To analyze the effect of tooth extraction site preservation on bone mineral density 6 months after surgery. From 2020 to 2021, two adjacent teeth (37, 38) of the same patient were extracted at the same time, and then 37 were selected for site preservation, implanted with Bio-oss bone powder, covered with double Bio-gide membrane, reduce tension and sutured. After 6 months of self-healing, 38 was taken CBCT, and the gray value measurement tool in the software was used to measure the bone mineral density of 37 bone graft areas and 38 extraction sockets. Bone density was high in the center of the bone graft area after the extraction site, and the density decreased in the adjacent alveolar socket, but the gray value was still higher than 38 for natural healing. Extraction site surgery can improve bone mass and quality at the extraction site. It is good for implanting

Aims. Osteoporosis and abnormal bone metabolism may prove to be significant factors influencing the outcome of arthroplasty surgery, predisposing to complications of aseptic loosening and peri-prosthetic fracture. We aimed to investigate baseline bone mineral density (BMD) and bone turnover in patients about to undergo arthroplasty of the hip and knee. Methods. We prospectively measured bone mineral density of the hip and lumbar spine using dual-energy X-ray absorptiometry (DEXA) scans in a cohort of 194 patients awaiting hip or knee arthroplasty. We also assessed bone turnover using urinary deoxypyridinoline (DPD), a type I collagen crosslink, normalised to creatinine. Results. The prevalence of DEXA proven hip osteoporosis (T-score ≤ -2.5) among hip and knee arthroplasty patients was found to be low at 2.8% (4 of 143). Spinal osteoporosis prevalence was higher at 6.9% (12 of 175). Sixty patients (42% (60 of 143)) had osteopenia or osteoporosis of either the hip or spine. The mean T-score for the hip was -0.34 (. sd. 1.23), which is within normal limits, and the mean hip Z-score was positive at 0.87 (. sd. 1.17), signifying higher-than-average BMD for age. The median urinary DPD/creatinine was raised in both female patients at 8.1 (interquartile range (IQR) 6.6 to 9.9) and male patients at 6.2 (IQR 4.8 to 7.5). Conclusions. Our results indicate hip and knee arthroplasty patients have higher BMD of the hip and spine compared with an age-matched general population, and a lower prevalence of osteoporosis. However, untreated osteoporotic patients are undergoing arthroplasty, which may negatively impact their outcome. Raised DPD levels suggest abnormal bone turnover, requiring further investigation. Cite this article: Bone Joint Res 2014;3:14–19

Background. Reduced bone mineral density is recognised as a risk factor for hip fractures and fragility fractures in general. Vitamin D is important in maintaining healthy bone mineral levels and can therefore affect risk of hip fracture. We investigated the correlation between vitamin D levels and bone mineral density, as well as fracture type, in neck of femur fractures and also assessed the relationship of vitamin D and social deprivation. Method. We included all patients admitted to our department, with a neck of femur fracture over one year (October 2013 to October 2014). We analysed vitamin D levels for all patients during admission and compared these to bone mineral density scores, based on DEXA scan results; hip fracture type & comminution, based on admission radiographs; and levels of social deprivation, based on the patient's address. Results. In total 360 patients were admitted over the study period, with a neck of femur fracture, of which 298 had vitamin D assessed and 76 had DEXA scans. Of these cohorts, 71% were found to be vitamin D deficient and 7% had osteoporosis. No significant correlation was found between vitamin D scores and bone density, or with level of vitamin D deficiency and fracture type or comminution. A significant correlation was however identified, between low vitamin D levels and decreasing levels of social deprivation (R=0.11, p=0.04). Conclusion. No relationship was identified between vitamin D levels and hip fracture type, suggesting that vitamin D cannot be used to predict patients at risk of more comminuted fractures. Although no relationship was also identified for bone mineral density and vitamin D, this may be because the sample size of DEXA scans was relatively small. Interestingly the relationship between vitamin D and social deprivation was the reverse of what was expected and suggests that affluent individuals may be at greater risk of low vitamin D

