Given the challenges of total ankle replacement, these authors provide a historical overview of one of the early implants, review common complications and offer salient insights on revisional treatment.
It is generally accepted that the early history of total ankle replacement arthroplasty consisted of uninterrupted failure and accordingly was rendered nearly extinct.1-7 Dissatisfaction with ankle joint arthrodesis, the success of total hip and knee implant arthroplasties, and the efforts of surgeons and industry to address the problems associated with prior implant designs have resulted in renewed interest in total ankle replacement.8-12
One total ankle replacement available for use in the U.S. is the Agility® Total Ankle Replacement System (DePuy Orthopaedics). Frank G. Alvine, MD, who invented the device, states that the prosthesis was designed around three specific areas of study: (1) CAD-CAM computer analysis of 100 normal ankle radiographs; (2) modes of failure (specifically subsidence, impingement and malalignment) of previous generations of total ankle replacements; and (3) surgical approach including accuracy of insertion and instrumentation including an external fixation device to tension the ligaments.13,14
The design process started in 1978 and the first patient received the implant in 1985. It was subsequently marketed in 1992 as the “DePuy Alvine Total Ankle Prosthesis.”15 Between 1985 and 2007, the implant went through a total of four generations and seven phases of implant improvement.13,14,16 Of note, the ankle implant is FDA approved only for use with polymethylmethacrylate (PMMA) cement fixation as demonstrated in the technique guides.17,18
Between 1985 and 1998, there were several early phases of improvement with the implant. These improvements included thickening of the tibial titanium component; augmenting the posterior dimensions of the tibial component; changing the metallurgy of the talus from titanium to cobalt-chrome; increasing the sizes from three to six; developing a rectangular “revision” talar component; and adding revision ultra-high molecular weight polyethylene (UHMWPE) with an additional 2 mm thickness as well as a half-column design for the 0-mm UHMWPE insert to make revision insertion of the bottom-loaded insert easier.14 These changes were based on the continued effort of the inventor to refine the implant and improve his patient’s outcomes as well as the release of the implant to a select group of orthopaedic surgeons across the U.S. in 1993 and their ongoing feedback.
Following these changes, the implant became widely available to surgeons who completed a company-sponsored surgical skills course at the American Academy of Orthopaedic Surgeons Learning Center in Rosemont, Illinois, starting in 1998.16,19 The Agility Total Ankle Replacement System was the only FDA-cleared ankle replacement readily available in the U.S. until 2007. As a result, the Agility Total Ankle Replacement System was the most widely implanted ankle replacement in the U.S. for over a decade. Complications began to surface that predominantly involved three modes of failure: (1) syndesmosis nonunion and subsequent tibial component malalignment or loosening; (2) talar component subsidence; and (3) aseptic osteolysis.14,16,19-27 The last two modes of failure usually coincide.
As a result, the next changes to the Agility Total Ankle Replacement System occurred in 2002 with alterations to the talar component, making it 18 percent wider, shortening the length of the fin and adding the ability to create a custom-stemmed talar component to replace lost height due to subsidence and cystic changes, and perform concomitant arthrodesis of the subtalar joint.9,14 This was followed in 2003 with the ability to create a custom-stemmed total talar replacement and in 2004 with the use of a plate and screw construct to enhance syndesmosis union.14,28,29 Unfortunately, as of December 8, 2011, any Agility Total Ankle Replacement System custom-stemmed talar component is no longer available for clinical use due to U.S. FDA regulation and the availability of this in the future remains uncertain.30
The final changes occurred in 2007 after surgeons and engineers developed the Agility® LP Total Ankle System, which included three major modifications. The first modification was the development of a broad-based “winged” and 2 mm thicker talar component to reduce the incidence of subsidence with primary implantation, and allow for the ability to revise previously inserted talar components and a corresponding shortening or “lowering the profile” of the tibial component side walls by 2 mm to accommodate the talar wings.
A second modification was the ability to mismatch component sizes by upsizing one talar component relative to the tibial component. This allows for more precise insertion and revision capabilities since the tibial component from an earlier generation can remain in situ and one can insert a bottom-loaded full column +2 mm UHMWPE into an LP talar component. The third modification was developing a front-loaded polyethylene locking mechanism with 0 mm (i.e., neutral) and +1 mm thickness, making subsequent replacement easier.14,19,31,32
Unfortunately, a recently completed but not yet published U.S. National Institutes of Health two-year outcome study of 50 non-cemented Agility LP Total Ankle Systems revealed complications similar to the older Agility designs.33 Additionally, the Agility LP Tibial Tray is no longer being manufactured. This foretells the end of the LP version as a primary total ankle replacement and complicates revision options.
