Operative Techniques in Orthopaedic Surgery (4 Volume Set) 1st Edition

478. INBONE Total Ankle Arthroplasty

James K. DeOrio, Mark E. Easley, James A. Nunley II, and Mark A. Reiley

DEFINITION

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

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

images While 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.

images To achieve reliable intramedullary alignment, the INBONE™ 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.

ANATOMY

images Ankle

images Tibial plafond with medial malleolus

images Articulations with dorsal and medial talus

images In sagittal plane, slight posterior slope

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

images Fibula

images Articulation with lateral talus

images Responsible for one sixth of axial load distribution of the ankle

images Talus

images 60% of surface area covered by articular cartilage

images Dual radius of curvature

images Distal tibiofibular syndesmosis

images Anterior inferior tibiofibular ligament

images Interosseous membrane

images Posterior tibiofibular ligament

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

PATHOGENESIS

images Post-traumatic arthrosis

images Most common cause

images Intra-articular fracture

images Ankle fracture-dislocation with malunion

images Chronic ankle instability

images Primary osteoarthrosis

images Relatively rare compared to hip and knee arthrosis

images Inflammatory arthropathy

images Most commonly rheumatoid arthritis

images Other

images Hemochromatosis

images Pigmented villonodular synovitis

images Charcot neuroarthropathy

images Septic arthritis

NATURAL HISTORY

images Post-traumatic arthrosis

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

images Chronic lateral ankle instability may eventually be associated with:

images Relative anterior subluxation of the talus

images Varus tilt of the talus within the ankle mortise

images Hindfoot varus position

images Primary osteoarthrosis of the ankle is rare and poorly understood.

images Inflammatory arthropathy

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

images May be associated with chronic posterior tibial tendinopathy and progressive valgus hindfoot deformity, eventual valgus tilt to the talus within the ankle mortise, potential lateral malleolar stress fracture, and compensatory forefoot varus

PATIENT HISTORY AND PHYSICAL FINDINGS

images Patient history

images Often a history of ankle trauma

images Ankle fracture, particularly intra-articular

images Ankle fracture with malunion

images Chronic ankle instability (recurrent ankle sprains)

images Chronic anterior ankle pain, primarily with activity and weight bearing

images Ankle stiffness, particularly with dorsiflexion

images Ankle swelling

images Progressively increased pain with activity

images Physical findings

images Limp

images Patient externally rotates hip to externally rotate ankle to avoid painful push-off.

images Painful and limited ankle range of motion (ROM), particularly limited dorsiflexion

images Mild ankle edema

images Potential associated foot deformity

images Post-traumatic arthrosis secondary to chronic instability may be associated with varus ankle and hindfoot and compensatory forefoot varus.

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

IMAGING AND OTHER DIAGNOSTIC STUDIES

images Weight-bearing AP with contralateral ankle included, lateral, and mortise views of the ankle

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

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

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

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

images If we suspect avascular necrosis of the talus or distal tibia, we obtain an MRI of the ankle.

DIFFERENTIAL DIAGNOSIS

images See the “Pathogenesis” section.

NONOPERATIVE MANAGEMENT

images Activity modification

images Bracing

images Ankle–foot orthosis

images Double upright brace attached to shoe

images Stiffer-soled shoe with a rocker-bottom modification

images Nonsteroidal anti-inflammatories or COX-2 inhibitors

images Medications for systemic inflammatory arthropathy

images Corticosteroid injection

images Viscosupplementation

SURGICAL MANAGEMENT

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

images While 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.

images To achieve reliable intramedullary alignment, the INBONE™ 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.

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

images 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

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

images Noninvasive vascular studies and potential vascular surgery consultation if necessary

images 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.

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

images 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.

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

images Ankle ROM is determined.

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

images Anterior tibiotalar exostectomy

images Posterior capsular release

images Occasionally, tendo Achilles lengthening

images Instrumentation

images These instruments facilitate total ankle arthroplasty:

images Small oscillating and reciprocating saws for fine cuts as well as larger oscillating saw for broad bone cuts. The smaller saws make it easier to resect prominences with precision, and easily morselize large bone fragments to be evacuated from the joint.

images A rasp for final preparation of cut bony surfaces

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

images A toothed lamina spreader to distract the joint and aid in realignment of preoperative ankle deformity. Since the INBONE™ 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.

