Purpose. Total Ankle Replacement (TAR) is increasingly being offered to patients as an alternative to arthrodesis for the operative management of debilitating end-stage ankle arthritis. The Mobility Total Ankle System is a third-generation design consisting of a three component, cementless, unconstrained, mobile-bearing prosthesis. This study reports the early results of a multi-centre prospective study of the Mobility prosthesis. This is the first such report by independent researchers. Method. The senior authors implanted 86 consecutive Mobility prostheses. The underlying diagnosis was primary OA in 24 ankles, secondary OA in 47 ankles and inflammatory arthritis in 15 ankles. There were 41 males (Mean age 67 / Range 51–87) and 44 females (Mean age 60 / Range 29–72). The mean BMI was 28 (Range 22–36) for males, and 28 (Range 20–39) for females. Previous ankle operations were performed in 24 patients, 22 of which were for fracture fixation. Ankles were classified according to the COFAS end-stage ankle arthritis classification system. Coronal plane deformity was quantified pre-operatively. Clinical outcome was assessed using the AOFAS hindfoot score. Radiological assessment was performed from weight-bearing radiographs, documenting post-operative alignment, osseous integration, edge-loading and heterotopic bone formation. The mean follow-up time was 40 months (Range 30–60). Survival analysis was calculated according to the Kaplan-Meier method. Failure was defined as exchange of any component of the TAR, arthrodesis or amputation. Results. Type 1 ankle arthritis was demonstrated in 54 ankles (63%). No patient had pre-operative coronal plane angulation > 20. In 30 ankles (35%), the pre-operative coronal alignment was neutral, and in 32 ankles (37%), the deformity was < 10. The mean AOFAS hindfoot score improved from 37.4 (Range 12–59) pre-operatively to 77.9 (Range 51–100) post-operatively. 78 (90%) of prosthetic components were implanted within 5 of the optimal position. Bone-implant interface abnormalities were identified in 16 ankles (18%). In total, 5 TARs required revision, 4 for aseptic loosening and one for component malpositioning. There was one conversion to arthrodesis, and one BKA for CRPS. 30 simultaneous procedures were performed in 28 patients. The most common was gastrocnemius recession. There were 8 re-operations, most commonly for impingement due to peri-articular ossifications. Delayed wound healing occurred in 3 patients, and there was one case of deep infection. There were 5 patients that sustained fractures of the medial malleolus: 2 were intra-operative, and underwent internal fixation. There are 6 patients being investigated for ongoing pain. The 2-year survival was 96.4% (95% CI 89.4–99.1) and 3-year survival was 91.7% (95% CI 83.3–96.3). Conclusion. Although early results of the Mobility TAR are encouraging for independent researchers, they do not match those reported by designer surgeons. Most patients achieve good pain relief and improved function post-operatively

Preoperative talar valgus deformity increases the technical difficulty of total ankle replacement (TAR) and is associated with an increased failure rate. Deformity of ≥15° has been reported to be a contraindication to arthroplasty. The goal of the present study was to determine whether the operative procedures and clinical outcomes of TAR for treatment of end-stage ankle arthritis were comparable for patients with preoperative talar valgus deformity of ≥15° as compared to those with <15°. We will describe the evolving surgical technique being utilized to tackle these challenging cases. Fifty ankles with preoperative coronal-plane tibiotalar valgus deformity of ≥15° “valgus” group) and 50 ankles with valgus deformity of <15° (“control” group) underwent TAR. The cohorts were similar with respect to demographics and components used. All TARs were performed by a single surgeon. The mean duration of clinical follow-up was 5.5 years (minimum two years). Preoperative and postoperative radiographic measurements of coronal-plane deformity, Ankle Osteoarthritis Scale (AOS) scores and Short Form (SF)-36 scores were prospectively recorded. All ancillary (intraoperative) and secondary procedures, complications and measurements were collected. The AOS pain and disability subscale scores decreased significantly in both groups. The improvement in AOS and SF-36 scores did not differ significantly between the groups at the time of the final follow-up. The valgus group underwent more ancillary procedures during the index surgery (80% vs 26%). Tibio-talar deformity improved significantly toward a normal weight-bearing axis in the valgus group. Secondary postoperative procedures were more common in the valgus group (36%) than the controls (20%). Overall, re-operation was not associated with poorer patient outcome scores. Metal component revision surgery occurred in seven patients (three valgus and four controls). These revisions included two deep infections (2%), one in each group, which were converted to hindfoot fusions. Therefore, 94% of the valgus group retained their original components at final follow-up. Thus far, this is the largest reported study that specifically evaluates TAR with significant preoperative valgus alignment, in addition to having the longest follow-up. Satisfactory midterm results were achieved in patients with valgus mal-alignment of ≥15°. The valgus cohort required more procedures during and after their TAR, as well as receiving more novel techniques to balance their TAR. Whilst longer term studies are needed, valgus coronal-plane alignment of ≥15° should not be considered an absolute contraindication to TAR if the associated deformities are addressed

