DEFINITION

The Salto Total Ankle Prosthesis (Tornier SA, Saint- Ismier, France) is a cementless resurfacing-type implant that is intended to restore near-normal joint kinematics. Fixation is achieved through bone ingrowth.

The surgical technique is critical to a successful outcome, and some criteria are essential:

Tight fit of the components and extended contact area with bone to achieve good primary stability, which is a prerequisite for secondary biologic fixation

Restoration of the mechanical axis of the ankle

Accurate restoration of the joint line (proper level and strict horizontal plane) Preservation or restoration of the soft tissue balance

Adequate soft tissue release to achieve good range of motion (ROM) intraoperatively

 

 

ANATOMY

The Mobile-Bearing Salto Prosthesis

 

The Salto Total Ankle Prosthesis (Tornier SA) was developed between 1994 and 1996 and has been used clinically since January 1997 (FIG 1).

 

Based on experience with the third-generation cementless meniscal-bearing designs, this system was designed to restore nearly normal kinematics of the ankle.

 

A dedicated instrument system was developed to achieve optimal positioning of the components, and the design of the implant was optimized to better restore the natural anatomy and obtain an optimal primary fixation of the components while retaining a minimally invasive resurfacing concept.

 

The tibial component accommodates the superior flat surface of the mobile bearing. Its smooth surface allows free translation and rotation of the mobile bearing. The 3-mm medial rim protects the polyethylene from impingement with the medial malleolus.

 

The specific shape (segment of a cone of revolution) of the talar component replicates the anatomy of the talar dome. It is broader anteriorly than posteriorly, and the lateral condyle has a larger radius of curvature than the medial condyle (FIG 2).

 

As a result, the axis of flexion and extension of the talar component, under the polyethylene, is aligned with the physiologic axis.

 

The lateral aspect of the talus is resurfaced, allowing articulation with the lateral malleolus.

 

The ultra-high-molecular-weight polyethylene (UHMWPE) insert articulates with the tibial component superiorly

and with the talar component inferiorly. It maintains full congruency with the talar component in flexion and extension and accommodates as much as 4 degrees of varus and valgus in the coronal plane, thereby reducing the chance of polyethylene edge loading.

 

The tibial component is available in three sizes and the talar component is available in four sizes. The mobile bearing is sizematched to the talar component in thicknesses from 4 to 8 mm.

 

The mobile-bearing size must match the size of the talar component. The talar component must be equal to or one size less than the tibial component.

 

Primary fixation to the tibia is ensured by close match of the tibial component to the epiphysis and enhanced by an anteroposterior (AP) keel and a tapered cylindrical plug.

 

Stability of the talar component is provided by three bone cuts and insertion of an 11-mm diameter hollow fixation peg into the body of the talus.

 

 

 

 

FIG 1 • A. An oblique view shows the Salto Total Ankle Prosthesis. B. An AP view shows the three main components and the malleolar component.

 

 

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FIG 2 • AP (A) and lateral (B) radiographs show the Salto Total Ankle Prosthesis in situ.

 

 

Secondary fixation is provided by bone ingrowth into a dual coating of hydroxyapatite applied to a 200-γm thick layer of plasma-sprayed titanium.

 

The Fixed-Bearing Salto-Talaris Prosthesis

 

Our experience with the Salto prosthesis has led us to revise our concept of mobility. Because of the anatomic design of the implant, the precision of the bone cuts, the accuracy in component positioning, and the need for and the potential problems associated with postoperative motion of the polyethylene bearing during flexion-extension movements have been almost completely eliminated. This has been confirmed in clinical studies based on standing dynamic views. On the other hand, intraoperative motion of the tibial component assembly is most helpful in allowing self-positioning of the bearing with respect to the talar component before the tibial keel preparation is completed.

 

The Salto-Talaris components and instrument system are the same as those of the Salto prosthesis, except that the tibial component is a fixed-bearing design (FIG 3).

 

Polyethylene is attached to tibial component prior to insertion.

 

The final position of the tibial component is fine-tuned at the end of the procedure to achieve perfect alignment with the talar component. In this manner, the self-positioning feature of the mobile-bearing insert has been retained.

 

PATHOGENESIS

 

In general, our indications for total ankle arthroplasty (TAA) are end-stage ankle osteoarthritis (OA) or rheumatoid arthritis (RA).

 

 

 

FIG 3 • The Salto-Talaris components and instrument system are the same as those of the Salto prosthesis, except that the tibial component is a fixed-bearing design.

 

 

In OA, degeneration may be due to sequelae of trauma, chronic ankle instability, and rarely primary OA.

 

In our experience, RA occurs relatively infrequently in the ankle when compared to the hip or knee. However, there is no consensus on the actual rate of ankle joint involvement in RA patients, with figures ranging from 9% in the study by Vainio, in which clinical criteria were used, to 40% in the study by Jakubowski et al, which employed radiographic criteria.

 

Occasionally, end-stage erosive or degenerative changes of the ankle may develop secondary to osteochondromatosis, pigmented villonodular synovitis, hemochromatosis, or osteochondritis dissecans.

 

Ankle joint involvement in RA tends to occur late in the disease process, with symptoms not occurring until a mean disease duration of 17 to 19 years.

 

Because the tibiotalar joint is rarely affected in isolation, treatment will need to be systemic and not only for the ankle.

NATURAL HISTORY

 

Progressive tibiotalar arthritis typically is accompanied by progressive ankle stiffness. Loss of ankle ROM, particularly dorsiflexion, results from tibiotalar osteophytes and less resilience in the distal tibiofibular syndesmosis.

 

Over time, the patient may develop an equinus gait with resultant Achilles tendon contracture, posterior capsular adhesions, and, occasionally, tibialis posterior adhesions.

PATIENT HISTORY AND PHYSICAL FINDINGS

 

Silfverskiöld test

 

Passive ankle ROM with the patient supine and the knee flexed and extended

 

Physiologic ROM with this examination is 15 degrees dorsiflexion or 0 to 40 degrees plantarflexion.

 

An isolated gastrocnemius contracture is present when lack of dorsiflexion with the knee in extension is

eliminated with knee flexion.

 

Evaluation of ankle ROM with the patient standing and walking

 

Visualizing the gait pattern. The patient may externally rotate the extremity, or female patients may be able to walk in high heels to mask the lack of ankle dorsiflexion.

 

Hindfoot ROM

 

We use three grades of hindfoot motion: physiologic, diminished, or stiff. We favor TAA over ankle arthrodesis in patients with a stiff hindfoot.

 

Hindfoot alignment with the patient standing or ambulating

 

Hindfoot malalignment (varus or greater than physiologic valgus) may be most pronounced with the patient walking.

 

Hindfoot alignment with the patient supine

 

We typically assess passive hindfoot motion to determine if the deformity can be reduced to a physiologic position. In our hands, this examination determines the type of hindfoot realignment that will be performed concomitant to TAA.

 

Tibiotalar instability

 

The examiner successively assesses coronal plane and sagittal plane stability with varus-valgus stress and anterior drawer testing, respectively. In our hands, varus instability or fixed varus ankle requires careful ligament balancing.

 

IMAGING AND OTHER DIAGNOSTIC STUDIES

 

In our preoperative assessment, we not only determine the extent of deformity and instability at the ankle but also

 

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assess any concomitant ipsilateral lower extremity malalignment that may have a bearing on the outcome of TAA.

