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article describes a method used to calibrate 3-D freehand ultrasound systems based on phantoms with parallel wires forming two perpendicular planes, such as the usual general-purpose commercial phantoms. In our algorithm, the phantom pose is co-optimized with the calibration to avoid the need to precisely track the phantom. We provide a geometrical analysis to explain the proposed acquisition protocol. Finally, we give an estimate of the system accuracy and precision based on measurements acquired on an independent test phantom. We obtained error norms of 1.6 mm up to 6 cm of depth and 3.5 mm between 6 and 14 cm of depth, in total average. In conclusion, it is possible to calibrate ultrasound tracked-probe systems with a reasonable accuracy based on a general-purpose phantom. Contrarily to most calibration methods that imply the construction of the phantom, the present algorithm is based on a standard phantom geometry that is commercially available. (E-mail: sandra. marcadent@epfl.ch) (c) 2022 World Federation for Ultrasound in Medicine & Biology. All rights reserved.

While a causal relationship between pain-related fear and spinal movement avoidance in patients with chronic low back pain (CLBP) has frequently been postulated, evidence supporting this relationship is limited. This study aimed to test if decreases in pain-related fear or catastrophizing were associated with improvements in spinal biomechanics, accounting for possible changes in movement-evoked pain. Sixty-two patients with CLBP were assessed before and after an interdisciplinary rehabilitation program (IRP). Pain-related fear was assessed with general and task-specific measures. Lower and upper lumbar angular amplitude and velocity as well as paraspinal muscle activity were recorded during five daily-life tasks to evaluate spinal biomechanics. Relationships were tested with multivariable linear regression analyses. The large decreases in pain-related fear and catastrophizing following the IRP were scarcely and inconsistently associated with changes in spinal biomechanics (< 3% of the models reported a statistically significant association). Results remained comparable for activities inducing more or less fear, for specific or general measures of pain-related fear, and for analyses performed on the entire population or limited to subgroups of patients with higher levels of task-specific fear. In contrast, reductions in task-specific pain-related fear were significantly associated with decreases in movement-evoked pain in all tasks (r = 0.26-0.62, p ≤ 0.02). This study does not support an association between pain-related fear and spinal movement avoidance. However, it provides evidence supporting a direct relationship between decreased pain-related fear and decreased movement-evoked pain, possibly explaining some mechanisms of the rehabilitation programs.

Objective To study the prevalence of suprapatellar fat pad (SPFP) MR alterations in asymptomatic subjects, in relation to a wide range of clinical/imaging parameters, including muscle performance tests and physical activity data. Materials and methods We prospectively included 110 asymptomatic subjects as part of a cohort study. Inclusion criteria were no knee pain in the last year. Exclusion criteria were any medical/surgical history of a knee disorder. Subjects underwent knee and low-dose posture radiographs [EOS®], 3 T MRI, clinical examination including muscle performance tests, and physical activity monitoring. The presence/absence of SPFP alterations (hyperintensity and mass effect) were assessed through consensus reading on fluid-sensitive sequences. Differences between groups of knees with SPFP alterations and controls were tested for a total of 55 categorical/continuous clinical/imaging parameters, including SPFP relative-T2-signal, trochlear/patellar/lower-limb morphologic measurements. Wilcoxon-rank-sum and chi-square tests were used to compare groups of patients. The histological correlation was obtained in a cadaveric specimen. Results SPFP alterations were common in asymptomatic subjects: hyperintensity 57% (63/110) and mass effect 37% (41/110), with 27% (30/110) showing both. Among the 55 imaging, clinical, or activity parameters tested, only increased patellar tilt angle (p = 0.02) and TT-TG distance (p = 0.03) were statistically different between groups of SPFP alterations and controls. The histological correlation showed more abundant connective tissue in SPFP compared to the prefemoral fat pad. Conclusions SPFP hyperintensity and mass effect are common MRI findings in asymptomatic knees, and they are not related to most imaging, clinical, and activity parameters. Care should be taken not to overcall them pathological findings as they most likely represent normal variants.

introduction: there is lack of understanding of the relationship between knee adduction moment (KaM) reductions and improvements in pain or function in patients with knee osteoarthritis (Koa). Moreover, there is no systematic review describing the longitudinal relationship between KaM changes and subsequent changes in pain and/or physical function. We aimed to: 1) investigate the relationship between changes in KaM induced by non-surgical biomechanical interventions and consecutive changes in pain and/or physical function in patients with medial Koa and; 2) compare this relationship for different interventions. EVidEncE acQuisition: We considered eligible all rcts using biomechanical interventions aimed to reduce KaM in Koa patients, that measured pain/function. We used cohen’s d effect size to quantify outcome measurements. EVIDENCE SYNTHESIS: Fourteen papers reporting 11 studies were identified. Braces were tested in 6 studies, insoles in 5 studies, shoes in 3 studies and gait retraining in 2 studies. Methodological differences were large among studies. Large effect sizes (≥0.8) changes in pain/function were observed with interventions having at least a small KAM effect size (≥0.2), suggesting an association between KAM and pain/function changes. A linear trend was observed between inter-intervention KAM and VAS pain effect sizes, based on 4 studies. No firm conclusions could be drawn for the different intervention types. conclusions: there was a trend toward larger KaM reductions leading to larger improvements in pain/function in non-surgical biomechanical interventions. additional high-quality rct with consistent methodology are needed to fully characterize the association between KaM and pain/function changes.