Introduction. Comparative studies examining Fixed-Bearing (FB) and Mobile-Bearing (MB) Total Ankle Replacement (TAR) designs have demonstrated similar results and successful long-term outcomes for both. To date there has been no study directly comparing FB and MB designs of the same prosthesis. We present the first prospective randomised trial comparing patient satisfaction, functional outcomes and radiographic results of the Salto Talaris Fixed-Bearing and the Salto Mobile-Bearing Total Ankle Replacement in the treatment of end-stage ankle arthritis. Methods. A total of 108 adult patients with end-stage ankle arthritis were enrolled in the study between November 2014 and October 2021 with similar demographic comparison. Prospective patient-reported outcomes and standardised weightbearing ankle radiographs were performed preoperatively, at 6 weeks, 6 months and 12 months post-operatively, followed by yearly intervals. All surgeries were performed by a single non-design orthopaedic foot and ankle specialist with experience in over 200 Salto and Salto Talaris TAR prior to the study. Radiographs were examined independently by two clinicians. Complete patient data and radiographs were available for 103 patients with an average follow up of 2 years. Results. Both groups demonstrated statistically significant improvement from preoperative evaluation to most recent follow up with no statistically significant difference between the two groups in all outcome measures. Radiographic incidence of subchondral cyst formation was 8.9% and 38.2% for FB and MB, respectively. Talar subsidence occurred in 2.2% and 5.5% of FB and MB, respectively. Discussion. Our study demonstrates a higher than previously reported rate of cyst formation in the MB TAR and comparatively higher talar subsidence in the MB TAR vs FB however this did not correlate with clinical outcome measures which were favourable for both groups. Conclusion. Fixed-Bearing and Mobile-Bearing Total Ankle Replacement demonstrate comparable favourable

Recent advances in arthroplasty for the hip and the knee have motivated modern foot and ankle research to perfect the implant and technique for the optimal total ankle replacement. Unlike in the hip where different approaches can be done with similar implants, the approach of a total ankle is intimately associated to the prosthetic design. The anterior and lateral approaches have pros and cons regarding their respective soft tissue complications, osteotomy necessity, orientation of the bone cut and gutter visualization. While both have been studied independently, very few reports have compared both in the same setting. This study retrospectively looked at the difference in reoperations rate after each ankle arthroplasty within two years estimating that both had similar rate of return to the operating room. A retrospective study was conducted from a single center between 2014 and 2017 including a total of 115 total ankles performed by one of four fellowship-trained foot and ankle surgeon. Re-operations were reported in the charts as an operative report. The index approach used was determined by the surgeon's practice preference. Patients were included when they had a primary TAR in the timeframe noted and had a complete dataset up to at least the two-year data. This cohort comprised 67 anterior and 48 lateral with balanced demographic for age (95%CI 63–67 yo) and gender (47% F). The lateral group had more complex cases with higher COFAS type arthritis. Comparing the two groups, a total of 40 reoperations (7 anterior, 33 lateral) occurred in 27 patients (5A, 22L). One patient had up to four related reoperations. The only revision was in the anterior group. The only soft tissue reconstruction was an STSG in the lateral group. Nine reoperations were irrigation debridement related to an infective process (3 A, 6L). The majority (19/33) of reoperations in the lateral group were gutter debridement (8) or lateral hardware removal (11). Operative time was not statistically different. The odds ratio of having a reoperation with a laterally based TAR was 6.19 compared to the anterior group. This retrospective study outlines the intermediate results at two years of lateral and anterior total ankle replacements. This is a first study of this kind in the literature. This study did show that there were more reoperations after a laterally-based TAR than an anterior TAR, recognizing the significant case complexity imbalance between groups. This speaks to the relative increase resource utilization of laterally based TAR patients. Both implant designs carry different reoperation rates favoring the anterior group however larger prospective datasets will be needed with patient-reported outcome

Background:. Total ankle replacements (TAR) are not as successful as total hip or total knee replacements. A three-time increased revision rate is reported in registry data [1]. Therefrom, wear associated revisions are frequent [2]. However, there is little knowledge about the wear behavior of TAR. This may be partly related to the fact, that currently no standard for wear testing of TAR exists. The aim of this study is to define a biomechanical valid, force-controlled test specification for level walking of TAR. Material and Methods:. Basic requirements for force-controlled testing of TAR is the definition joint flexion, as well as active forces and torques acting on the joint and the definition of the ligamental stabilization of the joint. To specify flexion of the ankle, gait analysis was performed on patients treated with a TAR (HINTEGRA, Smith & Nephew) using skin mounted markers. Data about in-vivo forces is missing for TAR. Hence, determination of active forces and torques was based on mathematical models as described in the literature. A new testing device (figure 1) has been developed to measure ligamental stabilization of the ankle joint. Measurements were performed on 10 paired cadaver feet (n = 20). Measurements were performed in different flexion angles when applying anterior-posterior forces (± 160N) and internal-external torques (± 2,5 Nm) between the talus and the tibia. Results:. Three different testing scenarios for level walking were defined, representing the rehabilitation of the patient: . 1. Level walking after implantation with reduced kinematics & kinetics. 2. Level walking with an increasing range of motion (ROM). 3. Level walking with kinematics & kinetics based on the loading in the native/healthy joint. These definitions were based on the following findings: Gait analysis showed a reduced flexion for patients provided with TAR (ROM 14,9° TAR vs. 23,1° native side). Axial forces were defined to be 3.6 times in the native and 2.5 times body weight in TAR. Internal-external torques in total of 6.5 Nm and 10.1 Nm and AP-forces of 375N and 598N were defined for TAR and for the native joint, respectively. Laxity of the ankle joint was found to be directly related to the flexion of the ankle joint. Restraints of the joint during simulation were defined for every testing scenario with regard to the flexion angle and the acting AP-forces and IE torques. Conclusion:. Previous, published wear testing scenarios used self-defined displacement controlled methods. However, it is not known how TAR moves dynamically, especially regarding AP-motion. Therefore, the validity of these tests needs to be questioned. The new developed testing scenarios enable a biomechanically valid wear testing of TAR. In this study determined forces and torques have been shown to be comparable to total knee replacements (TKR). However, the flexion is massively decreased compared to TKR. Additionally, the TAR has a smaller contact area compared to TKR. Therefore increased contact pressures during simulation have to be assumed. Based on this study, wear-testing of TAR has been performed (see abstract: Wear performance of total ankle replacements)