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

images Large fluoroscopic scanner

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

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

images With the leg holder, the large scanner is necessary to straddle the leg and leg holder.

images Fluoroscopy through the operating table is necessary, so a little fluoroscopy unit is inadequate.

images Foot pedals to make adjustments to the table position

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

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

Positioning

images Supine

images Plantar aspect of operated foot at end of operating table

images Foot and ankle well balanced with toes directed to the ceiling

images A bolster under the ipsilateral hip prevents undesired external rotation of the hip.

images We routinely use a thigh tourniquet and regional anesthesia.

images 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.

images 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.

images The operative extremity needs adequate space for the INBONE™ leg holder. The surgeon should be sure the opposite extremity is not secured too close to the operative extremity.

Approach

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

TECHNIQUES

APPROACH

images  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.

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

images  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.

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

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

images  We then expose the extensor retinaculum, identify the course of the EHL tendon, and sharply but carefully divide the retinaculum directly over the EHL tendon.

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

images 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.

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

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

images  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.

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

images  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.

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

images

TECH FIG 1  In this case there is no separate sheath for the tibialis anterior (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.

TIBIOTALAR ALIGNMENT

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

images  Varus malalignment

images We routinely perform a comprehensive medial release for moderate to severe varus malalignment.

images The concept is similar to balancing the varus knee for total knee arthroplasty and was well described by Bonnin et al.1 in their 2004 report of the Salto prosthesis.

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

images 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.

images 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.

images 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.

images  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 seldom 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 2BD). This marks a significant change from our initial practices in rebalancing the varus ankle.

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

images  Valgus malalignment

images Likewise, a valgus malalignment must be rebalanced.

images However, in our experience, we rarely need to perform a ligament release.

images 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.

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

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

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

images

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). 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.

INTRAMEDULLARY ALIGNMENT

images  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).

images  The foot and lower leg are secured in the leg holder.

images 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).

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

images Proper rotation

images  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.

images Plantigrade foot

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

images   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.

images  Coronal plane alignment

images In the mediolateral plane, center the heel over the starting point for the reference drill.

images We use the AP alignment guides to grossly set this alignment.

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

images Preoperative deformity complicates such preliminary alignment.

images  Sagittal plane alignment

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

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

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

images  Fluoroscopic confirmation of proper alignment

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

images



images

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.

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

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

images  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.

images  Reference drill

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

images   1 cm allows for subtle adjustments to the medial and lateral position of the reference drill, even when its drill sleeve has been positioned on the plantar calcaneus.

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

images Insert the drill guide to contact the plantar calcaneus.

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

images   Secure the drill guide.

images Advance the reference drill from calcaneus to tibia.

images   Since 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.

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

images Since drilling may shift the frame slightly, fluoroscopic confirmation of proper alignment must be re-established, after which proper alignment of the reference drill may be confirmed.

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

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

TIBIOTALAR JOINT PREPARATION

images  Sizing

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

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

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

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

images   In the lateral plane, we use saw blades through the cutting guide to determine the resection level (TECH FIG 4B).

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

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

images  Pinning the cutting block

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

images   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.

images   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.

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

images   Their mediolateral position is determined on the fluoroscopic image of the final cutting block position.

images   These pins protect the malleoli.

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

images

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.

images   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.

images  Withdraw the axial reference drill.

images  Anti-rotation drill

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

images  Bone resection

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

images 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.

images Once the posterior cortex has been penetrated for all cuts, the cutting guide and its pins can be removed.

images  The resected bone is evacuated from the joint.

images A toothless lamina spreader may be used to facilitate accessing the most posterior bone.

images Avoid levering on the malleoli with the instruments, as they may break.

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

images 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.

images  Tibial reaming

images 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.

images Advance the reamer. We typically use four segments for the stem extension; this requires reaming 55 mm into the tibia.

images 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.

images  Talar preparation

images Secure the talar alignment guide sleeve to the plantar aspect of the foot plate.

images Advance the talar positioning guide through this sleeve to the prepared talar surface.

images

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

images  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.

images  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). The pin can then be placed through the talar trial and will then be in the ideal position. The talar trial is positioned on the talar pin and a lateral fluoroscopic view confirms that the talar component will be in the desired position.

images  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. In the radiograph shown in Techniques Figure 6B, the component and talar pin are too far posterior. The talar trial and pin were moved anteriorly before drilling the talar stem hole. The new correct position is seen on the intraoperative films at the end of the case (TECH FIG 6C).

images  This also determines which of the two stem sizes is to be used. 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. For the 14-mm stem, we typically place this stem first and then attach the talar dome separately.

images  Remove the talar trial and ream the talar stem guide pin to either 10 mm or 14 mm (TECH FIG 6D).

images

TECH FIG 6  A. Talar component trial with hole and talar stem guide pin through it to determine position of stem. B. Cannulated drill being used over guide pin to create hole for stem. C. Lateral view of talar component with the talar stem guide through it. The guide and prosthesis are too far posterior and were brought forward. D. Final intraoperative lateral view showing that the prosthesis was moved forward and is in the correct position.

