Bone age is a radiographical assessment used in pediatric medicine due to its relative objectivity in determining biological maturity compared to chronological age and size.1 Currently, Greulich and Pyle (GP) is one of the most common methods used to determine bone age from hand radiographs.2–4 In recent years, new methods were developed to increase the efficiency in bone age analysis like the shorthand bone age (SBA) and the automated artificial intelligence algorithms. The purpose of this study is to evaluate the accuracy and reliability of these two methods and examine if the reduction in analysis time compromises their accuracy. Two hundred thirteen males and 213 females were selected. Each participant had their bone age determined by two separate raters using the GP (M1) and SBA methods (M2). Three weeks later, the two raters repeated the analysis of the radiographs. The raters timed themselves using an online stopwatch while analyzing the radiograph on a computer screen. De-identified radiographs were securely uploaded to an automated algorithm developed by a group of radiologists in Toronto. The gold standard was determined to be the radiology report attached to each radiograph, written by experienced radiologists using GP (M1). For intra-rater variability, intraclass correlation analysis between trial 1 (T1) and trial 2 (T2) for each rater and method was performed. For inter-rater variability, intraclass correlation was performed between rater 1 (R1) and rater 2 (R2) for each method and trial. Intraclass correlation between each method and the gold standard fell within the 0.8–0.9 range, highlighting significant agreement. Most of the comparisons showed a statistically significant difference between the two new methods and the gold standard; however it may not be clinically significant as it ranges between 0.25–0.5 years. A bone age is considered clinically abnormal if it falls outside 2 standard deviations of the chronological age; standard deviations are calculated and provided in GP atlas.6–8 For a 10-year old female, 2 standard deviations constitute 21.6 months which far outweighs the difference reported here between SBA, automated algorithm and the gold standard. The median time for completion using the GP method was 21.83 seconds for rater 1 and 9.30 seconds for rater 2. In comparison, SBA required a median time of 7 seconds for rater 1 and 5 seconds for rater 2. The automated method had no time restraint as bone age was determined immediately upon radiograph upload. The correlation between the two trials in each method and rater (i.e. R1M1T1 vs R1M1T2) was excellent (κ= 0.9–1) confirming the reliability of the two new methods. Similarly, the correlation between the two raters in each method and trial (i.e. R1M1T1 vs R2M1T1) fell within the 0.9–1 range. This indicates a limited variability between raters who may use these two methods. The shorthand bone age method and an artificial intelligence automated algorithm produced values that are in agreement with the gold standard Greulich and Pyle, while reducing analysis time and maintaining a high inter-rater and intra-rater reliability

Purpose of the study: Determining bone age at the wrist is not an easy task and can be a source of error. We elaborated a method for determining bone age at the elbow using an analysis of bone maturation at this localization. Material and methods: The method finetunes the Sauvegrain method and is based on more than ten years of data for the analysis of more than 3600 x-rays. Bone maturation evolves from 0% at birth to 100% marking the end of growth. We propose a digital system for drawing the growth curve from 50% to 100% bone maturation as a function of chronological age. This curve gives the distribution of bone age around the median for each gender. Fifty percent maturation corresponds to onset of adolescence and can be used to define onset of puberty before any other clinical sign; 100% bone maturation corresponds to maximal growth or stature. Specific bone landmarks are used and the method for calculating bone age is presented. Results: It is interesting that a shift of one year or more between bone age calculated at the elbow and that calculated from the wrist. This observation was frequent and suggests that bone age determined at the elbow gives a better reflection of limb maturation. In addition, regular use of this method in daily practice confirmed its usefulness, reliability, and inter- and intra-observer reproducibility. Conclusion: This is a reliable simple method for determining bone maturation. It is easier to use than the wrist method and probably better reflects bone maturation of the limbs

Introduction: Prophylactic pinning of an asymptomatic hip in SCFE is controversial. Bone age has been used as evidence of future contralateral slip risk and used as an indication for such intervention. The efficacy of bone age assessment at predicting contralateral slip was tested in this study. Patients and Methods: 18 Caucasian children prospectively had bone age assessment using wrist and hand x-rays when presenting with a unilateral SCFE. Patients and parents were informed about the chance of con-tralateral slip and risks of prophylactic fixation, and advised to attend hospital immediately on development of symptoms in contralateral hip. After in-situ fixation of the affected side prospective monitoring in outpatient department was performed. Surgical intervention was undertaken if the contralateral hip was symptomatic. Results: Three children (2 boys) went on to develop to a contralateral slip at a mean of 20 months from initial presentation. 6 children (5 boys) were deemed at risk of contralateral slip due to a bone age below 12.5 years for boys and 10.5 for girls. Only one from this group developed a contralateral slip. The relative risk of proceeding to contralateral slip when the bone age is below the designated values was 1 (95% confidence interval of 0.1118 to 8.95). The sensitivity and specificity were 33% and 66% respectively. With positive predictive value of 15% and diagnostic efficiency of 61%. Conclusion: Delayed bone age by itself is not a good predictor of future contralateral slip at initial presentation. Routine prophylactic pinning is not justified based on bone age alone, with the risks of surgical fixation it carries. Prospective long term longitudinal study is required

Introduction: Prophylactic pinning of an asymptomatic hip in SCFE is controversial. Bone age has been used as evidence of future contralateral slip risk and used as an indication for such intervention. The efficacy of bone age assessment at predicting contralateral slip was tested in this study. Patients and Methods: 18 Caucasian children prospectively had bone age assessment using wrist and hand x-rays when presenting with a unilateral SCFE. Patients and parents were informed about the chance of contralateral slip and risks of prophylactic fixation, and advised to attend hospital immediately on development of symptoms in contralateral hip. After in-situ fixation of the affected side prospective monitoring in outpatient department was performed. Surgical intervention was undertaken if the contralateral hip was symptomatic. Results: Three children (2 boys) went on to develop to a contralateral slip at a mean of 20 months from initial presentation. 6 children (5 boys) were deemed at risk of contralateral slip due to a bone age below 12.5 years for boys and 10.5 for girls. Only one from this group developed a contralateral slip. The relative risk of proceeding to contralateral slip when the bone age is below the designated values was 1 (95% confidence interval of 0.1118 to 8.95). Conclusion: Delayed bone age by itself is not a good predictor of future contralateral slip at initial presentation. Routine prophylactic pinning is not justified based on bone age alone, with the risks of surgical fixation it carries. Prospective long term longitudinal study is required

Introduction: Prophylactic pinning of an asymptomatic hip in SCFE is controversial. Bone age has been used as evidence of future contralateral slip risk and used as an indication for such intervention. The efficacy of bone age assessment at predicting contralateral slip was tested in this study. Patients and Methods: 18 Caucasian children prospectively had bone age assessment using wrist and hand x-rays when presenting with a unilateral SCFE. Patients and parents were informed about the chance of con-tralateral slip and risks of prophylactic fixation, and advised to attend hospital immediately on development of symptoms in contralateral hip. After in-situ fixation of the affected side prospective monitoring in outpatient department was performed. Surgical intervention was undertaken if the contralateral hip was symptomatic. Results: Three children (2 boys) went on to develop to a contralateral slip at a mean of 20 months from initial presentation. 6 children (5 boys) were deemed at risk of contralateral slip due to a bone age below 12.5 years for boys and 10.5 for girls. Only one from this group developed a contralateral slip. The relative risk of proceeding to contralateral slip when the bone age is below the designated values was 1 (95% confidence interval of 0.1118 to 8.95). The sensitivity and specificity were 33% and 66% respectively. With positive predictive value of 15% and diagnostic efficiency of 61%. Conclusion: Delayed bone age by itself is not a good predictor of future contralateral slip at initial presentation. Routine prophylactic pinning is not justified based on bone age alone, with the risks of surgical fixation it carries. Prospective long term longitudinal study is required

A chance observation of asymmetrical bone ages in a child with spastic hemiplegia stimulated a prospective gathering of bilateral hand radiographs in 33 hemiplegic patients, and on a single occasion in a control group of 23 patients with leg length discrepancy in the absence of neurological disorder. The bone age assessments according to Greulich and Pyle, which by convention has used the left hand only, were done by a single expert observer blinded to the clinical details. 13 hemiplegic patients (39%) had delayed bone ages of 6 months or more. When present it was always delayed on the hemiplegic side. The mean delay for the whole group was 2.5 months, whereas there was no mean difference in the control group (p = 0.001). The oldest bone age with asymmetry was 14.5 years in males and 12 years in females, indicating that when present the delay “catches up” in the last 2-3 years of growth. In hemiplegia the percentage leg length discrepancy also tends to decrease during later growth, and after 80% of growth the hemiplegic side outgrows the normal leg by a mean of 0.3cm/year. No correlation could be found between the delay of bone age and the severity of either the neurological abnormality or the actual discrepancy of length. The implications for clinical management will be discussed

Cemented femoral stems with force closed fixation designs have shown good clinical results despite high early subsidence. A new triple-tapered stem in this category (C-stem AMT) was introduced in 2005. This study compares this new stem with an established stem of similar design (Exeter) in terms of migration (as measured using radiostereometric analysis), peri-prosthetic bone remodelling (measured using dual energy x-ray densitometry, DXA), Oxford Hip Score, and plain radiographs. . A total of 70 patients (70 hips) with a mean age of 66 years (53 to 78) were followed for two years. Owing to missing data of miscellaneous reasons, the final analysis represents data from 51 (RSA) and 65 (DXA) patients. Both stems showed a typical pattern of migration: Subsidence and retroversion that primarily occurred during the first three months. C-stem AMT subsided less during the first three months (p = 0.01), before stabilising at a subsidence rate similar to the Exeter stem from years one to two. The rate of migration into retroversion was slightly higher for C-stem AMT during the second year (p = 0.03). Whilst there were slight differences in movement patterns between the stems, the C-stem AMT exhibits good early clinical outcomes and displays a pattern of migration and bone remodelling that predicts good clinical performance. Cite this article: Bone Joint J 2015;97-B:755–61