Researchers and clinicians measuring outcomes following total ankle replacement (TAR) are challenged by the wide range of outcome measures used in the literature without consensus as to which are valid, reliable, and responsive in this population. This review identifies region- or joint-specific outcome measures used for evaluating TAR outcomes and synthesises evidence for their measurement properties. A standard search strategy was conducted of electronic databases MEDLINE, EMBASE and CINAHL (to June 2015) to identify foot/ankle measures in use. A best evidence synthesis approach was taken to critically appraise measurement properties [COnsensus-based Standards for the selection of health Measurement INstruments (COSMIN)] of identified measures. The review was restricted to English publications and excluded cross-cultural adaptations. Measurement properties collected from each article were coded for validity, reliability, responsiveness, or interpretability. Clinimetric evidence exists for identified measures tested in non-TAR populations, but were not the focus of this review. The search identified 14 studies to include in the best evidence synthesis with 32 articles providing clinimetric evidence for eight of the measures (one CBO, seven PRO), however only five measures were tested in a TAR population (Foot Function Index, Ankle Osteoarthritis Scale, American Orthopaedic Foot and Ankle Society Ankle-Hindfoot Scale [AOFAS], Foot and Ankle Outcome Score, Self-Reported Foot and Ankle Score). Five studies provided clinimetric evidence in a TAR population and their methodological quality was assessed: (1) Validity—two good quality studies examining different measures provide moderate evidence supporting construct validity (FFI, AOS, AOFAS self-reported items; SEFAS); (2) Reliability—two good quality studies examining different measures provide moderate evidence supporting internal consistency and test-retest reliability (FFI, AOS, AOFAS self-reported items; FAOS, SEFAS); (3) Responsiveness—three poor quality studies, thus unknown evidence for responsiveness; (4) Interpretability—two studies provide interpretability values (AOS, FFI, AOFAS self-reported items; AOS). This review offers a basis for choosing the most appropriate instrument for evaluating TAR outcomes. Numerous outcome measures were identified with evidence supporting their use in populations with various foot/ankle conditions, but none have strong evidence supporting use in a TAR population. Measures must have adequate clinimetric properties in all patient groups in which they are applied. Evidence supporting or critiquing an instrument should not be based on studies with poor quality methodology, as identified by this review. Further testing in a TAR population would benefit identified measures with emphasis on adequate sample sizes, testing a priori hypotheses, and evaluating their content validity for a TAR population

Introduction. Total ankle replacement (TAR) is less successful than other joint replacements with a 77% survivorship at 10 years. Predominant indications for revision include: Insert dislocation, soft tissue impingement and pain/stiffness. Insert edge-loading may be both a product and cause of these indications and was reported to affect 22% of patients with the, now withdrawn from market, Ankle Evolutive System (AES) TAR (Transysteme, Nimes, France). Compressive forces up to seven times body weight over a relatively small contact area (∼6.0 to 9.2 cm. 2. ), in combination with multi-directional motion potentially causes significant polyethylene wear and deformation in mobile-bearing TAR designs. Direct methods of measuring component volume (e.g. pycnometer) use Archimedes' principle but cannot identify spatial changes in volume or form indicative of wear/deformation. Quantitative methods for surface analysis bridge this limitation and may advance methods for analysing the edge loading phenomena in TAR. Aim. Determine the frequency of edge loading in a cohort of explanted total ankle replacements and compare the quantitative surface characteristics using a novel explant analysis method. Methods. Thirty-two AES TAR devices were implanted and retrieved by the same surgeon (UK Health Research Authority approval: 09/H1307/60). Mean implantation time was 7.8 years (1.5 to 12.1 range). Pain and/or loosening were the primary indications for revision. An Alicona Infinite microscope measured the entire superior surface of each insert (10× mag; 1.76µm lateral resolution). Abbott-Firestone curves were produced per insert to quantify the deviation of the insert surface from flat. Peak material volume (Vmp), core material volume (Vmc), core void volume (Vvc) and dale void volume (Vvv) were measured. Edge loading was identified visually by a depressed area in the insert surface indicative of articulation with the edge of the tibial component. Inserts were identified as either edge-loaded or not edge-loaded and the above analyses compared. Results. Seventeen inserts (53%) showed edge loading. Peak material volume (Vmp) was significantly increased for the edge loaded inserts 5.64 ± 5.42µm compared to the normal inserts 1.29 ± 0.954µm (Independent T-Test, P=0.005). No difference was found for the other volume parameters (Figure 2). A progressive change in insert form, beginning at the edges of the superior insert surface, was evident (Figure 1). Machining marks identified at the centre of several components supported this observation. Discussion. Insert edge loading affected 53% of TAR explants. The volume parameters showed a statistically significant inflection of material at the inserts' edge for the affected ankles. Spatial changes to insert form progressed over time in-vivo. Machining marks at the centre of several inserts remained which indicated the deformation/wear process commenced at the periphery of the insert. Normal ranges of volume change/redistribution are not established for TAR devices and the implications of insert form change are not yet understood. However, edge-loaded components composed over half of this cohort, which reflects the conflict between design simplicity and kinematic complexity. For any figures or tables, please contact authors directly (see Info & Metrics tab above).

