DEFINITION

End-stage ankle arthritis failing to respond to nonoperative treatment

 

 

ANATOMY

 

Ankle

 

 

Tibial plafond with medial malleolus

 

 

 

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

 

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

 

Fibula

 

 

Articulation with lateral talus

 

 

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

 

 

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

 

Distal tibiofibular syndesmosis

 

 

 

 

Anteroinferior tibiofibular ligament Interosseous membrane Posterior tibiofibular ligament

 

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

 

PATHOGENESIS

 

Posttraumatic arthrosis

 

 

 

Most common etiology Intra-articular fracture

 

 

Ankle fracture-dislocation with malunion Chronic ankle instability

 

Primary osteoarthrosis

 

 

 

Relatively rare compared to hip and knee arthrosis Inflammatory arthropathy

 

 

Most commonly rheumatoid arthritis Other

 

Hemochromatosis

 

 

 

Pigmented villonodular synovitis Charcot neuroarthropathy Septic arthritis

NATURAL HISTORY

 

Posttraumatic arthrosis

 

 

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

 

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

 

 

 

 

Relative anterior subluxation of the talus Varus tilt of the talus within the ankle mortise Hindfoot varus position

 

 

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

 

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

 

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

 

PATIENT HISTORY AND PHYSICAL FINDINGS

 

Patient history

 

 

Often a history of ankle trauma

 

 

 

Ankle fracture, particularly intra-articular Ankle fracture with malunion

 

Chronic ankle instability (recurrent ankle sprains)

 

 

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

 

Ankle swelling

 

 

Progressively worsening activity level Physical findings

 

Limp

 

 

 

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

 

Potential associated foot deformity

 

 

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

 

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

 

IMAGING AND OTHER DIAGNOSTIC STUDIES

 

Weight-bearing anteroposterior (AP), lateral, and mortise views of the ankle (FIG 1)

 

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

 

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

 

 

56

 

 

 

FIG 1 • Weight-bearing ankle radiographs of a 60-year-old woman with end-stage posttraumatic left ankle arthritis. A. AP view (note slight varus talar tilt). B. Lateral view.

 

 

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

 

We typically evaluate complex or ill-defined ankle-hindfoot patterns of arthritis with or without deformity using computed tomography (CT) of the ankle and hindfoot.

 

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

 

 

DIFFERENTIAL DIAGNOSIS

See the section on Pathogenesis.

 

 

NONOPERATIVE MANAGEMENT

 

 

Activity modification Bracing

 

Ankle-foot orthosis (AFO)

 

Double upright brace attached to shoe

 

 

 

 

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

 

Viscosupplementation

 

SURGICAL MANAGEMENT

Preoperative Planning

 

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

 

 

Noninvasive vascular studies and potential vascular surgery consultation should be obtained if necessary.

 

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

 

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

 

 

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

 

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

 

Ankle ROM should be determined.

 

 

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

 

 

 

Anterior tibiotalar exostectomy Posterior capsular release

 

Occasionally, tendo Achilles lengthening

 

 

Instrumentation

 

 

These instruments facilitate TAA:

 

 

Small oscillating saw to fine-tune cuts, resect prominences with precision, and easily morselize large bone fragments to be evacuated from the joint

 

A rasp for final preparation of cut bony surfaces

 

An angled curette, particularly to separate bone from the posterior capsule

 

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

 

Positioning

 

 

The patient is positioned supine with the plantar aspect of the operated foot at the end of the operating table. The foot and ankle are well balanced, with toes directed to the ceiling.

 

 

A bolster placed under the ipsilateral hip prevents undesired external rotation of the hip. We routinely use a thigh tourniquet and regional anesthesia.

 

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

 

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

 

Approach

 

An anterior approach to the ankle is made, using the interval between the tibialis anterior (TA) tendon and the extensor hallucis longus (EHL) tendon.

