Study of the three-dimensional orientation of the labrum: its relations with the osseous acetabular rim

Abstract Understanding the three-dimensional orientation of the coxo-femoral joint remains a challenge as an accurate three-dimensional orientation ensure an efficient bipedal gait and posture. The quantification of the orientation of the acetabulum can be performed using the three-dimensional axis perpendicular to the plane that passes along the edge of the acetabular rim. However, the acetabular rim is not regular as an important indentation in the anterior rim was observed. An innovative cadaver study of the labrum was developed to shed light on the proper quantification of the three-dimensional orientation of the acetabulum. Dissections on 17 nonembalmed corpses were performed. Our results suggest that the acetabular rim is better represented by an anterior plane and a posterior plane rather than a single plane along the entire rim as it is currently assumed. The development of the socket from the Y-shaped cartilage was suggested to explain the different orientations in these anterior and posterior planes. The labrum forms a plane that takes an orientation in between the anterior and posterior parts of the acetabular rim, filling up inequalities of the bony rim. The vectors V L , V A2 and V P , representing the three-dimensional orientation of the labrum, the anterior rim and the posterior rim, are situated in a unique plane that appears biomechanically dependent. The three-dimensional orientation of the acetabulum is a fundamental parameter to understand the hip joint mechanism. Important applications for hip surgery and rehabilitation, as well as for physical anthropology, were discussed

Robustness and Reproducibility of a Glenoid-Centered Scapular Coordinate System Derived From Low-Dose Stereoradiography Analysis

A robust and reproducible scapular coordinate system is necessary to study scapulo-thoracic kinematics. The coordinate system recommended by the ISB (International Society of Biomechanics) is difficult to apply in studies using medical imaging, which mostly use a glenoid-centered coordinate system. The aim of this study was to assess the robustness of a glenoid-centered coordinate system compared to the ISB coordinate system, and to study the reproducibility of this coordinate system measure during abduction. A Monte-Carlo analysis was performed to test the robustness of the two coordinate systems. This method enabled the variability of the orientation of the coordinate system to be assessed in laboratory setting. A reproducibility study of the glenoid-centered coordinate system in the thorax reference frame was performed during abduction in the scapular plane using a low-dose stereoradiography system. We showed that the glenoid-centered coordinate system was slightly more robust than the ISB-recommended coordinate system. Most reproducible rotation was upward/downward rotation (x axis) and most reproducible translation was along the Y axis (superior-inferior translation). In conclusion, the glenoid-centered coordinate system can be used with confidence for scapular kinematics analysis. The uncertainty of the measures derived from our technique is acceptable compared to that reported in the literature. Functional quantitative analysis of the scapular-thoracic joint is possible with this method.We would like to thank Guillaume Simer and Benjamin Aubert for their technical support. Funding: IRSST, ParisTech BiomecAM Chair, Société Générale and Covea

3D scapular orientation on healthy and pathologic subjects using stereoradiographs during arm elevation.

Background Alterations of the scapular kinematics in different pathologic conditions have been widely studied. However, results have shown considerable discrepancies concerning the direction and the amplitude of scapular movement. The lack of consistency in the literature probably has several explanations. The purpose of this study was to analyze scapular orientation with the arm at rest and with 90° lateral elevation in healthy and pathologic subjects by use of stereoradiographs. Materials and methods All participants (n = 65) underwent a clinical examination and magnetic resonance imaging of the shoulder to assess rotator cuff status. Participants were separated into 3 groups: healthy, rotator cuff tear (RCT), and RCT and subacromial impingement syndrome (RCT+ SIS). A 3-dimensional model of the scapula was fitted to each low-dose stereoradiograph acquired with the arm at rest and 90° arm elevation. Results Orientation of the scapula with the arm at rest was not significantly different between groups. During lateral elevation, scapular orientation was not significantly different between the healthy group and the RCT group. However, upward rotation was significantly reduced in the RCT + SIS group. Conclusion Alterations of scapular kinematics in symptomatic subjects are multifactorial. We observed a link between clinically assessed subacromial impingement and scapular orientation during lateral elevation of the arm.Funding: IRSST, ParisTech BiomecAM Chair, Société Générale, and Covea

Shear wear elastography of the human Achilles tendon: a cadaveric study of factors influencing the repeatability

