Outcomes of Short and Long Tibial Stems for Primary Total Knee Arthroplasty in a Population of Obese Patients at Two-Year Follow-Up: A Clinical and Biomechanical Study.

BACKGROUND: Obesity can be a source of higher failure rates and inferior clinical outcomes after total knee arthroplasty (TKA). The aim of this study was to compare outcomes, failure rates, and stress distributions of TKA in obese patients using a short, long, or no tibial stem. METHODS: A matching process based on the type of stem used and the age allowed included 180 patients who had a body mass index (BMI) > 30 and underwent a TKA between January 2010 and December 2019, with a minimum follow-up of 2 years. They were classified as moderately obese (MO: 30 < BMI < 35, N = 90) and severely obese (SO: BMI > 35, N = 90). For each, 3 subgroups were defined: thirty patients received a 30 mm short stem (SS), thirty received a 100 mm long stem (LS), and thirty received no stem (NS). Patients were assessed preoperatively and postoperatively using the Knee Society Score (KSS). A finite element model was developed to evaluate the biomechanical effects of the tibial stem on stress distribution in the subchondral bone based on BMI. RESULTS: The SS patients had significantly higher postoperative KSS knee score [MO: 88.9 (SS) versus 79 (LS) versus 80.6 (NS); SO: 84.5 versus 72.4 versus 78.2] (P < .0001) and function score [MO: 90.4 (SS) versus 78.4 (LS) versus 68.5 (NS); SO: 85.5 versus 73 versus 61.8] (P < .0001) compared to LS and NS patients. The biomechanical study demonstrated a BMI-dependent increase in stress in the subchondral bone in contact with the tibial components. These stresses were mainly distributed at the tibial cut for NS and along the stem for SS and LS. CONCLUSIONS: A short, cemented tibial stem offers better functional outcomes without increasing failure rates compared to a longer stem during primary TKA in a population of obese patients at two-year follow-up. A short tibial stem does not lead to increased stress compared to an LS, at least for certain BMI categories.

Osteochondral autograft transplantation (mosaicplasty): What is the impact of plug diameter in cartilage repair?

PURPOSE: To compare the mechanical stress applied to our grafted defect area according to the diameter of the plugs used in the treatment of osteochondral lesion with osteochondral autograft transplantation (OAT) procedure. METHODS: A biomechanical study was conducted on eight cadaveric knees. A 20-mm defect was created in the weight-bearing zone on the medial femoral condyle then filled either with three plugs of 8 mm, or with four plugs of 6 mm, or with 6 plugs of 4 mm diameter. After the preparation of the specimens, each knee was installed on a mechanical test bench (Instron 5566A). A continuous axial compression of 700 N at 10 mm.min-1 was exerted on the joint. A K-scan 4000-type pressure sheet was used to record the contact area (mm2), the mean pressure (MPa), and the maximum pressure (MPa) on the area of interest. RESULTS: The differences found between the conditions were not statistically significant but showed tendencies. Filling the defect with six plugs of 4 mm restores a larger contact surface compared with the other plugs. The use of 8- and 6-mm grafts lead to a respective increase of 12% and 52% of the mean pressure compared with the 4 mm grafts. This difference was also found for the maximum pressure (36% and 129%). Regardless of the diameter of the plugs used, filling the lesion reduces the mean pressure exerted on the healthy cartilage by 19%. DISCUSSION: A trend emerged towards a better restoration of the cartilage surface and a more harmonious distribution of the pressures exerted in favour of the grafts of smaller diameter. A larger study is needed to obtain a statistically significant result.

Local tissue effects and peri-implant bone healing induced by implant surface treatment: an in vivo study in the sheep.

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 with 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, was 79.3 ± 11.2% and 86.4 ± 6.7%, compared with the untreated implants (68.3 ± 8.8% and 74.8 ± 13%). Micro-computed tomography analyses revealed that healing patterns differed between coronal and apical regions, with higher coronal bone-to-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.

Adding a protective K-wire during opening high tibial osteotomy increases lateral hinge resistance to fracture.

