Aims. Osteoporosis is characterized by decreased trabecular bone volume, and microarchitectural deterioration in the medullary cavity. Interleukin-19 (IL-19), a member of the IL-10 family, is an anti-inflammatory cytokine produced primarily by macrophages. The aim of our study was to investigate the effect of IL-19 on osteoporosis. Methods. Blood and femoral bone marrow suspension IL-19 levels were first measured in the lipopolysaccharide (LPS)-induced bone loss model. Small interfering RNA (siRNA) was applied to knock down IL-19 for further validation. Thereafter, osteoclast production was stimulated with IL-19 in combination with mouse macrophage colony-stimulating factor (M-CSF) and receptor activator of nuclear factor-κB ligand (RANKL). The effect of IL-19 was subsequently evaluated using tartrate-resistant acid phosphatase (TRAP) staining and quantitative real-time polymerase chain reaction (RT-qPCR). The effect of IL-19 on osteoprotegerin (OPG) was then assessed using in vitro recombinant IL-19 treatment of primary osteoblasts and MLO-Y4 osteoblast cell line. Finally, transient transfection experiments and chromatin immunoprecipitation (ChIP) experiments were used to examine the exact mechanism of action. Results. In the LPS-induced bone loss mouse model, the levels of IL-19 in peripheral blood serum and femoral bone marrow suspension were significantly increased. The in vivo results indicated that global IL-19 deletion had no significant effect on RANKL content in the serum and bone marrow, but could increase the content of OPG in serum and femoral bone marrow, suggesting that IL-19 inhibits OPG expression in bone marrow mesenchymal stem cells (BMSCs) and thus increases bone resorption. Conclusion. IL-19 promotes bone resorption by suppressing OPG expression in BMSCs in a LPS-induced bone loss mouse model, which highlights the potential benefits and side effects of IL-19 for future clinical applications. Cite this article: Bone Joint Res 2023;12(11):691–701

Aims. Transcription factor nuclear factor kappa B (NF-κB) plays a major role in the pathogenesis of chronic inflammatory diseases in all organ systems. Despite its importance, NF-κB targeted drug therapy to mitigate chronic inflammation has had limited success in preclinical studies. We hypothesized that sex differences affect the response to NF-κB treatment during chronic inflammation in bone. This study investigated the therapeutic effects of NF-κB decoy oligodeoxynucleotides (ODN) during chronic inflammation in male and female mice. Methods. We used a murine model of chronic inflammation induced by continuous intramedullary delivery of lipopolysaccharide-contaminated polyethylene particles (cPE) using an osmotic pump. Specimens were evaluated using micro-CT and histomorphometric analyses. Sex-specific osteogenic and osteoclastic differentiation potentials were also investigated in vitro, including alkaline phosphatase, Alizarin Red, tartrate-resistant acid phosphatase staining, and gene expression using reverse transcription polymerase chain reaction (RT-PCR). Results. Local delivery of NF-κB decoy ODN in vivo increased osteogenesis in males, but not females, in the presence of chronic inflammation induced by cPE. Bone resorption activity was decreased in both sexes. In vitro osteogenic and osteoclastic differentiation assays during inflammatory conditions did not reveal differences among the groups. Receptor activator of nuclear factor kappa Β ligand (Rankl) gene expression by osteoblasts was significantly decreased only in males when treated with ODN. Conclusion. We demonstrated that NF-κB decoy ODN increased osteogenesis in male mice and decreased bone resorption activity in both sexes in preclinical models of chronic inflammation. NF-κB signalling could be a therapeutic target for chronic inflammatory diseases involving bone, especially in males. Cite this article: Bone Joint Res 2024;13(1):28–39