 

 

57

TECHNIQUES

• Exposure

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

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

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

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

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

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

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

 

 

 

 

TECH FIG 1 • Anterior approach to the ankle. A. Approach. B. Close-up of superficial peroneal nerve. C. Division of extensor retinaculum directly over EHL tendon. D. Deep neurovascular bundle is identified and protected. E. After anterior capsulotomy, with ankle exposed.

 

 

Preserving the retinaculum over the TA tendon:

 

 

This 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.

 

Preserving the retinaculum over the TA tendon is not always possible; some patients do not have a dedicated sheath for the TA.

 

The interval between the TA and EHL tendon is used, with the TA and EHL tendons retracted medially and laterally, respectively.

 

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

 

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

 

Elevate this separated capsule and periosteum medially and laterally to expose the ankle, to access the medial and lateral gutters, and to visualize the medial and lateral malleoli.

 

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

 

58

• Tibial Preparation

Positioning the External Tibial Alignment Guide

 

An osteotome placed in the medial gutter serves as a reference for optimal rotation for the tibial preparation (TECH FIG 2).

 

Place a pin in the proximal tibia via a 1-cm incision over the tibial tubercle.

 

When viewed in the AP plane, this pin is oriented parallel to the reference osteotome in the medial gutter.

 

When viewed in the lateral plane, the pin should be perpendicular to the tibial shaft axis if the physiologic 3 to 5 degrees of posterior slope to the tibial component is desired. We prefer to implant the tibial component perpendicular to the longitudinal tibial shaft axis (no posterior slope), aiming the pin slightly proximally. The external tibial alignment guide directs the initial tibial cut into 3 degrees of posterior slope; we aim to eliminate this slope.

 

 

 

TECH FIG 2 • Positioning the external tibial alignment guide. A,B. Positioning the proximal pin relative to a reference osteotome placed in the medial gutter. C,D. Setting rotation of the distal cutting block of the guide relative to the medial gutter reference osteotome. E,F. Fluoroscopic confirmation of proper guide position in the AP and lateral planes.

 

 

Suspend the external tibial alignment guide from the proximal pin. To further promote a perpendicular tibial preparation relative to the tibial shaft axis, we raise the proximal aspect of the external tibial alignment guide two to three fingerbreadths above the tibial spine before securing it to the proximal pin.

 

Set the rotation of the cutting block for tibial preparation based on the reference osteotome set in the medial gutter. A dedicated T guide temporarily attached to the distal aspect of the guide facilitates setting proper rotation. Lock the rotation of the distal block with the knob connecting the telescoping rods of the guide.

 

While controlling rotation, set the proper length of the guide via the telescoping rods.

 

Fine-tuning of the distal block's lateral plane position is possible. We routinely separate the distal block of the guide from the portion of the guide used to pin it to the tibia by at least 10 mm.

 

59

 

 

 

TECH FIG 3 • Determining tibial plafond resection level. A. Angel wing about to be inserted into capture guide attached to distal tibial cutting block. B. Angel wing in capture guide with height adjustment being made under fluoroscopy. C. Fluoroscopic image of angel wing confirming tibial resection level.

 

 

If the initial position of the distal block is set at the apex of the plafond, the desired 5 mm of resection may be easily set and even greater resection is possible in a tighter ankle.

 

We make sure that the block is positioned at the tibial plafond's apex, that it is properly rotated, and that we are able to fine-tune the block's proximal-distal position before pinning the guide to the tibia.

 

Multiple options exist to pin the guide to the tibia. We recommend using pins at different levels rather than pins in a single plane (risks creating a stress riser).

Determining Tibial Plafond Resection Level

 

Attach the cutting capture guide to the distal block and insert an angel wing resection guide in the capture guide. Use fluoroscopy in the lateral plane to determine the proper resection level for the tibial cut (TECH FIG 3).

 

Adjust the cutting guide in the coronal plane to ensure that the malleoli are protected with tibial resection.

 

There is only a single capture guide size.

