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Varus and valgus ankle deformities were once considered contraindications for TAA, and were primarily treated by tibiotalar fusions. As the total ankle implant generations matured in conjunction with evolving surgeon techniques the indications for total ankle arthroplasty grew. Currently, ankle deformities may receive arthroplasty if the deformity is corrected either at the time of implantation or beforehand. There exists a lack of consensus in the literature regarding the most appropriate timeframe for these procedures to be performed, and oftentimes these protocols are unique to each individual surgeon. In this text the authors present a protocol that has been developed and employed to overwhelmingly positive results. This was developed with the goal of returning to early ambulation and reducing the amount of surgical trauma of any one given procedure. These tenants allow for the optimization of the arthroplasty procedure's function as well as respecting the healing timeframe necessary in reconstructive surgery. It is the author's hope that this protocol may serve as a steppingstone for other surgeons to develop their criteria and timeframe to suit their comfort level.
The original total ankle arthroplasty system consisted of a long tibial stem with a polyethylene talar component which necessitated a fusion of the subtalar joint
. The surgical technique was modeled after hip implants and would soon prove to poorly translate to total ankle implants. The official first-generation Total Ankle replacements were the first to respect the native anatomy of the tibiotalar joint. This generation of implants consisted of a two-component design varying from “constrained” to “constrained” depending on the polyethylene spacer without a separate independent bearing
. Unfortunately, this generation of TAR's were plagued with high failure rates even in short to mid-term results and were withdrawn from the market based on high rates of subsidence, continued pain and progressive deformity.
Despite these early fallbacks, innovation continued in the field and resulted in the next generation of implant design. These employed the use of metallic tibial and talar components with an ultra-high molecular weight polyethylene meniscus. These generations were then subcategorized based on the number of components and device type. The two component systems are fixed bearing with the polyethylene spacer incorporated into the tibial component of the implant, while the three-component systems are mobile bearing due to their separate polyethylene spacer.
With the adoption of the second and third generations came a newfound focus on reduction of bone resection and consequent preservation of bone stock. The combination of newer implant configuration, surgeon education, and surgical technique driven by evidence resulted in a dramatic increase in survivability of Total Ankle Replacements. Complication rates have continued to decrease with this procedure, and for the first-time comparable complication and reoperation rates to ankle arthrodesis have been reported
End-stage ankle osteoarthritis: arthroplasty offers better quality of life than arthrodesis with similar complication and re-operation rates-an updated meta-analysis of comparative studies.
The next stage in innovation that has been recently introduced is patient specific instrumentation (PSI). These systems rely on Computed Tomography (CT) scans to provide a patient specific and engineer provided preoperative plan. This allows for the alignment and sizing of the metallic prosthetic component based on the patient's ankle joint landmarks or adjacent tibiotalar surface anatomy. With this information available in the preoperative phase, the surgeon can modify the plan based on their preferences or any additional cystic changes that may be near the intended TAR components. Upon final approval by the surgeon the manufacturer creates a three-dimensional model of the patient's anatomy.
From these digital models a disposable physical cut guide is fabricated that allows the surgeon to avoid intra-or extramedullary guide set up. This is because the patient specific pinning and cutting guides do not need further referencing. Other potential benefits from this technique allow for less procedural complexity, less radiation, and less surgical time. Non-industry sponsored research has noted low incidence of perfectly aligned PSI cut guides and only 77% accuracy within +/- 5 degrees from an axial rotational alignment.
Does patient-specific instrumentation have a higher rate of early osteolysis than standard referencing techniques in total ankle arthroplasty? A radiographic analysis.
Intraoperative assessment of the axial rotational positioning of a modern ankle arthroplasty tibial component using preoperative patient-specific instrumentation guidance.
Intraoperative assessment of the axial rotational positioning of a modern ankle arthroplasty tibial component using preoperative patient-specific instrumentation guidance.
. To date, comparison studies note that the PSI systems can get similar implant position and clinical outcomes to standard instrumentation, but there is not strong enough evidence to date to definitively evaluate PSI. It should also be noted that PSI has largely fallen out of favor in hip, knee and shoulder arthroplasty given a reduction in accuracy
Thienpont E, Schwab PE, Fennema P. A systematic review and meta-anlalysis of patient-specific instrumentation for improving alignment of the components in total knee replacement. Bone Joint J 96-B:1052-1061; https://doi.org/10.1302/0301-620X.96B8.33747
. These are factors that should be considered by the surgeon given the increased costs and healthcare resources associated with PSI.
