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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.

Femorotibial alignment is crucial for the outcome of unicompartmental knee arthroplasty (UKA). Robotic-assisted systems are useful to increase the accuracy of alignment in UKA. However, no study has assessed if the femorotibial alignment measured by the image-free robotic system is reliable. The aim of this study was to determine whether measurement of the mechanical femorotibial axis (mFTA) in the coronal plane with handheld robotic assistance during surgery is equivalent to a static measurement on radiographs and to a dynamic measurement during walking. Twenty patients scheduled for robotic-assisted medial UKA using handheld technology were included in this prospective study. Three measurements of the frontal femorotibial axis were compared: intra-operative acquisition by computer assistance (dynamic, non-weightbearing position), radiographic measurements on long leg X-ray (static, weightbearing position), and by gait analysis during walking (dynamic, weightbearing position). There was no significant difference in the mFTA between computer (174.4 ± 3.4°), radiological (173.9 ± 3.3°), and gait analysis (172.9 ± 5.1°) measurements (p = 0.5). There was a strong positive correlation (r = 0.6577355, p = 0.0016) between robotic-assisted measurements and gait analysis. There was no significant difference in the femorotibial axis measured by the image-free robotic assistance, from the preoperative radiographs or by gait analysis. The reliability of intra-operative measurements of the frontal femorotibial axis by these robotic-assisted systems is acceptable.

There are increased surgical considerations when revising total knee arthroplasty (TKA) in active patients. Few studies have assessed if a semi-constrained [Total Stabilized (TS)] prostheses has similar knee biomechanics to a primary posterior stabilized (PS) prosthesis. The aim was to compare the gait parameters in patients with PS or TS TKA and normal controls. 32 patients with TKA were prospectively included with either a primary PS (n = 15) or a revision TS (n = 17) prosthesis. Gait analysis was performed at 6 months postoperatively for each patient, with an optoelectronic knee assessment device (KneeKG®) assessing the displacement of the tibia relative to the femur during the different gait phases (flexion/extension, anterior/posterior translation, adduction/abduction, internal/external rotation). A control group (n = 12) of healthy knees was compared with the TKA groups. There were no significant kinematic differences between PS and TS groups. The maximum knee flexion during gait was 53° ± 8.1° in the PS group vs 52° ± 8.7° in the TS group. The antero-posterior translation was similar in both group (2.3 ± 0.5 mm vs 2.6 ± 0.9 mm, respectively). Peak varus angle during loading and swing phase was slightly higher in the TS group (2.7° ± 0.7° and 5.2° ± 0.9°) than in the PS group (2.9° ± 0.6° and 5.6° ± 1.2°), without significant difference. The ranges in internal/external rotation were similar between PS and TS TKA (3.7° ± 0.5° vs 3.3° ± 0.6°, respectively). Both designs approached closely the normal gait patterns of the control group except in the frontal plane. Single radius TS TKA has gait parameters similar to single radius PS TKA. Use of a single radius TS TKA in revision TKA is not detrimental to a patient’s gait pattern. Both designs approached closely the normal gait patterns of the control group. Prospective, case–control study; Level III.

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 post-sprain 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 four-segment 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 pre-swing 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.

In recent studies, robotic-assisted surgical techniques for unicompartmental knee arthroplasty (UKA) have demonstrated superior implant positioning and limb alignment compared to a conventional technique. However, the impact of the robotic-assisted technique on clinical and functional outcomes is less clear. The aim of this study was to compare the gait parameters of UKA performed with conventional and image-free robotic-assisted techniques. This prospective, single-center study included 66 medial UKA, randomized to a robotic-assisted (n = 33) or conventional technique (n = 33). Gait knee kinematics was assessed on a treadmill at 6 months to identify changes in gait characteristics (walking speed, each degree-of-freedom: flexion–extension, abduction–adduction, internal–external rotation, and anterior–posterior displacement). Clinical results were assessed at 6 months using the IKS score and the Forgotten Joint Score. Implants position was assessed on post-operative radiographs. Post-operatively, the whole gait cycle was not significantly different between groups. In both groups, there was a significant improvement in varus deformity between the pre- and post-operative gait cycle. There was no significant difference between the two groups in clinical scores, implant position, revision, and complication rates. No difference of gait parameters could be identified between medial UKA performed with image-free robotic-assisted technique or with conventional technique. Prospective randomized controlled trial. Level of evidence I.

