Simultaneous Evaluation of Bone Cut and Implant Placement Accuracy in Robotic-Assisted Total Knee Arthroplasty.

Background: This study aimed to evaluate the accuracy of bone cuts and implant placements, simultaneously, for total knee arthroplasty (TKA) performed using a system with an active robotic arm. Methods: Two experienced orthopaedic surgeons performed TKA on ten cadaveric legs. Computed tomography scans were performed to compare the bone cuts and implant placements with the preoperative planning. The differences between the planned and actual bone cuts and implant placements were assessed using positional and angular errors in the three anatomical planes. Additionally, the cut-implant deviations were calculated. Statistical analysis was performed to detect systematic errors in the bone cuts and implant placements and to quantify the correlations between these errors. Results: The root-mean-square (RMS) errors of the bone cuts (with respect to the planning) were between 0.7-1.5 mm and 0.6-1.7°. The RMS implant placement errors (with respect to the planning) varied between 0.6-1.6 mm and 0.4-1.5°, except for the femur and tibia in the sagittal plane (2.9°). Systematic errors in the bone cuts and implant placements were observed, respectively, in three and two degrees of freedom. For cut-implant deviations, the RMS values ranged between 0.3-2.0 mm and 0.6-1.9°. The bone cut and implant placement errors were significantly correlated in eight degrees-of-freedom (ρ ≥ 0.67, p < 0.05). Conclusions: With most of the errors below 2 mm or 2°, this study supported the value of active robotic TKA in achieving accurate bone cuts and implant placements. The findings also highlighted the need for both accurate bone cuts and proper implantation technique to achieve accurate implant placements.

Slowing gait during turning: how volition of modifying walking speed affects the gait pattern in healthy adults.

Background: Turning during walking and volitionally modulating walking speed introduces complexity to gait and has been minimally explored. Research question: How do the spatiotemporal parameters vary between young adults walking at a normal speed and a slower speed while making 90°, 180°, and 360° turns? Methods: In a laboratory setting, the spatiotemporal parameters of 10 young adults were documented as they made turns at 90°, 180°, and 360°. A generalized linear model was utilized to determine the effect of both walking speed and turning amplitude. Results: Young adults volitionally reducing their walking speed while turning at different turning amplitudes significantly decreased their cadence and spatial parameters while increasing their temporal parameters. In conditions of slower movement, the variability of certain spatial parameters decreased, while the variability of some temporal parameters increased. Significance: This research broadens the understanding of turning biomechanics in relation to volitionally reducing walking speed. Cadence might be a pace gait constant synchronizing the rhythmic integration of several inputs to coordinate an ordered gait pattern output. Volition might up-regulate or down-regulate this pace gait constant (i.e., cadence) which creates the feeling of modulating walking speed.

Accuracy and Reliability of Pelvimetry Measures Obtained by Manual or Automatic Labeling of Three-Dimensional Pelvic Models.

(1) Background: The morphology of the pelvic cavity is important for decision-making in obstetrics. This study aimed to estimate the accuracy and reliability of pelvimetry measures obtained when radiologists manually label anatomical landmarks on three-dimensional (3D) pelvic models. A second objective was to design an automatic labeling method. (2) Methods: Three operators segmented 10 computed tomography scans each. Three radiologists then labeled 12 anatomical landmarks on the pelvic models, which allowed for the calculation of 15 pelvimetry measures. Additionally, an automatic labeling method was developed based on a reference pelvic model, including reference anatomical landmarks, matching the individual pelvic models. (3) Results: Heterogeneity among landmarks in radiologists' labeling accuracy was observed, with some landmarks being rarely mislabeled by more than 4 mm and others being frequently mislabeled by 10 mm or more. The propagation to the pelvimetry measures was limited; only one out of the 15 measures reported a median error above 5 mm or 5°, and all measures showed moderate to excellent inter-radiologist reliability. The automatic method outperformed manual labeling. (4) Conclusions: This study confirmed the suitability of pelvimetry measures based on manual labeling of 3D pelvic models. Automatic labeling offers promising perspectives to decrease the demand on radiologists, standardize the labeling, and describe the pelvic cavity in more detail.

Changes in spinal motor behaviour are associated with reduction in disability in chronic low back pain: A longitudinal cohort study with 1-year follow-up.

