Common modelling assumptions affect the joint moments measured during passive joint mobilizations.

Joint resistance to passive mobilization has already been estimated in-vivo in several studies by measuring the applied forces and moments while manipulating the joint. Nevertheless, in most of the studies, simplified modelling approaches are used to calculate this joint resistance. The impact of these simplifications is still unknown. We propose a protocol that enables a reference 3D inverse dynamics approach to be implemented and compared to common simplified approaches. Eight typically developed children and eight children with cerebral palsy were recruited and underwent a passive testing protocol, while applied forces and moments were measured through a 3D handheld dynamometer, simultaneously to its 3D kinematics and the 3D kinematics of the different segments. Then, passive joint resistance was estimated using the reference 3D inverse dynamics approach and according to 5 simplified approaches found in the literature, i.e. ignoring either the dynamometer kinematics, the measured moments alone or together with the measured tangential forces, the gravity and the inertia of the different segments, or the distal segments kinematics. These simplifications lead to non-negligible differences with respect to the reference 3D inverse dynamics, from 3 to 32% for the ankle, 4 to 34% for the knee and 1 to 58% for the hip depending of the different simplifications. Finally, we recommend a complete 3D kinematics and dynamics modelling to estimate the joint resistance to passive mobilization.

A procedure and model for the identification of uni- and biarticular structures passive contribution to inter-segmental dynamics.

Inter-segmental moments come from muscles contractions, but also from passive moments, resulting from the resistance of the periarticular structures. To quantify the passive contribution of uni- and biarticular structures during gait, we propose an innovative procedure and model. 12 typically developed (TD) children and 17 with cerebral palsy (CP) participated in a passive testing protocol. The relaxed lower limb joints were manipulated through full ranges of motion while kinematics and applied forces were simultaneously measured. The relationships between uni-/biarticular passive moments/forces and joint angles/musculo-tendon lengths were modelled by a set of exponential functions. Then, subject specific gait joint angles/musculo-tendon lengths were input into the determined passive models to estimate joint moments and power attributable to passive structures. We found that passive mechanisms contribute substantially in both populations, mainly during push-off and swing phases for hip and knee and push-off for the ankle, with a distinction between uni- and biarticular structures. CP children showed comparable passive mechanisms but larger variability than the TD ones and higher contributions. The proposed procedure and model enable a comprehensive assessment of the passive mechanisms for a subject-specific treatment of the stiffness implying gait disorders by targeting when and how passive forces are impacting gait.

A Velocity Stretch Reflex Threshold Based on Muscle-Tendon Unit Peak Acceleration to Detect Possible Occurrences of Spasticity during Gait in Children with Cerebral Palsy.

Spasticity might affect gait in children with cerebral palsy. Quantifying its occurrence during locomotion is challenging. One approach is to determine kinematic stretch reflex thresholds, usually on the velocity, during passive assessment and to search for their exceedance during gait. These thresholds are determined through EMG-Onset detection algorithms, which are variable in performance and sensitive to noisy data, and can therefore lack consistency. This study aimed to evaluate the feasibility of determining the velocity stretch reflex threshold from maximal musculotendon acceleration. Eighteen children with CP were recruited and underwent clinical gait analysis and a full instrumented assessment of their soleus, gastrocnemius lateralis, semitendinosus, and rectus femoris spasticity, with EMG, kinematics, and applied forces being measured simultaneously. Using a subject-scaled musculoskeletal model, the acceleration-based stretch reflex velocity thresholds were determined and compared to those based on EMG-Onset determination. Their consistencies according to physiological criteria, i.e., if the timing of the threshold was between the beginning of the stretch and the spastic catch, were evaluated. Finally, two parameters designed to evaluate the occurrence of spasticity during gait, i.e., the proportion of the gait trial time with a gait velocity above the velocity threshold and the number of times the threshold was exceeded, were compared. The proposed method produces velocity stretch reflex thresholds close to the EMG-based ones. For all muscles, no statistical difference was found between the two parameters designed to evaluate the occurrence of spasticity during gait. Contrarily to the EMG-based methods, the proposed method always provides physiologically consistent values, with median electromechanical delays of between 50 and 130 ms. For all subjects, the semitendinosus velocity during gait usually exceeded its stretch reflex threshold, while it was less frequent for the three other muscles. We conclude that a velocity stretch reflex threshold, based on musculotendon acceleration, is a reliable substitute for EMG-based ones.

