No difference of gait parameters in patients with image-free robotic-assisted medial unicompartmental knee arthroplasty compared to a conventional technique: early results of a randomized controlled trial.

PURPOSE: 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. METHODS: 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. RESULTS: 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. CONCLUSION: No difference of gait parameters could be identified between medial UKA performed with image-free robotic-assisted technique or with conventional technique. LEVEL OF EVIDENCE: Prospective randomized controlled trial.

Cruciate-substituting and posterior-stabilised total knee arthroplasties had similar gait patterns in the short term.

PURPOSE: Surgeons want to achieve native kinematics in primary total knee arthroplasty (TKA). Cruciate-substituting (CS) implants could restore the knee kinematics more efficiently than posterior-stabilised (PS) TKA. This study aimed to compare gait patterns in patients with CS or PS TKA at 6 months. The hypothesis was that CS implants would demonstrate comparable gait parameters to PS implants at 6 months. METHODS: In this prospective case-control study, 38 primary TKA without coronal laxity were divided into 2 groups: 19 cruciate-substituting (CS) and 19 posterior-stabilised (PS) implants. The type of prosthesis was determined according to the surgical period. Exclusion criteria were TKA revision, associated procedures and inability to walk on a treadmill. Gait analysis was conducted on a treadmill 6 months postoperatively for each patient with a knee assessment device (KneeKG®). Gait characteristics included analysis in three spatial dimensions (flexion-extension, abduction-adduction, internal-external rotation, anterior-posterior translation). Clinical outcomes (Knee Society Score and Forgotten Joint Score) were compared between both groups at 6 months postoperatively. RESULTS: At 6 months, the gait analysis did not demonstrate any significant difference between CS and PS implants. The range and the maximum anteroposterior translation were similar in both groups (9.2 ± 6.5 mm in CS group vs. 8.1 ± 3 mm in PS group (n.s.); and - 5.2 ± 5 mm in CS group vs. - 6.3 ± 5.9 mm in PS group (n.s.), respectively). The internal/external rotation, the flexion, and the varus angle were similar between CS and PS implants. The KSS Knee score was higher at 6 months in the CS group than in the PS group (92.1 ± 5.6 vs. 84.8 ± 8.9 (p < 0.01)). CONCLUSION: Cruciate-substituting and posterior-stabilised TKA had similar gait patterns at 6 months postoperatively, despite a non-equivalent posterior stabilisation system. CS prostheses were an interesting option for primary TKA for knee kinematics restoration without requiring a femoral box. LEVEL OF EVIDENCE: Prospective, case-control study; Level II.

A Method for Quantifying Back Flexion/Extension from Three Inertial Measurement Units Mounted on a Horse's Withers, Thoracolumbar Region, and Pelvis.

Back mobility is a criterion of well-being in a horse. Veterinarians visually assess the mobility of a horse's back during a locomotor examination. Quantifying it with on-board technology could be a major breakthrough to help them. The aim of this study was to evaluate the accuracy of a method of quantifying the back mobility of horses from inertial measurement units (IMUs) compared to motion capture (MOCAP) as a gold standard. Reflective markers and IMUs were positioned on the withers, eighteenth thoracic vertebra, and pelvis of four sound horses. The horses performed a walk and trot in straight lines and performed a gallop in circles on a soft surface. The developed method, based on the three IMUs, consists of calculating the flexion/extension angle of the thoracolumbar region. The IMU method showed a mean bias of 0.8° (±1.5°) (mean (±SD)) and 0.8° (±1.4°), respectively, for the flexion and extension movements, all gaits combined, compared to the MOCAP method. The results of this study suggest that the developed method has a similar accuracy to that of MOCAP, opening up possibilities for easy measurements under field conditions. Future studies will need to examine the correlations between these biomechanical measures and clinicians' visual assessment of back mobility defects.

Primary osteoarthritic knees have more varus coronal alignment of the femur compared to young non-arthritic knees in a large cohort study.