Purpose There is a paucity of data available on total knee prostheses combining dual-radius, ultra-congruency, posterior-stabilization and mobile-bearing insert. This prospective cohort study aimed to assess the clinical evolution of the FIRST® prosthesis (Symbios Orthopédie, Yverdon, CH), the earliest prosthesis with this particular design. It was hypothesized that the primary outcomes, evaluating pain, stiffness, function and stability, would improve following arthroplasty and remain improved during the follow-up period of 10 years. Methods All patients programmed for a total knee arthroplasty using a FIRST® prosthesis at our university hospital between 2006 and 2008 were invited to participate. Study knees were evaluated pre-operatively as well as one, five and ten years post-operatively. Patients filled out questionnaires at each evaluation point and had a radiographic assessment at the five-year and ten-year follow-ups. Primary outcomes were the total, pain, stiffness and function measures of the Western Ontario and McMaster Universities Osteoarthritis questionnaire (WOMAC) and the knee and function measures of the Knee Society Score (KSS). Friedman and Wilcoxon’s rank-sum tests were used to compare measures across time points. Results Hundred and twenty four prostheses were included (baseline demographics: 69.9 ± 8.3 years old, 28.1 ± 4.3 kg/m2, 54% male) and 68 could be followed during ten years. Five prostheses underwent a revision. All other prostheses lost at follow-up were lost for reasons unrelated to the prosthesis. All primary measures reported statistically and clinically significant improvements between baseline and the three follow-up evaluations. Statistically significant improvements at the three follow-up evaluations were also observed for most secondary measures. There was no implant loosening. At ten-year follow-up, radiolucent lines were observed in 2.9% femoral implants and 1.5% tibial implants. Conclusion The positive results observed in all domains of assessment and the small revision rate demonstrated an effective functioning of the FIRST® prosthesis during the ten-year follow-up period. The results, globally similar to those previously published for other prosthesis designs, encourage the development of assistive methods to select the most appropriate designs on an individual basis. Level of evidence IV, prospective cohort study.

Objective To estimate the prevalence of acetabular rim ossifications in the adult population with asymptomatic, morphologically normal hips at CT and to determine whether the presence of these ossifications is associated with patient- or hip-related parameters. Methods We prospectively included all patients undergoing thoracoabdominal CT over a 3-month period. After exclusion of patients with a clinical history of hip pathology and/or with signs of osteoarthritis on CT, we included a total of 150 hips from 75 patients. We analyzed the presence and the size of ossifications around the acetabular rim. The relationships between the size of acetabular rim ossifications and patient-related (sex, age, BMI) or hip-related parameters (joint space width, and cam- and pincer-type femoroacetabular impingement morphology) were tested using multiple regression analysis. Results The prevalence of acetabular rim ossifications in this population of asymptomatic, non-osteoarthritic hips was 96% (95% CI = [80.1; 100.0]). The presence of ossifications and their size were correlated between the right and left hips (Spearman coefficient = 0.64 (95% CI = [0.46;0.79]), p < 0.05)). The size of acetabular rim ossifications was significantly associated with age (p < 0.0001) but not with BMI (p = 0.35), gender (p = 0.05), joint space width (p ≥ 0.53 for all locations), or any of the qualitative or quantitative parameters associated with femoroacetabular morphology (p ≥ 0.34). Conclusion Acetabular rim ossifications are highly prevalent in asymptomatic, non-osteoarthritic adult hips at all ages. Their size is not correlated with any patient- or hip-related parameters except for age. These findings suggest that ossifications at the acetabular rim, when present in isolation, should not be considered a sign of osteoarthritis or femoroacetabular impingement morphology. Key Points • Acetabular rim ossifications are extremely common in asymptomatic, non-osteoarthritic adult hips. • Acetabular rim ossifications are present independently from other signs of osteoarthritis in adult hips at all ages and should not be interpreted as a pathological finding. • The diagnosis of osteoarthritis or femoroacetabular impingement morphology should not be made based on the sole presence of ossifications at the acetabular rim.

Using insoles to modify walking biomechanics is of keen interest for the treatment of medial-compartment knee osteoarthritis. So far, insole interventions have focused on reducing the peak of the knee adduction moment (pKAM) and have led to inconsistent clinical outcomes. This study aimed to evaluate the changes in other gait variables related to knee osteoarthritis when patients walk with different insoles to provide insights into the necessity to enlarge the biomechanical analyses to other variables. Walking trials were recorded for 10 patients in four insole conditions. Changes among conditions were computed for six gait variables, including the pKAM. The associations between the changes in pKAM and the changes in the other variables were also assessed individually. Walking with different insoles had noticeable effects on the six gait variables, with high heterogeneity among patients. For all variables, at least 36.67% of the changes were of medium-to-large effect size. The associations with the changes in pKAM varied among variables and patients. In conclusion, this study showed that varying the insole could globally influence ambulatory biomechanics and that limiting measurement to the pKAM could lead to an important loss of information. Beyond the consideration of additional gait variables, this study also encourages personalized interventions to address inter-patient variability.