Objectives: Nowadays estimating paediatric bone age is done using methods based on standards from the 50’s and 70’s. These methods are often difficult to perform, they require experience in the analysis of multiple bones and are based on subjective measures. Many times, the age calculated stands within a wide range of age interval. We investigate a new method based on AP foot X-rays. Material and Methods: 971 radiographs taken from 220 paediatric patients (0–18 years old) were analyzed. 34 different ratios were designed by measuring ossification centres of the bones of the first and second foot rays. These ratios were statistically studied searching for the relation with variables as gender, laterality, foot pathology and forefoot formulae. Finally, regression lines and curves from each ratio were calculated as well as their correlation with chronological age. Results: The best suited correlations are obtained with the ratios calculated from the epiphysis of the proximal phalange of the first and second toes. With them, multiple regression analysis is able to establish an equation that estimates bone age, with a chronological age correlation of 0,86 for general population, 0,85 for boys and 0,90 for girls (p< 0,01). It is applicable for either feet, and valid for every forefoot formula or pathologic feet. Conclusions: This new method is designed to estimate bone age in children using either plain radiographs or digital images. The method is objective, precise, universal and easy to calculate. It proves a good correlation in children between 1 and 13 years old. It is based on a modern population and adjusted with lineal regression equations to both genders

Osteoarthritis (OA) is mainly caused by ageing, strain, trauma, and congenital joint abnormalities, resulting in articular cartilage degeneration. During the pathogenesis of OA, the changes in subchondral bone (SB) are not only secondary manifestations of OA, but also an active part of the disease, and are closely associated with the severity of OA. In different stages of OA, there were microstructural changes in SB. Osteocytes, osteoblasts, and osteoclasts in SB are important in the pathogenesis of OA. The signal transduction mechanism in SB is necessary to maintain the balance of a stable phenotype, extracellular matrix (ECM) synthesis, and bone remodelling between articular cartilage and SB. An imbalance in signal transduction can lead to reduced cartilage quality and SB thickening, which leads to the progression of OA. By understanding changes in SB in OA, researchers are exploring drugs that can regulate these changes, which will help to provide new ideas for the treatment of OA. Cite this article: Bone Joint Res 2023;12(9):536–545

We assessed the Japanese specific bone age standard with Tanner-Whitehouse 2 (TW2) method for the evaluation of skeletal maturity in adolescent scoliosis. TW2 bone age was investigated by the left hand-wrist X-rays of 120 girls with adolescent scoliosis. Their chronological age ranged from 10.2 to 19.0 years. Because Risser’s sign is uncertain between Risser IV and V, for comparison of TW2 bone age with Risser’s sign, we classified apophyses that with an apparent narrowing of cartilage and that with a partial fusion as the later of Risser IV. In addition, clinical courses of the skeletal matured cases (adult bones) in 6 months before investigation were reviewed retrospectively. Even or less than 5 degrees change of Cobb’s angle was evaluated as unchanged. Furthermore, bone age distribution of immature cases was also reviewed for comparision of the unchanged group with the progressive group. None was evaluated as adult bone in the stage from Risser 0 to III. The rate of adult bone which was shown in Risser IV was 43.5%, but 88.9% was in the later of IV. 95.8% of Risser V was already adult bone. Moreover, 93.1% of adult bone was unchanged in their clinical courses. Remaining 4 cases (6.9%) was progressive, but had not progressed in the following 6 months. Bone ages of the progressive immature group distributed in the range from 11.7 to 13.9 years. Those of the unchanged immature group distributed mainly over 13.1 years. Although it is necessary to follow the immature longitudinally, adult bone appeared almost in the later of Risser IV, and appeared earlier than Risser V. And Cobb’s angle may become unchanged before adult bone. At least adult bone would be an indicator between Risser IV and V

Objectives. In total hip arthroplasty (THA), the cementless, tapered-wedge stem design contributes to achieving initial stability and providing optimal load transfer in the proximal femur. However, loading conditions on the femur following THA are also influenced by femoral structure. Therefore, we determined the effects of tapered-wedge stems on the load distribution of the femur using subject-specific finite element models of femurs with various canal shapes. Patients and Methods. We studied 20 femurs, including seven champagne flute-type femurs, five stovepipe-type femurs, and eight intermediate-type femurs, in patients who had undergone cementless THA using the Accolade TMZF stem at our institution. Subject–specific finite element (FE) models of pre- and post-operative femurs with stems were constructed and used to perform FE analyses (FEAs) to simulate single-leg stance. FEA predictions were compared with changes in bone mineral density (BMD) measured for each patient during the first post-operative year. Results. Stovepipe models implanted with large-size stems had significantly lower equivalent stress on the proximal-medial area of the femur compared with champagne-flute and intermediate models, with a significant loss of BMD in the corresponding area at one year post-operatively. Conclusions. The stovepipe femurs required a large-size stem to obtain an optimal fit of the stem. The FEA result and post-operative BMD change of the femur suggest that the combination of a large-size Accolade TMZF stem and stovepipe femur may be associated with proximal stress shielding. Cite this article: M. Oba, Y. Inaba, N. Kobayashi, H. Ike, T. Tezuka, T. Saito. Effect of femoral canal shape on mechanical stress distribution and adaptive bone remodelling around a cementless tapered-wedge stem. Bone Joint Res 2016;5:362–369. DOI: 10.1302/2046-3758.59.2000525

We measured bone mineral density (BMD) in the proximal femur by dual-energy X-ray absorptiometry (DEXA) in 20 patients after cemented total hip arthroplasty over a period of one year. We found a statistically significant reduction in periprosthetic BMD after six months on the medial side and on the lateral side adjacent to the mid and distal thirds of the prosthesis. At one year after operation there was a mean 6.7% reduction in BMD in the region of the calcar and a mean 5.3% increase in BMD in the femoral shaft distal to the tip of the implant. These changes reflect a pattern of reduced stress in the proximal femur and increased stress around the tip of the prosthesis. They support current concepts of bone remodelling in the proximal femur in response to prosthetic implantation

Introduction: The assessment of bone age using the standard Gruel and Pyle chart based on hand and wrist radiographs is usually carried out by Senior Radiologists. We performed a study to look at both intra and inter observer variability with different grades of clinicians. Materials and Methods: 30 sets of wrist radiographs were selected at random. The investigators included a Senior Radiographer, a Consultant and Registrar Radiologist an Orthopaedic Consultant and Senior Orthopaedic Fellow. Discussion: The Radiology team appear to be more consistent in their readings for the assessment of skeletal bone age than the Orthopaedic team. Howevr, it is interesting to note that although the Orthopaedic team are less consistent, when looking at the inter-observer variability, it suggests that both teams are equally well equipped to perform the task. Conclusion: Our study suggests that we should not cross professional boundaries. Render unto Caeser what is Ceaser’s!

We used dual-energy x-ray absorptiometry (DEXA) to evaluate the extent of periprosthetic bone remodelling around a prosthesis for distal femoral reconstruction, the Kotz modular femoral tibial replacement (KMFTR; Howmedica, Rutherford, New Jersey). A total of 23 patients was entered into the study which had four parts: 1) 17 patients were scanned three times on both the implant and contralateral legs to determine whether the precision of DEXA measurements was adequate to estimate bone loss surrounding the anchorage piece of the KMFTR; 2) in 23 patients the bone mineral density (BMD) in different regions of interest surrounding the diaphyseal anchorage was compared with that of the contralateral femur at the same location to test whether there was consistent evidence of loss of BMD adjacent to the prosthetic stem; 3) in 12 patients sequential studies were performed about one year apart to compare bone loss; and 4) bone loss was compared in ten patients with implants fixed by three screws and in 13 without screws. The mean coefficients of variation (SD/mean) for the 17 sets of repeated scans ranged from 2.9% to 7.8% at different regions of interest in the KMFTR leg and from 1.4% to 2.5% in the contralateral leg. BMD was decreased in the KMFTR leg relative to the contralateral limb and the percentage of BMD loss in general increased as the region of interest moved distally in the femur. Studies done after one year showed no consistent pattern of progressive bone loss between the two measurements. The ten patients with implants fixed by screws were found to have a mean loss of BMD of 42% in the most distal part of the femur, while the 13 without screw fixation had a mean loss of 11%. DEXA was shown to have adequate precision to evaluate loss of BMD around the KMFTR. This was evident relative to the contralateral leg in all patients and generally increased in the most distal part of the femur. In general, it stabilised between two measurements taken one year apart and was greater surrounding implants fixed by cross-locking screws

Aims. The aim of this study was to evaluate the clinical and radiological outcome of using an anatomical short-stem shoulder prosthesis to treat primary osteoarthritis of the glenohumeral joint. Patients and Methods. A total of 66 patients (67 shoulders) with a mean age of 76 years (63 to 92) were available for clinical and radiological follow-up at two different timepoints (T1, mean 2.6 years, . sd. 0.5; T2, mean 5.3 years,. sd. 0.7). Postoperative radiographs were analyzed for stem angle, cortical contact, and filling ratio of the stem. Follow-up radiographs were analyzed for timing and location of bone adaptation (cortical bone narrowing, osteopenia, spot welds, and condensation lines). The bone adaptation was classified as low (between zero and three features of bone remodelling around the humeral stem) or high (four or more features). Results. The mean Constant score improved significantly from 28.5 (. sd. 11.6) preoperatively to 75.5 (. sd. 8.5) at T1 (p < 0.001) and remained stable over time (T2: 76.6, . sd. 10.2). No stem loosening was seen. High bone adaptation was present in 42% of shoulders at T1, with a slight decrease to 37% at T2. Cortical bone narrowing and osteopenia in the region of the calcar decreased from 76% to 66% between T1 and T2. Patients with high bone adaptation had a significantly higher mean filling ratio of the stem at the metaphysis (0.60, . sd. 0.05 vs 0.55, . sd. 0.06; p = 0.003) and at the diaphysis (0.65 . sd. 0.05 vs 0.60 . sd. 0.05; p = 0.007). Cortical contact of the stem was also associated with high bone adaptation (14/25 shoulders, p = 0.001). The clinical outcome was not influenced by the radiological changes. Conclusion. Total shoulder arthroplasty using a short-stem humeral component resulted in good clinical outcomes with no evidence of loosening. However, approximately 40% of the shoulders developed substantial bone loss in the proximal humerus at between four and seven years of follow-up. Cite this article: Bone Joint J 2018;100-B:603–9

Objectives. Bisphosphonates are widely used as first-line treatment for primary and secondary prevention of fragility fractures. Whilst they have proved effective in this role, there is growing concern over their long-term use, with much evidence linking bisphosphonate-related suppression of bone remodelling to an increased risk of atypical subtrochanteric fractures of the femur (AFFs). The objective of this article is to review this evidence, while presenting the current available strategies for the management of AFFs. Methods. We present an evaluation of current literature relating to the pathogenesis and treatment of AFFs in the context of bisphosphonate use. Results. Six broad themes relating to the pathogenesis and management of bisphosphonate-related AFFs are presented. The key themes in fracture pathogenesis are: bone microdamage accumulation; altered bone mineralisation and altered collagen formation. The key themes in fracture management are: medical therapy and surgical therapy. In addition, primary prevention strategies for AFFs are discussed. Conclusions. This article presents current knowledge about the relationship between bisphosphonates and the development of AFFs, and highlights key areas for future research. In particular, studies aimed at identifying at-risk subpopulations and organising surveillance for those on long-term therapy will be crucial in both increasing our understanding of the condition, and improving population outcomes. Cite this article: N. Kharwadkar, B. Mayne, J. E. Lawrence, V. Khanduja. Bisphosphonates and atypical subtrochanteric fractures of the femur. Bone Joint Res 2017;6:144–153. DOI: 10.1302/2046-3758.63.BJR-2016-0125.R1

Aims

The management of periprosthetic joint infection (PJI) remains a major challenge in orthopaedic surgery. In this study, we aimed to characterize the local bone microstructure and metabolism in a clinical cohort of patients with chronic PJI.

