L’hallux varus est une déformation du premier rayon avec désaxation médiale de la première phalange par rapport à l’axe du métatarsien. L’incidence de cette complication est relativement fréquente, rapporté dans la littérature de 2 à 15,4 %. La déformation est considérée comme souple s’il est possible de réduire passivement la désaxation tout en conservant une mobilité articulaire. La forme enraidie est souvent le résultat d’une contracture ancienne et devient dès lors non-réductible et sans mobilité en position axée. La déviation interphalangienne est également composée d’une supination de l’hallux et d’une flexion dorsale de la phalange proximale, la mobilité interphalangienne est évaluée, principalement sa capacité de flexion dorsale (extension) ou sa raideur en flexion. La déformation terminale et enraidie représente la griffe fixée ou cock-up deformity. La présence de craquements douloureux intra-articulaires lors de la manipulation de l’articulation métatarso-phalangienne peut indiquer une arthrose sous-jacente et doit être recherchée en position de réduction neutre de l’hallux. L’évaluation radiologique est indispensable afin d’identifier les différents éléments de la déformation. Le premier élément décisionnel est la réductibilité et la souplesse en position de réduction de la première articulation métatarso-phalangienne. Toute situation de raideur articulaire doit toujours faire évoquer la réalisation d’une arthrodèse. La réalisation des techniques qui conservent la mobilité impose un orteil parfaitement souple et réductible. Sur une articulation souple, les transferts peuvent être proposés mais la reconstruction ligamentaire statique est plus facile à régler. La correction de l’angle intermétatarsien doit être réalisé s’il est inférieur à 6°. L’arthrodèse est la solution la plus fiable pour les déformations enraidis et fixés. Elle présente très certainement le moins de risque d’échec. Niveau de preuve V ; avis d’expert.

Background: To our knowledge, no study is available comparing the change in ankle mechanics during gait after total ankle arthroplasty (TAA) based on the origin of the osteoarthritis. As the nature of trauma is different in patients sustaining post-fracture ankle osteoarthritis (PFOA) from those sustaining post-sprain ankle osteoarthritis (PSOA), it could be expected that the outcomes of TAA, in terms of ankle mechanics during gait, would be different in the 2 groups. A prospective matched comparative study was therefore performed to investigate whether patients sustaining PFOA had different outcomes in terms of changes to ankle mechanics during gait (before surgery vs 1 year after surgery), compared with patients sustaining PSOA.Methods: Fifteen patients with PFOA and 15 patients with PSOA scheduled for primary TAA for pain relief were recruited and peer-matched based on their demographic and spatiotemporal data. All patients underwent a 3D gait analysis before and after surgery, during which a kinematic and kinetic multi-segment foot model was used to quantify inter-segmental joint kinematics and kinetics.Results: The PFOA group exhibited significantly lesser pre- vs postoperative increases in ankle (Shank-Calcaneus) joint peak power, and ankle (Shank-Calcaneus) joint work after TAA compared with the PSOA group. Furthermore, the results demonstrated a trend toward greater increases in peak ankle (Shank-Calcaneus) joint plantarflexion moment and in negative ankle (Shank-Calcaneus) joint work for the PSOA group compared with the PFOA group.Conclusion: This study suggests that patients sustaining PFOA have smaller pre- to postoperative gains in ankle (Shank-Calcaneus) joint power and ankle (Shank-Calcaneus) joint work during gait after TAA compared with patients sustaining PSOA, with modest between-group effects. Although evidence in TAA is lacking, insights from knee replacement suggest prehabilitation and nutritional support may mitigate deficits, representing a potentially essential strategy for PFOA patients requiring further validation.

