough pins in so that when the lamina spreader is removed, the correction is maintained.

 

Withdraw the axial reference drill.

 

The antirotation drill corresponding to the cutting block is used to drill the antirotation slot in the tibia (the sagittal prominence on the tibial base plate).

Bone Resection

 

With the soft tissues protected, make the tibial and talar cuts.

 

The bone resection should go all the way through the posterior cortex for each cut.

 

It may not be possible on the initial pass, depending on the height of the cutting block and the particular saw used. After the initial cut, the cutting block can typically be lowered to complete the cuts or the cuts can be freehand after the initial cuts. Obviously, avoid plunging the saw blade.

 

Release the Achilles support to help prevent the flexor hallucis longus from being forced anteriorly and cut with the saw. Gently tapping the saw on the posterior cortex is usually possible to confirm that there is still cortex in place.

 

Beware of the length of the saw, as it may cut posterior structures especially when the cutting block is removed.

 

 

Once the posterior cortex has been penetrated for all cuts, the cutting guide and its pins can be removed. The resected bone is evacuated from the joint.

 

 

A toothless lamina spreader may be used to facilitate accessing the most posterior bone. Avoid levering on the malleoli with the instruments, as they may break.

 

A rongeur and an angled curette are ideal to remove the bone.

 

A fine reciprocating saw may be necessary to morselize the resected bone to facilitate removing all of the bone. Avoid cutting into the prepared tibial and talar surfaces with this saw, and protect the malleoli.

 

 

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Tibial Reaming

 

Secure the reamer tip to its shaft within the joint (TECH FIG 5). A toothless lamina spreader may be required to facilitate securing the reamer tip.

 

Advance the reamer. We typically use four segments for the stem extension; this requires reaming 55 mm into the tibia. However, the INBONE prosthesis is now cleared by the U.S. Food and Drug Administration (FDA) for the use of two to eight segments of the tibial stem.

 

Extract the reamer tip from the joint. When the wrench is placed on the reamer tip, avoid activating the driver, as it will spin the reamer and the wrench, which then may fracture a malleolus. Keep your fingers off the trigger during this portion. With the wrench secured to the reamer tip and firmly held with one hand, set the driver for reverse and disengage the shaft from the tip, thereby protecting the malleoli. Extract the reamer tip from the joint and withdraw the reamer shaft from the plantar foot.

Talar Preparation

 

 

Secure the talar alignment guide sleeve to the plantar aspect of the foot plate. Advance the talar positioning guide through this sleeve to the prepared talar surface.

 

Secure the talar pin guide to the positioning guide and place the talar pin. Check to see if the pin will be appropriately placed in the prepared talar surface; if not, then the talar pin guide affords multiple options for pin positioning. Alternatively, the pin may be placed in the “0” position and then the talar pin guide may be used over that initial pin to position a second, more appropriately positioned pin.

 

We have also used the talar trial to determine optimal pin position. The talar trial may be positioned in the ideal mediolateral position and on the posterior cortex (TECH FIG 6A).

 

Two Kirschner wires (K-wires) are placed to secure the talar trial.

 

Once ideal talar trial position is confirmed clinically and fluoroscopically, the central pin for the stem may also be placed through the talar trial (TECH FIG 6B).

 

The fluoroscopic view confirms that the talar component will be in the desired position (TECH FIG 6C).

 

 

 

TECH FIG 5 • Reamer tip being assembled onto reamer to ream out distal tibia.

 

 

 

TECH FIG 6 • A. Talar trial component positioned and pinned with two K-wires. Central pin for talar stem may also be placed through the guide, but because the INBONE II talar component has two anterior pegs, some surgeons implant the talar component without the stem. B. Talar trial component pinned in proper position in AP plane. C. Lateral fluoroscopic image demonstrating satisfactory sagittal plane talar position. In addition to the anterior K-wires, the central pin was inserted in preparation for using the stem. (continued)

 

The anterior peg holes are reamed.