 

We routinely obtain weight-bearing AP, mortise, and lateral radiographs of both ankles; radiographs of the uninvolved ankle typically provide some understanding of what is physiologic for the patient. Weight-bearing mechanical axis hip-to-ankle radiographs are required if there is associated deformity of the ipsilateral lower extremity.

 

We recommend obtaining computed tomography (CT) scans of the ankle and hindfoot, particularly to review coronal sections, to further evaluate tibial or talar bone loss or cysts not fully defined on plain radiographs.

 

DIFFERENTIAL DIAGNOSIS

Septic arthritis

Charcot neuroarthropathy

 

 

NONOPERATIVE MANAGEMENT

 

 

We have had limited success with nonoperative management in active patients with end-stage ankle arthritis. Activity modification, rocker bottom shoe modification, and bracing offer some relief.

 

We reserve nonoperative management for low-demand patients who are poor surgical candidates.

 

SURGICAL MANAGEMENT

Total Ankle Arthroplasty versus Ankle Arthrodesis

 

 

 

In general, arthrodesis is favored over TAA because of the following: Lower risk of mechanical implant failure; no risk of implant wear Lower risk of infection

 

Less chance of skin necrosis when the ankle has been previously operated on

 

In our hands, lower incidence of residual pain

 

 

In general, TAA is favored over ankle arthrodesis because of the following: Less risk of developing adjacent (hindfoot) joint arthritis

 

In our hands, more favorable functional outcome

 

In our opinion, malunion or development of adjacent joint arthritis makes revision surgery more difficult after arthrodesis.

 

Preoperative Planning

 

Preoperative evaluation of weight-bearing radiographs and CT scan to:

 

Choose the optimal implant size, with the use of available templates. This is important because an oversized prosthesis will alter the center of rotation, giving rise to pain and stiffness.

 

If the talus is particularly deformed, the template should be applied to the contralateral, unaffected ankle.

 

Determine the reference for establishing the ideal tibial resection level, taking into account the extent of wear in the tibial plafond.

 

Analyze tibiotalar joint alignment relative to the tibial shaft axis. This allows differentiation between axial deviations:

 

 

Resulting from asymmetric wear of the tibial plafond that may be corrected with tibial preparation Because of malunion that may require corrective osteotomy, simultaneous to or staged with TAA

 

Analyze the residual talar body.

 

Asymmetry needs to be balanced in the talar preparation.

 

Evaluate the hindfoot.

 

A joint-sparing calcaneal osteotomy may be necessary to realign the hindfoot.

 

In the face of hindfoot arthritis or hindfoot instability, a subtalar or even triple arthrodesis may be warranted.

 

Positioning

 

The patient is positioned supine on the operating table, with a pad under the ipsilateral hip to promote a neutral tibial and foot alignment with the foot pointing to the ceiling.

 

The plantar aspect of the foot should be flush with the end of the table.

 

 

Placing a rolled towel under the ankle facilitates subtle adjustments in ankle positioning. We routinely use a thigh tourniquet.

 

 

In our experience, a pillow placed behind the knee allows the Achilles tendon to relax and may improve exposure. We recommend including the knee in the sterile field so that the limb can be positioned more freely and so that the

patella and tibial tubercle may be used to confirm optimal alignment. The surgeon stands at the foot of the table, with the assistant at the lateral side of the operative leg.

 

TECHNIQUES

• Exposure

   

  The tibiotalar joint is approached through an anterior midline incision starting 8 to 10 cm proximal to the joint line and extending to the midfoot.

   

  The soft tissues must be handled carefully, especially in patients being managed with systemic steroid treatment.

   

  The surgeon should avoid undermining the skin.

   

   

  The surgeon should maintain deep retraction only and avoid tension directly on the skin edges. Extending the skin incision will further diminish skin tension.

   

  Although we maintain meticulous hemostasis, we ligate vessels whenever possible and use electrocautery sparingly to diminish the risk of skin burns. We typically incise the crural fascia and extensor retinaculum along the lateral border of the tibialis anterior tendon, using the interval between the tibialis anterior and extensor hallucis longus (EHL) tendons.

   

  Whenever possible, the tibialis anterior tendon should remain protected in its individual sheath throughout the procedure (this also separates the tendon from the anterior incision during closure).

   

  Alternatively, the extensor retinaculum may be incised at the lateral border of the EHL tendon, using the interval between the EHL and extensor digitorum longus tendons. The tendons are retracted with angled retractors, and the deep neurovascular bundle (anterior tibial artery and deep peroneal nerve) is identified in the proximal wound and carefully reflected laterally.

   

  The periosteum and joint capsule are incised longitudinally. The medial and lateral flaps are elevated using a scalpel and an

   

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  elevator to expose the tibiotalar joint to the anterior margins of the malleoli.

   

  To avoid direct tension on the skin margins, we use deep retractors, one at the proximal aspects of each malleolus.

   

  Anterior osteophytes are removed with an osteotome, and the talar facets are cleared with a rongeur.

   

  We then define the physiologic aspects of both malleoli, removing any osteophytes, ossifications, and loose bodies that obscure visualization of the medial and lateral ankle gutters, distort the natural anatomy, or impinge on the talus (TECH FIG 1).

   

  Upon completion of these steps, the talus should be mobile and the medial and lateral gutters should be fully exposed.

   

   

   

  TECH FIG 1 • A lateral retractor is placed against the lateral malleolus and a medial retractor against the upper part of the medial malleolus. Anterior osteophytes are removed with an osteotome, and the talar facets are cleared with a rongeur.

• Tibial Resection

 

The goal is to restore a physiologic tibiocalcaneal axis. Ideally, implant position should produce a joint line at right angles to the mechanical tibial axis in the coronal plane and reproduce the physiologic 7-degree posterior slope in the sagittal plane.

 

Align the extramedullary guide with the anterior tibial crest or a line joining the center of the knee and the midpoint of the distal tibial surface.

 

Proximally, secure the alignment guide to the anterior tibial tuberosity with a self-drilling pin, roughly perpendicular (in the sagittal plane) to the malleolar tips and distal medial tibial metaphysis in the sagittal plane (TECH FIG 2).

 

We then perform five sequential adjustments.

 

 

 

TECH FIG 2 • A,B. Left ankle. The extramedullary guide is aligned with the anterior tibial crest. It is attached with self-drilling pins at the anterior tibial tuberosity, roughly perpendicular (in the sagittal plane) to the malleolar tips, and then at the distal medial metaphysis of the tibia. Resection is performed using the extramedullary guide, referencing off the anterior tibial border. A few degrees of axial deviation of the knee joint in the coronal plane can be compensated for by using the proximal holes (arrows) to obtain a perfect adjustment and to perform a bone cut that will be almost horizontal.

Orientation in the Coronal Plane

 

Provided there is anatomic or near-anatomic overall alignment of the lower extremity, the tibial cut should be horizontal and perpendicular to the tibial axis (TECH FIG 3).

 

Perform resection using the extramedullary guide referencing off the anterior tibial border.

 

A few degrees of coronal plane deviation proximal to the ankle or at the knee is readily compensated by realigning the proximal aspect of the external tibial alignment guide on the pin placed in the tibial tubercle. However, in our experience, moderate to severe deformity proximal to the ankle should be corrected before TAA, typically in a staged fashion.

 

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TECH FIG 3 • In the coronal plane, provided there is a good overall alignment of the lower extremity, the tibial cut should be horizontal and perpendicular to the tibial axis.

Orientation in the Sagittal Plane

 

The external tibial alignment guide, when positioned parallel to the anterior tibial cortex, establishes a physiologic posterior slope of 7 degrees for the tibial cut.

