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Several diseases and medical treatments have been found to affect bone quality over decades. Bone mass characteristics summarized in bone mineral density (BMD), geometry, microarchitecture, and mechanical properties are the main parameters permitting to assess the quality of bone. Clinically, the diagnosis of bone diseases and the prediction of bone fracture are largely based on the BMD values. Thus, the investigation of how diseases and treatments alter the BMD value is primordial to anticipate additional treatment for the patient. In this chapter, we summarize the main research studies investigating diseases and treatments’ effects on bone quality and more specifically on BMD.

Bone is a biological tissue characterized by its hierarchical organization. This material has the ability to be continually renewed, which makes it highly adaptative to external loadings. Bone renewing is managed by a dynamic biological process called bone remodeling (BR), where continuous resorption of old bone and formation of new bone permits to change the bone composition and microstructure. Unfortunately, because of several factors, such as age, hormonal imbalance, and a variety of pathologies including cancer metastases, this process can be disturbed leading to various bone diseases. In this study, we have investigated the effect of breast cancer (BC) metastases causing osteolytic bone loss. BC has the ability to affect bone quantity in different ways in each of its primary and secondary stages. Based on a BR mathematical model, we modeled the BC cells' interaction with bone cells to assess their effect on bone volume fraction (BV/TV) evolution during the remodeling process. Some of the parameters used in our model have been determined experimentally using the enzyme-linked immune-sorbent assay (ELISA) and the MTT assay. Our numerical simulations show that primary BC plays a significant role in enhancing bone-forming cells' activity leading to a 6.22% increase in BV/TV over 1 year. On the other hand, secondary BC causes a noticeable decrease in BV/TV reaching 15.74% over 2 years.

Existence of a relationship between knee and hindfoot alignments is commonly accepted, but not clearly proven. While studied in the coronal plane using 2D imaging, axial alignment has not been studied yet, likely requiring 3D measurements. We aimed to investigate how knee and hindfoot rotational alignments are related using 3D biometrics and modern 3D weight-bearing technologies.Hindfoot alignment is correlated with femoral and tibial torsions.All patients who underwent both weight-bearing CT (WBCT) and low dose biplanar radiographs (LDBR) were selected in this retrospective observational study, resulting in a cohort of 157 lower limbs from 99 patients. Patients' pathologies were stratified in subgroups and those with a history of trauma or surgery affecting lower limb alignment were excluded. Foot Ankle Offset was calculated from WBCT; femoral and tibial torsions and coronal alignment were calculated from LDBR, respectively.Overall, mean Foot Ankle Offset was 1.56% (SD 7.4), mean femoral anteversion was 15.6° (SD 9.5), and mean external tibial torsion was 32.6° (SD 7.6). Moderate negative correlation between Tibial Torsion and Foot Ankle Offset was found in the whole series (rho=-0.23, p=0.003) and for non-pathologic patients (rho=-0.27, p=0.01). Linear models to estimate Tibial Torsion with Foot Ankle Offset and conversely were found, with a low adjusted RExternal tibial rotation was associated with varus hindfoot configuration in the group without pathologies, suggesting that compensatory mechanisms may occur between knee and hindfoot alignments. In pathological cases, however, the same relationship wasn't found, raising concerns about compensatory failure in spite of the numbers available. We didn't find similar correlations with the femur possibly because the hip has a degree of liberty in the axial plane.III, retrospective comparative study.

Bone density and bone microarchitecture are two principle parameters needed for the evaluation of mechanical bone performance and consequently the detection of bone diseases. The mechanobiological behavior of the skeletal tissue has been described through several mathematical models. Generally, these models fingerboard different length scale processes, such as the mechanical, the biological, and the chemical ones. By means of the mechanical stimulus and the biological factors involved in tissue regeneration, bone cells’ behavior and bone volume changes are determined. The emergence of bone diseases leads to disrupt the bone remodeling process and thus, induces bone mechanical properties’ alteration. In the present chapter, an overview of bone diseases and their relationship with bone density alteration will be presented. Besides, several studies treating bone diseases’ effect on bone remodeling will be discussed. Finally, the mechanobiological models proposed to treat bone healing and drugs’ effect on bone, are going to be reviewed. For this sake, the chapter is subdivided into three main sequences: (i) Bone remodeling, (ii) Bone deterioration causes, (iii) Mathematical models of a pathological bone, and (iv) Mechanobiological models treating bone healing and drugs effect.

International audience; This study aims at suggesting a new approach to peri-implant healing models, providing a set of taxis-diffusion-reaction equations under the combined influence of mechanical and biochemical factors. Early events of osseointegration were simulated for titanium screw implants inserted into a pre-drilled trabecular bone environment, up to twelve weeks of peri-implant bone healing. Simulations showed the ability of the model to reproduce biological events occurring at the implant interface through osteogenesis. Implants with shallow healing chamber showed higher proportions of lamellar bone, enhanced by the increase of mechanical stimulation. Osteoconduction was observed through the surface treatment model and similar bone healing patterns compared to in vivo studies.