 

Optimally, the talar pin (which is the drill guide for the talar stem) is just posterior midpoint to the center of the calcaneal posterior facet.

 

The 10-mm stem can typically be attached to the talar component on the back table and the talar dome-stem combination may be inserted simultaneously. The 14-mm stem, which we rarely use, requires placing the stem first and attaching the talar component on the stem in situ. Increasingly, we have been using only the anterior pegs on the talar component to avoid taking away too much bone from the talus. Additionally, we have begun bone grafting the calcaneal talar hole to prevent ingress of synovial fluid from the subtalar joint.

 

With the talar trial component removed and the talar stem to be used, the central pin is overdrilled with the acorn reamer to create a relief area for the talar stem (TECH FIG 6D).

 

Final fluoroscopic view demonstrating proper component position. Note that the central stem was used in this case. As mentioned, some surgeons advocate only using the anterior pegs for talar implant stability (TECH FIG 6E).

 

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TECH FIG 6 • (continued) D. With trial talus removed, central pin overdrilled for placing the talar stem. E.

Final fluoroscopic image demonstrating satisfactory component positioning in the sagittal plane.

• Component Implantation

Tibial Stem Assembly within the Joint

 

We routinely leave the ankle plantarflexed, assemble the first two segments of the tibial stem on the back table, and insert them into the reamed tibia with the corresponding wrench (TECH FIG 7A).

 

Return the ankle to the neutral position in which the tibia was reamed and introduce the “X screwdriver” from the plantar foot while the next tibial stem segment is positioned within the joint using the corresponding clip (TECH FIG 7B). A toothless lamina spreader to gently distract the joint may be needed to introduce the next segment, especially if you have used the lamina spreader to balance the joint.

 

 

 

TECH FIG 7 • A. The foot is plantarflexed to allow insertion of the cone piece with one midstem cylinder attached. B. Wrench holding already inserted pieces in place while another midstem component is being inserted. C. An X screwdriver being inserted into stem component to screw it in place. (continued)

 

 

Using the X screwdriver and while securing the wrench holding the other two segments in the tibia, secure the third segment to the stem (TECH FIG 7C). Be sure to hold the wrench that is stabilizing the two segments already in the tibia; if the third segment is advanced and secured and then turned, the wrench could impact the malleolus and break it.

 

Remove the X screwdriver and place the rod impactor from the plantar foot to advance the three-segment stem into the tibia (TECH FIG 7D). Obtaining a radiograph at this point can help ensure the correct angle of placement in this varus ankle (TECH FIG 7E). Be sure to attach the appropriate wrench to the third

 

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segment while impacting the stem to avoid having the stem advance too far into the tibia.

 

 

 

TECH FIG 7 • (continued) D. Stem components inserted, waiting for wrench to be attached before tapping stem up into tibia. E. AP view of stem just before wrench is attached and stem is pushed up into tibia.

 

 

Repeat the steps to attach the fourth segment to the third segment. Add additional segments as needed. We typically use four segments.

 

The final segment is different from the others in that it houses the female portion of the Morse taper. It also has a small hole that indicates proper rotation. Be sure this segment is aligned and rotated properly. Then the entire stem is fully seated with its corresponding wrench using the rod impactor.

Tibial Base Plate

 

Introduce the tibial base plate into the joint (TECH FIG 8A).

 

Withdraw the rod impactor from the stem slightly, allowing the tibial base plate to be positioned, and then use the rod impactor to secure the base plate to the stem. The tibial base plate is secured to the stem by means of a Morse taper (see TECH FIG 8A).

 

Once the Morse taper is secured, remove the wrench on the stem and the composite base plate and stem combination is ready to be fully seated. Make sure there is enough room for the base plate, and trim out any bone on the sides, which could lead to a malleolus fracture (TECH FIG 8B).