Patient Selection
The American Academy of Orthopaedic Surgeons have noted up to 14 factors that one should consider to optimize outcomes when considering surgical treatment of ankle arthritis (AAOS). These factors include device type, patient age, patient weight, preoperative infection, fracture, surgical side, sex of patient, foot and ankle deformity, comorbidities, previous ankle surgery, presence of hindfoot arthritis, surgeon experience, and hospital surgical volume. Exploring these factors in greater detail is warranted.
Gender
As of the time of this writing, gender has shown no influence on Total ankle survival
. Female gender was found to be a significant risk factor for wound healing problems, but once corrected for confounding variables, it was no longer a predictor for delayed wound healing
Younger age at implantation may affect the survivability of the implant in many ways. Firstly, the TAR will need to function longer due to the higher life expectancy of the patient. Additionally, younger patients tend to be more active, which has been proven to be associated with greater wear of the prosthesis and polyethylene component. However, in a comparison study with identicalimplants patients < 50 years of age had a survival of 75% at 6.8 years, and patients > 50 had a survival of 81% at 6 years. There was no statistically significant difference between the two groups
Even though strong emphasis has been placed on the effect of activity level on the survivability of the implant research into this relationship is seldomly performed. At the moment, there is no correlation between increased activity level and adverse effects with the Salto-Talaris and Hintermann Prostheses
. Despite the relatively low amount of research into this specific variable, guidelines have been developed that may be useful for patient discussion. These include continuation of aerobic or low impact sports and activities. Boot immobilized sports may be acceptable as long as the patient has prior experience with them. High impact, cutting, and jumping sports and activities are discouraged
Obesity has long been considered a relative contraindication for TAR. In the short-term postoperative phase, there are no statistically significant differences noted between complication rates and survivability amongst obese and non-obese TAR patients.
. Currently, most studies find no correlation between BMI and results of TAR.
Smoking
Smoking, as with many surgical interventions, has been a relative contraindication for TAR. However, there has only been one study that has investigated the relationship between smoking and TAR. In this retrospective review of 642 patients, there was a statistically significant increase in wound breakdown amongst the smokers versus nonsmokers
. Further research has been performed with an emphasis on less than 12 pack year smokers which did not see a significant change in complication rates in smokers.
Comorbidities
To date there is no literature that solidly supports the notion that diabetes should be considered a contraindication for TAR, with the obvious exception of uncontrolled diabetes. No definitive statement could be made regarding neuropathy and vascular insufficiency due to a lack of literature given their label as absolute contraindications.
Deformity
The importance of deformity correction either before or during TAR has been recognized for quite some time
. Since the adoption of recent guidelines the scientific evidence has strongly supported the notion that deformity is no longer a contraindication for TAR. Under the assumption that stepwise realignment procedures are followed accordingly.
Pre-operative planning
The pre-operative planning process is an important part of the long-term success and survivability of the total ankle implant. This includes a full set of plain film radiographs of the foot and ankle, hindfoot alignment, stress dorsiflexion and stress plantarflexion. When performed correctly, these X-rays help provide the foundation to determine the treatment of choice (between fusion and replacement) and the true origin of the deformity. Along with a proper physical examination this can help determine if the deformity is secondary to soft tissue or osseous rigidity as well as the appropriate level. CT scans are also vitally important in the preoperative stage to assess for cyst formation and bony abnormalities at and around the tibiotalar joint. Weightbearing CT scans are applicable in this setting to determine ankle deformity in the stance of gait. Recent literature has explored the additional benefits of CT scans in the form of Hounsfield Unit (HU) measurements with their relation to bone mineral density. Studies specific in focus to the foot and ankle have determined bone attenuation of the distal tibia and talus on CT reveal significant correlation with BMD on all parts of a DEXA scan and HU. Threshold HU values in the distal tibia and talus were defined for osteoporosis with the distal tibia at 122.5 and talus at 311.4
. Additionally, HU measurements have been related to risk of nonunion in ankle fractures and have also been used to define patients appropriate for prophylactic medial malleolar screw fixation during TAR procedures
Predicting nonunions in ankle fractures using quantitative tibial hounsfield samples from preoperative computed tomography: a multicenter matched case control study.
The long-term survivability of the total ankle implant can be maximized by uniform distribution of ground reactive forces along the implant components and spacer. Neutralizing the deforming forces that may be experienced along the implant will permit a more even wear pattern. The role of physical examination, plain film radiographs, and advanced imaging is crucial to determining the center of rotation of angulation (CORA) which in turn will dictate surgical correction. When the CORA is proximal to the ankle joint a combination of supramalleolar osteotomies, medial malleolus lengthening/shortening, and/or lateral malleolus lengthening/shortening can be performed. A CORA that originates in the foot can be corrected via a combination of hindfoot or midfoot osteotomies and/or fusions with or without appropriate soft tissue correction.