BACKGROUND: The need to improve spinal motor behaviour in chronic low back pain (CLBP) rehabilitation remains unclear. The objective of this study was to test if changes in spinal motor behaviour were associated with changes in disability after an interdisciplinary rehabilitation program (IRP) in patients with CLBP. METHODS: Seventy-one patients with CLBP participating in an IRP were included. Spinal motor behaviour was assessed with biomechanical (lumbar angular amplitude and velocity, erector spinae muscle activity and duration of the task), cognitive-emotional (task-specific fear [PRF]) and pain-related (movement-evoked pain [MEP]) measures during a lifting task before and after the IRP. Disability was measured before and after the IRP, and at 3-month and 1-year follow-ups. RESULTS: After adjusting for confounders, changes in disability were significantly associated with MEP changes (ß adj. = 0.49, p < 0.001) and PRF changes (ß adj. = 0.36, p = 0.008), but not with changes in any of the biomechanical measures. MEP at the end of IRP was also associated with disability at 3 months (ß adj. = 0.37, p = 0.001) and 1 year (ß adj. = 0.42, p = 0.01). Biomechanical measures at the end of the IRP were not associated with disability, except for the duration of the task that was significantly associated with reduction of disability at 3 months (ß non-adj = 0.5, p < 0.001). CONCLUSIONS: Pain-related and cognitive-emotional measures of spinal motor behaviour were associated with reduction in disability following an IRP. Future research is needed to further investigate causal relationships between spinal motor behaviour and disability. SIGNIFICANCE STATEMENT: This study supports a multidimensional understanding and analysis of spinal motor behaviour, integrating the cognitive-emotional, pain-related and biomechanical domains. It also supports the consideration of spinal motor behaviour as a potentially important treatment target in chronic low back pain management. Moreover, it suggests that reducing movement-evoked pain and task-specific fear may have more influence on disability than changing lumbar amplitude, lumbar angular velocity or erector muscle activity, which may have important implications for rehabilitation.

Rehabilitation for Musculoskeletal Disorders: The Emergence of Serious Games and the Promise of Personalized Versions Using Artificial Intelligence.

According to the World Health Organization (WHO), musculoskeletal conditions are among the most common health problems, affecting approximately 1 [...].

Diverse parameters of ambulatory knee moments differ with medial knee osteoarthritis severity and are combinable into a severity index.

Objective: To characterize ambulatory knee moments with respect to medial knee osteoarthritis (OA) severity comprehensively and to assess the possibility of developing a severity index combining knee moment parameters. Methods: Nine parameters (peak amplitudes) commonly used to quantify three-dimensional knee moments during walking were analyzed for 98 individuals (58.7 ± 9.2 years old, 1.69 ± 0.09 m, 76.9 ± 14.5 kg, 56% female), corresponding to three medial knee osteoarthritis severity groups: non-osteoarthritis (n = 22), mild osteoarthritis (n = 38) and severe osteoarthritis (n = 38). Multinomial logistic regression was used to create a severity index. Comparison and regression analyses were performed with respect to disease severity. Results: Six of the nine moment parameters differed statistically significantly among severity groups (p ≤ 0.039) and five reported statistically significant correlation with disease severity (0.23 ≤ |r| ≤ 0.59). The proposed severity index was highly reliable (ICC = 0.96) and statistically significantly different between the three groups (p < 0.001) as well as correlated with disease severity (r = 0.70). Conclusion: While medial knee osteoarthritis research has mostly focused on a few knee moment parameters, this study showed that other parameters differ with disease severity. In particular, it shed light on three parameters frequently disregarded in prior works. Another important finding is the possibility of combining the parameters into a severity index, which opens promising perspectives based on a single figure assessing the knee moments in their entirety. Although the proposed index was shown to be reliable and associated with disease severity, further research will be necessary particularly to assess its validity.

Improved accuracy and precision of fat-suppressed isotropic 3D T2 mapping MRI of the knee with dictionary fitting and patch-based denoising.