Recently, concerns arose over the medial tibial bone resorption of a novel cobalt-chromium (CoCr) implant. This study aimed to investigate the effects of tibial component material, design, and patient factors on periprosthetic bone resorption and to determine its association with clinical outcomes after total knee arthroplasty (TKA). A total of 462 primary TKAs using five types of implants were included. To evaluate tibial periprosthetic bone resorption, we assessed radiolucent lines (RLL) and change in bone mineral density at the medial tibial condyle (BMDMT). Factors related to bone resorption were assessed using regression analysis. Clinical outcomes were also evaluated with respect to periprosthetic bone resorption. Compared to titanium (Ti) implants, CoCr implants showed a higher incidence of complete RLL (23.1% vs. 7.9% at two years post-TKA) and a greater degree of BMDMT reduction. However, there was no significant difference between the implants made of the same material. Increased medial tibial bone resorption was associated with male sex, osteoporosis, larger preoperative varus deformity, longer follow-up period, and lower body mass index. The periprosthetic bone resorption was not associated with clinical outcomes including changes in range of motion and WOMAC score. Furthermore, no cases warranted additional surgery. Periprosthetic bone resorption was associated with implant material but not with implant design. Moreover, patient factors were related to the medial tibial bone resorption post-TKA. However, the periprosthetic bone resorption was not associated with short-term clinical outcomes. We contend that researchers should incorporate integrative considerations when developing and assessing novel implants

Bone remodeling effects is a significant issue in predicting long term stability of hip arthroplasty. It has been frequently observed around the femoral components especially with the implantation of prosthesis stem. Presence of the stiffer materials into the femur has altering the stress distribution and induces changes in the architecture of the bone. Phenomenon of bone resorption and bone thickening are the common reaction in total hip arthroplasty (THA) which leading to stem loosening and instability. The objectives of this study are (i) to develop inhomogeneous model of lower limbs with hip osteoarthritis and THA and (ii) to predict the bone resorption behavior of lower limbs for both cases. Biomechanical evaluations of lower limbs are established using the finite element method in predicting bone remodeling process. Lower limbs CT-based data of 79 years old female with hip osteoarthritis (OA) are used in constructing three dimensional inhomogenous models. The FE model of lower limbs was consisted of sacrum, left and right ilium and both femur shaft. Bond between cartilage, acetabulum and femoral head, sacrum and ilium were assumed to be rigidly connected. The inhomogeneous material properties of the bone are determined from the Hounsfield unit of the CT image using commercial biomedical software. A load case of 60kg body weight was considered and fixed at the distal cut of femoral shaft. For THA lower limbs model, the left femur which suffering for hip OA was cut off and implanted with prosthesis stem. THA implant is designed to be Titanium alloy and Alumina for stem and femoral ball, respectively. Distribution of young modulus of cross-sectional inhomogeneous model is presented in Fig. 2 while model of THA lower limbs also shown in Fig. 2. Higher values of young modulus at the outer part indicate hard or cortical bone. Prediction of bone resorption is discussed with the respect of bone mineral density (BMD). Changes in BMD at initial age to 5 years projection were simulated for hip OA and THA lower limbs models. The results show different pattern of stress distribution and bone mineral density between hip OA lower limbs and THA lower limbs. Stress is defined to be dominant at prosthesis stem while femur experienced less stress and leading to bone resorption. Projection for 5 years follow up shows that the density around the greater tronchanter appears to decrease significantly

Aseptic loosening is currently the leading cause of failure of total hip arthroplasty. The aetiology of periprosthetic bone resorption is currently under intense investigation. Wear particles are produced from the articulating surface of the femoral and acetabular components. These particles gain access to the bone-cement interface where they are phagocytosed by macrophages. Particle stimulated macrophages differentiate into bone resorping osteoclasts. This leads to periprosthetic bone resorption and subsequent implant loosening. Nuclear factor kappa B (NFκB) is a transcription factor known to be activated by pathogenic stimuli in a variety of cells. The activation of NFkB would appear to be the primary event in the activation of particle stimulated macrophages in the periprosthetic membrane. NFκB subsequently causes a cascade of events leading to the release of bone resorbing cytokines, namely interleukin-6 (IL-6) and tumour necrosis factor α (TNFα). The aim of our study was to ascertain if bone resorption could be prevented in vitro by the addition of PDTC, an NFkB inhibitor to particle stimulated macrophages. Human monocytes were isolated and cultured from healthy volunteers. The monocyte/macrophage cell line was differentiated into osteoclasts by the addition of alumina particles and allowed to adhere onto bone slices. The NFkB inhibitor, PDTC, has added to the cultured osteoclasts. Bone resorption was analysed by counting the number of resorption pits in each bone slice. The addition of PDTC to stimulated macrophages reduced the number of resorption pits by greater than 40% compared to control. This is a unique and promising finding that may offer a future therapeutic strategy for the prevention of periprosthetic bone resorption and therefore aseptic loosening in total hip arthoplasty