PURPOSE: Many surgeons are performing total knee arthroplasty (TKA) with an aim to reproducing native anatomical coronal alignment. Yet, it remains unclear if primary osteoarthritic and non-osteoarthritic populations have similar knee coronal alignment. This study aims to describe and compare the distribution of femoral and tibial coronal alignment in a large primary osteoarthritic cohort and a young non-osteoarthritic cohort. METHODS: This is a retrospective analysis of a monocentric prospectively gathered data, from 1990 to 2019, of 2859 consecutive primary osteoarthritic knees in 2279 patients. Patients underwent standardized long-leg radiographs. Femoral mechanical angle (FMA) and tibial mechanical angle (TMA) were digitally measured using software. Femoral, tibial and knee phenotypes were analyzed, and descriptive data were reported. Data were compared to a young non-osteoarthritic population previously described. RESULTS: In osteoarthritic knees, the mean FMA was 91° ± 2.9° (range 86°-100°) and the mean TMA was 87° ± 3.1° (range 80°-94°). No significant difference was observed for FMA and TMA between genders. The most common femoral and tibial phenotypes were varus (38.7%) and neutral (37.1%). The most frequent knee phenotype was a varus femoral phenotype with a neutral tibial phenotype (15.5%), which is different to the non-osteoarthritic population. CONCLUSION: This study showed the wide distribution of knee phenotypes in a large osteoarthritic cohort. There was more varus distribution of the femoral coronal alignment compared to a non-osteoarthritic population, suggesting consideration and potential adaptation of the realignment strategy of the femoral component during TKA. LEVEL OF EVIDENCE: III.

Mechanical alignment for primary TKA may change both knee phenotype and joint line obliquity without influencing clinical outcomes: a study comparing restored and unrestored joint line obliquity.

PURPOSE: In total knee arthroplasty (TKA), knee phenotypes including joint line obliquity are of interest regarding surgical realignment strategies. The hypothesis of this study is that better clinical results, including decreased postoperative knee pain, will be observed for patients with a restored knee phenotype. METHODS: A retrospective analysis was performed on prospective data, including 1078 primary osteoarthritic knees in 936 patients. The male:female ratio was 780:298, mean age at surgery was 71.3 years ± 8.0. International Knee Society Scores and standardized long-leg radiographs (LLR) were collected preoperatively and at 2 years follow-up after TKA. Patients were categorized using the Coronal Plane Alignment of the Knee (CPAK) classification including the lateral distal femoral angle (LDFA) and medial proximal tibial angle (MPTA) measured on LLR by a single observer, allowing knee phenotypes to be categorized considering the arithmetic hip-knee-ankle (aHKA) angle (MPTA-LDFA) as measure of constitutional alignment, and joint line obliquity (JLO) (MPTA + LDFA). Clinical results were compared between patients with surgically restored preoperative constitutional knee phenotype to patients without restored constitutional knee phenotypes. Descriptive data analysis such as means, standard deviations and ranges were performed. T tests for independent samples were performed to compare group differences. Comparisons of categorical data were performed using the χ2 test. Significance was set at p < 0.05. RESULTS: A third of patients (33.4%) had constitutional knee varus with apex distal JLO. 63.5% of patients had preoperative apex distal JLO. Postoperatively, 57.8% of patients had a neutral HKA (- 2° to 2°) and a neutral JLO (- 3° and 3°), with only 18% of patients with restored constitutional knee phenotype. Of these patients, statistically less postoperative pain was observed in patients where apex distal JLO was restored compared to non-restored apex distal JLO (pain score 46.7 vs. 44.6; p = 0.02) without clinical relevance. Other categories of restored JLO or arithmetic HKA angle were not associated with improved outcomes. CONCLUSION: This study showed that performing mechanical alignment for primary TKA resulted in most cases in a change of the preoperative knee phenotype. These results emphasize the relevance of considering joint line obliquity to better understand preoperative knee deformity and better restore knee phenotypes with a more personalized realignment strategy to potentially improve TKA postoperative results. LEVEL OF EVIDENCE: III.

Femorotibial alignment measured during robotic assisted knee surgery is reliable: radiologic and gait analysis.

PURPOSE: 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. METHODS: 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). RESULTS: 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. CONCLUSION: 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.

A Method to Estimate Horse Speed per Stride from One IMU with a Machine Learning Method.