PURPOSE: To develop an isotropic three-dimensional (3D) T2 mapping technique for the quantitative assessment of the composition of knee cartilage with high accuracy and precision. METHODS: A T2-prepared water-selective isotropic 3D gradient-echo pulse sequence was used to generate four images at 3 T. These were used for three T2 map reconstructions: standard images with an analytical T2 fit (AnT2Fit); standard images with a dictionary-based T2 fit (DictT2Fit); and patch-based-denoised images with a dictionary-based T2 fit (DenDictT2Fit). The accuracy of the three techniques was first optimized in a phantom study against spin-echo imaging, after which knee cartilage T2 values and coefficients of variation (CoV) were assessed in ten subjects in order to establish accuracy and precision in vivo. Data given as mean ± standard deviation. RESULTS: After optimization in the phantom, whole-knee cartilage T2 values of the healthy volunteers were 26.6 ± 1.6 ms (AnT2Fit), 42.8 ± 1.8 ms (DictT2Fit, p < 0.001 versus AnT2Fit), and 40.4 ± 1.7 ms (DenDictT2Fit, p = 0.009 versus DictT2Fit). The whole-knee T2 CoV reduced from 51.5% ± 5.6% to 30.5 ± 2.4 and finally to 13.1 ± 1.3%, respectively (p < 0.001 between all). The DictT2Fit improved the data reconstruction time: 48.7 ± 11.3 min (AnT2Fit) versus 7.3 ± 0.7 min (DictT2Fit, p < 0.001). Very small focal lesions were observed in maps generated with DenDictT2Fit. CONCLUSIONS: Improved accuracy and precision for isotropic 3D T2 mapping of knee cartilage were demonstrated by using patch-based image denoising and dictionary-based reconstruction. KEY POINTS: • Dictionary T2 fitting improves the accuracy of three-dimensional (3D) knee T2 mapping. • Patch-based denoising results in high precision in 3D knee T2 mapping. • Isotropic 3D knee T2 mapping enables the visualization of small anatomical details.

Walking with Different Insoles Changes Lower-Limb Biomechanics Globally in Patients with Medial Knee Osteoarthritis.

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.

Walking with shorter stride length could improve knee kinetics of patients with medial knee osteoarthritis.

Walking with a shorter stride length (SL) was recently proposed for gait retraining in medial knee osteoarthritis; however it was never assessed in this patient population. This study tested the hypothesis that shortening SL while maintaining walking speed reduces knee adduction (KAM) and flexion (KFM) moments in patients with medial knee osteoarthritis. Walking trials with normal SL and SL reduced by 0.10 m and 0.15 m were recorded for 15 patients (10 men, 55.5 ± 8.7 years old, 24.6 ± 3.0 kg/m2). SL was modified using an augmented reality system displaying target footprints on the floor. Repeated one-way ANOVAs and post-hoc paired t-tests were performed to compare gait measures between normal and reduced SL. The individual effects of SL reduction were analyzed using descriptive statistics. Group analysis indicated significant decreases in KAM impulse with both SL reductions (p < 0.05). No systematic change was observed in the first peaks KAM and KFM when walking with reduced SL (p > 0.05). Individually, 33 % of the patients decreased the peak KAM, whereas 20 % decreased the KAM impulse. Among these patients with a decrease in peak KAM or in KAM impulse, 0 % and 33 % had a simultaneous increase in peak KFM, respectively. In conclusion, this study showed that SL shortening can decrease kinetic measures associated with the progression of medial knee osteoarthritis in some patients, demonstrating the importance of considering SL modifications on an individual basis. While further research is necessary, notably regarding dose-response relationships and long-term effects, these findings are particularly encouraging because SL reductions could be easily integrated into rehabilitation protocols.

Ten-year follow-up of a total knee prosthesis combining multi-radius, ultra-congruency, posterior-stabilization and mobile-bearing insert shows long-lasting clinically relevant improvements in pain, stiffness, function and stability.

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.

Spatiotemporal parameters during turning gait maneuvers of different amplitudes in young and elderly healthy adults: A descriptive and comparative study.

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°), half-turns (180°) and full-turns (360°)? METHODS: The spatiotemporal parameters of 10 young and 10 elderly adults were recorded in a laboratory while turning at 90°, 180° and 360°. 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 parameters 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° and turning at larger amplitudes (180°, 360°). 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.

Reduction in pain-related fear is not associated with improvement in spinal biomechanics but with decrease in movement-evoked pain in patients with chronic low back pain.

BACKGROUND AND AIMS: 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. METHODS: 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. RESULTS: 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). CONCLUSION: 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.

3-D Freehand Ultrasound Calibration Using a Tissue-Mimicking Phantom With Parallel Wires.

This 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.

Between/within-session reliability of spinal kinematic and lumbar muscle activity measures in patients with chronic low back pain and asymptomatic individuals.

