Malalignment is often postulated as the main reason for the high failure rate of total ankle replacements (TARs). Only a few studies have been performed to correlate radiographic TAR malalignment to the clinical outcome, but no consistent trends between TAR alignment parameters and the clinical outcome were found. No standard TAR alignment measurement method is present, so reliable comparison between studies is difficult. Standardizing TAR alignment measurements and increasing measurable parameters on radiographs in the clinic might lead to a better insight into the correlation between malalignment and the clinical outcome. This study aims to develop and validate a tool to semi-automatic measure TAR alignment, and to improve alignment measurement on radiographs in the clinic. A tool to semi-automatically measure TAR alignment on anteroposterior and lateral radiographs was developed and used by two observers to measure TAR alignment parameters of ten patients. The Intraclass Coefficient (ICC) was calculated and accuracy was compared to the manual measurement method commonly used in the clinic. The tool showed an accuracy of 76% compared to 71% for the method used during follow-up in the clinic. ICC values were 0.94 (p<0.01) and higher for both inter-and intra-observer reliability. The tool presents an accurate, consistent, and reliable method to measure TAR alignment parameters. Three-dimensional alignment parameters are obtained from two-dimensional radiographs, and as the tool can be applied to any TAR design, it offers a valuable addition in the clinic and for research purposes

An increasingly used treatment for end-stage ankle osteoarthritis is total ankle replacement (TAR). However, implant loosening and subsidence are commonly reported complications, leading to relatively high TAR failure rates. Malalignment of the TAR has often been postulated as the main reason for the high incidence of these complications. It remains unclear to what extent malalignment of the TAR affects the stresses at the bone-implant interface. Therefore, this study aims to elucidate the effect of TAR malalignment on the contact stresses on the bone-implant interface, thereby gaining more understanding of the potential role of malalignment in TAR failure. FE models of the neutrally aligned as well as malaligned CCI Evolution TAR implant (Van Straten Medical) were developed. Separate models were developed for the tibial and talar segment, with the TAR components in neutral alignment and 5° and 10° varus, valgus, anterior and posterior malalignment, resulting in a total of 9 differently aligned TAR models. Loading conditions of the terminal stance phase of the gait cycle, when the force on the ankle joint is highest (5.2x body weight), were applied. Peak and mean contact pressure and shear stress at the bone-implant interface were analyzed. Also, stress distributions on the bone-implant interface were visualized. In the neutrally aligned tibial and talar TAR models, peak contact pressures of respectively 98.4 MPa and 68.2 MPa, and shear stresses of respectively 49.3 MPa and 39.0 MPa were found. TAR malalignment increases peak contact pressure and shear stress on the bone-implant interface. A maximum peak contact pressure of 177 MPa was found for the 10° valgus malaligned tibial component and the highest shear stress found was 98.5 MPa for the 10° posterior malaligned talar model. Upon TAR malalignment contact stresses increase substantially, suggesting that proper orientation of the TAR is needed to minimize peak stresses on the bone-implant interface. This is in line with previous studies, which state that malalignment considerably increases bone strains, micromotion, and internal TAR contact pressures, which might increase the risk of TAR failure. Further research is needed to investigate the relationship between increased contact stresses at the bone-implant interface and TAR failure

Varus ankle osteoarthritis (OA) is typically associated with peritalar instability, which may result in altered subtalar joint position. This study aimed to determine the extent to which total ankle replacement (TAR) in varus ankle OA can restore the subtalar position alignment using 3-dimensional semi-automated measurements on WBCT. Fourteen patients (15 ankles, mean age 61) who underwent TAR for varus ankle OA were retrospectively analyzed using semi- automated measurements of the hindfoot based on pre-and postoperative weightbearing WBCT (WBCT) imaging. Eight 3-dimensional angular measurements were obtained to quantify the ankle and subtalar joint alignment. Twenty healthy individuals were served as a control groups and were used for reliability assessments. All ankle and hindfoot angles improved between preoperative and a minimum of 1 year (mean 2.1 years) postoperative and were statistically significant in 6 out of 8 angles (P<0.05). Values The post-op angles were in a similar range to as those of healthy controls were achieved in all measurements and did not demonstrated statistical difference (P>0.05). Our findings indicate that talus repositioning after TAR within the ankle mortise improves restores the subtalar position joint alignment within normal values. These data inform foot and ankle surgeons on the amount of correction at the level of the subtalar joint that can be expected after TAR. This may contribute to improved biomechanics of the hindfoot complex. However, future studies are required to implement these findings in surgical algorithms for TAR in prescence of hindfoot deformity