With the emergence of numerical sensors in sports, there is an increasing need for tools and methods to compute objective motion parameters with great accuracy. In particular, inertial measurement units are increasingly used in the clinical domain or the sports one to estimate spatiotemporal parameters. The purpose of the present study was to develop a model that can be included in a smart device in order to estimate the horse speed per stride from accelerometric and gyroscopic data without the use of a global positioning system, enabling the use of such a tool in both indoor and outdoor conditions. The accuracy of two speed calculation methods was compared: one signal based and one machine learning model. Those two methods allowed the calculation of speed from accelerometric and gyroscopic data without any other external input. For this purpose, data were collected under various speeds on straight lines and curved paths. Two reference systems were used to measure the speed in order to have a reference speed value to compare each tested model and estimate their accuracy. Those models were compared according to three different criteria: the percentage of error above 0.6 m/s, the RMSE, and the Bland and Altman limit of agreement. The machine learning method outperformed its competitor by giving the lowest value for all three criteria. The main contribution of this work is that it is the first method that gives an accurate speed per stride for horses without being coupled with a global positioning system or a magnetometer. No similar study performed on horses exists to compare our work with, so the presented model is compared to existing models for human walking. Moreover, this tool can be extended to other equestrian sports, as well as bipedal locomotion as long as consistent data are provided to train the machine learning model. The machine learning model's accurate results can be explained by the large database built to train the model and the innovative way of slicing stride data before using them as an input for the model.

Does a third condyle TKA restore normal gait kinematics in varus knees? In vivo knee kinematic analysis.

INTRODUCTION: Patients with knee osteoarthritis tend to modify spatial and temporal parameters during walking to reduce the pain. Total knee arthroplasty (TKA) is considered the gold standard treatment for end-stage knee osteoarthritis. However, reduced physical function of the knee is partly, but apparently not fully, remedied by surgery. The purpose of this study was to investigate the in vivo, three dimensional knee kinematics during gait at the patients with knee osteoarthritis and the influence of "third condyle" psoterior stabilized (PS) total knee arthroplasty on restoration of normal kinematics. MATERIALS AND METHODS: Twenty patients with medial knee osteoarthritis and a control group with age-matched subjects were prospectively collected for this study. The same group of 20 patients were re-assessed 10 months after total knee arthroplasty with "third condyle" PS prosthesis. All subjects were assessed with a 3D, optoelectric knee assessement device, while walking on a treadmill at a self-selected speed. For each participant, knee flexion-extension, abduction-adduction, internal-external rotation and anterior-posterior displacement, were calculated. RESULTS: The range of flexion/extension was improved significantly (39.9° ± 5.5° vs 44.8° ± 5.1°, p < 0.05) after TKA but it still remained lower than control group (6.9° ± 5.5° vs 2.2° ± 3.9°, p < 0.05). The range of motion in internal-external rotation did not change pre- and post-arthroplasty, but remained lower than the matched control group (6.7° ± 2.4° vs 9.3° ± 2.4, p < 0.05). The maximum posterior displacement during swing phase was significantly higher at post-arthroplasty group comparing with control group (-9.5 ± 2.2 vs -5.7 ± 3 mm, p < 0.05). CONCLUSION: Following "third condyle" PS-TKA, patients had better clinical, spatiotemporal and kinematic parameters. Despite improvements, the knee kinematics during gait in TKA group differed from healthy control group. TKA group had a lower extension lower range of axial rotation and an increased tibial posterior displacement.

Influence of the Level of Muscular Redundancy on the Validity of a Musculoskeletal Model.