Background:. There is little knowledge about wear performance of total ankle arthroplasties (TAR). However, revisions rates are high for TAR [1] and wear associated revisions are frequent [2]. Therefore, the aim of this study is . (1). To test the wear behavior of a TAR using a biomechanically valid testing scenario. (2). To test the influence of an alternative ceramic tibial component. (3). To test the long term wear performance of TAR. Material and Methods:. In the first part of this study the HINTEGRA (Smith & Nephew) TAR has been used for wear testing. Wear testing was performed on a modified AMTI knee simulator. Level walking according to a previous described testing standard [see abstract: Development of a force controlled testing scenario for total ankle replacements] has been used. Level walking was simulated in three clinical relevant situations, first simulating the reduced loading after implantation, secondly simulating an increasing range of motion and at last a loading pattern orientating at the loadings in the native/healthy joint. Every simulation was run for 3 million cycles, resulting in 9 million total cycles. In the second part of this study the metal tibial plateau was replaced by a ceramic tibial component (Biolox® Delta, CeramTec). Simulation was run, as described above, for additional 9 million cycles. Termed as a long term test, in total 18 million cycles of testing are performed. Results:. When simulating level walking with loadings assumed after implantation a wear rate of 19.5 ± 1,49 mg/Mc has been determined. Increasing the range of motion lead to a wear rate of 18.0 ± 2,56 mg/Mc and simulating loading as assumed in a healthy joint, a wear rate of 23.8 ± 1,47 mg/Mc was determined. When replacing the metal tibial component by a ceramic tray the wear rate decreased between 20–30% dependent on the tested scenario. No delamination occurred during 18 millon cycles of testing. Conclusion:. In this study, high wear rates for TAR were determined. Compared to standardized wear testing of total knee replacements in our laboratory the wear rate of TAR was approximately 2.5 times increased. Ceramics seem to be an option to decrease the wear rate. The high wear rate of the polyethylene may be a factor contributing to the high revision rates seen in TARs

Introduction. Total ankle replacement (TAR) is surgically complex; malalignment can arise due to surgical technique or failure to correct natural varus/valgus malalignment. Across joint replacement, malalignment has been associated with pain, component edge loading, increased wear and higher failure rates. Good component alignment is considered instrumental for long term TAR success. The conforming surface geometry of mobile bearing TARs leaves no freedom for coronal plane malalignment. The aim of this study was to investigate the biomechanical effect of coronal alignment on a mobile bearing TAR. Methods. Three TARs (Zenith, Corin Group) were tested under five coronal malalignment angles from 0–10° in a single station electromechanical knee simulator applying a typical ankle gait profile. As swing phase load is critical to TAR contact mechanics but will vary depending on the joint laxity. Swing loads of 100N, 300N and 500N were investigated. A positive control test with a swing load of 1000N was also studied, and was expected to eliminate the majority of lift off effects. Under each condition, the version was allowed to move freely while tests were performed, and the version profile under each alignment angle was recorded. Each test was carried out for 600 cycles in 25% bovine serum. Under the same loading conditions, but without lubrication, a Tekscan sensor recorded data from two cycles to assess the change in contact pressure and area at the five coronal angles. Results. Across the three TARs the effect of the swing phase load varied the biomechanics with a similar pattern. The high swing load of 1000N eliminates the majority of version while with 100N swing loads the TAR abducts for the length of the swing phase only realigning when the force increases, the extent dependent on the malalignment angle. At both 300N and 500N swing loads there is an oscillation apparent which changes the contact mechanics. The Tekscan results (Figure 1b) show changes in the contact area at three points in the load cycle; swing, the lower peak and the peak load (Figure 1a). With any degree of malalignment, component lift off is highly prevalent under lower swing phase loads of 100–300N. As the swing load is increased, this effect is only noticeable at greater malalignment angles. Discussion. The observed component lift off results in edge loading and peak pressures occurring at the insert edges. When the insert is 10 degrees coronally malaligned and the insert is brought fully into contact, the peak pressure reaches 16–18MPa, a pressure similar to the yield stress of polyethylene. The high contact pressures will likely elevate the wear and may increase the potential for polyethylene failure. Conclusion. Biomechanical testing has shown the malalignment of a total ankle replacement combined with the joint tension may change the contact mechanics and potentially increase wear. For any figures or tables, please contact authors directly (see Info & Metrics tab above).