Osteoclastic bone resorption is a highly dynamic process that requires the tight ordering of intracellular trafficking events in order to maintain the structural and functional polarization of the ruffled border and basolateral domains. Rab3 proteins are a subfamily of GTPases, known to mediate membrane transport in eukaryotic cells and play a role in exocytosis. Our recent data indicates that Rab3D modulates a post-TGN trafficking step that is required for osteoclastic bone resorption (1). Here, to identify down-stream regulatory molecules of Rab3D, we have performed a yeast two-hybrid screen. Amongst several candidate Rab3D-interacting proteins identified, Rab3D was found to associate with calmodulin, an established regulator of osteoclastic bone resorption. As an initial effort to better define the interaction between Rab3D and calmodulin, we generated several mutants of Rab3D which interfere with the GDP/GTP nucleotide exchange (Rab3DQ81L, Rab3DN135I) and/or membrane attachment of Rab3D (Rab3D-CXC). By in vivo bioluminescence resonance energy transfer (BRET) assay, Calmodulin was found to associate equivalently with wild type Rab3D as well as Rab3DN135I and Rab-3DCXC variants. Over expression of constitutively active Rab3D (Rab3DQ81L) enhanced this interaction suggesting that the active form of Rab3D (i.e. GTP-bound) might recruit additional effector molecules which further potentiate it’s binding to calmodulin. In an attempt to address the impact of calmodulin activity on Rab3D-calmodulin interaction and osteoclastic bone resorption, we performed complementary BRET and in vitro bone resorption assays in the presence of the calmodulin inhibitor, calmidazolium chloride. Interestingly, we show that suppression of calmodulin activity via calmidazolium chloride impairs the association of Rab3D with calmodulin, an affect that correlates with a disruption in osteoclastic bone resorption. We propose that the recruitment of calmodulin by Rab3D might be an important requirement for osteoclast-mediated bone resorption

A heavy infiltrate of foreign-body macrophages is commonly seen in the fibrous membrane which surrounds an aseptically loose cemented implant. This is in response to particles of polymethylmethacrylate (PMMA) bone cement and other biomaterials. We have previously shown that monocytes and macrophages responding to particles of bone cement are capable of differentiating into osteoclastic cells which resorb bone. To determine whether the radio-opaque additives barium sulphate (BaSO. 4. ) and zirconium dioxide (ZrO. 2. ) influence this process, particles of PMMA with and without these agents were added to mouse monocytes and cocultured with osteoblast-like cells on bone slices. Osteoclast differentiation, as shown by the presence of the osteoclast-associated enzyme tartrate-resistant acid phosphatase (TRAP) and lacunar bone resorption, was observed in all cocultures. The addition of PMMA alone to these cocultures caused no increase in TRAP expression or bone resorption relative to control cocultures. Adding PMMA particles containing BaSO. 4. or ZrO. 2. , however, caused an increase in TRAP expression and a highly significant increase in bone resorption. Particles containing BaSO. 4. were associated with 50% more bone resorption than those containing ZrO. 2. . Our results suggest that radio-opaque agents in bone cement may contribute to the bone resorption of aseptic loosening by enhancing macrophage-osteoclast differentiation, and that PMMA containing is BaSO. 4. likely to be associated with more osteolysis than that containing ZrO. 2.