 

We routinely set the guide based on a pin placed loosely in the medial aspect of the capture guide.

 

 

 

TECH FIG 4 • A. After determining proper coronal placement of the tibial cutting block, the capture guide is pinned, with the pins used to protect the malleoli. B. Saw in the capture guide. C. Medial resection with a reciprocating saw to complete the initial tibial preparation. (continued)

 

 

We aim to position the guide so that the medial extent of tibial preparation is directly proximal from the transition of tibial plafond to medial malleolus.

 

Drive the pin used as a reference into the tibia through the medial aspect of the capture guide to protect the medial malleolus.

 

Similarly, place a lateral pin in the lateral aspect of the capture guide and advance it into the lateral gutter.

 

The capture guide has several options to place the lateral pin to accommodate any coronal plane dimension of the tibial plafond.

Initial Tibial Resection

 

With the soft tissues protected, particularly the deep neurovascular bundle, make the distal tibial cut with an oscillating saw through the horizontal portion of the capture guide. To complete the cut, use a reciprocating saw along the medial border of the capture guide, extending proximally from the medial gutter (TECH FIG 4).

 

Remove the capture guide and evacuate the resected bone.

 

A toothless lamina spreader may be placed judiciously on the prepared tibial surface and dorsal talus to facilitate evacuation of bone from the posterior ankle.

 

60

 

 

 

TECH FIG 4 • (continued) D. Tibial resection after removal of the capture guide (note that the cutting block was translated slightly medial for optimal positioning). E. Removal of the resected tibial bone (note

the judicious use of a toothless lamina spreader to facilitate access to the posterior ankle). F. Confirming adequate tibial resection with plastic spacer (9 mm).

 

 

We routinely use a small reciprocating saw to morselize the posterior fragments and a combination of curved curette and rongeur to retrieve the fragments that need to be separated from the posterior capsule.

 

The curette is used directly vertically in the ankle and never levered against a malleolus.

 

We routinely perform a posterior capsular resection to optimize dorsiflexion.

 

To ensure that the tibial resection is adequate, use the system's plastic spacer as a sizing guide. The 9-mm end of this sizing guide equals the combined height of the tibial component (3 mm) and the thinnest polyethylene component (6 mm).

• Talar Preparation

  Initial Talar Preparation

   

  Residual articular cartilage must be removed from the dorsal talar dome so that the talar cutting guide may be properly balanced on the dorsal talus. We routinely use a thin oscillating saw to remove residual cartilage.

   

  Position the talar guide within the ankle joint and secure it to the distal block of the external alignment guide.

   

  We then hold the ankle in neutral dorsiflexion-plantarflexion.

   

  Excessive dorsiflexion risks talar preparation, leading to anterior translation and tilt of the talar implant. Moreover, an exaggerated notch will be created in the dorsal talar neck.

   

  Excessive plantarflexion risks talar preparation, leading to posterior translation and tilt of the talar implant. In addition, too much posterior talus will be removed.

   

  Excessive plantarflexion may be a result of fixed equinus. If the talus cannot be brought to a neutral position (confirm with an intraoperative radiograph), then consider a tendo Achilles lengthening rather than risk resecting too much of the posterior talus.

   

  With perfect contact of both the medial and lateral talar dome on the intra-articularly placed paddle of the talar cutting guide and a neutral sagittal plane alignment maintained, pin the talar guide.

   

  Place the angel wing resection guide in the talar cutting guide and use lateral plane fluoroscopy to confirm proper resection level and desired orientation for the guide.

   

  Place two more pins in the talar guide to protect the malleoli and further stabilize the guide.

   

  Make the initial talar cut using an oscillating saw, remove the guide, and evacuate the resected bone from the joint (TECH FIG 5A-E).

   

  To ensure that a balanced resection was performed on the tibia and talus and that the resection levels are appropriate, use the plastic spacer-sizing guide impactor and confirm proper alignment and resection levels on intraoperative fluoroscopy (TECH FIG 5F,G).