This meta-analysis investigated whether more negative psychological factors are associated with less spinal amplitude of movement and higher trunk muscle activity in individuals with low back pain. Furthermore, it examined whether pain intensity was a confounding factor in this relationship. We included studies that provided at least 1 correlation coefficient between psychological (pain-related fear, catastrophizing, depression, anxiety, and self-efficacy) and spinal motor behaviour (spinal amplitude and trunk muscle activity) measures. In total, 52 studies (3949 participants) were included. The pooled correlation coefficients (95% confidence interval; number of participants) were -0.13 (-0.18 to -0.09; 2832) for pain-related fear, -0.16 (-0.23 to -0.09; 756) for catastrophizing, -0.08 (-0.13 to -0.03; 1570) for depression, -0.08 (-0.30 to 0.14; 336) for anxiety, and -0.06 (-0.46 to 0.36; 66) for self-efficacy. The results indicated that higher levels of pain-related fear, catastrophizing, and depression are significantly associated with reduced amplitudes of movement and larger muscle activity and were consistent across subgroup and moderation analyses. Pain intensity did not significantly affect the association between these psychological factors and spinal motor behaviour and had a very small independent association with spinal motor behaviour. In conclusion, the very small effect sizes found in the meta-analyses question the role of psychological factors as major causes of spinal movement avoidance in low back pain. Experimental studies with more specific and individualized measures of psychological factors, pain intensity, and spinal motor behaviour are recommended.

Lately, the projection of foot placement visual cues onto the floor has been considered for use in gait rehabilitation. While promising, this approach needs further basic assessment to ensure proper uses.Does following floor-projected foot placement visual cues of one's natural walking pattern induce gait mechanics changes immediately or after a practice period?Gait mechanics data from fifteen healthy individuals (7 female, 25.4 ± 5.0 years, 21.5 ± 1.68 kg/mCompared to normal walking without foot placement visual cues, there was a statistically significant (p 0.05) increase in stride length (maximum change of 0.01 ± 0.01 m), stance phase knee flexion (2.0 ± 2.5°), and swing phase hip flexion (1.2 ± 1.3°) in both immediate and post-practice testing phases, along with an increase in terminal stance hip (0.28 ± 0.38 %BW*Ht) and knee (0.25 ± 0.25 %BW*Ht) flexion moments in the immediate testing phase. All of these changes between testing phases were smaller than their corresponding normal gait smallest real differences (SRD). With the addition of visual cues, variability was statistically significantly decreased in spatial parameters and increased in knee flexion angle at heel strike and knee flexion moment in terminal stance.While biomechanical changes were observed, their magnitudes were small enough to suggest that floor-projected visual cues can be used in gait retraining without introducing unintended gait changes. Furthermore, the results suggested that lengthy practice periods are not necessary. The validity of these observations will, however, need to be confirmed in cases of severe impairments.

Background: Longitudinal research is required to better understand the role of spinal movement alterations in chronic low back pain (CLBP). To this end, it is critical to assess the between-session reliability of spinal movement measures., Research question: What is the within/between-session reliability of spinal movement measures in patients with CLBP and asymptomatic controls?, Methods: Spinal movement was recorded prospectively during two sessions, a week apart, for 20 patients with CLBP (60% male; 40.0 +/- 12.3 years old) and 20 asymptomatic individuals (55% male; 38.2 +/- 10.9 years old). Sagittal-plane angular amplitude and angular velocity at the lower lumbar, upper lumbar, lower thoracic and upper thoracic joints, as well as maximal erector spinae activity were measured during five daily-activity tasks. In addition, task-independent measures were obtained by averaging the measures across tasks. The Intraclass Correlation Coefficient (ICC 2,1) and the minimal detectable change (MDC) were calculated. Pearson correlation was used to compare task-independent and task-specific measures., Results: Between-session ICCs in patients with CLBP were mostly moderate to good for maximal angular amplitude and erector spinae activity measures. Lower ICCs were observed for range of angular motion and angular velocity measures (42% of ICCs < 0.5). Median MDCs were 9.6 degrees, 18.3 degrees /s and 1.0% for angular amplitude, angular velocity and erector spinae activity measures, respectively. The reliability of task-independent and task-specific measures was strongly correlated (r = 0.91, p < 0.001)., Significance: Sagittal-plane maximal angular amplitude and erector spinae activity measures during various daily-activity tasks demonstrated mostly moderate to good between-session ICCs. However, relatively large MDCs suggested that important changes are needed to be detectable. Task-independent measures reported similarly acceptable ICCs than task-specific measures, supporting their use to describe spinal movement.