Introduction. Revision total knee arthroplasy (TKA) has been often used with a metal block augmentation for patients with poor bone quality. However, bone resorption beneath metal block augmentation has been still reported and little information about the reasons of the occurrence of bone resorption is available. The aim of the current study is to identify a possibility of the potential occurrence of bone resorption beneath metal block augmentation, through evaluation of strain distribution beneath metal block augmentation in revision TKA with metal block augmentation, during high deep flexion. Materials and Method. LOSPA, revision TKA with a metal block augmentation (Baseplate size #5, Spacer size #5, Stem size Φ9, L30, Augment #5 T5) was considered in this study. For the test, the tibia component of LOSPA was implanted to the tibia sawbone (left, #3401, Sawbones EuropeAB, Malmö, Sweden), which was corresponded to a traditional TKR surgical guideline. The femoral component of LOSPA was mounted to a customized jig attached to the Instron 8872 (Instron, Norwood, MA, USA), which was designed specially to represent the angles ranged from 0° to 140° with consideration of a rollback of knee joint (Figure. 1). Here, a compressive load of 1,600N (10N/s) was applied for each angle. Strain distribution was then measured from rossete strain gauge (Half Bridge type, CAS, Seoul, Korea) together (Figure 1). Results and Discussions. The strain distribution on the cortical bone of the tibia was shown in Figure 2. The results showed that the strains on the posterior region were gradually increased from extension to high deep of the knee joint and generally larger than the other regions. In contrast to the results on the posterior region, the strains on the medial region were gradually decreased after 60° or 90° flexion position and relatively lower than the other regions. Particularly, the strains on the medial region were generally lower than 50–100 µstrain, which is known as critical value range able to inducing bone resorption, during high deep flexion. This fact indicate that a possibility of the potential bone resorption occurrence in revision TKA used with a metal block augmentation may be relatively increased in patients who are frequently exposed to a personal lifestyle history with the loading conditions of the high flexion. This study may be valuable by identifying for the first time a possibility of the potential bone resorption occurrence through evaluation of the strain distribution beneath metal block augmentation in revision TKA used with a metal block augmentation during high deep flexion. Conclusion. A possibility of the potential bone resorption occurrence in revision TKA used with a metal block augmentation may be dependent on loading patterns applied on the knee joint related to personal lifestyle history. Particularly, it may be relatively increased in patients who are frequently exposed to a personal lifestyle history with the loading conditions of the high flexion. Acknowledgements. This study was supported by a grant from the New Technology Product Evaluation Technical Research project, Ministry of Food and Drug Safety (MFDS), Republic of Korea

Summary Statement. In this study it has been considered an alternative therapeutic approach to bone resorption diseases by using plant decoctions to improve adherence from patients to the treatment. In this context, Hemidesmus indicus represents a possible therapeutic or adjuvant natural compound. Introduction. The acceleration of bone remodelling, with an excessive osteoclastogenesis or activation of mature osteoclasts, causes the loss of bone mass which is implicated in bone resorption diseases. Conventional therapies are expensive and limited by systemic toxicity and low drug bioavailability. Alternative treatments that are not only effective but also administered employing formulations and dosages different from conventional ones, may improve adherence to therapy, having a positive influence on clinical outcomes. Experimental evidence have attributed antiproliferative and apoptosis inducing activity on different cell lines (including osteoclast precursors or mature osteoclasts) to four plants used in Ayurvedic medicine: Asparagus racemosus (AR), Emblica officinalis (EO), Hemidesmus indicus (HI) and Rubia cordifolia (RC) These properties could be helpful in the treatment of some bone resorption diseases. In order to clarify the possible therapeutic effects of these compounds, the anti-osteoclast activity of their decoctions were evaluated. Methods. The anti-osteoclast activity of natural compounds was evaluated on primary cultures of human osteoclasts generated by isolating peripheral blood monocytes from buffy coat and treating cells with medium supplemented with differentiating factors. To evaluate the effect on osteoclastogenesis, osteoclast precursors were treated with different concentrations of plant decoctions and characterised by the formation of multinucleated cells and the expression of tartrate-resistant acid phosphatase. To evaluate the osteoclasts apoptosis inducing activity mature osteoclasts were treated with the compounds and stained with Hoechst 33258, to make clear the possible nuclear pyknosis, and phalloidin-TRITC to highlight the structure of the typical osteoclast actin ring. The toxicity of compounds on osteogenic precursors was evaluated by the Alamar Blue assay after 7 days of cells treatment with bioactive concentrations of decoctions. Results. At the higher concentrations, all the decoctions had inhibited osteoclastogenesis with an effect similar to that of alendronate (positive control), but only HI was effective like alendronate at lower concentrations. The percentage of apoptotic osteoclasts was very low in control cultures (30 ± 2%), but increased significantly when cells were exposed to the highest concentration of EO (P < 0.001), HI (P < 0.001), and RC (P < 0.05). It was not observed the same effect when cells were exposed to the highest concentration of AR. At the highest concentrations AR has completely inhibited the proliferation of osteogenic precursors, EO was toxic at all tested concentrations, while RC was toxic only at the highest ones. On the contrary, HI showed absence of toxicity on osteogenic precursors at all tested concentrations. Conclusion. An ideal anti-resorption drug should exert an anti-osteoclastic activity without interfering with the proliferative capacity of osteogenic precursors. For these reasons, among all the plants evaluated in this study, HI represents a possible therapeutic candidate. In fact, it demonstrated the greater effectiveness of anti-osteoclast activity, both in terms of inhibition of osteoclastogenesis that induction of apoptosis, but showed no toxicity on osteogenic precursors

