Pascal F. Rippstein, Mark E. Easley, and J. Chris Coetzee
DEFINITION
Three-component, mobile-bearing total ankle arthroplasty system indicated for 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
60% of surface area covered by articular cartilage
Dual radius of curvature
Distal tibiofibular syndesmosis
Anterior inferior tibiofibular ligament
Interosseous membrane
Posterior tibiofibular ligament
Ankle functions as part of the ankle–hindfoot complex much like a mitered hinge.
PATHOGENESIS
Post-traumatic arthrosis
Most common cause
Intra-articular fracture
Ankle fracture-dislocation with malunion
Chronic ankle instability
Primary osteoarthrosis
Relatively rare compared to hip and knee arthrosis
Inflammatory arthropathy
Most commonly rheumatoid arthritis
Other
Hemochromatosis
Pigmented villonodular synovitis
Charcot neuroarthropathy
Septic arthritis
NATURAL HISTORY
Post-traumatic 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:
Relative anterior subluxation of the talus
Varus tilt of the talus within the ankle mortise
Hindfoot varus position
Primary osteoarthrosis of the ankle 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
History
Typically, history of trauma to the ankle
Intra-articular ankle fracture (bior tri-malleolar ankle fracture; tibial plafond [pilon] fracture)
Chronic ankle instability
Inflammatory arthropathy
Primary ankle arthritis
Symptoms or complaints
Pain in anterior ankle with weight bearing and particularly with forced dorsiflexion
Often relieved by rest, but patient may have pain even at rest after vigorous activity or prolonged standing
Ankle swelling
Ankle stiffness
Medications
If patient is taking anti-inflammatory agents, these will need to be stopped preoperatively to limit the risk of perioperative bleeding.
Rheumatoid medications may need to be stopped perioperatively to optimize wound healing and bone ingrowth into the prosthesis.
Physical examination
Alignment
Ipsilateral limb alignment, not simply ankle alignment. The lower extremity should be examined from the hip to the foot. Optimal limb alignment is essential for longevity of the implant.
Ankle–foot alignment
The ankle functions as part of an ankle–subtalar joint complex.
The total ankle needs a solid, well-aligned platform on which to rest.
Hindfoot, midfoot, and even forefoot malalignment may need to be addressed as part of total ankle arthroplasty.
Range of motion (ROM)
Preoperative ankle ROM often dictates postoperative ROM. A stiff ankle before surgery may be a stiff ankle after surgery, despite total ankle arthroplasty. Dorsiflexion may be limited by anterior tibiotalar osteophytes, a tight Achilles tendon or posterior capsular contracture, or both. The examination may identify a distinction between anterior impingement and a tight heel cord.
Hindfoot ROM: Limitations in ROM of the hindfoot may place eccentric stresses on the implant.
Soft tissues
An intact, relatively healthy soft tissue envelope surrounding the ankle is less likely to have soft tissue complications postoperatively, provided careful soft tissue handling is maintained.
Previous surgical scars must be considered. Either they can be incorporated into the surgical approach or the surgical approach may be modified to limit postoperative wound complications
Vascular status: Intact pulses and satisfactory refill must be confirmed; if not, a Doppler ultrasound, noninvasive vascular studies, or both must be performed before considering surgery.
Neurologic status: A peripheral neuropathy is a relative contraindication for total ankle arthroplasty, but in our opinion well-controlled diabetes without neuropathy is not. Established neuropathy and either existing or high risk of Charcot neuroarthropathy is a contraindication for total ankle arthroplasty.
Motor function: Intact motor function of the ankle and foot is essential to successful total ankle arthroplasty. In particular, lack of active dorsiflexion is a relative contraindication to total ankle arthroplasty. It is important to distinguish between anterior impingement or Achilles contracture or posterior capsular tightness versus lack of satisfactory tibialis anterior tendon function.
IMAGING AND OTHER DIAGNOSTIC STUDIES
Weight-bearing AP, lateral, and mortise views of the ankle (FIG 1A,B)
Weight-bearing AP, lateral, and oblique views of the foot, particularly with associated foot deformity
We routinely obtain weight-bearing mechanical axis (hip-toankle) views of both extremities (FIG 1C).