While recent literature has clearly demonstrated that an extensive personalization of the musculoskeletal models was necessary to reach high accuracy, several components of the generic models may be further investigated before defining subject-specific parameters. Among others, the choice in muscular geometry and thus the level of muscular redundancy in the model may have a noticeable influence on the predicted musculotendon and joint contact forces. In this context, the aim of this study was to investigate if the level of muscular redundancy can contribute or not to reduce inaccuracies in tibiofemoral contact forces predictions. For that, the dataset disseminated through the Sixth Grand Challenge Competition to Predict In Vivo Knee Loads was applied to a versatile 3D lower limb musculoskeletal model in which two muscular geometries (i.e., two different levels of muscular redundancy) were implemented. This dataset provides tibiofemoral implant measurements for both medial and lateral compartments and thus allows evaluation of the validity of the model predictions. The results suggest that an increase of the level of muscular redundancy corresponds to a better accuracy of total tibiofemoral contact force whatever the gait pattern investigated. However, the medial and lateral contact forces ratio and accuracy were not necessarily improved when increasing the level of muscular redundancy and may thus be attributed to other parameters such as the location of contact points. To conclude, the muscular geometry, among other components of the generic model, has a noticeable impact on joint contact forces predictions and may thus be correctly chosen even before trying to personalize the model.

External Responsiveness and Intrasession Reliability of the Rope-Climbing Test.

Dhahbi, W, Chamari, K, Chèze, L, Behm, DG, and Chaouachi, A. External responsiveness and intrasession reliability of the rope-climbing test. J Strength Cond Res 30(10): 2952-2958, 2016-Although the rope-climbing test (RCT) has been validated for upper-body power assessment of Commando soldiers, the external responsiveness and intrasession reliability of the RCT have not been reported. To examine RCT external responsiveness and intrasession reliability, this study consisted of 2 separate phases. Forty male soldiers belonging to the special units of the National Guard, selected on the basis of their training and specialty operations levels, participated in the first phase of the study to identify the discriminant ability of RCT. This group was then divided into anti-terrorism Commandos (21 soldiers) and Intervention-Brigade (19 soldiers). Only the anti-terrorism Commandos participated in the intrasession reliability study. The Commandos were significantly better than the Intervention-Brigade soldiers on execution time (ET), absolute power output (APO), and relative power output (RPO; p < 0.001). The areas under the receiver operator characteristics curves were all higher than 0.70: 0.91, 0.85, and 0.90 for ET, APO, and RPO, respectively. The RCT provided good external responsiveness; thus, RCT was considered to indicate "good" discriminative ability. No significant difference was found between groups in posttest rating of perceived exertion. The intrasession reliability coefficients were excellent for ET, APO, and RPO (intraclass correlation coefficient [3,1] > 0.90). The standard errors of measurement values for the ET, APO, and RPO were all less than 5% (range: 1.29-1.47%). The main findings of this study suggest that RCT is a tool with both high sensitivity and intrasession reliability, allowing the consistent detection of differences in upper-limb power performance between the 2 military groups of different operational capacity levels.

What portion of the soft tissue artefact requires compensation when estimating joint kinematics?

When joint kinematics is analyzed using noninvasive stereophotogrammetry, movements of the skin markers relative to the underlying bone are regarded as artefacts (soft tissue artefact (STA)). Recent literature suggests that an appropriate estimation of joint kinematics may be obtained by compensating for only a portion of the STA, but no evidence for this case has been reported, and which portion of the STA should be selected remains an issue. The aim of this study was to fill this gap. A modal approach was used to represent the STA. This resulted in a series of additive components (modes) and in the possibility to select a subset of them. The following STA definitions were used: individual skin marker displacement (MD), marker-cluster geometrical transformation (GT), and skin envelope shape variation (SV). An STA approximation for each of the three definitions was obtained by ordering modes on the basis of their contribution to the total STA energy and truncating the relevant series at 90% of it. A fourth approximation was obtained when the GT definition was used, by selecting the modes that represented the marker-cluster rigid transformation (i.e., three translation and three rotation modes). The different STA approximations were compared using data obtained during the stance phase of running of three volunteers carrying both pin and skin markers. The STA was measured and knee joint kinematics estimated using four skin marker datasets compensated for the above-mentioned STA approximations. Accuracy was assessed by comparing results to the reference kinematics obtained using pin markers. The different approximations resulted in different numbers of modes. For joint angles, the compensation efficiency across the STA approximations based on an energy threshold was almost equivalent. The median root mean square errors (RMSEs) were below 1 deg for flexion/extension and 2 deg for both abduction/adduction and internal/external rotation. For the joint displacements, the compensation efficiency depended on the STA approximation. Median RMSEs for anterior/posterior displacement ranged from 1 to 4 mm using either MD, GT, or SV truncated series. The RMSEs were virtually null when the STA was approximated using only the GT rigid modes. This result, together with the limited number of modes used by this approximation (i.e., three translations and three rotations of the marker-cluster), makes the STA rigid component and a good candidate for designing an STA model to be incorporated in an enhanced bone pose estimator.

