Total Ankle Arthroplasty: Surgical Technique

Fig. 14.1

(a) Anteroposterior radiograph showing loosening of a Ramses model prosthesis. (b) A replacement was performed by Agility prosthesis. It is one of the first revision surgeries performed by the authors. Since no current revision components were available at the time, an Agility prosthesis was implanted with good functional results. To date, no new revision has been necessary. In addition, the arthrodesis of tibiofibular syndesmosis was indicated with this model

Lachman et al. [5] have published failure rates in their series of 10% prosthetic revisions, which are comparable to previously reported failure rates in primary ankle prostheses and tibiotalar arthrodeses [6, 7]. In addition, tibiotalar arthrodesis with allograft block, which was considered the gold standard, frequently engenders complications and reoperations, and the patient is often not satisfied with the intervention. The rate of reoperation after arthrodesis can reach up to 41% often due to the development of osteoarthritis in adjacent joints [8, 9].

The main challenges in rescuing an ankle prosthesis that has failed include finding the right prosthesis for the revision, exhaustively planning the management of bone defects and underlying infection, and the possible concomitant procedures necessary to achieve good alignment and stability of the ankle prosthetic components.

14.2 Indications and Contraindications

The main indications for revision of an ankle prosthesis include loosening and sinking of the talus component. According to Myerson et al. [10], there are no limits regarding the extent of the collapse or loss of bone stock in the talus, given that nothing prevents the use of a revision system, particularly when a flat cut can be made in the talus. Previously, a significant loss of bone stock in the talus was a contraindication for prosthetic revision. As we will see in this chapter, however, arthrodesis can be avoided using a large structural graft or certain prosthetic models.

Some authors consider the presence of recent or ongoing infection as a contraindication. However, it is possible to perform a rescue and implant a new prosthesis following proper guidelines and planning. The presence of chronic pain or a damaged soft tissue envelope with excessive scarring or previous healing problems can be contraindications.

14.3 Ankle Prosthesis Revision for Aseptic Loosening With or Without Sinking of the Components

In an ankle prosthesis, the force that supports the bone is at least three times greater than under normal conditions. For this reason, the fixation of the metallic components must ensure appropriate stability during physical activities and must also prevent sinking.

In the aseptic loosening of the tibial component, the cortex of the tibial metaphysis becomes sclera, and in the center the spongy bone mass decreases or bone cysts form. In contrast, when loosening of the talus component occurs, it can increase sclerosis in the anterior and posterior part of the talus, resulting in the formation of cysts in these locations.

We have also frequently observed that those patients who present loosening with prosthetic sinking have vitamin D levels well below normal limits. Future studies will be necessary to observe whether there is a cause-effect relationship; for now, the authors recommend always making a determination of vitamin D levels before revision surgery and supplementing with vitamin D when necessary [11, 12].

When an ankle prosthesis revision surgery is indicated, several problems must be addressed (Fig. 14.2). To determine its importance, we must perform a thorough physical and radiological examination. It is necessary to evaluate the coronal alignment of the leg and hindfoot; for this, we must observe how the patient walks, observing the patient from behind; and also evaluate the alignment while standing, statically, on a podoscope (to detect misalignment in the varus or valgus, or pronation or supination of the midfoot). Regarding sagittal misalignment, equine contracture can be related to a shortening of the gastrocnemius muscles or the Achilles tendon, which plays an important role in the correction of the hindfoot.

../images/479782_1_En_14_Chapter/479782_1_En_14_Fig2_HTML.png — Fig. 14.2

Problems to be addressed when a revision total ankle arthroplasty (RTAA) is indicated. *TAA* total ankle arthroplasty

To evaluate the radiographic evolution, we need to obtain an X-ray of lateral and anteroposterior loading of the ankle and foot before the surgery, and a hindfoot projection (Saltzman view). Occasionally, a lower limb standing radiograph might be necessary to assess varus or valgus deformities of the shaft or tibial metaphysis.

A computed tomography (CT) scan allows us to determine the extent of bone destruction (Fig. 14.3) and to anticipate the need for bone grafts, custom-made ankle prostheses, or prostheses with diaphyseal anchor tibial stems (such as the INBONE total ankle replacement system), or talar support plates (such as the INVISION total ankle replacement system. Modalities such as single-photon emission CT and fluorodeoxyglucose positron emission CT can identify pathological situations around the prosthetic components.

../images/479782_1_En_14_Chapter/479782_1_En_14_Fig3_HTML.jpg — Fig. 14.3

Computed tomography (CT) scan axial cut showing extensive osteolysis and poor bone quality around the tibial stem of the talus component

Hintermann et al. use an algorithm based on the size of the bone defect in the tibia and the talus to plan revision surgeries [13]. However, this approach only appears applicable in the case of using the Hintegra prosthesis and its revision components.