Abstract. Introduction. Ankle arthritis is estimated to affect approximately 72 million people worldwide. Treatment options include fusion and total ankle replacement (TAR). Clinical performance of TAR is not as successful as other joint replacement and failure is poorly understood. Finite element analysis offers a method to assess the strain in bone implanted with a TAR. Higher strain has been associated with microfracture and alters the bone-implant interface. The aim of this study was to explore the influence of implant fixation on strain within the tibia when implanted with a TAR through subject-specific models. Methods. Five cadaveric ankles were scanned using a Scanco Xtreme CT. The Tibia and Talus were segmented from each scan and virtually implanted with a Zenith TAR (Corin, UK) according to published surgical technique. Patient specific models were created and run at five different positions of the gait cycle corresponding to peak load and flexion values identified from literature. Bone material properties were derived from CT greyscale values and all parts were meshed with linear tetrahedral elements. The implant-bone interface was adjusted to fully-fixed or frictionless contact, representing different levels of fixation post-surgery. Strain distributions around the tibial bone fixation were measured. Results. Initial results showed clear differences in strain distributions both between different ankle specimens and fixation levels, with highest strain occurring within the bone at the tip of the tibial stem. Frictionless contact gave higher strain outputs than fully-fixed for all specimens with a range 0.12–0.3% and 0.07%–0.13% respectively. Conclusions. In all specimens, strain was higher in the frictionless contact, which may be considered representative of no bony ingrowth, highlighting fixation may be a critical factor in TAR failure. Differences observed between specimens highlights that TAR may not be a suitable intervention for all patients, due to variation in bone quality and anatomy. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Total ankle replacement (TAR) is increasingly used in the treatment of end-stage ankle arthropathy, but much debate exists about the clinical result. The goals of present study are: 1) to provide an overview of the clinical outcome of 58 TAR's in a single centre and 2) to assess the association between radiological characteristics and clinical outcome. We reviewed a prospective included cohort of 58 TAR's in 54 patients with a mean age of 66.9 (range 54–82) and a mean follow-up of 21.6 months (range 1.45–66.0). The TAR's where performed by a single surgeon in a single centre (MUMC) between 2010 and 2015, using the CCI ankle replacement. A standard surgical protocol and standardized post-op rehabilitation was used. Patients were followed-up pre-op and at 1 day, 6 weeks, 3–6–12 months and yearly thereafter post-op. The AOFAS and range of motion (ROM) were assessed and all complications, re-operations and the presence of pain were recorded. Radiographic assessment consisted of the estimation of prosthesis alignment, migration, translation and radiolucent lines using the Rippstein protocol (1). The clinical outcome was compared with a systematic review of TAR outcome. Ten intra-operative complications occurred and 9 were malleolar fractures. Post-operative complications occurred in 20 out of the 54 patients (37.0%). Impingement (5/54 patients), deep infection (4/54 patients), delayed wound healing (3/54 patients) and minor nerve injuries (3/54 patients) were the most frequently recorded. 18 patients (31.0%) underwent one or more re-operations and 12 of these 18 patients underwent a component revision (mostly the PE insert) or a conversion to arthrodesis. Despite the complications and revisions, the functional outcome improved. Radiologically 15.8% of the TAR's were positioned in varus and 1.8% in valgus. Migration in the frontal and sagittal plane is seen in 3 and 2 TAR's respectively. Radiolucency is significantly increasing with the follow-up time (p=0.009). Migration in the frontal plane is significantly associated with conversion to arthrodesis (p=0.005) and migration in the sagittal plane to revision of a component or conversion to arthrodesis (p=0.04). Finally, pain is significantly associated with re-operations (p=0.023) and complications (p=0.026). Remarkable is that the clinical outcome is independent of the direct post-op alignment of the TAR. The complication-, re-operation and revision or conversion to arthrodesis rates makes the clinical outcome of TAR still questionable favourable. Especially the complication and re-operation incidences are greater than found in the systematic review. However, it is remarkable that the minor complications and re-operations not related to the TAR are not often mentioned in the literature. Radiographic characteristics could be of value in predicting this clinical outcome and thereby influence the post-operative handling. In conclusion, our results show relatively high incidences of complications (37.0%) and re-operations (31.0%) when minor complications and re-operations are included. TAR clinical outcome can be predicted by radiographic migration characteristics and pain