As knee osteoarthritis is a disease of the entire joint, our pathophysiological understanding could be improved by the characterization of the relationships among the knee components. Diverse quantitative parameters can be characterized using magnetic resonance imaging (MRI) and computed tomography (CT). However, a lack of methods for the coordinated measurement of multiple parameters hinders global analyses. This study aimed to design an expert-supervised registration method to facilitate multiparameter description using complementary image sets obtained by serial imaging. The method is based on three-dimensional tissue models positioned in the image sets of interest using manually placed attraction points. Two datasets, with 10 knees CT-scanned twice and 10 knees imaged by CT and MRI were used to assess the method when registering the distal femur and proximal tibia. The median interoperator registration errors, quantified using the mean absolute distance and Dice index, were = 0.96 unit, respectively. These values differed by less than 0.1 mm and 0.005 units compared to the errors obtained with gold standard methods. In conclusion, an expert-supervised registration method was introduced. Its capacity to register the distal femur and proximal tibia supports further developments for multiparameter description of healthy and osteoarthritic knee joints, among other applications.

Background: Turning during walking adds complexity to gait and has been little investigated until now. Research question What are the differences in spatiotemporal parameters between young and elderly healthy adults performing quarter-turns (90 degrees), half-turns (180 degrees) and full-turns (360 degrees)? Methods: The spatiotemporal parameters of 10 young and 10 elderly adults were recorded in a laboratory while turning at 90 degrees, 180 degrees and 360 degrees. Two-way mixed ANOVA were performed to determine the effect of age and turning amplitude. Results: Elderly were slower and needed more steps and time to perform turns of larger amplitude than young adults. Cadence did not differ across age or across turning amplitude. Generally, in the elderly, the spatial pa-rameters were smaller and the temporal parameters enhancing stability (i.e., double-support phase and stance/ cycle ratio) were larger, especially for turns of larger amplitudes. In elderly adults, the variability of some spatial parameters was decreased, whereas the variability of some temporal parameters was increased. Stride width of the external leg showed the most substantial difference between groups. Most parameters differed between turning at 90 degrees and turning at larger amplitudes (180 degrees, 360 degrees). Significance This study extends the characterization of turning biomechanics with respect to ageing. It also suggested paying particular attention to the turning amplitude. Finally, the age-related differences may pave the way for new selective rehabilitation protocols in the elderly.

There is a growing interest for turning biomechanics notably because it is a more challenging task than straight-line walking during which some gait impairments are increased. Detecting heel-strike (HS) and toe-off (TO) events using the trajectory of markers attached to the feet is common in straight-line gait analysis and could reveal very useful to evaluate turning maneuvers. Yet, a comprehensive evaluation is missing, making difficult the selection of features for temporal analysis of turning. This study aimed to compare features of foot marker trajectories to detect HS and TO. Twenty healthy participants, 10 young (5 males, 23 ± 1 years old, 21.3 ± 2.2 kg/m2) and 10 elderly (4 males, 72 ± 5 years old, 26.4 ± 6.4 kg/m2), performed quarter, half, and full turns as well as straight-line walking in a gait lab. Fourteen features, adapted from straight-line walking literature, were used to detect HS and TO based on marker trajectories. Force plate measures served as reference. One HS and one TO feature were found particularly suitable. Overall, they detected more than 99% of the 1788 events recorded, with accuracies and precisions of −3.9 ms and 9.0 ms for HS and −7.8 ms and 10.7 ms for TO, respectively. Differences in accuracy and precision were observed among walking conditions and groups, but remained small, generally below 4.0 ms. In conclusion, this study identified kinematic features that can be used to analyze both turning and straight-line walking. Further assessment could be necessary with pathologies inducing severe degradation of gait patterns.

The aim of this study was to develop and assess a method of quantifying cartilage T2 relaxation times in a series of volumes of interest (VOIs) covering the entire cartilage of the femoral condyles. Subsequently, the method was used to test for T2 spatial variations in non-osteoarthritic (OA) knees.Ten non-OA subjects (five female, average 30 years) were enrolled after informed consent. Three-dimensional bone and cartilage models were created by double echo steady state (DESS) morphological magnetic resonance image (MRI) segmentation, and the models were semi-manually registered with multi-slice, multi-echo (MSME) T2 MRI. Mean T2 values were calculated for 12 VOIs derived from cartilage thickness literature and their respective superficial and deep layers.Analyses showed that intra- and inter-rater reliabilities of the presented method were "good" to "excellent" in more than 90% of the VOIs. Additionally, several spatial differences in T2 values were observed, including, for the medial condyle, higher T2 values in the anterior and central VOIs versus in the posterior VOI (p .05). T2 values were also generally higher in the superficial versus deep layers (p .05).The presented MRI T2 analysis method is reliable and provides a comprehensive quantification of spatial heterogeneity of healthy cartilage compositional properties. This method can be further applied to better understand knee OA pathophysiology and potentially define clinically relevant diagnostic features of the disease.