 

In our experience, to achieve correct angulation of the tibial cutting block, the extramedullary guide must rest on the tibia at both the proximal and distal ends.

 

 

 

TECH FIG 4 • A. The goal with the Salto is to restore an anatomic joint line level. Then, in the absence of significant bone wear, the amount of bone resection on the tibia must fit exactly with the thickness of the tibial components (metal baseplate plus polyethylene). B. The only reliable landmark is the plafond of the tibial pilon. The anterior margin of the tibial pilon is resected using an osteotome. This will provide direct exposure of the joint surface. From this reference level, the required cut is determined, aiming to remove as little bone as possible. (continued)

Resection Level

 

The goal is to restore an anatomic joint line level. When the subchondral architecture of the tibial plafond is intact, the amount of distal tibial resection should match the metal tibial baseplate plus the polyethylene insert.

 

We use the apex of the tibial plafond as the reference point for tibial resection. To expose this apex, we resect the anterior margin of the tibial plafond using an osteotome. With clinical inspection or fluoroscopic confirmation in the sagittal plane, the resection level is determined from this reference point (TECH FIG 4).

 

For the Salto (three-part mobile-bearing) prosthesis, the tibial resection is 7 mm (3 mm for the thickness of the metal baseplate plus 4 mm for the minimum thickness of the polyethylene).

 

For the Salto-Talaris (two-part fixed-bearing) prosthesis, the minimum resection is 8 mm (3 mm for the thickness of the metal baseplate plus 5 mm for the minimum thickness of the polyethylene). However, as a routine, we resect 9 mm, which allows for downsizing of the polyethylene in the event that the joint is too tight.

 

We modify the tibial cut based on the ligamentous tension in the ankle. In stiff ankles, we typically resect 2 mm more than the minimal resection; in ankles with instability, we generally resect 2 mm less than the minimal resection.

 

Bone loss in the tibia may warrant adjusting the tibial cut to reestablish the proper joint line.

Orientation in Rotation

 

Because both the tibial and initial talar cutting guides are suspended from the tibial alignment guide, thus linking the tibial and initial talar resection, proper rotational alignment is critical. Malrotation of the components may interfere with the implant's kinematics, create malleolar impingement, risk edge loading,

 

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and (particularly in the fixed-bearing Salto-Talaris) lead to increased constraint (TECH FIG 5).

 

 

 

 

TECH FIG 4 • (continued) C. Left ankle. The guide is adjusted at the level of the tibial pilon (small arrow) and this level is observed on the scale on the tibial alignment jig (large arrow and circle). D. Then, from the initial reference position, the guide is adjusted proximally from 7 to 9 mm according to the desired amount of resection (arrow and circle).

 

 

Although the mobile-bearing Salto implant may compensate for a certain degree of malpositioning, edge loading or overhang of the polyethylene on the metal tibial tray may result. Therefore, every effort should be made to orient the implant on the center bisecting line of the talus in the coronal plane, the line that is parallel with the talus when it is taken through its motion arc. We rotate the cutting guide until it is centered on the line bisecting the space between the medial and lateral talar facets.

 

Orienting the implant in line with the second metatarsal may be useful but introduces errors with associated midfoot or forefoot deformity.

Coronal Plane Positioning

 

The final adjustment is to center the cutting block on the tibial plafond, often necessitating medial or lateral translation of the cutting block relative to the tibial alignment guide. The propersize cutting block must be selected; the reference landmarks for sizing are the medial axilla and the lateral edge of the tibia.

 

Set the guide to avoid compromise of the malleoli. Secure pins within the cutting block at the level of resection to protect the malleoli from inadvertent saw blade excursion (TECH FIG 6A).

 

Bone resection

 

Before making the sagittal bone cuts (medial and lateral), drill holes through the appropriate-size cutting block and fully insert two short pins through the superior holes to protect the malleoli during resection. Before placing the protective pins, an AP radiograph may be obtained to confirm proper position and sizing of the cutting block in the coronal plane.

 

 

 

TECH FIG 5 • The rotational alignment is of critical importance even more so as the tibial and talar resections are linked. A. The talar component must be aligned with the axis of the talar dome (1) and is centered on the line bisecting the space between the medial and lateral talar facets (2 and 3). External (B) or internal (C) rotational malpositioning of the components will result in increased stress being placed on the fixation system, impingement with the malleoli, and may interfere with the kinematics of the joint replacement.

 

 

For a mobile-bearing Salto prosthesis, use the extramedullary guide to initially prepare for the tibial keel, as it sets the rotational alignment of the tibial component.

 

When implanting a Salto-Talaris prosthesis, the rotational alignment is established using the trials and ranging the ankle to allow the tibial base and insert assembly to selfcenter with respect to the trial talar component.

 

The capture guide on the cutting block guides the saw blade.

 

The tibial resection must be completed through the posterior cortex of the distal tibia, without plunging the saw blade into the posterior soft tissues.

 

We typically use a saw blade of adequate length and limited excursion.

 

Removing the resected bone

 

Remove the tibial cutting block but leave the external tibial alignment guide in position.

 

With a thin osteotome or small reciprocating saw, complete the two sagittal cuts through the predrilled holes created using the cutting block.

 

Remove the resected bone wafer.

 

The resected bone must be fully mobilized before attempting to extract it from the joint; abrupt mobilization of this bone may result in a fracture of the medial malleolus if the cut is not complete, especially in an ankle with an equinus contracture. The removal of the distal tibial resection is rarely done in one piece; usually piecemeal removal is required.

 

Remove the anterior half. With the Salto and Salto-Talaris prostheses, removal of the posterior portion may be delayed until after the posterior talar cut is completed (TECH FIG 6B).

 

 

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TECH FIG 6 • A. The instrument system provides accurate component positioning through adjustment of the resection level, translation, and rotation. Pins can be inserted in the medial and lateral holes of the guide to visualize the limits of the tibial cut with respect to the malleoli. Before the tibial cut is performed, holes are drilled through the appropriate-size cutting block and two short pins are fully inserted through the superior holes to protect the malleoli during resection (small arrows). B. The removal of the distal tibial resection is rarely done in one piece; usually, piecemeal removal is required. The anterior half is removed, and then removal of the posterior portion can be delayed until after the posterior talar cut is completed.

• Talar Preparation

 

Talar preparation requires that the ankle can be dorsiflexed to at least 90 degrees.

 

This angle is almost always obtained at this stage because the removal of bone from the tibia (anterior part of tibial resection) will have created more space, even in a stiff ankle.

 

In the rare case that it is not achieved, then an Achilles tendon lengthening or gastrocnemius-soleus recession may need to be considered.

 

Talar preparation comprises three cuts: posterior, anterior, and lateral. The native medial talar dome is left intact with this technique.

Posterior Talar Chamfer Cut

 

To position the talar component properly on the prepared talar dome, the posterior talar cut must be inclined 20 degrees posteriorly.

 

 

 

TECH FIG 7 • A. The talar pin setting guide (large arrow) is positioned on the distal end of the tibial guide. With the ankle positioned in neutral flexion, a pin is inserted through the hole into the talus (small arrow) (left ankle). B. The pin-guided resection is performed with an oscillating saw, taking care to keep the saw blade flat against the pin surface during resection.

 

 

With the ankle maintained at 90 degrees of dorsiflexion and the hindfoot in physiologic valgus position, suspend the talar guide from the external tibial alignment guide and insert a pin into the talus (TECH FIG 7A).