  Sizing the Talus and Positioning the 4-in-1 Talar Reference Guide (“Datum”)

   

  Position a sizing guide on the dorsal prepared talar surface and properly rotate it with the second metatarsal. The proper sizing guide matches the dimensions of the true talar implant and therefore should be placed in the desired position for the talar component (TECH FIG 6A).

   

  With the sizing guide in the appropriate position, drive the central pin through the guide into the talus (TECH FIG 6B).

   

  Confirm proper sagittal plane guide position on the lateral fluoroscopic view: The nob on the guide should

  center over the lateral process of the talus (TECH FIG 6C).

   

  With the sizing guide removed, position the 4-in-1 talar reference guide (datum) over the central pin and flush onto the prepared talar surface (TECH FIG 6D).

   

  Be sure the guide is rotated in line with the second metatarsal. Coronal plane position of the datum is dictated by the central pin position; often, the datum position may appear slightly lateral.

   

  Secure the 4-in-1 guide to the talus with dedicated pins (TECH FIG 6E,F).

   

   

  61

   

   

   

  TECH FIG 5 • Talar resection. A. Talar resection guide to be suspended from the external tibial alignment guide. B. The surgeon should ensure proper talar alignment (patient had an equinus contracture, and gastrocnemius-soleus recession was required to obtain optimal talar position). C. Intraoperative fluoroscopic view confirming resection level. Note the gap between intra-articular paddle of talar resection guide, suggesting some residual articular cartilage on talar dome and leaving talar resection too shallow. This prompted removal of residual talar cartilage to obtain optimal talar resection. D. Pinning the talar cutting guide. E. Talar resection with soft tissues protected. F. Plastic spacer confirms adequate resection (12-mm gap). G. Fluoroscopy confirms that the resections are balanced.

   

   

   

  TECH FIG 6 • Talar sizing (different patient). A. Talar sizing guide being used to determine ideal talar size.

  B. Talar sizing guide properly positioned on the prepared talar surface with proper rotation, aligned with the second metatarsal axis, and with the central pin positioned. C. Fluoroscopic confirmation of proper sagittal plane position. Note that the nob on the guide is directly over the lateral process of the talus. (continued)

   

   

  62

   

   

   

  TECH FIG 6 • (continued) D. The 4-in-1 reference guide is positioned on the prepared talar surface over the central pin. Guide positioned on the prepared talar surface with the handle that may be used to avoid posterior lift-off. E. Threaded pin fixation of the 4-in-1 guide to the talus. F. The 4-in-1 guide properly positioned and secured, with handle removed.

   

   

  Confirm proper position of the 4-in-1 guide with lateral fluoroscopy. Ideally, the center point of the undersurface of the guide rests directly over the lateral talar process. Another rough estimate of proper position is that the guide is centered under the tibia.

   

  Full dorsiflexion of the talus is not possible due to impingement of the pins securing the guide to the talus.

   

  If this position cannot be confirmed, then the 4-in-1 talar guide must be repositioned and repinned.

   

  This may be difficult because, typically, only a subtle move of the guide is necessary and securing a pin immediately adjacent to a previous pin position is possible but challenging.

• Completing the Talar Preparation and Implanting the Talar Component

Anteroposterior Talar Chamfer Cutting Guide

 

Secure the anteroposterior talar chamfer cutting guide to the 4-in-1 talar reference guide and place an additional pin in the guide to stabilize it to the talus (TECH FIG 7A).

 

Cut the posterior talar chamfer using an oscillating saw in the posterior capture guide.

 

 

 

TECH FIG 7 • Anterior and posterior talar chamfer preparation. A. Posterior chamfer bone resection; note the AP chamfer guide has a posterior capture guide. B. Anterior chamfer milling. C. Talus with 4-in-1 reference guide in place and with prepared anterior and posterior chamfers.