The aims of this study were to examine the repeatability of measurements of bone mineral density (BMD) around a cemented polyethylene Charnley acetabular component using dual-energy x-ray absorptiometry and to determine the longitudinal pattern of change in BMD during the first 24 months after surgery.

The precision of measurements of BMD in 19 subjects ranged from 7.7% to 10.8% between regions, using a four-region-of-interest model. A longitudinal study of 27 patients demonstrated a transient decrease in net pelvic BMD during the first 12 months, which recovered to baseline at 24 months. The BMD in the region medial to the dome of the component reduced by between 7% and 10% during the first three months, but recovered to approximately baseline values by two years.

Changes in BMD in the pelvis around cemented acetabular components may be measured using dual-energy x-ray absorptiometry. Bone loss after insertion of a cemented Charnley acetabular component is small, transient and occurs mainly at the medial wall of the acetabulum. After two years, bone mass returns to baseline values, with a pattern suggesting a uniform transmission of load to the acetabulum.

We investigated the implant-bone interface around one design of femoral stem, proximally coated with either a plasma-sprayed porous coating (plain porous) or a hydroxyapatite porous coating (porous HA), or which had been grit-blasted (Interlok). Of 165 patients implanted with a Bimetric hip hemiarthroplasty (Biomet, Bridgend, UK) specimens were retrieved from 58 at post-mortem.

We estimated ingrowth and attachment of bone to the surface of the implant in 21 of these, eight plain porous, seven porous HA and six Interlok, using image analysis and light morphometric techniques. The amount of HA coating was also quantified.

There was significantly more ingrowth (p = 0.012) and attachment of bone (p > 0.05) to the porous HA surface (mean bone ingrowth 29.093 ± 2.019%; mean bone attachment 37.287 ± 2.489%) than to the plain porous surface (mean bone ingrowth 21.762 ± 2.068%; mean bone attachment 18.9411 ± 1.971%). There was no significant difference in attachment between the plain porous and Interlok surfaces. Bone grew more evenly over the surface of the HA coating whereas on the porous surface, bone ingrowth and attachment occurred more on the distal and medial parts of the coated surface. No significant differences in the volume of HA were found with the passage of time.

This study shows that HA coating increases the amount of ingrowth and attachment of bone and leads to a more even distribution of bone over the surface of the implant. This may have implications in reducing stress shielding and limiting osteolysis induced by wear particles.

Displaced fractures of the distal radius in children are usually reduced under sedation or general anaesthesia to restore anatomical alignment before the limb is immobilized. However, there is growing evidence of the ability of the distal radius to remodel rapidly, raising doubts over the benefit to these children of restoring alignment. There is now clinical equipoise concerning whether or not young children with displaced distal radial fractures benefit from reduction, as they have the greatest ability to remodel. The Children’s Radius Acute Fracture Fixation Trial (CRAFFT), funded by the National Institute for Health and Care Research, aims to definitively answer this question and determine how best to manage severely displaced distal radial fractures in children aged up to ten years.

Cite this article: Bone Joint J 2024;106-B(1):16–18.

Metabolic bone diseases, such as osteoporosis and osteopetrosis, result from an imbalanced bone remodeling process. In vitro bone models are often used to investigate either bone formation or resorption independently, while in vivo, these processes are coupled. Combining these processes in a co-culture is challenging as it requires finding the right medium components to stimulate each cell type involved without interfering with the other cell type's differentiation. Furthermore, differentiation stimulating factors often comprise growth factors in supraphysiological concentrations, which can overshadow the cell-mediated crosstalk and coupling. To address these challenges, we aimed to recreate the physiological bone remodeling process, which follows a specific sequence of events starting with cell activation and bone resorption by osteoclasts, reversal, followed by bone formation by osteoblasts. We used a mineralized silk fibroin scaffold as a bone-mimetic template, inspired by bone's extracellular matrix composition and organization. Our model supported osteoclastic resorption and osteoblastic mineralization in the specific sequence that represents physiological bone remodeling. We also demonstrated how culture variables, such as different cell ratios, base media, and the use of osteogenic/osteoclast supplements, and the application of mechanical load, can be adjusted to represent either a high bone turnover system or a self-regulating system. The latter system did not require the addition of osteoclastic and osteogenic differentiation factors for remodeling, therefore avoiding growth factor use. Our in vitro model for bone remodeling has the potential to reduce animal experiments and advance in vitro drug development for bone remodeling pathologies like osteoporosis. By recreating the physiological bone remodeling cycle, we can investigate cell-cell and cell-matrix interactions, which are essential for understanding bone physiology and pathology. Furthermore, by tuning the culture variables, we can investigate bone remodeling under various conditions, potentially providing insights into the mechanisms underlying different bone disorders

Abstract. Objectives. Young patients receiving metallic bone implants after surgical resection of bone cancer require implants that last into adulthood, and ideally life-long. Porous implants with similar stiffness to bone can promote bone ingrowth and thus beneficial clinical outcomes. A mechanical remodelling stimulus, strain energy density (SED), is thought to be the primary control variable of the process of bone growth into porous implants. The sequential process of bone growth needs to be taken into account to develop an accurate and validated bone remodelling algorithm, which can be employed to improve porous implant design and achieve better clinical outcomes. Methods. A bone remodelling algorithm was developed, incorporating the concept of bone connectivity (sequential growth of bone from existing bone) to make the algorithm more physiologically relevant. The algorithm includes adaptive elastic modulus based on apparent bone density, using a node-based model to simulate local remodelling variations while alleviating numerical checkerboard problems. Strain energy density (SED) incorporating stress and strain effects in all directions was used as the primary stimulus for bone remodelling. The simulations were developed to run in MATLAB interfacing with the commercial FEA software ABAQUS and Python. The algorithm was applied to predict bone ingrowth into a porous implant for comparison against data from a sheep model. Results. The accuracy of the predicted bone remodelling was verified for standard loading cases (bending, torsion) against analytical calculations. Good convergence was achieved. The algorithm predicted good bone remodelling and growth into the investigated porous implant. Using the standard algorithm without connectivity, bone started to remodel at locations unconnected to any bone, which is physiologically implausible. The implementation of bone connectivity ensures the gradual process of bone growth into the implant pores from the sides. The bone connectivity algorithm predicted that the full remodelling required more time (approximately 50% longer), which should be considered when developing post-surgical rehabilitation strategies for patients. Both algorithms with and without bone connectivity implementation converged to same final stiffness (less than 0.01% difference). Almost all nodes reached the same density value, with only a limited number of nodes (less than 1%) in transition areas with a strong density gradient having noticeable differences. Conclusions. An improved bone remodelling algorithm based on strain energy density that modelled the sequential process of bone growth has been developed and tested. For a porous metallic bone implant the same final bone density distribution as for the original adaptive elasticity theory was predicted, with a slower and more fidelic process of growth from existing surrounding bone into the porous implant. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Introduction and Objective. Bone remodelling is a continuous process whereby osteocytes regulate the activity of osteoblasts and osteoclasts to repair loading-induced microdamage. While many in vitro studies have established the role of paracrine factors (e.g., RANKL/OPG) and cellular pathways involved in bone homeostasis, these techniques are generally limited to two-dimensional cell culture, which neglects the role of the native extracellular matrix in maintaining the phenotype of osteocyte. Recently, ex vivo models have been used to understand cell physiology and mechanobiology in the presence of the native matrix. Such approaches could be applicable to study the mechanisms of bone repair, whilst also enabling exploration of biomechanical cues. However, to date an ex vivo model of bone remodelling in cortical bone has not been developed. In this study, the objective was to develop an ex vivo model where cortical bone was subjected to cyclic strains to study the remodelling of bone. Materials and Methods. Ex vivo model of bone remodelling induced by cyclic loading: At the day of culling, beam-shape bovine bone samples were cut and preserved in PBS + 5% Pen/Strep + 2 mM L-Glut overnight at 37°C. Cyclic strains were applied with a three-point bend system to induce damage with a regime at 16.66 mm/min for 5,000 cycles in sterile PBS in Evolve® bags (maximum strain 6%). A control group was cultured under static conditions. Metabolic activity: Alamar Blue assays were performed after 1 and 7 days of ex vivo culture for each group (Static, Loaded) and normalized to weight. Bone remodelling: ALP activity was assessed in the media at day 1 and 7. After 24 hours cell culture conditioned media (CM) was collected from each group and stored at −80°C. RAW264.7 cells were cultured with CM for 6 days, after which the samples were stained for TRAP, to determine osteoclastogenesis, and imaged. Histomorphometry: Samples were cultured with calcein for 3 days to label bone formation between day 4 and 7. Fluorescent images were captured at day 7. μCT scanning was performed at 3 μm resolution after labelling samples with BaSO. 4. precipitate to quantify bone damage. Results. Bone was sectioned and cultured to maintain live osteoblasts and osteocytes. CM that was obtained 24 hours after cyclic loading and added to RAW264.7 cells cultures, resulted in significantly increased osteoclastogenic potential compared to that from static samples (4.245±1.65% vs 0.88±0.48%, p<0.001). Calcein and HE staining indicated the presence of structures similar to bone remodelling cones in both groups after 7 days of culture. Also, 7 days post-loading, matrix microdamage in the stimulated area, detected with the BaSO. 4. precipitate, were not significantly increased under the load point in loaded samples (0.11±0.05% of bone volume), while at the support areas it was significantly higher (0.2387±0.06%, p<0.001) compared to the static (0.062±0.02%). Conclusions. This study demonstrates that (1) cyclic strains applied on ex vivo bovine cortical bone successfully induced remodelling as characterized by the formation of bone resorption cones, along with an increase of osteoclast formation, and (2) there was an induction of microdamage post loading as shown by the significant increases in microdamage labelled. This supports previous in vivo studies with an increase in osteoclastogenesis up to 7 days post loading. This is the first evidence of the development of an ex vivo model to study osteon remodelling that could be applied to study bone physiology and repair