Total ankle replacement (TAR) is contraindicated in patients with significant talar collapse due to AVN and in these patients total talus body prosthesis has been proposed to restore ankle joint. To date, five studies have reported implantation of a custom-made talar body in patients with severely damaged talus, showing the limit of short-term damage of tibial and calcaneal thalamic joint surfaces. Four of this kind of implants have been performed. The first two realized with “traditional” technology CAD-CAM has been performed in active patients affected by “missing talus” and now presents a survival follow-up of 15 and 17 years. For the third patient affected by massive talus AVN we designed a 3D printed porous titanium custom talar body prosthesis fixed on the calcaneum and coupled with a TAR, first acquiring high-resolution 3D CT images of the contralateral healthy talus that was “mirroring” obtaining the volume of fractured talus in order to provide the optimal fit. Then the 3D printed implant was manufactured. The fourth concern a TAR septic mobilization with high bone loss of the talus. The “two-stage” reconstruction conducted with the implant of total tibio-talo-calcaneal prosthesis “custom made” built with the same technology 3D, entirely in titanium and using the “trabecular metal” technology for the calcaneous interface. Weightbearing has progressively allowed after 6 weeks. No complications were observed. All the implants are still in place with an overall joint mobility ranging from 40° to 60°. This treatment requires high demanding technical skills and experience with TAR and foot and ankle trauma. The 15 years survival of 2 total talar prosthesis coupled to a TAR manufactured by a CAD-CAM procedure encourages consider this 3D printed custom implant as a new alternative solution for massive AVN and traumatic missing talus in active patients