Objectives. Several genome-wide association studies (GWAS) of bone mineral density (BMD) have successfully identified multiple susceptibility genes, yet isolated susceptibility genes are often difficult to interpret biologically. The aim of this study was to unravel the genetic background of BMD at pathway level, by integrating BMD GWAS data with genome-wide expression quantitative trait loci (eQTLs) and methylation quantitative trait loci (meQTLs) data. Method. We employed the GWAS datasets of BMD from the Genetic Factors for Osteoporosis Consortium (GEFOS), analysing patients’ BMD. The areas studied included 32 735 femoral necks, 28 498 lumbar spines, and 8143 forearms. Genome-wide eQTLs (containing 923 021 eQTLs) and meQTLs (containing 683 152 unique methylation sites with local meQTLs) data sets were collected from recently published studies. Gene scores were first calculated by summary data-based Mendelian randomisation (SMR) software and meQTL-aligned GWAS results. Gene set enrichment analysis (GSEA) was then applied to identify BMD-associated gene sets with a predefined significance level of 0.05. Results. We identified multiple gene sets associated with BMD in one or more regions, including relevant known biological gene sets such as the Reactome Circadian Clock (GSEA p-value = 1.0 × 10. -4. for LS and 2.7 × 10. -2. for femoral necks BMD in eQTLs-based GSEA) and insulin-like growth factor receptor binding (GSEA p-value = 5.0 × 10. -4. for femoral necks and 2.6 × 10. -2. for lumbar spines BMD in meQTLs-based GSEA). Conclusion. Our results provided novel clues for subsequent functional analysis of bone metabolism, and illustrated the benefit of integrating eQTLs and meQTLs data into pathway association analysis for genetic studies of complex human diseases. Cite this article: W. Wang, S. Huang, W. Hou, Y. Liu, Q. Fan, A. He, Y. Wen, J. Hao, X. Guo, F. Zhang. Integrative analysis of GWAS, eQTLs and meQTLs data suggests that multiple gene sets are associated with bone mineral density. Bone Joint Res 2017;6:572–576

To prevent bone loss, OPG/RANK/RANKL signalling pathway is a key in keeping the balance between the action of osteoblasts and osteoclasts. Aim of this study is to assess the influence of long-term nicotine exposure on bone mineral density (BMD) scores, RANKL and OPG levels of plasma and RANKL and OPG immunoreactivities of tissue in rats. In this study, totally 36 Swiss Albino rats (70±10 g) were used in three groups. Whereas normal drinking water was given for the control group (n:12), 0.4 mg/kg/day and 6.0 mg/kg/day nicotine was added to drinking water for low-dose nicotine (LDN) group (n:12) and high-dose nicotine (HDN) group (n:12), respectively for 12 months. At the end of 12. th. month, BMD scores were measured via X-ray absorptiometry and then bone turnover was assessed via measuring both RANKL, OPG levels in plasma and RANKL, OPG immunoreactivities in tail vertebrae of all rats. Lumbar spine and femoral regions BMD scores of the control group and the nicotine groups were not significantly difference. In HDN group, OPG levels of plasma were found significantly higher when compared with the control and LDN groups (p=0.001) unlike RANKL levels of plasma. RANKL and OPG immunoreactivities of tissue were found significantly lower in both LDN and HDN groups (p<0.001, p=0.004, respectively) in comparison to control group. No correlation was found between plasma levels and tissue immunoreactivities of RANKL and OPG. As a result, this study indicates that nicotine is not primarily responsible for the decline of BMD frequently seen in smokers

The shape of the vertebral bodies from L1 to L4 was assessed from lateral dual-energy x-ray absorptiometry (DXA) images using an active shape model. The output from the model was compared to measurements of areal bone mineral density in L1 to L4 (aBMD) using a stepwise linear regression model. A significant relationship was found between aBMD and vertebral shape that suggests that the method may be useful for correcting artefacts such as osteophytes

We investigated the effect of locally administered bisphosphonate on distraction osteogenesis in a rabbit model and evaluated its systemic effect. An osteotomy on the right tibia followed by distraction for four weeks was performed on 47 immature rabbits. They were divided into seven equal groups, with each group receiving a different treatment regime. Saline and three types of dosage of alendronate (low, 0.75 μg/kg; mid, 7.5 μg/kg and high 75 μg/kg) were given by systemic injection in four groups, and saline and two dosages (low and mild) were delivered by local injection to the distraction gap in the remaining three groups. The injections were performed five times weekly during the period of distraction. After nine weeks the animals were killed and image analysis and mechanical testing were performed on the distracted right tibiae and the left tibiae which served as a control group. The local low-dose alendronate group showed a mean increase in bone mineral density of 124.3 mg/cm. 3. over the local saline group (analysis of variance, p < 0.05) without any adverse effect on the left control tibiae. The findings indicate that the administration of local low-dose alendronate could be an effective pharmacological means of improving bone formation in distraction osteogenesis

