Femoral Head Region Research Articles

Influence of age and gender on microarchitecture and bone remodeling in subchondral bone of the osteoarthritic femoral head

IntroductionAge and gender have been reported to have a remarkable impact on bone homeostasis. However, subchondral bone, which plays a pivotal role in the initiation and progression of OA, has been poorly investigated. This study was to investigate age- and gender-related changes of microarchitecture and bone remodeling in subchondral bone in OA. MethodsSubchondral trabecular bone (STB) and deeper trabecular bone (DTB) specimens were extracted in the load-bearing region of femoral heads from 110 patients with OA. Micro-CT and histomorphometry were performed to analyze microarchitectural and bone remodeling changes of all specimens. ResultsCompared to DTB, STB showed more sclerotic microarchitecture, more active bone remodeling and higher frequency of bone cysts. There were no gender differences for both microarchitecture and bone remodeling in STB. However, gender differences were found in DTB, with thinner Tb.Th, higher Tb.N, higher OS/BV and ES/BV in males. In both STB and DTB, no correlation between microarchitecture and age was found in both genders. However, bone remodeling of STB increased significantly with age in males, while bone remodeling of DTB increased significantly with age in females. No age or gender preference was found in subchondral bone cyst (SBC) frequency. The cyst volume fraction was correlated with neither age nor gender. ConclusionsThere were differences in microarchitecture and bone remodeling between STB and DTB, which may be due to the distinct biomechanical and biochemical functions of these two bone structures in maintaining joint homeostasis. OA changed the normal age- and gender-dependence of bone homeostasis in joints, in a site-specific manner.

The effect of osteoarthritis on the regional anatomical variation of subchondral trabecular bone in the femoral head

BackgroundThe subchondral trabecular bone is located deep inside the articular cartilage, with the subcapital region carrying up to 70% of the diurnal loads occurring in the hip joint. This leads to severe regional anatomical variations of subchondral trabecular bone in the femoral head and the purpose of this study was to examine whether osteoarthritis affects these topographic characteristics. Methods60 femoral heads were harvested during hip replacement and studied by osteopenetration at 8 pre-defined angles, at a penetration rate of 1mm/s. Twenty-eight of the donors underwent surgery due to osteoarthritis, whereas the remaining were trauma patients with hip fractures. To correlate these measurements to non-invasive data, all specimens were scanned by micro Computed Tomography (μCT) prior to experimentation. A cross-sectional area, perpendicular to the needle penetration pathway, was analyzed and the deviations compared to the recorded osteopenetration energy. FindingsThe experiments revealed significant topographical deviations in the trabeculae. These were more pronounced in the osteoarthritic samples which also required overall higher osteopenetration energy. A notable dependency of the directional bone strength to its cross-sectional characteristics was observed. Although the effect of “gender” on osteopenetration energy was proven to be significant, gender was not considered an independent variable in a regression model correlating osteopenetration energy to 2D trabecular bone density as this did not improve the value of the adjusted R2. InterpretationThe investigation provided refined insight into femoral head load-bearing capacity of patients suffering from osteoarthritis, as a comparison of osteoarthritic to healthy samples illustrated that subchondral trabecular bone in the femoral head region is subjected to increased remodeling and demineralization, reflected in higher osteopenetration values.

Identical subchondral bone microarchitecture pattern with increased bone resorption in rheumatoid arthritis as compared to osteoarthritis

To analyze the differences in microarchitecture and bone remodeling of subchondral bone in femoral heads from patients with rheumatoid arthritis (RA) and osteoarthritis (OA). Peri-articular bone samples, including subchondral trabecular bone (STB) and deeper trabecular bone (DTB) were extracted from the load-bearing region of femoral heads from 20 patients with RA and 40 patients with OA during hip replacement surgery. Micro-CT, histomorphometry and backscatter scanning electron microscopy (BSEM) were performed to assess microarchitecture and bone histology parameters. In both RA and OA, STB showed more sclerotic microarchitecture and more active bone remodeling, compared to DTB. RA and OA showed similar microarchitecture characteristics in both STB and DTB, despite STB in RA exhibiting higher bone resorption. In addition, there was no difference in the frequency of bone cysts in STB between RA and OA. In STB, the trabecular bone surrounding subchondral bone cysts (Cys-Tb) was more sclerotic than the trabecular bone found distant to cysts (Peri-Tb), with a higher level of bone remodeling. Both Cys-Tb region and Peri-Tb region were detected to have similar microarchitectural and bone remodeling characteristics in RA and OA. Apart from higher bone resorption in the general subchondral bone of RA samples, the peri-articular bone exhibited similar microarchitectural and bone remodeling characteristics in RA and OA.