The effect of high-fat diet and testosterone replacement therapy upon bone remodelling was investigated in orchiectomised male APOE-/- mice. Mice were split in to three groups: sham surgery + placebo treatment (control, n=9), orchiectomy plus placebo treatment (n=8) and orchiectomy plus testosterone treatment (n=10). Treatments were administered via intramuscular injection once a fortnight for 17 weeks before sacrifice at 25 weeks of age. Tibiae were scanned ex-vivo using µCT followed by post-analysis histology and immunohistochemistry. Previously presented µCT data demonstrated orchiectomised, placebo treated mice exhibited significantly reduced trabecular bone volume, number, thickness and BMD compared to control mice despite no significant differences in body weight. Trabecular parameters were rescued back to control levels in orchiectomised mice treated with testosterone. No significant differences were observed in the cortical bone. Assessment of TRAP stained FFPE sections revealed no significant differences in osteoclast or osteoblast number along the endocortical surface. IHC assessment of osteoprotegerin (OPG) expression in osteoblasts is to be quantified alongside markers of osteoclastogenesis including RANK and RANKL. Results support morphological analysis of cortical bone where no change in cortical bone volume or density between groups is in line with no significant change in osteoblast or osteoclast number and percentage across all three groups. Future work will include further IHC assessment of bone remodelling and adiposity, as well as utilisation of mechanical testing to establish the effects of observed morphological differences in bone upon mechanical properties. Additionally, the effects of hormone treatments upon murine-derived bone cells will be investigated to provide mechanistic insights

Aims. Knee osteoarthritis (OA) involves a variety of tissues in the joint. Gene expression profiles in different tissues are of great importance in order to understand OA. Methods. First, we obtained gene expression profiles of cartilage, synovium, subchondral bone, and meniscus from the Gene Expression Omnibus (GEO). Several datasets were standardized by merging and removing batch effects. Then, we used unsupervised clustering to divide OA into three subtypes. The gene ontology and pathway enrichment of three subtypes were analyzed. CIBERSORT was used to evaluate the infiltration of immune cells in different subtypes. Finally, OA-related genes were obtained from the Molecular Signatures Database for validation, and diagnostic markers were screened according to clinical characteristics. Quantitative reverse transcription polymerase chain reaction (qRT‐PCR) was used to verify the effectiveness of markers. Results. C1 subtype is mainly concentrated in the development of skeletal muscle organs, C2 lies in metabolic process and immune response, and C3 in pyroptosis and cell death process. Therefore, we divided OA into three subtypes: bone remodelling subtype (C1), immune metabolism subtype (C2), and cartilage degradation subtype (C3). The number of macrophage M0 and activated mast cells of C2 subtype was significantly higher than those of the other two subtypes. COL2A1 has significant differences in different subtypes. The expression of COL2A1 is related to age, and trafficking protein particle complex subunit 2 is related to the sex of OA patients. Conclusion. This study linked different tissues with gene expression profiles, revealing different molecular subtypes of patients with knee OA. The relationship between clinical characteristics and OA-related genes was also studied, which provides a new concept for the diagnosis and treatment of OA. Cite this article: Bone Joint Res 2023;12(12):702–711

Femoroacetabular impingement (FAI) results from a morphological deformity of the hip and is associated with osteoarthritis (OA). Increased bone mineral density (BMD) is observed in the antero-superior acetabulum rim where impingement occurs. It is hypothesized that the repeated abnormal contact leads to damage of the cartilage layer, but could also cause a bone remodelling response according to Wolff's Law. Thus the goal of this study was to assess the relationship between bone metabolic activity measured by PET and BMD measured in CT scans. Five participants with asymptomatic cam deformity, three patients with uni-lateral symptomatic cam FAI and three healthy controls were scanned in a 3T PET-MRI scanner following injection with [18F]NaF. Bone remodelling activity was quantified with Standard Uptake Values (SUVs). SUVmax was analyzed in the antero-superior acetabular rim, femoral head and head-neck junction. In these same regions, BMD was calculated from CT scans using the calibration phantom included in the scan. The relationship between SUVmax and BMD from corresponding regions was assessed using the coefficient of determination (R. 2. ) from linear regression. High bone activity was seen in the cam deformity and acetabular rim. SUVmax was negatively correlated with BMD in the antero-superior region of the acetabulum (R. 2. =0.30, p=0.08). SUVmax was positively correlated with BMD in the antero-superior head-neck junction of the femur (R. 2. =0.359, p=0.067). Correlations were weak in other regions. Elevated bone turnover was seen in patients with a cam deformity but the relationship to BMD was moderate. This study demonstrates a pathomechanism of hip degeneration associated with FAI deformities, consistent with Wolff's law and the proposed mechanical cause of hip degeneration in FAI. [18F]-NaF PET SUV may be a biomarker of degeneration, especially in early stages of degeneration, when joint preservation surgery is likely to be the most successful

The success of cementless orthopaedic implants relies on bony ingrowth and active bone remodelling. Much research effort is invested to develop implants with controllable surface roughness and internal porous architectures that encourage these biological processes. Evaluation of these implants requires long-term and costly animal studies, which do not always yield the desired outcome requiring iteration. The aim of our study is to develop a cost-effective method to prescreen design parameters prior to animal trials to streamline implant development and reduce live animal testing burden. Ex vivo porcine cancellous bone cylinders (n=6, Ø20×12mm) were extracted from porcine knee joints with a computer-numerically-controlled milling machine under sterile conditions within 4 hours of animal sacrifice. The bone discs were implanted with Ø6×12mm additive manufactured porous titanium implants and were then cultured for 21days. Half underwent static culture in medium (DMEM, 10% FBS, 1% antibiotics) at 37°C and 5% CO. 2. The rest were cultured in novel high-throughput stacked configuration in a bioreactor that simulated physiological conditions after surgery: the fluid flow and cyclic compression force were set at 10ml/min and 10–150 N (1Hz,5000 cycles/day) respectively. Stains were administered at days 7 and 14. Samples were evaluated with widefield microscopy, scanning electron microscopy (SEM) and with histology. More bone remodelling was observed on the samples cultured within the bioreactor: widefield imaging showed more remodelling at the boundaries between the implant-bone interface, while SEM revealed immature bone tissue integration within the pores of the implant. Histological analysis confirmed these results, with many more trabecular struts with new osteoid formation on the samples cultured dynamically compared to static ones. Ex vivo bone can be used to analyse new implant technologies with lower cost and ethical impact than animal trial. Physiological conditions (load and fluid flow) promoted bone ingrowth and remodelling

Aims. Osteoarthritis (OA) is a common degenerative joint disease. The osteocyte transcriptome is highly relevant to osteocyte biology. This study aimed to explore the osteocyte transcriptome in subchondral bone affected by OA. Methods. Gene expression profiles of OA subchondral bone were used to identify disease-relevant genes and signalling pathways. RNA-sequencing data of a bone loading model were used to identify the loading-responsive gene set. Weighted gene co-expression network analysis (WGCNA) was employed to develop the osteocyte mechanics-responsive gene signature. Results. A group of 77 persistent genes that are highly relevant to extracellular matrix (ECM) biology and bone remodelling signalling were identified in OA subchondral lesions. A loading responsive gene set, including 446 principal genes, was highly enriched in OA medial tibial plateaus compared to lateral tibial plateaus. Of this gene set, a total of 223 genes were identified as the main contributors that were strongly associated with osteocyte functions and signalling pathways, such as ECM modelling, axon guidance, Hippo, Wnt, and transforming growth factor beta (TGF-β) signalling pathways. We limited the loading-responsive genes obtained via the osteocyte transcriptome signature to identify a subgroup of genes that are highly relevant to osteocytes, as the mechanics-responsive osteocyte signature in OA. Based on WGCNA, we found that this signature was highly co-expressed and identified three clusters, including early, late, and persistently responsive genes. Conclusion. In this study, we identified the mechanics-responsive osteocyte signature in OA-lesioned subchondral bone. Cite this article: Bone Joint Res 2022;11(6):362–370

Aims. Therapeutic agents that prevent chondrocyte loss, extracellular matrix (ECM) degradation, and osteoarthritis (OA) progression are required. The expression level of epidermal growth factor (EGF)-like repeats and discoidin I-like domains-containing protein 3 (EDIL3) in damaged human cartilage is significantly higher than in undamaged cartilage. However, the effect of EDIL3 on cartilage is still unknown. Methods. We used human cartilage plugs (ex vivo) and mice with spontaneous OA (in vivo) to explore whether EDIL3 has a chondroprotective effect by altering OA-related indicators. Results. EDIL3 protein prevented chondrocyte clustering and maintained chondrocyte number and SOX9 expression in the human cartilage plug. Administration of EDIL3 protein prevented OA progression in STR/ort mice by maintaining the number of chondrocytes in the hyaline cartilage and the number of matrix-producing chondrocytes (MPCs). It reduced the degradation of aggrecan, the expression of matrix metalloproteinase (MMP)-13, the Osteoarthritis Research Society International (OARSI) score, and bone remodelling. It increased the porosity of the subchondral bone plate. Administration of an EDIL3 antibody increased the number of matrix-non-producing chondrocytes (MNCs) in cartilage and exacerbated the serum concentrations of OA-related pro-inflammatory cytokines, including monocyte chemotactic protein-3 (MCP-3), RANTES, interleukin (IL)-17A, IL-22, and GROα. Administration of β1 and β3 integrin agonists (CD98 protein) increased the expression of SOX9 in OA mice. Hence, EDIL3 might activate β1 and β3 integrins for chondroprotection. EDIL3 may also protect cartilage by attenuating the expression of IL-1β-enhanced phosphokinase proteins in chondrocytes, especially glycogen synthase kinase 3 alpha/beta (GSK-3α/β) and phospholipase C gamma 1 (PLC-γ1). Conclusion. EDIL3 has a role in maintaining the cartilage ECM and inhibiting the development of OA, making it a potential therapeutic drug for OA. Cite this article: Bone Joint Res 2023;12(12):734–746