 

This pin dictates the sagittal orientation of the talar component.

 

This reference pin must be placed with the ankle in a strictly neutral position between flexion and extension.

 

 

Excessive dorsiflexion will lead to anterior and flexed positioning of the talar component. Excessive plantarflexion tilts the implant backward.

 

Secure the posterior chamfer talar cutting block on this reference pin.

 

Talar styli are available to determine the level for an anatomic resection that corresponds to the thickness of the talar component.

 

In case of severe flattening of the talar dome, this resection level may need to be adjusted. The talar resection level depends on having

 

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satisfactory fixation of the implant in healthy bone while simultaneously trying to preserve as much talar bone stock as possible.

 

The posterior chamfer cut of the talus should be anatomic, parallel to the superior margin of the talar dome.

 

Asymmetric wear must be recognized and the posterior talar chamfer cut adjusted appropriately; shims are available to make such adjustments.

 

We do not recommend compensating extra-articular or hindfoot deformity by means of an asymmetric posterior talar chamfer cut; instead, simultaneous or staged hindfoot correction should be performed.

 

The talar guide orients the placement of four pins in the talus that are then used to guide the talar resection. Maintain the oscillating saw flush with the dorsal aspects of the pins while protecting the malleoli from injury (TECH FIG 7B).

 

The residual tibial bone is relatively easy to extract at this point, along with the resected portion of talus. A lamina spreader without teeth, used judiciously, usually improves exposure.

Anterior Talar Chamfer Preparation

 

Anterior talar preparation contributes to the correct AP and rotational positioning of the talar component.

 

Perform the anterior chamfer cut with a milling device controlled by the anterior talar cutting guide, secured on the posterior resected surface (TECH FIG 8).

 

Adequate anterior resection is essential to avoid an anterior talar position relative to the tibia, a situation that may lead to increased anterior contact stresses and potential edge loading.

 

 

 

In our experience, the threshold to deepen the anterior chamfer preparation should be low. Removing anterior talar neck osteophytes allows the guide to be properly seated on the talus. Appropriate anterior chamfer preparation is determined using the talar gauge.

 

With respect to rotation, the guide must be perfectly aligned with the axis of the talar body. The second metatarsal may be used as a reference provided there is no associated foot malalignment.

Lateral Chamfer and Talar Stem Preparation

 

Proper positioning is essential.

 

In the sagittal plane, the guide should be positioned flush with the two previously resected surfaces, with no anterior overhang.

 

In the horizontal plane, rotation is determined with reference to the axis of the talar body.

 

In the coronal plane, correct mediolateral position is referenced from the lateral margin of the prepared talar dome.

 

Once correctly positioned, pin the cutting guide to the bone.

 

First, prepare the talar stem recession using the bell saw. Then, insert a dedicated metal peg into this prepared portion of talus to afford greater stability to the lateral talar chamfer cutting guide. Prepare the lateral chamfer using an oscillating or reciprocating saw.

 

 

 

TECH FIG 8 • The anterior chamfer cut is performed with an end mill cutter controlled by the anterior talar cutting guide, which is positioned on the posterior resected surface.

• Insertion of Trial Components

   

  The appropriate-size talar trial is that which provides good coverage of the talus in the mediolateral plane, without medial overhang.

   

  The talar trial lacks the plasma spray coating and thus lacks the interference fit of the actual talar implant; therefore, the talar trial may appear loose. To determine optimal polyethylene thickness and ligament balance, the talar trial remains in situ during insertion of the tibial trials.

   

  Salto mobile-bearing prosthesis

   

  Insert the selected trial tibial component flush with the bone cut; this will serve as a drill guide for creation of the press-fit hole for the tapered cylindrical plug.

   

  Insert the mobile bearing. Bearing thickness is crucial to the stability of the implant. A bearing of correct thickness will need to be pushed rather than slipped into the joint.

   

  Salto-Talaris fixed-bearing prosthesis

   

  Push the trial tibial base and insert assembly into position; it is free to rotate relative to the tibia.

   

  As the ankle is ranged from flexion to extension, the tibial trial locates its ideal position and rotation with respect to the talus, unless the tibial trial has essentially the same dimensions as the prepared tibial surface.

   

  When this automatic adjustment is obtained, the definitive position is determined.

   

  Perform preparation for the press-fit hole for the tapered cylindrical plug as described earlier for the Salto prosthesis.

   

  The use of a fixed or mobile bearing allows different sizes to be employed on the tibia and on the talus; when this option is being used, the choice of polyethylene size must be by the same size as the talar component.

   

  Range the joint and check stability. The implant should be stable in the coronal plane, without any residual laxity; dorsiflexion greater than 10 degrees should be readily obtained.

   

   

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• Insertion of the Definitive Components

   

  Insert the definitive components.

   

  The prosthesis must have sound initial stability, indicating appropriate ligament balance.

   

   

   

   

  TECH FIG 9 • After insertion of the tibial component, the anterior opening of the cortex (A) is filled with bone graft obtained from the bone cuts to prevent any ingress of joint fluid (B).

   

   

  Before impacting the components, any tibial or talar subchondral cysts or other bone defects may be filled with bone graft.

   

  Insert the talar component first.

   

  After inserting the tibial component, fill the anterior opening of the cortex with bone graft obtained from the bone cuts to prevent any ingress of joint fluid (TECH FIG 9), which may lead to osteolysis.

• Closure

   

  Because the skin over the ankle is very delicate, closure must be meticulous.

   

  Close the wound over an intra-articular drain. Whenever possible, close the capsule with absorbable sutures.

   

  Suture the fascia and retinaculum. Isolate the toe extensor tendons and particularly the tibialis anterior tendon from the fascial suture line.

   

   

  Close the loose subcutaneous tissue and the skin with interrupted sutures. Apply a below-knee plaster cast with the ankle in maximum dorsiflexion.

• Salto-Talaris Case Example (Courtesy of Mark E. Easley, MD)

Background

 

 

A 62-year-old woman with right ankle arthritis failed appropriate nonoperative treatment Ankle/hindfoot alignment in neutral; lacking physiologic valgus

 

Some associated hindfoot stiffness

 

Weight-bearing radiographs

 

Suggested slight varus at the ankle (TECH FIG 10A)

 

 

 

End-stage ankle arthritis with loss of the joint space (TECH FIG 10A-C) Large anterior osteophytes and suggestion of talar cysts (TECH FIG 10C) Hindfoot alignment in neutral (TECH FIG 10D)

 

 

CT suggested end-stage ankle arthritis with medial joint wear pattern (TECH FIG 10E). Despite radiographic appearance, no large talar cysts suggested (TECH FIG 10E,F)

Exposure

 

Longitudinal anterior incision over ankle (TECH FIG 11A)

 

 

Starting 1 cm lateral to tibial crest, approximately 8 cm proximal to ankle Extending to central midfoot approximately 4 cm distal to joint

 

Superficial peroneal nerve identified and protected throughout procedure (TECH FIG 11B)

 

Occasionally, there is one medial crossing branch immediately anterior to the ankle that needs to be sacrificed because it would be under tension and at risk for injury.

 

Extensor retinaculum exposed

 

Extensor retinaculum opened longitudinally over EHL tendon (TECH FIG 11C)

 

Deep neurovascular bundle identified, mobilized laterally, and protected throughout procedure (TECH FIG 11D,E)

Joint Preparation

 

 

Osteophytes removed (TECH FIG 12A,B) Distal anterior tibial resection

 

 

Osteophytes removed (TECH FIG 12C) Congruent resection recommended

 

Perpendicular to tibial shaft axis to facilitate orthogonal positioning of external tibial alignment guide (TECH FIG 12D,E)

 

Cutting the anterior distal tibial preparation to expose the tibial plafond is cut in varus may promote varus positioning of the external tibial alignment guide.