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°, 18.3°/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.

MRI signal and morphological alterations of the suprapatellar fat pad in asymptomatic subjects: are these normal variants?

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.

An Expert-Supervised Registration Method for Multiparameter Description of the Knee Joint Using Serial Imaging.

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 ≤0.45 mm and ≥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.

Effect of very large body mass loss on energetics, mechanics and efficiency of walking in adults with obesity: mass-driven versus behavioural adaptations.

Understanding the mechanisms involved in the higher energy cost of walking (NCw : 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 NCw . A motion analysis system and instrumented treadmill were combined to assess total mechanical work (Wtot ). Mechanical efficiency (Wtot NCw-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 NCw 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 Wtot 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 NCw 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.

Patients With Chronic Low Back Pain Have an Individual Movement Signature: A Comparison of Angular Amplitude, Angular Velocity and Muscle Activity Across Multiple Functional Tasks.

Despite a large body of evidence demonstrating spinal movement alterations in individuals with chronic low back pain (CLBP), there is still a lack of understanding of the role of spinal movement behavior on LBP symptoms development or recovery. One reason for this may be that spinal movement has been studied during various functional tasks without knowing if the tasks are interchangeable, limiting data consolidation steps. The first objective of this cross-sectional study was to analyze the influence of the functional tasks on the information carried by spinal movement measures. To this end, we first analyzed the relationships in spinal movement between various functional tasks in patients with CLBP using Pearson correlations. Second, we compared the performance of spinal movement measures to differentiate patients with CLBP from asymptomatic controls among tasks. The second objective of the study was to develop task-independent measures of spinal movement and determine the construct validity of the approach. Five functional tasks primarily involving sagittal-plane movement were recorded for 52 patients with CLBP and 20 asymptomatic controls. Twelve measures were used to describe the sagittal-plane angular amplitude and velocity at the lower and upper lumbar spine as well as the activity of the erector spinae. Correlations between tasks were statistically significant in 91 out of 99 cases (0.31 ≤ r ≤ 0.96, all p < 0.05). The area under the curve (AUC) to differentiate groups did not differ substantially between tasks in most of the comparisons (82% had a difference in AUC of ≤0.1). The task-independent measures of spinal movement demonstrated equivalent or higher performance to differentiate groups than functional tasks alone. In conclusion, these findings support the existence of an individual spinal movement signature in patients with CLBP, and a limited influence of the tasks on the information carried by the movement measures, at least for the twelve common sagittal-plane measures analysed in this study. Therefore, this work brought critical insight for the interpretation of data in literature reporting differing tasks and for the design of future studies. The results also supported the construct validity of task-independent measures of spinal movement and encouraged its consideration in the future.

Assessing feasibility and maternal acceptability of a biomechanically-optimized supine birth position: A pilot study.

BACKGROUND: In order to manage a protracted second stage of labor, "eminence-based" birth positions have been suggested by some healthcare professionals. Recent biomechanical studies have promoted the use of an optimized supine birthing position in this setting. However, uncertainty exists regarding the feasibility of this posture, and its acceptability by women. This pilot study primarily aimed to assess these characteristics. OBJECTIVE AND METHODS: In this monocentric prospective study, 20 women with a protracted second stage of labor were asked to maintain a biomechanically-optimized position for at least 20 minutes at full dilatation. This posture is similar to the McRoberts' maneuver. Maintaining the position for 20 minutes or more was considered clinically relevant and indicative of feasibility and acceptability. Satisfaction with the position was assessed using a Visual Analogue Scale (VAS). A sub-group analysis was performed to assess eventual differences between more and less satisfied patients, according to the median of patients' satisfaction scores. RESULTS: Seventeen patients (85%) maintained the optimized position for at least 20 minutes. The median satisfaction score of these participants was 8 (interquartile range: 1) out of 10. No significant differences were found between the two sub-groups (satisfaction score <8 vs satisfaction score ≥8) regarding general and obstetric characteristics, as well as obstetrical and fetal outcomes. CONCLUSION: The optimized position is acceptable and feasible for women experiencing a protracted second stage of labor. Further clinical studies are needed to assess the efficiency of such positions when women undergo an obstructed labor.

Association between changes in the knee adduction moment and changes in knee pain and function in response to non-surgical biomechanical interventions for medial knee osteoarthritis: a systematic review.

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.