Total Ankle Replacement




Abstract


Selection of the treatment approach for ankle arthritis should not be the surgeon’s decision alone. Many patients recognize the potential problems with ankle arthrodesis, the inherent stiffness, the limitation to certain activities, and in particular the likelihood of adjacent joint arthritis developing in the future. Within this group of patients, however, some prefer not to deal with potential for failure of an ankle replacement and want more predictability in the outcome and therefore select the arthrodesis. We outline all of the potential advantages and disadvantages, as well as the possibility of complications for each procedure; selection of the most appropriate procedure then becomes a joint decision that the patient and we make together. There are certain patients who should preferably not undergo an ankle replacement even if many of the other prerequisites are met, including those with severe osteopenia, severe avascular necrosis, those with neuropathy, patients who are young and very active, and those who have unrealistic expectations of the outcome of the procedure. On the other hand, there are certain indications for replacement that one can follow, and while not absolute, they are very helpful. These include the patient with bilateral ankle arthritis, the presence of a stiff subtalar joint, good range of motion in the ankle joint, good bone quality, normal alignment of the leg, and those individuals who are engaged in daily activities and who feel that they need more flexibility of the ankle, for example for dancing and yoga.




Key Words

ankle arthritis, arthroplasty, total ankle, replacement, TAA

 




Overview


Replacement Versus Arthrodesis


Who is the ideal candidate for an ankle replacement? What should the surgeon tell a patient who presents with ankle arthritis, and how should decision making proceed in this setting? Selection of the treatment approach should not be the surgeon’s decision alone. For an ideal patient with good alignment, good bone support, and reasonable range of motion, with no contraindication to joint replacement, what is the best surgical advice? There is a learning curve to ankle replacement (total ankle replacement; TAR), which is not the case with ankle arthrodesis. This learning curve has been well established in the literature, and noted and documented for different types of prostheses. It is not possible for us to quantify how many replacements a surgeon should perform before becoming comfortable with the procedure, but what is clear is that there should be a minimum number of TAR performed by an individual surgeon annually to maintain a level of expertise and ability to deal with all types of pre-, intra-, and postoperative problems. While we cannot state with certainty what this number is, from discussions with many surgeons in the field on this topic, it appears that a minimum of 15 TAR should be performed per year to maintain a level of expertise that provides a realistic level of competence.


What are the advantages of ankle replacement over arthrodesis? Is the functional improvement with ankle replacement so much greater than arthrodesis that it warrants performing the procedure despite its much higher complication rate? Many patients recognize the potential problems with ankle arthrodesis, the inherent stiffness, the limitation to certain activities, and in particular the likelihood of adjacent joint arthritis developing in the future ( Fig. 18.1 ). Within this group of patients, however, some prefer not to deal with potential for failure of an ankle replacement and want more predictability in the outcome, and therefore select the arthrodesis. We outline all of the potential advantages and disadvantages, as well as the possibility of complications for each procedure; selection of the most appropriate procedure then becomes a joint decision that the patient and we make together. There are certain patients, however, who should preferably not undergo an ankle replacement even if many of the other prerequisites are met, including those with severe osteopenia, severe avascular necrosis (AVN), those with neuropathy, the patient who is young and very active, and those who have unrealistic expectations of the outcome of the procedure. On the other hand, there are certain indications for replacement that one can follow and, while not absolute, are very helpful. These include the patient with bilateral ankle arthritis, the presence of a stiff subtalar joint, good range of motion in the ankle joint, good bone quality, normal alignment of the leg, and those individuals who are engaged in daily activities and who feel that they need more flexibility of the ankle, for example for dancing and yoga.








Figure 18.1


The development of adjacent joint arthritis is a major medium- and long-term complication of ankle arthrodesis (A and B). While arthritis of the peritalar joints occurs frequently and is often associated with stiffness of the subtalar joint, it becomes symptomatic in approximately 20% of patients who require subsequent surgery (C).