Objective: The aim of this study was to assess, through biological analysis, the local effects and osseointegration of dental implants incorporating surface micro/nanofeatures compared to implants of identical design without surface treatment. Background: Known to impact bone cell behavior, surface chemical and topography modifications target improved osseointegration and long-term success of dental implants. Very few studies assess the performance of implants presenting both micro-and nanofeatures in vivo on the animal models used in preclinical studies for medical device certification. Methods: Implant surfaces were characterized in terms of topography and surface chemical composition. After 4 weeks and 13 weeks of implantation in sheep femoral condyles, forty implants were evaluated through micro-computed tomography, histopathologic, and histomorphometric analyses. Results: No local adverse effects were observed around implants. Histomorphometric analyses showed significantly higher bone-to-implant contact in the coronal region of the surface treated implant at week 4 and week 13, respectively 79.3$\pm$11.2% and 86.4$\pm$6.7%, compared to the untreated implant's 68.3$\pm$8.8% and 74.8$\pm$13%. Micro-computed tomography analyses revealed that healing patterns differed between coronal and apical regions, with higher coronal boneto-implant contact at week 13. Histopathologic results showed, at week 13, bone healing around the surface treated implant with undistinguishable defect margins while the untreated implant still presented bone condensation and traces of the initial drill defect. Conclusion: Our results suggest that the surface treated implant not only shows no deleterious effects on local tissues but also promotes faster bone healing around the implant. (word count: 241, Journal of Periodontal Research, Wiley, 2021

International audience; Pharmaceutical treatments can slow bone degradation, thus reducing the fracture risk inherent in osteoporosis. Antiresorptive treatments block the over-activation of osteoclasts vs osteoblasts, but the resulting decrease in bone remodeling frequency may weaken bone structure over time, with no gain in bone volume. Anabolic treatments, however, induce gain in bone volume. The quantitative results from existing studies on the effects of treatments over time are general and nonpatient-specific, while numerical models simulating evolution of patient-specific bone microarchitecture consider a spatially random distribution of the remodeling process. Here, we propose a new approach to simulate the remodeling over decades of an individual patient's bone microarchitecture, based on the hypothesis that the oldest sites, which are hypermineralized and more brittle, are remodeled first. Taking these older sites as prime targets of remodeling, simulations show that severe osteoporosis profoundly degrades the mechanical properties of the bone structure, which can be restored and even improved by anabolic, more than by antiresorptive, therapies.

Place: England; International audience; Patient-specific finite element models (PSFEM) are becoming more and more used. Different methods for assigning their material properties were studied on PSFEMs of 9 tibias along with the minimal required length of the CT acquisition window. Material properties are generally attributed to the PSFEM using relationships linking the grayscale of CT scans to the elasticity moduli. Using cortical-specific and trabecular-specific relationships or a generic one, did not result in significant differences. However, the use of homogeneous elastic moduli in the cortical and trabecular regions led to considerable differences. The result highlight that the PSFEM must comprise at least 40% of the tibia to ensure consistent results in the proximal 20%.

Osteoarthritis (OA) is a common degenerative disease whose early management includes promising mechanical treatments. New treatments are initially validated using an animal model in which OA is induced. The MMT (mechanical induction) and MIA (chemical induction) models of OA induction are widespread, but their use to generate early OA is poorly documented. We analyzed and compared early-stage knee OA-induction via these two methods in 16 rats divided into two groups. After 4 weeks of induction, the knees were sampled and studied using both histology (Toluidine Blue and Sirius Red) and surface topology, an innovative technique for characterizing osteoarthritic cartilage. The Mankin-modified score confirms that the two OA-induction models evolved at the same speed. At this early stage, the two models can be differentiated morphologically, although no significant differences were revealed by either cellularity or birefringence analysis. However, the topological analysis generated two forms of quantitative data, the deformation ratio and the cohesion index, that differentiated between the two groups. Thus, the early-stage OA induced by these two models is revealed to differ. The patterns of cartilage damage induced point to MMT as the better choice to assess mechanical approaches to clinical OA treatment.

Purpose The purpose of this study was to investigate bone microarchitecture of cadaveric proximal femurs using ultra-high field (UHF) 7-Tesla magnetic resonance imaging (MRI) and to compare the corresponding metrics with failure load assessed during mechanical compression test and areal bone mineral density (ABMD) measured using dual-energy X-ray absorptiometry. Materials and methods ABMD of ten proximal femurs from five cadavers (5 women; mean age = 86.2 ± 3.8 (SD) years; range: 82.5–90 years) were investigated using dual-energy X-ray absorptiometry and the bone volume fraction, trabecular thickness, trabecular spacing, fractal dimension, Euler characteristics, connectivity density and degree of anisotropy of each femur was quantified using UHF MRI. The whole set of specimens underwent mechanical compression tests to failure. The inter-rater reliability of microarchitecture characterization was assessed with the intraclass correlation coefficient (ICC). Associations were searched using correlation tests and multiple regression analysis. Results The inter-rater reliability for bone microarchitecture parameters measurement was good with ICC ranging from 0.80 and 0.91. ABMD and the whole set of microarchitecture metrics but connectivity density significantly correlated with failure load. Microarchitecture metrics correlated to each other but did not correlate with ABMD. Multiple regression analysis disclosed that the combination of microarchitecture metrics and ABMD improved the association with failure load. Conclusion Femur bone microarchitecture metrics quantified using UHF MRI significantly correlated with biomechanical parameters. The multimodal assessment of ABMD and trabecular bone microarchitecture using UHF MRI provides more information about fracture risk of femoral bone and might be of interest for future investigations of patients with undetected osteoporosis.