Knowledge of the premorbid glenoid shape and the morphological changes the bone undergoes in patients with glenohumeral arthritis can improve surgical outcomes in total and reverse shoulder arthroplasty. Several studies have previously used scapular statistical shape models (SSMs) to predict premorbid glenoid shape and evaluate glenoid erosion properties. However, current literature suggests no studies have used scapular SSMs to examine the changes in glenoid surface area in patients with glenohumeral arthritis. Therefore, the purpose of this study was to compare the glenoid articular surface area between pathologic glenoid cavities from patients with glenohumeral arthritis and their predicted premorbid shape using a scapular SSM. Furthermore, this study compared pathologic glenoid surface area with that from virtually eroded glenoid models created without influence from internal bone remodelling activity and osteophyte formation. It was hypothesized that the pathologic glenoid cavities would exhibit the greatest glenoid surface area despite the eroded nature of the glenoid and the medialization, which in a vault shape, should logically result in less surface area. Computer tomography (CT) scans from 20 patients exhibiting type A2 glenoid erosion according to the Walch classification [Walch et al., 1999] were obtained. A scapular SSM was used to predict the premorbid glenoid shape for each scapula. The scapula and humerus from each patient were automatically segmented and exported as 3D object files along with the scapular SSM from a pre-operative planning software. Each scapula and a copy of its corresponding SSM were aligned using the coracoid, lateral edge of the acromion, inferior glenoid tubercule, scapular notch, and the trigonum spinae. Points were then digitized on both the pathologic humeral and glenoid surfaces and were used in an iterative closest point (ICP) algorithm in MATLAB (MathWorks, Natick, MA, USA) to align the humerus with the glenoid surface. A Boolean subtraction was then performed between the scapular SSM and the humerus to create a virtual erosion in the scapular SSM that matched the erosion orientation of the pathologic glenoid. This led to the development of three distinct glenoid models for each patient: premorbid, pathologic, and virtually eroded (Fig. 1). The glenoid surface area from each model was then determined using 3-Matic (Materialise, Leuven, Belgium). Figure 1. (A) Premorbid glenoid model, (B) pathologic glenoid model, and (C) virtually eroded glenoid model. The average glenoid surface area for the pathologic scapular models was 70% greater compared to the premorbid glenoid models (P < 0 .001). Furthermore, the surface area of the virtual glenoid erosions was 6.4% lower on average compared to the premorbid glenoid surface area (P=0.361). The larger surface area values observed in the pathologic glenoid cavities suggests that sufficient bone remodelling exists at the periphery of the glenoid bone in patients exhibiting A2 type glenohumeral arthritis. This is further supported by the large difference in glenoid surface area between the pathologic and virtually eroded glenoid cavities as the virtually eroded models only considered humeral anatomy when creating the erosion. For any figures or tables, please contact the authors directly

Abstract. Cranial cruciate ligament (CrCL) disease/rupture is a highly prevalent orthopaedic disease in dogs and common cause of pain, lameness, and secondary joint osteoarthritis (OA). Previous experiments investigating the role of glutamate receptors (GluR) in arthritic degeneration and pain revealed that OA biomarkers assessing early bone turnover and inflammation, including osteoprotegerin (OPG) and the receptor activator of nuclear factor kappa-B ligand (RANKL) are more likely to be influenced by glutamate signalling. Moreover, interleukin-6 (IL-6) has a complex and potentially bi directional (beneficial and detrimental) effect, and it is a critical mediator of arthritic pain, OA progression and joint destruction. Objectives. 1) to recruit dogs undergoing CrCL disease/rupture surgery and obtain discarded synovial fluid (SF) and serum/plasma (ethics approval, RCVS:2017/14/Alves); 2) to quantify the biomarkers listed above in the SF and serum/plasma by enzyme linked immunosorbent assay (ELISA); 3) to assess radiographic OA at the time of surgery and correlate it with the biomarkers and clinical findings. Methods. Abnova, Abcam and AMSBIO ELISA kits were tested using a validation protocol relating the standard curve to a dilution series of SF and serum/plasma (1× to 1/50×), with and without SF hyaluronidase treatment to evaluate linearity, specificity and optimal dilutions. Validated ELISA kits were used to measure [IL-6], glutamate [glu], [RANKL] and [OPG] in SF and serum/plasma. For each dog, CrCL disease pre-operative lameness scores were graded as: (1) mild, (2) moderate (easily visible), (3) marked (encumbered), (4) non-weightbearing lameness. Blinded OA scoring was performed on radiographs [15–60, normal-severe OA]. Results. canine population (n=14) was of various breeds, aged between 2–10 years and weighing 17.1–45.5Kg; 42.86% male; 57.14% female; 83.33% males and 62.5% females were neutered. Lameness scores varied from 1 and 4 (average 2.07±1.12) and radiographic OA scores from 18 and 36 (average 27.86±5.11). Individual correlations in concentrations with respect to age, weight, lameness score (1–4) and OA scores (15–60) were tested. SF [glu] and lameness score were inversely correlated with higher levels of lameness corresponding to lower SF [glu] (P=0.0141). SF [RANKL] inversely correlated with weight (P=0.0045) and lameness score (P=0.0135), and serum [RANKL] inversely correlated with weight (P=0.0437). There was also a negative correlation between SF and serum [OPG] and weight (P=0.0165 and P=0.0208, respectively). No other significant correlations were detected. Overall, [glu] and [IL-6] are increased in SF compared to serum/plasma, by 12.84 and 1.28, respectively, whereas all the remaining biomarkers are higher (2–3 times) in the serum/plasma compared to SF. Principal component analysis (PCA) and Pearson correlation coefficient matrix [IL-6/glu/RANKL/OPG] (n=7) showed SF [IL-6] correlates with SF [glu] (rs=0.64) and strong positive correlations between SF/serum [RANKL] and SF/serum [OPG] (rs 0.68–0.96). Conclusions. Dogs with CrCL disease show an association between the bone remodelling markers RANKL and OPG, and the inflammatory cytokine IL-6, and to a lesser extent SF [glu]. Therapeutics targeting bone remodelling, IL-6 or GluR/[glu] may be of interest for the management of OA in dogs. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Aims. The aim of this study was to compare the mid-term patient-reported outcome, bone remodelling, and migration of a short stem (Collum Femoris Preserving; CFP) with a conventional uncemented stem (Corail). Methods. Of 81 patients who were initially enrolled, 71 were available at five years’ follow-up. The outcomes at two years have previously been reported. The primary outcome measure was the clinical result assessed using the Oxford Hip Score (OHS). Secondary outcomes were the migration of the stem, measured using radiostereometric analysis (RSA), change of bone mineral density (BMD) around the stem, the development of radiolucent lines, and additional patient-reported outcome measures (PROMs). Results. There were no statistically significant differences between the groups regarding PROMs (median OHS (CFP 45 (interquartile range (IQR) 35 to 48); Corail 45 (IQR 40 to 48); p = 0.568). RSA showed stable stems in both groups, with little or no further subsidence between two and five years. Resorption of the femoral neck was evident in nine patients in the CFP group and in none of the 15 Corail stems with a collar that could be studied. Dual X-ray absorbiometry showed a significantly higher loss of BMD in the proximal Gruen zones in the CFP group (mean changes in BMD: Gruen zone 1, CFP -9.5 (95% confidence interval (CI) -14.8 to -4.2), Corail 1.0 (95% CI 3.4 to 5.4); Gruen zone 7, CFP -23.0 (95% CI -29.4 to -16.6), Corail -7.2 (95% CI -15.9 to 1.4). Two CFP stems were revised before two years’ follow-up due to loosening, and one Corail stem was revised after two years due to chronic infection. Conclusion. The CFP stem has a similar clinical outcome and subsidence pattern when compared with the Corail stem. More pronounced proximal stress-shielding was seen with the CFP stem, suggesting diaphyseal fixation, and questioning its femoral neck-sparing properties in the long term. Cite this article: Bone Joint J 2022;104-B(5):581–588

Introduction. Direct skeletal attachment of prosthetic limbs, commonly known as osseointegration (“OI”), is being investigated by our team with the goal of safely introducing this technology into the United States for human use. OI technology allows for anchorage of prosthetic devices directly to bone using an intramedullary stem. For OI to be effective and secure, bone ingrowth and remodeling around the implant must be achieved. Physicians need an effective way to measure bone remodeling in order to make informed decisions on prescribed loading. This work describes methodology that was developed that utilizes computed tomography (CT) imaging as a tool for analyzing bone remodeling around an osseointegrated implant. Method. A subject implanted with a new Percutaneous Osseointegrated Prosthesis (POP) (DJO Surgical, Austin, TX) had CTs taken of their residual femur at 6-weeks and 12-months post-op in a FDA Early Feasibility Study with Institutional Review Board approval. Three-dimensional models of the femur were created from dicom files of the CT slices using Mimics (v21.0, Materialise, Leuven, Belgium). Each scan was segmented into four objects: cortical bone, medullary cavity, total volume (cortical bone plus the medullary cavity) and endoprosthetic stem (Fig. 1). Following segmentation, models were uploaded to 3-Matic Research (v13.0, Materialise, Leuven, Blegium) in STL format for alignment to a common world coordinate system (Fig. 2). A common origin was set by taking the average distance between planes of the femoral head and the greater trochanter. Once aligned to the coordinate system, biomechanical length (BML) was calculated from the proximal origin to the distal end of the amputated femur. BML and STLs of the aligned medullary cavity and femur volume were entered into custom Matlab code designed to measure cortical and medullary morphology in transverse cross sections of the femur. Morphology data from 6-weeks and 12-month time points were compared in order to determine if bone remodeling around the POP implant could be detected using these methods. Results. Comparing longitudinal data from post-operative visits suggests that important indicators of bone remodeling around the device could be detected (Fig 3). One year after implantation of the POP device the medullary perimeter and area had minimal % differences (−1.5 and 2.2) from the 6-week visit, validating that consistent alignment of the femoral model was achieved between scans from different time points. The cortical area, cortical perimeter, and cortical thickness around the POP implant showed positive percent changes at the 12-months of 19.44%, 4.04% and 14.36% respectively, with the largest increases observed at the the distal end for each parameter. These increases in cortex morphology values indicate bone changes were identified around the endoprosthetic stem of the implant. Discussion/Conclusion. This pilot study utilized CT imaging as a tool for analyzing bone remodeling around a new osseointegrated device. These methods can be performed quickly and accurately and have the potential for use in monitoring bone remodeling. CT scans from additional subjects are being analyzed to further validate and optimize these methods for clinical use. This study described an investigational device, limited by federal law to investigational use. No long-term data exists about its performance. For any figures or tables, please contact the authors directly