This study investigated associations between changes in the total joint moment (TJM) at the knee and changes in cartilage thickness after anterior cruciate ligament reconstruction (ACLR). Seventeen subjects (five males; age: 29.6 ± 7.3 years) with unilateral ACLR underwent gait analysis and magnetic resonance imaging at baseline (2.2 ± 0.3 years post-ACLR) and at long-term follow-up (7.7 ± 0.7 years post-ACLR). Knee loading was assessed using the TJM, and differences in loading were analyzed using repeated measures analysis of variance. Pearson correlation coefficients assessed associations between changes in TJM and changes in (medial-to-lateral) M/L femoral cartilage thickness ratios in the ACLR limb. Bilaterally, there was no significant change in the magnitude of the TJM first peak (TJM1), however, there was a significant increase in the percent contribution of the knee flexion moment (KFM) (p < 0.001) and decrease in the percent contribution of the knee adduction moment (KAM) to TJM1 (p < 0.001). The change in the percent contributions of KFM and KAM to TJM1 were associated with changes in M/L femoral cartilage thickness in the ACLR limb. Specifically, subjects with smaller increases in KFM contribution (R = 0.521, p = 0.032) and smaller decreases in KAM contribution (R = -0.521, p = 0.032) had a reduction in the M/L ratio in the central femoral subregion over the follow-up period, with similar trends in the external femoral subregion. The study results provide new insight into changes in the loading environment at the knee joint prospectively following ACL reconstruction and give evidence that there are modifiable gait metrics that are associated with cartilage changes after ACLR. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1546-1554, 2019.

Objective: To test whether subchondral bone mineral density (sBMD) and cartilage thickness (CTh) of femoral condyles are correlated in knees without and with severe medial femorotibial osteoarthritis (OA), using a subregional analysis with computerized tomography (CT) arthrography., Methods: CT arthrograms of 50 non-OA (18 males, 58.7 (interquartile range (IQR) = 6.6 years)) and 50 severe medial OA (24 males, 60.5 (IQR = 10.7) years) knees, were retrospectively analyzed. Bone and cartilage were segmented using custom-designed software, leading to 3D models on which each point of the subchondral surface is given a CTh and sBMD value. The average sBMD and CTh were then calculated for the entire weight-bearing regions as well as specific subregions of interest. Linear bivariate and multivariable analyses were performed to test for relationships between sBMD and CTh (regional and subregional measures, or medial-to-lateral ratios), with confounders of age, gender, femoral bone size and femorotibial angle., Results: In non-OA knees, the sBMD and CTh medial-to-lateral ratios were positively correlated for the total region and the external and internal subregions (r >= 0.341, P, Conclusions: The positive correlation between sBMD and CTh in non-OA knees, and the negative one in OA knees, bring support to the theory of a subchondral bone/cartilage functional unit, which could help to better understand the pathophysiology of OA. (c) 2018 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.

Understanding the mechanisms involved in the higher energy cost of walking (NC w : the energy expenditure above resting per unit distance) in adults with obesity is pivotal to optimizing the use of walking in weight management programmes. Therefore, this study aimed to investigate the mechanics, energetics and mechanical efficiency of walking after a large body mass loss induced by bariatric surgery in individuals with obesity. Nine adults (39.5 ± 8.6 year; BMI: 42.7 ± 4.6 kg m -2 ) walked at five fixed speeds before (baseline) and after the bariatric surgery (post 1 and post 2). Gas exchanges were measured to obtain NC w . A motion analysis system and instrumented treadmill were combined to assess total mechanical work (W tot ). Mechanical efficiency (W tot NC w -1 ) was also calculated. Participants lost 25.7 ± 3.4% of their body mass at post 1 (6.6 months; P < 0.001) and 6.1 ± 4.9% more at post 2 (12 months; P = 0.014). Mass-normalized NC w was similar between baseline and post 1 and decreased at post 2 compared to that at baseline (-6.2 ± 2.7%) and post 1 (-8.1 ± 1.9%; P ≤ 0.007). No difference was found in mass-normalized W tot during follow-up (P = 0.36). Mechanical efficiency was similar at post 1 and post 2 when compared to that at baseline (P ≥ 0.19), but it was higher (+14.1 ± 4.6%) at post 2 than at post 1 (P = 0.013). These findings showed that after a very large body mass loss, individuals with obesity may reorganize their walking pattern into a gait more similar to that of lean adults, thus decreasing their NC w by making their muscles work more efficiently. KEY POINTS: A higher net (above resting) energy cost of walking (lower gait economy) is observed in adults with obesity compared to lean individuals. Understanding the mechanisms (i.e. mass driven, gait pattern and behavioural changes) involved in this extra cost of walking in adults with obesity is pivotal to optimizing the use of walking to promote daily physical activity and improve health in these individuals. We found that very large weight loss induced by bariatric surgery significantly decreased the energy cost of walking per kg of body mass after 1 year with similar total mechanical work per kg of body mass, resulting in an increased mechanical efficiency of walking. Individuals with obesity may reorganize their walking pattern into a gait more similar to that of adults of normal body mass, thus decreasing their energy cost of walking by making their muscles work more efficiently.