An important consideration in surgical planning is the preoperative range of motion of the ankle. One of the most critical factors affecting the postoperative range of motion is a preexisting contracture, which is often the case with posttraumatic arthritis. The soft tissue envelope around the posttraumatic and arthritic ankle joint is usually quite scarred, at times significantly so. Contractures developing over long-term periods of immobilization further adversely affect the ankle joint mobility. In such cases, it is more difficult to obtain a satisfactory range of motion even intraoperatively, despite good peri-articular soft tissue release. A patient with severe ankylosis may never achieve an acceptable range of motion regardless of how the procedure is performed. For such patients with ankle stiffness, arthrodesis may not be perceived as disabling (in comparison with those in whom the clinical presentation includes a reasonable range of motion but some degree of preoperative pain) ( Fig. 18.2 ). We routinely obtain dynamic lateral plantar flexion and dorsiflexion radiographic views of the ankle during the preoperative evaluation to identify the exact location of sagittal plane motion. The accurate measurement of range of motion of the ankle joint is essential both pre- and postoperatively to determine the true ankle motion instead of the total motion which includes the talonavicular joint. The latter becomes much more relevant postoperatively when the ankle joint may be stiff, and the plantar flexion obtained on examination is that of the talonavicular and not the ankle joint ( Fig. 18.3 ).




Figure 18.2


The range of motion of the ankle is important in surgical decision making and may have no correlation with the radiographic appearance. (A–C). In this example, a patient with hemochromatosis had severe ankle arthritis but retained excellent range of motion. (D–F) By contrast, a patient with posttraumatic arthritis may have no ankle motion at all despite only moderate arthritis as indicated by radiographically evident changes, as in this case. This patient may be a better candidate for an ankle arthrodesis than another patient with excellent motion but with far more extensive radiographic changes, for whom a replacement is preferable.









Figure 18.3


Whether measured pre- or postoperatively, a standardized approach must be taken to the measurement of true ankle range of motion as opposed to total sagittal plane of motion, which includes the talonavicular joint. Presented here are pre- and postoperative x-rays with these measurements (A–D).


Another factor with respect to range of motion has to do with the subtalar joint. A stiff subtalar joint may do better with a replacement than an ankle arthrodesis, since the increased load on the subtalar joint will lead to pain and arthritis quickly unless one proceeds directly to a tibiotalocalcaneal (TTC) arthrodesis. Here again the importance of obtaining a lateral flexion and extension x-ray (XR) of the foot to evaluate not only the ankle but also the subtalar joint comes through. In the standing or the forward or extended view, the subtalar joint may appear to be normal, but only when compared with the flexion view does one appreciate the subtalar arthritis and the now apparent flatfoot deformity. This implies that one may need to correct the flatfoot deformity before or at the same time as the ankle replacement, but it cannot be left alone ( Fig. 18.4 ). Deformity of the foot must be corrected before or at the same time as the replacement. It is not realistic to expect that the outcome of replacement will be satisfactory if the foot is left deformed. We take it for granted that a varus or valgus foot deformity must be corrected, but the same applies to a flatfoot, which places undue stress on the prosthesis. In particular, a flatfoot deformity must be corrected either as a staged procedure or at the same time as the TAR ( Fig. 18.5 ). If a staged procedure is performed, the most important aspect of the hindfoot arthrodesis is planning the incisions. The incision for the talonavicular arthrodesis must be exactly in the location where the incision would be made for the joint replacement (i.e., more laterally than one is accustomed to making with a routine arthrodesis).






Figure 18.4


The effect of flexion and extension of the foot on the subtalar joint is evident here (A and B). In the forward extended view, the foot is flat and the subtalar joint impingement is now apparent with the hindfoot in valgus. This is reversed in the flexion view where the subtalar joint opens up and appears to be quite normal. The implication for this has to do with managing the flatfoot before or at the same time as the replacement.









Figure 18.5


This ankle replacement was not well thought out, since the procedure was performed on a foot that was flat and left unexpected (A and B). The patient was markedly symptomatic 6 months following surgery, and required revision. However, instead of revising the joint replacement, the flatfoot was corrected leading to a good outcome, leaving the replacement intact (C and D).


Peritalar arthritis is not a contraindication to performing ankle replacement. There have been no studies that indicate a quicker or higher rate of failure following hindfoot arthrodesis performed either before or simultaneous to the joint replacement ( Fig. 18.6 ). Asymptomatic subtalar joint arthritis does not require treatment, and it is recommended that one waits to determine the effect of the ankle replacement on the subtalar joint and not to routinely perform an arthrodesis regardless of how the joint may appear radiographically ( Fig. 18.7 ).