 

 

 

TECH FIG 8 • A. Base plate of tibial component being inserted onto base of stem. Note male Morse taper.

B. Trimming away of bone using small reciprocating saw to ensure final fit. C. Base plate with stem being tapped up into tibia.

 

 

During this step, rotation of the tibial component must be controlled. A narrow handle attaches to the anterior aspect of the base plate to control rotation as the tibial component is impacted. When the component is fully seated, it should rest snugly in the mortise (TECH FIG 8C).

 

If the stem is not in the proper varus-valgus orientation, the small reciprocating saw may be taken and a small sliver of bone removed from the concave side (the side to which the stem is leaning). Then the impactor can be used to impact that side superiorly, correcting any malalignment.

Talar Component

 

This may be the most challenging step of the procedure, particularly if the joint was distracted to minimize bone resection or to correct deformity. In this situation, the joint space is quite tight by design to achieve optimal soft tissue balance and ligament tension.

 

14

 

 

 

TECH FIG 9 • Talar component insertion. A. Protective sleeve placed to protect tibial component. B. Talar component insertion with dedicated handle. C. Talar impactor. D. Note that in this case, the 10-mm stem (attached to the talar component on the back table) is used to optimize talar component stability. Some surgeons do not use the central stem, relying solely on the two anterior pegs for talar component stability.

 

 

We routinely assemble a 10-mm stem to the talar dome component on the back table for the size 2 and 3 prosthesis, using the dedicated assembly device to secure the Morse taper.

 

Typically, a 14-mm stem is too long to be connected to the talar dome component before implantation. Therefore, we place the 14-mm talar stem first for size 4 and up if there is enough depth to the talus and

seat it to the thin rib wrench that is flush with the prepared talar surface. Because the Morse taper has not been secured, the rib wrench must remain under the 14-mm talar stem.

 

The joint must then be gently distracted with a lamina spreader, followed by insertion of the talar dome component. A protective plastic sleeve inserted onto the tibial base plate protects the talar dome from being scratched (TECH FIG 9A). The toothless lamina spreader may need to go under the talar dome component to obtain the distraction while the talar component is carefully forced posteriorly into position. A handle attached to the talar dome component facilitates driving the talar dome posteriorly (TECH FIG 9B).

 

Once the talar dome component seats on the pegs and with or without the stem, the talar dome impactor is used to fully seat the talar component (TECH FIG 9C,D).

 

Remove the rib wrench and inspect the interface between talar dome and stem to ensure that the two talar components are securely attached. Use the impactor to fully seat the talar component.

 

While impacting the talar component, use the handle that inserts into the talar dome to control subtle changes in rotation of the talar component.

Polyethylene Insertion

 

The polyethylene trials determine optimal polyethylene thickness (TECH FIG 10).

 

We routinely remove the leg from the leg holder and obtain AP and lateral fluoroscopic images at this stage to confirm proper position and balance of the components.

 

With the ankle in neutral position, there should be a balance with varus and valgus stress. If not, the polyethylene thickness may be inappropriate or, more likely, balance needs to be established. Typically, the medial joint (deltoid ligament) is too tight. Traditionally, we have performed a lateral ligament reconstruction (modified Brostrom or Brostrom-Evans); however, in our more recent experience, we have been successful in rebalancing the ankle with a deltoid ligament release (described earlier) and increasing the polyethylene thickness.

 

 

 

TECH FIG 10 • Polyethylene trial placed to determine optimal final thickness of final polyethylene component to provide satisfactory coronal plane stability and sagittal plane motion.

 

 

15

 

The ankle should dorsiflex to at least 5 degrees, preferably 10 degrees beyond neutral. If not, the

polyethylene thickness may be too thick. If the polyethylene thickness is appropriate and the foot cannot be dorsiflexed to 90 degrees, consider a gastrocnemius recession or percutaneous tendo Achilles lengthening.