Abstract. OBJECTIVE. Flattening of the talar dome is observed clinically in haemarthropathy as structural and functional changes advance but has not been quantified yet. In order to confirm clinical observation, and assess the degree of change, morphological measurements were derived from MR images. METHODS. Four measurements were taken, using ImageJ (1.52v), from sagittal MRI projections at three locations – medial, lateral and central: Trochlear Tali Arc Length (TaAL), Talar Height (TaH), Trochlear Tali Length (TaL), and Trochlear Tali Radius (TaR). These measurements were used to generate three ratios of interest: TaR:TaAL, TaAL:TaL, and TaL:TaH. With the hypothesis of a flattening of the talar dome with haemarthropathy, it was expected that TaR:TaAL and TaL:TaH should be greater for haemophilic ankles, and TaAL:TaL should be smaller. A total of 126 MR images (ethics: MEEC 18–022) were included to assess the difference in those ratios between non-diseased ankles (33 images from 11 volunteers) and haemophilic ankles (93 images from 8 patients’ ankles). Non-diseased control measurements were compared to literature to assess the capacity of doing measurements on MRI instead of radiographs or CT. RESULTS. Reasonable agreement was found between measurements on non-diseased ankles and those from literature, with greatest variance in TaAL. The medial talus demonstrated decreases in all dimensions with haemophilia (TaR=2.4%, TaL=14.7%, TaAL=19.5% and TaH=27.8%; t-test at p<0.05), as did the lateral talus (TaR=6.2%, TaL=6.8%, TaAL=12.0% and TaH=22.4%; t-test at p<0.05). The effect on the central talus was not significant. TaAL:TaL showed talar flattening in the medial and lateral haemophilic talus (healthy medial=1.21, lateral=1.20; haemophilic medial=lateral=1.14). CONCLUSION. The results demonstrate non-uniform increased influence of haemarthropathy at the medial and lateral talar extremes, with relatively healthy measurements seen in the centre. The degree of morphological change is however progressive, differing with each haemophilic ankle. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Abstract. Objectives. Implant loosening remains a common cause of total ankle replacement (TAR) revision, and has been associated with wear-mediated osteolysis. Limited pre-clinical studies for TARs have been reported and the variety of experiment settings make it difficult to compare wear rates. Factors such as simulator control mechanism; whether pneumatic or electromechanical, may influence the integrity of the simulator outputs with respect to input profiles. This study compares the wear of a TAR, tested in electromechanical and pneumatic experimental simulators under identical input conditions. Methods. Twelve medium BOX® (MatOrtho Ltd) TARs (n=6 for each simulator) were tested in an electromechanical and pneumatic knee simulator (Simulation Solutions, UK) for 3 million cycles (Mc). Standard ‘Leeds’ displacement-controlled inputs were used. Kinematic performance was investigated by comparing the output profiles against the maximum demanded input values. The lubricant used was 25% new-born calf serum and wear was determined gravimetrically. Results. There was no significant difference (P=0.66) in wear rate between simulators (electromechanical = 15.96 ± 6.37mm. 3. /Mc; pneumatic = 14.51 ± 5.27mm. 3. /Mc). The electromechanical simulator (3157.06 ± 1.52N) achieved the maximum load (3150N), but the pneumatic simulator was unable to attain the demand (2542.34 ± 86.52N). Maximum AP displacement from the electromechanical simulator was 3.27 ± 0.07mm (3.1mm input), compared to 3.62 ± 0.95mm from the pneumatic simulator. Internal/external rotation angle was 7.97° ± 0.00 (8° input) and 7.24° ± 0.12 from the electromechanical and pneumatic simulators respectively. Both simulators achieved the demanded flexion angle (±15°). Conclusions. The outputs from the electromechanical simulator followed the input profiles more closely than the pneumatic simulator. Despite these differences, there was no significant influence on wear rate. The variation in kinematics between simulators was not sufficient to significantly change the tribological conditions of the TAR. The authors recommend the use of electromechanical simulators for future studies where more demanding and adverse conditions may be applied. Declaration of Interest. (a) fully declare any financial or other potential conflict of interest

Total ankle replacement (TAR) is a substitute to ankle fusion, replacing the degenerated joint with a mechanical motion-conserving alternative. Compared with hip and knee replacements, TARs remain to be implanted in much smaller numbers, due to the surgical complexity and low mid-to-long term survival rates. TAR manufacturers have recently explored the use of varying implant sizes to improve TAR performance. This would allow surgeons a wider scope for implanting devices for varying patient demographics. Minimal pre-clinical testing has been demonstrated to date, while existing wear simulation standards lack definition. Clinical failure of TARs and limited research into wear testing defined a need for further investigation into the wear performance of TARs to understand the effects of the kinematics on varying implant sizes. Six medium and six extra small BOX® (MatOrtho) TARs will be tested in a modified knee simulator for 5 million cycles (Mc). The combinations of simulator inputs that mimic natural gait conditions were extracted from ankle kinematic profiles defined in previous literature. The peak axial load will be 3.15 kN, which is equivalent to 4.5 times body weight of a 70kg individual. The flexion profile ranges from 15° plantarflexion to 15° dorsiflexion. Rotation about the tibial component will range from −2.3° of internal rotation to 8° external rotation, while the anterior/posterior displacement will be 7mm anterior to −2mm posterior throughout the gait cycle. The components will be rotated through the simulation stations every Mc to account for inter-station variability. Gravimetric measurements of polyethylene wear will be taken at every Mc stage. A contact profilometer will also be used to measure average surface roughness of each articulating surface pre-and-post simulation. The development of such methods will be crucial in the ongoing improvement of TARs, and in enhancing clinical functionality, through understanding the envelope of TAR performance