Background Tools for functional assessment of chronic low back pain (LBP) are lacking. Objective To determine the correlations and the responsiveness of the 400 m comfortable walk test (400 mCWT) and the 200 m fast-walk test (200 mFWT) in the functional assessment of a multimodal program. Methods One hundred and twenty-seven participants (68 females) with LBP and with or without radicular pain completed a Quebec Back Pain Disability Scale, a Sorensen test, a Shirado test, a 400 mCWT and a 200 mFWT, at baseline and at the end of the program. Results No significant side effect was reported during walk tests. Walking speed was significantly increased after the program (0.18 ± 0.15 m.s-1 for the 400 mCWT and 0.17 ± 0.17 m.s-1 for the 200 mFWT). Clinical parameters were also significantly improved (82.02 ± 83.1 seconds for the Shirado, 92.1 ± 100.1 seconds for the Sorensen, -14.0 ± 12.9 for the Quebec scale). A significant relationship was found between the increase in walking speed for the two walk tests and the improvement of the Quebec scale. The gait speed improvement was close to the minimal clinically important change (95% confidence interval: 0.14-0.22) determined from the Quebec scale threshold (minimum detectable change). Conclusions Both 400 mCWT and 200 mFWT are correlated with functional parameters and are responsive for the functional assessment of LBP.

Background 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. Methods 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 o) 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. Results 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. Conclusions 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.

To validate the use of an innovative navigation method for sacrospinous fixation in surgery-like conditions as a new teaching tool and surgical method.Two-month experimental prospective pilot study between July and August 2021.Biomechanics laboratory academic research.A total of 29 participants took part in the study: 9 gynecological surgeons and 20 participants with no medical background.All participants used the 2 mocks-up.The experiment was composed of 2 training phases dedicated to improving the hand-eye coordination and suture skills on a training mock-up and of a suturing phase on a pelvic mock-up designed to recreate the surgery-like conditions of a sacrospinous fixation. The surgeons provided qualitative feedback on the bio-accuracy of the mock-ups and evaluated the ease of use of the navigation software. Nonsurgeons were included to assess the progression of the suture performance between 2 experiments performed 1 week apart (session 1 and 2). The main objective for participants was to reach a virtual target and to stitch sacrospinous ligaments. For session 1, an overall comfort score of 7.2 of 10 was attributed to the tool; 14 (42%) surgeon suture attempts and 63 (65%) nonsurgeon suture attempts were accurate (i.e., below the 5-mm threshold). Twenty-two (67%) surgeon suture attempts and 28 (34%) nonsurgeon suture attempts were fast (i.e., in the first 2 quantiles of the duration dataset). An improvement in the nonsurgeon performance was observed between the 2 sessions in terms of duration (session 1: 46 ± 20 s; session 2: 37 ± 18 s; p = .047) and distance (session 1: 3.8 ± 1.3 mm; session 2: 3.2 ± 1.4 mm; p = 10This new motion capture-based navigation method for sacrospinous fixation tested under surgery-like conditions seemed to be accurate and effective. The next step will be to design a pelvis model more adapted to the constraints of a sacrospinous fixation and to validate the benefits of this method compared with current techniques.

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.

International audience; The Dual Mobility Cup (DMC) was created in 1974 to prevent dislocation and decrease wear. However, the movement of the polyethylene liner in vivo remains unclear. The aims of this study were to visualise liner positions and quantify the accuracy of the liner plane orientation for static positions, using ultrasound imaging. DMC reconstruction and angle between cup and liner were evaluated on isolated submerged DMCs by comparing 3D laser scans and ultrasound imaging. Moreover, the abduction and anteversion angles of the liner plane relative to the pelvis orientation were calculated via combined motion analysis and 3D ultrasound imaging on four fresh post-mortem human subjects with implanted DMC. On submerged DMC, the mean angle error between ultrasound imaging and 3D scan was 1.2°. In cadaveric experiments, intra-operator repeatability proved satisfactory, with low range value (lower than 2°) and standard deviation (lower than 1°). The study demonstrates the feasibility of measuring liner orientation on submerged and ex vivo experiments using ultrasound imaging, and is a first step towards in vivo analysis of DMC movement.