We investigated the possibility that the macrophages which are seen around implants may stimulate bone resorption and cause loosening. We found that macrophages release mediators that stimulate bone resorption, and that the amount of resorption increased by between 2.5 and 10 times when the macrophages adhered to a foreign surface. This bone resorption depended on the surface energy and roughness of the foreign surface, varying with these physical properties rather than with the chemical nature of the material. It is concluded that loosening of orthopaedic implants is likely to be influenced by the surface energy and roughness of the implant

We investigated in vitro a mechanism by which particulate debris may induce bone resorption and cause implant loosening. We first studied two standard particles: latex, which is considered to be inert, and zymosan, which is inflammatory. Macrophages that phagocytosed either particle became activated, and stimulated 15 times as much bone resorption as did control macrophages. For activation to occur, 100 times more latex than zymosan had to be phagocytosed. We also found that bone cement and polyethylene particles activated macrophages in a similar manner, and that the necessary amounts of these were intermediate between those of latex and zymosan. None of the particles were toxic. It was concluded that implant loosening may result from bone resorption stimulated by mediators released by macrophages that have phagocytosed particles of bone cement or polyethylene

Summary Statement. Obovatol inhibits receptor activator of nuclear factor kappa B ligand (RANKL)-induced osteoclastogenesis and prevents inflammatory bone loss in mice. Introduction. Adult skeletal mass and integrity are maintained by balancing osteoclast-mediated bone resorption and osteoblast-induced bone formation during bone remodeling. Abnormal increases in osteoclastic bone resorption can lead to excessive bone destruction as observed in osteoporosis, rheumatoid arthritis, and metastatic cancers Therefore, Modulation of osteoclast formation and function is a promising strategy for the treatment of bone-destructive diseases. To search for compounds that inhibit osteoclast formation, we tested the effect of obovatol, a natural product isolated from the medicinal plant Magnolia obovata, on osteoclastogenesis and inflammatory bone loss. Methods. Osteoclastogenesis was assessed using bone marrow-derived macrophages. RANKL signaling was assessed by immunoblotting and apoptosis by cell death ELISA assay. Actin ring staining and resorption pit assay was performed. Bone morphometric parameters were determined using a microcomputed tomography system. Results. We found that obovatol strongly inhibited osteoclast formation from bone marrow-derived macrophages in a dose-dependent manner without cytotoxicity. Obovatol significantly suppressed RANKL-induced activation of NF-κB, JNK, and ERK signaling pathways. Obovatol also inhibited RANKL-induced expression of the genes c-Fos and nuclear factor of activated T cells c1, which are transcription factors important for osteoclastogenesis. In addition to osteoclast differentiation, obovatol blocked cytoskeletal organization and abrogated the bone resorbing activity of mature osteoclast. Obovatol also accelerated osteoclast apoptosis through the induction of caspase-3 activation. Consistent with its in vitro anti-resorptive effect, obovatol prevented bone loss induced by lipopolysaccharide (LPS) in vivo. Conclusion. Our findings demonstrate that obovatol, a natural compound isolated from Magnolia obovata, suppresses the differentiation, function, and survival of osteoclasts. Furthermore, obovatol protected against LPS-induced bone loss in vivo. Therefore, we suggest that obovatol may have therapeutic potential for the treatment of bone-destructive diseases characterised by increased osteoclast number and/or activity