Effect of an augmented reality active video game for gait training in children with cerebral palsy following single-event multilevel surgery: protocol for a randomised controlled trial.

INTRODUCTION: In paediatric rehabilitation, fun and motivation are also critical keys to successful therapy. A variety of interventions have shown positive effects, high level of interest, compliance and engagement with active video game (AVG).This seems to be an interesting approach for the postoperative gait rehabilitation of children with cerebral palsy (CP). In this study, we will investigate if an overground gait training (GT) delivered through an AVG can improve walking capacity and anaerobic performance. METHODS AND ANALYSIS: This study is a randomised clinical controlled trial. A total of 14 children and adolescents in the age of 10-18 years with CP will be included. The minimum time between surgery and inclusion will be 7 weeks. The test group will participate in the GT programme with Augmented Reality Rehabilitation of Walking-Cerebral Palsy AVG, control group will receive GT on a treadmill. The primary outcome is the 6-Min Walk Test assessing walking capacity; secondary outcomes are the Muscle Power Sprint Test for anaerobic performance and Shuttle Run Test for physical fitness level. Satisfaction is tested with the Physical Activity Enjoyment Scale. ETHICS AND DISSEMINATION: The findings will be disseminated by publications in peer-reviewed journals and conferences. This study received agreement from French ethic committee (Comité de Protection des Personnes Sud-Est VI-Number 2020-A02959-30). TRIAL REGISTRATION NUMBER: NCT04837105.

Visual Feedback in Augmented Reality to Walk at Predefined Speed Cross-Sectional Study Including Children With Cerebral Palsy.

In an augmented reality environment, the range of possible real-time visual feedback is extensive. This study aimed to compare the impact of six scenarios in augmented reality combining four visual feedback characteristics on achieving a target walking speed. The six scenarios have been developed for Microsoft Hololens augmented reality headset. The four feedback characteristics that we have varied were: Color; Spatial anchoring; Speed of the feedback, and Persistence. Each characteristic could have different values (for example, the color could be unicolor, bicolor, or gradient). Participants had to walk for two consecutive walking trials for each scenario: at their maximal speed and an intermediate speed. Mean speed, percentage of time spent above or around target speed, and time to reach target speed were compared between scenarios using mixed linear models. A total of 25 children with disabilities have been included. The feasibility and user experience were excellent. Mean speed during scenario 6, which displayed feedback with gradient color, attached to the world, with a speed relative to the player equal to his speed, and that disappeared over time, was significantly higher than other scenarios and control (p =0.003). Participants spent 80.98% of time above target speed during scenario 6. This scenario mixed the best combination of feedback characteristics to exceed the target walking speed (p=0.0058). Scenarios 5 and 6, which shared the same feedback characteristics for spatial anchoring (world-locked) and feedback speed (equal to the player speed), decreased the time to reach the target speed (p=0.019). Delivering multi-modal feedback has been recognized as more effective for improving motor performance. Therefore, our results showed that not all visual feedback had the same impact on performance. Further studies are required to test the weight of each feedback characteristic and their possible interactions inside each scenario. This study was registered in the ClinicalTrials.gov database (NCT04460833).

Rehabilitation After Single-Event Multilevel Surgery for Children and Young Adults With Cerebral Palsy: A Systematic Review.