Figure 18.6


Peritalar arthritis is not a contraindication to performing ankle replacement. There have been no studies that indicate a quicker or higher rate of failure following hindfoot arthrodesis performed either before or simultaneous with the joint replacement. (A–D) This patient presented with painful ankle and hindfoot pain, with range of motion in the ankle well maintained. A subtalar and talonavicular arthrodesis was performed simultaneously with the replacement and the follow-up at 4 years noted here.











Figure 18.7


Asymptomatic subtalar joint arthritis does not require treatment, and it is recommended that one waits to determine the effect of the ankle replacement on the subtalar joint and not to routinely perform an arthrodesis regardless of how the joint may appear radiographically. (A and B) The preoperative x-rays of ankle arthritis associated with asymptomatic subtalar arthritis. (C–E) This was treated with replacement, and the patient remains asymptomatic in the subtalar joint 6 years later.


The sagittal plane alignment of the ankle is important, particularly with respect to anterior translation of the talus under the tibia. Invariably this deformity occurs following erosive arthritis combined with an equinus contracture, which leads to anterior erosion of the tibia and anterior subluxation of the talus. Another cause of this anterior subluxation is following an aggressive cheilectomy of the ankle where the talus subluxates anteriorly. Anterior subluxation of the talus is not a contraindication to joint replacement ( Fig. 18.8 ). One has to be careful with the intraoperative technique, since some of the alignment guides and cutting jigs are created specifically to increase the lateral tibial alignment to 83 degrees. This is incorrect, and in these deformities in particular, one must cut the tibia so as to “close” the cut to 90 degrees (or as close as possible) if necessary. The worst mistake would be to cut the distal tibia in slight dorsiflexion (i.e., “open”), which simply increases the potential for the talus to subluxate again anteriorly postoperatively. Following good joint debridement, in particular the posterior capsule, the talus should be mobile and once the trial is inserted, note that in dorsiflexion, the talus is well centered under the tibia. The talus must not be inserted anterior to the long axis of the tibia. If there is any persistent tendency to subluxate following adequate circumferential release, then one can add a static stabilizer to the joint by pulling the talus back posteriorly using a split peroneus brevis tendon. The tendon is split and then passed through the syndesmosis posteriorly and sutured under tension behind the fibula, thereby preventing anterior subluxation ( Fig. 18.9 )














Figure 18.8


Anterior subluxation of the talus was present in this case, partly as a result of the posttraumatic distal recurvatum deformity of the tibia, and partly from fixed equinus. (A–D) It is important to obtain flexion and extension x-rays to determine the potential for coverage of the talus, which was present here. The center of the talus corresponds to the tip of the lateral process of the talus, and this is 2 cm anteriorly translated from the center axis of the tibia. (E and F) Note that the talar component has been centered correctly, and the tibial cut was made more “closed” than normally done. With extension of the ankle, the talus is perfectly centered.











Figure 18.9


This case of anterior subluxation of the talus demonstrates the alignment of the center of the talus and the center of the tibia in forward flexion (ankle extension). The final alignment was good with the exception of the tibial component, which is slightly anterior to the axis of the tibia. (A–E) Figure (E) demonstrates the measurement of the anterior subluxation with a line through the lateral process of the talus and one through the longitudinal axis of the tibia.


Alignment


Tibia varus or valgus deformity should be addressed before ankle replacement, particularly if the knee is affected, in which case the knee must be first corrected ( Fig. 18.10 ). It sounds simplistic, but how often do you as the surgeon ask the patient to remove their pants to adequately visualize the alignment of the leg? It is an error to examine a patient without full visualization of the leg.




Figure 18.10


Joint replacement should be staged if there is tibia vara. The tibial osteotomy can, however, be performed simultaneously with the ankle replacement.