Total ankle replacement (TAR) is the main surgical option in case of severe joint osteoarthritis. The high failure rate of current TAR is often associated to inappropriate prosthetic articulating surfaces designed according to old biomechanical concepts such the fixed axis of rotation, thus resulting in non-physiological joint motion. A recent image-based 3D morphological study of the normal ankle (Siegler et al. 2014) has demonstrated that the ankle joint surfaces can be approximated by a saddle-shaped cone with its apex located laterally (SSCL). We aimed at comparing the kinematic effects of this original solution both with the intact joint and with the traditional prosthetic articulating surfaces via in-silico models and in-vitro measurements. Native 3D morphology of ten normal cadaver ankle specimens was reconstructed via MRI and CT images. Three custom-fit ankle joint models were then developed, according to the most common TAR designs: cylindrical, symmetrically-truncated medial apex cone (as in Inman's pioneering measures), and the novel lateral apex cone, i.e. SSCL. Bone-to-bone motion, surface-to-surface distance maps, and ligament forces and deformations were evaluated via computer simulation. Prototypes of corresponding prosthesis components were designed and manufactured via 3D-printing, both in polymer-like-carbon and in cobalt-chromium-molybdenum powders, for in-vitro tests on the cadaver specimens. A custom testing rig was used for application of external moments to the ankle joint in the three anatomical planes; a motion tracking system with trackers pinned into the bone was used to measure tibial, talar and calcaneal motion (Franci et al. 2009), represented then as tibiotalar, subtalar and ankle complex 3D joint rotations. Each ankle specimen was tested in the intact joint configuration and after replacement of the articulating surfaces according with the three joint models: cylindrical, medial apex cone and SSCL. Results. Small intra-specimen data variability in cycle-to-cycle joint kinematics was found in all cadaver ankles, the maximum standard deviation of all rotation patterns being smaller than 2.0 deg. In-silico ligament strain/stress analysis and in-vitro joint kinematic and load transfer measurements revealed that the novel SSCL surfaces reproduce more natural joint patterns than those with the most common surfaces used in current TAR. TAR based on a saddle-shaped skewed truncated cone with lateral apex is expected to restore more normal joint function. Additional tests are undergoing for further biomechanical validation. The present study has also demonstrated the feasibility and the quality of the full process of custom TAR design and production for any specific subject. This implies a thorough procedure, from medical imaging to the production of artificial surfaces via 3D printing, which is allowing for personalised implants to become the future standard in total joint replacement

Total ankle replacement (TAR) has a mean survivorship of 77% at 10 years which is poor compared to other types of joint arthroplasty. Osteolysis and aseptic loosening are commonly cited TAR failure modes, the mechanisms of which are unknown. Retrieval analyses of TAR devices may reveal mechanisms of failure similar or dissimilar to other joint replacements. This study investigated whether TAR explants exhibit similar damage modes to those recognised in other total joint replacements. 22 Ankle Evolution System TARs (Transystème, Nimes, France) were implanted and retrieved by the same surgeon. Mean implantation time was 7.8 yrs (5.3 to 12.1 range). Pain and/or loosening were the indications for revision. Macro photography, an Alicona Infinite microscope and the Hood/Wasielewski scale were used to classify damage modes on the polyethylene insert. Scanning electron microscopy with energy dispersive X-ray spectroscopy was used to determine the composition of third body debris and to image the fixation surface of the tibial components. Mean damage score was 185.4 (± 40.0 SD). Damage modes common to total knee replacements were identified on both the superior and inferior insert surfaces, these included: burnishing, scratching, pitting and abrasion. Titanium particles, hydroxyapatite fragments and bone debris were embedded in the insert surfaces. Fixation surface delamination was identified by the ongrowth of tissue between the cobalt chromium substrate and titanium alloy coating. Damage modes indicative of high levels of wear and deformation were evident. Pitting caused by third body debris was abundant and suggested fixation surface wear and failure

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