 

Using the dedicated polyethylene insertion device (TECH FIG 11A), insert the polyethylene. In our experience, the polyethylene will engage the tibial base plate's locking mechanism most effectively with the following maneuvers:

 

Have an assistant or cosurgeon distract the joint. During the initial portion of the insertion, gently pull the insertion device into slight plantarflexion, thus driving the polyethylene into the tibial base plate's locking mechanism (TECH FIG 11B).

 

 

 

TECH FIG 11 • Final polyethylene insertion. A. Temporary stem attached to tibial component and polyethylene positioned on dedicated insertion device. B. With assistant applying joint distraction, surgeon inserts polyethylene with dedicated insertion device. C. Close-up view of polyethylene insertion.

D. Final components in place. Final fluoroscopic AP (E) and lateral (F) views.

 

 

Once the polyethylene has cleared the superior dome of the talar component, ease off on the plantarflexion of the insertion device and have the assistant or cosurgeon compress the joint, thereby forcing the polyethylene into the locking mechanism (TECH FIG 11C).

 

Remove the insertion device and fully seat the polyethylene with the dedicated impactor. With that accomplished, the prosthesis should be fully seated (TECH FIG 11D).

 

Obtain final AP and lateral fluoroscopic views of the valgus ankle (TECH FIG 11E,F).

• Closure

  Thoroughly irrigate the joint and implant with sterile saline. Reapproximate the capsule. We routinely use a drain.

  Release the tourniquet and obtain meticulous hemostasis.

  Reapproximate the extensor retinaculum while protecting the deep and superficial peroneal nerves. Irrigate the subcutaneous layer with sterile saline and then reapproximate it.

  Reapproximate the skin to a tensionless closure.

  Apply sterile dressings on the wounds, adequate padding, and a short-leg cast with the ankle in neutral position.

   

   

  16

  PEARLS AND PITFALLS
  	Equinus ▪ Because the initial tibial and talar preparation is performed using a single contracture monoblock cutting guide, an equinus contracture will lead to excessive and undesired resection from the posterior talus. Therefore, perform a gastrocnemius recession or tendo Achilles lengthening to get the talus in a neutral position before securing the leg in the leg holder. If the heel does not rest fully on the leg holder's foot plate with the toes touching the foot plate, there is equinus.     Rotation ▪ The foot and leg may be well positioned in the leg holder and fluoroscopy may suggest proper alignment, but the ankle may still be malrotated, leading to symmetric but malrotated tibial and talar preparation. Place a thin osteotome in the medial gutter of the tibiotalar joint to determine optimal rotation; the osteotome should be parallel to the side of the leg holder.     Varus ankle ▪ Balance the ankle before placing it into the leg holder. For varus, perform the and valgus medial release; for valgus, the ankle is usually loose and simply needs the lamina malalignment spreader to realign the talus within the ankle mortise.     Place the ▪ The ankle must be in the center of the monitor or alignment cannot be accurately ankle at the determined. Therefore, first place the ankle in the center of the fluoroscopic beam, center of the and then make adjustments. Note also that as adjustments are made to the fluoroscopic operating table to optimize alignment, the ankle may “drift” from the center of the monitor. monitor and will need to be recentered in the fluoroscopic beam while alignment is being set.     Be sure ▪ Assessing the position of any instrument fluoroscopically demands that proper alignment is alignment has been confirmed first. For example, when positioning the cutting block proper relative to the reference drill, first check that alignment is perfect, and then assess before any the cutting block position. reading is made off the fluoroscopy.     Returning ▪ The stop on the side of the leg holder must be set before the ankle is plantarflexed

   

   

  the ankle to neutral position while it is in the leg holder

  with the frame or else it is difficult to return to the same neutral position.

   

  Morse taper ▪ The tibial base plate and the talar dome components attach to their respective stems with Morse tapers; be sure these are fully secured before seating either composite (combination main component and stem) fully.