Background: The tibiotalar arthrodesis for end-stage ankle osteoarthritis is a surgical procedure that leads to a modification of the kinematics of the adjacent joints and may result in the development of secondary osteoarthritic degeneration of the subtalar joint. It has previously been observed that subtalar arthrodesis in this context shows a lower fusion rate than isolated subtalar arthrodesis. This retrospective study reports the results of subtalar joint arthrodesis with previous ipsilateral tibiotalar arthrodesis and suggests some factors that may compromise the fusion of the joint. Methods: Between September 2010 and October 2021, 15 arthrodeses of the subtalar joint with screw fixation were performed in 14 patients, with a fusion of the ipsilateral tibiotalar joint. Fourteen of 15 cases used an open sinus tarsi approach, 13 were augmented with iliac crest bone graft, and 11 had supplemental demineralized bone matrix (DBM). The outcome variables were fusion rate, time to fusion, and revision rate. Fusion was assessed by radiographs and computed tomography scan. Results: Twelve of the 15 subtalar arthrodeses (80%) fused at the first attempt with an average fusion time of 4.7 months. Conclusion: In this limited retrospective case series, compared to the fusion rate of isolated subtalar arthrodesis reported in the literature, the rate of subtalar fusion in the presence of an ipsilateral tibiotalar arthrodesis was found to be lower. Level of Evidence: Level IV, retrospective case series.

Purpose: Emerging reports suggest an important involvement of the ankle/hindfoot alignment in the outcome of knee osteotomy; however, a comprehensive overview is currently not available. Therefore, we systematically reviewed all studies investigating biomechanical and clinical outcomes related to the ankle/hindfoot following knee osteotomies. Methods: A systematic literature search was conducted on PubMed, Web of Science, EMBASE and Cochrane Library according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and registered on international prospective register of systematic reviews (PROSPERO) (CRD42021277189). Combining knee osteotomy and ankle/hindfoot alignment, all biomechanical and clinical studies were included. Studies investigating knee osteotomy in conjunction with total knee arthroplasty and case reports were excluded. The QUality Appraisal for Cadaveric Studies (QUACS) scale and Methodological Index for Non-Randomized Studies (MINORS) scores were used for quality assessment. Results: Out of 3554 hits, 18 studies were confirmed eligible, including 770 subjects. The minority of studies (n = 3) assessed both high tibial- and distal femoral osteotomy. Following knee osteotomy, the mean tibiotalar contact pressure decreased (n = 4) except in the presence of a rigid subtalar joint (n = 1) or a talar tilt deformity (n = 1). Patient symptoms and/or radiographic alignment at the level of the ankle/hindfoot improved after knee osteotomy (n = 13). However, factors interfering with an optimal outcome were a small preoperative lateral distal tibia angle, a small hip–knee–ankle axis (HKA) angle, a large HKA correction (>14.5°) and a preexistent hindfoot deformity (>15.9°). Conclusions: Osteotomies to correct knee deformity alter biomechanical and clinical outcomes at the level of the ankle/hindfoot. In general, these changes were beneficial, but several parameters were identified in association with deterioration of ankle/hindfoot symptoms following knee osteotomy.

Background: Previous studies have examined the effect of concomitant triceps surae lengthening on ankle dorsiflexion motion at the time of total ankle arthroplasty (TAA). As plantarflexor muscle-tendon structures are important for producing positive ankle work during the propulsive phase of gait, caution should be exercised when lengthening triceps surae, as it may decrease plantarflexion strength. In order to develop an understanding of the work of the anatomical structures crossing the ankle during propulsion, joint work must be measured. The aim of this explorative study was to assess the effect of concomitant triceps surae lengthening with TAA on the resultant ankle joint work. Methods: Thirty-three patients were recruited to the study and divided into 3 groups of 11. The first group underwent both triceps surae lengthening (Strayer and TendoAchilles) and TAA (Achilles group), the second group underwent only TAA (Non-Achilles group), and the third group underwent only TAA, but had a greater radiographic prosthesis range of motion (Control group) compared to the first 2 groups. The 3 groups were matched in terms of demographic variables and walking speed. All patients underwent a 3D gait analysis 1 year after surgery to measure intersegmental joint work using a 4-segmented kinetic foot model. An analysis of variance (ANOVA) or Kruskal-Wallis test was used to compare the 3 groups. Results: The ANOVA showed significant differences between the 3 groups. Post hoc analyses suggested that (1) the Achilles group had less positive work at the ankle joint than the Non-Achilles and Control groups; (2) the Achilles group produced less positive work performed by all foot and ankle joints than the Control group; and (3) the Achilles and Non-Achilles groups absorbed less energy across all foot and ankle joints during the stance phase than the Control group. Conclusion: Concomitant triceps surae lengthening in TAA may reduce the positive work at the ankle joint. Level of Evidence: Level III, retrospective comparative study.