Gait knee kinematics after ACL reconstruction: 3D assessment.

PURPOSE: While many studies about anterior-cruciate-ligament-deficient (ACLD) patients have demonstrated functional adaptations to protect the knee joint, an increasing number of patients undergo ACL reconstruction (ACLR) surgery in order to return to their desired level of activity. The purpose of this study was to compare 3D kinematic patterns between individuals having undergone ACLR with their healthy contralateral knee and a control group. METHODS: Three-dimensional kinematic data were obtained from 15 patients pre- and post-ACLR, 15 contralateral knees and 15 healthy controls. Data were recorded during treadmill walking at self-selected speed. Flexion/extension, external/internal tibial rotation, adduction/abduction and anterior/posterior tibial translation were compared between groups. RESULTS: ACLR knees showed a significantly higher knee-joint extension during the entire stance phase compared with ACLD knees. However, ACLR knees still showed a deficit of extension compared with healthy control knees. In the axial plane, there was no significant difference in pre- and postoperative kinematic data. Significant difference was achieved between ACLR knees and healthy control knees, specifically between 28 and 34 % and 44 and 54 % of the gait cycle. There was no significant difference in anterior-posterior translation or coronal plane between groups. CONLUSION: Following ACL reconstruction, patients have better clinical and kinematic parameters. Despite improvements, knee kinematics during gait in the ACLR group differed from the control group. These kinematic changes could lead to abnormal loading in the knee joint and initiate the process for future chondral degeneration.

Gait knee kinematic alterations in medial osteoarthritis: three dimensional assessment.

PURPOSE: Although kinematic changes in the sagittal plane of the osteoarthritic knee (OA) have been elucidated, very few studies have analysed changes in the frontal and horizontal planes. Therefore, the aim of this study was to investigate in vivo 3D knee kinematics during walking in patients wth knee OA. METHODS: Thirty patients with medial knee OA and a control group of similarly aged individuals were prospectively collected for this study. All participants were assessed with KneeKG(TM) system while walking on a treadmill at a self-selected speed. In each trial, we calculated the angular displacment of flexion/extension, abduction/adduction and external/internal tibial rotation. Statistical analysis was performed to determine differences between the knee OA group and the control group. RESULTS: Patients with knee OA had reduced extension during the stance phase (p < 0.05; 8.5° and 4.4°, OA and control group, respectively) and reduced flexion during pushoff and initial swing phase (p < 0.05; 41.9° and 49.4°, respectively). Adduction angle was consistently greater for OA patients (p < 0.05; 3.4° and -0.9°, respectively). Frontal laxity for OA patients was positively correlated with varus deformity (r = 0.42, p < 0.05). There was a significant difference (p) < 0.05 in tibial rotation during the midstance phase; OA patients retained a neutral position (-0.4°), while the control group presented internal tibial rotation (-2.2°). CONCLUSION: Weight-bearing kinematics in medial OA knees differs from that of normal knees. The knee OA group showed an altered "screw-home" mechanism by decreased excursion in sagittal and axial tibial rotation and posterior tibial translation.

An evaluation of CT-scan to locate the femoral head centre and its implication for hip surgeons.