Introduction Les malpositions des implants acetabulaires grevent le resultat fonctionnel des PTH. Pour optimiser leur positionnement, les relations entre l’equilibre sagittal du rachis et l’orientation acetabulaire sont frequemment etudiees. Cependant, il n’a pas encore ete demontre de correlation entre l’incidence pelvienne (IP) et l’orientation acetabulaire anatomique. L’objectif principal de notre etude etait d’etablir des correlations entre l’IP et les parametres anatomiques acetabulaires. Materiel et methodes A partir d’une cohorte de 150 bassins indemnes de pathologies degeneratives, une etude tomodensitometrique a ete realisee. L’orientation (inclinaison et anteversion) anatomique acetabulaire dans le plan de Lewinnek, l’incidence pelvienne ainsi que l’angle sacro-pelvien (ASP) decrit comme l’angle entre la tangente a la premiere vertebre sacree et le plan pelvien anterieur etaient mesures. Des analyses statistiques ont ete realisees afin de trouver des correlations entre l’IP, l’ASP et les parametres acetabulaires. Resultats La reproductibilite inter-et intra-observateurs des mesures etait selon la methode de Bland et Altman consideree comme tres satisfaisante. L’IP moyenne de la serie etait de 58,6°, sans difference significative entre les sexes et l’âge des sujets. L’ASP moyen etait de 34,7° et n’etait correle ni a l’âge ni au sexe des sujets. L’anteversion anatomique des femmes etait plus importante que celle des hommes (23,4° vs 20° et p Discussion Cette etude sur TDM de bassins sains a permis de montrer que l’anteversion acetabulaire anatomique etait significativement plus grande chez les femmes, qu’il existait une correlation entre l’ASP et l’IP ainsi qu’entre l’ASP et la version acetabulaire. Ainsi, l’ASP permettrait de definir pour chaque patient son anteversion anatomique « theorique » et pourrait etre integre aux systemes de planification ou de guidages peroperatoires pour les chirurgies prothetiques de hanche.

Recently in veterinary medicine, a new technique of intra-articular repair is receiving increasing attention, particularly when using prosthetic ligaments (Barnhart et al. 2019). The development of...

Resume Introduction La technique d’alignement cinematique (AC) est une technique alternative pour le positionnement des implants totaux de genou. L’objectif est de realiser un positionnement des implants specifique a chaque patient dans le but de reproduire l’anatomie pre-arthritique de leur genou. La fiabilite dans le positionnement des implants est un prerequis indispensable pour l’obtention de resultats fonctionnels bons et reproductibles et cela n’a pas ete etudie concernant le positionnement de l’implant femoral. Hypothese d’etude La technique d’AC permet une reproduction fiable par l’implant prothetique femoral des surfaces articulaires condyliennes natives. Methodes L’imagerie par resonance magnetique (IRM) du genou natif et la tomodensitometrie (CT) du genou prothetique de 13 patients ont ete segmentees pour creer des modeles femoraux 3D respectivement pre et postoperatoires. Le positionnement cinematique du composant femoral a ete planifie sur le modele IRM puis l’ensemble a ete superpose avec le modele 3D CT. Les differences dans les positions de la composante femorale alignee cinematiquement et implantee chirurgicalement ont ete determinees avec un logiciel d’analyse interne. Resultats Les surfaces condyliennes prothetiques et natives (points distaux et posterieurs de chaque condyle) avaient des differences moyennes inferieures a 1 mm. En terme de variabilite, 62 % (8/13) des composants femoraux implantes respectaient une marge d’erreur maximale de 1,5 mm ; la difference maximale observee etait de 3 mm. Conclusion Le positionnement cinematique du composant femoral realise a l’aide de l’instrumentation manuelle specifique permet de reproduire de facon fiable la geometrie condylienne native. Niveau de preuve Niveau 3.

Resume Introduction La prise en charge des arthroses femoro-tibiales mediales par osteotomie tibiale de valgisation (OTV) est d’autant plus efficace que la correction angulaire est optimale. L’instrumentation conventionnelle est limitee lorsque qu’une correction dans plusieurs plans de l’espace est necessaire. Hypothese L’utilisation d’un guide de coupe sur mesure (GCM) dans les OTV permet une correction precise (difference Materiels et methodes Entre fevrier 2014 et fevrier 2015, 10 patients (âge moyen 46 ans [31–59], arthrose grade 1 et 2 selon la classification d’Ahlback) ont ete inclus prospectivement dans cette etude de fiabilite et de securite. Les patients ont ete operes selon la meme technique d’addition mediale. En preoperatoire, la planification etait fondee sur les telemetries et une tomodensitometrie avec reconstruction 3D. Les GCM obtenus permettaient le guidage de la coupe d’osteotomie et le positionnement des trous de vis. La correction visee etait obtenue dans les 3 plans de l’espace lorsque les trous de la plaque s’alignaient avec les trous perces grâce au GCM. L’angle HKA preoperatoire moyen etait de 171,9° (min 166°–max 179°), l’angle tibial proximal moyen de 87° (86°–88°), la pente tibiale de 7,8° (1°–22°). En postoperatoire, l’analyse de la correction par rapport a la planification etait effectuee grâce a un procede de recalage 3D scannographique. Les complications perioperatoires etaient relevees a un an de recul minimum. Resultats Dans tous les cas, l’intervention a pu etre realisee integralement a l’aide du GCM. Sur les telemetries postoperatoires, l’HKA moyen etait de182,3° (180°–185°), et sur le scanner, l’angle mecanique tibial moyen etait de 94° (90°–98°), la pente tibiale moyenne de 7,1° (4°–11°). Dans 19 cas sur 20 (HKA et pente), une difference Discussion Les resultats de cette etude montrent que les GCM dans l’OTV permettent d’obtenir une correction optimale de maniere fiable et securitaire. Niveau de preuve IV – etude de cohorte prospective.