COMPONENT IMPLANTATION

images  Assemble the tibial stem within the joint.

images 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).

images Return the ankle to the neutral position in which the tibia was reamed and introduce the “X-screw driver” 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.

images Using the X-screw driver 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.

images Remove the X-screw driver 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 segment while impacting the stem to avoid having the stem advance too far into the tibia.

images

TECH FIG 7  A. The foot is plantarflexed to allow insertion of the cone piece with one mid-stem cylinder attached. B. Wrench holding already inserted pieces in place while another mid-stem component is being inserted. C. X-screw driver being inserted into stem component to screw it in place. 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.

images

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.

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

images 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.

images  Tibial base plate

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

images 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 (TECH FIG 8A).

images 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).

images 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).

images  Talar component

images In our opinion, this is 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.

images 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.

images 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 (TECH FIG 9). Since the Morse taper has not been secured, the rib wrench must remain under the 14-mm talar stem.

images The joint must then be gently distracted with a lamina spreader, followed by insertion of the talar dome component. 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. A protective plastic sleeve inserted onto the tibial base plate protects the talar dome from being scratched.

images

TECH FIG 9  Fourteen-millimeter stem inserted first with rib wrench underneath and component impacted onto stem. Rib wrench prevents stem from being impacted before Morse tape is seated. Plastic trial protects talar dome surface.

images

TECH FIG 10  Trial in place to determine final thickness of final polyethylene component.

images Once the talar dome component seats on the stem, use the talar dome impactor to secure the Morse taper, with the rib wrench still between the talar dome component and the prepared talar surface.

images 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.

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

images  Polyethylene insertion

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

images 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.

images  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 BrostromEvans); however, in our more recent experience, we have been successful in rebalancing the ankle with a deltoid ligament release (described above) and increasing the polyethylene thickness.

images  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.

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

images Have an assistant or co-surgeon distract the joint.

images 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.

images 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 co-surgeon compress the joint, thereby forcing the polyethylene into the locking mechanism.

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

images  Obtain final AP and lateral fluoroscopic views of the valgus ankle (TECH FIG 12).

images

TECH FIG 11  A. Polyethylene insertion device that screws down and pushes polyethylene onto tibial component tracks. B. Final component in position.

images

TECH FIG 12  A, B. Final AP and lateral films taken in the operating room showing correction of initial valgus deformity.

CLOSURE

images  Thoroughly irrigate the joint and implant with sterile saline.

images  Reapproximate the capsule. We routinely use a drain.

images  Release the tourniquet and obtain meticulous hemostasis.

images  Reapproximate the extensor retinaculum while protecting the deep and superficial peroneal nerves.

images  Irrigate the subcutaneous layer with sterile saline and then reapproximate it.

images  Reapproximate the skin to a tensionless closure.

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

images

images

POSTOPERATIVE CARE

images Overnight stay

images Nasal oxygen while in hospital

images Touch-down weight bearing on the cast is permitted, but elevation is encouraged as much as possible.

images Follow up in 2 to 3 weeks for cast change and suture removal

images The patient returns 6 weeks after surgery for cast removal and weight-bearing radiographs of the ankle.

OUTCOMES

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

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

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

images Overall survivorship analysis for currently available implants, designating removal of a metal component or conversion to arthrodesis as the endpoint, ranges from about 90% to 95% at 5 to 6 years and 80% to 92% at 10 to 12 years.

images At the time of this writing there are no published results available for the INBONE™ total ankle arthroplasty.

COMPLICATIONS

images Infection (superficial or deep)

images Neuralgia (superficial or deep peroneal nerve; rarely tibial nerve)

images Delayed wound healing

images Wound dehiscence

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

images Osteolysis

images Subsidence

images Malleolar or distal tibial stress fracture

images Implant fracture (including polyethylene)

REFERENCES

1. Bonnin M, Judet T, Colombier JA, et al. Mid-term results of the Salto total ankle prosthesis: report of 98 cases with minimum two years follow up. Clin Orthop Relat Res 2004;424:6–18.

2. Gougoulias N, Khanna A, Maffulli N. How successful are current ankle replacements? A systematic review of the literature. Clin Orthop Relat Res 2010;468:199–208.

3. Haddad SL, Coetzee JC, Estok R, et al. Intermediate and long-term outcomes of total ankle arthroplasty and ankle arthrodesis: a systematic review of the literature. J Bone Joint Surg Am 2007;89A:1899–1905.



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