Alterations in cartilage thickness (CTh) are a hallmark of knee osteoarthritis, which remain difficult to characterize at high resolution, even with modern magnetic resonance imaging (MRI), due to a paucity of standardization tools. This study aimed to assess a computational anatomy method producing standardized two-dimensional femorotibial CTh maps. The method was assessed with twenty knees, processed following three common experimental scenarios. Cartilage thickness maps were obtained for the femorotibial cartilages by reconstructing bone and cartilage mesh models in tree-dimension, calculating three-dimensional CTh maps, and anatomically standardizing the maps. The intra-operator accuracy (median (interquartile range, IQR) of &minus, 0.006 (0.045) mm), precision (0.152 (0.070) mm), entropy (7.02 (0.71) and agreement (0.975 (0.020))) results suggested that the method is adequate to capture the spatial variations in CTh and compare knees at varying osteoarthritis stages. The lower inter-operator precision (0.496 (0.132) mm) and agreement (0.808 (0.108)) indicate a possible loss of sensitivity to detect differences in a setting with multiple operators. The results confirmed the promising potential of anatomically standardized maps, with the lower inter-operator reproducibility stressing the need to coordinate operators. This study also provided essential reference data and indications for future research using CTh maps.

International audience; Subtransus multiaxial hot forging of α+β Ti-6Al-4V (TA6V) titanium alloy with a β-transformed microstructure aims at obtaining an equiaxed microstructure through α phase globularization. The activation of mechanisms involved in microstructural evolution, such as globularization, depends on parameters such as time, temperature, strain and strain rate. It is also sensitive to the crystallographic orientation of α-lamellae. As a result, multiaxial processing of titanium alloys leads to significant microstructural gradients depending on thermomechanical conditions and initial microstructure. In this study, we focused on the effect of complex thermomechanical paths on microstructural evolutions. Thanks to the MaxStrain Gleeble device, we were able to reproduce such thermomechanical treatments to β-transformed TA6V samples. Stress strain fields obtained with finite element modelling of the MaxStrain test were compared to experimental microstructure gradients. This experimental method offers the opportunity to get closer to industrial open die forging conditions.

This perspective paper presents converging recent knowledge in neurosciences (motor neurophysiology, neuroimaging and neuro cognition) and biomechanics to outline the relationships between maturing neuronal network, behavior, and gait in human development. Autism Spectrum Disorder (ASD) represents a particularly relevant neurodevelopmental disorder (NDD) to study these convergences, as an early life condition presenting with sensorimotor and social behavioral alterations. ASD diagnosis relies solely on behavioral criteria. The absence of biological marker in ASD is a main challenge, and hampers correlations between behavioral development and standardized data such as brain structure alterations, brain connectivity, or genetic profile. Gait, as a way to study motor system development, represents a well-studied, early life ability that can be characterized through standardized biomechanical analysis. Therefore, developmental gait biomechanics might appear as a possible motor phenotype and biomarker, solid enough to be correlated to neuronal network maturation, in normal and atypical developmental trajectories—like in ASD.

This study tested for longitudinal changes in femoral cartilage T2 relaxation time and thickness in fast-progressing medial femorotibial osteoarthritis (OA). From the Osteoarthritis Initiative (OAI) database, nineteen knees fulfilled the inclusion criteria, which included medial femorotibial OA and sequential progression from Kellgren–Lawrence grade (KL) 1 to KL2 to KL3 within five years. Median T2 value and mean thickness were calculated for six condylar volumes of interest (VOIs, medial/lateral anterior, central, posterior) and six sub-VOIs (medial/lateral anterior external, central, internal). T2 value and thickness changes between severity timepoints were tested using repeated statistics. T2 values increased between KL1 and KL2 and between KL1 and KL3 in the medial compartment (p ≤ 0.02), whereas both increases and decreases were observed between the same timepoints in the lateral compartment (p ≤ 0.02). Cartilage thickness decreased in VOI/subVOIs of the medial compartment from KL1 to KL2 and KL3 (p ≤ 0.014). Cartilage T2 value and thickness changes varied spatially over the femoral condyles. While all T2 changes occurred in the early radiographic stages of OA, thickness changes occurred primarily in the later stages. These data therefore support the use of T2 relaxation time analyses in methods of detecting disease-related change during early OA, a valuable period for therapeutic interventions.

Summary Objective To address the need for early knee osteoarthritis (OA) markers by testing if longitudinal cartilage thickness changes are associated with specific biomechanical and biological measures acquired at a baseline test in asymptomatic aging subjects. Design Thirty-eight asymptomatic subjects over age 45 years were studied at baseline and at an average of 7–9 year follow-up. Gait mechanics and knee MRI were measured at baseline and MRI was obtained at follow-up to assess cartilage thickness changes. A subset of the subjects (n = 12) also had serum cartilage oligomeric matrix protein measured at baseline in response to a mechanical stimulus (30-min walk) (mCOMP). Baseline measures, including the knee extension (KEM), flexion (KFM), adduction (KAM) moments and mCOMP, were tested for associations with cartilage thickness changes in specific regions of the knee. Results Cartilage change in the full medial femoral condyle (p = 0.005) and external medial femoral region (p = 0.041) was negatively associated with larger early stance peak KEM. Similarly, cartilage change in the full medial femoral region (p = 0.009) and medial femoral external region (p = 0.043) was negatively associated with larger first peak KAM, while cartilage change in the anterior medial tibia was positively associated with larger first peak KAM (p = 0.003). Cartilage change in the anterior medial tibia was also significantly associated (p = 0.011) with mCOMP levels 5.5-h post-activity (percentage of pre-activity levels). Conclusions Interactions found between gait, mechanically-stimulated serum biomarkers, and cartilage thickness in an at-risk aging asymptomatic population suggest the opportunity for early detection of OA with new approaches that bridge across disciplines and scales.