New fusionless devices are being developed to get over the limits of actual spinal surgical treatment, based on arthrodesis. However, due to their recentness, no standards exist to test and validate those devices, especially concerning the wear. A new tribological first approach to the definition of an in vitro wear protocol to study wear of flexible and sliding spinal devices is presented in this article, and was applied to a new concept. A simplified synthetic spine portion (polyethylene) was developed to reproduce a simple supra-physiological spinal flexion (10° between two vertebrae). The device studied with this protocol was tested in wet environment until 1 million cycles (Mc). We obtained an encouraging estimated wear volume of same order of magnitude compared to similar devices. An associated finite element (FE) numerical model has permitted to access contact information and study the effect of misalignment of one screw. First results could point out how to improve the design and suggest that a vertical misalignment of a screw (under or over-screwing) has more impact than a horizontal one. (Less)

At advanced knee osteoarthritis (OA) stages subchondral trabecular bone (STB) is altered. Lower limb alignment plays a role in OA progression and modify the macroscopic loading of the medial and lateral condyles of the tibial plateau. How the properties of the STB relate to alignment and OA stage is not well defined. OA stage (KL scores 2–4) and alignment (HKA from 17° Varus to 8° Valgus) of 30 patients were measured and their tibial plateau were collected after total knee arthroplasty. STB tissue elastic modulus, bone volume fraction (BV/TV) and trabecula thickness (Tb.Th) were evaluated with nanoindentation and µCT scans (8.1 µm voxel-size) of medial and lateral samples of each plateau. HKA and KL scores were statistically significantly associated with STB elastic modulus, BV/TV and Tb.Th. Medial to lateral BV/TV ratio correlated with HKA angle (R = −0.53, p = 0.016), revealing a higher ratio for varus than valgus subjects. STB properties showed lower values for KL stage 4 patients. Tissue elastic modulus ratios and BV.TV ratios were strongly correlated (R = 0.81, p

Background The purpose of this study was to assess cadaveric proximal femurs from the points of view of bone microarchitecture using ultra-high field (UHF) 7 Tesla magnetic resonance imaging (MRI), bone strength using biomechanical tests and bone mineral density (BMD) using Dual-energy X-ray absorptiometry (DXA). Objectives We aimed at determining whether bone microarchitecture parameters were related to bone strength and BMD and whether UHF MRI can provide additional information regarding bone strength. Methods BMD of ten proximal femurs from five cadavers were investigated using DXA and the bone volume fraction (BVF), trabecular thickness (Tb.Th), and trabecular spacing (Tb.Sp), fractal dimension (FD), Euler characteristics (Euler Ch.), Connectivity density (Conn. D) and Degree of anisotropy (DA) of each femur was quantified using UHF MRI. The whole set of specimens underwent mechanical compression tests to failure. Results BMD and all the microarchitecture parameters except ConnD were significantly correlated with failure load (p Overall, femur bone microarchitecture assessed with UHF MRI was significantly correlated with biomechanical parameters. The multimodal assessment of BMD and trabecular bone microarchitecture using UHF MRI improved the fracture risk prediction of femoral bone and might be of interest for the future investigation of selected osteoporotic patients. Conclusion We demonstrated that femur bone microarchitecture assessed with UHF MRI was significantly correlated with biomechanical parameters. The multimodal assessment of bone mineral density and trabecular bone microarchitecture using UHF MRI improved the fracture risk prediction of femoral bone and might be of interest for the future investigation of selected osteoporotic patients. Disclosure of Interests None declared

International audience; Purpose: Damage of bone structures is mainly conditioned by bone quality related to the bone strength. The purpose of this work was to present a simple and reliable numerical treatment of a quasi-brittle damage constitutive model coupled with two different elastic modulus and to compare the numerical results with the experimental ones.Methods: To achieve this goal, a QCT based finite element model was developed within the framework of CDM (Continuum Damage Mechanics) and implemented in the FE code (ABAQUS). It described the propagation of brittle cracks which will help to predict the ultimate load fracture of a human vertebra by reproducing the experimental failure under quasi-static compressive loading paths of nineteen cadaveric lumbar vertebral bodies.Results: The numerical computations delivered by the proposed method showed a better agreement with the available experimental results when bone volume fraction related Young's modulus (E (BV/TV)) is used instead of density related Young's modulus (E (ρ)). Also, the study showed that the maximum relative error (%) in failure was 8.47% when E (BV/TV) was used, whereas the highest relative error (%) was 68.56% when E (ρ) was adopted. Finally, a mesh sensitivity analysis revealed that the element size has a weak incidence on the computed load magnitude.Conclusions: The numerical results provided by the proposed quasi-brittle damage model combined with E (BV/TV) are a reliable tool for the vertebrae fracture prediction.

International audience; Purpose It was hypothesized in this in-vitro study that positioning a K-wire intersecting the cutting plane at the theoretical lateral hinge location would limit the cut depth and help preserve the lateral hinge during the opening of the osteotomy. Objectives were (1) to compare the mechanical resistance of the hinge and the protective effect of leaving the K-wire during the opening procedure (2) to check if the K-wire would limit the depth of the osteotomy.Methods An ex-vivo mechanical study, testing 5 pairs of fresh-frozen tibias, was designed. CT-scan based Patientspecific cutting guides were obtained to define the cutting plane and the location of the K-wire at the hinge, using standardized 3D planning protocol. In each pair, OWHTO was performed either with or without the K-wire. To evaluate the hinge's resistance to fracture, the specimens were rigidly fixed at the proximal tibia and a direct load was applied on the free tibial diaphysis to open the osteotomy. The maximum load at breakage, maximum permissible displacement and maximal angulation of the osteotomy before hinge failure was measured. To assess the preservation of an unscathed hinge (protected by the K-wire), the distance from the end of the osteotomy cut to the lateral tibial cortical was measured in mm.Results The maximum load to hinge breakage in the K-wires PsCG knees compared to the control group (48.3 N vs 5.5 N, p = 0.004), the maximum permissible displacement (19.8 mm vs 7.5 mm, p = 0.005) and the maximal angulation of the osteotomy before hinge breakage (9.9° vs 2.9°, p = 0.002) were all statistically superior in the K-wires PsCG knees compared to the control group. A mean distance of 10 ± 1 mm between cut-bone (saw-print) and lateral hinge cortical bone was found post-performing the osteotomy and the hinge failing.Conclusion The maximum load to breakage and the maximum permissible displacement were, respectively, 880% and 260% higher during the opening of the OWHTO in using K-wires compared to the non-K-wire control group. This confirms the mechanical advantage of using a K-wire for both stabilization and protecting the Hinge during OWHTO. This comparative cadaveric study shows an improvement of the lateral hinges resistance to failing during the opening of the osteotomy. This can be achieved by the placement of a K-wire intersecting the cutting plane at the theoretical location of the lateral hinge.