ABSTRACT: This review sought to describe and analyze published protocols for rehabilitation after single-event multilevel surgery for people with cerebral palsy, to identify their differences and limits, and to introduce a common step-by-step framework for future descriptions and assessments of postoperative rehabilitation protocols.The MEDLINE, Embase, CINAHL, and the Cochrane Library databases were searched. Inclusion criteria were as follows: (1) single-event multilevel surgery, (2) full-text reports published after 1985, and (3) articles with a method section describing the rehabilitation protocol. Interventions were coded using the Oxford Levels of Evidence and the Methodological Index for Non-Randomized Studies Index.Twenty-four articles were included in the review. Studies included patients aged 4-30 yrs with spastic cerebral palsy (hemiplegia, diplegia, and quadriplegia). The mean postoperative rehabilitation duration was 4.5 mos, with 4 sessions per week, and rehabilitation took place in a rehabilitation center. This review provides relevant information about the modalities, contents, limits, and difficulties associated with the post-SEMS rehabilitation protocol reported in the literature. Pain was identified as a major problem.A more precise and comprehensive description of post-SEMS rehabilitation protocols would be useful. The proposed five-step framework could be used by future studies to standardize their protocol description in terms of objective, content, and intensity.

Validity of Hololens Augmented Reality Head Mounted Display for Measuring Gait Parameters in Healthy Adults and Children with Cerebral Palsy.

Serious games are a promising approach to improve gait rehabilitation for people with gait disorders. Combined with wearable augmented reality headset, serious games for gait rehabilitation in a clinical setting can be envisaged, allowing to evolve in a real environment and provide fun and feedback to enhance patient's motivation. This requires a method to obtain accurate information on the spatiotemporal gait parameters of the playing patient. To this end, we propose a new algorithm called HoloStep that computes spatiotemporal gait parameters using only the head pose provided by an augmented reality headset (Hololens). It is based on the detection of peaks associated to initial contact event, and uses a combination of locking distance, locking time, peak amplitude detection with custom thresholds for children with CP. The performance of HoloStep was compared during a walking session at comfortable speed to Zeni's reference algorithm, which is based on kinematics and a full 3D motion capture system. Our study included 62 children with cerebral palsy (CP), classified according to Gross Motor Function Classification System (GMFCS) between levels I and III, and 13 healthy participants (HP). Metrics such as sensitivity, specificity, accuracy and precision for step detection with HoloStep were above 96%. The Intra-Class Coefficient between steps length calculated with HoloStep and the reference was 0.92 (GMFCS I), 0.86 (GMFCS II/III) and 0.78 (HP). HoloStep demonstrated good performance when applied to a wide range of gait patterns, including children with CP using walking aids. Findings provide important insights for future gait intervention using augmented reality games for children with CP.

Contribution of passive moments to inter-segmental moments during gait: A systematic review.

Inter-segmental moments computed by inverse dynamic during gait come from active moments, due to muscle contraction, but also from passive moments, resulting from the resistance of the periarticular structures to their deformation. The evaluation of the proportion of the inter-segmental moments that can be attributed to passive moments has led to divergent results. Thus, the purpose of this study was to systematically search and synthesize the evidence of the contribution of passive moments to inter-segmental moments during healthy and pathological gait. A broad systematic search was performed including four databases. Thirteen studies met all inclusion criteria. Results showed that passive moments participate to inter-segmental moments during gait in a non-negligible way. For the ankle, the evaluation of the proportion of inter-segmental moment attributed to passive structures is 5-20% around the push-off. For the knee, this proportion is 40-98% during late swing and 10-80% during the single support phase. For the hip, it is 20-50% at push-off. For pathological population, it has been shown that this contribution may sometimes be more important, either due to a smaller inter-segmental moment or a larger passive moment. These results suggest that passive mechanisms can contribute substantially to normal human gait, facilitating the propulsion or the braking of the joint. Passive structures, acting as elastic springs, thus help to reduce the energy cost of gait. For pathological gait, studying the contribution of passive moments to inter-segmental moments can help to better understand the aetiology of the pathology.

A Classification and Calibration Procedure for Gesture Specific Home-Based Therapy Exercise in Young People With Cerebral Palsy.