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 Patient-specific 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.

Mechanical strains passing through the acetabular labrum modify its shape during hip motion: an anatomical study.

PURPOSE: 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. METHODS: 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. RESULTS: From 20° to 40° 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 (31.1°-40°) to 52.3 (41.4°-58.8°), labral sectional area decreased from a median of 22.1 (17-27.1 mm2) to 14.2 (12-16.8 mm2) all p = 0.001. Femoro-labral strains were maximal at 40° of abduction [median 0.1 N mm-2 (0.1-3.1 N mm-2)] and minimal at 30° adduction (median 0 N mm-2 (0-0.1 N mm-2) and p = 0.001). CONCLUSION: 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.

Chemotherapy and adjuvant therapies' impact on the internal remodeling process of bone and its mechanical behavior for breast cancer patients.

Breast cancer is a significant public health issue affecting women worldwide. While advancements in treatment options have led to improved survival rates, the impact of breast cancer and its treatments on bone health cannot be overlooked. Bone remodeling is a complex process regulated by the delicate balance between bone formation and resorption. Any disruption to this balance can lead to decreased bone density, increased fracture risk, and compromised physical function. To investigate the effects of breast cancer and its treatments on bone remodeling, a finite element model was developed in this study. This model incorporated bone remodeling equations to simulate the mechanical behavior of bone under different conditions. The ABAQUS/UMAT software was used to simulate the behavior of bone tissue under the influence of breast cancer and treatments. Our findings suggest that bone loss is more pronounced after secondary breast cancer and treatment, leading to bone loss (6%-19% decrease in BV/TV), reduced bone stimulation, and decreased effectiveness of physical activity on recovery. These results highlight the importance of early intervention and management of bone health in breast cancer patients to mitigate the negative impact of cancer and treatment on bone remodeling.

Acute compartment syndrome of the lower limbs: Fasciotomy or dermofasciotomy? A cadaver study of compartment pressures.

BACKGROUND: Acute compartment syndrome (ACS) of the lower limbs is a function-threatening event usually managed by extended dermofasciotomy. Closure of the skin may be delayed, creating a risk of complications when there is an underlying fracture. Early treatment at the pre-ACS stage might allow isolated fasciotomy with no skin incision. The primary objective of this study was to compare intracompartmental pressure (ICP) changes after fasciotomy and after dermofasciotomy. The secondary objectives were to evaluate potential associations linking the starting ICP to achievement of an ICP below the physiological cut-off of 10mm Hg and to determine whether the ICP changes after fasciotomy and dermofasciotomy varied across muscle compartments. HYPOTHESIS: Fasciotomy with no skin incision may not provide a sufficient ICP decrease, depending on the initial ICP value. MATERIAL AND METHODS: A previously validated model of cadaver ACS of the lower limbs was used. Saline was injected gradually to raise the ICP to>15mmHg (ICP15), >30mmHg (ICP30), and >50mmHg (ICP50). We studied 70 leg compartments (anterior, lateral, and superficial posterior) in 13 cadavers (mean age, 89.1±4.6years). ICP was monitored continuously. Percutaneous, minimally invasive fasciotomy consisting in one to three 1-cm incisions was performed in each compartment. ICP was measured before and after fasciotomy then after subsequent skin incision. The objective was to decrease the ICP below 10mmHg after fasciotomy or dermofasciotomy. RESULTS: Overall, mean ICP was 37.8±19.1mmHg after the injection of 184.0±133.01mL of saline. In the ICP15 group, the mean ICP of 16.1mmHg fell to 1.4mmHg after fasciotomy (ΔF=14.7) and 0.3mmHg after dermofasciotomy (ΔDF=1.1). Corresponding values in the ICP30 group were 33.9mmHg, 4.7mmHg (ΔF=29.2), and 1.2mmHg (ΔDF=3.5); and in the ICP50 group, 63.7mmHg, 17.0mmHg (ΔF=46.7), and 1.2mmHg (ΔDF=15.8). Thus, in the group with initial pressures >50mmHg, the ICP decrease was greater after both procedures, but fasciotomy alone nonetheless failed to achieve physiological values (<10mmHg). The pressure changes were not significantly associated with the compartment involved (anterior, lateral, or superficial posterior) (p<0.05). CONCLUSION: Under the conditions of this study, higher baseline ICPs were associated with larger ICP drops after fasciotomy and dermofasciotomy. Nevertheless, when the baseline ICP exceeded 50mmHg, fasciotomy alone failed to decrease the ICP below 10mmHg. Adding a skin incision achieved this goal. LEVEL OF EVIDENCE: IV, experimental study.