In recent studies, robotic-assisted surgical techniques for unicompartmental knee arthroplasty (UKA) have demonstrated superior implant positioning and limb alignment compared to a conventional technique. However, the impact of the robotic-assisted technique on clinical and functional outcomes is less clear. The aim of this study was to compare the gait parameters of UKA performed with conventional and image-free robotic-assisted techniques.This prospective, single-center study included 66 medial UKA, randomized to a robotic-assisted (n = 33) or conventional technique (n = 33). Gait knee kinematics was assessed on a treadmill at 6 months to identify changes in gait characteristics (walking speed, each degree-of-freedom: flexion-extension, abduction-adduction, internal-external rotation, and anterior-posterior displacement). Clinical results were assessed at 6 months using the IKS score and the Forgotten Joint Score. Implants position was assessed on post-operative radiographs.Post-operatively, the whole gait cycle was not significantly different between groups. In both groups, there was a significant improvement in varus deformity between the pre- and post-operative gait cycle. There was no significant difference between the two groups in clinical scores, implant position, revision, and complication rates.No difference of gait parameters could be identified between medial UKA performed with image-free robotic-assisted technique or with conventional technique.Prospective randomized controlled trial. Level of evidence I.

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.

Femorotibial alignment is crucial for the outcome of unicompartmental knee arthroplasty (UKA). Robotic-assisted systems are useful to increase the accuracy of alignment in UKA. However, no study has assessed if the femorotibial alignment measured by the image-free robotic system is reliable. The aim of this study was to determine whether measurement of the mechanical femorotibial axis (mFTA) in the coronal plane with handheld robotic assistance during surgery is equivalent to a static measurement on radiographs and to a dynamic measurement during walking.Twenty patients scheduled for robotic-assisted medial UKA using handheld technology were included in this prospective study. Three measurements of the frontal femorotibial axis were compared: intra-operative acquisition by computer assistance (dynamic, non-weightbearing position), radiographic measurements on long leg X-ray (static, weightbearing position), and by gait analysis during walking (dynamic, weightbearing position).There was no significant difference in the mFTA between computer (174.4 ± 3.4°), radiological (173.9 ± 3.3°), and gait analysis (172.9 ± 5.1°) measurements (p = 0.5). There was a strong positive correlation (r = 0.6577355, p = 0.0016) between robotic-assisted measurements and gait analysis.There was no significant difference in the femorotibial axis measured by the image-free robotic assistance, from the preoperative radiographs or by gait analysis. The reliability of intra-operative measurements of the frontal femorotibial axis by these robotic-assisted systems is acceptable.

45e Congrès de la Société de Biomécanique, Metz, FRANCE, 26-/10/2020 - 28/10/2020; Possible lack of length or over-stiffness of soft tissues may explain some musculo-skeletal disorders. Certain extra length of soft tissues can be recovered by releasing some strain with pie-crusting technique. This technique can be applied to the tendons (Burge et al., 2014), the ligaments (He et al., 2018), or the fascias (C?atal et al., 2019). It is widely used when patients having a too short and too stiff iliotibial band (ITB), suffer from unstable knee, joint line elevation, etc. For example, in valgus knees, ITB is tensed on the lateral side and the main technique used to correct valgus deformity is to perform a pie-crusting technique to release the ITB. However, soft tissue releasing using the pie-crusting technique is challenging as too extensive releases may lead to complications. The aim of this preliminary study is to assess the level of strain release of the ITB using pie-crusting technique in view of assessing quantitatively the impact of this surgery on the strain release.

SB'20, 45ème Congrès de la Société de Biomécanique, Metz, France, 26-/10/2020 - 28/10/2020; The aim of this study was to calculate, for an asymptomatic healthy population, the quasi-stiffness of the intrinsic foot joints during mid-stance. This phase is characterised by a single leg support with low propulsion as it occurs before heel-off and by a presumed major contribution of the passive foot structures.

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 12months 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.