Movement-based video games can provide engaging practice for repetitive therapeutic gestures towards improving manual ability in youth with cerebral palsy (CP). However, home-based gesture calibration and classification is needed to personalize therapy and ensure an optimal challenge point. Nineteen youth with CP controlled a video game during a 4-week home-based intervention using therapeutic hand gestures detected via electromyography and inertial sensors. The in-game calibration and classification procedure selects the most discriminating, person-specific features using random forest classification. Then, a support vector machine is trained with this feature subset for in-game interaction. The procedure uses features intended to be sensitive to signs of CP and leverages directional statistics to characterize muscle activity around the forearm. Home-based calibration showed good agreement with video verified ground truths (0.86 ± 0.11, 95%CI = 0.93-0.97). Across participants, classifier performance (F1-score) for the primary therapeutic gesture was 0.90 ± 0.05 (95%CI = 0.87-0.92) and, for the secondary gesture, 0.82 ± 0.09 (95%CI = 0.77-0.86). Features sensitive to signs of CP were significant contributors to classification and correlated to wrist extension improvement and increased practice time. This study contributes insights for classifying gestures in people with CP and demonstrates a new gesture controller to facilitate home-based therapy gaming.

A biofeedback-enhanced therapeutic exercise video game intervention for young people with cerebral palsy: A randomized single-case experimental design feasibility study.

IMPORTANCE/BACKGROUND: Movement-controlled video games have potential to promote home-based practice of therapy activities. The success of therapy gaming interventions depends on the quality of the technology used and the presence of effective support structures. AIM: This study assesses the feasibility of a novel intervention that combines a co-created gaming technology integrating evidence-based biofeedback and solution-focused coaching (SFC) strategies to support therapy engagement and efficacy at home. METHODS: Following feasibility and single-case reporting standards (CONSORT and SCRIBE), this was a non-blind, randomized, multiple-baseline, AB, design. Nineteen (19) young people with cerebral palsy (8-18 years old) completed the 4-week home-based intervention in France and Canada. Participant motivations, personalized practice goals, and relevance of the intervention to daily activities were discussed in a Solution Focused Coaching-style conversation pre-, post-intervention and during weekly check-ins. Participants controlled a video game by completing therapeutic gestures (wrist extension, pinching) detected via electromyography and inertial sensors on the forearm (Myo Armband and custom software). Process feasibility success criteria for recruitment response, completion and adherence rates, and frequency of technical issues were established a priori. Scientific feasibility, effect size estimates and variance were determined for Body Function outcome measures: active wrist extension, grip strength and Box and Blocks Test; and for Activities and Participation measures: Assisting Hand Assessment (AHA), Canadian Occupational Performance Measure (COPM) and Self-Reported Experiences of Activity Settings (SEAS). RESULTS: Recruitment response (31%) and assessment completion (84%) rates were good and 74% of participants reached self-identified practice goals. As 17% of technical issues required external support to resolve, the intervention was graded as feasible with modifications. No adverse events were reported. Moderate effects were observed in Body Function measures (active wrist extension: SMD = 1.82, 95%CI = 0.85-2.78; Grip Strength: SMD = 0.63, 95%CI = 0.65-1.91; Box and Blocks: Hedge's g = 0.58, 95%CI = -0.11-1.27) and small-moderate effects in Activities and Participation measures (AHA: Hedge's g = 0.29, 95%CI = -0.39-0.97, COPM: r = 0.60, 95%CI = 0.13-0.82, SEAS: r = 0.24, 95%CI = -0.25-0.61). CONCLUSION: A definitive RCT to investigate the effectiveness of this novel intervention is warranted. Combining SFC-style coaching with high-quality biofeedback may positively engage youth in home rehabilitation to complement traditional therapy. TRIAL REGISTRATION: ClinicalTrials.gov, U.S. National Library of Medicine: NCT03677193.

Kinematics after unilateral femoral derotation osteotomy in children with diplegic cerebral palsy.