   

  Insertion of talar component

  • May be difficult when joint distraction with lamina spreaders was used to minimize bone resection. However, judicious use of lamina spreaders is again possible to facilitate insertion of the talar component. When using a 10-mm talar stem, we typically have ample room to insert the combination of talar dome and stem composite that was attached on the back table; however, we usually have to independently insert the 14-mm stem followed by the talar dome component, securing the Morse taper within the joint. With the decreased working space necessitated by the anterior prongs on INBONE II, we rarely, if ever, use the 14-mm stem and, as already mentioned, have eliminated the talar stem completely in many situations.

 

POSTOPERATIVE CARE

 

Overnight stay

 

Nasal oxygen while in hospital

 

Touchdown weight bearing on the cast is permitted, but elevation is encouraged as much as possible. We tell patient to keep their “toes above their nose” to encourage proper elevation.

 

Follow-up in 2 to 3 weeks for cast change and suture removal. If the wound looks good, we advance patients to a removable boot with partial weight bearing.

 

The patient returns 6 weeks after surgery for cast removal if it was reapplied and weight-bearing radiographs of the ankle as well as 1-year follow-up (FIG 1).

 

OUTCOMES

Although some recently reported outcomes based on highlevel evidence, results of total ankle arthroplasty are almost uniformly derived from level IV evidence.

Functional outcome using commonly used scoring systems for total ankle arthroplasty (American Orthopaedic Foot and Ankle Society [AOFAS] [Kofoed, Mazur] and New Jersey Orthopaedic Hospital [NJOH] [Buechel-Pappas]) suggest uniform improvement in all studies, with follow-up scores ranging from 70 to 90 points (maximum 100 points).

Patient satisfaction rates for total ankle arthroplasty exceed 90%, although follow-up data for patient satisfaction often do not exceed 5 years.

 

 

 

 

FIG 1 • One-year follow-up weight-bearing radiographs. A. Mortise view. B. Lateral view demonstrating ankle dorsiflexion.

 

 

17

 

Our recent study on the INBONE ankle replacement showed a 93.8% survival, mean 3.7-year follow-up, designating removal of a metal component or conversion to arthrodesis as the end point.1

 

There was a direct correlation of avascular collapse of the talus in association with previous subtalar arthrodesis and concomitant subtalar and talonavicular arthrodesis. Many of these cases were done with the screws brought from anterior to posterior. Now, when a concomitant subtalar arthrodesis is warranted, we recommend preparation of the posterior facet of the subtalar joint only and using screws from posterior to anterior avoiding the talar vascularity in the sinus tarsi.

 

We also noticed cases of avascular collapse of the talus in which the only factor for injuring the blood supply to the talus was the 6-mm drill hole.

 

COMPLICATIONS

Infection (superficial or deep)

Neuralgia (superficial or deep peroneal nerve; rarely tibial nerve) Delayed wound healing

Wound dehiscence

Persistent pain despite optimal orthopaedic examination and radiographic appearance of implants Osteolysis

Subsidence

Malleolar or distal tibial stress fracture Implant fracture (including polyethylene)

 

 

 

REFERENCES

1. Adams SB Jr, Demetracopoulos CA, Queen RM, et al. Early to midterm results of fixed-bearing total ankle arthroplasty with modular intramedullary tibial component. J Bone Joint Surg Am 2014;96(23): 1983-1989.

    

    

2. Bonnin M, Judet T, Colombier JA, et al. Midterm results of the Salto total ankle prosthesis. Clin Orthop Relat Res 2004;(424):6-18.

    

    

3. Tennant J, Rungprai C, Pizzimenti M, et al. The effect of current total ankle arthroplasty methods on blood supply of the talus: a latex injection cadaver study with computed tomography and dissection analysis poster presentation. Presented at the American Orthopaedic Foot and Ankle Society Summer Meeting, July 17-20, 2013, Hollywood, FL.