The determination to perform adjunctive deformity correction with a total ankle replacement versus staging the deformity correction prior to implant placement can be chosen based on the amount of additional non-weightbearing time each procedure is responsible for. To assist in optimizing range of motion (ROM) of the implant it is crucial to start physical therapy and weightbearing as soon as possible, which is oftentimes determined by the state of the incision when the procedure is solely a TAR. The longer that time is spent non-weightbearing and the joint immobilized without ROM in TAR the more likely it is that the capsule will form adherences and the surrounding soft tissues fibrose in a contracted position. Deformity correction through osseous procedures may add additional nonweightbearing time to promote proper bone healing. If these additional adjunctive procedures are required to correct deformity, consideration for staging may be necessary. Another, often overlooked, consideration surgeons should be cognizant of is the healing demand placed on the patient. Depending on the level of reconstruction necessary, a brief intermission in surgery may allow the body to more efficiently heal through a staged approach.
All these determinations should be addressed during the pre-operative period in order to optimize patient experience, outcomes, and total ankle survivability.
Staging Considerations
As is true of all surgical techniques, a practitioner should base their plans on their own comfort level and training. The algorithms and recommendations in this text are based off the authors’ experience; however, it should also be noted that no single algorithm can truly capture every unique patient.
In general, staging deformity correction in Total Ankle Replacements is dictated by the effects that a procedure will have on the weightbearing protocol. Overall patient outcomes in total joint surgeries are dictated in large part by return to ambulation. Expeditious return to ambulation and physical therapy will decrease the adherences that develop over a prolonged period of sedentation. Time to ambulation for TAA's performed on their own are oftentimes determined by the state of the incision. This usually allows for protected weightbearing to initiate from week 2-3 in the postoperative stage. Additional procedures may increase the non-weightbearing timeline; however, it is important to try and limit this phase to no longer than 4 weeks. Hindfoot fusions, multiple midfoot fusions, and supra-malleolar osteotomies traditionally necessitate at least 6 weeks of non-weightbearing. The procedures listed in this category may then be ill suited to be performed simultaneously with a total ankle replacement. And thus are most appropriately staged at least 4-6 weeks before the TAA. Hindfoot and/or midfoot osteotomies, and soft tissue corrections may realistically transition to protected weight bearing 4 weeks post operatively and may be appropriate to be completed in a single stage with the TAA (Figure 1, Figure 2).
Figure 1Preoperative films for 55 year old female that underwent Total Ankle Arthroplasty with reconstructive surgery to neutralize the ankle joint in a single operation.
Figure 2Postoperative films for 55 year old female that underwent Total Ankle Arthroplasty with reconstructive surgery to neutralize the ankle joint in a single operation.
In the pursuit of achieving ankle joint neutrality, certain patterns arise based on the type and severity of deformity. This allows for a protocol such as the one shown in Graph 1 to be developed. Varus type deformities of the tibiotalar joint are more amenable to correction through a combination of osteotomies and soft tissue procedures regardless of severity. Valgus type deformities, however, oftentimes require a combination of hindfoot/midfoot fusion and supra-malleolar osteotomies in order to achieve neutrality at the ankle. This may be in part attributed to the rigidity seen in cavovarus feet allotting a greater degree of surgical control when addressing varus deformities. In comparison to the flexibility seen in planovalgus feet that introduces a certain degree of variability requiring more aggressive correction in valgus ankles.
Based on this recognition of deformity patterns it is important to assess the type of deformity as well as the exact location of the CORA. Regardless of the deformity type, corrections requiring a supramalleolar osteotomies necessitate a duration of non-weightbearing that is better suited for a staged approach. Valgus deformities are further subcategorized based on the severity of deformity that is present. The cutoff present in the current protocol is at 10° however the amount of deformity and correction that can be obtained via osteotomies versus fusions should be at the discretion of the surgeon and re-evaluated with each new patient. Typically, tibiotalar joint in valgus deformity responds to a combination of soft tissue correction, midfoot osteotomies and rearfoot osteotomies, which may still allow a TAA patient to initiate protected weightbearing within 4 weeks post-operative. Valgus deformities greater than 10° are much more likely to require a combination of supramalleolar osteotomies, hindfoot and midfoot fusion(s) which will prolong time to weightbearing past an acceptable time frame for a single stage TAA. Ankles in varus are less dictated by the severity of the deformity and are more directed by arthritic changes in major joints of the foot and ankle. Correction of these joints may be via triplanar correction through osteotomies. Varus tibiotalar joints which retain supple joint spaces and motion are, in the opinion of the author's, easily correctable via osteotomies in the hindfoot and midfoot.