Gait retraining is gaining in interest to reduce loading associated to knee osteoarthritis (OA) progression. So far, interventions focused on reducing the peak knee adduction moment (pKAM) and it remains unclear if this can be done individually without increasing the peak knee flexion moment (pKFM). Additionally, while modifying foot progression angle (FPA) and step width (SW) is common, little is known about modifications in stride length (SL). This study aimed at characterizing the feasibility of a dual kinetic change, consisting in reducing the pKAM by at least 10% without increasing the pKFM. It also aimed to evaluate the added value of SL modifications in achieving the dual kinetic change. Gait trials with modifications in FPA, SW and SL were recorded for 11 young healthy subjects in a laboratory equipped with an augmented-reality system displaying instruction footprints on the floor. All participants achieved the dual kinetic change with at least one of the modifications. Seven participants achieved it with FPA modification, three with SW modification, and seven with SL modification. In conclusion, this study showed that it is feasible to achieve the dual kinetic change individually through subject-specific modifications in footprint parameters, suggesting that, in the future, gait retraining could aim for more specific kinetic changes than simply pKAM reductions. Modifying SL allowed achieving the dual kinetic change, stressing out the value of this parameter for gait retraining, in addition to FPA and SW. Finally, an augmented-reality approach was introduced to help footprint parameter modifications in the framework of knee OA. (C) 2020 The Author(s). Published by Elsevier Ltd.

Although still limited in clinical practice, quantitative analysis is expected to increase the value of musculoskeletal (MSK) imaging. Segmentation aims at isolating the tissues and/or regions of interest in the image and is crucial to the extraction of quantitative features such as size, signal intensity, or image texture. These features may serve to support the diagnosis and monitoring of disease. Radiomics refers to the process of extracting large amounts of features from radiologic images and combining them with clinical, biological, genetic, or any other type of complementary data to build diagnostic, prognostic, or predictive models. The advent of machine learning offers promising prospects for automatic segmentation and integration of large amounts of data. We present commonly used segmentation methods and describe the radiomics pipeline, highlighting the challenges to overcome for adoption in clinical practice. We provide some examples of applications from the MSK literature.

Summary Objective To introduce an integrated joint system (IJS) model of joint health and osteoarthritis (OA) pathophysiology through a systematic review of the cross-sectional relationships among three knee properties (cartilage thickness, gait mechanics, and subchondral bone mineral density). Methods Searches using keywords associated with the three knee properties of interest were performed in PubMed, Scopus, and Ovid databases. English-language articles reporting cross-sectional correlations between at least two knee properties in healthy or tibiofemoral OA human knees were included. A narrative synthesis of the data was conducted. Results Of the 5600 retrieved articles, 13 were included, eight of which reported relationships between cartilage thickness and gait mechanics. The 744 tested knees were separated into three categories based on knee health: 199 healthy, 340 at-risk/early OA, and 205 late OA knees. Correlations between knee adduction moment and medial-to-lateral cartilage thickness ratios were generally positive in healthy, inconclusive in at-risk/early OA, and negative in late OA knees. Knee adduction moment was positively correlated with medial-to-lateral tibial subchondral bone mineral density ratios in knees of all health categories. One study reported a positive correlation between lateral tibial subchondral bone mineral density and femoral cartilage thickness in at-risk/early OA knees. Conclusions The correlations identified between knee properties in this review agreed with the proposed relationship-based IJS model of OA pathophysiology. Accordingly, the IJS model could provide insights into overcoming current barriers to developing disease-modifying treatments by considering multiple aspects of OA disease, aspects that could be assessed simultaneously at an in vivo system level.

Improving lower-limb flexion/extension angles during walking is important for the treatment of numerous pathologies. Currently, these gait retraining procedures are mostly qualitative, often based on visual assessment and oral instructions. This study aimed to propose an alternative method combining motion capture and display of target footprints on the floor. The second objectives were to determine the error in footprint modifications and the effects of footprint modifications on lower-limb flexion/extension angles. An augmented-reality system made of an optoelectronic motion capture device and video projectors displaying target footprints on the floor was designed. 10 young healthy subjects performed a series of 27 trials, consisting of increased and decreased amplitudes in stride length, step width and foot progression angle. 11 standard features were used to describe and compare lower-limb flexion/extension angles among footprint modifications. Subjects became accustomed to walk on target footprints in less than 10 min, with mean (± SD) precision of 0.020 ± 0.002 m in stride length, 0.022 ± 0.006 m in step width, and 2.7 ± 0.6° in progression angle. Modifying stride length had significant effects on 3/3 hip, 2/4 knee and 4/4 ankle features. Similarly, step width and progression angle modifications affected 2/3 and 1/3 hip, 2/4 and 1/4 knee as well as 3/4 and 2/4 ankle features, respectively. In conclusion, this study introduced an augmented-reality method allowing healthy subjects to modify their footprint parameters rapidly and precisely. Walking with modified footprints changed lower-limb sagittal-plane kinematics. Further research is needed to design rehabilitation protocols for specific pathologies.