INTRODUCTION: Femoral derotation osteotomy (FDO) is a treatment option in children and adolescents with cerebral palsy who have transverse plane deviations in their lower limbs. When the transverse kinematic deviations are asymmetric, the osteotomy indication can be unilateral. HYPOTHESIS: Unilateral FDO has a kinematic effect on ipsilateral transverse plane deviations along with those of the pelvis and contralateral side. MATERIALS AND METHODS: Among the 170 diplegic children that our team has operated on, 34 underwent unilateral FDO. Their mean age was 12.5±2.7 years; 12 were GMFCS level I and 22 were level II. The kinematic changes 18 months after surgery were evaluated with a paired Student's t test and correlations were determined with the Spearman test (p<0.05). The mean preoperative femoral anteversion was 45°±8°. In terms of kinematics, on the operated side, the children had a mean internal hip rotation of 26°±7°, external pelvis rotation of -8°±6° and inward foot progression angle of 8°±12°. RESULTS: The anteversion was corrected surgically by -28°±5°. Postoperatively, the ipsilateral hip rotation (10°±10°), pelvis rotation (-2°±5°) and foot rotation (6°±12°) were significantly improved. No correlations were identified between the resulting kinematic parameters and surgical correction. The five feet that had inward rotation (13°±9°) were improved to (-5°±7°). DISCUSSION: Unilateral FDO of the hip in patients with asymmetry not only reduces the internal rotation of the operated hip, it also normalizes the rotation of the pelvis and both feet. However, these improvements are not directly related to the amount of surgical correction. LEVEL OF EVIDENCE: IV: case series.

Combined 3D analysis of lower-limb morphology and function in children with idiopathic equinovarus clubfoot: A preliminary study.

INTRODUCTION: In children treated for idiopathic equinovarus clubfoot (EVCF), the relation between morphologic defects on clinical examination and standard X-ray on the one hand and functional abnormalities on the other is difficult to objectify. The aim of the present study was to demonstrate the feasibility of combined 3D analysis of the foot and lower limb based on biplanar EOS radiographs and gait analysis. The study hypothesis was that this provides better understanding of abnormalities in form and function. METHODS: Ten children with unilateral EVCF and "very good" clinical results were included. They underwent gait analysis on the Rizzoli Institute multisegment foot model. Kinematic data were collected for the hip, knee, ankle and foot (hindfoot/midfoot, midfoot/forefoot and hindfoot/forefoot). Biplanar EOS radiographs were taken to determine anatomic landmarks and radiological parameters. RESULTS: Complete acquisition time was around 2hours per patient. No significant differences were found between EVCF and healthy feet except for calcaneal incidence, tibiocalcaneal angle and hindfoot/midfoot and hindfoot/forefoot inversion. DISCUSSION: The feasibility of the combined analysis was confirmed. There were no differences in range of motion, moment or power between EVCF and healthy feet in this series of patients with very good results. The functional results are related to radiological results within the normal range. The protocol provided anatomic and kinematic reference data. A larger-scale study could more objectively assess the contribution of EOS radiography using optoelectronic markers. LEVEL OF EVIDENCE: II, low-power prospective study.

Telepsychiatry for Children and Adolescents: A Review of the PROMETTED Project.

BACKGROUND: Telemedicine for children and adolescents is a public health topic, and since 2009 in France, the legal framework defines practical modalities. Some children with Attention Deficit with or without Hyperactivity Disorder, social anxiety, or Autism Spectrum Disorder (ASD) can be easily engaged within a teleconsultation model. Literature suggests new opportunities to facilitate the care process for the ASD person and his family: diagnosis with the use of validated instruments and parental accompaniment. METHODS: Since 2015, a pilot project called PROMETTED was supported by the Regional Health Agency of Ile de France. It was developed and managed by the team of the Center for Diagnosis and Evaluation for Autism (CDEA) of Sainte-Anne Hospital and associated PEDIATED, the CDEA of Versailles. RESULTS: Five medico-social structures for children and adolescents with ASD and the two CDEAs co-elaborated a scheme of intervention with telemedicine. The remote evaluation is a four-step process structured around the medical history and the observation of the young subject; the Autism Diagnostic Interview; the use of the Childhood Autism Rating Scale and the Vineland Adaptive Behavior Scales; and feedback to parents. CONCLUSIONS: Medico-economic and satisfaction evaluations are in progress.