44e Congrès de la Société de Biomécanique, Poitiers, France, 28-/10/2019 - 30/10/2019; Fascia is a fibrous connective tissue present all over the body. This study focuses on the deep fascia that is overlying muscles of the outer thigh. Indeed, fascia lata is involved in various pathologies, such as iliotibial band syndrome, inflammatory lesions, traumatic injuries etc. (Huang et al. 2013). This fascia has a sheathing effect on muscles and a stabiliser effect on the knee and hip joints during movements (Eng et al. 2014); however, these sheathing and stabiliser effects have not been quantified yet. Skin is connected to the muscle via fascia and adipose tissues. It also plays a role of sheath on underlying tissues. Thus, body movements cause the stretching of all these tissues. To unserstand what are the involed mechanical phenomena in these tissues and how they interact, the objective of this study is to look at superfical strain fields of the skin and deep fascia of the thigh during knee flexion extension movements.

Soft tissue artefact (STA), i.e. the motion of the skin, fat and muscles gliding on the underlying bone, may lead to a marker position error reaching up to 8.7cm for the particular case of the scapula. Multibody kinematics optimisation (MKO) is one of the most efficient approaches used to reduce STA. It consists in minimising the distance between the positions of experimental markers on a subject skin and the simulated positions of the same markers embedded on a kinematic model. However, the efficiency of MKO directly relies on the chosen kinematic model. This paper proposes an overview of the different upper limb models available in the literature and a discussion about their applicability to MKO. The advantages of each joint model with respect to its biofidelity to functional anatomy are detailed both for the shoulder and the forearm areas. Models capabilities of personalisation and of adaptation to pathological cases are also discussed. Concerning model efficiency in terms of STA reduction in MKO algorithms, a lack of quantitative assessment in the literature is noted. In priority, future studies should concern the evaluation and quantification of STA reduction depending on upper limb joint constraints.

Soft tissue artefacts (STA) introduce errors in joint kinematics when using cutaneous markers, especially on the scapula. Both segmental optimisation and multibody kinematics optimisation (MKO) algorithms have been developed to improve kinematics estimates. MKO based on a chain model with joint constraints avoids apparent joint dislocation but is sensitive to the biofidelity of chosen joint constraints. Since no recommendation exists for the scapula, our objective was to determine the best models to accurately estimate its kinematics. One participant was equipped with skin markers and with an intracortical pin screwed in the scapula. Segmental optimisation and MKO for 24-chain models (including four variations of the scapulothoracic joint) were compared against the pin-derived kinematics using root mean square error (RMSE) on Cardan angles. Segmental optimisation led to an accurate scapula kinematics (1.1° ≤ RMSE ≤ 3.3°) even for high arm elevation angles. When MKO was applied, no clinically significant difference was found between the different scapulothoracic models (0.9° ≤ RMSE ≤ 4.1°) except when a free scapulothoracic joint was modelled (1.9° ≤ RMSE ≤ 9.6°). To conclude, using MKO as a STA correction method was not more accurate than segmental optimisation for estimating scapula kinematics.

Background Obtaining precise and repeatable measurements is essential to clinical gait analysis. However, defining the thigh medial-lateral axis segment remains a challenge, with particular implications for the hip rotation profile. Thigh medial-lateral axis misalignment modifies the hip rotation profile and can result in a phenomenon called crosstalk, which increases knee adduction-abduction amplitude artificially. Research question This study proposes an a posteriori geometrical method based solely on segment anatomy that aims to correct the thigh medial-lateral axis definition and crosstalk-related error. Methods The proposed method considers the thigh medial-lateral axis as the normal to the mean sagittal plane of the lower limb defined by hip, knee and ankle joint centres during one gait cycle. Its performance was compared to that of an optimisation method which repositions the axis to reduce knee abduction-adduction variance. An existing dataset was used: 75 patients with a knee prosthesis undergoing gait analysis three months and one-year post-surgery. Three-dimensional hip and knee angles were computed for two gait analysis sessions. Crosstalk was quantified using both the coefficient of determination (r²) between knee flexion-extension and adduction-abduction and the amplitude of knee adduction-abduction. The reproducibility of hip internal-external rotation was also quantified using the inter-trial, inter-session and inter-subject standard deviations and the intraclass coefficient (ICC). Results Crosstalk was significantly reduced from r² = 0.67 to r² = 0.51 by the geometrical method but remained significantly higher than with the optimisation method with a r² Significances Both methods allowed to improve the hip internal-external reproducibility from poor to moderate (original data: ICC = 0.34, geometrical method: ICC = 0.65, optimisation method ICC = 0.73). One advantage of the geometrical method is that, unlike the optimisation method, it does not require much movement, making it suitable for a wider range of patients.