1. Introduction Achilles tendinopathy is a frequent disease, which can lead to tendon rupture (Hess 2010). Its treatment is controversial, partly due to the actual lack of reliable diagnostic tools in clinical practice. Shear waves elastography (SWE) is a new mode of ultrasound imaging, allowing real-time and in vivo assessment of tendon stiffness. It may facilitate tendinopathy management as this pathology is usually associated with an increase of tendon stiffness (Hess 2010; Aubry et al. 2013). The reproducibility of SWE is good in tissues such as breast (Evans et al. 2010) or liver (Muller et al. 2009), but it varies among different published studies (with variable protocols) on human Achilles tendon (AT). The aim of this study was to assess the reproducibility of human cadaveric AT SWE and to study the influencing factors, in real and optimal conditions 2. Methods 2.1. ‘Clinical practice-like’ protocol Twelve lower limbs of fresh frozen human cadavers (age = 84 ± 5 years, mean ± SD) were examined. The ATs were assessed with SWE (Aixplorer®, Supersonic Imagine, Aix-en-Provence, France), randomly and blindly by three operators. Longitudinal and axial slices were performed at three successive levels (0, 3, and 6 cm from the calcaneal insertion), in three ankle positions (position #1: neutral position, position #2: maximal dorsal flexion, position #3: 25° plantar flexion), maintained by custom-made splints (Figure 1). The longitudinal measurement at the 2nd level was made five times by every operator. The probe was held by the operator and stationed lightly on top of a generous amount of coupling gel, perpendicularly to the skin, motionless during 10 s (time of acquisition of a video clip of data). Data processing was performed blindly by one operator, who positioned the region of interest (ROI) inside the tendon area, in which the mean shear modulus was defined. Repeatability and reproducibility were calculated. 2.2. Comparison to measurements in optimal conditions Then, the limbs were surgically prepared: the ATs (with bone insertions) were sampled and mounted in a testing machine. A standardized load (10 N) was applied, and three SWE measurements were done for each tendon sample, in order to assess the reproducibility. 3. Results and discussion Mean shear modulus values were equal to 290.4 kPa (SD: 49.8), 392.0 kPa (SD: 67.6) and 126.7 kPa (SD: 40.6) for positions #1, 2 and 3, and 47.3 kPa (SD: 18.8) for the tendon samples. In longitudinal slices, our ‘clinical practice-like’ protocol reproducibility was equal to 22.1, 20.7, and 33.4% for ankle positions #1, #2, and #3, and the repeatability was equal to 15.8, 18.5, and 16.3%, respectively. The reproducibility of the tendon samples SWE was equal to 12.8%. Our results are consistent with Aubry, who demonstrated that shear modulus increased during dorsal flexion of the ankle (Aubry et al. 2013). The repeatability of SWE in tendons has been reported as ‘good’ to ‘very good’ in animal tendons through increasing loads (Peltz et al. 2013), but varies among different studies, in human AT in vivo. Turan (Turan et al. 2013) reported intra-observer agreement of 0.77, and inter-observer agreement of 0.79, while Aubry (Aubry et al. 2013) found lower inter-observer reproducibility (intra-class coefficient (ICC) equal to 0.46 and less), as well as Peltz (Peltz et al. 2013) for the repeatability (ICC = 0.42). Our results were better for the repeatability than the reproducibility, as well as for the isolated tendon SWE’s repeatability (considered as the reference value). It can be explained by the time needed to achieve a complete measurement session with three operators, which is longer than a repeatability study session (one operator). Indeed, AT has viscoelastic properties (Brum et al. 2014), such as relaxation (once the tendon has been installed on the splint), which leads to a decreasing of tendon stiffness over time. In our study, we found a mean 23% decrease of shear modulus after 20 min of installation, for position #1, 29% for position #2 (Figure 2), and 19% for position three. 4. Conclusions The repeatability of AT SWE is higher in maximal dorsal flexion, but values decrease faster over time in that position, making it necessary to take every SWE measurements after a constant time once the patient has been positioned. These findings were a prerequisite for the realization of another study, in order to validate SWE in human tendon. This study, which compares shear modulus (SWE) with apparent elastic modulus obtained by simultaneous tensile tests, will be presented soon. Acknowledgements The authors are grateful to the ParisTech BiomecAM chair program on subject-specific musculoskeletal modeling for funding (with the support of ParisTech and Yves Cotrel Foundations, Société Générale, Proteor, and Covea)