In conventional DXA (Dual-energy X-ray Absorptiometry) analysis, pixel bone mineral density (BMD) is often averaged at the femoral neck. Neck BMD constitutes the basis for osteoporosis diagnosis and fracture risk assessment. This data averaging, however, limits our understanding of localised spatial BMD patterns that could potentially enhance fracture prediction. DXA region free analysis (RFA) is a validated toolkit for pixel-level BMD analysis. We have previously deployed this toolkit to develop a spatio-temporal atlas of BMD ageing in the femur. This study aims first to introduce bone age to reflect the overall bone structural evolution with ageing, and second to quantify fracture-specific patterns in the femur. The study dataset comprised 4933 femoral DXA scans from White British women aged 75 years or older. The total number of fractures was 684, of which 178 were reported at the hip within a follow-up period of five years. BMD maps were computed using the RFA toolkit. For each BMD map, bone age was defined as the age for which the L2-norm between the map and the median atlas at that age is minimised. Next, bone maps were normalised for the estimated bone age. A t-test followed by false discovery rate (FDR) analysis was applied to compare between fracture and non-fracture groups. Excluding the ageing effect revealed subtle localised patterns of loss in BMD oriented in the same direction as principal tensile curves. A new score called f-score was defined by averaging the normalised pixel BMD values over the region with FDR q-value less than 1e–6. The area under the curve (AUC) was 0.731 (95% confidence interval (CI)=0.689–0.761) and 0.736 (95% CI=0.694–0.769) for neck BMD and f-score. Combining bone age and f-score improved the AUC significantly by 3% (AUC=0.761, 95% CI=0.756–0.768) over the neck BMD alone (AUC=0.731, 95% CI=0.726–0.737). This technique shows promise in characterizing spatially-complex BMD changes, for which the conventional region-based technique is insensitive. DXA RFA shows promise to further improve fracture prediction using spatial BMD distribution

Introduction and Objective. The osteocyte, recognized as a major orchestrator of osteoblast and osteoclast activity, is the most important key player during bone remodeling processes. Imbalances that occur during bone remodeling, caused by hormone perturbations or alterations in mechanical loading, can induce bone disease as osteoporosis. Due to limited understanding of the underlying mechanisms, current therapies for osteoporosis cannot adequately address this imbalance because current studies of osteocytes rely on conventional cell culture that cannot recapitulate local in vivo microenvironments for the lack of control of the spatial/temporal distribution of cells and biomolecules. Microfluidics is the science and technology of microscale fluid manipulating and sensing and can help fill this gap. Materials and Methods. We used a microfluidic device to enable the culture of osteocyte-like cells (MLO-Y4 and MLO-A5) in a 3D fashion. Osteocytes were cultured in a perfused and 160 μm high channel and embedded in a bone-like extracellular matrix: osteocytes were embedded in a matrigel- and collagen-based hydrogel enriched with nanostructured hydroxypatite crystals (HA-NP) to mimic bone. To set up the best combination of matrigel enriched with Type I collagen we used fluorescent microspheres and confocal analysis. To evaluate the viability and the expression of osteocytic markers, we used live-dead assay amd immunofluorescent staining and confocal analysis combined with automated quantification. For mineralization, we performed alizarin red staining. Results. Osteocytes in the organ-on-a-chip model showed high viability and, in respect to 2D conventional cell cultures an increased differentiation, as assessed by a live-dead assay and the staining of the osteocytic markers connexin-43 and alkaline phosphatase and the increased mineralization activity. Furthermore, the addition of HA-NP significantly increased the formation of dendrite-like structures spreading through the xyz-axes, as assessed after G-actin immunofluorescence. Conclusions. Using a microfluidic device for MLO-Y4 and MLO-A5 cell cultures, compared to the 2D surfaces, we demonstrated a significant difference in cell differentiation and morphology. In particular, 3D cultures allowed the formation of 3D cell networks and the osteogenic phenotype. As a platform technology, this microfluidic device can function as a novel cell culture model that enables further studies of osteocytes and 3D co-culturing with other bone cells for the screening of anti-osteoporotic drugs

Aims. Using 90% of final height as a benchmark, we sought to develop a quick, quantitative and reproducible method of estimating skeletal maturity based on topographical changes in the distal femoral physis. Patients and Methods. Serial radiographs of the distal femoral physis three years prior to, during, and two years following the chronological age associated with 90% of final height were analyzed in 81 healthy children. The distance from the tip of the central peak of the distal femoral physis to a line drawn across the physis was normalized to the physeal width. Results. A total of 389 radiographs of the distal femur with corresponding Greulich and Pyle bone ages and known chronological ages were measured. Children reached 90% of final height at a mean age of 11.3 years (. sd. 0.8) for girls and 13.2 years (. sd. 0.6) for boys. Linear regression analysis showed higher correlation coefficent in predicting the true age at 90% of final height using chronological age + gender + central peak value (R. 2 . = 0.900) than chronological age + gender (R. 2.  = 0.879) and Greulich and Pyle bone age + gender (R. 2.  = 0.878). Conclusion. Chronological age + gender + central peak value provides more accurate prediction of 90% of final height compared with chronological age + gender and Greulich and Pyle bone age + gender. Cite this article: Bone Joint J 2018;100-B:1106–11

Osteoporosis is a worldwide disease resulting in the increase of bone fragility and enhanced fracture risk in adults. In the context of osteoporotic fractures, bone tissue engineering (BTE), i.e., the use of bone substitutes combining biomaterials, cells, and bone inducers, is a potential alternative to conventional treatments. Pre-clinical testing of innovative scaffolds relies on in vitro systems where the simultaneous presence of osteoblasts (OBs) and osteoclasts (OCs) is required to mimic their crosstalk and molecular cooperation for bone remodelling. To this aim, two composite materials based on type I collagen were developed, containing either strontium-enriched mesoporous bioactive glasses or rod-like hydroxyapatite nanoparticles. Following chemical crosslinking with genipin, the nanostructured materials were tested for 2–3 weeks with an indirect co-culture of human trabecular bone-derived OBs and buffy coat-derived OC precursors. The favourable structural and biological properties of the materials proved to successfully support the viability, adhesion, and differentiation of bone cells, encouraging a further investigation of the two bioactive systems as biomaterial inks for the 3D printing of more complex scaffolds for BTE

Aims. Aseptic loosening is a leading cause of uncemented arthroplasty failure, often accompanied by fibrotic tissue at the bone-implant interface. A biological target, neutrophil extracellular traps (NETs), was investigated as a crucial connection between the innate immune system’s response to injury, fibrotic tissue development, and proper bone healing. Prevalence of NETs in peri-implant fibrotic tissue from aseptic loosening patients was assessed. A murine model of osseointegration failure was used to test the hypothesis that inhibition (through Pad4-/- mice that display defects in peptidyl arginine deiminase 4 (PAD4), an essential protein required for NETs) or resolution (via DNase 1 treatment, an enzyme that degrades the cytotoxic DNA matrix) of NETs can prevent osseointegration failure and formation of peri-implant fibrotic tissue. Methods. Patient peri-implant fibrotic tissue was analyzed for NETs biomarkers. To enhance osseointegration in loose implant conditions, an innate immune system pathway (NETs) was either inhibited (Pad4-/- mice) or resolved with a pharmacological agent (DNase 1) in a murine model of osseointegration failure. Results. NETs biomarkers were identified in peri-implant fibrotic tissue collected from aseptic loosening patients and at the bone-implant interface in a murine model of osseointegration failure. Inhibition (Pad4-/-) or resolution (DNase 1) of NETs improved osseointegration and reduced fibrotic tissue despite loose implant conditions in mice. Conclusion. This study identifies a biological target (NETs) for potential noninvasive treatments of aseptic loosening by discovering a novel connection between the innate immune system and post-injury bone remodelling caused by implant loosening. By inhibiting or resolving NETs in an osseointegration failure murine model, fibrotic tissue encapsulation around an implant is reduced and osseointegration is enhanced, despite loose implant conditions. Cite this article: Bone Joint J 2021;103-B(7 Supple B):135–144

INTRODUCTION. Hip resurfacing offers a more bone conserving solution than total hip replacement (THR) but currently has limited clinical indications related to some poor design concepts and metal ion related issues. Other materials are currently being investigated based on their successful clinical history in THR such as Zirconia Toughened Alumina (ZTA, Biolox Delta, CeramTec, Germany) which has shown low wear rates and good biocompatibility but has previously only been used as a bearing surface in THR. A newly developed direct cementless fixation all-ceramic (ZTA) resurfacing cup offers a new solution for resurfacing however ZTA has a Young's modulus approximately 1.6 times greater than CoCr - such may affect the acetabular bone remodelling. This modelling study investigates whether increased stress shielding may occur when compared to a CoCr resurfacing implant with successful known clinical survivorship. METHODS. A finite element model of a hemipelvis constructed from CT scans was used and virtually reamed to a diameter of 58mm. Simulations were conducted and comparisons made of the ‘intact’ acetabulum and ‘as implanted’ with monobloc cups made from CoCr (Adept®, MatOrtho Ltd, UK) and ZTA (ReCerf ™, MatOrtho Ltd. UK) orientated at 35° inclination and 20° anteversion. The cups were loaded with 3.97kN representing a walking load of 280% for an upper bound height patient with a BMI of 35. The cup-bone interface was assigned a coulomb slip-stick function with a coefficient of friction of 0.5. The percentage change in strain energy density between the intact and implanted states was used to indicate hypertrophy (increase in density) or stress shielding (decrease in density). RESULTS. Implanting both cups changed the strain distribution observed in the hemipelvis, Figure 1. The change in strain distribution was similar between materials and indicated a similar response from the bone, Figure 2. In both implanted cases, the inferior peri-acetabular bone around the implant indicated a reduction in bone strain. The bone remodelling distribution charts show that regardless of threshold remodelling stimulus level (75% in elderly, 50% in younger patients) the CoCr and ZTA cups were expected to produce the same bone response with only a small percentage of the bone in the hemipelvis indicating stress shielding or hypertrophy, Figure 3. DISCUSSION. Currently only metal cups are used for cementless fixation but improvements in design and technology have made it possible to engineer a thin-walled, direct fixation, all-ceramic cup. Both CoCr and ZTA are an order of magnitude greater than the Young's modulus of cortical bone altering the bone strain but changing the material from CoCr to a stiffer ZTA did not change the expected bone remodelling response. Given the clinical history of metal cups without loosening due to bone remodelling, the study indicates that a ZTA cup should not lead to increased stress shielding and is potentially suitable for as a cementless cup for both resurfacing and THR. SIGNIFICANCE. An all-ceramic cup is unlikely to lead to increased stress shielding around the acetabulum due to the change in material. For any figures or tables, please contact the authors directly