 

Tibial plafond exposed (TECH FIG 12F)

 

 

89

 

 

 

TECH FIG 10 • A 62-year-old woman with end-stage right ankle arthritis. A-D. Weight-bearing radiographs. A. AP view. B. Mortise view. Note medial ankle joint wear pattern with some varus malalignment. C. Lateral view. Note large anterior osteophytes and question of talar cyst formation. D. Hindfoot alignment view suggesting neutral heel position. E. Coronal CT demonstrates end-stage ankle arthritis and medial wear pattern. F. Sagittal view shows no obvious talar cysts, and no advanced subtalar arthritis is suggested.

 

 

 

TECH FIG 11 • A. Longitudinal anterior incision over ankle. B. Superficial peroneal nerve identified and protected throughout procedure. C. Extensor retinaculum opened longitudinally over EHL tendon. D. Deep neurovascular bundle identified. E. Deep neurovascular bundle mobilized laterally and protected.

 

 

90

 

 

 

TECH FIG 12 • A. Anterior osteophytes. B. Osteophytes removed with a rongeur. C-F. Anterior distal tibial preparation. C. Osteophytes removed. D. Reciprocating saw used to create a vertical relief cut. E. Anterior bone/osteophyte resection to expose ankle. F. Tibial plafond exposed.

Placing the External Tibial Alignment Guide

 

An osteotome may be placed in the medial gutter to use as a reference to align the proximal tibial (tubercle) pin from which the external tibial alignment guide will be suspended (TECH FIG 13A).

 

 

External tibial alignment guide positioned, centered over the tibial crest (TECH FIG 13B) External tibial alignment guide secured in distal medial tibia (TECH FIG 13C)

 

Slope properly adjusted

 

Traditional guide has 7 degrees of anterior opening if alignment guide placed parallel to tibial shaft axis.

 

Elevating the alignment guide proximally removes some of this slope to neutralize the tibial plafond cut (TECH FIG 13D).

 

Newer instrumentation will have less than 7 degrees of slope built into the system.

 

Rotation properly adjusted

 

With the talus moved in the sagittal plane, a reference pin suspended from the tibial alignment guide is used to orient the cutting block to match the talar axis (TECH FIG 13E).

 

Ideally, this will determine optimal rotation for the tibial cutting block.

Setting the Tibial Cutting Block

 

The tibial cut is set for 8 to 9 mm from the apex of the tibial plafond (TECH FIG 14A,B).

 

Proper tibial cutting block positioning confirmed fluoroscopically (TECH FIG 14C-E)

 

Provisionally, a pin is manually placed in the proximal medial aspect of the cutting guide to ensure that the cutting block is not placed too medially, risking weakening medial malleolar support (TECH FIG 14F).

 

Even if fluoroscopy suggest optimal position, clinical confirmation is recommended.

 

A simple lateral shift of the cutting block or downsizing the block protects the malleolus.

 

With the tibial cutting block in place, the two proximal pins are placed to protect the malleoli (TECH FIG 14G).

 

The additional holes are drilled to weaken the bone planned for resection, thereby facilitating the bone's removal (TECH FIG 14H).

 

Careful tibial preparation with the oscillating saw (TECH FIG 14I).

 

Avoid overpenetration with the saw blade posteriorly, as it will potentially risk injury to the flexor hallucis longus tendon and the posteromedial neurovascular bundle.

 

With the cutting block removed, the medial and lateral drill holes are connected with a small reciprocating saw (TECH FIG 14J).

 

The tibial plafond resection is mobilized and removed.

 

Rarely can the resected distal tibial bone be removed as one piece (TECH FIG 14K).

 

Using a lamina spreader (without teeth so the prepared tibial surface is protected), the residual posterior bone may be carefully morselized with the small reciprocating saw and the fragments removed using a 90-degree curette and rongeur (TECH FIG 14L,M).

 

 

91

 

 

 

TECH FIG 13 • External tibial alignment guide. A. Osteotome may be placed in medial gutter, serves as a

reference to align proximal tibial (tubercle) pin from which external tibial alignment guide is suspended. B. External tibial alignment guide centered over tibial crest. C. External tibial alignment guide secured in distal medial tibia. D. Elevating the alignment guide proximally removes some of this slope to neutralize the 7 degrees of anterior opening (slope) built into the traditional alignment guide (a new guide with less slope is to be released). E. Setting tibial cutting block rotation. With the talus moved in the sagittal plane, a reference pin suspended from the tibial alignment guide used to orient the cutting block's rotation to match the talar axis.

 

 

 

TECH FIG 14 • Setting the tibial cutting block. A. The tibial cut is set for 8 to 9 mm. B. Note that the resection level is set for 8 mm (moved from zero position that was positioned at the apex of the tibial plafond). C-E. Fluoroscopic confirmation of optimal tibial cutting block position. C,D. In the AP plane, the external tibial alignment guide should be parallel to the tibial shaft axis and the cutting block should be oriented with the joint without violating the malleoli. E. In the lateral plane, the resection will ideally be nearly perpendicular to the tibial shaft axis and resecting approximately 8 to 9 mm of bone from the apex of the tibial plafond. (continued)

 

 

92

 

 

 

TECH FIG 14 • (continued) F. A pin is manually placed in the proximal medial aspect of the cutting guide to ensure that the cutting block is not placed too medially, risking weakening medial malleolar support. G. Pins serve to protect malleoli. H. The additional holes are drilled to weaken the bone planned for resection, thereby facilitating the bone's removal. I. Careful tibial preparation with the oscillating saw, avoiding overpenetration of the posterior cortex that may risk flexor hallucis longus (FHL) or posteromedial neurovascular bundle injury. J. With cutting block removed, the medial and lateral drill holes are connected with small reciprocating saw. K. Rarely can the resected distal tibial bone be removed as one piece. L. Using lamina spreader (without teeth so the prepared tibial surface is protected), residual posterior bone may be carefully morselized with the small reciprocating saw. M. Fragments removed using a 90-degree curette and rongeur.

Initial Talar Preparation

 

Through a dedicated drill guide suspended from the external tibial alignment guide, a reference hole is drilled in the anterior talus with (TECH FIG 15A,B) the following:

 

 

Ankle held in neutral sagittal plane position Hindfoot held in physiologic valgus

 

Drill guide removed (TECH FIG 15C)

 

Pin placed in reference drill hole (TECH FIG 15D)

 

 

External tibial alignment guide removed (TECH FIG 15E) Posterior talar chamfer cutting guide placed (TECH FIG 15F)

 

Four drill holes through posterior chamfer guide and four pins placed through the guide, serving as reference for the posterior chamfer cut (TECH FIG 15G,H)

 

In narrow ankles, sometimes, only three pins gain purchase in the talar dome.

 

With malleoli protected, posterior chamfer cut made directly on the four pins and resected bone removed (TECH FIG 15I-L)

Anterior Talar Chamfer Preparation

 

Residual anterior osteophytes removed, so there is no impingement on the guide (TECH FIG 16A).

 

Anterior chamfer milling guide properly positioned and secured with dedicated lamina spreader(s) (TECH FIG 16B-D)

 

Guide should align with second metatarsal when foot is positioned for simulated weight bearing.