An Evaluation of the Reliability of Manual Landmark Identification on 3D Segmented Wrists.

BACKGROUND: Three-dimensional (3D) preoperative planning is increasingly used in orthopaedic surgery. Two-dimensional (2D) characterization of distal radial deformities remains inaccurate, and 3D planning requires a reliable reference frame at the wrist. We aim to evaluate the reliability of the determination of anatomical points placed manually on 3D models of the radius to determine which of those points allow reliable morphometric measurements. METHODS: Twenty-three radial scans were reconstructed in 3D. Five operators specialized in the upper limb manually positioned 8 anatomical points on each model. One of the operators repeated the operation 6 times. The anatomical points were based on previously published 3D models used for radial inclination and dorsopalmar tilt measurements. The repeatability and reproducibility of the measurements derived using this manual landmarking were calculated using different measurement methods based on the identified points. An error of ≤2° was considered clinically acceptable. RESULTS: This study of intraobserver and interobserver variability of the anatomic points allowed us to determine the least variable and most accurately defined points. The middle of the ulnar border of the radius, the radial styloid, and the midpoint of the ulnar incisura of the radius were the least variable. The palmar and dorsal ends of the ridge delineating the scaphoid and lunate facets were the most variable. Only 1 of the radial inclination measurement methods was clinically acceptable; the others had a repeatability and reproducibility limit of >2°, making those measurements clinically unacceptable. CONCLUSIONS: The use of isolated points seems insufficient for the development of a wrist reference frame, especially for the purpose of measuring dorsopalmar tilt. If one concurs that an error of 2° is unacceptable for all distal radial measurements, then clinicians should avoid using 3D landmarked points, due to their unreliability, except for radial inclination measured using the radial styloid and the midpoint of the ulnar edge of the radius. A characterization of the wrist using 3D shapes that fit the articular surface of the radius should be considered. LEVEL OF EVIDENCE: Diagnostic Level III . See Instructions for Authors for a complete description of levels of evidence.

Computational model combined with in vitro experiments to analyse mechanotransduction during mesenchymal stem cell adhesion.

The shape that stem cells reach at the end of adhesion process influences their differentiation. Rearrangement of cytoskeleton and modification of intracellular tension may activate mechanotransduction pathways controlling cell commitment. In the present study, the mechanical signals involved in cell adhesion were computed in in vitro stem cells of different shapes using a single cell model, the so-called Cytoskeleton Divided Medium (CDM) model. In the CDM model, the filamentous cytoskeleton and nucleoskeleton networks were represented as a mechanical system of multiple tensile and compressive interactions between the nodes of a divided medium. The results showed that intracellular tonus, focal adhesion forces as well as nuclear deformation increased with cell spreading. The cell model was also implemented to simulate the adhesion process of a cell that spreads on protein-coated substrate by emitting filopodia and creating new distant focal adhesion points. As a result, the cell model predicted cytoskeleton reorganisation and reinforcement during cell spreading. The present model quantitatively computed the evolution of certain elements of mechanotransduction and may be a powerful tool for understanding cell mechanobiology and designing biomaterials with specific surface properties to control cell adhesion and differentiation.

Bone texture analysis is correlated with three-dimensional microarchitecture and mechanical properties of trabecular bone in osteoporotic femurs.