Device-associated bacterial infections are a major and costly clinical challenge. This project aimed to develop a smart new biomaterial for implants that helps to protect against infection and inflammation, promote bone growth, and is biodegradable. Gallium (Ga) doped strontium-phosphate was coated on pure Magnesium (Mg) through a chemical conversion process. Mg was distributed in a graduated manner throughout the strontium-phosphate coating GaSrPO4, with a compact structure and a Ga-rich surface. We tested this sample for its biocompatibility, effects on bone remodeling and antibacterial activities including Staphylococcus aureus, S. epidermidis and E. coli - key strains causing infection and early failure of the surgical implantations in orthopaedics and trauma. Ga was distributed in a gradient way throughout the entire strontium-phosphate coating with a compact structure and a gallium-rich surface. The GaSrPO4 coating protected the underlying Mg from substantial degradation in minimal essential media at physiological conditions over 9 days. The liberated Ga ions from the coatings upon Mg specimens inhibited the growth of bacterial tested. The Ga dopants showed minimal interferences with the SrPO4 based coating, which boosted osteoblasts and undermined osteoclasts in in vitro co-cultures model. The results evidenced this new material may be further translated to preclinical trial in large animal model and towards clinical trial. Acknowledgements: Authors are grateful to the financial support from the Australian Research Council through the Linkage Scheme (ARC LP150100343). The authors acknowledge the facilities, and the scientific and technical assistance of the RMIT University and John Curtin School of Medical Research, Australian National University

Wear debris from implant interfaces is the major factor leading to periprosthetic osteolysis. Fibroblast-like synoviocytes (FLSs) populate the intimal lining of the synovium and are in direct contact with wear debris. This study aimed to elucidate the effect of Ti particles as wear debris on human FLSs and the mechanism by which they might participate in the bone remodeling process during periprosthetic osteolysis. FLSs were isolated from synovial tissue from patients, and the condition medium (CM) was collected after treating FLSs with sterilized Ti particles. The effect of CM was analyzed for the induction of osteoclastogenesis or any effect on osteogenesis and signaling pathways. The results demonstrated that Ti particles could induce activation of the NFκB signaling pathway and induction of COX-2 and inflammatory cytokines in FLSs. The amount of RANL in the conditioned medium collected from Ti particle-stimulated FLSs (Ti CM) showed the ability to stimulate osteoclast formation. The Ti CM also suppressed the osteogenic initial and terminal differentiation markers for osteoprogenitors, such as alkaline phosphate activity, matrix mineralization, collagen synthesis, and expression levels of Osterix, Runx2, collagen 1α, and bone sialoprotein. Inhibition of the WNT and BMP signaling pathways was observed in osteoprogenitors after the treatment with the Ti CM. In the presence of the Ti CM, exogenous stimulation by WNT and BMP signaling pathways failed to stimulate osteogenic activity in osteoprogenitors. Induced expression of sclerostin (SOST: an antagonist of WNT and BMP signaling) in Ti particletreated FLSs and secretion of SOST in the Ti CM were detected. Neutralization of SOST in the Ti CM partially restored the suppressed WNT and BMP signaling activity as well as the osteogenic activity in osteoprogenitors. Our results reveal that wear debris-stimulated FLSs might affect bone loss by not only stimulating osteoclastogenesis but also suppressing the bone-forming ability of osteoprogenitors. In the clinical setting, targeting FLSs for the secretion of antagonists like SOST might be a novel therapeutic approach for preventing bone loss during inflammatory osteolysis

Bone homeostasis is a highly regulated process involving pathways in bone as WNT, FGF or BMP, but also requiring support from surrounding tissues as vessels and nerves. In bone diseases, the bone-vessel-nerve triad is impacted. Recently, new players appeared as regulators of bone homeostasis: microRNAs (miRNA). Five miRNAs associated with osteoporotic fractures are already known, among which miR-125b is decreasing bone formation by downregulating human mesenchymal stem cells (hMSCs) differentiation. Other miRNAs, as miR-214 (in cluster with miR-199a), are secreted by osteoclasts to regulate osteoblasts and inhibit bone formation. This forms a very complex regulatory network. hMSCs and osteoblasts (n=3) were transfected with mimic/antagomiR of miR-125b, miR-199a-5p or miR-214, or with a scrambled miRNA (negative control) in osteogenic differentiation calcium-enriched medium (Ca++). Mineralization was assessed by Alizarin Red/CPC staining, miRNA expression by qPCR and protein by western blotting. Exposure of hMSCs or osteoblasts to Ca++ increased mineralization compared to basal medium. hMSCs transfected with miR-125b mimic in Ca++ presented less mineralization compared to scramble. This correlated with decreased levels of BMPR2 and RUNX2. hMSCs transfected with miR-125b inhibitor presented higher mineralization. Interestingly, hMSCs transfected with miR-214 mimic in Ca++ presented no mineralization while miR-214 inhibitor increased mineralization. No differences were observed in hMSCs transfected with miR-199a-5p modulators. On the contrary, osteoblasts transfected with miR-199a-5p mimic present less mineralization than scrambled-transfected and same was observed for miR-214 and miR-125b mimics. We highlight that miR-125b and miR-214 decrease mineralization of hMSCs in calcium-enriched medium. We noticed that miR-199a-5p is able to regulate mineralization in osteoblasts but not in hMSCs suggesting that this effect is cell-specific. Interestingly, the cluster miR-199a/214 is known as modulator of vascular function and could thus contribute to bone remodeling via different ways. With this work we slightly open the door to possible therapeutic approaches for bone diseases

We had previously reported on early outcomes on a new fluted, titanium, monobloc stem with a three degree taper that has been designed for challenging femoral reconstruction in the setting of extensive bone loss. The aim of this study was to report its mid-term clinical and radiographic outcomes. This is a retrospective review of prospectively collected data carried out at a single institution between Jan 2017 and Dec 2019. 85 femoral revisions were performed using a new tapered, fluted, titanium, monobloc (TFTM) revision stem. Complications, clinical and radiographic data were obtained from medical records and a locally maintained database. Clinical outcomes were assessed using the Oxford Hip Score (OHS) and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). All post-operative radiographs were analysed for subsidence, osteolysis and femoral cortical bone remodelling. Mean follow-up was 60 months (range 28–84 months). Subsidence of 1.2 mm was noted in one patient. No cases of clinically significant subsidence (10 mm) were observed. At final follow-up, a statistically significant improvement was noted in functional outcome scores. The mean OHS preoperatively and at final follow-up were 24 (SD 13) and 42 (SD15). p = 0.04 mean difference 18 (95% CI 15–22). The mean WOMAC scores preoperatively and at final follow-up were 62 (SD23) and 88 (SD7) respectively (p < 0.001, mean difference 26; 95% CI 21–34). No stem fractures were noted within the follow-up period. Two patients had revision of the stem's one for infection and another for persistent pain. Positive mid-term clinical and radiological outcomes have been observed with this tapered, fluted, titanium, monobloc stem. Based on these results, this implant may be considered as a viable option in the majority of uncemented femoral revisions

Low-energy fractures complications are a major public health issue that make osteoporosis even worse. In sub-Saharan Africa, the prevalence of osteoporosis varies from 18.2% to 65.8%. There was no change in bone mineral density between HIV-infected and non-HIV-infected women in Sub-Saharan Africa, where HIV is widespread. Other investigations that demonstrated that HIV-infected people had poor BMD both before and after starting anti-retroviral treatment did not consistently show a low BMD finding. Inflammation-mediated bone remodelling has been associated with low BMD in HIV-infected patients. Antiretroviral Therapy has been demonstrated to exacerbate bone loss in addition to the pre-existing intrinsic risk of developing osteoporosis. Question: Is there loss of bone in HIV-infected patients before initiating ART?. The patients who were HIV-positive and enrolled in the ADVANCE research were retrospectively reviewed on a desk. All of the 1053 individuals in the ADVANCE research had a DXA scan performed to evaluate BMD as part of the initial screening and recruitment approach. The ADVANCE research enrolled HIV-positive people and randomly assigned them to three ART arms. A total of 400 patients were reviewed. Of these 400 records reviewed, 62.3% were female. 80% of the participants were younger than 40 years old, and 3% were older than 50 years. 82% were virally suppressed with less than 50 viral copies. The prevalence of osteopenia was 25.5% and osteoporosis was 2.8%, observed in predominantly African female participants aged between 30 and 39 years. The findings of this study confirm that there is pre-existing bone loss among HIV-infected ART naïve individuals. Approximately 28.3% in our study had clinically confirmed evidence of bone loss and of these, 2.8% of the entire cohort had osteoporosis. Bone loss was most prevalent in black females who are virologically suppressed

Distal radius fractures are the most common osteoporotic fractures among women. The treatment of these fractures has been shifting from a traditional non-operative approach to surgery, using volar locking plate (VLP) technology. Surgery, however, is not without risk, complications including failure to restore an anatomic reduction, fracture re-displacement, and tendon rupture. The VLP implant is also marked by bone loss due to stress-shielding related to its high stiffness relative to adjacent bone. Recently, a novel internal, composite-based implant, with a stiffness less than the VLP, was designed to eradicate the shortcomings associated with the VLP implant. It is unclear, however, what effect this less-stiff implant will have upon adjacent bone density distributions long-term. The objective of this study was to evaluate the long-term effects of the two implants (the novel surgical implant and the gold-standard VLP) by using subject-specific finite element (FE) models integrated with an adaptive bone formation/resorption algorithm. Specimen: One fresh-frozen human forearm specimen (female, age = 84 years old) was imaged using CT and was used to create a subject-specific FE model of the radius. Finite element modeling: In order to simulate a clinically relevant (unstable) fracture of the distal radius, a wedge of bone was removed from the model, which was approximately 10 mm wide and centered 20 mm proximal to the tip of the radial styloid. Bone remodeling algorithm: A strain-energy density (SED) based bone remodeling theory was used to account for bone remodeling. With this approach, bone density decreased linearly when SED per bone density was less than 67.5 µJ/g and increased when it was more than 232.5 µJ/g. When it was in the lazy zone (67.5 to 232.5 µJ/g), no changes in density occurred. Boundary conditions: A 180 N quasi-static force representing the scaphoid, and a 120 N quasi-static force representing the lunate was applied to the radius. The midshaft of the radius was constrained. FE outcomes: To examine the effects of stress shielding associated with each implant, the long-term changes of bone density within proximal transverse cross-sections of radius were inspected. The regional density analysis focused on three transverse cross-sections. The transverse cross-sections were positioned proximal to the subchondral plate, and were distanced 50 (cross-section A), 57 (cross-section B), and 64 mm (cross-section C) from the subchondral endplate. For both implants in all three cross-sections, cortical bone was reserved completely at the volar side. On the dorsal side, the cortical bone was completely resorbed in the VLP model. In all cross-sections, the averaged resultant density was higher for the “novel implant”. The difference ranged from 33% (cross-section A) to 36% (cross-section C) in favor of the “novel implant”. On average, the density values of the novel implant were 34% higher in transverse cross-sections (A, B, and C). This study showed that the novel implant offered higher density distributions compared to the VLP, which suggests that the novel implant may be superior to the VLP in terms of avoiding stress shielding