 

The anterior chamfer will dictate talar component rotation.

 

 

Proper position confirmed with dedicated AP reference guide (TECH FIG 16E,F) Anterior chamfer milled (TECH FIG 16G)

 

Anterior chamfer preparation completed with a rongeur (TECH FIG 16H,I)

 

 

93

 

 

 

TECH FIG 15 • A. Through a dedicated drill guide suspended from the external tibial alignment guide, a reference hole is drilled in the anterior talus. B. Ankle held in neutral position and hindfoot supported in slight valgus. C. Drill guide removed. D. Pin placed in reference drill hole. E. External tibial alignment guide removed.

F. Posterior talar chamfer cutting guide placed on reference pin, with paddles flush on posterior talar dome. Note use of dedicated lamina spreaders to keep paddles flush. G. Four drill holes through posterior chamfer guide and four pins placed through the guide. H. Posterior chamfer guide removed. I. Four pins serve as reference for posterior chamfer cut. J. Posterior chamfer cut with oscillating saw. Note ribbon retractors to protect malleoli. K. Resected bone removed. L. Posterior chamfer cut complete.

 

 

94

 

 

 

TECH FIG 16 • A. Residual anterior osteophytes removed. B. Anterior talar chamfer guide properly positioned, aligned with second metatarsal. C. Guide secured with anterior pins and lamina spreader(s). D. Guide in proper position. E. AP reference guide placed. F. With ankle dorsiflexion, AP reference guide confirms satisfactory anterior chamfer guide position. G. Anterior chamfer milled. H. Anterior chamfer completed with rongeur. I. Completed anterior chamfer.

Lateral Chamfer and Stem Relief Preparation

 

 

Lateral chamfer guide properly positioned on prepared anterior and posterior chamfer cuts Guide pinned in place (TECH FIG 17A)

 

Confirm proper position clinically.

 

 

Stem preparation should be situated directly over crest, where two chamfers meet (TECH FIG 17B). Avoid posterior lift-off of the lateral chamfer guide.

 

 

Stem relief drilled with dedicated bell saw that leaves central core of bone for larger sizes (TECH FIG 17C,D) For smallest size, the central core is forfeited.

 

Stabilizing plug placed through lateral chamfer cutting guide into prepared stem relief area to further stabilize guide for lateral chamfer preparation (TECH FIG 17E)

 

Lateral chamfer preparation (TECH FIG 17F)

 

 

Protect anterior neurovascular bundle and EHL tendon. Avoid violating anterior tibial cortex with edge of saw.

 

 

Central stabilizing plug removed and lateral chamfer cutting guide removed (TECH FIG 17G) Resected lateral chamfer bone removed (TECH FIG 17H)

 

Gutters inspected to ensure no impinging bone present (TECH FIG 17I) Trial Components

 

Talar trial placed and fully seated (TECH FIG 18A,B)

 

Tibial trial with attached polyethylene trial placed with careful axial distraction placed on the joint (TECH FIG 18C,D)

 

95

 

 

 

TECH FIG 17 • A. Lateral chamfer guide properly positioned on prepared chamfer cuts. B. Stem preparation where two chamfers meet. C. Stem relief drilled with dedicated bell saw. D. Bell saw leaves central core of bone for larger sizes (removed with preparation for smallest talar size). E. Stabilizing plug in stem relief area.

F. Lateral chamfer preparation. G. Central stabilizing plug removed and lateral chamfer cutting guide removed. H. Resected lateral chamfer bone removed. I. Gutters inspected to ensure no impinging bone present.

 

 

 

TECH FIG 18 • A. Talar trial placed. B. Talar trial impacted. C. Tibial trial with attached polyethylene trial placed with careful axial ankle distraction. (continued)

 

 

96

 

 

 

TECH FIG 18 • (continued) D. Tibial trial fully seated. E,F. Fluoroscopic assessment of trial components. E. AP view suggesting satisfactory alignment. F. Lateral view. Note that posterior tibial coverage could be improved. G-J. Upsizing tibial component. G. Judiciously, the tibial preparation is widened to accommodate a size 2 tibial component. H. Size 2 tibial component with size 1 polyethylene (to match unchanged talar component) placed. I. AP view suggests widening tibial preparation and upsizing tibial trial without compromising malleoli. J. Posterior tibial coverage improved; no posterior tibial lift-off and tibial trial pinned.

 

 

Clinical assessment

 

Satisfactory ROM, especially dorsiflexion

 

Satisfactory stability in the coronal plane; assess with the ankle in neutral position

 

Fluoroscopic assessment

 

Confirm proper alignment (TECH FIG 18E).

 

 

Confirm proper bony apposition of tibial component, particularly posteriorly; no posterior “lift-off.” Assess posterior tibial component coverage (TECH FIG 18F).

 

Tibial component may be upsized (TECH FIG 18G-J).

 

If posterior coverage based on intraoperative fluoroscopy is not ideal, then the tibial component may be upsized one size from that of the talar component.

 

 

The polyethylene size will remain the same so it continues to match the talus. Once optimal combination of trial components determined, open true components

 

In this case, a size 2 tibial component is used with a size 1 talar component and a 10-mm polyethylene was

used to optimize coronal plane stability (TECH FIG 18K).

Final Tibial Preparation

 

 

Preparing the tibial stem relief area does not require violating the posterior tibial cortex. With proper trial components in place, tibial trial is pinned.

 

 

Fluoroscopic confirmation that there is indeed no posterior tibial component lift-off (see TECH FIG 18J) Second, more proximal, tibial drill hole made to create relief area for tibial component stem

 

 

Proximal tibial reaming performed (TECH FIG 19A) Tibial stem relief area preparation completed

 

Drill holes connected with a small reciprocating saw (TECH FIG 19B)

 

Dedicated chisel used to the proper depth without violating the posterior tibial cortex (TECH FIG 19C)

 

Dedicated tibial rasp used to ensure transition from prepared tibial surface to prepared relief area for the stem is appropriate and limits risk of component lift-off during insertion (TECH FIG 19D).

 

 

97

 

 

 

TECH FIG 19 • A. With tibial trial pinned and second drill hole prepared, tibia reamer used. Note that posterior cortex is not violated with this preparation. B. Drill holes connected with a small reciprocating saw. C. Dedicated chisel used to the proper depth without violating the posterior tibial cortex. D. Dedicated tibial rasp used to ensure transition from prepared tibial surface to prepared relief area for the stem is appropriate.

Final Implants

 

Locking polyethylene to tibial component

 

On the back table, the polyethylene is attached to the true tibial component (TECH FIG 20A,B).

 

A dedicated device may be used to facilitate locking the polyethylene to the tibial component (TECH FIG 20C).

 

Talar component insertion

 

 

Talus carefully positioned to preserve central core of bone for the stem (TECH FIG 21A,B) Impactor used

 

Avoid impinging the impactor handle on the anterior tibia (TECH FIG 21C).

 

 

 

TECH FIG 20 • A. Manually, polyethylene inserted into locking mechanism on tibial component. A size 2 tibial component was used with size 1 polyethylene. B. Polyethylene locked to tibial component. C. A dedicated device may be used to facilitate locking the polyethylene to the tibial component.

 

 

 

Tibial component insertion Assistant applies axial traction.

 

Surgeon “drives” tibia up into prepared tibia in proper rotation with the goal to avoid posterior lift-off (TECH

FIG 21D).

 

Requires and upwardly directed force with the dedicated insertion device (TECH FIG 21E)

 

If any concern that lift-off occurs, then a lateral fluoroscopy image should be obtained before fully inserting tibial component (TECH FIG 21F).