 

 

 

Mill the anterior chamfer with the soft tissues and deep neurovascular bundle protected (TECH FIG 7B). Remove the AP chamfer guide, leaving the 4-in-1 guide in place (TECH FIG 7C).

Mediolateral Chamfer Cutting Guide

 

Secure the mediolateral chamfer cutting guide to the 4-in-1 talar reference guide (TECH FIG 8).

 

Two additional smooth pins may be placed through this guide to further stabilize the guide to the talus.

 

 

63

 

 

 

TECH FIG 8 • Mediolateral talar chamfer preparation. A. The mediolateral chamfer guide. B. Guide attached to the 4-in-1 reference guide and lateral chamfer being prepared with reciprocating saw (note protection of soft tissues with retractor). C. Talus after mediolateral chamfer resection and rongeur used to evacuate resected bone from medial gutter.

 

 

With the soft tissues and neurovascular structures protected, make the medial and lateral chamfer cuts with a reciprocal saw.

 

To accommodate the talar implant:

 

 

Medial cut is made to a depth of 10 mm. Lateral cut is made to a depth of 15 mm.

 

 

Remove the mediolateral chamfer and 4-in-1 reference guides. Evacuate the resected bone with the following:

 

 

 

A thin osteotome A curved curette A rongeur

 

Inspect the prepared talus for any uneven surfaces or residual bony prominences, which may be removed judiciously with a small reciprocal saw and a rasp.

The “Window” Talar Trial

 

Position the window talar trial on the prepared talus (TECH FIG 9A-C).

 

 

 

TECH FIG 9 • Trial talus (window trial). A. Lateral view of trial. B. AP view of trial. C. Trial pinned to talus; note congruent fit on all prepared surfaces. (continued)

 

 

Often, any incongruencies or prominences still need to be addressed to ensure that the guide rests completely flush on all prepared surfaces of the talus.

 

Because the guide is a window, proper fit can be confirmed for the true implant that is resurfacing without any means of determining the actual bony contact between bone and implant.

 

Pin the talar trial.

 

 

Use a router to create the slot in the talus to accommodate the talar implant's fin (TECH FIG 9D-F). Use a stem punch to finish preparing the talar fin slot.

Implanting the Talar Component

 

Orient the properly sized talar component with the longer side placed laterally (to articulate with the fibula) (TECH FIG 10).

 

Gently tap the prosthesis posteriorly with the set's plastic spacersizer impactor to rest in the optimal position over the fin slot.

 

64

 

 

 

TECH FIG 9 • (continued) D-F. Preparing the fin slot for the talar stem. D. Using the router in the trial talus (note the judicious use of a toothless lamina spreader to afford greater support to the trial during talar stem preparation). E. Talus after removal of talar trial and fin slot preparation. F. Stem punch is used to complete preparation of fin slot.

 

 

Use the talar dome impaction device to impact the talar component.

 

The anterior tibial cortex must be protected.

 

We make sure that despite proper initial positioning the talar component does not tilt anteriorly, which it will tend to do given the limited access to the natural talus.

 

Fully seat the talar component.

Final Preparation of the Tibial Plafond and Tibial Component Implantation

 

 

Measure the AP dimensions of the tibia. Select the corresponding tibial component.

 

If the mediolateral dimensions of the tibial plafond do not accommodate this component, then judiciously remove one or two more millimeters of medial bone to safely position the tibial trial.

 

Also, all syndesmotic soft tissue impinging in the joint must be removed.

 

The tibial trial should align with the center of the tibial shaft axis (TECH FIG 11A-D).

 

It should not be tilted in varus or valgus.

 

It should not be lateral to the longitudinal center of the tibial shaft.

 

 

 

TECH FIG 10 • Inserting talar component. A. Talar component properly oriented. B. Impacting the talar component (note that the ankle is plantarflexed and the impactor is not contacting the anterior tibia).