Assessing the functional ability depending on the prosthesis fitting of individuals with transfemoral amputation (TFA) is critical for overall rehabilitation and prosthetic care. Gait analysis could provide an overwhelming number of biomechanical parameters. We argue that margins of stability (MoS) could be critical indicators of TFA’s control strategy. A study revealed statistically larger MoS on the prosthetic limb when comparing medial-lateral MoS for six TFAs fitted with a socket-suspended prostheses and six able- bodied during treadmill walking (Hof et al. 2007). Another study showed limited and non-significant differences when comparing anterior-posterior MoS for ten TFA fitted with mechanical and microprocessor-controlled knees during walking overground (Prinsen et al. 2017). There is a need to report MoS more widely, particularly for TFA fitted with bone-anchored prosthesis as osseoperception should improve control. A single case study demonstrated that the load applied by bone-anchored prosthesis fitted with microprocessor-controlled was attenuated by 10-20% compared to mechanical knee (Frossard et al. 2013). However, the impact of these loading differences on the overall gait pattern, including medial-lateral MoS, remains unknown.

Background Although the initial anaerobic component of exercise adaptation is unavoidable, no specific functional test is available for use in routine non-sporting practice to evaluate it. Objective To assess the bioenergetic and biomechanical properties of the Short and Fast Step Test (SFST), which consists of walking up and down a step as many times as possible in 1 minute and to analyse its ability to explore the initial anaerobic component of effort in comparison to a reference self-paced step test. Methods Overall, 31 healthy subjects (19 women; mean [SD] age, 32.4 [10.2] years) completed a test–retest of a self-paced step test and the SFST, with pre- and post-test measurement of blood lactate concentration and continuous recording of VO2 and modelling of excess post-exercise oxygen consumption (EPOC), near-infrared spectroscopy (NIRS) of the quadriceps and mechanical power (estimated by the number of steps climbed and 3-D motion analysis). Results Both step tests were well tolerated. The reliability of the bioenergetics parameters, number of raised steps, mechanical power and NIRS tissue saturation index was good. Indirect mechanical power (estimated from number of steps) was correlated with direct power (computed from the centre of mass). Lactate accumulation was significantly increased during exercise with only the SFST (mean [SD] increase, 3.86 [3.26] mmol L−1 from resting values, P Conclusions SFST is feasible, well tolerated, reliable and responsive to explore a brief exercise involving anaerobic metabolism at submaximal intensity. The number of steps taken in 1 minute seems a suitable parameter for practical application.

International audience

International audience; ObjectivesThere is ambiguity concerning the walk tests available for functional assessment of coronary patients, particularly for the walking speed. This study explores the psychometric properties of two walking tests, based on fixed-distance tests, at comfortable and fast velocity, in stabilized patients at the end of a cardiac rehabilitation program.MethodsAt a three-day interval 58 coronary patients (mean age of 64.85 ± 6.03 years, 50 men) performed three walk tests, the first two at a comfortable speed in a random order (6-minute walk test – 6MWT – and 400-metre comfortable walk test – 400mCWT) and the third at a brisk speed (200-metre fast walk test – 200mFWT). A modified Bruce treadmill test was associated at the end of the second phase. Monitored main parameters were: heart rate, walking velocity, VO2.ResultsTolerance to the 3 tests was satisfactory. The reliability of the main parameters was good (intraclass correlation coefficient > 0.8). The VO2 concerning 6MWT and 400mCWT were not significantly different (P = 0.33) and were lower to the first ventilatory threshold determined by the stress test (P < 0.001): 16.2 ± 3.0 vs. 16.5 ± 2.6 vs. 20.7 ± 5.1 mL·min−1·kg−1 respectively. The VO2 of the 200mFWT (20.2 ± 3.7) was not different from the first ventilatory threshold.Conclusions400mCWT and 200mFWT are feasible, well-tolerated and reliable. They explore two levels of effort intensity (lower and not different to the first ventilatory threshold respectively). 400mCWT is a possible alternative to 6MWT. Associated with 200mFWT it should allow a better measurement of physical capacities and better customization of exercise training.