Supramalleolar osteotomy enables correction of the ankle varus deformity and is associated with improvement of pain and function in the short term and long term. Despite these beneficial results, the amount of surgical correction is challenging to titrate and the procedure remains technically demanding. Most supramalleolar osteotomies are currently planned preoperatively on 2-dimensional weight-bearing radiographs and executed peroperatively using free-hand techniques. This article encompasses 3-dimensional planning and printing techniques based on weight-bearing computed tomography images and patient-specific instruments to correct ankle varus deformities.

BACKGROUND:Although considerable literature can be found on the outcome of total ankle replacement (TAR), only a few studies have reported the results of the fixed-bearing Cadence prosthesis. This noninventor study reports a consecutive series of 60 Cadence TAR systems with a mean of 2.9 years' follow-up, focusing on clinical and radiographic outcomes and early complications. This study is the first to assess true postoperative radiographic ankle prosthesis range of motion (ROM) and to report an unanticipated serious adverse device effect.METHODS:Sixty patients who underwent primary TAR with the Cadence prosthesis between July 2016 and July 2019 were clinically and radiographically evaluated preoperatively and at last follow-up after the procedure. Revisions, additional procedures, implant failure, and complications were reported according to the classifications of Vander Griend and Glazebrook. Radiographic outcomes included radiographic TAR ROM, bone-implant interface, and alignment parameters.RESULTS:The survival rate of the prosthesis was 98.3%. The mean radiographic ankle ROM at the last follow-up was 24 degrees (9 degrees of dorsiflexion and 15 degrees of plantarflexion). The coronal and sagittal alignment of TAR was 90.8 degrees and 3.9 degrees, respectively. Bone-implant interface analysis revealed osteolysis in 9 ankles (15%) and radiolucent lines in 33 ankles (55%) occurring at both component interfaces. Intraoperative complications were 3 periprosthetic malleolar fractures (5%). Five talar implant fractures (implant failure of 8.3%) were observed, and 1 unexplained persistent pain that required a conversion from TAR to a tibiotalocalcaneal arthrodesis.CONCLUSION:Clinical, radiograph ROM, implant position outcomes, and survival rate at an early-term follow-up of 2.9 years were similar to those reported in recent Cadence studies. However, this study reports 5 unanticipated talar implant fractures and a high rate of posterior radiolucent lines.LEVEL OF EVIDENCE:Level IV, retrospective case series.

Ankle osteoarthritis does not only led to lower ankle power generation, but also results in compensatory gait mechanics at the hip and Chopart joints. Much of previous work explored the relative work distribution after total ankle replacement (TAR) either across the lower extremity joints where the foot was modelled as a single rigid unit or across the intrinsic foot joints without considering the more proximal lower limb joints. Therefore, this study aims, for the first time, to combine 3D kinetic lower limb and foot models together to assess changes in the relative joint work distribution across the foot and lower limb joints during level walking before and after patients undergo TAR. We included both patients and healthy control subjects. All patients underwent a three-dimensional gait analysis before and after surgery. Kinetic lower limb and multi-segment foot models were used to quantify all inter-segmental joint works and their relative contributions to the total lower limb work. Patients demonstrated a significant increase in the relative ankle positive joint work contribution and a significant decrease in the relative Chopart positive joint work contribution after TAR. Furthermore, there exists a large effect toward decreases in the relative contribution of the hip negative joint work after TAR. In conclusion, this study seems to corroborate the theoretical rationale that TAR reduces the compensatory strategy in the Chopart and hip joints in patients suffering from end-stage ankle osteoarthritis.