Mast cells (MC), the tissue-based effector cells in allergic diseases, have many functions. Within bone tissue, they have been linked with new blood vessel formation and marrow fibrosis and it has been proposed that they are capable of promoting osteoclastic bone resorption. MC numbers are known to increase in a number of osteolytic conditions e.g. osteoporosis, hyperparathyroidism and periodontitis. In fracture callus, too, large numbers of MC are present, especially during the onset of remodelling where it is believed they may be responsible for osteoclast recruitment and/or differentiation. The aim of this study was to look for further evidence of mast cell (MC) involvement in pathological bone resorption. MC activity was assessed in tissue sections of osteolytic conditions including Paget’s disease of bone, rheumatoid arthritis and fibrous dysplasia together with several benign and malignant bone tumours. MCs were identified by toluidine blue staining and by immunostaining with a commercial antibody against MC tryptase. Extensive infiltration of mast cells was observed in fibrous dysplasia, rheumatoid arthritis and Paget’s disease of bone and mast cell accumulation was seen at the bone resorbing margin of a number of enlarging bone tumours including osteosarcoma, giant cell tumour of bone, osteoma and osteoid osteoma. MCs, along with other inflammatory cells, are known to accumulate at the margins of soft tissue tumours where they are thought to promote tumour growth. The current findings are consistent with a similar role for mast cells in the primary bone tumours examined. In each of the conditions studied, an additional role for MC may be that of promoting bone lysis. MC are known to contain numerous factors including TNF-alpha and IL-1, which are potent stimulators of osteoclast formation and activity. It is concluded that MCs may contribute to the fibrosis, angiogenesis and increased bone resorption seen in certain metabolic bone diseases. MC activity may also be an important factor contributing to the lysis that occurs in numerous other pathological situations including at the margins of aggressive primary bone tumours and skeletal metastases, leading to the expansion of these lesions

Introduction: Tumor necrosis factor-alpha (TNF-a) has been shown to be a potent stimulator of bone resorption in vitro and in vivo, and has been identified as an important factor in aseptic loosening of total joint replacements. In order to investigate the effects of TNF-a at the bone-cement interface, we developed a rabbit model in which a slow-release pellet containing a known amount of TNF-a was inserted adjacent to a polymethylmethacryate (PMMA) implant in the distal femur. Methods: 25 male New Zealand white rabbits were used in this IACUC-approved study. After routine exposure of the distal femur, a 3 mm drill bit was used to drill through the intercondylar region into the medullary canal of the distal femur. A resorbable pellet containing 0, 420, 4200, 42 000 or 420 000 pg of TNF-a (n=5 animals per dose level) was inserted into the drill hole, immediately followed by a cylindrical PMMA implant (20 mm long). Animals were euthanized 42 days after surgery. The right femora were excised, radiographed, and processed for histology. Ground sections were prepared at the level of the proximal implant. Semi-automated image analysis was used to quantify cortical bone area, porosity and fractional surfaces (quiescent, osteoid and eroded). Data from control and treatment animals were compared with a one-way analysis of variance (ANOVA) using p< 0.05. Results: All of the animals recovered well after surgery. Radiographically, all of the implants appeared to be stable, with no evidence of linear or cystic osteolysis. Local delivery of TNF-a for 6 weeks had no effect on cortical bone area or porosity. However, TNF-a stimulated bone resorption and decreased new bone formation at the endosteal surface (p< 0.05); these effects were not dose-dependent but were seen in all of the TNF-a groups. Discussion: Our data provide direct evidence that local release of TNF-a is capable of inducing endosteal bone resorption in vivo. Additional studies are now needed to determine the effects of other proinflammatory cytokines in this animal model. However, based on these results, it appears that targeted blockade of TNF-a release or activity may provide a rational therapeutic approach to osteolysis and aseptic loosening