These algorithms are not used in our usual practice. We support other prosthetic models that allow bone defects to be resolved based on stability and diaphyseal support in the case of the tibia or the use of talar plateaus of various sizes that recover a flat surface and with cortical support on which to implant the talar dome.

14.4 Technique for Removing an Ankle Prosthesis

Some essential first steps should be taken to reach the prosthetic implants that have failed.

With the patient in the supine position, make an incision incorporating the previous anterior incision in the midline.
Identify and protect the dorsal medial cutaneous branch of the superficial peroneal nerve, which falls superficially to the extensor retinaculum and can be surrounded by scar tissue. The surgeon should keep in mind that fibrous and scar tissue can prevent proper bone preparation, while increasing the risk of neurovascular injury.
Identify the extensor reticulum and section it longitudinally to the neck of the talus. We use a Vicryl 1 suture to mark and identify both flaps of the retinaculum, and repair it. Next, the interval between the tibialis anterior tendon and the extensor hallucis longus should be deepened, protecting the neurovascular bundle.
Limit as far as possible the placement of aggressive separators to prevent complications in the healing of soft tissues.
Once the tibia is exposed, insert the capsule over the ankle joint and place a medial and lateral Hoffman-type separator.
Extract the loosened prosthetic components. First, extract the polyethylene. Sometimes, according to the prosthetic model, specific instruments can be used for their extraction; however, if the models are older, acquiring these instruments is not always possible. In those cases, the polyethylene must be sectioned in its middle and extracted in parts. Another possibility is to drill the polyethylene on both sides, thus loosening it for its extraction. With respect to the tibial and talar components, they are often loosened and easily removed. If there are areas with good bone anchoring, the use of small chisels can be helpful to detach the implant, preserving as much bone as possible.
The medial and lateral droplets should be debrided exhaustively, and the posterior capsule should be resected, avoiding the neurovascular structures in the posteromedial area.

When we have the bony surfaces free of prosthetic implants, we can focus on each specific area: tibia and talus.

14.5 Aseptic Loosening of the Tibial Component

One of the major surgical concerns is the bone stock that can remain after the extraction of the prosthesis. Some causes for this loss of bone stock include an excessive resection in the primary intervention, loosening and sinking of the component, osteolysis, cyst formation, and bone loss during extraction and infection. It is essential to observe bone surfaces with good bleeding after removing the prosthesis and to perform a thorough debridement of the fibrosis.

Before beginning the surgical technique for the prosthesis to be implanted, we attempt to get flat and parallel surfaces to the ground, making cuts with a saw guided by fluoroscopy (Fig. 14.4). If the prosthesis to be implanted is not a revision, it is very important to keep the anterior and posterior cortex as undamaged as possible, given the tibial plate will rest on that tibial cortical ring. However, if the quality of the distal metaphyseal cortices is poor, it is useful to opt for a prosthesis with a tibial stem, which can have a variety of lengths (INBONE II prosthesis) and achieve greater diaphyseal support, without completely depending on the distal tibial cortex.

../images/479782_1_En_14_Chapter/479782_1_En_14_Fig4_HTML.jpg — Fig. 14.4

Intraoperative fluoroscopy image after making tibial and talar cuts parallel to each other and parallel to the ground plane before placing the cutting templates of a particular prosthetic model

We consider from the outset that the implant support on the distal tibial cortices of our patients will be insufficient, and a greater diaphyseal support will always be necessary to achieve a satisfactory stability and to decrease the risk of subsidence of the tibial component (Fig. 14.5).

../images/479782_1_En_14_Chapter/479782_1_En_14_Fig5_HTML.jpg — Fig. 14.5

Anteroposterior radiograph showing INBONE II prosthesis with modular tibial stem, implanted after prosthetic revision due to loosening of the tibial and talar components. It was not necessary to use revision components. Note also the osteosynthesis that was performed in an intraoperative tibial malleolus fracture

If there are important cysts or bone defects, they should first be debrided and curetted until the healthy subchondral bone is visible. Afterward, the cysts should be filled with a cancellous bone autograft of the proximal tibia and/or of the ipsilateral iliac crest. The additional use of cement can secure the prosthetic anchor and provide good results. Opt for an allograft only in cases needing large amounts of bone graft, which is unlikely, given that a sufficient autograft is typically obtained (which also has better characteristics for osteointegration). It is important to compact it well to prevent early resorption.

In case of a longitudinal bone defect, to restore the height of the joint line, thicker revision tibial components can be used, such as the Hintegra prosthetic system with 8 mm and 12 mm tibial components, or the INVISION prosthetic system that adds +4 mm or + 8 mm at the usual height of the INBONE II tibial component (Fig. 14.6).