Bone quality is an important consideration, and if severe osteopenia is present, the likelihood of subsidence of the prosthesis is increased. The risk increases if AVN is present. The talar component is more likely to subside than the tibial component, particularly if osteopenia or AVN is present. Preoperative instability of the ankle is very important to ascertain, and treatment should be planned accordingly. Certain deformities seem trivial but should be approached with caution. An unstable ankle is typically thought to be associated with a lack of lateral ligamentous support. Such instability is problematic only if not identified intraoperatively, because a ligament reconstruction is always possible to restore stability. It is rarely necessary to reconstruct the deltoid ligament preoperatively.


Combined surgeries are commonly performed for associated deformity and arthritis. We recommend simultaneous hindfoot arthrodesis but only when there is minimal deformity. If deformity is present, it is more difficult to correct the ankle and the foot simultaneously ( Fig. 18.11 ). The talonavicular arthrodesis is straightforward, because the incision is simply extended slightly distally. A lateral incision can be used for an isolated subtalar arthrodesis or a subtalar and calcaneocuboid arthrodesis ( Fig. 18.12 ). The fixation of these joints can be difficult, but correctly positioned screws or plates are used without interfering with the prosthesis. This consideration is of particular importance in patients with rheumatoid arthritis. Repeated bouts of immobilization lead to increased osteopenia with the potential for implant subsidence or fracture. Simultaneous joint replacement–arthrodesis has its advantages. If hardware is present in the tibia or talus, it obviously has to be removed if it interferes with correct positioning of either the tibial or the talar component. Of note, however, removal of hardware may create a stress riser, particularly in the medial malleolus. Screws that strip on attempted removal constitute more of a problem: additional bone has to be removed to core out the screw with a screw removal device. Screws in the medial malleolus may interfere with insertion of the tibial component, and they should not be removed intraoperatively, regardless of the type of prosthesis, unless the malleolus is reinforced with temporary Kirschner wires.



Techniques, Tips, and Pitfalls





  • After the skin incision, the extensor retinaculum is carefully incised to create two flaps, which are not retracted during dissection until the tibial periosteum is reflected. The central aspect of the incision directly over the ankle is at the most risk for subsequent wound dehiscence, and very gentle retraction is necessary. Use finger retraction, and do not pull on the skin with an instrument. Simultaneous retraction of both sides of the incision should be avoided. Use of deep Gelpi retractors facilitate retraction of the deep tissue minimizing pressure on the skin if both sides of the incision require retraction. These should be released as soon as they are not required for visualization.



  • A synovectomy and debridement of the osteophytes will facilitate improved exposure, including a sense of the position and plane of the ankle joint. Performing an extensive ostectomy or cheilectomy of the anterior distal tibia to improve visualization of the joints is always helpful, regardless of the implant used. A problem may arise with exposure of the distal fibula at the talofibular articulation. This is not easy to visualize and is best done slowly, with movement of the ankle until the joint is easily visible.



  • For all implant systems, it is necessary to be able to change the size of the prosthesis at the final stage of the surgery. This is particularly the case if the range of motion is compromised, and under these circumstances, we downsize the prosthesis in the hope of improving the range of motion. Select the smaller prosthesis only if it adequately covers the cortical rims of talus and distal tibia and provides sufficient clearance.



  • When the tibial cut is made in cases of posttraumatic arthritis, removal of the posterior lip of the tibia is difficult. The tibia can be prominent posteroinferiorly, and the flexor hallucis and peroneal tendons may be scarred down to the underlying bone. Do not rip out the bone with a rongeur, but slowly remove the hypertrophic osteophytes with a pituitary rongeur. When making the tibial bone cut, pay attention to the posterior soft tissues, in particular the posterior tibial tendon and the flexor hallucis longus tendon, with the cut on the posterior aspect of the tibia.



  • A fracture of either malleolus must be recognized and fixed intraoperatively. Fracture of the medial malleolus creates more of a problem and is usually caused by a combination of osteopenia, previous stress on the medial malleolus (such as with a varus deformity), difficulty with sizing or positioning of the tibial component, or inadvertent manipulation of the ankle. If a fracture does occur intraoperatively, it should always be secured with internal fixation, because the malleoli are required for the stability of the prosthesis. Fracture of the medial malleolus creates more of a problem and is usually caused by carelessness with sizing or positioning of the tibial component or inadvertent manipulation of the ankle. Perhaps the most common error causing fracture of the medial malleolus is making an oblique (not vertical) cut of the medial malleolus, when the swing of the blade cuts deeper into the malleolus posteriorly.