We typically evaluate complex or ill-defined ankle–hindfoot patterns of arthritis with or without deformity using CT of the ankle and hindfoot.
If we suspect avascular necrosis of the talus or distal tibia, we obtain an MRI of the ankle.
Electrodiagnostic studies are indicated with lack of active dorsiflexion that is not due simply to Achilles contracture, posterior capsular tightness, or anterior impingement.
DIFFERENTIAL DIAGNOSIS
See the “Pathogenesis” section above.
NONOPERATIVE MANAGEMENT
Activity modification
Bracing
Ankle–foot orthosis
Double upright brace attached to shoe
Stiffer-soled shoe with a rocker-bottom modification
Nonsteroidal anti-inflammatories or COX-2 inhibitors
Medications for systemic inflammatory arthropathy
Corticosteroid injection
Viscosupplementation
SURGICAL MANAGEMENT
Preoperative Planning
The surgeon must be sure the patient has satisfactory perfusion to support healing and is not neuropathic.
Noninvasive vascular studies and potential vascular surgery consultation if necessary
FIG 1 • Preoperative weight-bearing radiographs of a 75-year-old man with end-stage ankle arthritis. A. AP view of ankle. B. Lateral view of ankle. C. Full-length mechanical axis views to rule out proximal malalignment.
The surgeon must understand the clinical and radiographic alignment of the lower extremity, ankle, and foot.
The surgeon must be prepared to balance and realign the ankle. Occasionally, this necessitates corrective osteotomies of the distal tibia or foot, hindfoot arthrodesis, ligament releases or stabilization, and tendon transfers.
The surgeon should determine whether the coronal plane alignment is passively correctable; this provides some understanding as to whether ligament releases will be required.
Ankle ROM is determined (FIG 2A,B).
Ankle stiffness, particularly lack of dorsiflexion, needs to be corrected:
Anterior tibiotalar exostectomy
Posterior capsular release
Occasionally, tendo Achilles lengthening
Instrumentation
These instruments facilitate total ankle arthroplasty:
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
FIG 2 • Preoperative weight-bearing radiographs of same patient in Figure 1. A. Preoperative dorsiflexion. B. Preoperative plantarflexion.
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
Supine
Plantar aspect of operated foot at end of operating table
Foot and ankle well balanced with toes directed to the ceiling
A bolster under the ipsilateral hip prevents undesired external rotation of the hip.
We routinely use a thigh tourniquet and regional anesthesia.
A popliteal block provides adequate pain relief postoperatively, particularly if a regional catheter is used. Moreover, hip and knee flexion–extension is not forfeited, facilitating safe immediate postoperative mobilization.
However, using a thigh tourniquet with a popliteal block typically requires a supplemental femoral nerve block (patient forfeits knee extension) or general anesthesia.
Approach
Anterior approach to the ankle, using the interval between the tibialis anterior (TA) tendon and the extensor hallucis longus (EHL) tendon
TECHNIQUES
APPROACH
Make a longitudinal midline incision over the anterior ankle, starting about 10 cm proximal to the tibiotalar joint and 1 cm lateral to the tibial crest.
Continue the incision midline over the anterior ankle just distal to the talonavicular joint.
At no point should direct tension be placed on the skin margins; we perform deep, full-thickness retraction as soon as possible to limit the risk of skin complications.
Identify and protect the superficial peroneal nerve by retracting it laterally.
In our experience there is a consistent branch of the superficial peroneal nerve that crosses directly over or immediately proximal to the tibiotalar joint.
We then expose the extensor retinaculum, identify the course of the EHL tendon, and sharply but carefully divide the retinaculum directly over the EHL tendon.
We always attempt to maintain the TA tendon in its dedicated sheath.
Preserving the retinaculum over the TA tendon prevents bowstringing of the tendon and thereby reduces the stress on the anterior wound. Should there be a wound dehiscence, then the TA is not directly exposed. Preserving the retinaculum over the TA tendon is not always possible; some patients do not have a dedicated sheath for the TA.
Use the interval between the TA and EHL tendon, with the TA and EHL tendons retracted medially and laterally, respectively (TECH FIG 1).
Identify the deep neurovascular bundle (anterior tibial–dorsalis pedis artery and deep peroneal nerve) and carefully retract it laterally throughout the remainder of the procedure.