 

 

After positioning the proper size of tibial component and confirming its position on intraoperative fluoroscopy, pin the tibial trial.

 

Temporarily insert a trial polyethylene insert to maintain pressure on the tibial trial and therefore optimal bony apposition of the tibial trial base plate and prepared tibial surface.

 

On intraoperative fluoroscopy, there should not be any posterior tibial tray lift-off from the prepared tibial surface and the tibial trial should be well aligned with the tibial shaft axis on the AP view.

 

Prepare the barrel holes with the corresponding drill and chisel and remove the tibial trial and trial polyethylene. Leave the pin placed to secure the tibial trial as a reference.

 

Irrigate the joint.

 

 

Using the dedicated tibial impaction device, impact the tibial component almost fully (TECH FIG 11E-G). Use the plastic spacer-sizer impactor to advance the tibial component to its final position.

 

Again, use a trial polyethylene to afford further stability to the tibial trial as the final impaction is performed (TECH FIG 11H,I).

 

65

 

 

 

TECH FIG 11 • Final tibial preparation and insertion. A. Properly sized tibial trial in place, with trial polyethylene for support (we routinely obtain fluoroscopic confirmation in the lateral plane that the tibial trial is flush on the prepared tibial surface). B. Reaming the barrel holes. C. Using the dedicated chisel to complete the barrel hole preparation. D. Prepared tibia. E. Tibial component being advanced with insertion device. F. With tibial component nearly fully seated, trial polyethylene is inserted to support posterior tibial component. G. Final impaction of tibial component. Trial polyethylene clinical (H) and fluoroscopic (I) views.

 

 

66

Final Polyethylene Implantation

 

With the true tibial and talar components implanted, determine the optimal polyethylene size based on the trial polyethylenes (TECH FIG 12A-D).

 

With the ankle in neutral position, there should be virtually no lift-off at the two polyethylene-prosthesis interfaces when a varus or valgus stress is applied.

 

 

 

TECH FIG 12 • Insertion of final polyethylene. A. Manual insertion. B. Polyethylene in place. C. Dorsiflexion. D. Plantarflexion. Final fluoroscopic AP (E) and lateral (F) views. The talus is proud posterior because of a relatively conservative initial talar cut. In our experience, the component will settle (not subside) into a stable position.

 

 

ROM must allow dorsiflexion to at least 5 to 8 degrees, preferably more.

 

Occasionally, tendo Achilles lengthening is required. In these select situations, we routinely perform a gastrocnemius-soleus recession.

 

Contain the polyethylene meniscus under the tibial component during ROM (TECH FIG 12E,F).

• Closure and Casting

 

Thoroughly irrigate the joint and implant with sterile saline.

 

While protecting the prosthesis, fill the anterior barrel holes with bone graft from the resected bone (TECH FIG 13).

 

 

Remove the pin from the proximal tibia. Reapproximate the capsule.

 

We routinely use a drain.

 

The tourniquet is released and meticulous hemostasis is obtained.

 

 

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

 

Reapproximate the skin to a tensionless closure.

 

Place sterile dressings on the wounds, and apply adequate padding and a short-leg cast with the ankle in

neutral position.

67

 

TECH FIG 13 • Bone grafting and closure. A. Bone grafting the anterior cortex at the barrel holes. B.

Capsular closure.

 

 

 

 

PEARLS AND PITFALLS

 

Tibial preparation

• Although traditionally up to 7 degrees of posterior slope was recommended, we favor 0 degree of posterior slope. In our opinion, the mobile bearing will be more stable with a more uniform load distribution across the ankle.

   

  Talar preparation

• Confirm fluoroscopically that the talus is in neutral dorsiflexion-plantarflexion in the sagittal plane so that the talar component will be in optimal position. If there is residual equinus despite anterior osteophyte removal, perform a tendo Achilles lengthening or gastrocnemius-soleus recession to position the talus correctly.