Calvaria from six-day-old infant mice were grown on a grid culture in a chemically defined medium under varying oxygen tensions. Quantitative isotope studies demonstrated a linear association between bone resorption and oxygen tension in the physiological range. This result was supported by histological, histochemical and vital staining experiments. The clinical finding of osteoporosis in areas of hyperaemia could therefore be attributed to a rise in oxygen tension causing increased bone resorption

Using a rat model, we created a bone-to-titanium interface and applied phagocytosable high-density polyethylene pArticles between the bone and implant, either initially or when the interface had matured. No fibrous membrane developed and no bone resorption was found. If sliding movements were initiated at the interface after two weeks, there was formation of a fibrous membrane. The additional application of pArticles did not change the thickness of the membrane, and there were only minor qualitative changes. Creation of a membrane by movement followed by cessation of movement and the application of pArticles caused the membrane to persist, whereas in a pArticle-free control group bone-to-metal contact was re-established. Our findings suggest that mechanical stimuli are of primary importance for prosthetic loosening, and that pArticles may modulate the later stages of the loosening process

Introduction: A collar can be defined as any projection from the surface of the proximal third of the femoral stem that interferes with the capacity of the stem to move distally within the cement mantle and provide optimal load distribution along the calcar area. Contraversy exists concerning the usage of a collared or collarless prosthesis and the ability of the collar to perform its effect on the medial femoral neck. The purpose of this study is to compare the proximal femoral bone resorption and aseptic loosening in cases that had poor or good contact between the collar and the proximal medial femoral neck. Materials& Methods: 102 hybrid total hip arthroplasties which were done for severe hip joint disease were analyzed radiographically in the current study. Pre-operative, immediate post operative and the last follow-up anteroposterior and lateral pelvis radiographies were examined. The medial femoral neck-collar contact was considered to be ideal if the medial femoral neck was fully covered by the prosthesis (group A). Contact was deamed to be poor if the medial femoral neck was partially uncovered (group B) or there was cement interposition between the bone and the prosthesis (group C) Cortical femoral bone thickness of the femoral neck was measured on the immediate post-operative and the latest follow-up radiograph as well as the thicker area of bone in Gruen Zone 7. The medial femoral neck height was measured from the superior border of the lesser trochanter. Results: The mean follow up was 4.86 years. The good contact between the collar and the medial femoral neck was achieved for most of the patients. 55 hips were in group A. 30 hips were in group B and 17 hips were in group C at the latest follow-up. The mean loss in the height of the medial femoral neck was 4.21 mm for group A, 4.26mm for group B and 3.05mm for group C. The difference among the groups was not statiscally significant (p=0.545). As we evaluate the relation between the transverse bone loss in the Gruen Zone 7; the loss was 2.49 for group A, 2.26 for group B and 1.58 for group C. The difference among the groups was not statistically significant (p=0.246). Discussion: Unloading of the proximal femur leads resorption of the medial femoral neck and the proximal support of the prosthesis can be lost ultimately leading to aseptic failure due to excessive stresses on the proximal cement and debonding. Although the main purpose of using a collared femoral stem is to transfer load to the medial femoral neck and to prevent bone resorption, in the current study the collar did not prevent calcar resorption even when ideal contact was achieved between the collar and proximal medial femoral neck. Revision rate seems to be unchanged whether the collar had good or bad contact