International audience; Increasing use of patient-specific surgical procedures in orthopaedics means that patient-specific anatomical coordinate systems (ACSs) need to be determined. For knee bones, automatic algorithms constructing ACSs exist and are assumed to be more reliable than manual methods, although both approaches are based on non-unique numerical reconstructions of true bone geometries. Furthermore, determining the best algorithms is difficult, as algorithms are evaluated on different datasets. Thus, in this study, we developed 3 algorithms, each with 3 variants, and compared them with 5 from the literature on a dataset comprising 24 lower-limb CT-scans. To evaluate algorithms’ sensitivity to the operator-dependent reconstruction procedure, the tibia, patella and femur of each CT-scan were each reconstructed once by three different operators.Our algorithms use principal inertia axis (PIA), cross-sectional area, surface normal orientations and curvature data to identify the bone region underneath articular surfaces (ASs). Then geometric primitives are fitted to ASs, and the ACSs are constructed from the geometric primitive points and/or axes. For each bone type, the algorithm displaying the least inter-operator variability is identified. The best femur algorithm fits a cylinder to posterior condyle ASs and a sphere to the femoral head, average axis deviations: 0.12°, position differences: 0.20 mm. The best patella algorithm identifies the AS PIAs, average axis deviations: 0.91°, position differences: 0.19 mm. The best tibia algorithm finds the ankle AS center and the 1st PIA of a layer around a plane fitted to condyle ASs, average axis deviations: 0.38°, position differences: 0.27 mm.

International audience; Background: Malrotation of the femur is a frequent complication in the management of a diaphyseal fracture. It is often responsible for pain and adverse functional results. Among these complications, contact stress effects on the patellofemoral joint are recognized as predictive factors of impaired results. The purpose of this study was to analyze the effect of malrotation on stress distribution on the patellofemoral joint, using radiological measurement and three-dimensional finite element models. Methods: Functional analysis of the patellofemoral joint was evaluated in eight knee pairs from patients with unilateral femoral fractures and subsequent femoral malrotation. A computed tomography-based protocol allowed patellofemoral joint analysis. A finite element model of the healthy (contralateral) knee was then created from 3D reconstruction at 30 flexion. In a finite element model, incremental rotational malalignment was simulated to observe changes in stress distribution on the patellar surface. Results: Femoral malrotation was associated with anomalies of patellofemoral joint rotational alignment. Internal rotation resulted in increased stress on the lateral side of the patella, and external rotation increased inferior medial side stress. Conclusions: Rotational disorders of the distal femur resulted in increased stress on the patellofemoral joint and alignment changes. Malrotation in internal and external rotation might cause patellofemoral pain syndrome from rotations

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International audience; This protocol describes the use of a newly developed external fixator for distraction osteogenesis in a rat femoral model. Distraction osteogenesis (DO) is a surgical technique leading to bone regeneration after an osteotomy. The osteotomized extremities are moved away from each other by gradual distraction to reach the desired elongation. This procedure is widely used in humans for lower and upper limb lengthening, treatment after a bone nonunion, or the regeneration of a bone defect following surgery for bone tumor excision, as well as in maxillofacial reconstruction. Only a few studies clearly demonstrate the efficiency of their protocol in obtaining a functional regenerated bone, i.e., bone that will support physiological weight-bearing without fracture after removal of the external fixator. Moreover, protocols for DO vary and reproducibility is limited by lack of information, making comparison between studies difficult. The aim of this study was to develop a reproducible protocol comprising an appropriate external fixator design for rat limb lengthening, with a detailed surgical technique that permits physiological weight-bearing by the animal after removal of the external fixator.

Background Fracture risk prediction in patient relies chiefly on bone mineral density (BMD) measurement. However, the decreased bone strength characteristic of osteoporosis is dependent not only on BMD, but also on other factors, most notably bone microarchitecture. Objectives The purpose of this study was to investigate bone microarchitecture variables of cadaveric vertebrae using ultra-high field MRI (7 Tesla). Methods Twenty four vertebrae (L2, L3, L4) from eight cadavers were studied using 7 Tesla MRI. Their Bone Mineral Density (BMD) were investigated using dual energy X Ray absorptiometry. Then, all specimens underwent mechanical compression tests to failure and the failure load (in Newton) and constraint (in Mpa) were measured. Bone Volume Fraction (BV/TV), Trabecular Thickness (Tb.Th), and Trabecular Spacing (Tb.Sp) were measured in MR images using a Digital topological analysis (Bone J). Measurements were performed by two observators in order to characterize the inter-rater reliability. Statistical analyses were performed using SPSS. Correlations between variables were analyzed using Spearman correlations and Stepwise regression. A p value of 0.05 was considered as significant. Results The inter-rater reliability for bone microarchitecture parameters quantification was good. Tb.Th and Tb.Sp measured using high-field MRI were 0.52±0.18 and 0.48±0.10 respectively while the BV/TV fraction was 0.52±0.13. The mean BMD was 0.86±0.20 g/cm2. The failure load and the constraint measured during the compression tests were 2600±1267N and 1.57±0.81 Mpa respectively. Interestingly, the variables measured during the mechanical tests were significantly The failure load and constraint measured during the compression tests were significantly correlated with the BMD. Regarding the bone indices quantified using high-field MRI, a significant linear relationship was observed between the trabecular spacing and the BMD (R2=0.23, p=0.01 and the constraint values to failure (R2=0.18, p=0.04). A stepwise regression with backward elimination demonstrated that combining BV/TV and BMD improved the relationship with the constraints from an adjusted R2=0.384 for BMD alone to an adjusted R2=0.41 for BMD + BV/TV. Conclusions In the present study, we demonstrated for the first time that the variables characterizing the vertebral bone microarchitecture quantified using ultra-high field MRI were significantly correlated with biomechanical parameters. In addition, we illustrated that the vertebral bone strength was better described by a variable combining BMD and trabecular bone spacing. Disclosure of Interest None declared