Perform an anterior capsulotomy and elevate the tibial and dorsal talar periosteum to about 6 to 8 cm proximal to the tibial plafond and talonavicular joint, respectively.
Elevate this separated capsule and periosteum medially and laterally to expose the ankle, access the medial and lateral gutters, and visualize the medial and lateral malleoli.
Remove anterior tibial and talar osteophytes to facilitate exposure and avoid interference with the instrumentation.
TECH FIG 1 • Anterior approach to the ankle.
EXTERNAL TIBIAL ALIGNMENT GUIDE
Position the tibial alignment jig so that the clamp adjustment bar lies over the anterior crest of the tibia and the bar is parallel to the long axis of the tibia (TECH FIG 2A).
The proximal end of the alignment jig is held in position by a 2.5-mm stabilizing pin.
The adjustment tube on the yoke post and the extending tibial rod should be parallel to the tibia, or with deformity, aligned with the mechanical axis of the leg.
Adjust alignment to obtain proper positioning for the cutting block at the tibial plafond (TECH FIG 2B).
Reference the tibial cutting block to the medial and lateral sides of the talus (TECH FIG 2C).
Drill two 2.5-mm pins into the tibia through the guide holes to stabilize the tibial cutting block.
The configuration of the guide holes allows adjustment of the cutting block proximally or distally by increments of 2.5 mm to optimize the level of tibial resection.
TECH FIG 2 • External tibial alignment guide parallel to the tibial shaft axis. A. Lateral view. B. Anterior view. C. Initial tibial preparation, cutting block set for initial resection.
TIBIAL PREPARATION
Initial Tibial Resection
The tibial resection is performed with an oscillating saw (TECH FIG 3A).
With an asymmetric wear pattern in the tibial plafond, the resection may not be congruent but should be perpendicular to the tibial shaft axis or, with deformity, to the mechanical axis.
In our experience, a stiff ankle warrants resection of 2 or 3 mm of distal tibia in excess of the resection needed to create sufficient room for the combined thickness of the implants.
Do not attempt to remove the resected tibial bone until making a vertical tibial cut that is a vertical extension of the medial gutter of the ankle (TECH FIG 3B). This protects the medial malleolus from fracture.
Do not lever on either malleolus while removing the resected bone because of the risk of fracture.
Use the gap template to confirm and adequate tibial resection to accommodate the thickness of the tibial implant and thinnest mobile polyethylene bearing (TECH FIG 3C). If the guide does not fit in the space, further bone resection is required (TECH FIG 3D,E).
TECH FIG 3 • Initial tibial preparation. A. Oscillating saw. B. Vertical cut to complete initial tibial cut (protects medial malleolus from potential fracture). C. Gap template matches thickness of tibial base plate and the thinnest polyethylene bearing. D. Cutting block moved 2 mm more proximally on same pins to allow greater resection in same plane as initial cut. E. Repeat resection.
Tibial Sizing
Use the tibial sizing gauge to determine the optimal tibial component size in the AP dimension (TECH FIG 4A).
The talar component may be of equal in size or smaller than the tibial component (TECH FIG 4B), but it cannot be larger than the tibial component (TECH FIG 4C).
Place the gauge on the prepared tibial surface and hook it on the posterior aspect of the tibia (TECH FIG 4D,E).
The proper component size is based on the markings on the upper surface of the gauge.
Select the corresponding tibial profile guide to confirm that the size determined from the AP dimension is also appropriate in the medial-to-lateral dimension. If not, then downsizing is necessary.
The tibial components are sized 1 through 6, with 1 being the smallest and 6 being the largest.
Subsequent tibial cuts will be specific for the size of implant selected at this stage.
TECH FIG 4 • Tibial sizing. A. Tibial sizing gauge adjacent to corresponding tibial trial. B. Tibial sizing gauge next to talar trial. C. Corresponding tibial sizing gauge, tibial trial, and talar trial. D, E. Tibial sizing using the tibial sizing gauge. D. Gauge being introduced to joint. E.Gauge hooked on posterior tibial cortex.
Tibial Window Resection
Select the tibial template corresponding to the size determined from the guides used for sizing (TECH FIG 5A).
Fit the tibial window cutting block to the tibial template and secure it with the system handle adapter.