PURPOSE: The aim of this preliminary study was to determine the accuracy of CT-scan to locate the femoral head centre. METHODS: Eleven dried femurs were included for study. Three techniques were compared to determine femoral head centre (FHC) location: CT-scan, Motion Analysis and Faro-Arm. Markers were stuck on each femur to create a system of coordinates. Femurs lied on their posterior parts (bicondylar plane). Several points around the femoral head were palpated (Motion Analysis and Faro-Arm) or determined (Amira software for CT-scans). By a least-square regression method, the FHC location in 3D was defined for each technique. RESULTS: The results of the FHC location determined by the CT-scan technique were compared with those measured by the faro-arm and the Motion Analysis techniques. The coordinates (X, Y, Z) of the FHC were compared between the three methods, and no statistical difference was found (p = 0.99). In a 3D plot, this gave a mean difference of 1.3 mm. The mean radius of the femoral head was of 22.5 mm (p = 0.6). CONCLUSIONS: CT-scan is as accurate and reliable as gold-standard techniques (motion and faro-arm). Locating FHC before and after hip arthroplasty would allow hip surgeons to determine and compare 3D orientation of the upper-end of femur: offset, height and anteversion.

Scapulothoracic kinematics during tennis forehand drive.

Scapular dyskinesis is recognized as an abnormality in the kinetic chain; yet, there has been little research quantifying scapular motion during sport tasks. Tennis forehand drives of eight highly skilled tennis players were studied to assess the scapulothoracic kinematics and evaluate repeatability using video-based motion analysis. Scapulothoracic downward/upward rotation, posterior/anterior tilt, and internal/external rotation were computed using an acromial marker cluster. On average, the upward rotation, anterior tilt, and internal rotation varied from 1 degrees to 26 degrees, from 7 degrees to 32 degrees, and from 42 degrees to 100 degrees, respectively, during the tennis forehand drive. During the backswing and forward swing phases of the forehand stroke, small changes were observed for the three scapular angle values, while all angles increased rapidly during the follow-through phase. This suggests that the tennis forehand drive may contribute to scapula dyskinesis, mainly due to the great amplitude in scapulothoracic anterior tilt and internal rotation observed during the follow-through phase. Knowledge of normal scapula motion during sport tasks performed at high velocity could improve the understanding of various sport-specific adaptations and pathologies.

Establishment of anterior cruciate ligament injury thresholds for injured pediatric population with GNRB®, a prospective study on 141 children.

BACKGROUND: Treating an anterior cruciate ligament (ACL) injury in pediatric patients is challenging. The GNRB® is a diagnostic tool for laximetry and can provide valuable information for clinical decision. As few data exist on this subject, the first objective is to provide physiological laxity values of anterior tibial translation in healthy and pathological knees in pediatric population by age and gender groups. A second objective is to establish injury thresholds with the GNRB®. METHODS: This prospective study included 141 pediatric patients with a complete ACL tear. They all underwent GNRB® measurements before the surgery. Age and gender groups were created: child/adolescent girls and child/adolescent boys. Thresholds were established using ROC curves and 2-factors ANOVA tests were used for comparisons. RESULTS: A significant age effect was found for laxities measured on healthy knees. Significant age and gender effects were found for laxities measured on pathological knees and for side-to-side differences of laxity (SSD) between healthy and pathological knees. The optimal threshold to detect a complete ACL rupture with GNRB® is 1.5 mm at 134N with a sensitivity of 83.7% and a specificity of 92.7%. CONCLUSION: GNRB® brought new information about ACL laxities for healthy and pathological knees in pediatric population. Children have a greater anterior tibial translation which decreases gradually with age, and girls have grater laxities than boys. Thresholds for complete ACL tears, presenting good predictive values, were established and can help surgeons in their decisions to improve clinical practice. LEVEL OF EVIDENCE: Prospective cohort study, level of evidence III.

Unconstrained 3D-kinematics of prehension in five primates: lemur, capuchin, gorilla, chimpanzee, human.

Primates are known for their use of the hand in many activities including food grasping. Yet, most studies concentrate on the type of grip used. Moreover, kinematic studies remain limited to a few investigations of the distal elements in constrained conditions in humans and macaques. In order to improve our understanding of the prehension movement in primates, we analyse here the behavioural strategies (e.g., types of grip, body postures) as well as the 3D kinematics of the whole forelimb and the trunk during the prehension of small static food items in five primate species in unconstrained conditions. All species preferred the quadrupedal posture except lemurs, which used a typical crouched posture. Grasp type differed among species, with smaller animals (capuchins and lemurs) using a whole-hand grip and larger animals (humans, gorillas, chimpanzees) using predominantly a precision grip. Larger animals had lower relative wrist velocities and spent a larger proportion of the movement decelerating. Humans grasped food items with planar motions involving small joint rotations, more similar to the smaller animals than to gorillas and chimpanzees, which used greater rotations of both the shoulder and forearm. In conclusion, the features characterising human food prehension are present in other primates, yet differences exist in joint motions. These results provide a good basis to suggest hypotheses concerning the factors involved in driving the evolution of grasping abilities in primates.