Introduction/Purpose. Total ankle replacement (TAR) success has improved since first-generation implants, but patient satisfaction continues to be less than knee and hip replacements. Little is known about variations in distal tibia anatomy between genders and across ethnicities; therefore it is unclear the extent to which current TAR prostheses accommodate variability in patient size and shape. This study quantified distal tibia morphometrics relevant to TAR design, and assessed differences between ethnicities and genders. The hypotheses were: (1) The anterior-posterior (AP) location of the dwell point of the tibia is centralized; (2) The sagittal radius of curvature of the tibial articulation increases with bone size; (3) Differences in dwell point location or sagittal radii between genders and ethnicities can be attributed to size differences between those populations. Methods. Tibial CT scans were obtained from cadavers or individuals of various ethnicities (Table 1). Landmarks were defined on digital models created from the scans, including medial and lateral edges of the distal tibial articulation (Figure 1a), and sagittal contours of the articulation (Figure 1b). The articulation center was defined as the average center point of all contours (Figure 1c). The AP center and AP length at the level of a distal tibial resection for TAR were determined, and the AP offset of the articulation center was calculated (Figure 1c). Differences in metrics for each ethnic and gender group were determined using a one-way Anova (P<.05) with Tukey's method for differentiating groups. Regression fits of AP offset, average medial radius, and average lateral radius were determined. Utilizing AP length as a covariate, ANCOVA was utilized to assess differences in AP offset and sagittal radii between gender and ethnic groups (P<.05). Results. Descriptive statistics for AP length, AP offset, and medial/lateral radii are shown in Table 1, with Tukey groupings assigned. The relationship between medial and lateral radius was not consistent across all groups. AP length was a significant covariate for medial and lateral radii, but not AP offset. The relationship between lateral radius and AP length was significantly impacted by ethnicity (P<.001), but not by gender (P=.067) (Figure 2a). Medial radius versus AP length was significantly impacted by both ethnicity (P=.01) and gender (P<.03) (Figure 2b). Conclusion. This study illustrates for the first time the complexity of anatomical variation of the distal tibia across ethnic groups and between genders. The location of the articulation center is invariant to tibia size across each ethnicity. Medial and lateral sagittal radii generally increase with bone size, but the relative radii of the medial and lateral compartments are not consistent across ethnicities. These results highlight the need for increased anatomic understanding of the distal tibia, and implications on TAR design and technique

Introduction. Survival rates of recent total ankle replacement (TAR) designs are lower than those of other arthroplasty prostheses. Loosening is the primary indication for TAR revisions [NJR, 2014], leading to a complex arthrodesis often involving both the talocrural and subtalar joints. Loosening is often attributed to early implant micromotion, which impedes osseointegration at the bone-implant interface, thereby hampering fixation [Soballe, 1993]. Micromotion of TAR prostheses has been assessed to evaluate the stability of the bone-implant interface by means of biomechanical testing [McInnes et al., 2014]. The aim of this study was to utilise computational modelling to complement the existing data by providing a detailed model of micromotion at the bone-implant interface for a range of popular implant designs, and investigate the effects of implant misalignment during surgery. Methods. The geometry of the tibial and talar components of three TAR designs widely used in Europe (BOX®, Mobility® and SALTO®; NJR, 2014) was reverse-engineered, and models of the tibia and talus were generated from CT data. Virtual implantations were performed and verified by a surgeon specialised in ankle surgery. In addition to the aligned case, misalignment was simulated by positioning the talar components in 5° of dorsi- or plantar-flexion, and the tibial components in ± 5° and 10° varus/valgus and 5° and 10° dorsiflexion; tibial dorsiflexed misalignement was combined with 5° posterior gap to simulate this misalignment case. Finite element models were then developed to explore bone-implant micromotion and loads occurring in the bone in the implant vicinity. Results. Micromotion and bone loads peaked at the end of the stance phase for both the tibial and talar components. The aligned BOX and SALTO demonstrated lower tibial micromotion (with under 30% of bone-implant interface area subjected to micromotion larger than 100µm, as opposed to > 55% for Mobility; Figure 1). Talar micromotion was considerably lower for all designs, and no aligned talar component demonstrated micromotion larger than 100µm. The aligned SALTO showed the largest talar micromotion (Figure 2). Dorsiflexed implantation of all tibial components increased micromotion and bone strains compared to the reference case; interestingly, the SALTO tibial component, which demonstrated the lowest micromotion for the aligned case, also demonstrated the smallest changes in micromotion due to malpositioning (Figure 3). The posterior gap between the tibia and implant further increased bone strains. Dorsi- or plantar-flexed implantation of all talar components considerably increased micromotion and bone loads compared to the reference case (Figure 2), often resulting in micromotion exceeding 100µm. The SALTO talar component demonstrated the smallest changes in micromotion due to malpositioning. Discussion. The aligned Mobility had greater tibial micromotion than the SALTO and BOX, which agrees with higher revision rates reported in registry data (e.g. NZJR, 2014). The increased micromotion associated with dorsi- or plantar-flexion misalignment highlights the importance of aligning the implant correctly, and implies that SALTO can be more “forgiving” for malpositioning than the other TAR designs. Implant design and alignment are therefore important factors that affect the implant fixation and performance of the reconstructed ankle

We present the clinical and radiological outcome of a prospective series of 22 Buechel-Pappas Total Ankle Replacements (TAR) implanted in 19 patients with a mean follow-up of 9 years (range 6 to 13). The only published long term results of this prosthesis in the literature are from the originators' unit. Patients have been prospectively reviewed yearly since 1991. None was lost to follow-up. The primary diagnosis was rheumatoid arthritis in 11 and osteoarthritis in 8 patients. 12 patients were female. Mean patient age was 64 (range 39 to 81). At the time of review 4 patients (6 ankles) had died between 12 and 69 months post-operatively of unrelated causes with their prostheses in situ. One patient had a below knee amputation for chronic venous ulceration 11 years after a TAR which until that point had continued to function well. One patient with severe rheumatoid arthritis had the implant removed at 8 weeks for deep infection. Another patient with rheumatoid arthritis had the TAR revised to a tibio-talar-calcaneal fusion 59 months post-operatively for talar avascular necrosis. One patient has pain from impingement and another patient with rheumatoid arthritis has intermittent pain at 8 years following her TAR. Every other implant continues to function well. The New Jersey LCS ankle assessment scores increased from a mean of 35 pre-operatively to 82 post-operatively. The increases were largely due to pain relief and improved function with the pre-operative range of motion being preserved. These scores have been maintained in the long term. No surviving implant is radiologically loose. Our results suggest that the Buechel-Pappas TAR offers good clinical and radiological long-term results to patients with often disabling ankle arthritis