 

Fully seat final tibial component to same depth as tibial trial (TECH FIG 21G)

 

 

98

 

 

 

TECH FIG 21 • A. Talus carefully positioned to preserve central core of bone for the stem. B. Talar component properly positioned. C. Talar component impacted with dedicated impactor. D. Tibial component is driven up into prepared tibia in proper rotation, with the goal to avoid posterior lift-off. E. Requires and upwardly directed force with the dedicated insertion device. F. If any concern that lift-off occurs, a lateral fluoroscopy image should be obtained before fully inserting tibial component. G. Final tibial component is fully seated to same depth as tibial trial. H,I. Fluoroscopic confirmation of proper component position and alignment. H. AP view. I. Lateral view confirming no posterior lift-off of final components. J. Morselized bone graft form distal tibial resection. K. Anterior defect filled.

 

 

99

 

 

 

TECH FIG 22 • Capsular closure. A. Capsule reapproximated over components. B. Deep neurovascular bundle protected during capsular closure.

 

 

Fluoroscopic confirmation

 

 

Proper component position (TECH FIG 21H) No posterior tibial lift-off (TECH FIG 21I)

 

 

No stress fracture Clinical evaluation

 

 

Satisfactory ROM Satisfactory balance/stability

 

Irrigation

 

 

Bone graft anterior tibial defect (TECH FIG 21J,K) Use morselized bone from tibial resection.

Closure and Postoperative Care

 

 

Capsule (TECH FIG 22A,B): Protect deep neurovascular bundle. Extensor retinaculum: Protect superficial peroneal nerve.

 

 

Routine subcutaneous layer and skin closure Over a drain

 

Avoid pinching skin edges with forceps.

 

 

Recommend well-padded cast with ankle in neutral position Protected weight bearing for approximately 6 weeks

 

Regular follow-up recommended at 6 weeks, 3 months, 6 months, 1 year, and every year thereafter (TECH FIG 23)

 

 

 

TECH FIG 23 • One-year followup. A. AP view. B. Lateral view. C. Dorsiflexion view. D. Plantarflexion view. E.

Hindfoot alignment view suggesting improved hindfoot position from preoperative alignment.

 

 

 

 

 

00

PEARLS AND PITFALLS
	Impossible to insert even ▪ Tibial side will need to be reresected. the thinnest bearing     Dorsiflexion unobtainable ▪ Check the size and the positioning of the talar component. Check that the posterior capsular structures and the medial and lateral talar margins have been adequately cleared. Perform percutaneous lengthening of the Achilles tendon. Reresect the tibia.     Lateral residual laxity ▪ Medial collateral ligament release, and use a thicker polyethylene component. Consider lateral ligament reconstruction.

• Active infection

• Poor anterior skin (multiple scars, previous graft)

• Risk factors for skin necrosis

• Major bone loss

• Diffuse (as opposed to focal) osteonecrosis of the talus

• Nonreconstructable ankle ligamentous instability

 

Absolute contraindications for TAA

 

Relative contraindications for TAA

• Eradicated tibiotalar infection

• Previous medial or lateral surgical approaches to the ankle (TAA incision will be anterior and central)

• Multiple prior surgeries to the ankle

• High body mass index

• High-demand patient (eg, construction work)

• Unrealistic patient expectations

 

POSTOPERATIVE CARE

 

The drain is removed the day after the operation.

 

Once the swelling has subsided, a below-knee circular resin cast is applied.

 

As a rule, weight bearing may be resumed once the resin cast has been applied.

 

 

Patients who have undergone Achilles tendon lengthening will be non-weight bearing for 3 weeks. Where there has been a malleolar fracture, the period of non-weight bearing will be 45 days.

The cast is removed after 45 days to prevent skin problems, and physiotherapy is commenced.

OUTCOMES

Bonnin et al reported the results of a consecutive series of their first 98 cases implanted between 1997 and 2000.

With a mean 35 months of follow-up (range 24 to 57 months), they reported two failures requiring conversion to ankle arthrodesis.

Reviewing the same consecutive series with a mean 6.4 years of follow-up (range 5 to 8.5), they reported five failures necessitating conversion into arthrodesis.

The mean American Orthopaedic Foot and Ankle Society (AOFAS) ankle-hindfoot score preoperatively was

32.3 (standard deviation [SD] 10) and 83.1 (SD 16) at last follow-up. The mean ankle ROM measured on dynamic radiographs improved from 15.2 degrees preoperatively (SD 10) to 28.3 degrees at follow-up (SD 7).

 

 

COMPLICATIONS

Technical difficulties in TAA may arise from a number of factors.

Failure to Reestablish the Physiologic Joint Line

The final level of the implant joint line will depend on the level of the tibial cut.

The level is determined with reference to the preoperative radiographs. Depending on the status of the tibial plafond, the anatomy of the malleoli, and lateral talomalleolar congruency, four different patterns may be encountered (FIG 4):

 

 

The ankle mortise is intact, with symmetric wear of the tibial plafond. The procedure should be a simple resurfacing, with the metal tibial component and polyethylene thickness replacing exactly what is resected.

 

The ankle mortise is intact, but the tibial plafond is asymmetrically worn. This pattern is seen in advanced RA, especially in the wake of long-term steroid therapy. In this case, a reasonable and balanced distal tibial resection level will need to be determined during preoperative planning.

 

The malleoli are deformed, but the tibial plafond is intact. In our experience, this deformity involves the lateral malleolus. This pattern is seen in RA with severe hindfoot valgus that has resulted in a fatigue fracture of the fibula. In this case, the lateral malleolus will need to be managed with malleolar osteotomy and plating before TAA.

 

The malleoli are deformed and the tibial plafond is worn or depressed. These cases will need to be managed with a combination of the principles discussed earlier: First, a normal ankle mortise pattern will have to be created, and then, a resection level will need to be determined, taking into account the extent of loss of tibial bone stock.

Extra-articular Deformity

 

The physiologic ankle joint line is perpendicular to the axis of the tibia and the hindfoot axis is in slight (5 to 10 degrees) valgus in relation to the tibial axis. To promote long-term

 

 

01 02

implant survival, physiologic alignment will need to be restored.

 

 

 

FIG 4 • A,B. Ankle mortise intact, no asymmetric wear of the tibial pilon. C,D. Ankle mortise intact, tibial pilon asymmetrically worn. E,F. Malleoli deformed, tibial pilon intact. G,H. Malleoli deformed, tibial pilon worn.

 

 

Inserting a TAA prosthesis into a malaligned tibia or hindfoot is a recipe for early loosening and failure.

 

Correction of deformities may be difficult in sequelae of trauma or RA. Preoperative evaluation should allow the determination of whether these deformities have an intraarticular or extra-articular origin.

 

In our experience, most intra-articular deformities resulting from wear or laxity (including varus position caused by OA in chronic instability) can be corrected from within the joint with the prosthesis.

 

In contrast, most extra-articular deformities cannot be corrected from within the joint with the prosthesis and must be treated independently with supramalleolar osteotomy, performed either staged or simultaneous to TAA (FIG 5A).

 

In our opinion, hindfoot malalignment associated with arthritis must be corrected by doing a triple arthrodesis before TAA (FIG 5B).

 

We recommend performing staged triple arthrodesis and TAA to reduce the potential for skin problems and edema. In our hands, triple arthrodesis is usually done as a firststage procedure 45 days before TAA, which avoids prolonged cast immobilization.