Effect of postural changes on 3D joint angular velocity during starting block phase.

Few studies have focused on the effect of posture during sprint start. The aim of this study was to measure the effect of the modification of horizontal distance between the blocks during sprint start on three dimensional (3D) joint angular velocity. Nine trained sprinters started using three different starting positions (bunched, medium and elongated). They were equipped with 63 passive reflective markers, and an opto-electronic Motion Analysis system was used to collect the 3D marker trajectories. During the pushing phase on the blocks, norm of the joint angular velocity (NJAV), 3D Euler angular velocity (EAV) and pushing time on the blocks were calculated. The results demonstrated that the decrease of the block spacing induces an opposite effect on the angular velocity of joints of the lower and the upper limbs. The NJAV of the upper limbs is greater in the bunched start, whereas the NJAV of the lower limbs is smaller. The modifications of NJAV were due to a combination of the movement of the joints in the different degrees of freedom. The medium start seems to be the best compromise because it leads, in a short pushing time, to a combination of optimal joint velocities for upper and lower segments.

Joint Kinetics to Assess the Influence of the Racket on a Tennis Player's Shoulder.

This study aimed at investigating the influence of three rackets on shoulder net joint moments, power and muscle activity during the flat tennis serve under field- conditions. A 6-camera Eagle(®) motion analysis system, operating at 256 Hz, captured racket and dominant upper limb kinematics of the serve in five tennis players under three racket conditions (A: low mass, high balance and polar moment, B: low three moments of inertia, and C: high mass, swingweight and twistweight). The electromyographic activity of six trunk and arm muscles was simultaneously recorded. Shoulder net joint moments and power were computed by 3D inverse dynamics. The results showed that greater shoulder joint power and internal/external rotation peak moments were found to accelerate and decelerate racket A in comparison with the racket C. Moreover, serving with the racket A resulted in less activity in latissimus dorsi muscle during the acceleration phase, and biceps brachii muscle during the follow-through phase when compared with racket C. These initial findings encourage studying the biomechanical measurements to quantify the loads on the body during play in order to reduce them, and then prevent shoulder injuries. Racket specifications may be a critical point for coaches who train players suffering from shoulder pain and chronic upper limb injuries should be considered in relation to the racket specifications of the players. Key PointsLight racket required more joint power than heavy one to achieve similar post impact ball velocity.Serving with a light racket resulted in higher shoulder internal and external rotation moments than using a heavy one for similar performance.Chronic shoulder pain should encourage coaches to check for potentially inappropriate racket specifications of their players.

Measuring objective physical activity in people with chronic low back pain using accelerometers: a scoping review.

Purpose: Accelerometers can be used to objectively measure physical activity. They could be offered to people with chronic low back pain (CLBP) who are encouraged to maintain an active lifestyle. The aim of this study was to examine the use of accelerometers in studies of people with CLBP and to synthesize the main results regarding the measurement of objective physical activity. Methods: A scoping review was conducted following Arksey and O'Malley's framework. Relevant studies were collected from 4 electronic databases (PubMed, Embase, CINHAL, Web of Science) between January 2000 and July 2023. Two reviewers independently screened all studies and extracted data. Results: 40 publications out of 810 citations were included for analysis. The use of accelerometers in people with CLBP differed across studies; the duration of measurement, physical activity outcomes and models varied, and several limitations of accelerometry were reported. The main results of objective physical activity measures varied and were sometimes contradictory. Thus, they question the validity of measurement methods and provide the opportunity to discuss the objective physical activity of people with CLBP. Conclusions: Accelerometers have the potential to monitor physical performance in people with CLBP; however, important technical limitations must be overcome.