Effect of a Dual Task on Postural Control in Dyslexic Children

Several studies have examined postural control in dyslexic children; however, their results were inconclusive. This study investigated the effect of a dual task on postural stability in dyslexic children. Eighteen dyslexic children (mean age 10.3±1.2 years) were compared with eighteen non-dyslexic children of similar age. Postural stability was recorded with a platform (TechnoConcept®) while the child, in separate sessions, made reflex horizontal and vertical saccades of 10° of amplitude, and read a text silently. We measured the surface and the mean speed of the center of pressure (CoP). Reading performance was assessed by counting the number of words read during postural measures. Both groups of children were more stable while performing saccades than while reading a text. Furthermore, dyslexic children were significantly more unstable than non-dyslexic children, especially during the reading task. Finally, the number of words read by dyslexic children was significantly lower than that of non-dyslexic children and, in contrast to the non-dyslexic children. In line with the U-shaped non-linear interaction model, we suggest that the attention consumed by the reading task could be responsible for the loss of postural control in both groups of children. The postural instability observed in dyslexic children supports the hypothesis that such children have a lack of integration of multiple sensorimotor inputs

A united statement of the global chiropractic research community against the pseudoscientific claim that chiropractic care boosts immunity.

BACKGROUND: In the midst of the coronavirus pandemic, the International Chiropractors Association (ICA) posted reports claiming that chiropractic care can impact the immune system. These claims clash with recommendations from the World Health Organization and World Federation of Chiropractic. We discuss the scientific validity of the claims made in these ICA reports. MAIN BODY: We reviewed the two reports posted by the ICA on their website on March 20 and March 28, 2020. We explored the method used to develop the claim that chiropractic adjustments impact the immune system and discuss the scientific merit of that claim. We provide a response to the ICA reports and explain why this claim lacks scientific credibility and is dangerous to the public. More than 150 researchers from 11 countries reviewed and endorsed our response. CONCLUSION: In their reports, the ICA provided no valid clinical scientific evidence that chiropractic care can impact the immune system. We call on regulatory authorities and professional leaders to take robust political and regulatory action against those claiming that chiropractic adjustments have a clinical impact on the immune system

Rigid Ankle Foot Orthosis Deteriorates Mediolateral Balance Control and Vertical Braking during Gait Initiation

Rigid ankle-foot orthoses (AFO) are commonly used for impeding foot drop during the swing phase of gait. They also reduce pain and improve gait kinematics in patients with weakness or loss of integrity of ankle-foot complex structures due to various pathological conditions. However, this comes at the price of constraining ankle joint mobility, which might affect propulsive force generation and balance control. The present study examined the effects of wearing an AFO on biomechanical variables and electromyographic activity of tibialis anterior (TA) and soleus muscles during gait initiation (GI). Nineteen healthy adults participated in the study. They initiated gait at a self-paced speed with no ankle constraint as well as wearing an AFO on the stance leg, or bilaterally. Constraining the stance leg ankle decreased TA activity ipsilaterally during the anticipatory postural adjustment (APA) of GI, and ipsilateral soleus activity during step execution. In the sagittal plane, the decrease in the stance leg TA activity reduced the backward displacement of the center of pressure (CoP) resulting in a reduction of the forward velocity of the center of mass (CoM) measured at foot contact (FC). In the frontal plane, wearing the AFO reduced the displacement of the CoP in the direction of the swing leg during the APA phase. The mediolateral velocity of the CoM increased during single-stance prompting a larger step width to recover balance. During step execution, the CoM vertical downward velocity is normally reduced in order to lessen the impact of the swing leg with the floor and facilitates the rise of the CoM that occurs during the subsequent double-support phase. The reduction in stance leg soleus activity caused by constraining the ankle weakened the vertical braking of the CoM during step execution. This caused the absolute instantaneous vertical velocity of the CoM at FC to be greater in the constrained conditions with respect to the control condition. From a rehabilitation perspective, passively- or actively-powered assistive AFOs could correct for the reduction in muscle activity and enhance balance control during GI of patients

Anatomie de l'epaule (implications en chirurgie)