Total Hip Replacement (THR) is one of the most successful operations in all of medicine, however surgeons just rely on their experience and expertise when choosing between cemented or cementless stem, without having any quantitative guidelines. The aim of this project is to provide clinicians with some tools to support in their decision making. A novel method based on bone mineral density (BMD) measurements and assessments was developed 1) to estimate the periprosthetic fracture risk (FR) while press-fitting cementless stem; 2) to evaluate post-operative bone remodeling in terms of BMD changes after primary THR. Data for 5 out of over 70 patients (already involved in a previous study. 1. ) that underwent primary THA in Iceland were selected for developing novel methods to assess intra-operative FR and bone mineral density (BMD) changes after the operation. For each patient three CT images were acquired (Philips Brilliance 64 Spiral-CT, 120 kVp, slice thickness: 1 mm, slice increment: 0.5 mm): pre-op, 24 hours and 1 year post-operative. Pre-op CT scan was used to create 3D finite element model (Materialise Mimics) of the proximal femur. The material properties were assigned based on Hounsfield Units. Different strategies were analyzed for simulating the press-fitting operation, developing what has already been done in prior study. 1. In the finite element simulation (Ansys Workbench), a pressure (related to the implant hammering force of 9.25 kN. 2. ) was applied around the femur's hollow for the stem and the distribution of maximum principal elastic strain over the bone was calculated. Assuming a critical failure value. 3. of 7300 με, the percentage of fractured elements was calculated (i.e. FR). Post 24 hours and Post 1 year CT images were co-registrated and compared (Materialise Mimics) in order to assess BMD changes. Successively, volumes of bone lost and bone gained were calculated and represented in a 3D model. Age and gender should not be taken as unique indicators to choose between implants typologies, since also three dimensional BMD distribution along with volume of cortical bone influence the risk of periprosthetic fractures. Highest FR values were experienced in the calcar-femorale zone and in similar location on the posterior side. BMD loss volume fractions after 1 year were usually higher than BMD gain ones. Consistently with prior studies. 4. , BMD loss was mainly concentrated around the proximal end (lesser trochanter area, outer bone). If present, BMD gain occurred at the distal end (below stem's tip) or proximally (lesser trochanter area, interface contact with the stem). The use of clinical data for BMD assessments serves as an important tool to develop a quantitative method which will support surgeons in their decisions, guiding them to the optimal implant for the patient. Knowing the risk of fracture if choosing a cementless stem and being aware of how the bone will remodel around the stem in one year's time can eventually lead to reduction in revisions and increased quality of life for the patient. Further work will target analysis of a larger cohort of patients and validate FE models

Fragility fractures are an increasing cause of morbidity and mortality in the elderly population. Their association with reduced bone mineral density (BMD) is well documented. It is a reasonable assumption that hip fracture severity is linked to the magnitude of bone loss, (the lower the BMD, the more severe the fracture), however it is not known whether this correlation exists. Our aim therefore was to investigate the relationship between BMD and hip fracture severity. We reviewed 142 patients, 96 females and 46 males, mean age 74 years (49-92), who had sustained a hip fracture following a simple ground level fall. All had subsequently undergone DEXA bone scanning of the contralateral hip and lumbar spine. Fractures were classified as intra-capsular, extra-capsular or subtrochanteric, then sub-classified using the Garden, Jensen and Seinsheimer classifications respectively. They were grouped into simple (stable) or comminuted (unstable) fracture patterns. Risk factors for osteoporosis were recorded. A low hip BMD (<2.5) was associated with an increased risk of extra-capsular fracture (p=0.025). However, no association with fracture type (extra vs. intra-capsular, p>0.05) was identified with the following variables; age, gender, BMI <25, smoking, and excess alcohol intake. We did not find any statistically significant associations between fracture severity and the nine principle variables tested for: age; gender; smoking; BMI < 25; alcohol excess and low hip or lumbar BMD T or Z score <-2.5. Although the association between BMD and risk of fragility fractures is well documented, the results of this study would suggest that severity of hip fractures does not follow this correlation. Therefore, no assumption can be made about BMD of the proximal femur based on the severity of fracture observed on plain radiographs alone