Place the assembly flush on the prepared tibial surface, with the tibial template flat against the resected plafond and the tibial window cutting block held firmly against the anterior tibia (TECH FIG 5B).
The scissor distractor supports the tibial window cutting block–tibial template assembly.
Use a 6-mm tibial drill to prepare the proximal aspect of the tibial window resection.
Drill to the depth stop.
Insert a tibial window peg to stabilize the tibial window cutting block.
Remove the system handle but leave the scissor distractor to further stabilize the tibial window cutting block–tibial template assembly.
TECH FIG 5 • Tibial window preparation. A. Tibial window cutting block adjacent to its corresponding tibial template–sizing gauge. B. Tibial window cutting block assembled to the tibia template and placed flush against initial tibial prepared surface and flush with the anterior tibial cortex. C.After drilling proximal hole and placing a stabilizing post, the oscillating saw is used to cut the anterior tibial window. D. Tibial window extractor. E. Tibial window impactor to finalize window preparation. F. Tibial trial confirming satisfactory window preparation.
Immediately adjacent to the window cutting block, cut the medial and lateral sides of the window with an oscillating saw (TECH FIG 5C).
Mark the appropriate depth on the saw blade corresponding to the size of tibial component to be implanted.
After preparing the tibial window sides, remove all instruments.
Position the tibial window extractor on the distal tibial surface.
The appropriate mark on its upper surface must be positioned against the anterior tibial cortex.
By carefully levering against the talus, force the cutting edge of the tibial window extractor into the firm subchondral bone of the distal tibia, thereby releasing the bony resection (TECH FIG 5D).
Retain this bone segment, as it is replaced after trimming at a later stage.
Use the tibial window impactor to compact the most proximal cancellous bone in the tibial window to the required depth, indicated by the markings on the impactor (ie, size 1 through 6; TECH FIG 5E).
Insert the tibial trial to be sure it fits appropriately and is perfectly centered over the talus (TECH FIG 5F).
TALAR PREPARATION
Superior Talar Flat Resection
Assemble the tibial template used to make the tibial window resections with the tibial template post and the talar pin jig. The assembly is secured with the system handle adapter.
There are four talar pin jigs: 5 mm, 7 mm, 9 mm, and 11 mm.
Estimate the bearing insert thickness that is appropriately sized and avoids excessive dorsiflexion of the ankle.
Place the tibial template, tibial post, and talar pin jig assembly in the resected tibial window (TECH FIG 6A). Use the system handle to hold this assembly in position.
With the correct-thickness talar pin jig in place, hold the foot 90 degrees to the lower leg, and insert the first 2.5-mm pin through the talar guide (TECH FIG 6B). The foot must be held at 90 degrees relative to the lower leg; this is essential during talar drill pin insertion.
Insert a second pin into one of the two other holes (TECH FIG 6B). Avoid the medial and lateral extremes of the talus.
Remove all the instruments but leave the 2.5-mm talar drill pins, which should be parallel to the long axis of the talus (TECH FIG 6C).
Slide the “standard” talar flat cutting block onto the 2.5-mm pins with the groove uppermost and on the left.
Resect the superior flat of the talus (TECH FIG 6D,E). Keep the saw blade flush with the cutting block.
TECH FIG 6 • Initial talar preparation (superior talar flat cut). A. Tibial template, tibial post, and talar pin guide assembly in place. B. With ankle at neutral position, talus is pinned through the talar pin guide. C. Talar pins in appropriate position. D. Oscillating saw for the superior talar flat cut. E. Initial talar preparation completed.
Transfer of Joint Center to Talus
Assemble the talar center guide (TECH FIG 7A,B).
Insert the tibial template into the resected tibial window with the 2.5-mm drill pins and the talar flat cutting block still in position (TECH FIG 7C).
Align the foot into the neutral position and guide the locating runners on the talar center guide into the grooves in the tibial template superiorly and the groove in the talar flat cutting block inferiorly.
Once the correct spacing is achieved, advance the talar center guide until the superior runners contact the end of the tibial template grooves. Use a center guide packing between the talar center guide and the tibial template if the space between the tibia and the talus is excessive.
Advance the stop block until it meets the front of the talar flat cutting block and lock it into position using the locking screw.