Introduction. Total ankle replacements (TAR) are a much debated alternative to ankle fusion for treatment of end stage arthritis. Compared with hip and knee replacements these are implanted in small numbers with less than 500 per year recorded by the joint registry for England and Wales. The small numbers are a likely result of typically low mid-term survival rates, as well as extensive contra-indications for surgery. There have been multiple generations of TARs consisting of both constrained and unconstrained designs but due to device classification pre-clinical testing has been minimal. Method. Five Zenith (Corin Group PLC), Titanium Nitride (TiN) coated, unconstrained TARs with conventional polyethylene inserts (Figure 1) were tested in an adapted knee simulator (Simulator Solutions, UK) for six million cycles (MC). The input parameters (Figure 2) were taken from available literature as there is no recognised ISO standard in place. A parametric study with three conditions was conducted to understand the impact of kinematic inputs on the polyethylene wear rate. These conditions aimed to understand the effect of both linear wear with isolated flexion, then multidirectional motion by implementing a rotational input with and without anterior/posterior (AP) displacement. Each condition was run for two MC. Stage One: Flexion and Load. Stage Two: Flexion, Load, Rotation and Displacement. Stage Three: Flexion, Load and Displacement. A lubricant of 25% bovine serum, 0.03% Sodium Azide solution was used to replicate the protein content of the natural joint capsule. The wear was measured gravimetrically every million cycles and surface measurements taken with a contacting profilometer. Results. The wear tests showed that under solely flexion and loading there was a low wear rate of 1.1±0.5 mm³/MC. With the addition of rotation and a 9mm AP displacement in Stage two the wear rate increased to 25.8±3.1 mm³/MC. When the displacement was removed in Stage three the wear rate decreased significantly to 15.2±2.5 mm³/MC (Figure 3). Discussion. Wear of the TAR was shown to vary significantly with kinematic input. As observed with other polymer total joint replacement articulations, unidirectional motion of the ankle yielded minimal wear of the Zenith TAR. Using an extreme anterior/posterior displacement motion from literature significantly increased the wear in combination with the rotation. After these wear stages the TiN tibials show obvious signs of wear in the region of polyethylene contact. The counter surface of the polyethylene insert showed both linear and radial scratches whereas as the curved surface of the insert and the talar component solely showed unidirectional wear lines. Conclusions. The design allows a large range of motion within the simulator. The wear rate presented by the Zenith TAR is similar to previous tests on unconstrained bearings and is highly dependent on the kinematic conditions

Statement of purpose. To describe the results and technique of ankle fusion following failed Total Ankle Replacement (TAR) in a limb reconstruction unit. Methods. Retrospective case note, microbiology and imaging review was performed on four consecutive patients referred to the limb reconstruction unit for salvage of infected total ankle replacement surgery since 2009. The patients were identified from operative list and tertiary referral records. A review of the current literature regarding TAR was performed. Results. Three patients were treated with a two stage surgical approach with initial removal of metalwork, debridement of infected tissue and temporary spanning external fixation. Local and systemic antibiotic therapy was then implemented for an average period of 53 days (range 48–61 days), before definitive fixation with a circular frame. One patient showed no clinical evidence of infection during preoperative investigation or intraoperatively, and was therefore treated with a single stage procedure with application of a circular frame. All four patients grew Staphylococci on culture of excised tissue and in one case there was additional growth of Proteus species. Bony union was achieved after fusion with a circular frame in all cases. Conclusion. TAR is gaining popularity for the treatment of severe talocrural arthritis, and several series with medium term results report low numbers of infected cases requiring revision. This case series discusses and describes the management strategy for failed TAR due to infection employed by a limb reconstruction unit

Background. Total Ankle Replacement (TAR) has become a common surgical procedure for severe Osteoarthritis of the ankle. Unlike hip and knee, current TARs still suffer from high failure rates. A key reason could be their non-anatomical surface geometry design, which may produce unnatural motion and load-transfer characteristics. Current TARs have articular surfaces that are either cylindrical or truncated cone surfaces following the Inman truncated cone concept from more than 60 years ago [1]. Our recent study demonstrated, that the surfaces of the ankle can be approximated by a Saddle-shaped, Skewed, truncated Cone with its apex directed Laterally (SSCL) [2]. This is significantly different than the surface geometry used in current TAR systems. The goal of this study was to develop and test the reliability of an in vitro procedure to investigate the effect of different joint surface morphologies on the kinematics of the ankle and to use it to compare the effect of different joint surface morphologies on the 3D kinematics of the ankle complex. Methodology. The study was conducted on ten cadaver ankle specimens. Image processing software (Analyze Direct. TM. ) was used to obtain 3D renderings of the articulating bones. The 3D bone models were then introduced into engineering design software packages (, Geomagic. TM. and Inventor. TM. ) to produce a set of four custom-fit virtual articular surfaces for each specimen: 1. Exact replica of the natural surfaces; 2. cylindrical; 3. truncated cone with apex oriented medially according to Inman's postulate; and 4. SSCL. The virtual TAR implants were exported to a 3D printing software and 3D physical models of each implant was produced in PLA using 3D printing (Figure 1). The intact cadaver was tested first in a specially design loading and measuring system [3] in which external moments were applied across the ankle in the three planes of motion and the resulting motion was measured through a surgical navigation system (Figure 1). Each of the four customized implant sets were then surgically introduced one at a time and the test was repeated. From the results, the ankle, subtalar and complex kinematics could be compared to that of the intact natural joint. Results and Conclusions. 1. Replacing the natural ankle joint surfaces by artificial exact replicas do not significantly affect the kinematic characteristics thus establishing good reliability of the experimental technique. This high reliability is an important finding proving that the combined factors involved in the process, such as replacing the natural surfaces with artificial replicas and the overall surgical procedure, do not significantly affect the kinematic characteristics of the ankle joint; 2. The SSCL implant produces close to intact joint kinematics (Figure 3), 3. The SSCL produces closer to normal kinematics then TARs with either cylindrical surfaces or those representing a symmetric truncated cone with apex oriented medially (Figure 3). For any figures or tables, please contact authors directly (see Info & Metrics tab above).

