Analysis of retrieved agility total ankle arthroplasty systems

Metal debris release is commonly seen from explanted total ankle replacements

This study aimed to characterise the damage mechanisms present on the metal components used in various contemporary total ankle replacements. Twenty-seven explanted total ankle replacements comprising 8 different designs (3 fixed bearing and 5 mobile bearing) were analysed using various explant analysis techniques. Pitting and scratching were the most commonly observed wear features. Microscopic analysis revealed metallic pitting on 52% of tibial components and 95% of talar components. Pitting was identified on more cobalt-chromium than titanium alloy tibial components (63% versus 0%). Non-contact profilometry confirmed the presence of pitting, with significant (p < 0.05) differences in the measured average surface roughness values of pitted and unpitted areas for tibial and talar components. There was macroscopically visible sliding plane scratching, indicating the presence of hard third body particles, on 78% of talar components. Changes to the non-articulating surfaces coatings in terms of coating loss and/or changes in reflectivity was identified visually on 80% of metal components. Scanning electron microscopy with energy dispersive X-ray spectroscopy identified metallic embedded debris in 19% of polyethylene inserts. This explant study demonstrates the release of metal debris from both the metallic tibial and talar component articulating surfaces and non-articulating surface coatings of various contemporary total ankle replacements. Metal particulate debris release from total ankle replacements may be more common than previously recognised. Metal debris should be considered in further study into the aetiology of failed total ankle arthroplasty.

Periprosthetic ankle infection: eradication rate, complications, and limb salvage. A systematic review

BACKGROUND

This systematic review investigated the outcomes of revision surgery after periprosthetic ankle infection (PAI).

METHODS

According to the PRISMA statement, 9 studies with 131 PAIs surgically treated and analyzed were included. Demographics and surgical techniques with eradication rates and complications were reported.

RESULTS

Methicillin-sensitive Staphylococcus aureus (MSSA) (30.4%) and coagulase-negative Staphylococcus (CNS) (26.5%) were the most common microorganisms. The eradication rate was 91.7% with permanent antibiotic spacers (SPC), 84.4% with 2-stage, 79.4% with arthrodesis (AA), and 58.8% with debridement and implant retention (DAIR). DAIR showed a significantly lower eradication rate than 2-stage (p = 0.016) and SPC (p = 0.043). Amputations occurred in 25% of patients after SPC, 8.8% after AA and 3.9% after DAIR. SPC showed a significantly higher amputation rate than DAIR and 2-stage (p = 0.044, and p = 0.017, respectively).

CONCLUSIONS

SPC and 2-stage revision show the highest eradication rates, but 2-stage has a lower risk of amputation.

Damage patterns in polyethylene fixed bearings of retrieved total ankle replacements

INTRODUCTION

Poor long-term outcomes continue to hinder the universal adoption of total ankle replacements (TAR) for end stage arthritis. In the present study, polyethylene inserts of TARs retrieved at revision surgery were analyzed for burnishing, scratching, mechanical damage, pitting, and embedded particles.

METHODS

Fourteen retrieved polyethylene inserts from a fixed bearing total ankle replacement design currently in clinical use were analyzed. Duration of time in vivo was between 11.5 months and 120.1 months. Three investigators independently graded each articular surface in quadrants for five features of damage: burnishing, scratching, mechanical damage, pitting, and embedded particles.

RESULTS

No correlation was found for burnishing between the anterior and posterior aspects (p = 0.47); however, scratching and pitting were significantly higher on the posterior aspect compared to the anterior aspect (p < 0.03). There was a high correlation between burnishing and in vivo duration of the implant (anterior: R = 0.67, p = 0.01, posterior: R = 0.68, p = 0.01).

CONCLUSION

The higher concentration of posterior damage on these polyethylene inserts suggested that prosthesis-related (design) or surgeon-related (technique) factors might restrict the articulation of the implant. The resulting higher stresses in the posterior articular surfaces may have contributed to the failure of retrieved implants Keywords: Retrieval, Polyethylene Damage, Total Ankle Replacement.

Histological Analysis of a Retrieved Porous Tantalum Total Ankle Replacement: A Case Report

CASE

We present a case report documenting the retrieval and histological analysis of a porous tantalum (P-Ta) total ankle replacement (TAR) from a 50-year-old woman after a below-knee transtibial amputation. This rare opportunity to examine an intact TAR may help to better understand the implant-bone relationship because it would be in situ.