Predicting postoperative gait in cerebral palsy.

In this work, postoperative lower limb kinematics are predicted with respect to preoperative kinematics, physical examination and surgery data. Data of 115 children with cerebral palsy that have undergone single-event multilevel surgery were considered. Preoperative data dimension was reduced utilizing principal component analysis. Then, multiple linear regressions with 80% confidence intervals were performed between postoperative kinematics and bilateral preoperative kinematics, 36 physical examination variables and combinations of 9 different surgical procedures. The mean prediction errors on test vary from 4° (pelvic obliquity and hip adduction) to 10° (hip rotation and foot progression), depending on the kinematic angle. The unilateral mean sizes of the confidence intervals vary from 5° to 15°. Frontal plane angles are predicted with the lowest errors, however the same performance is achieved when considering the postoperative average signals. Sagittal plane angles are better predicted than transverse plane angles, with statistical differences with respect to the average postoperative kinematics for both plane's angles except for ankle dorsiflexion. The mean prediction errors are smaller than the variability of gait parameters in cerebral palsy. The performance of the system is independent of the preoperative state severity of the patient. Even if the system is not yet accurate enough to define a surgery plan, it shows an unbiased estimation of the most likely outcome, which can be useful for both the clinician and the patient. More patients' data are necessary for improving the precision of the model in order to predict the kinematic outcome of a large number of possible surgeries and gait patterns.

Dual-tasking postural control in patients with right brain damage.

The control of dual-tasking effects is a daily challenge in stroke neurorehabilitation. It maybe one of the reasons why there is poor functional prognosis after a stroke in the right hemisphere, which plays a dominant role in posture control. The purpose of this study was to explore cognitive motor interference in right brain-lesioned and healthy subjects maintaining a standing position while performing three different tasks: a control task, a simple attentional task and a complex attentional task. We measured the sway area of the subjects on a force platform, including the center of pressure and its displacements. Results showed that stroke patients presented a reduced postural sway compared to healthy subjects, who were able to maintain their posture while performing a concomitant attentional task in the same dual-tasking conditions. Moreover, in both groups, the postural sway decreased with the increase in attentional load from cognitive tasks. We also noticed that the stability of stroke patients in dual-tasking conditions increased together with the weight-bearing rightward deviation, especially when the attentional load of the cognitive tasks and lower limb motor impairments were high. These results suggest that stroke patients and healthy subjects adopt a similar postural regulation pattern aimed at maintaining stability in dual-tasking conditions involving a static standing position and different attention-related cognitive tasks. Our results indicate that attention processes might facilitate static postural control.

Rectus femoris transfer and musculo-skeletal modeling: effect of surgical treatment on gait and on rectus femoris kinematics.

Spasticity of the rectus femoris (RF) is one of the possible causes of stiff knee gait (SKG) in cerebral palsy. Musculoskeletal studies have shown that in SKG, length and speed of the RF are affected. No evaluation had been made to quantify the modifications of those parameters after surgery. The effect of this operation on gait quality and on RF kinematics was assessed in this study in order to identify kinematic patterns that may aid its diagnosis. For 26 transfers, clinical gait analysis pre- and post-surgery was used to compute the Gait Deviation Index (GDI) and Goldberg's index. The kinematics of the Original RF path (ORFp) was studied before and after surgery. The expression ORFp was chosen to avoid any confusion between this modeling parameter, whose computation was unchanged, and the actual anatomical path that was modified by surgery. The gait quality was improved (+18±12GDI) and there was an inverse relation between the pre-operative GDI and its improvement. The Golberg's index was improved (88% of the cases). The operation had a significant effect on the normalization of the timings of maximum length and speed of the ORFp. The improvement of SKG was correlated with the normalization of the timing of the ORFp's maximum length. The global improvement of the gait quality and of the SKG was demonstrated. Some parameters of muscular kinematics (RF length and velocity) have been standardized, showing an effect of the transfer not only during the swing, but also during stance. The premature timing of the ORFp peak length has been identified as a prognostic factor of a successful surgical outcome.