End-stage ankle arthritis (ESAA) is a debilitating disease that does not affect all individuals equally. Gender differences have been identified in patients with end-stage hip and knee arthritis and have stimulated research to explain these findings. The present study was undertaken to examine if gender has a significant effect on pre-operative disability and post-operative outcomes in patients with ESAA. Patients undergoing ankle arthrodesis (AA) or total ankle replacement (TAR) with minimum 2-year follow-up were identified in the Canadian Orthopaedic Foot and Ankle Society prospective ankle reconstruction database. Demographic data, revision data, patient satisfaction questionnaires, and outcome data using the Ankle Osteoarthritis Scale (AOS) and Short-form 36 (SF-36) health survey were collected. TAR: 384 patients were included, with 198 females and 186 males. Patient BMI, comorbidities, and duration of follow-up were similar between groups. Males were slightly older at the time of surgery (65.1 vs 62.4 years, p=0.01)). The most common etiology was post-traumatic arthritis for both genders, however females had a higher rate of rheumatoid arthritis (17% vs 5%, p=0.001). Implant types included STAR, Hintegra, and Mobility, and were similar between groups. Preoperatively females had higher rates of pain and disability, demonstrated by lower SF-36 physical component scores (PCS) (31.0 vs 34.5, p<0.001), and higher AOS pain (54.7 vs 51.1, p=0.05) and AOS disability scores (66.5 vs 59.6, p<0.001). Postoperatively, both groups had significant improvement in PCS, AOS pain, and AOS disability scores. Females, however, continued to demonstrate lower PCS scores (38.3 vs 41.9, p<0.001) and higher AOS disability (31.0 vs 25.8, p=0.02) than males. Regression analysis found that preoperative PCS, gender, age, and arthritis etiology all had a significant impact on postoperative PCS scores, with preoperative PCS scores having the largest impact. Preoperative AOS pain and disability scores had the largest impact on postoperative AOS pain and disability scores, respectively. Gender had no significant impact on AOS pain and disability scores postoperatively. Patient satisfaction was similar between males and females postoperatively. Secondary surgery was performed in 13.6% of females and 16.1% of males. Five males and five females underwent revision to arthrodesis. In patients with ESAA, females tend to have higher pre-operative levels of pain and disability compared to males, which persists post-operatively. This is consistent with the hip and knee arthroplasty literature. This finding may be due to females undergoing surgery at more advanced disease states, arthritis etiology, referral bias, or treatment bias. Both males and females have significant and similar degrees of improvement in pain and disability scores after TAR, and reoperation rates and patient satisfaction rates are similar despite the apparent disparity in outcomes

Introduction. Coronal plane deformity can pose difficulties with balancing in Total Ankle Replacement (TAR). Current reports outline improved outcomes in the presence of varus deformity. Soft tissue balancing techniques are well described, but are limited by no link to eitiology and pathoanatomy of the deformity. Method. A prospective review of all the TAR by the senior author was performed to identify cases of pre-operative varus greater than 10°. A chart review was performed to identify aetiology, intraoperative findings, and operative techniques to achieve a balanced TAR. X-rays were examined to measure deformity and amount of correction. Volumetric rendering and segmentalisation was performed on pre- and post-CTs to identify anatomical defects, osteophyte formation, rotational and translational changes of the hindfoot joints. Results. Between January 2002 and January 2009 there were thirty-five cases from two hundred and thirty cases with varus deformity greater than 10°, with an average 17° varus angle (range 10° to 30°). Multiple sprains and instability over several years was seen in 62% of patients. Clinically, increasing varus was associated with cavovarus foot position. Incongruent deformities had intact tibial plafond. Congruent deformities had tibial defects in the anteromedial tibial plafond and associated anterolateral tibial ostephyte. Increasing deformity often had lateral fibula osteophytes and ossicles between fibula osteophyte and anterolateral talar body. In more severe cases, 3D analysis showed the talus was anteriorly displaced and internally rotated. Post operative alignment improved from 17° to 1.5°. Conclusion. Understanding the pathoanatomy of the arthritic ankle with coronal plane deformity can help plan the surgical techniques required to correct this often challenging surgical reconstruction