  • If the prosthesis has been well sized and there is apparent stiffness, one has two choices. To recut the tibia or to insert a smaller poly spacer. If the prosthesis has been correctly sized and matches the tibia and the talus, then it is preferable to recut the bone, which can be removed from either the talus or the tibia, depending on the available bone. One should avoid removing more bone from the talus, and if it seems like this is the ideal location to remove more bone, to ensure that the posterior subtalar joint is not compromised, any further cuts on the talus must therefore be made with the ankle fully dorsiflexed.



  • Do not overstuff the joint, which will lead to stiffness, pain, and ultimate joint failure. A gastrocnemius recession or Achilles tendon is often necessary to obtain 10 degrees of dorsiflexion without much stress on the foot with the knee extended. If good range of motion appears present but the joint still has a feel of stiffness, then one can shave 2 mm off the tibial cut and decrease the tension on the joint thereby gaining motion.



  • Once the trial components are inserted, it should just be possible to separate the components by a few millimeters from each other with gentle pulling on the ankle. This ensures the correct tension.



  • The retinaculum over the anterior tibial tendon must be carefully repaired if the tendon is exposed. In the event of a wound dehiscence, provided the tendon is not exposed, the management of the wound is not difficult. The anterior incision must protect the sheath of the anterior tibial tendon and should be made slightly lateral to the tendon. If the retinaculum tears, inserting a suture in it early is preferable to repairing the retinaculum after surgery to maintain the tendon in the sheath. The retinaculum must be closed to prevent bowstringing of the tendon and to minimize the potential for disaster if a wound dehiscence occurs postoperatively.



  • Initial splinting of the ankle joint in maximum dorsiflexion is essential to avoid creating an equinus contracture, because the dorsiflexion is difficult to regain later on.



  • Early initiation of range-of-motion exercises is recommended. A fracture boot locked in extension should be used to immobilize the joint during the periods when exercise is not performed. Control of postoperative swelling minimizes patient discomfort and increases ability to perform the necessary exercises. Early weight bearing is permitted with the Salto prosthesis, and once the incisions are fully healed, the patient is permitted to begin swimming and walking in a pool. Progressive resistance exercises are gradually added to the postoperative rehabilitation regimen.



  • Patient weight should be taken into consideration by the expected size of implant to be used and the body mass index. A large muscular man with a large joint who requires a large implant would be expected to have fewer complications with subsidence and wear than those typical for an obese patient of the same weight with a small ankle requiring a smaller implant. In general, the exact-size prosthesis should be inserted; in some instances, however, it may be best to “err” in one direction or another with regard to size. For example, in patients with severe ankle ankylosis secondary to trauma, an acceptable range of motion may not be attainable; this limitation can be minimized to some extent by downsizing the prosthesis.

















Figure 18.11


This patient presented with severe hindfoot valgus associated with arthritis and partial avascular necrosis (AVN) of the talus. Although a hindfoot arthrodesis will not increase vascularization of the talus, it was thought that a prudent approach would be to perform the triple arthrodesis and, 6 months later, the replacement. (A and B) Note the valgus hindfoot deformity, the arthritis, and the talus AVN. (C–G) The replacement was performed 7 months later, now with corrected deformity and less concern for subsidence of the talar component. One can appreciate the improved alignment and the range of motion gained from the total ankle replacement.



Figure 18.12


A subtalar arthrodesis was performed simultaneously with the joint replacement through a separate lateral incision. It is important to maintain as large a skin bridge as possible.


The Salto Talaris Prosthesis Technique


Unlike with the other implants discussed here, with the Salto Talaris ankle replacement (Integra Life Sciences, Plainsboro, United States), the anterior tibial cheilectomy must fully expose the tibial articular surface, because the plafond marks the point from which the tibial resection is measured.


The purpose of the locking pins in the tibial alignment guide is to accomplish just that—to hold the guide in a firm position relative to the ankle. The medial pin may not align well with the tibia and can actually be situated anywhere on the tibia. If the guide is shifted, then the distal cutting block is adjusted eventually. If the tibia has a difficult anterior configuration, the pin can be inserted laterally.