Plantarflex the ankle and remove the tibial template.
Adjust the talar center guide on the talar flat cutting block so that the talar center guide’s stop block contacts the top of the talar flat cutting block.
The two bands marked on the talar center guide correspond to two ranges within the six available talar component sizes.
The AP length of the talar flat must be at least equal to the bands for the smallest range of sizes marked on the talar center guide.
If the AP talar flat is less than the bands marked on the talar center guide, then more superior talar flat must be resected.
Use the “low” talar flat cutting block to remove more of the superior talus.
At this point a decision must be made whether the optimal talar size falls in the size range 1–4 or 5–6. The anterior and posterior chamfer cuts are the same within these respective ranges but different as the size transitions from size 4 to 5.
The size of the bearing insert component must match the size of the talar component.
The size of the talar component and bearing insert must be smaller than or equal to that of the tibial component selected to prevent overhang of the bearing compared to the tibial plate.
The sizes of subsequent cutting blocks used to further resect the talus are based on the talar size selection.
Once the appropriate amount of talar flat cut has been confirmed, properly position the talar center guide against the talar flat cutting block and insert a 2.5-mm guide pin into the talus (TECH FIG 7D).
TECH FIG 7 • Transferring joint center to talus. A, B. Assembling the talar center guide. C. Advancing the talar center guide on the talar pin guide. D. With the talar center guide appropriately positioned on the initial talar cut, the guide pin is drilled into the talus. E. Center pin position confirmed.
The forked end of the talar center guide determines the position for the 2.5-mm pin.
Insert the pin at about 60 degrees relative to the superior talar flat.
This 2.5-mm pin identifies the AP center of the tibial component in relation to the talus.
Visually confirm that the 2.5-mm pin is in the AP center of the talus (TECH FIG 7E).
If the pin is not in the optimal position, repeat the transfer of the joint center and reposition the 2.5-mm guide pin in the exact AP center of the talus. flat cut until it abuts the 2.5-mm talar guide pin (TECH FIG 8A).
Anterior and Posterior Talar Flat Resection
Remove the talar center guide but leave the 2.5-mm guide pin and the talar flat cutting block in position.
Select the talar fin drill guide, either size 1–4 or size 5–6, to correspond to the size of talar component to be implanted, and attach it to the system handle.
Guide the runner on the underside of the fin drill guide into the groove on the left side of the talar flat guide and advance the forked end along the resected talar
Using the system handle to hold the fin drill guide in position, drill four holes into the talus using the 4.5-mm drill bit (TECH FIG 8B). Be sure to seat the drill fully against the talar fin guide so that the holes are created to the required depth.
Remove the talar fin drill guide, the talar flat cutting block, and all 2.5-mm guide pins from within the joint space (TECH FIG 8C).
Trephine Guide
Select the appropriate trephine guide (either size 1–4 [blue] or size 5–6 [green]) to correspond to the size of talar component to be implanted, and attach it to the system handle (TECH FIG 9A).
The four posts in the trephine guide fit into the four drill holes made in the talus, and the guide is held in position using the system handle (TECH FIG 9B).
Two posts are marked “A” for anterior and must be inserted into the anterior two holes in the talus.
The other two posts are marked “P” for posterior and must be inserted into the posterior two holes in the talus.
TECH FIG 8 • Talar fin drill guide. A. Guide positioned. B. Initial fin preparation. C. Initial talar fin preparation with talar fin drill guide removed.
TECH FIG 9 • Talar trephine and posterior chamfer guides. A. Trephine guide adjacent to corresponding talar component. B. Trephine guide positioned on talus. C. After trephine preparation.
Trephine the superior and posterior talar sulcus using the specifically designed depth-stopped trephine.
After the superior and posterior sulci have been trephined, remove the trephine guide (TECH FIG 9C).
Posterior Chamfer Preparation
Select the appropriate posterior cutting block (either size 1–4 [blue] or size 5–6 [green]) to correspond to the size of talar component to be implanted, and attach it to the system handle.
The two posts on the posterior cutting block are marked “A” for anterior. These posts must be inserted into the anterior holes in the talus.
In the proper position, the tongue of the posterior cutting block will sit flush in the posterior sulcus that has just been trephined. The scissor distractors may be used to steady the cutting block.