Fracture of the proximal femur is a major public health problem in elderly persons. It has recently been suggested that combining texture analysis and bone mineral density measurement improves the failure load prediction in human femurs. In this study, we aimed to compare bone texture analysis with three-dimensional (3D) microarchitecture and mechanical properties of trabecular bone in osteoporotic femurs. Eight femoral heads from osteoporotic patients who fractured their femoral neck provided 31 bone cores. Bone samples were studied using a new high-resolution digital X-ray device (BMA™, D3A Medical Systems) allowing for texture analysis with fractal parameter H (mean), and were examined using micro-computed tomography (microCT) for 3D microarchitecture. Finally, uniaxial compression tests to failure were performed to estimate failure load and apparent modulus of bone samples. The fractal parameter H (mean) was strongly correlated with bone volume fraction (BV/TV) (r = 0.84) and trabecular thickness (Tb.Th) (r = 0.91) (p < 0.01). H (mean) was also markedly correlated with failure load (r = 0.84) and apparent modulus (r = 0.71) of core samples (p < 0.01). Bone volume fraction (BV/TV) and trabecular thickness (Tb.Th) demonstrated significant correlations with failure load (r = 0.85 and 0.72, respectively) and apparent modulus (r = 0.72 and 0.64, respectively) (p < 0.01). Overall, the best predictors of failure load were H (mean), bone volume fraction, and trabecular thickness, with r (2) coefficients of 0.83, 0.76, and 0.80 respectively. This study shows that the fractal parameter H (mean) is correlated with 3D microCT parameters and mechanical properties of femoral head bone samples, which suggests that radiographic texture analysis is a suitable approach for trabecular bone microarchitecture assessment in osteoporotic femurs.

Pullout strength of all suture anchors in the repair of rotator cuff tears: a biomechanical study.

PURPOSE: We evaluated the biomechanical strength of two all suture anchors (ASA) of reduced diameter (1.4 mm) and compared them with the standard screw anchor (SA) with larger diameter (5.5 mm) used in rotator cuff tears. METHODS: We conducted 30 uniaxial vertical pullout tests using Material Testing System Instron 5566A until failure of the anchorage defined as rupture of the threads or anchor or detachment of the anchor. Anchor fixation was on tuberosities of fresh bovine humerus bone. ASAs were spaced four millimetres apart and were compared with a control SA implanted on the same greater tubercle at two centimetres. The tests were all performed at room temperature in a dry environment. Tensile loads (10 mm/min) were applied parallel to the axis of insertion. A preloading of 10 N was used to overcome loading artifacts of the test sample at the beginning of the test. RESULTS: Student's t test showed no statistically significant difference between anchors in terms of load to failure (ASA: force 265.06 ± 87.25 N versus SA : 325.35 ± 113.46 N; p = 0.09) and mean elongation at rupture (ASA : 23 ± 7 mm versus SA : 21 ± 6 mm; p = 0.46). CONCLUSIONS: In vitro, this experimental study showed no statistically significant difference in pullout strength and displacement between ASA and SA at a chosen level of significance (p < 0.05).

Three-dimensional biometrics using weight-bearing imaging shows relationship between knee and hindfoot axial alignment.

BACKGROUND: 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. HYPOTHESIS: Hindfoot alignment is correlated with femoral and tibial torsions. PATIENTS AND METHODS: 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. RESULTS: 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 R2 (3%

Modeling and simulation of bone cells dynamic behavior under the late effect of breast cancer treatments.