• Remove residual cartilage from the dome of the talus to ensure an adequate talar resection level. The distance between the cutting slot and paddle that rests on the talar dome is fixed. Therefore, if there is residual talar dome cartilage or a prominence that tilts the cutting guide, the initial talar cut will be less than desired or asymmetric.

   

  Use of the 4-in-1 talar reference guide (datum)

• Confirm its proper AP position with a lateral fluoroscopic view.

   

   

  Impacting the talar component

• Because of the limited access to the ankle, the talar component tends to tilt anteriorly when impacted, even with optimal talar preparation. Be sure it is positioned properly in the sagittal plane over the talus (inserted posteriorly enough) before it is impacted. During impaction, carefully place a small osteotome under the anterior edge of the prosthesis to limit the anterior tilt.

   

  Coronal plane position of the tibial component

• The tibial component must be centered under the tibial shaft axis. If performed judiciously, one or two more millimeters of medial tibial bone may be resected with a small reciprocating saw to translate the tibial component more medially, without compromising the medial malleolus.

   

  Impacting the tibial component

• The tibial component is wider anteriorly than posteriorly. The medial malleolus must be carefully monitored during tibial component impaction. If the component begins to impinge on the medial malleolus, the reciprocating saw may be used to perform an anterior “relief” cut to relieve stress on the malleolus. With proper reaming of the barrels in the trial component, this is rarely an issue, but it may be encountered.

 

POSTOPERATIVE CARE

 

Overnight stay

 

Nasal oxygen while in the hospital

 

 

Touchdown weight bearing on the cast is permitted, but elevation is encouraged as much as possible. The patient returns in 2 to 3 weeks for cast change and suture removal.

 

The patient then returns at 6 weeks postoperatively for removal of cast and weight-bearing radiographs of the ankle.

 

If there is no evidence of a stress fracture or failure of the procedure, then the patient can progress to a regular shoe and full weight bearing (FIG 2).

 

OUTCOMES

Although some recently reported outcomes are based on high-level evidence, results of TAA are almost uniformly derived from level IV evidence. Two recent investigations of the Scandinavian total ankle replacement are level I5 and level II3 but with short- to intermediate-term follow-up only.2,4

68

 

 

 

 

FIG 2 • Weight-bearing radiographs of same patient in FIG 1. A. AP view. B. Lateral view (note that talus has assumed anatomic position under tibial shaft axis).

 

 

Functional outcome using commonly used scoring systems for TAA (American Orthopaedic Foot and Ankle

Society [AOFAS],1 Mazur, and New Jersey Orthopaedic Hospital [NJOH] [Buechel-Pappas]) suggest uniform improvement in all studies, with follow-up scores ranging from 70 to 90 points (maximum 100 points).

 

Patient satisfaction rates for TAA exceed 90%, although follow-up for the patient satisfaction rating often does not exceed 5 years.

 

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

 

COMPLICATIONS

Infection (superficial or deep)

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

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

Subsidence

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

 

 

 

REFERENCES

1. Kofoed H. Scandinavian total ankle replacement (STAR). Clin Orthop Relat Res 2004;(424):73-79.

    

    

2. Nunley JA, Caputo AM, Easley ME, et al. Intermediate to long-term outcomes of the STAR Total Ankle Replacement: the patient perspective. J Bone Joint Surg Am 2012;94(1):43-48.

    

    

3. Saltzman CL, Mann RA, Ahrens JE, et al. Prospective controlled trial of STAR total ankle replacement versus ankle fusion: initial results. Foot Ankle Int 2009;30:579-596.

    

    

4. Wood PL, Prem H, Sutton C. Total ankle replacement: medium-term results in 200 Scandinavian total ankle replacements. J Bone Joint Surg Br 2008;90(5):605-609.

    

    

5. Wood PL, Sutton C, Mishra V, et al. A randomised, controlled trial of two mobile-bearing total ankle replacements. J Bone Joint Surg Br 2009;91(1):69-74.