Locking plate fixation in proximal humeral fractures has demonstrated good results tempered by a significant rate of loss of fixation. Reported rates of failure are typically around 10% of cases but can be 20% or higher. In addition large series are often made up of a diverse patient population, so we have chosen to focus solely on patients confirmed to have significantly reduced BMD who can be considered a subset at high risk of fixation failure. Twenty-three patients (5 male, 18 female) with a proximal humeral fracture treated by locking plate fixation were confirmed on DEXA scanning to be osteopaenic (17), osteoporotic (4) or severely osteoporotic (2). Patients early in the series were reviewed retrospectively and recalled for an updated assessment where appropriate, and the remainder were followed prospectively. The average age was 66 years (range 49 to 82). Follow up was for an average of nine months following surgery (range 2 and a half to 28 months). 17 patients underwent surgery for acute injuries and 6 for established surgical neck non-unions. Seven injuries were 2-part fractures, 12 3-part, 3 were 4-part and one a 2-part surgical neck non-union.1 plate failed due to complete loss of fixation within 2 months in a patient with severe osteoporosis and was treated with removal of metalwork. This was the only injury that failed to unite. Avascular necrosis occurred in three patients with two revised to a hemiarthroplasty. 1 patient had ongoing pain and underwent removal of the plate. Our series demonstrated that locking plate fixation of proximal humeral fractures is associated with a low rate of fixation failure and satisfactory outcomes in patients with significantly reduced bone mineral density

Stand-alone anterior lumbar interbody fusion (ALIF) provides the opportunity to avoid supplemental posterior fixation. This may reduce morbidity and complication rate, which is of special interest in patients with reduced bone mineral density (BMD). This study aims to assess immediate biomechanical stability and radiographic outcome of a stand-alone ALIF device with integrated screws in specimens of low BMD. Eight human cadaveric spines (L4-sacrum) were instrumented with SynFix-LR™ (DePuy Synthes) at L5/S1. Quantitative computed tomography was used to measure BMD of L5 in AMIRA. Threshold values proposed by the American Society of Radiology 80 and 120 mg CaHa/mL were used to differentiate between Osteoporosis, Osteopenia, and normal BMD. Segmental lordosis, anterior and posterior disc height were analysed on pre- and postoperative radiographs (Fig 1). Specimens were tested intact and following instrumentation using a flexibility protocol consisting of three loading cycles to ±7.5 Nm in flexion-extension, lateral bending, and axial rotation. The ranges of motion (ROM) of the index level were assessed using an optoelectronic system. BMD ranged 58–181mg CaHA/mL. Comparison of pre- and postoperative radiographs revealed significant increase of L5/S1 segmental lordosis (mean 14.6°, SD 5.1, p < 0.001) and anterior disc height (mean 5.8mm, SD 1.8, p < 0.001), but not posterior disc height. ROM of 6 specimens was reduced compared to the intact state. Two specimens showed destructive failure in extension. Mean decrease was most distinct in axial rotation up to 83% followed by flexion-extension. ALIF device with integrated screws at L5/S1 significantly increases segmental lordosis and anterior disc height without correlation to BMD. Primary stability in the immediate postoperative situation is mostly warranted in axial rotation. The risk of failure might be increased in extension for some patients with reduced lumbar BMD, therefore additional posterior stabilization could be considered. For any figures or tables, please contact the authors directly

We aimed to evaluate the precision and longitudinal sensitivity of measurement of bone mineral density (BMD) in the pelvis and to determine the effect of bone cement on the measurement of BMD in femoral regions of interest (ROI) after total hip arthroplasty (THA). A series of 29 patients had duplicate dual-energy x-ray absorptiometry (DXA) scans of the hip within 13 months of THA. Pelvic analyses using 3- and 4-ROI models gave a coefficient of variation (CV) of 2.5% to 3.6% and of 2.5% to 4.8%, respectively. Repeat scans in 17 subjects one year later showed a significant change in BMD in three regions using the 4-ROI model, compared with change in only one region with the 3-ROI model (p < 0.05). Manual exclusion of cement from femoral ROIs increased the net CV from 1.6% to 3.6% (p = 0.001), and decreased the measured BMD by 20% (t = 12.1, p < 0.001). Studies of two cement phantoms in vitro showed a small downward drift in bone cement BMD giving a measurement error of less than 0.03 g/cm. 2. /year associated with inclusion of cement in femoral ROIs. Changes in pelvic periprosthetic BMD are best detected using a 4-ROI model. Analysis of femoral ROI is more precise without exclusion of cement although an awareness of its effect on the measurement of the BMD is needed