Ankle osteoarthritis is a chronic debilitating disease marked by cartilage breakdown, pain and significant biomechanical impairment of the entire lower limb. Total ankle replacement (TAR) has been encouraged during the last decade as it has the potential to maintain the existing pre-operative ankle range of motion and to protect the more distally located joints of the foot. Three-dimensional gait analysis using a multi-segment foot model can provide an objective analysis of TAR for the treatment of end-stage ankle osteoarthritis. Thirty-six patients suffering from post-traumatic end-stage ankle osteoarthritis were evaluated before and after TAR. A four-segment kinematic foot model was used to calculate intrinsic foot joint kinematics during gait. Spatio-temporal parameters were also assessed. Kinematic results were compared to a control group of asymptomatic subjects. Differences in waveform patterns were mainly limited to dorsi-/plantarflexion inter-segment angles. At loading response, the Shank-Calcaneus plantarflexion angles as well as the Calcaneus-Midfoot dorsiflexion angle increased slightly in post-operative condition. During propulsion, an increase in Hallux-Metatarsus dorsiflexion angle was observed. Pain improved after surgery as supported by increased spatio-temporal parameters. While multi-segment foot and ankle kinematics were improved, they remained impaired compared to control values. This study confirms that TAR maintains the residual pre-operative range of motion after surgery from midstance to propulsion. Furthermore, the results suggest that the kinematic behavior of the foot joints distal to the affected ankle joint also improves post-operatively. The outcome of this study further emphasizes the clinical relevance of multi-segment foot modeling when assessing the outcome of TAR.

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. Modifications of intrinsic foot joint kinetics after total ankle replacement Alexandre Naaim, Raphaël Dumas, Jean-Luc Besse, Laurence Cheze, Bernhard Devos Bevernage, Thibaut Leemrijse, Paul-André Deleu

Les prothèses totales de cheville (PTC), les arthrodèses tibio-taliennes (TT) et les arthrodèses tibio-talo-calcanéennes (TTC) sont des interventions chirurgicales courantes parfois concurrentes. Les résultats fonctionnels des TTC sont réputés moins bons du fait du double sacrifice articulaire. Les mesures rapportées directement par le patient (« Patient-reported outcome measures (PROMS) » PROMS) ainsi que les scores de satisfaction sont couramment utilisés pour évaluer le résultat de ces chirurgies. Ils ne prennent, cependant, pas en compte la capacité de certains patients à compenser certaines limitations fonctionnelles. L’objectif de notre étude était de comparer les résultats des PTC, des arthrodèses TT et des arthrodèses TTC en se basant sur le ressenti et le point de vue du patient. Nous émettions deux hypothèses : 1) les PTC donnent des résultats supérieurs aux arthrodèses TT ; 2) les arthrodèses TT donnent des résultats supérieurs aux arthrodèses TTC. Nous avons réalisé une étude rétrospective intégrant de manière continue l’ensemble des PTC, des arthrodèses TT et des arthrodèses TTC réalisées dans notre centre de 2010 à 2017. Ces chirurgies étaient comparées à l’aide de PROMS ( Foot Function Index [FFI], Foot and Ankle Outcome Scale [FAOS] et Short Form-12 [SF-12]), d’un score de satisfaction et d’une classification intégrant les possibilités de compensation. Cinquante et un patients ont été inclus dans le groupe PTC, 50 dans le groupe TT et 51 dans le groupe TTC. La durée moyenne de suivi était de 46 ± 20,8 mois. Le groupe PTC présentait de meilleurs résultats que le groupe TT concernant le score FFI et la satisfaction, confirmant ainsi notre première hypothèse. En revanche, aucune différence significative n’était retrouvée entre le groupe TT et le groupe TTC, ce qui infirmait notre deuxième hypothèse. Aucune différence significative entre les groupes n’était retrouvée sur la classification intégrant les possibilités de compensation. Notre hypothèse n’était pas confirmée. En effet les PTC, les arthrodèses TT et les arthrodèses TTC présentaient des résultats sensiblement similaires. Bien qu’il soit difficile de comparer des chirurgies répondant à des indications différentes, il est étonnant de constater que le ressenti des patients, en s’éloignant des résultats cliniques et radiologiques habituels, se montrent relativement proches. IV ; étude rétrospective.