Breast Cancer (BC) treatments have been proven to interfere with the health of bones. Chemotherapy and endocrinal treatment regimens such as tamoxifen and aromatase inhibitors are frequently prescribed for women with BC. However, these drugs increase bone resorption and reduce the Bone Mineral Density (BMD), thus increasing the risk of bone fracture. In the current study, a mechanobiological bone remodeling model has been developed by coupling cellular activities, mechanical stimuli, and the effect of breast cancer treatments (chemotherapy, tamoxifen, and aromatase inhibitors). This model algorithm has been programmed and implemented on MATLAB software to simulate different treatment scenarios and their effects on bone remodeling and also predict the evolution of Bone Volume fraction (BV/TV) and the associated Bone Density Loss (BDL) over a period of time. The simulation results, achieved from different combinations of Breast Cancer treatments, allow the researchers to predict the intensity of each combination treatment on BV/TV and BMD. The combination of chemotherapy, tamoxifen, and aromatase inhibitors, followed by the combination of chemotherapy and tamoxifen remain the most harmful regimen. This is because they have a strong ability to induce the bone degradation which is represented by a decrease of 13.55% and 11.55% of the BV/TV value, respectively. These results were compared with the experimental studies and clinical observations which showed good agreement. The proposed model can be used by clinicians and physicians to choose the most appropriate combination of treatments, according to the patient's case.

Mechanobiological model to study the influence of screw design and surface treatment on osseointegration.

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 12 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.

Experimental-based mechanobiological modeling of the anabolic and catabolic effects of breast cancer on bone remodeling.

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.

The femoral calcar: a computed tomography anatomical study.

The femoral calcar is a dense internal septum reaching from the femoral neck to the distal part of the lesser trochanter. Our study aimed at providing an exhaustive radio-anatomical description of this structure. One hundred pelvic computed tomography examinations were retrospectively selected to bilaterally evaluate the shape, dimensions, and density of the femoral calcar. Then, its relation to the femoral cavity was assessed by recording the dimensions of the medullary canal at the level of the greatest length of the spur. The femoral calcar exhibited a variable shape classified as ridge-type 17% (34/200), spur-type 66.5% (133/200), and septum-type 16.5% (33/200). Its mean dimensions were: height = 33.03 mm (20-46), length = 9.94 mm (5-16), and thickness = 2.71 mm (1-4). These dimensions were positively correlated to the height and weight of the individuals (P < 0.001) and were higher in males (P < 0.001). Its mean density was 788.5 Hounsfield units (530-1,200). The longest oblique and anteroposterior diameters of the femoral cavity were respectively 38.74 mm (28-51) and 22.04 mm (17-27). The femoral cavity dimensions were positively correlated to the height and weight of the individuals (P < 0.001), to the femoral calcar dimensions (P < 0.001) and were higher in males (P < 0.001). The femoral calcar was constantly identified as a vertical plate of compact bone exhibiting a consistent anatomical pattern, which suggests a significant mechanical function within the upper femur. Our results may lead to a greater understanding of the hip fracture patterns and to alternative designs for hip arthroplasties.

Influence of material properties and boundary conditions on patient-specific models.

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%.

Toward a Mathematical Modeling of Diseases' Impact on Bone Remodeling: Technical Review.

A wide variety of bone diseases have hitherto been discovered, such as osteoporosis, Paget's disease, osteopetrosis, and metastatic bone disease, which are not well defined in terms of changes in biochemical and mechanobiological regulatory factors. Some of these diseases are secondary to other pathologies, including cancer, or to some clinical treatments. To better understand bone behavior and prevent its deterioration, bone biomechanics have been the subject of mathematical modeling that exponentially increased over the last years. These models are becoming increasingly complex. The current paper provides a timely and critical analysis of previously developed bone remodeling mathematical models, particularly those addressing bone diseases. Besides, mechanistic pharmacokinetic/pharmacodynamic (PK/PD) models, which englobe bone disease and its treatment's effect on bone health. Therefore, the review starts by presenting bone remodeling cycle and mathematical models describing this process, followed by introducing some bone diseases and discussing models of pathological mechanisms affecting bone, and concludes with exhibiting the available bone treatment procedures considered in the PK/PD models.

Early-stage knee OA induced by MIA and MMT compared in the murine model via histological and topographical approaches.

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.

Tibial subchondral trabecular bone micromechanical and microarchitectural properties are affected by alignment and osteoarthritis stage.

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 < 0.001). Results showed that both micromechanical and microarchitectural properties of STB are affected by macroscopic loading at late stage knee OA. For the first time, a strong association between tissue stiffness and quantity of OA STB was demonstrated.