International audience; The function of the hip labrum during hip motion remains poorly known. Our hypothesis was that acetabular labrum will deform and change its shape during adduction to abduction movement consecutively to variation of strains passing from the acetabulum to the femoral head. An ex vivo anatomical study was conducted to analyse the morphological parameters variation of the mid-portion of the labrum (length, thickness, shape, deformation) as well as femoro-labral strains during hip adduction to abduction movement. Ten fresh-frozen, unpaired human cadaver hemi-pelvises were obtained. To best approximate the clinical reality, fresh-frozen cadaver tissues were utilized. The hemi-pelvises were split sagittally in two equal parts through a plane crossing the femoral neck and femoral head centres. The hemi-pelvises were rigidly mounted on a test platform using a custom-made fixture, and a seven hundred Newton load was applied through the iliac wing, with a unidirectional movement (adduction/abduction) of the acetabulum above the fixed femur. Variations of strain passing from the labrum to the femoral head or neck were analysed using captors fixed on the acetabular edge. From 20A degrees to 40A degrees of abduction labral length decreased from a median of 5.8 (5.5-6.4 mm) to 4.6 (4-5.4 mm), labral edge angle increased from a median of 33.1 (31.1A degrees-40A degrees) to 52.3 (41.4A degrees-58.8A degrees), labral sectional area decreased from a median of 22.1 (17-27.1 mm(2)) to 14.2 (12-16.8 mm(2)) all p = 0.001. Femoro-labral strains were maximal at 40A degrees of abduction [median 0.1 N mm(-2) (0.1-3.1 N mm(-2))] and minimal at 30A degrees adduction (median 0 N mm(-2) (0-0.1 N mm(-2)) and p = 0.001). The morphological variations of the mid-portion of the labrum during hip motion reflect strains passing from the labrum to the femoral head. Those elements may provide clues to understand the mechanical role of the labrum during abduction. The acetabular labrum bears a direct mechanical role during hip motion, thus resecting the hip's labrum during surgery might be detrimental for hip joint's biomechanics as it might modify strains distribution between the acetabulum and femur.

Links between sagittal spinal alignment and acetabular orientation attract considerable research attention with the goal of optimising prosthetic cup position. However, whether pelvic incidence (PI) is related to anatomic acetabular orientation remains unknown. We therefore conducted a radiological study with the following objectives: to look for correlations between PI and anatomic acetabular parameters; to describe the sacro-pubic angle (SPA), defined by fixed bony pelvic landmarks, and its relations with acetabular anteversion; and to determine whether anatomical parameters (PI and SPA) correlate with demographic characteristics.PI correlates with anatomical acetabular parameters.We conducted a computed tomography (CT) study of the pelvises of 150 patients free of degenerative disease. Three parameters were measured: anatomic acetabular orientation in the Lewinnek reference plane, PI, and the SPA subtended by the line connecting the midpoint of the sacral endplate to the pubic symphysis and the anterior pelvic plane. Statistical tests were performed to look for correlations among these parameters.Intra-observer and inter-observer reproducibility was considered highly satisfactory (inter-class correlation coefficient,86% and82%, respectively). Mean PI was 58.6°±10.2° (range, 32.8°-97.6°), with no significant differences between genders or across age groups. Mean SPA was 34.7°±5.5° (range, 18.3°-49.8°). Mean anatomic acetabular anteversion (AAA) was greater in females (23.4°; range, 11.5°-34.5°) than in males (20°; range, 7.5°-34.5°) (P0.001). PI did not correlate with any of the acetabular parameters (PI/AAA, r=0.8 and P=0.33; PI/acetabular inclination on the horizontal, r=-0.96 and P=0.24). SPA correlated significantly with both PI (r=0.33 and P0.001) and AAA (r=0.33 and P0.001).This CT study of normal pelvises showed that AAA was significantly greater in females and that SPA correlated significantly with both PI and acetabular anteversion. SPA could serve to define the "theoretical" AAA of each individual patient and could thus be incorporated into surgical planning protocols or intra-operative guidance methods for hip replacement surgery.IV, retrospective study with no control group.