Our aim was to determine the precision of the measurements of bone mineral density (BMD) by dual-energy x-ray absorptiometry in the proximal femur before and after implantation of an uncemented implant, with particular regard to the significance of retro- and prospective studies. We examined 60 patients to determine the difference in preoperative BMD between osteoarthritic and healthy hips. The results showed a preoperative BMD of the affected hip which was lower by a mean of 4% and by a maximum of 9% compared with the opposite side. In addition, measurements were made in the operated hip before and at ten days after operation to determine the effect of the implantation of an uncemented custom-made femoral stem. The mean increase in the BMD was 8% and the maximum was 24%. Previous retrospective studies have reported a marked loss of BMD on the operated side. The precision of double measurements using a special foot jig showed a modified coefficient of variation of 0.6% for the non-operated side in 15 patients and of 0.6% for the operated femur in 20 patients. The effect of rotation on the precision of the measurements after implantation of an uncemented femoral stem was determined in ten explanted femora and for the operated side in ten patients at 10° rotation and in 20 patients at 30° rotation. Rotation within 30° influenced the precision in studies in vivo and in vitro by a mean of 3% and in single cases in up to 60%. Precise prediction of the degree of loss of BMD is thus only possible in prospective cross-sectional measurements, since the effect of the difference in preoperative BMD, as well as the apparent increase in BMD after implantation of an uncemented stem, is not known from retrospective studies. The DEXA method is a reliable procedure for determining periprosthetic BMD when positioning and rotation are strictly controlled

The operative treatment of fractures of the proximal humerus can be complicated by poor bone quality. Our aim was to evaluate a new method which allows prediction of the bone quality of the proximal humerus from radiographs. Anteroposterior radiographs were taken of 19 human cadaver humeri. The cortical thickness was measured at two levels of the proximal humeral diaphysis. The bone mineral density (BMD) was determined for the humeral head (HH), the surgical neck (SN), the greater tuberosity (GT) and lesser tuberosity (LT) using dual-energy x-ray absorptiometry. The mean cortical thickness was 4.4 ± 1.0 mm. Specimens aged 70 years or less had a significantly higher cortical thickness than those aged over 70 years. A significant positive correlation was found between cortical thickness and the BMD for each region of interest. The cortical thickness of the proximal diaphysis is a reliable predictor of the bone quality of the proximal humerus

Weight-bearing is a known stimulus for bone remodelling and a reduction in weight-bearing is associated with reduced bone mineral density (BMD) in affected limbs post lower limb fracture. This study investigated short and long-term precision of a method for measuring relative left/right weight-bearing using two sets of identical calibrated scales. The effect of imbalance on BMD at the hip and on lower limb lean tissue mass (LLTM) was also assessed. 46 postmenopausal women, with no history of leg or ankle fracture, were measured three times whilst standing astride two scales (Seca, Germany). 34 of the participants were re-measured after 6 months by the same method. Bilateral hip and total body dual x-ray absorptiometry measurements were performed using a GE Lunar Prodigy (Bedford, MA). Precision errors in weight-bearing measures were calculated using the root mean square coefficient of variation (RMSCV%). The correlations at the first visit between left/right differences in weight-bearing and differences in BMD and LLTM were calculated. The short-term RMSCV% for left and right weights were 4.20% and 4.25% respectively and the long-term RMSCV% were 6.91% and 6.90%. Differences in left/right weight-bearing ranged from 0 to 24% (SD 8.63%) at visit 1 and 0 to 30% (SD 10.71%) at visit 2. Using data from visit 1, the relationship between hip BMD differences and left/right weight-bearing differences were investigated, with no significant correlations found. However, a weak, but statistically significant correlation of r=0.35 (p=0.02) was found for differences in LLTM and left/right weight-bearing differences. In conclusion, left/right weight-bearing measured using two scales is a precise method for evaluating differences in weight-bearing in the short and long-term. Differences in left/right weight-bearing in this population varied by up to 30%. Participants showed a high degree of consistency in their long-term balance in a natural standing posture. Inequalities in left/right weight-bearing did not correlate significantly with BMD at the hip, but demonstrated a weak but statistically significant correlation with lean tissue mass