The tibial alignment guide must not be completely flush on the distal tibia, leaving 2 mm of clearance for translation of the cutting block guide proximally for adjusting the resection level. The guide must, however, be flush with the surface of the plafond, aided by removal of all anterior osteophytes. The tibial alignment guide can be lifted proximally by a few millimeters to bring the tibial cutting block away from 83 degrees. This is important if the cut on the tibia is made less than 83 degrees and the alignment of the tibial cut is now dorsiflexed (“open”). There are situations where the cut must definitely not be open, and one has to deliberately plan for a more perpendicular cut on the tibia when there is anterior erosion of the tibia or when the talus subluxates anteriorly.


The foot must be plantigrade for correct use of the alignment guide. As with other implant systems, soft tissue correction should be done before the bone cuts are made.


The recommended distal tibial resection thickness is at 9 mm on the jig, which does not mean that 9 mm of tibial bone is removed.


Use of an 8-mm resection level is recommended for loose joints in an effort to preserve bone, even though this can be made up with a larger poly-insert thickness.


As with all implants, sizing of the prosthesis is important, although not critical at this stage, because the size of the tibial implant can be changed. The edge of the medial malleolus and the lateral edge of the syndesmosis mark the lines for selection of the implant size.


Use half-pins in the tibial cutting guide to protect the malleoli during the tibial resection.


Anterior translation of the talus will lead to anterior insertion of the talar component, and the foot must be in neutral to allow placement of the talar cutting guide pin in the correct location. If the foot is dorsiflexed, the talar dome resection will be too anterior, and if the foot is plantar flexed, the talar dome resection will be too posterior. This is a malleolus-sparing implant, and the narrow saw blade should be used to cut the talus and protect the malleoli. Verify the position of the talar cutting pins fluoroscopically to ensure that they are correctly oriented.




Overview


Replacement Versus Arthrodesis


Who is the ideal candidate for an ankle replacement? What should the surgeon tell a patient who presents with ankle arthritis, and how should decision making proceed in this setting? Selection of the treatment approach should not be the surgeon’s decision alone. For an ideal patient with good alignment, good bone support, and reasonable range of motion, with no contraindication to joint replacement, what is the best surgical advice? There is a learning curve to ankle replacement (total ankle replacement; TAR), which is not the case with ankle arthrodesis. This learning curve has been well established in the literature, and noted and documented for different types of prostheses. It is not possible for us to quantify how many replacements a surgeon should perform before becoming comfortable with the procedure, but what is clear is that there should be a minimum number of TAR performed by an individual surgeon annually to maintain a level of expertise and ability to deal with all types of pre-, intra-, and postoperative problems. While we cannot state with certainty what this number is, from discussions with many surgeons in the field on this topic, it appears that a minimum of 15 TAR should be performed per year to maintain a level of expertise that provides a realistic level of competence.


What are the advantages of ankle replacement over arthrodesis? Is the functional improvement with ankle replacement so much greater than arthrodesis that it warrants performing the procedure despite its much higher complication rate? Many patients recognize the potential problems with ankle arthrodesis, the inherent stiffness, the limitation to certain activities, and in particular the likelihood of adjacent joint arthritis developing in the future ( Fig. 18.1 ). Within this group of patients, however, some prefer not to deal with potential for failure of an ankle replacement and want more predictability in the outcome, and therefore select the arthrodesis. We outline all of the potential advantages and disadvantages, as well as the possibility of complications for each procedure; selection of the most appropriate procedure then becomes a joint decision that the patient and we make together. There are certain patients, however, who should preferably not undergo an ankle replacement even if many of the other prerequisites are met, including those with severe osteopenia, severe avascular necrosis (AVN), those with neuropathy, the patient who is young and very active, and those who have unrealistic expectations of the outcome of the procedure. On the other hand, there are certain indications for replacement that one can follow and, while not absolute, are very helpful. These include the patient with bilateral ankle arthritis, the presence of a stiff subtalar joint, good range of motion in the ankle joint, good bone quality, normal alignment of the leg, and those individuals who are engaged in daily activities and who feel that they need more flexibility of the ankle, for example for dancing and yoga.


Apr 18, 2019 | Posted by in RHEUMATOLOGY | Comments Off on Total Ankle Replacement
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