International audience; Additive manufacturing methods provide an increasingly popular industrial means of producing complex mechanical parts when classical methods are not suitable. The main advantage of these methods is the great freedom they give designers. At the same time, theoretical and numerical topology optimization tools can be used to simulate structures with complex shapes which exactly meet the mechanical constraints while requiring as little material as possible. Combining topology optimization and additive production procedures therefore seems to be a promising approach for obtaining optimized mechanical parts. Nonetheless structures obtained via topology optimization are composed of parts of composite densities which can not produced via additive manufacturing. Only numerical structures made of full or empty spaces only can be produced by additive methods. This can be obtained at the end of computational optimization through a penalization step which gives the composite densities from 0 to 1 the values 0 or 1. This means that the final part is different from the best solution predicted by topology optimization calculations. It therefore seemed to be worth checking the validity of an engineering approach in which additive methods are used to manufacture structures based on the use of industrial topology optimization codes. Here the authors propose to study, in the case of a simple mechanical problem, that of a metal cube subjected to a given pressure, three procedures, which differed in terms of the code and type of topology optimization calculations performed and the level of penalization applied. The three structures thus obtained were then produced using additive methods. Since all three structures proved to be mechanically resistant, the three procedures used can be said to be valid. However, one of them yielded better compromise between the mechanical strength and the amount of material saved. (C) 2017 The Society of Manufacturing Engineers. Published by Elsevier Ltd. All rights reserved.

International audience; IntroductionTreatment of medial tibiofemoral osteoarthritis with a high-tibial osteotomy (HTO) is most effective when the optimal angular correction is achieved. However, conventional instrumentation is limited when multiplanar correction is needed.HypothesisUse of patient-specific cutting guides (PSCGs) for HTO provides an accurate correction (difference < 2°) relative to the preoperative planning.Materials and methodsBetween February 2014 and February 2015, 10 patients (mean age: 46 years [range: 31–59]; grade 1 or 2 osteoarthritis in Ahlbäck's classification) were included prospectively in this reliability and safety study. All patients were operated using the same medial opening-wedge osteotomy technique. Preoperative planning was based on long-leg radiographs and CT scans with 3D reconstruction. The PSGCs were used to align the osteotomy cut and position the screw holes for the plate. The desired correction was achieved in the three planes when the holes on the plate were aligned with the holes drilled based on the PSCG. Preoperatively, the mean HKA angle was 171.9° (range: 166–179°), the mean proximal tibial angle was 87° (86–88°) and the mean tibial slope was 7.8° (1–22°). The postoperative correction was compared to the planned correction using 3D CT scan transformations. Intraoperative and postoperative complications were assessed at a minimum follow-up of 1 year.ResultsThe procedure was successfully carried out in all patients with the PSCGs. On postoperative long-leg radiographs, the mean HKA was 182.3° (180–185°); on the CT scan, the mean tibial mechanical angle was 94° (90–98°) and the mean tibial slope was 7.1° (4–11°). In 19 out of 20 postoperative HKA and slope measurements, the difference between the planned and achieved correction was < 2° based on the 3D analysis of the three planes in space; in the other case, the slope was 13° instead of the planned 10°. The intra-class correlation coefficients between the postoperative and planned parameters were 0.98 [0.92–0.99] for the HKA and 0.96 [0.79–0.99] for the tibial slope. There were no surgical site infections; one patient had a postoperative hematoma that resolved spontaneously.DiscussionThe results of this study showed that use of PSCGs in HTO procedures helps to achieve optimal correction in a safe and reliable manner.Level of evidenceIV – Prospective cohort study.Keywords: Medial tibiofemoral osteoarthritis, High tibial osteotomy, Opening-wedge osteotomy, Patient-specific surgical guides, 3D printing

International audience; Introduction: Kinematic alignment (KA) technique is an alternative technique for positioning a TKA, which aims a patient-specific implant positioning in order to reproduce the pre-arthritic knee anatomy. Because reliability in implant positioning is of interest to obtain reproducible good functional results, our study tests the hypothesis that the medial and lateral distal and posterior positions of the planned and surgically implanted kinematically aligned femoral component are similar. Methods: Preoperative knee magnetic resonance imaging (MRI) and postoperative knee computed tomography (CT) of 13 patients implanted with a KA Persona TKA (Zimmer, Warsaw, USA) using manual instrumentation (kinematically-aligned TKA procedure pack, Zimmer Biomet, Warsaw, USA) were segmented to create 3D femoral models. The kinematic alignment position of the femoral component was planned on the 3D model created from the preoperative MRI. Differences in the positions of the planned and surgically implanted kinematically-aligned femoral component were determined with in-house analysis software. Results: The average differences between the medial and lateral distal and posterior positions of the planned and surgically implanted kinematically-aligned femoral component were inferior to 1mm and no statistically significant. In terms of variability, 62% (8/13) of performed implants matched all four positions within 1.5mm, and the maximum difference was 3mm. Conclusion: In this small series, intraoperative kinematic positioning of the femoral component with the specific manual instrumentation closely matched the planned position, which suggests that this technique reliably aligned the flexion-extension axis of the femoral component to the cylindrical axis. (C) 2017 Elsevier Masson SAS. All rights reserved.

STUDY DESIGN High-resolution imaging and biomechanical investigation of ex-vivo vertebrae. OBJECTIVE The aim of this study was to assess bone microarchitecture of cadaveric vertebrae using ultra-high field (UHF) 7 Tesla magnetic resonance imaging (MRI) and to determine whether the corresponding microarchitecture parameters were related to bone mineral density (BMD) and bone strength assessed by dual-energy x-ray absorptiometry (DXA) and mechanical compression tests. SUMMARY OF BACKGROUND DATA Limitations of DXA for the assessment of bone fragility and osteoporosis have been recognized and criteria of microarchitecture alteration have been included in the definition of osteoporosis. Although vertebral fracture is the most common osteoporotic fracture, no study has assessed directly vertebral trabecular bone microarchitecture. METHODS BMD of 24 vertebrae (L2, L3, L4) from eight cadavers was investigated using DXA. The bone volume fraction (BVF), trabecular thickness (Tb.Th), and trabecular spacing (Tb.Sp) of each vertebra were quantified using UHF MRI. Measurements were performed by two operators to characterize the inter-rater reliability. The whole set of specimens underwent mechanical compression tests to failure and the corresponding failure stress was calculated. RESULTS The inter-rater reliability for bone microarchitecture parameters was good with intraclass correlation coefficients ranging from 0.82 to 0.94. Failure load and stress were significantly correlated with BVF, Tb.Sp, and BMD (P