Background and objectives. Local bone-related adverse events occur more frequently following metal-on metal hip resurfacing (MOMHR) versus convention total hip arthroplasty (THA). High local tissue levels of cobalt and chromium may contribute to impaired bone health, however the systemic effects on bone of exposure to elevated metal levels after MOMHR are unknown. Methods. In this cross-sectional study we compared whole body bone mineral density (WB-BMD) and biochemical markers of bone turnover in 31 healthy male subjects at a mean of 8 years after MOMHR versus 31 individually age and time since surgery matched male subjects after conventional THA. All subjects had well-functioning prostheses and were in good self-reported health as assessed by Oxford Hip Score and EQ-5D questionnaire. WB-BMD was measured by dual energy x-ray absorptiometry and adjusted for pre-morbid osteoporosis risk factors using the FRAX tool, and for the presence of the metal prostheses using identical exclusion regions. Bone turnover markers were measured on fasting morning serum or 24hr urine collection by electro-chemiluminescent assay. Cobalt and chromium were measured by ICP-MS. Results. The subject pairs were similar for all matching criteria (P>0.05, all comparisons). Cobalt and chromium were elevated in the MOMHR versus THA group (P<0.05, all comparisons). WB-BMD was 7% higher in the MOMHR versus THA subjects (1.05 versus 0.98 g/cm2, P= 0.002). Bone formation, measured by serum osteocalcin, was 17% lower in the MOMHR versus THA subjects (18.2 versus 21.1ng/mL, P= 0.02) and osteoclast number measured by TRAP 5b, was 23% lower (3.4 versus 3.9U/L, P= 0.008). Systemic levels of bone formation and resorption markers were inversely correlated with systemic cobalt, but not chromium levels (Spearman, P<0.05). Conclusion. Subjects 8 years after MOMHR versus THA have higher WB-BMD and lower bone turnover measured by some markers, and marker activity inversely correlate to systemic cobalt levels. These data suggest that this metal has a systemic suppressive effect on bone turnover. The difference in BMD may be due to a reduction in age-related bone loss since surgery, although the measured BMD might also be due, in part, to diffuse metal deposition within the skeleton

While knee osteoarthritis (OA) is now recognized as a complex disease affecting the whole joint, not just the cartilages, there remains a paucity of data regarding the interactions between knee components. One relationship of particular interest is between the spatial variations in cartilage thickness (CTh) and subchondral bone mineral density (BMD). Indeed, bone and cartilage are two mechanosensitive tissues that interact as a functional unit and there is evidence of a biomechanical coupling between both tissues. Particularly, a recent in vivo study has shown a positive relationship in non-OA knees with thicker cartilage where bone is denser, and an alteration of this relationship in OA knees. These observations support the concept of an osteochondral unit and warrant additional research to assess the influence of bone depth. Therefore, this study aimed to characterize the relationship between spatial variations in CTh and BMD measured at various depths below the bone surface.

CT-arthrography of 20 non-OA tibias and 20 severe medial-compartment OA tibias were segmented to build 3D mesh models of the bones and cartilages. Each individual tibia model was registered to a reference tibia, allowing to calculate BMD maps at 1, 3, 5 and 10mm below the bone-cartilage interface in the medial compartment. Pearson correlations between CTh maps and the four BMD maps were then calculated for each knee. Lastly, differences in correlation coefficients between successive bone layers were assessed using Wilcoxon signed-rank tests.

In both OA and non-OA tibias, the correlation coefficients were higher with the BMD measured in the 1mm layer, and followed a pattern of statistically significant decrease with bone layers of increasing depth (p < 0.021). In non-OA tibias, the median relationship was positive with a strong effect size in the 1, 3 and 5mm layers, while in OA tibias the median relationship was positive only in the 1mm layer and with a medium effect size. In the OA tibias, the median relationship was negative with a weak effect size in the 3 and 5mm layers, and it was negative with a medium effect size in the 10mm layer.

In conclusion, the results of the present study support the value of considering bone and cartilage as a unit, and more generally support OA pathophysiology models based on relationships among knee properties.