 

We perform the triple arthrodesis by what would be an extension of the anterior approach to the ankle to prepare the talonavicular joint and a limited lateral-subfibular approach to the subtalar joint. We avoid dissection under the talar head to minimize the risk of necrosis of the talar body.

 

 

Fixation is achieved using a talocalcaneal screw and two talonavicular and calcaneocuboid staples. The TAA prosthesis must be positioned on a properly aligned hindfoot.

 

In RA patients with a valgus deformity and severe lateral bone loss, bone grafting is the rule. Graft material is harvested from a local donor site (bone slices taken from the midtarsal joint, sometimes bone material taken from the proximal tibial metaphysis) and, in some cases, from the ipsilateral iliac crest in case of severe deformity.

 

 

 

FIG 5 • A. In case of tibial malunion, a correction via a supramalleolar osteotomy must be associated with the ankle prosthesis. B. In case of hindfoot deformity, a correction via a subtalar or triple arthrodesis or calcaneal osteotomy must be done in association with the ankle prosthesis.

 

 

We stage the TAA 45 days after triple arthrodesis using the proximal extension of the same anterior approach. The talocalcaneal screw is removed.

Bone Loss

 

Implant fixation requires sufficient tibial and talar bone stock and an intact ankle mortise.

 

In RA patients or in posttraumatic OA, there may be major bone loss, and defects may have to be grafted. In particularly severe cases, TAA may be contraindicated.

Ankle Instability

 

OA secondary to chronic lateral laxity is technically challenging because the persistence of lateral laxity may cause rapid deterioration of the prosthesis.

 

In our experience, most cases can be balanced with TAA. We routinely restore the ankle's soft tissue balance with TAA and comprehensive soft tissue release on the concave side of the deformity.

 

Medial release in a varus deformity is challenging and involves the entire deltoid ligament, which is first released subperiosteally from its malleolar attachment and then detached from the talus. We have been satisfied with this balancing technique, which, in our hands, eliminates the need for the medial malleolar osteotomy technique to rebalance the deltoid ligament.

 

With comprehensive and satisfactory medial release, we rarely need to perform a ligament reconstruction

on the convex side of the deformity. Occasionally, however, for severe varus malalignment, we need to perform a lateralizing and valgus-producing calcaneal osteotomy to further realign the hindfoot.

Ankle Stiffness

 

End-stage tibiotalar joint arthritis almost always leads to stiffness of the tibiotalar joint.

 

Stiffness with equinus deformity requires sequential steps to regain dorsiflexion, beginning with excision of anterior

 

03

ossifications, then freeing of talomalleolar adhesions, and finally posterior capsulectomy from within the joint.

 

The use of a lamina spreader greatly facilitates capsulectomy. However, great caution should be used to avoid avulsion of the medial malleolus and accidental penetration of the prepared tibial surface.

 

In particular, the surgeon must make sure that complete capsulectomy is performed at the posteromedial corner, flush with the tibialis posterior tendon.

 

Freeing up adhesions to this tendon is important, as they may cause postoperative pain, particularly in patients who have previously undergone a procedure through a posteromedial approach.

 

In this case, tenolysis of the tibialis posterior tendon with opening of its retinaculum through a limited posteromedial approach may be useful. This approach makes posterior capsular release and even repair of associated fissures much easier.

 

Lastly, contracture of the triceps surae and Achilles tendon is often responsible for a deficit of dorsiflexion. Therefore, lengthening should be considered whenever dorsiflexion is less than 10 degrees after insertion of the trials. Release of flexors may be achieved through either tendon lengthening or fasciotomy of the triceps surae.

 

Achilles tendon lengthening

 

This simple procedure has little influence on the postoperative course, but it is associated with long-term persistence of posterior discomfort and sometimes with permanent loss of plantarflexion strength and ROM.

 

Lengthening technique consists of making two or three percutaneous staged incisions with a fine scalpel; each incision should involve slightly more than half of the tendon.

 

The most distal incision may be performed on either side, depending on the fibers to be lengthened— laterally for a valgus deformity in order to preserve varus-oriented fibers and medially for a varus hindfoot.

 

While making incisions, the ankle should be held in forced dorsiflexion with the trial components in place. Dorsiflexion suddenly increases as fibers slide over one another (FIG 6).

 

Fasciotomy of the triceps surae usually does not cause postoperative pain; it is performed through a limited midline posterior approach at the middle third of the leg. The sural vein is preserved.

 

The insertional fascia of the gastrocnemius is sectioned in a V-shaped fashion and the underlying soleus fascia is sectioned in line with the muscle fibers. The postoperative course is the same as for Achilles tendon lengthening.

Anterior Translation of Talus

 

Anterior translation of the talus must always be corrected to restore normal kinematics and avoid early wear due to overloading in a fixed-bearing prosthesis or due to overhanging of the polyethylene bearing in a mobile-bearing prosthesis (alignment between the polyethylene bearing and the talar component must be maintained at all times).

 

Repositioning of the talar component requires complete soft tissue release (ie, talomalleolar compartment, posterior capsule) as well as correction of equinus deformity (if any) through Achilles tendon lengthening.

 

Should these procedures prove ineffective, the talar component will have to be moved posteriorly, which

means recutting the anterior chamfer.

 

 

 

FIG 6 • Percutaneous lengthening of the Achilles tendon. Lengthening technique consists of making two or three percutaneous staged incisions with a fine scalpel; each incision should involve slightly more than half of the tendon.

 

 

In our experience, the tibial component will have to be positioned as far anteriorly as possible beneath the distal tibia.

 

SUGGESTED READINGS

1. Bonnin M. La prothèse totale de cheville. Techn Chir Orthopéd Traumatol 2002;10:44-903.

    

    

2. Bonnin M, Bouysset M, Tebib J, et al. Total ankle replacement in rheumatoid arthritis: treatment strategy. In: Bouysset M, Tourné Y, Tillmann K, eds. Foot and Ankle in Rheumatoid Arthritis. Paris, France: Springer-Verlag, 2006:207-219.

    

    

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

    

    

4. Bonnin M, Judet T, Colombier JA, et al. Total ankle prosthesis: five- to eight-year results. Presented at the 22nd Annual Summer Meeting of the American Orthopaedic Foot and Ankle Society, July 14-16, 2006, La Jolla, CA.

    

    

5. Bonnin M, Judet T, Siguier T, et al. Total ankle replacement. History, evolution of concepts, design and surgical technique. In: Bouysset M, Tourné Y, Tillmann K, eds. Foot and Ankle in Rheumatoid Arthritis. Paris, France: Springer-Verlag, 2006:179-200.

    

    

6. Jakubowski S, Mohing W, Richter R. Operationen am rheumatischen Fuss. Therapiewoche 1970;20:762-768.

    

    

7. Judet T, Piriou P, Elis JB, et al. Total-endoprothese des oberen Sprunggelenkes. Konzepte und Indikationen der Saltoprothese. In: Imhoff AB, Zollinger-Jies H, eds. Fuβchirurgie. Stuttgart, New York: Georg Thieme Verlag, 2003.

    

    

8. Schweitzer KM, Adams, SB, Viens NA, et al. Early prospective clinical results of a modern fixed-bearing total ankle arthroplasty. J Bone Joint Surg Am 2013;95:1002-1011.

    

    

9. Vainio K. The rheumatoid foot; a clinical study with pathological and roentgenological comments. Ann Chir Gynaecol Fenn Suppl 1956;45(1):1-107.

    

    

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