Background: The success of total ankle replacement (TAR) must be based on restoring reasonable mechanical balance with anatomical structures that can produce mechanical joint work through elastic (eg, tendons, fascia) or viscoelastic (eg, heel pad) mechanisms, or by active muscle contractions. Yet, quantifying the work distribution across the affected joint and the neighboring foot joints after TAR is lacking. Therefore, the objective of this study was to investigate if there is a change in the joint work distribution across the Ankle, Chopart, Lisfranc and Metatarsophalangeal joints during level walking before and after patients undergo TAR. Methods: Fifteen patients with end-stage ankle osteoarthritis scheduled for primary TAR for pain relief were recruited and peer-matched with a sample of 15 control subjects. All patients underwent a 3D gait analysis before and after surgery, during which a kinetic multisegment foot model was used to quantify intersegmental joint work. Results: The contribution of the Ankle joint (P = .007) to the total foot and ankle positive work increased significantly after TAR. In contrast, a significant decrease in the contribution to the total foot and ankle joint positive work (P < .001) were found at the Chopart joint after TAR. The foot joints combined produced a significant increase in a net mechanical work from +0.01 J/kg before surgery to +0.05 J/kg after TAR (P = .006). Conclusion: The findings of this study corroborate the theoretical rationale that TAR reduces significantly the compensatory strategy in the Chopart joint in patients with end-stage ankle osteoarthritis after TAR. However, the findings also showed that the contribution of the ankle joint of patients after TAR to the total foot and ankle joint positive work remained impaired compared to the control group.

Introduction: Total ankle arthroplasty (TAA), tibiotalar (TT) arthrodesis and tibiotalocalcaneal (TTC) arthrodesis are common surgical procedures that are sometimes concurrent. The functional results of TTC are deemed to be inferior because of the double joint sacrifice. Patient-Reported Outcome Measures (PROMs), as well as satisfaction scores, are commonly used to assess the outcome of these surgeries, but lack at capturing patients' ability to cope with potential functional limitations. The objective of our study was to compare the results of TAA, TT and TTC arthrodeses according to patients' point of view. We proposed two hypotheses: 1) TAA confer better results than TT arthrodeses, 2) and TT arthrodeses confer better results than TTC arthrodeses, on this specific criterion. Material and methods: We carried out a retrospective study integrating all TAA, TT and TTC arthrodeses performed in our center from 2010 to 2017. These surgeries were compared using PROMs (Foot Function Index (FFI), Foot and Ankle Outcome Scale (FAOS) and 12-Item Short Form Survey (SF-12)), a satisfaction rating and self-reported perceived recovery state. Results: Fifty-one patients were included in the TAA group, 50 in the TT group and 51 in the TTC group. The mean duration of follow-up was 46 +/- 20.8 months. The TAA group had better results than the TT group regarding the FFI score and satisfaction, thus confirming our primary hypothesis. On the other hand, no significant difference was found between the TT group and the TTC group, which invalidated our secondary hypothesis. No significant difference between the groups was found regarding the distribution of patients' perceived recovery state. Conclusion: Our hypothesis was not confirmed. In fact, TAAs, TT and TTC arthrodeses presented substan-tially similar results. Although it is difficult to compare surgeries with different indications, it is surprising to find that the patients' perceived recovery state, deviating from the usual clinical and radiological results, are relatively similar. Level of evidence: IV; Retrospective study. (c) 2022 Elsevier Masson SAS. All rights reserved.