There has been much attention focused on intraoperative complications (i.e., malleolar fracture, nerve or tendon injury) and incision healing-related problems (i.e., wound coverage, infection). However, the intermediate and long-term complications (i.e., aseptic osteolysis, subsidence, component loosening and progressive malalignment) require careful consideration as the secondary procedure options for revision remain limited and the potential need to revise previously revised implants exists.2,3,9-13,16,19,20,34-61
Although not definitive, researchers have recently determined a 10.2 percent (240 revisions/2,353 primary implants) incidence of revision, defined as component replacement, ankle or tibio-talo-calcaneal arthrodesis, or below-knee amputation.61,62 In a detailed systematic review, 78.6 percent of the revisions consisted of implant component replacement followed by arthrodesis (18.7 percent of revisions) and below-knee amputation (4.7 percent of revisions).63 Unfortunately, the outcomes of primary implantation of the most recent generation, the Agility LP Total Ankle Replacement System, and the ability to perform successful revision of a failed earlier-generation Agility Total Ankle Replacement System in general remain unanswered.
Nonunion of the distal tibiofibular syndesmosis develops secondary to premature weightbearing, inadequate preparation of the syndesmosis for arthrodesis, metal fixation failure and the presence of unrecognized post-traumatic distal-lateral tibial necrosis. The surgeon should resect the nonunion until only healthy, viable bone remains. This frequently results in significant bone loss. While most publications recommend the use of impaction cancellous bone grafting supplemented with a fibular side plate and multiple fibula-pro-tibia compression screw stabilization, this approach mandates protracted periods of non-weightbearing, and union is often incomplete, making further revision likely.9,29,42,50,51,64
The subsequent revision is even more complex due to the multiple osseous defects in the fibula from prior hardware insertion and removal, and the need for resection of additional bone about the syndesmosis nonunion site resulting in significant osseous defects. Instead, we recommend the implantation of multiple 0.062-inch Kirschner wires bent and twisted into various geometric shapes (i.e., coils, crosses, pyramids, etc.) within the osseous defect followed by the insertion of polymethylmethacrylate cement, adhering to the principles of cemented total knee arthroplasty (see photos D-F on page 53).65,66
The development of aseptic osteolysis following total ankle replacement is the major cause of failure. It increases with time and results in loss of fixation of the prosthesis. This process involves a macrophage mediated osteolytic destruction of periprosthetic bone secondary to phagocytosable UHMWPE wear debris usually as a result of component malposition.60,67-79 Specific to the Agility Total Ankle Replacement Systems, aseptic osteolysis about the tibial tray may or may not involve subsidence and/or component loosening. Aseptic osteolysis involving the talar component nearly universally involves varying degrees of subsidence and component loosening. The resultant bone loss can be quite extensive.37,80
When it comes to aseptic osteolysis about the tibial tray without subsidence, one should resect all cyst contents and proceed to implant multiple 0.062-inch Kirschner wires bent and twisted into geometric shapes within the osseous defect with subsequent insertion of polymethylmethacrylate cement (see photos F-H on page 54). Aseptic osteolysis about the tibial tray with subsidence remains a challenge. The only options are explantation and conversion to the INBONE® Total Ankle Replacement Systems (Wright Medical Technology) (see photos on page 56) or when more bone remains, coversion to the Salto Talaris™ Total Ankle Prosthesis (Tornier) or tibio-talo-calcaneal arthrodesis with bulk femoral head allograft and retrograde compression intramedullary nail fixation.45,48,84-86
Once the Salto Talaris® XT Revision Total Ankle Prosthesis (Tornier) is available for use in the U.S., the options for revision total ankle replacement will become more plentiful as this system includes stemmed tibia and talar components, augmented talar components, and a large array of thick UHMWPE inserts.
Aseptic osteolysis involving the talar component occurs in three stages of severity based on the degree of collapse into the talar body (see above radiographs) and seems to be correlated with the degree of osseous ongrowth to the porous coated undersurface of the talar component and keel/peg design characteristics.87-89 The options for revision of the talar component depends on whether the failed system was an Agility or Agility LP Total Ankle Replacement System. The original, flanged and posterior augmented talar components are no longer available for use.30
We should note that the LP talar component has the same height as the same size original, flanged or posterior augmented talar components. However, the articulating top surface of the LP talar component is much broader than these other designs and results in comparably less frontal and transverse plane motion. Additionally, depending on the size you use, the revision talar component adds between 1.5 mm and 2.8 mm of height.