Comparison of human and animal femoral head chondral properties and geometries

Investigations into tissue-preserving orthopaedic treatments should consider the tribology of articular cartilage; where simulations using animal joints are a predominant choice. However, very few studies have investigated the differences between human and animal cartilage. The aim of the present study was to characterise the differences in geometry and mechanical properties of human, porcine, bovine and ovine articular cartilage. Creep indentation was performed on osteochondral plugs taken from the superior region of femoral heads of all these species. Cartilage thickness was measured via the resistive force change of a needle descending through cartilage and bone. A biphasic finite element model was used to derive equilibrium elastic modulus and permeability. Results showed that human cartilage was significantly thicker than all other species tested. A positive correlation was found between femoral head diameter and cartilage thickness when comparing between species of quadrupeds. Human cartilage had the largest equilibrium elastic modulus, which was significant when comparing against porcine and bovine. However, porcine cartilage had significantly lower permeability. Significant differences in geometry and mechanical properties of articular cartilage were found between all species tested. It is necessary to consider these variations when choosing animal tissue to represent human.

Decreased Proliferation of Mesenchymal Stem Cells in Corticosteroid-induced Osteonecrosis of Femoral Head

The ability of self-repair in patients with corticosteroid-induced osteonecrosis of the femoral head is limited, and it has been suggested the cause is likely relevant to the poor proliferation activity of mesenchymal stem cells in the femoral head region. This study measured the number and proliferation activity of human mesenchymal stem cells in patients both with and without corticosteroid-induced osteonecrosis of the femoral head. Bone marrow was collected from the proximal femur in patients with steroid-induced osteonecrosis of the femoral head (osteonecrosis group, n=18) and patients with new femoral neck fractures without osteonecrosis (control group, n=11). Mesenchymal stem cells were isolated by density gradient centrifugation, and then selected by the adhesive method. The MTT reduction assay method was used to evaluate the level of proliferation. Cells from osteonecrosis patients showed reduced proliferation ability compared with the control patients. The percentage of cells in the S+G2/M phase was decreased significantly (P<.01) in the osteonecrosis group. The decreased proliferation ability of mesenchymal stem cells may play a role in the low repair capacity of steroid-induced osteonecrosis of femoral head. The altered function of mesenchymal stem cells may be responsible for the pathogenesis and progression of osteonecrosis.

Decreased Proliferation of Mesenchymal Stem Cells in Corticosteroid-Induced Osteonecrosis of Femoral Head

The ability of self-repair in patients with corticosteroid-induced osteonecrosis of the femoral head is limited, and it has been suggested the cause is likely relevant to the poor proliferation activity of mesenchymal stem cells in the femoral head region. This study measured the number and proliferation activity of human mesenchymal stem cells in patients both with and without corticosteroid-induced osteonecrosis of the femoral head. Bone marrow was collected from the proximal femur in patients with steroid-induced osteonecrosis of the femoral head (osteonecrosis group, n=18) and patients with new femoral neck fractures without osteonecrosis (control group, n=11). Mesenchymal stem cells were isolated by density gradient centrifugation, and then selected by the adhesive method. The MTT reduction assay method was used to evaluate the level of proliferation. Cells from osteonecrosis patients showed reduced proliferation ability compared with the control patients. The percentage of cells in the S+G 2 /M phase was decreased significantly ( P &lt;.01) in the osteonecrosis group. The decreased proliferation ability of mesenchymal stem cells may play a role in the low repair capacity of steroid-induced osteonecrosis of femoral head. The altered function of mesenchymal stem cells may be responsible for the pathogenesis and progression of osteonecrosis.

Regional differences in mechanical and material properties of femoral head cancellous bone in health and osteoarthritis.