Background

Although knee osteoarthritis (OA) has first been thought to be a wear-and-tear disease of the articular cartilage, it is now established that it is a disease of the entire joint. Unfortunately, its complex physiopathology is still incompletely understood, limiting the design of efficient therapeutic options. Recently, it has been suggested that OA could be related to the breakdown of the relationships among knee tissues rather than to isolated alterations of one or more tissues. However, there is a paucity of data regarding relationships among knee tissues. Better understanding the bone and cartilage relationships is thus of particular interest as both tissues contribute to the transfer of the mechanical loads through the joint and altered loading is known to be a main factor of OA onset and progression. Specifically, there is an interest to determine if cartilage thickness (CTh) and subchondral bone mineral density (sBMD), two properties related to loading, are adapted in healthy femurs.

Osteoporosis is a common disorder characterized by low bone mass and reduced bone quality that affects the bone strength negatively and leads to increased risk of fracture. Bone mineral density (BMD) has been the standard instrument for the diagnosis of osteoporosis and the determination of fracture risk. Despite the approximation of the bone mass, BMD does not provide information about the bone structure. Trabecular bone score (TBS), which provides an indirect evaluation of skeletal microarchitecture, is calculated from dual X-ray absorptiometry and a simple and noninvasive method that may contribute to the prediction of osteoporotic fractures in addition to the measure of bone density. The goal of this study was to determine the mean TBS values in healthy postmenopausal women and the overall association between TBS and demographic features, bone mineral density of the lumbar spine and femoral neck and bone mineral density to body mass index ratio (BMD/BMI) of the lumbar spine. Fifty-three postmenopausal healthy women participated. The bone mineral density of the lumbar spine and femoral neck were measured dual X-ray absorptiometry. Anteroposterior lumbar spine acquisitions were used to calculate TBS for L1-L4. Age, height, weight, BMI and the ratio of BMD to BMI, which was considered to be a simple tool for assessing fracture risk in especially obese individuals, were calculated. The relationship between TBS and other variables was examined using Spearman's rank correlation coefficients. Mean BMD of the lumbar spine and the femoral neck were 0.945 ± 0.133 and 0.785 ± 0.112 g/cm2, respectively (Table 1). Mean TBS was 1.354 ± 0.107. There was a significant positive moderate correlation between TBS and total lumbar BMD/BMI ratio (r=0.595, pTBS values of postmenopausal women were negatively correlated with age and BMI and positively with bone mineral density and BMD/BMI ratio. The ratio between lumbar BMD and BMI presented a stronger correlation with TBS than that of BMD with TBS. Because of the better correlation, the BMD/BMI ratio may be used as a simple tool for the assessment of the risk of fractures. Further investigation may be needed to evaluate the factors influencing exercise intervention on TBS on this population of patients

The medial periosteal hinge plays a key role in fractures of the head of the humerus, offering mechanical support during and after reduction and maintaining perfusion of the head by the vessels in the posteromedial periosteum. We have investigated the biomechanical properties of the medial periosteum in fractures of the proximal humerus using a standard model in 20 fresh-frozen cadaver specimens comparable in age, gender and bone mineral density. After creating the fracture, we displaced the humeral head medial or lateral to the shaft with controlled force until complete disruption of the posteromedial periosteum was recorded. As the quality of periosteum might be affected by age and bone quality, the results were correlated with the age and the local bone mineral density of the specimens measured with quantitative CT. Periosteal rupture started at a mean displacement of 2.96 mm (. sd. 2.92) with a mean load of 100.9 N (. sd. 47.1). The mean maximum load of 111.4 N (. sd. 42.5) was reached at a mean displacement of 4.9 mm (. sd. 4.2). The periosteum was completely ruptured at a mean displacement of 34.4 mm (. sd. 11.1). There was no significant difference in the mean distance to complete rupture for medial (mean 35.8 mm (. sd. 13.8)) or lateral (mean 33.0 mm (. sd. 8.2)) displacement (p = 0.589). The mean bone mineral density was 0.111 g/cm. 3. (. sd. 0.035). A statistically significant but low correlation between bone mineral density and the maximum load uptake (r = 0.475, p = 0.034) was observed. This study showed that the posteromedial hinge is a mechanical structure capable of providing support for percutaneous reduction and stabilisation of a fracture by ligamentotaxis. Periosteal rupture started at a mean of about 3 mm and was completed by a mean displacement of just under 35 mm. The microvascular situation of the rupturing periosteum cannot be investigated with the current model