BACKGROUND:Ankle and hindfoot malalignment is a common finding in patients suffering from post-traumatic ankle osteoarthritis. However, no studies have addressed the effect of concomitant foot deformities on intrinsic foot kinematics and kinetics. Therefore, the objective of this study was to investigate the effect of ankle and hindfoot malalignment on the kinematics and kinetics of multiple joints in the foot and ankle complex in patients suffering from post-traumatic ankle osteoarthritis.METHODS:Twenty-nine subjects with post-traumatic ankle osteoarthritis participated in this study. Standardized weight-bearing radiographs were obtained preoperatively to categorize patients as having cavus, planus or neutral ankle and hindfoot alignment, based on 4 X-ray measurements. All patients underwent standard gait assessment. A 4-segment foot model was used to estimate intrinsic foot joint kinematics and kinetics during gait. Statistical parametric mapping was used to compare foot kinematics and kinetics between groups.FINDINGS:There were 3 key findings regarding overall foot function in the 3 groups of post-traumatic ankle osteoarthritis: (i) altered frontal and transverse plane inter-segmental angles and moments of the Shank-Calcaneus and Calcaneus-Midfoot joints in the cavus compared to the planus group; (ii) in cavus OA group, Midfoot-Metatarsus joint abduction sought to compensate the varus inclination of the ankle joint; (iii) there were no significant differences in inter-segmental angles and moments between the planus and neutral OA groups.INTERPRETATION:Future studies should integrate assessment of concomitant foot and ankle deformities in post-traumatic ankle osteoarthritis, to provide additional insight into associated mechanical deficits and compensation mechanisms during gait.

Background: Common etiologies for post-traumatic ankle osteoarthritis are ankle fractures and chronic ankle instability. As the nature of trauma is different for these two etiologies, it might be expected that the two subtypes of post-traumatic ankle osteoarthritis would display different foot mechanics during gait. Research question: The objective of this exploratory cross-sectional study was to compare the foot kinematics and kinetics of patients suffering from post-fracture ankle osteoarthritis with those of patients suffering from postsprain ankle osteoarthritis. Methods: Twenty-nine subjects with end-stage post-traumatic ankle osteoarthritis and fifteen asymptomatic control subjects participated in this study. All patients suffered from post-traumatic ankle osteoarthritis secondary to ankle-related fracture (Group 1; n = 15) or to chronic ankle instability (Group 2; n = 14). A foursegment kinematic and kinetic foot model was used to calculate intrinsic foot joint kinematics and kinetics during gait. Vector field statistical analysis MANOVA was used to assess differences between groups for the entire three-component intrinsic foot joint angles and moments. Results: MANOVA showed significant differences between the groups. Post-hoc analyses suggested that the differences between post-fracture ankle osteoarthritis group and controls were caused by a combination of less adducted Shank-Calcaneus position and less plantarflexion at this joint. Post-hoc analyses also suggested that both pathological groups exhibited a decreased plantarflexion moment for Shank-Calcaneus, Chopart, Lisfranc joints compared to controls. Analyses of both pathological groups versus controls for power suggested lower Shank-Calcaneus and Lisfranc power generation during pre-swing phase. Significance: No significant differences were found between the two pathological groups in this exploratory study. Alterations in foot kinematics and kinetics were mainly found about the dorsi-/plantarflexion axis during the preswing phase of the stance phase for both pathological groups compared to controls. Observed differences were not limited to the painful ankle joint, but seem also to have affected the kinetics of the neighbouring foot joints.

Quasi-stiffness has been used as a parameter revealing the global mechanical behaviour of lower limb joints during locomotion and more particularly that of the ankle. This parameter has been define...

Background: Kinematic and kinetic foot models showed that computing ankle joint angles, moments and power with a one-segment foot modeling approach alters kinematics and tends to overestimate ankle joint power. Nevertheless, gait studies continue to implement one-segment foot models to assess the effect of total ankle replacement. Research question: The objective of this pilot study was to investigate the effect of the foot modeling approach (one-segment versus multi-segment) on how total ankle replacement is estimated to benefit or degrade the patient's biomechanical performance. Methods: Ten subjects with post-traumatic ankle osteoarthritis scheduled for total ankle replacement and 10 asymptomatic subjects were recruited. A one-segment and a multi-segment foot model were used to calculate intrinsic foot joints kinematics and kinetics during gait. A linear mixed model was used to investigate the effect of the foot model on ankle joint kinematic and kinetic analysis and the effect of total ankle replacement. Results: Differences in range of motion due to the foot model effect were significant for all the gait subphases of interest except for midstance. Peak power generation was significantly overestimated when computed with the one-segment foot model. Ankle and shank-calcaneus joint dorsi-/plantarflexion range of motion did not increase post-operatively except during the loading response phase. A significant 'group' effect was found for stance and pre-swing phase range of motion, with total ankle replacement patients showing lower range of motion values than controls for dorsi/plantarflexion. Significance: The outcome of this study showed that the 'foot model' had a significant effect on estimates of range of motion and power generation. The findings in our study therefore emphasize the clinical interest of multi-segment foot modeling when assessing the outcome of a therapeutic intervention.