Osteoarthritis (OA) is a debilitating condition common among the aging population. In this study we have determined mechanical and material properties of cancellous bone cores from two differently loaded regions of femoral heads obtained from healthy subjects and those with end-stage osteoarthritis. Densitometric properties were determined prior to compression testing for Young's modulus (EC) and yield strength (sigma(y)), after which bones were powdered for analysis of collagen and mineral content. In both OA and normal cancellous bone, volumetric bone mineral density (BMDv), apparent density (rhoA), E(C), and sigma(y) were systematically greater in the superior than in the inferior region (P<0.05). In the OA inferior region, median BMDv (0.434 g-cm(-3)) and rA (0.426 g-cm(-3)) were significantly greater than in normals (0.329 and 0.287 g-cm(-3), respectively, both P<0.05) reflecting an increased amount of tissue. The mineral:collagen ratio was decreased in OA, but this was only significant in the superior region (P<0.008). Relationships between EC and both BMDv and rho(A) were weaker in OA bone cores (r(2) = 0.66 and r(2) = 0.59) than in normals (r(2) = 0.86 and r(2) = 0.77, respectively). Likewise, sigma(y) and both BMDv and rho(A) were weaker in OA (r(2) = 0.74 and r(2) = 0.70) than in normals (r(2) = 0.83 and r(2) = 0.77, respectively). For the same value of density measure, EC and sigma(y) tended to be lower in OA bone when compared with normal bone. In conclusion, femoral head cancellous bone mass in end-stage osteoarthritis is increased but undermineralized, and is neither stiffer nor stronger than normal cancellous bone.

PET with /sup 18/F-fluoride: effects of interative versus filtered backprojection reconstruction on kinetic modeling

High focal uptake in patients poses particular problems in PET imaging. Filtered backprojection (FBP) introduces disturbing streak artifacts, adversely affecting the identification of structures and delineation of regions. Iterative reconstruction methods (MLEM) provide images of superb quality, however, the accuracy of quantitative results obtained from MLEM images has not been established for clinical data. Dynamic images were acquired over 1 hr with PET and /sup 18/F-fluoride in 6 patients with an old unilateral hip fracture. FBP and MLEM reconstruction was performed. Since the bladder was in the FOV and filled up with fluoride, FBP produced streaks hampering region delineation. Bone blood flow (kl) and fluoride influx rate (Ki) were estimated with a 3 compartment model. Analyzed regions (n=190) showed correlation coefficients between FBP and MLEM: 0.88 for kl and 0.97 for Ki. Affected and normal femoral head regions (n=30) yielded r=0.89 for kl and r=0.95 for Ki. Variations up to 46% were seen in individual data. It is concluded that in patients MLEM provides superior images at the expense of an increased reconstruction duration. The authors' procedure appeared acceptable in clinical routine. Quantitative estimates obtained with kinetic modeling from MLEM data were reliable and correlated highly to those obtained with the standard, validated FBP algorithm.

A Finite-Element Analysis of the Effects of Intertrochanteric Osteotomy on Stresses in Femoral Head Osteonecrosis

The efficacy of osteotomy for the precollapse stage of femoral head necrosis depends on altering load transmission. The alteration must reduce the stress levels on the infarcted bone during the process of repair. The prospects for success in this regard would likely be improved by the ability to predict reliably the stress changes derived from specific osteotomies for specific femoral head involvement patterns. For this reason, an anatomic three-dimensional finite-element model has been designed to compute necrotic femoral head stress changes that accompany varus, valgus, and rotational osteotomies. Four specific patterns of femoral head infarction are considered. Comparison of the patterns of load transmission at ten discrete instants (spanning the stance phase of the gait cycle) revealed that the critical stresses in the most commonly infarcted anterolateral and central femoral head regions occur just after the instant of heel-strike. For the femoral head with a deep, narrow lesion in the weight-bearing tract, and for classic wedge-shaped segmental infarct, the data showed that 30 degrees varus osteotomy was beneficial in reducing stress levels through much of the infarcted region. The 30 degrees valgus osteotomy was less successful. Neither 30 degrees anteversion nor 30 degrees retroversion osteotomies caused substantial changes in stresses for infarcted regions along the weight-bearing tract. For the case of a wide, shallow lesion or for whole femoral head involvement, none of the four osteotomies considered was able to achieve appreciable net reduction of stresses in weakened, infarcted regions.