Cette thèse s est d abord voulue pratique. La chirurgie de l épaule est en pleine expansion avec le vieillissement croissant de la population et la pratique de plus en plus généralisée du sport. L épaule est une articulation complexe. Paradoxalement les progrès techniques en chirurgie sont sans cesse grandissants et renouvelés tandis que l on tientpour acquis des données anatomiques démontrées il y a longtemps et rapportées jusqu à nos jours. Nous avons voulu confronter l anatomie avec les techniques diagnostiques actuelles et voir si cela pouvait avoir un impact sur les pratiques chirurgicales. Nous avons également voulu voir si certaines complications chirurgicales pouvaient s expliquer par des données anatomiques. Ce qui a orienté nos recherches sont les principaux problèmes actuels en pathologie de l épaule c est-à-dire la coiffe des rotateurs et le syndrome sous-acromial. Les observations lors des nombreuses dissections de l épaule nous ont conduit à ces réflexions : comment la glène est-elle vascularisée?, pourquoi est-elle si fragile?, que se passe-t- il dans l espace sous acromial?, quelle est l utilité du ligament coraco-acromial?, quels sont ses rapports avec lesuprapinatus?, pourquoi l insertion du supraspinatus est-elle fragile et difficile à reconstituer ?, la qualité osseuse de la tête humérale a-t-elle un impact sur la géographie des fractures, les échecs des ostéosynthèses, les descellements prothétiques?, qu est ce que la chape delto-trapézoidienne? Autant de questions que nous nous sommes posées endisséquant cette articulation très complexe qui est l épaule. Par ailleurs, l anatomie classique peut maintenant secompléter non seulement de l histologie, mais aussi de techniques radiologiques modernes comme l IRM l, le microCT, le synchrotron, la reconstruction 3D, la modélisation en éléments finis.I would like to make a practical thesis. Shoulder surgery is growing and growing as the population is ageing and people is doing more and more sports activities. A lot of technical progress were done but there are still a lot of surgical complications. On the other way some very old anatomical ideas are still alive. I want to see with the actual knowledge, if some surgical complications could be explained by anatomy. Subacromial pathology and bone quality remain the two mainproblems of shoulder surgery and pathology. That s what had suggested to me this study about the shoulder. I was supposed to analyze glenoid bone first .The aim was to know more about arterial supply of glenoid. That was my firststudy (article 1). Then, I was interested in glenoid bone quality. And the second study had appeared. (article 2). During the shoulder dissection, I was looking for the fascia delto-trapezoidal which I didn t found as described in books. It was my third study. (article 3). Going on I found the coraco-acromial ligament and I was surprised to see the constant portion under the acromial process. And that gave me the idea for the fourth study. (article 4).As I had discovered the very interesting technique of micro-Ct densitometry, I would like to apply it to the humeral head bone. There was the fifth study. (article 5)But, I want to know more and more about bone quality and I went on with the greater tuberosity and especially the area ofsupraspinatus insertion. The insertion and the sub-chondral bone were analyzed. There s the last but not least study!(article 6). I was really interested in supraspinatus muscle and tendon and I want to follow the course of the muscle as the zone of conflict. I was the subject of study in life as I went through RMI . The muscle was reconstructed as finite element. Then it was possible to describe the zone of conflict with the supraspinatus. Here s the seventh article. (article 7)PARIS11-SCD-Bib. électronique (914719901) / SudocSudocFranceF

Etude du comportement mécanique de la glène pour la mise au point d'un nouvel implant scapulaire à fixation sans ciment.

Les prothèses totales d épaule ont une survie limitée due essentiellement au descellement de l implant scapulaire. Le but de ce travail de recherche est la contribution à la mise au point d un nouvel implant scapulaire à fixation sans ciment.Une première partie a concerné la caractérisation de l anisotropie et des hétérogénéités de l os spongieux de la glène par une expérimentation en compression, cette partie a abouti à l élaboration d une loi de comportement de l os spongieux de la glène. La seconde partie de ce travail s est focalisée sur la modélisation par éléments finis des contraintes aux points d ancrage de l implant.Les résultats des tests de simulation montrent l incapacité du spongieux à assurer un effet press-fit dans le plan transversal, car on observe le dépassement des contraintes maximales pour un déplacement minime. Ce résultat met en question les modes de fixation primaire utilisés ce jour dans les prothèses sans ciment. Nos résultats montrent que la modification de la direction de chargement serait susceptible d améliorer la fixation primaire ce qui ouvre des perspectives nouvelles pour le dessin d une prothèse sans ciment.Total shoulder prostheses have a limited survival due mainly to the loosening of the glenoid implant. The purpose of this research is the contribution to the development of a new glenoid implant with cementless fixation.The first part concerned the characterization of the anisotropy and heterogeneity of cancellous bone of the glenoid by a compression experimental tests, this part has led to the drafting of a law of behavior of cancellous bone of the glenoid . The second part of this work has focused on finite element modeling of stress around the anchors of the glenoid implant.Simulation test results show the inability of the transversal plane of the glenoid to ensure effective press-fit fixation with stresses above strength properties of the cancellous bone with a minimal displacement. This calls into question the current modes of primary fixation of cementless implant. However, it appears that a change in the direction of loading would be beneficial for the primary fixation, which opens new perspectives for the design of a cementless prosthesis.PARIS11-SCD-Bib. électronique (914719901) / SudocSudocFranceF