CONCLUSION

In this case study, we demonstrate bone ingrowth to the first layer of the P-Ta and organized trabecular orientation, suggesting that equal bone load was achieved on the base and the rails in both components using a transfibular surgical approach.

Revision of failed total ankle arthroplasty to a hindfoot fusion

Aims

The aim of this study was to present a series of patients with aseptic failure of a total ankle arthroplasty (TAA) who were treated with fusion of the hindfoot using a nail.

Patients and Methods

A total of 23 TAAs, in 22 patients, were revised for aseptic loosening and balloon osteolysis to a hindfoot fusion by a single surgeon (NH) between January 2012 and August 2014. The procedure was carried out without bone graft using the Phoenix, Biomet Hindfoot Arthrodesis Nail. Preoperative investigations included full blood count, CRP and ESR, and radiological investigations including plain radiographs and CT scans. Postoperative plain radiographs were assessed for fusion. When there was any doubt, CT scans were performed.

Results

The mean follow-up was 13.9 months (4.3 to 37.2). Union occurred at the tibiotalar joint in 22 ankles (95.6%) with one partial union. Union occurred at the subtalar joint in 20 ankles (87%) of cases with two nonunions. The nail broke in one patient with a subtalar nonunion and revision was undertaken. The only other noted complication was one patient who suffered a stress fracture at the proximal aspect of the nail, which was satisfactorily treated conservatively.

Conclusion

This study represents the largest group of patients reported to have undergone revision TAA to fusion of the hindfoot with good results Cite this article: Bone Joint J 2018;100-B:475–9.

Revision Total Ankle Arthroplasty

With total ankle arthroplasty, documented complications can be categorized chronologically into intraoperative, postoperative, and late complications. Factors such as patient selection, surgeon experience, implant features, and prosthetic device selection can influence functional outcomes as well as incidence of complications. Even with impeccable surgical technique and optimal patient selection, complications that require revision may still arise and the most common complications with revision solutions are discussed in this article.

Osteolysis in Total Ankle Replacement: How Does It Work?

Aseptic loosening of implants remains the most common reason for revision surgery for hip, knee, or ankle prostheses. Although a great scientific effort has been made to explain the underlying mechanisms it remains poorly understood, complex, and multifactorial. Many factors, including age, body weight, activity lesions, implant design, fixation methods, material proprieties, immunologic responses, and biomechanical adaptations to total ankle replacement all contribute to the development of periprosthetic osteolysis.

Management of Massive Hindfoot Osteolysis Secondary to Failed INBONE I Total Ankle Replacement

This article presents a procedure whereby a failed INBONE I saddle talar component and polyethylene insert associated with massive cystic changes within the talus and calcaneus secondary to aseptic osteolysis was treated with impaction cancellous allograft bone graft impregnated with autogenous proximal tibia bone marrow aspirate and conversion to an INBONE II sulcus talar component and polyethylene insert. Concomitantly, a percutaneous tendo-Achilles lengthening and posterior capsule release was performed to enhance ankle dorsiflexion. The rationale for these procedures, the operative sequence of events, and recovery course are presented in detail. Causes for concern regarding subsequent revision, should this be required, are raised.

Wear characteristics of WSU total ankle replacement devices under shear and torsion loads

BACKGROUND

There are several factors that contribute to the failure of total ankle replacement (TAR). Aseptic loosening is one of the primary mechanisms of failure in TAR. Since a cross-linked ultrahigh molecular weight polyethylene (UHMWPE) is used as liner material, there is a need to quantify and develop methods to estimate the wear rates of the liners. High contact stresses develop during the gait generates wear debris resulting in osteolysis and early loosening of the prostheses.

METHODS

In this paper wear characteristics of Wright State University (WSU) TARs were determined by applying shear and torsion loads. Viscoelastic properties were used to model the liner component. Finite element analysis was conducted to determine the wear rate by deriving Von Mises and contact stresses generated in the liner and wear rate equation was used to predict the wear rate.

RESULTS

Titanium alloy has shown less resistance towards shear forces when compared with other metal alloys. Under torsion, rotation angle plays a significant role in affecting the peak stress values. The maximum average contact stress was 14.46 MPa under torsion load which contributes to a wear rate of 0.67 (mm(3)/year) for one of the mobile bearing models. The maximum average contact stress and wear rate obtained from the analytical study were 10.55 MPa and 0.33 (mm(3)/year), respectively for mobile bearing models. When compared with mobile bearing model, fixed bearing model has shown higher stresses at different degrees of rotation.