Resect the posterior talar flat and remove the posterior cutting block (TECH FIG 10).
TECH FIG 10 • Posterior chamfer guide positioned and posterior chamfer cut being performed with an oscillating saw.
Anterior Chamfer Preparation
Select the appropriate anterior milling guide (either size 1–4 [blue] or size 5–6 [green]) to correspond to the size of talar component to be implanted, and attach it to the system handle (TECH FIG 11A,B).
The two posts on the anterior milling guide are marked “P” for posterior; these posts must be inserted into the posterior holes in the talus.
In the correct position the posterior face of the jig will be aligned with the resected posterior talar flat.
The scissor distractors may be used to steady the jig.
The talar anterior mill has a depth stop and is moved throughout the guide to prepare the anterior chamfer (TECH FIG 11C).
The anterior milling guide restricts the mill from completely preparing the entire anterior chamfer.
TECH FIG 11 • A–C. Anterior talar chamfer preparation. A. Anterior chamfer mill and guide. B. Depiction of the recess created by the mill for the talar component. C. Talar milling for anterior chamfer preparation. D–G. Final talar preparation. D. Talar sulcus osteotome. E. Talar profile template to confirm adequate sulcus preparation. F, G. Completion of the talar fin slots.
After removing the anterior milling guide, use a rongeur to remove residual anterior bony prominences.
Finish the superior and posterior sulci by using the sulcus osteotome and the sulcus burr (TECH FIG 11D).
The talar profile template confirms satisfactory preparation of the talus (TECH FIG 11E).
Use the fin osteotome, the rongeur, or both to remove the small piece of bone between the anterior and posterior drill holes guided by the plastic fin angle guide (TECH FIG 11F,G).
TRIAL INSERTION
There are six sizes of talar and tibial trials corresponding to the six available final component sizes.
The size of talar implant must match or be smaller than the size of the tibial implant.
Insert the proper talar trial, narrow aspect directed posteriorly. The tibial window serves as a convenient access for the talar impactor (TECH FIG 12A).
Select the trial tibial component corresponding to the prepared tibial window and insert it straight anterior to posterior within the distal tibial window resection.
The curved aspect of the component is directed posteriorly.
The articular surface of the tibia component will be positioned about 85 degrees to the long axis of the leg.
The anterior aspect of the component should be flush with the anterior cortex of the tibia.
The posterior aspect of the component may overhang the rear of the tibia by 1 mm in the midpoint but should not do so near the malleoli as it may irritate the neurovascular bundle, tendons, or posterior soft tissues.
The medial and lateral dimensions of the tibial trial ideally should match the tibial resection. Most importantly it must cover all aspects of the polyethylene insert (TECH FIG 12B).
The bearing insert is available in the six sizes, and there are five different thicknesses.
The six sizes of bearing insert trials are color-coded according to size (1, black; 2, brown; 3, purple; 4, yellow; 5, hot pink; 6, red).
The trial bearing insert’s handle facilitates bearing removal without restricting trial joint motion or obstructing visualization of the resurfaced joint (TECH FIG 12C).
Confirm proper alignment and trial component position fluoroscopically (TECH FIG 12D–F). Also confirm that there is no indication of stress fracture
Confirm that the ankle is balanced and that ROM is adequate, particularly dorsiflexion beyond neutral (TECH FIG 12G,H).
TECH FIG 12 • Trial components. A. Impacting talar trial. B. Inserting tibial trial and trial bearing. C. All trial components in place. D–F. Fluoroscopic confirmation. G, H. Adequate dorsiflexion and plantarflexion.
FINAL COMPONENT INSERTION
The tibial and talar components are intended for uncemented use (TECH FIG 13A).
Seat the talar component with the narrow aspect of the component directed posteriorly and the keel fins directed in line with the slots.
Use the component impactor, which can be positioned in the tibial window so that the posterior talus may be fully seated.
To avoid anterior tilt of the component, we routinely place an instrument under the anterior aspect of the component during initial impaction (TECH FIG 13B).
Protect the articulating surface of the talar component with a trial insert bearing and insert the tibial component.
The curved aspect of the component is directed posteriorly.
Ensure that the implant is seated firmly on the prepared distal surface of the tibia (TECH FIG 13C,D).