Background The aim of this systematic review with meta-analysis was to determine the change in gait biomechanics after total ankle replacement and ankle arthrodesis for end-stage osteoarthritis. Methods Electronic databases were searched up until May 2019. Peer-reviewed journal studies including adult participants suffering from end-stage ankle osteoarthritis and reporting pre- and post-operative kinematics, kinetics and spatio-temporal effects of total ankle replacement and ankle arthrodesis during walking were included with a minimum of 12 months follow-up. Seventeen suitable studies were identified and assessed according to methodological and biomechanical qualities. Meta-analysis was performed by calculating the effect size using standard mean differences between pre- and post-operative gait status. Findings Seventeen studies with a total of 883 patients were included. Meta-analysis revealed moderate evidence of an improvement in lower limb kinematics, kinetics and spatio-temporal parameters after total ankle replacement. Moderate evidence indicated an increase in ankle moment, hip range of motion and walking speed after ankle arthrodesis. Interpretation The currently available evidence base of research papers evaluating changes in gait biomechanics after total ankle replacement and ankle arthrodesis is limited by a lack of prospective research, low sample sizes and heterogeneity in the patho-etiology of ankle osteoarthritis. Following total ankle replacement, improvements were demonstrated for spatio-temporal, kinematic and kinetic gait patterns compared to the pre-operative measures. Improvements in gait mechanics after ankle arthrodesis were limited to walking speed and ankle moment. Increased hip range of motion after ankle arthrodesis could represent a sign of compensation for the lack of ankle motion.

This study evaluated the 3D angle between the joint moment and the joint angular velocity vectors at the intrinsic foot joints, and investigated if these joints are predominantly driven or stabilized during gait. The participants were 20 asymptomatic subjects. A four-segment kinetic foot model was used to calculate and estimate intrinsic foot joint moments, powers and angular velocities during gait. 3D angles between the joint moment and the joint angular velocity vectors were calculated for the intrinsic foot joints defined as follows: ankle joint motion described between the foot and the shank for the one-segment foot model (hereafter referred as Ankle), and between the calcaneus and the shank for the multi-segment foot model (hereafter referred as Shank-Calcaneus); joint motion described between calcaneus and midfoot segments (hereafter referred as Chopart joint); joint motion described between midfoot and metatarsus segments (hereafter referred as Lisfranc joint); joint motion described between first phalanx and first metatarsal (hereafter referred as First Metatarso-Phalangeal joint). When the vectors were approximately aligned, the moment was considered to result in propulsion (3D angle <60o) or resistance (3D angle >120o) at the joint. When the vectors are approximately orthogonal (3D angle close to 90°), the moment was considered to stabilize the joint. The results showed that the four intrinsic joints of the foot are never fully propelling, resisting or being stabilized, but are instead subject to a combination of stabilization with propulsion or resistance during the majority of the stance phase of gait. However, the results also show that during pre-swing all four the joints are subject to moments that result purely in propulsion. At heel off, the propulsive configuration appears for the Lisfranc joint first at terminal stance, then for the other foot joints at pre-swing in the following order: Ankle, Chopart joint and First Metatarso-Phalangeal joint. Intrinsic foot joints adopt a stabilized-resistive configuration during the majority of the stance phase, with the exception of pre-swing during which all joints were found to adopt a propulsive configuration. The notion of stabilization, resistance and propulsion should be further investigated in subjects with foot and ankle disorders.