CONCLUSION

Both shear and torsion loads cause significantly lower contact stresses and wear when compared to the axial load. Further studies are necessary to accurately determine the wear behavior of fixed bearing TAR models.

Force-controlled dynamic wear testing of total ankle replacements

Currently, our knowledge of wear performance in total ankle replacements is limited. The aim of this study is to develop a scenario for force-controlled testing and wear testing of total ankle replacements. A force-controlled wear test was developed: based on cadaver measurements, the passive stabilization (ligaments and soft tissue) of the ankle joint was characterized and a restraint model for ankle stabilization was developed. Kinematics and kinetics acting at the replaced ankle joint were defined based on literature data and gait analysis. Afterwards, force-controlled wear testing was carried out on a mobile, three-component, total ankle replacement design. Wear was assessed gravimetrically and wear particles were analyzed. Wear testing resulted in a mean wear rate of 18.2±1.4mm(3)/10(6) cycles. Wear particles showed a mean size of 0.23μm with an aspect ratio of 1.61±0.96 and a roundness of 0.62±0.14. Wear testing of total ankle replacement shows that a relevant wear mass is generated with wear particles in a biologically relevant size range. The developed wear test provides a basis for future wear testing of total ankle replacements.

Strategies for Revision Total Ankle Replacement

As the frequency of primary total ankle replacement (TAR) continues to build, revision will become more commonplace. At present there are no “standard principles” associated with revision TAR. What is clear is that the current approaches are technically complex, fraught with complications and no one approach represents the only answer. Exchange of TAR metallic components to the same system standard or dedicated revision components are viable options with limited occurrence of complications. Explantation and conversion to custom-design long stemmed components has limited availability. Explantation and conversion to another TAR system is high-risk and has strong potential for complications. The use of metal reinforced polymethylmethacrylate cement augmentation of failed TAR systems and tibio-talo-calcaneal arthrodesis should be reserved for very select situations where other options are not possible. There is a real need for long-term survivorship following revision TAR and future efforts ought to be directed in this area.

Management of extensive tibial osteolysis with the Agility™ total ankle replacement systems using geometric metal-reinforced polymethylmethacrylate cement augmentation

Although total ankle replacement has endured improvement in implant design since its conception, failure requiring revision remains a known endpoint. We describe a technique for management of extensive tibial osteolysis for failed Agility™ total ankle replacement systems using geometric metal-reinforced polymethylmethacrylate cement augmentation. This technique provides immediate component stability and is a cost-effective alternate to impaction bone grafting. With this technique, the complications we have experienced have been limited to minor delayed incisional healing, and all patients have resumed meaningful weightbearing activities with stable integration of the tibial component.

Failure of the Agility total ankle replacement system and the salvage options

The Agility total ankle replacement system was the most commonly performed implant in the United States for more than 20 years and has undergone four generations and seven phases of improvement. Much attention has been placed on intraoperative complications, such as malleolar fracture; nerve or tendon injury; and incision healing-related problems, such as wound coverage and infection. However, it is the intermediate- and long-term complications (ie, aseptic osteolysis, subsidence, component loosening, and progressive malalignment) that require careful consideration, because the revision options remain limited. This article reviews the history of the Agility total ankle replacement system in detail, to understand the revision possibilities available.

Revision total ankle replacement

This review of the current literature regarding total ankle replacement (TAR) revision surgery focuses on the causes for implant failure, how to deal with the clinical dilemmas of pain and stiffness following TAR, the management of asymptomatic peri-implant cyst formation, and the management of the distal tibia and talus during revision surgery.

Incidence of revision after primary implantation of the Agility™ total ankle replacement system: a systematic review