Check for any osteophytes that might impinge within the joint and trim if needed, taking care not to damage the polished articulating surfaces.
Make the final decision about the thickness of the bearing, using trials as necessary.
Insert the final polyethylene bearing (TECH FIG 13E).
Trim and replace the resected bone in the tibial window, using slivers of bone in the saw cuts to enhance the stability of the “graft” (TECH FIG 13F–I).
Be sure that motion is adequate, particularly dorsiflexion (TECH FIG 13J–L).
Confirm proper alignment and implant position fluoroscopically. Also confirm that there is no indication of stress fracture.
TECH FIG 13 • Final implants. A. Surfaces prepared for cementless implantation. B. The anterior lip of the talar component is supported during its initial insertion to keep it from tilting anteriorly. C, D. Tibial component insertion (note use of a bearing trial to support the tibial component during insertion and to protect the talar component). E. Final components in place, including mobile bearing. F–L. Final steps of implantation. F. Replacing anterior tibial cortical fragment that was removed to create tibial window. G. The cancellous portion must be carefully trimmed. H–J. Anterior cortex fragment in place and then impacted. K, L. Adequate motion confirmed.
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.
The pin should have already been removed from the proximal tibia.
Reapproximate the capsule.
Use of a drain is by surgeon preference.
Release the tourniquet and obtain meticulous hemostasis.
Reapproximate the extensor retinaculum while protecting the deep and superficial peroneal nerves.
Irrigate the subcutaneous layer with sterile saline and then reapproximate it.
Reapproximate the skin to a tensionless closure.
Place sterile dressings on the wounds, adequate padding, and a short-leg cast with the ankle in neutral position.
POSTOPERATIVE CARE
Overnight stay
Nasal oxygen while in hospital
Touch-down weight bearing on the cast is permitted, but elevation is encouraged as much as possible.
Follow up in 2 to 3 weeks for suture removal and transition to a cam boot
Weight bearing to tolerance starting at 3 weeks
If the wound is stable, supervised therapy to reduce edema and optimize motion.
At 6 weeks after surgery, weight-bearing radiographs of the ankle are obtained (FIG 3).
If the wound is stable and radiographs suggest early bone ingrowth and no signs of stress fracture, weight bearing is gradually advanced and the patient is transitioned to a regular shoe.
FIG 3 • Follow-up weight-bearing radiographs. A. AP view of ankle. B. Lateral view of ankle. C. Dorsiflexion. D. Plantarflexion.
If there is no evidence of stress fracture or failure of the procedure, then the patient can progress to a regular shoe and full weight bearing.
OUTCOMES
While some recently reported outcomes are based on highlevel evidence, results of total ankle arthroplasty are almost uniformly derived from level IV evidence.
Functional outcome using commonly used scoring systems for total ankle arthroplasty (AOFAS [Kofoed, Mazur] and NJOH [Buechel-Pappas]) suggest uniform improvement in all studies, with follow-up scores ranging from 70 to 90 points (maximum 100 points).
Patient satisfaction rates for total ankle arthroplasty exceed 90%, although follow-up data for patient satisfaction often do not exceed 5 years.
Overall survivorship analysis for currently available implants, designating removal of a metal component or conversion to arthrodesis as the endpoint, ranges from about 90% to 95% at 5 to 6 years and 80% to 92% at 10 to 12 years.
At the time of this writing there are no published results available for the Mobility total ankle arthroplasty.
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
Medial malleolar stress fracture
Implant fracture (including polyethylene)
REFERENCES
1. Gougoulias N, Khanna A, Maffulli N. How successful are current ankle replacements? A systematic review of the literature. Clin Orthop Relat Res 2010;468(1):199–208.
2. Haddad SL, Coetzee JC, Estok R, et al. Intermediate and long-term outcomes of total ankle arthroplasty and ankle arthrodesis: a systematic review of the literature. J Bone Joint Surg Am 2007;89A:1899–1905.
3. Stengel D, Bauwens K, Ekkernkamp A, et al. Efficacy of total ankle replacement with meniscal-bearing devices: a systematic review and meta-analysis. Arch Orthop Trauma Surg 2005;125:109–119.
4. 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;91B:69–74.