Finally, several UHMWPE insert options exist depending on the specific version of the Agility or Agility LP Total Ankle Replacement System undergoing revision. Specifically, if the failed system is an Agility Total Ankle Replacement System, then the revision options include: (1) a same size revision talar component with a bottom-loaded full or half-column 0 mm UHMWPE insert; (2) a same size revision talar component with a bottomloaded full column +2 mm UHMWPE insert; or (3) a same size LP talar component with a bottom-loaded full column +2 mm UHMWPE insert.
However, if the failed system is an Agility LP Total Ankle Replacement System, then one may consider the following revision options.
(1) A same size revision talar component with a front-loaded 0 mm UHMWPE insert.
(2) A same size revision talar component with a front-loaded +1 mm UHMWPE insert (see photos on page 53).
(3) A same size LP talar component with a front-loaded 0 mm UHMWPE insert. (Note: this is only possible if one corrects the talar component subsidence back to its original state with the use of polymethylmethacrylate cement augmentation. Otherwise, an unstable joint will result.)
(4) A same size LP talar component with a front-loaded +1 mm UHMWPE insert.
(5) A one size larger revision talar component with a front-loaded mismatch UHMWPE insert (i.e., retained size 4 LP tibial tray with size 5 revision talar component and size 5/4 mismatch UHMWPE insert).
(6) A one size larger LP talar component with a front-loaded mismatch UHMWPE insert. We should note that the mismatch UHMWPE insert does not independently add any additional height.
As with tibial component subsidence, we recommend implanting multiple 0.062-inch Kirschner wires bent and twisted into geometric shapes packed within the osseous defect, and the subsequent insertion of polymethylmethacrylate cement to augment the deficient talar body.65,90 It is important to achieve proper talar height so the medial and lateral ankle ligaments are properly tensioned and the mechanical axis of the ankle joint is restored. Whenever possible, we try to achieve a talar height that allows for use of a 0 mm UHMWPE insert and a non-revision talar component in order to preserve these options for a future revision if necessary.
When it comes to aseptic osteolysis involving both the tibial tray and talar components, surgeons can manage this with either retention of the Agility Total Ankle Replacement System tibial tray and replacement of the talar component and UHMWPE adhering to the aforementioned options, or explantation and conversion to the INBONE Total Ankle Replacement Systems.
The use of an anterior distal tibia plate abutting the superior portion of the tibial tray can be invaluable to support or buttress the tibial tray realignment, and one can also employ this plate as a fixation point for a modified Evans peroneal tendon lateral ankle stabilization.31,91 Finally, it is frequently necessary to perform soft-tissue balancing most commonly with release of the deltoid ligament complex and/or a posterior tibial tendon recession and lateral ankle stabilization with a modified Evans peroneus brevis tendon transfer secured to the distal tibia or fibula.40,41,92,93
In regard to explantation of the failed Agility total ankle replacement and implantation of a permanent polymethylmethacrylate cement spacer, conversion to an extended tibio-talo-calcaneal arthrodesis with bulk femoral head allograft or a below-knee amputation, surgeons should reserve these options for non-reconstructable talar body destruction, non-reconstructable soft tissue defects, unremitting pain with joint stiffness or uncontrollable infection.84-86,93 Arthrodesis or below-knee amputation are also indicated in situations in which the patient does not desire or is medically unable to undergo revision surgery.
Failure of the Agility total ankle replacement system leading to revision involves two main etiologies: (1) distal tibio-fibular syndesmosis nonunion and (2) aseptic osteolysis of the tibial and/or talar components with or without secondary component subsidence. Depending on the alignment and integration of the components and size of the osseous defect, multiple revision possibilities exist such that surgeons can revise approximately 80 percent of the failed systems. The revision possibilities include reinforcement of the osseous defects utilizing polymethylmethacrylate cement with or without geometric metal augmentation; use of revision or LP talar components and UHMWPE exchange; or conversion to the INBONE or Salto Talaris Total Ankle Replacement Systems.
Although they are no longer available for use in the U.S., custom stemmed tibial and/or talar components represented viable options and should also be relevant in the future once the FDA loosens the current restrictions and the Salto Talaris XT Revision Total Ankle Prosthesis (Tornier) is cleared for use. Surgeons should reserve arthrodesis or below-knee amputation for select non-reconstructable cases or situations in which the patient does not desire or is medically unable to undergo revision surgery.
Dr. Roukis is an attending foot and ankle surgeon within the Department of Orthopaedics, Podiatry, and Sports Medicine with the Gundersen Health System in La Crosse, Wisconsin. He is a Fellow and President-Elect of the American College of Foot and Ankle Surgeons.
Dr. Prissel is a third-year resident with the Gundersen Medical Foundation in La Crosse, Wisconsin.
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