Revision of failed total ankle replacement remains a challenge with limited information available to guide treatment options. I undertook a systematic review of electronic databases and other relevant sources to identify material relating to the incidence of revision after primary implantation of the Agility™ Total Ankle Replacement System. In an effort to procure the highest quality studies available, studies were eligible for inclusion only if they involved patients undergoing primary Agility™ Total Ankle Replacement; had evaluated patients at a mean follow-up of 12 months or longer; included details of the revision performed; and included revision etiologies of aseptic loosening, ballooning osteolysis, cystic changes, malalignment, or instability. A total of 14 studies involving 2312 ankles, with a weighted mean follow-up of 22.8 months, were included. Of the 2312 ankles, 224 (9.7%) underwent revision, of which 182 (81.3%) underwent implant component replacement, 34 (15.2%) underwent arthrodesis, and 8 (3.6%) underwent below-knee amputation. No significant effect from the surgeon's learning curve on the incidence of revision or the type of revision surgery performed was identified. However, excluding the inventor increased the incidence of revision twofold, from 6.6% to 12.2%, and skewed the type of revision away from arthrodesis and toward implant component replacement or below-knee amputation. Regardless, the incidence of revision after primary implantation of the Agility™ Total Ankle Replacement System was less than historically reported and amenable to implant component revision more than 80% of the time. However, methodologically sound cohort studies are needed that include the outcomes after revision surgery, specifically focusing on what implant component replacement techniques are effective in enhancing survivorship of these revised implants and the role of custom-stemmed talar and tibial components have in revision of the Agility™ Total Ankle Replacement System. A direct comparison of the incidence of revision between the various contemporary total ankle replacement systems in common use is also warranted.

High rate of osteolytic lesions in medium-term followup after the AES total ankle replacement

BACKGROUND

Some previous studies have shown a high percentage of early-onset and rapidly progressing osteolysis associated with total ankle arthroplasty (TAA) by the Ankle Evolutive System (AES). The purpose of our study was to analyze medium-term results at our institution.

MATERIALS AND METHODS

Altogether 38 TAAs using AES prostheses were carried out between 2003 and 2007. Diagnoses were rheumatoid arthritis (71%), post-traumatic and idiopathic osteoarthritis (29%). The mean age was 54 years, followup 28 months. Tibial and talar components had hydroxyapatite coating on metal (Co-Cr) components (HA-coated). Since 2005 the design was changed and components were porous coated with titanium and hydroxyapatite (dual-coated).

RESULTS

Two-year survival was 79% (95% CI: 56 to 98). At followup 34 (89%) primary tibial and talar components were preserved. In 19 (50%) TAAs osteolysis (more than or equal to 2 mm) occurred in the periprosthetic bone area and in nine (24%) comprised large "cyst-like osteolysis''. In HA-coated prostheses radiolucent lines (less than or equal to 2 mm) or osteolysis (more than or equal to 2 mm) were detected in 11 (100%) cases and in dual-coated prostheses in 19 (74%) (p = 0.08). On the other hand there was more large "cyst-like osteolysis'' around the dual-coated prosthesis and lesions were larger (p = 0.017). In rheumatoid arthritis osteolysis was detected in 14 (52%) and large "cyst-like osteolysis'' in seven (26%) prostheses and in the group of traumatic and idiopathic osteoarthritis in six (55%) and two (18%), respectively.

CONCLUSION

This study showed a high frequency of osteolysis in medium-term followup after the AES ankle replacement. The outcome was not sufficiently beneficial and we have discontinued use of this prosthesis.

Misalignment of total ankle components can induce high joint contact pressures

BACKGROUND

A major cause of the limited longevity of total ankle replacements is premature polyethylene component wear, which can be induced by high joint contact pressures. We implemented a computational model to parametrically explore the hypothesis that intercomponent positioning deviating from the manufacturer's recommendations can result in pressure distributions that may predispose to wear of the polyethylene insert. We also investigated the hypothesis that a modern mobile-bearing design may be able to better compensate for imposed misalignments compared with an early two-component design.

METHODS

Two finite element models of total ankle replacement prostheses were built to quantify peak and average contact pressures on the polyethylene insert surfaces. Models were validated by biomechanical testing of the two implant designs with use of pressure-sensitive film. The validated models were configured to replicate three potential misalignments with the most

CLINICAL RELEVANCE

version of the tibial component, version of the talar component, and relative component rotation of the two-component design. The misalignments were simulated with use of the computer model with physiologically relevant boundary loads.

RESULTS

With use of the manufacturer's guidelines for positioning of the two-component design, the predicted average joint contact pressures exceeded the yield stress of polyethylene (18 to 20 MPa). Pressure magnitudes increased as implant alignment was systematically deviated from this reference position. The three-component design showed lower-magnitude contact pressures in the standard position (<10 MPa) and was generally less sensitive to misalignment. Both implant systems were sensitive to version misalignment.

CONCLUSIONS

In the tested implants, a highly congruent mobile-bearing total ankle replacement design yields more evenly distributed and lower-magnitude joint contact pressures than a less congruent design. Although the mobile-bearing implant reduced susceptibility to aberrant joint contact characteristics that were induced by misalignment, predicted average contact stresses reached the yield stress of polyethylene for imposed version misalignments of >5 degrees.