The time frame for staging should again be based on the surgeon's training and preference level. When determining the appropriate length of time between surgical procedures it is essential to remember the minimum amount of time for the biological processes to heal a specific surgical procedure. For instance, a bony arthrodesis typically requires 6 weeks to exhibit initial signs of radiological and clinical signs of trabeculation, and this information can be utilized to reduce the sedentary time for a surgical patient when considering staging. Ankle deformity requiring a staged approach can realistically undergo multiple fusion procedures 4 weeks before a TAA procedure, and pending optimal healing conditions, may still be able to ambulate 2 weeks after the final implant placement. This timing is only appropriate for a certain patient population, and a surgeon should exercise appropriate discretion when selecting candidates for this particular protocol.
Case Examples
Single Procedure
Patient is a 55 year old female who sustained a pilon fracture with subsequent ORIF and skin grafting shortly after injury. 5 years later development of pain and arthritis in the tibiotalar joint warranted clinical follow up (Figure 1). On physical examination and radiographic, a progressive mild cavus deformity was noted.
Surgical intervention included Total Ankle replacement with lateralizing calcaneal slide osteotomy, and ATFL repair through synthetic suture anchors and Brostrom-Gould repair (Figure 2). Given that a rectus ankle was achieved through osteotomy and soft tissue correction a decision was made to single-stage this intervention.
Staged
Patient is a 41 year old male with history of ankle fracture with resultant progressive cavovarus deformity leading to arthritis, pain and an antalgic gait (Figure 3). A decision was made to perform a staged correction to achieve foot and ankle neutrality before placement of total ankle replacement. The first procedure consisted of Dwyer type calcaneal osteotomy with supramalleolar osteotomies of medial and lateral malleolus as well as dorsiflexory wedge osteotomy of 1st metatarsal. 5 weeks later patient underwent TAR procedure (Figure 4A and B).
Figure 3Preoperative films for 41 year old male that underwent Total Ankle Arthroplasty 4 weeks after reconstructive surgery to neutralize the ankle joint.
Figure 4Postoperative films for 41 year old male that underwent Total Ankle Arthroplasty 4 weeks after reconstructive surgery to neutralize the ankle joint.
Varus and valgus ankle deformities were once considered contraindications for TAA, and were primarily treated by tibiotalar fusions. As the total ankle implant generations matured in conjunction with evolving surgeon techniques the indications for total ankle arthroplasty grew. Currently, ankle deformities may receive arthroplasty if the deformity is corrected either at the time of implantation or beforehand. There exists a lack of consensus in the literature regarding the most appropriate timeframe for these procedures to be performed, and oftentimes these protocols are unique to each individual surgeon. In this text the authors present a protocol that has been developed and employed to overwhelmingly positive results. This was developed with the goal of returning to early ambulation and reducing the amount of surgical trauma of any one given procedure. These tenants allow for the optimization of the arthroplasty procedure's function as well as respecting the healing timeframe necessary in reconstructive surgery. It is the author's hope that this protocol may serve as a steppingstone for other surgeons to develop their criteria and timeframe to suit their comfort level.
Author Contributions
Keegan Duelfer: Literature Review, case review, derived conclusions, protocol development
Jeffrey McAlister: Surgical intervention, case review and derived conclusions
Declaration of Patient Consent
Patient consented to involvement in study with the understanding that no identifying patient information is included.
End-stage ankle osteoarthritis: arthroplasty offers better quality of life than arthrodesis with similar complication and re-operation rates-an updated meta-analysis of comparative studies.
Does patient-specific instrumentation have a higher rate of early osteolysis than standard referencing techniques in total ankle arthroplasty? A radiographic analysis.
Intraoperative assessment of the axial rotational positioning of a modern ankle arthroplasty tibial component using preoperative patient-specific instrumentation guidance.
Thienpont E, Schwab PE, Fennema P. A systematic review and meta-anlalysis of patient-specific instrumentation for improving alignment of the components in total knee replacement. Bone Joint J 96-B:1052-1061; https://doi.org/10.1302/0301-620X.96B8.33747
Predicting nonunions in ankle fractures using quantitative tibial hounsfield samples from preoperative computed tomography: a multicenter matched case control study.
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