Abstract. OBJECTIVES. Bone health deterioration is a major public health issue. General guidelines for the limitation of bone loss prescribe a healthy lifestyle and a minimum level of physical activity. However, there is no specific recommendation regarding targeted activities that can effectively maintain lumbar spine bone health. To provide a better understanding of such influencing activities, a new predictive modelling framework was developed to study bone remodelling under various loading conditions. METHODS. The approach is based on a full-body subject-specific musculoskeletal model [1] combined with structural finite element models of the lumbar vertebrae. Using activities recorded with the subject, musculoskeletal simulations provide physiological loading conditions to the finite element models which simulate bone remodelling using a strain-driven optimisation algorithm [2]. With a combination of daily living activities representative of a healthy lifestyle including locomotion activities (walking, stair ascent and descent, sitting down and standing up) and spine-focused activities involving twisting and reaching, this modelling framework generates a healthy bone architecture in the lumbar vertebrae. The influence of spine-focused tasks was studied by adapting healthy vertebrae to an altered loading scenario where only locomotion activities were performed. RESULTS. The spine-focused activities were responsible for 57% of the overall bone mechanical stimulus of the five lumbar vertebrae. Cortical bone maintenance was more influenced by these activities in the superior vertebrae than in the inferior ones, with a stimulus degradation of 74% in L1 against 24% in L5 when adapted to the altered loading scenario. Trabecular bone stimulus degradation varied between 53% and 68%. CONCLUSION. The study suggests that locomotion activities are insufficient to maintain lumbar spine bone health. When appropriate, larger spine movements should be recommended as part of the minimum daily physical activities. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Stimulation of the mechanosensitive ion channel, Piezo1 promotes bone anabolism and SNPs in the Piezo1 locus are associated with changes in fracture risk. Osteocytes function as critical regulators of bone homeostasis by sensing mechanical signals. The current study used a human, cell-based physiological, 3D in vitro model of bone to determine whether loading of osteocytes in vitro results in upregulation of the Piezo1 pathway. Human Y201 MSCs, embedded in type I collagen gels and differentiated to osteocytes for 7-days, were subjected to pathophysiological load (5000 µstrain, 10Hz, 5 mins; n=6) with unloaded cells as controls (n=4). RNA was extracted 1-hr post load and assessed by RNAseq analysis. To mimic mechanical load and activate Piezo1, cells were differentiated to osteocytes for 13 days and treated ± Yoda1 (5µM, 2- and 24-hs, n=4); vehicle treated cells served as controls (n=4). RNA was subjected to RT-qPCR and data normalised to the housekeeping gene, YWHAZ. Media was analysed for IL6 release by ELISA. Mechanical load upregulated Piezo1 gene expression (16.5-fold, p<0.001) and expression of the transcription factor NFATc1, and matricellular protein CYR61, known regulators of Piezo1 mechanotransduction (3-fold; p= 5.0E-5 and 6.8-fold; p= 6.0E-5, respectively). After 2-hrs, Yoda1 increased the expression of the early mechanical response gene, cFOS (11-fold; p=0.021), mean Piezo1 expression (2.3-fold) and IL-6 expression (103-fold, p<0.001). Yoda1 increased the release of IL6 protein after 24 hours (7.5-fold, p=0.001). This study confirms Piezo1 as an important mechanosensor in osteocytes. Piezo1 activation mediated an increase in IL6, a cytokine that drives inflammation and bone resorption providing a direct link between mechanical activation of Piezo1, bone remodeling and inflammation, which may contribute to mechanically induced joint degeneration in diseases such as osteoarthritis. Mechanistically, we hypothesize this may occur through promoting Ca2+ influx and activation of the NFATc1 signaling pathway

Osteoclasts (OCs) are multinucleated cells that play a pivotal role in skeletal development and bone remodeling. Abnormal activation of OCs contributes to the development of bone-related diseases, such as osteoporosis, bone metastasis and osteoarthritis. Restoring the normal function of OCs is crucial for bone homeostasis. Recently, RNA therapeutics emerged as a new field of research for osteoarticular diseases. The aim of this study is to use non-coding RNAs (ncRNAs) to molecularly engineer OCs and modulate their function. Specifically, we investigated the role of the microRNAs (namely miR-16) and long ncRNAs (namely DLEU1) in OCs differentiation and fusion. DLEU1/DLEU2 region, located at chromosome 13q14, also encodes miR-15 and miR-16. Our results show that levels of these ncRNA transcripts are differently expressed at distinct stages of the OCs differentiation. Specifically, silencing of DLEU1 by small interfering RNAs (siDLEU1) and overexpression of miR-16 by synthetic miRNA mimics (miR-16-mimics) led to a significant reduction in the number of OCs formed per field (OC/field), both at day 5 and 9 of the differentiation stage. Importantly, time-lapse analysis, used to track OCs behavior, revealed a significant decrease in fusion events after transfection with siDLEU1 or miR-16-mimics and an alteration in the fusion mode and partners. Next, we investigated the migration profile of these OCs, and the results show that only miR-16-mimics-OCs, but not siDLEU-OCs, have a lower percentage of immobile cells and an increase in cells with mobile regime, compared with controls. No differences in cell shape were found. Moreover, mass-spectrometry quantitative proteomic analysis revealed independent effects of siDLEU1 and miR-16-mimics at the protein levels. Importantly, DLEU1 and miR-16 act by distinct processes and pathways. Collectively, our findings support the ncRNAs DLEU1 and miR-16 as therapeutic targets to modulate early stages of OCs differentiation and, consequently, to impair OC fusion, advancing ncRNA-therapeutics for bone-related diseases. Acknowledgements: Authors would like to thank to AO CMF / AO Foundation (AOCMFS-21-23A). SRM and MIA are supported by FCT (SFRH/BD/147229/2019 and BiotechHealth Program; CEECINST/00091/2018/CP1500/CT0011, respectively)

Aims. The aim of this retrospective study was to assess the incidence of early periprosthetic femoral fracture (PFF) associated with Charnley-Kerboull (CK) femoral components cemented according to the ‘French paradox’ principles through the Hueter anterior approach (HAA) in patients older than 70 years. Methods. From a prospectively collected database, all short CK femoral components implanted consecutively from January 2018 to May 2022 through the HAA in patients older than 70 years were included. Exclusion criteria were age below 70 years, use of cementless femoral component, and approaches other than the HAA. A total of 416 short CK prostheses used by 25 surgeons with various levels of experience were included. All patients had a minimum of one-year follow-up, with a mean of 2.6 years (SD 1.1). The mean age was 77.4 years (70 to 95) and the mean BMI was 25.3 kg/m. 2. (18.4 to 43). Femoral anatomy was classified according to Dorr. The measured parameters included canal flare index, morphological cortical index, canal-calcar ratio, ilium-ischial ratio, and anterior superior iliac spine to greater trochanter (GT) distance. Results. Among the 416 THAs, two PFFs (0.48% (95% confidence interval 0.13 to 1.74)) were observed, including one Vancouver type B2 fracture 24 days postoperatively and one intraoperative Vancouver type B1 fracture. Valgus malalignment and higher canal bone ratio were found to be associated with PFF. Conclusion. This study demonstrated that short CK femoral components cemented according to the French paradox were associated with a low rate of early PFF (0.48%) in patients aged over 70 years. Longer follow-up is warranted to further evaluate the rate of fracture that may occur during the bone remodelling process and with time. Cite this article: Bone Joint J 2024;106-B(3 Supple A):67–73

Several electrical fields are known to be present in bone tissue as originally described by Fukada and Yasuda in the year 1957. Intrinsic voltages can derive from bone deformation and reversely lead to mechanical modifications, called the piezoelectric effect. This effect is used in the clinic for the treatment of bone defects by applying electric and magnetic stimulation directly to the bone supplied with an implant such as the electroinductive screw system. Through this system a sinusoidal alternating voltage with a maximum of 700 mV can be applied which leads to an electric field of 5–70 V/m in the surrounding bone. This approach is established for bone healing therapies. Despite the established clinical application of electrical stimulation in bone, the fundamental processes acting during this stimulation are still poorly understood. A better understanding of the influence of electric fields on cells involved in bone formation is important to improve therapy and clinical success. To study the impact of electrical fields on bone cells in vitro, Ti6Al4V electrodes were designed according to the pattern of the ASNIS III s screw for a 6-well system. Osteoblasts were seeded on collagen coated coverslip and placed centred on the bottom of each well. During four weeks the cells were stimulated 3×45 min/d and metabolic and alkaline phosphatase (ALP) activity as well as gene expression of cells were analysed. Furthermore, supernatants were collected and proteins typical for bone remodelling were examined. The electrical stimulation did not exert a significant influence on the metabolic activity and the ALP production in cells over time using these settings. Gene expression of BSP and ALP was upregulated after the first 3 days whereas OPG was increased in the second half after 14 days of electrical stimulation. Moreover, the concentration of the released proteins OPG, IL-6, DKK-1 and OPN increased when cells were cultivated under electrical stimulation. However, no changes could be seen for essential markers, like RANKL, Leptin, BMP-2, IL-1beta and TNF-alpha. Therefore, further studies will be done with osteoblasts and osteoclasts to study bone remodelling processes under the influence of electrical fields more in detail. This study was supported by the German Research Foundation (DFG) JO 1483/1-1