Summary Objective To test if sagittal plane gait mechanics parameters and serum inflammation levels differ between healthy asymptomatic subjects and asymptomatic subjects with magnetic resonance imaging (MRI) evidence of cartilage loss. Design Gait mechanics and resting serum tumor necrosis factor-α (TNFα) concentrations were measured for two groups of asymptomatic subjects recruited for a previous study: Pre-Osteoarthritis (OA) subjects had MRI evidence of partial- or full-thickness knee cartilage loss in at least one compartment ( n = 52 (30 female), 1.7 ± 0.1 m, 85.3 ± 18.9 kg, 44 ± 11 years); Control subjects had no MRI features of cartilage loss, osteophytes, bone marrow lesions, nor meniscal pathology in either knee ( n = 26 (13 female), 1.7 ± 0.1 m, 74.6 ± 14.9 kg, 34 ± 10 years). Discrete measures of sagittal plane gait kinematics and kinetics were compared between subject groups and adjusted for age and body mass index (BMI) using analysis of covariance (ANCOVA). Serum TNFα concentrations were compared between groups using bootstrap t -test. Results The Pre-OA group had less extended knees ( P = 0.021) and decreased maximum external knee extension moment ( P = 0.0062) in terminal stance during gait, as well as increased resting serum TNFα concentration ( P = 0.040) as compared to Control subjects. There were no group differences in heel strike flexion angle ( P = 0.14), in maximum knee flexion moment ( P = 0.91), nor in first peak knee adduction moment (KAM) (post-hoc analysis, P = 0.39). Conclusions The finding that asymptomatic subjects with cartilage loss had gait and inflammatory characteristics similar to those previously reported in symptomatic OA patients supports the idea that there are specific mechanical and biological factors that precede the onset of knee pain in the pathogenesis of OA.

While cartilage thickness alterations are a central element of knee osteoarthritis (OA), differences among disease stages are still incompletely understood. This study aimed to quantify the spatial-variations in cartilage thickness using anatomically standardized thickness maps and test if there are characteristic patterns in patients with different stages of medial compartment knee OA. Magnetic resonance images were acquired for 75 non-OA and 100 OA knees of varying severities (Kellgren and Lawrence (KL) scores 1-4). Three-dimensional cartilage models were reconstructed and a shape matching technique was applied to convert the models into two-dimensional anatomically standardized thickness maps. Difference thickness maps and statistical parametric mapping were used to compare the four OA and the non-OA subgroups. This analysis showed distinct thickness patterns for each clinical stage that formed a coherent succession from the non-OA to the KL 4 subgroups. Interestingly, the only significant difference for early stage (KL 1) was thicker femoral cartilage. With increase in disease severity, typical patterns developed, including thinner cartilage in the anterior area of the medial condyle (significant for KL 3 and 4) and thicker cartilage in the posterior area of the medial and lateral condyles (significant for all OA subgroups). The tibial patterns mainly consisted of thinner cartilage for both medial and lateral compartments (significant for KL 2-4). Comparing anatomically standardized maps allowed identifying patterns of thickening and thinning over the entire cartilage surface, consequently improving the characterization of thickness differences associated with OA. The results also highlighted the value of anatomically standardized maps to analyze spatial variations in cartilage thickness. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2442-2451, 2017.

Although alterations in bone mineral density (BMD) at the proximal tibia have been suggested to play a role in various musculoskeletal conditions, their pathophysiological implications and their value as markers for diagnosis remain unclear. Improving our understanding of proximal tibial BMD requires novel tools for three-dimensional (3D) analysis of BMD distribution. Three-dimensional imaging is possible with computed tomography (CT), but computational anatomy algorithms are missing to standardize the quantification of 3D proximal tibial BMD, preventing distribution analyses. The objectives of this study were to develop and assess a registration method, suitable with routine knee CT scans, to allow the standardized quantification of 3D BMD distribution in the proximal tibia. Second, as an example of application, the study aimed to characterize the distribution of BMD below the tibial cartilages in healthy knees. A method was proposed to register both the surface (vertices) and the content (voxels) of proximal tibias. The method combines rigid transformations to account for differences in bone size and position in the scanner's field of view and to address inconsistencies in the portion of the tibial shaft included in routine CT scan, with a nonrigid transformation locally matching the proximal tibias. The method proved to be highly reproducible and provided a comprehensive description of the relationship between bone depth and BMD. Specifically it reported significantly higher BMD in the first 6 mm of bone than deeper in the proximal tibia. In conclusion, the proposed method offers promising possibilities to analyze BMD and other properties of the tibia in 3D.