40ème congrès de la Société de Biomécanique, PARIS, FRANCE, 28-/10/2015 - 30/10/2015; Soft tissue artefact (STA) is one of the most important limitations when studying human movement through marker-based motion capture techniques. Indeed, the relative movement between the reflective skin markers and the underlying bones introduce errors in bone kinematics. Upper limb kinematics is particularly affected by STA, especially when studying scapula. As a result, there is a need for correction in order to use, with confidence, this technique in clinical environments. Different compensation or correction methods exist, such as multibody optimisation (MBO). Using MBO, the studied limb is represented as a kinematic chain composed of rigid segments linked by mechanical joints. The position and orientation of each segment are then optimised under kinematic and rigid body constraints in order to minimise the sum of the squared distances between measured and model-determined markers positions. It has been shown that the correction obtained depends on the joint model and that anatomical- based models are better suited to reach physiological results. The aim of the study was thus to define and validate different upper limb joint models used in a MBO framework focusing on the definition of an anatomical-based scapulothoracic joint.

Introduction Coordination between shoulder and pelvis girdles during walking is pivotal to optimise a stable forward displacement (Lamoth and van Heuvelen, 2012). Hip osteoarthritis (HOA) increases the stiffness of the pelvis and the low back and should impair this coordination. To our knowledge, no study evaluates this outcome for HOA. The aim was to evaluate the psychometric properties of the pelvis-shoulder coordination in healthy (HEA) and non-severe unilateral HOA subjects. Material and methods HEA and HOA subjects were enrolled. Each participant performed a 3D gait analysis along a 6-metre walkway using an optoelectronic system with 8 cameras (100 Hz). HOA performed a second session to evaluate measurement's reliability (test-retest). Pelvis and shoulder yaws (transverse plane) and rolls (frontal plane) were calculated using markers positioned on the acromial process and the anterior-superior iliac spines. The phase-lag between angle waveforms expressed as a gait cycle's percentage was computed using continuous estimate of relative phase (CRP; Russell Esposito and Wilken, 2014). Intraclass correlation (ICC), one-way Anova and Pearson correlation coefficient were used to evaluate respectively, reliability, responsiveness and validity (against HOOS scores; Ornetti et al., 2009). Results Seventy-eight HEA (58.4 ± 15.4 years) and 103 HOA (61.0 ± 8.1 years) subjects were included. ICC were excellent for roll-lag (0.918) and yaw-lag (0.959). Significant difference was found for roll-lag between subjects (HEA 37.8 ± 10.6%; OA 29.5 ± 9.8%, P r > 0.24, P r = −0.27, P = 0.013 for Lesquene index). Discussion–conclusion Pelvis-shoulder coordination outcomes showed excellent reliability. Roll-lag was related to clinical scores whereas yaw-lag did not. As only non-severe patients were included, these outcomes need to be addressed in population with higher impairment. It could be then proposed as an objective outcome to evaluate deficit in hip osteoarthritis patients.

En pratique clinique, il est courant de comparer les resultats d’une analyse quantifiee de la marche de patients presentant des troubles de la marche a une population asymptomatique. Cependant, les vitesses de marche sont generalement differentes et plusieurs etudes ont montre que cela pouvait engendrer des repercussions sur l’interpretation des parametres cinematiques, cinetiques, spatio-temporaux et des patterns electromyographiques. Le but de cette etude etait d’etudier si la vitesse de marche pouvait egalement avoir une influence sur les strategies de stabilisation de la tete au cours de la marche chez une population asymptomatique. Les resultats obtenus sont coherents avec la litterature a vitesse spontanee et suggerent l’apparition d’une strategie en bloc dans les plans sagittal et transversal pour des vitesses lentes.