Introduction. Total Ankle replacement designs continue to evolve, and provide an alternative to ankle arthrodesis for patients with ankle arthritis. It has been our practice to offer total ankle replacement to selected patients with ankle arthritis. The purpose of this study was to analyse the short term results of our patients with the Mobility R Total Ankle Replacement (TAR) system. Methods. All patients who received TAR in our practice from 2004 to 2011 were reviewed. American Orthopaedic Foot and Ankle Scores AOFAS were assessed and compared both preoperatively and at time of follow-up. All complications both intra-operative and post-operatively were noted. Weight bearing X-rays were taken at follow-up, and implant alignment and the presence of lucencies were noted. Results. 21 patients were evaluated. All showed an improvement in AOFAS scores; however the improvement showed a wide variation. All patients showed an improvement in pain scores. Post-operative ankle stiffness, specifically dorsi-flexion, was problematic in several patients. Marked prolonged swelling was problematic for many patients. Conclusions. Total ankle replacement provides a good option for patients with ankle arthritis. Swelling and post-operative stiffness continue to be a problem, and should be explained to patients. MULTIPLE DISCLOSURES

We aimed to review the outcome of Agility total ankle replacements carried out in our institution between 2002 and 2006. Follow-up consisted of clinical and radiological review pre-operatively, then at 6 weeks, 6 and 12 months, and annually until 10 years post op. Clinical review included the American Orthopaedic Foot and Ankle Score, satisfaction and pain scores. Case notes were reviewed to determine intra and post-operative complications. 30 arthroplasties were performed in 30 consecutive patients. Pre-operative diagnosis was rheumatoid arthritis(16), primary osteoarthritis(12) and post-traumatic osteoarthritis(2). After a mean follow up of 6.2 years (1.4–10.1), 4 patients had died, and 22 out of the remaining 24 were available for follow-up. Intra operative complications included lateral malleoli fracture(3) and superficial peroneal nerve injury(2). Post operative complications included 1 early death, but this was not related to the surgical procedure. Two patients developed deep infections of the prosthesis. One underwent removal of the implant; the other is on long term oral antibiotic therapy. One patient had delayed union of the syndesmosis and six patients had non-union. On clinical assessment, patients' AOFAS scores improved from mean 40.4 pre-op to 83.5 post-op (p< 0.001). Radiological assessment of the tibial component revealed 25 (93%) patients had lucency in at least one zone in the AP radiograph. We found a relatively high level of re-surgery and complications following Agility total ankle replacement. A 7% revision rate is much higher than would be tolerated in knee or hip arthroplasty, but compares favourably to other studies of TAR. Despite radiological features which suggest loosening, the high rate of re-surgery and complications; patients are generally satisfied with the procedure, reporting lower levels of pain and improved function. Overall we feel that the Agility ankle is an acceptable alternative to ankle arthrodesis, however patients need to be warned of the risk of re-surgery

Purpose. Coronal plane malalignment at the level of the tibiotalar joint is not uncommon in advanced ankle joint arthritis. It has been stated that preoperative varus or valgus deformity beyond 15 degrees is a relative contraindication and deformity beyond 20 degrees is an absolute contraindication to ankle joint replacement. There is limited evidence in the current literature to support these figures. The current study is a prospective clinical and radiographic comparative study between patients who underwent total ankle arthroplasty with coronal plane varus tibiotalar deformities greater than 10 degrees and patients with neutral alignment, less than 10 degrees of deformity. Method. Thirty-six ankles with greater than 10 degrees of varus alignment were compared to thirty-six ankles which were matched for implant type, age, gender, and year of surgery. Patients completed preoperative and yearly postoperative functional outcome scores including the American Orthopaedic Foot and Ankle Society (AOFAS) Ankle-Hindfoot scores, the Ankle Osteoarthritis Scale (AOS) and the Short Form-36 Standard Version 2.0 Health Survey. Weightbearing preoperative and postoperative radiographs were obtained and reviewed by four examiners (AC, AQ, TD, TT) and measurements were taken of the degree of coronal plane deformity. Results. After a mean follow-up of 27 months (9–54), the varus ankles improved significantly on the AOFAS (P<0.0001), AOS-Pain Score (P<0.0001), AOS-Disability Score (P<0.0001), and SF-36 Physical Component Score (P<0.0001). There was no improvement in SF-36-Mental Component Score. (P=0.722). There was no statistically significant differences between the two groups when comparing AOFAS (P=0.155), AOS-Pain Score (P=0.854), AOSDisability Score (P=0.593), SF-36-Physical Component Score (P=0.433), SF-36 Mental Component Score (P=0.633). Sixteen of Thirty-Six ankles in the varus group needed a secondary procedure (implant failure, infection, malalignment) which was approaching significance in comparison to eight ankles in the neutral group. (P = 0.079). Secondary procedures in the varus group included: tendon transfers, calcaneal / metatarsal / malleolar ostoetomies and ligament reconstructions. Radiographically, the pre-operative coronal plane varus tibiotalar deformity averaged 19.4 6.4 and postoperatively 1.44 2.6 (P< 0.0001). There was no statistical difference in post operative tibiotalar alignment between the varus and neutral groups (P<0.05). Conclusion. The clinical outcome of TAR performed in ankles with pre-operative varus alignment >10 degrees is comparable with that of neutrally aligned ankles. The increased number of secondary procedures in the varus group was attributed to the complexity of the deformity and the steep learning curve. Outcomes as measured radiographically and through validate scores were similar to patients without deformity suggesting that varus coronal plane deformity of the talus is not a contraindication to total ankle replacement