International audience; Background: For over a decade, computer-assisted orthopaedic surgery for total knee arthroplasty has been accepted as ensuring accurate implant alignment in the coronal plane. Hypothesis: We hypothesised that lack of accuracy in skeletal landmark identification during the acquisition phase and/or measurement variability of the infrared optical system may limit the validity of the numerical information used to guide the surgical procedure. Methods: We built a geometric model of a navigation system, with no preoperative image acquisition, to simulate the stages of the acquisition process. Random positions of each optical reflector center and anatomic acquisition point were generated within a sphere of predefined diameter. Based on the virtual geometric model and navigation process, we obtained 30,000 simulations using the Monte Carlo statistical method then computed the variability of the anatomic reference frames used to guide the bone cuts. Rotational variability (a, b, g) of the femoral and tibial landmarks reflected implant positioning errors in flexion-extension, valgus-varus, and rotation, respectively. Results: Taking into account the uncertainties pertaining to the 3D infrared optical measurement system and to anatomic point acquisition, the femoral and tibial landmarks exhibited maximal alpha (flexion-extension), beta (valgus-varus), and gamma (axial rotation) errors of 1.65 • (0.9 •); 1.51 • (0,98 •), and 2.37 • (3.84 •), respectively. Variability of the infrared optical measurement system had no significant influence on femoro-tibial alignment angles. Conclusion: The results of a Monte Carlo simulation indicate a certain level of vulnerability of navigation systems for guiding position in rotation, contrasting with robustness for guiding sagittal and coronal alignments. Level of evidence: Level IV.

Resume Introduction Dans l’arthroplastie totale de genou, la chirurgie assistee par ordinateur se definit depuis plus de 10 ans comme l’outil de precision pour aligner les implants dans le plan frontal. Notre hypothese a ete qu’une imprecision sur les reperes squelettiques pendant la phase d’acquisition et/ou une variabilite de mesure du systeme optique infrarouge pouvaient remettre en question la pertinence des informations numeriques qui guident le geste operatoire. Materiel et methode Une modelisation geometrique d’un systeme de navigation, sans acquisition d’imagerie preoperatoire, a permis de simuler les etapes du processus d’acquisition. Le centre de chaque reflecteur optique et les points anatomiques d’acquisition ont ete bruites aleatoirement de maniere multidirectionnelle dans une sphere d’incertitude dont le diametre a ete prealablement fixe. Trente mille simulations realisees selon la methode statistique de Monte-Carlo ont permis a partir du modele geometrique virtuel et du processus de navigation de calculer la variabilite des referentiels anatomiques qui guident les coupes osseuses. Les variabilites en rotation (α, β et γ) des reperes squelettiques femoral et tibial ont traduit respectivement les erreurs de positionnement des implants en flexion–extension, valgus–varus et rotation. Resultats En considerant les incertitudes du systeme de mesure optique infrarouge 3D et de l’acquisition des points anatomiques, les reperes femoral et tibial ont montre une erreur maximale alpha (flexion–extension), beta (valgus–varus) et gamma (rotation axiale) respectivement de 1,65° (0,9°) ; 1,51° (0,98°) et 2,37° (3,84°). La variabilite du systeme de mesure optique infrarouge n’a pas eu d’influence significative sur les angles d’alignement femoro-tibiaux. Conclusion Sur la base d’une simulation de Monte-Carlo, les systemes de navigation demontrent une certaine vulnerabilite pour le guidage en rotation mais une robustesse pour le controle de l’alignement frontal et coronal. Niveau de preuve de l’etude IV.

Introduction L’interface fil/tendon reste la faiblesse lors de la reparation arthroscopique d’une rupture de la coiffe des rotateurs. Le point de Mason Allen (MA) arthroscopique a une resistance biomecanique a l’arrachement superieure. Cependant, il s’agit d’une reparation uniquement « simple rang ». Les objectifs de notre etude etaient : de decrire une technique arthroscopique d’un point de MA avec ancrage osseux double rang simple et reproductible et d’evaluer la resistance a l’arrachement de l’interface fil/tendon par rapport a une reparation double rang. L’hypothese de notre etude etait que la suture par un point de Mason Allen avait, in vitro, une resistance a l’arrachement superieure a celle d’un point classique de reference, a l’interface fil/tendon. Materiels et methode Une etude biomecanique in vitro sur tendons d’agneaux avec epreuve de traction uniaxiale a ete realisee. Chaque point etait realise et teste a partir d’un meme tendon. Les 2 points etaient realises par le meme operateur, dans des conditions similaires a l’arthroscopie. Les parametres mesures etaient la resistance a la traction (force a la rupture en Newton) et la cause de l’echec. Resultat Nous avons realise 30 essais de traction uniaxiale a l’aide d’une machine d’essai Instron 5566. Les causes d’arret du test etaient un lâchage au niveau de l’interface fil/tendon pour tous les essais. Le point de MA avait une resistance a l’arrachement superieure a celle du point de reference (61,0 ± 14,9 N vs 50,3 ± 15,0 N ; p = 0,001). Conclusion In vitro, le point de MA avec ancrage osseux double rang a une resistance a l’arrachement superieure a celle d’un point de reference double rang. Cette etude constitue une experimentation preliminaire pour l’utilisation de ce point dans la reparation de rupture de la coiffe des rotateurs sous-arthroscopie. Une approche clinique est necessaire afin d’evaluer la stabilite a long terme de ce point, apres reeducation.