Self-adjusting, isostatic exoskeleton for the human knee joint.

A knee-joint exoskeleton design that can apply programmable torques to the articulation and that self-adjusts to its physiological movements is described. Self-adjustment means that the articular torque is automatically produced around the rotational axis of the joint. The requirements are first discussed and the conditions under which the system tracks the spatial relative movements of the limbs are given. If these conditions are met, the torque applied to the joint takes into account the possible relative movements of the limbs without introducing constraints. A prototype was built to demonstrate the applicability of these principles and preliminary tests were carried out to validate the design.

Proximal femoral osteotomy in neurologic pediatric hips using the locking compression plate.

BACKGROUND: Proximal femoral osteotomy (PFO) is a widely performed reconstructive surgery in pediatric patients with diagnosis of neurologic abnormalities. Many implants have been used for the fixation of these osteotomies. These devices have been evolved to provide stable fixation. A novel fixation system, the proximal femoral locking compression plate (LCP), which has a low lateral profile system, has been developed to address the problem of loosening in the osteoporotic bone, and to reach a more precise angular reduction and fixation stability through the use of locking screws. In this study, we report the surgical technique and results of PFO in children with a neurologic diagnosis. METHODS: Fifty-two children with a primary neurologic diagnosis had a femoral osteotomy with the LCP device. Clinical records and radiographs, neck-shaft angle (NSA), acetabular slope, the Reimer migration percentage, and healing of the osteotomy site were studied. Among the 70 operated hips, 59 operated hips had a follow-up superior to 1 year and were included in this study. RESULTS: Among the 59 operated hips, 25 operated hips presented with subluxations. NSA improved from 145 degrees (130 degrees to 165 degrees) to 120 degrees (110 degrees to 125 degrees) and to 125 degrees (115 degrees to 130 degrees) on last follow-up. The Reimer migration percentage improved from 60% (35% to 90%) to 25% (15% to 35%). Ten operated hips presented with dislocations. Their NSA improved from 150 degrees (145 degrees to 170 degrees) to 122 degrees (115 degrees to 125 degrees) and to 125 degrees (118 degrees to 130 degrees) at last follow-up. The stability of the operative reduction was maintained and full range of motion was preserved. Five operated hips presented with dysplastic hips with NSA>130 degrees without associated subluxation, 6 operated hips presented with windswept deformities, 10 operated hips presented with excessive femoral anteversion, and 3 operated hips presented with pseudarthrosis after earlier PFO were also treated and neither presented angular loosening at last follow-up. No major complications were observed. CONCLUSIONS: The LCP system may be used for a wide range of indications if precise preoperative planning was achieved. Rigid primary fixation allows early mobilization and weight bearing in ambulant patient. LEVEL OF EVIDENCE LEVEL IV: Therapeutic study investigating the results of a treatment studying a case series.

The convex wrapping algorithm: a method for identifying muscle paths using the underlying bone mesh.

Associating musculoskeletal models to motion analysis data enables the determination of the muscular lengths, lengthening rates and moment arms of the muscles during the studied movement. Therefore, those models must be anatomically personalized and able to identify realistic muscular paths. Different kinds of algorithms exist to achieve this last issue, such as the wired models and the finite elements ones. After having studied the advantages and drawbacks of each one, we present the convex wrapping algorithm. Its purpose is to identify the shortest path from the origin to the insertion of a muscle wrapping over the underlying skeleton mesh while respecting possible non-sliding constraints. After the presentation of the algorithm, the results obtained are compared to a classically used wrapping surface algorithm (obstacle set method) by measuring the length and moment arm of the semitendinosus muscle during an asymptomatic gait. The convex wrapping algorithm gives an efficient and realistic way of identifying the muscular paths with respect to the underlying bones mesh without the need to define simplified geometric forms. It also enables the identification of the centroid path of the muscles if their thickness evolution function is known. All this presents a particular interest when studying populations presenting noticeable bone deformations, such as those observed in cerebral palsy or rheumatic pathologies.