Introduction. Stress shielding is one of the major concerns of load bearing implants (e.g. hip prostheses). Stiff implants cause stress shielding, which is thought to contribute to bone resorption1. On the contrary, low-stiffness implants generate high interfacial stresses that have been related to pain and interfacial micro-movements². Different attempts have been made to reduce these problems by optimizing either the stem design3 or using functionally graded implants (FGI) where the stem's mechanical properties are optimized4. In this way, new additive manufacturing technologies allow fabricating porous materials with well-controlled mesostructure, which allows tailoring their mechanical properties. In this work, Finite Element (FE) simulations are used to develop an optimization methodology for the shape and material properties of a FGI hip stem. The resorbed bone mass fraction and the stem head displacement are used as objective functions. Methodology. The 2D-geometry of a femur model (Sawbones®) with an implanted Profemur-TL stem (Wright Medical Technology Inc.) was used for FE simulations. The stem geometry was parameterized using a set of 8 variables (Figure 1-a). To optimize the stem's material properties, a grid was generated with equally spaced points for a total of 96 points (Figure 1-b). Purely elastic materials were used for the stem and the bone. Two bone qualities were considered: good (Ecortical=20 GPa, Etrabecular=1.5 GPa) and medium (Ecortical=15 GPa, Etrabecular=1 GPa). Poisson ratio was fixed to v=0.3. Loading corresponded to stair climbing. Hip contact force along with abductors, vastus lateralis and vastus medialis muscles were considered5 for a bodyweight of 847 N. The resorbed bone mass fraction was evaluated from the differences in strain energy densities between the intact bone and the implanted bone2. The displacement of the load point on the femoral head was computed. The optimization problem was formulated as the minimization of the resorbed bone mass fraction and the head displacement. It was solved using a genetic algorithm. Results. For the Profemur-TL design, bone resorption was around 36% and 56% for good and medium bone qualities, respectively (Fig. 2). The corresponding head displacements were 11.75 mm and 21.19 mm. Optimized solutions showed bone resorption from 15% to 26% and from 44% to 65% for good and medium bone qualities, respectively. Corresponding head displacements ranged from 11.85 mm to 12.25 mm and from 16.9 mm to 22.6 mm. Conclusion. The obtained set of solutions constitutes an improvement of the implant performance for this functionally graded implant (FGI) compared to the original implant for both bone qualities. From these simulations, the final solution for the FGI could be chosen based on manufacturing restrictions or another performance indicator

We reviewed at a minimum elapsed time of five years a consecutive series of 143 primary Exeter hip replacements in which matt-surfaced femoral stems had been used. Twenty-five patients had died and six stems and two sockets had been revised before follow-up. The remaining 110 hips were all examined clinically and radiographically. In 15 hips there were radiographic signs of definite loosening of the stem and in eight suspected loosening. The acetabulum was loose in four hips. In another eight hips localised bone resorption was present without signs of loosening. Half the patients with loosening or localised bone resorption had mild pain or no pain at all. The late complication rate with the matt-surfaced Exeter femoral stem is unacceptably high

Introduction: Many claim that an inflammatory reaction to wear debris particles is the main cause for prosthetic loosening. We have rat model in which bone resorption can be induced both by fluid pressure and particles. We compared the bone resorptive potency of particles and fluid pressure. Materials and Methods: The rats received a titanium plate at the proximal tibia. A central plug was inserted. After 5 weeks of osseointegration, the central plug was changed to a piston or a hollow plug with 20mg titanium particles. Commercially pure titanium particles with 90 % of particles lesser than 3,6 microns were used. The pressure piston was subjected to a transcutanous force of 5N. Each episode of pressure comprised 20 pressure cycles at 0.17 Hz, applied twice a day. 60 rats were randomized to 6 groups for particle treatment. One group had particle implantation both at day 1 and 7. Additionally 15 rats were randomized into 3 groups with for pressure treatment. All rats were killed after 5 or 14 days. Bone resorption underneath the piston was evaluated blindedly in hematoxlyin/eosine sections and scored as 0 – 5. Differences between groups were analyzed by Kruskal Wallis and Mann-Whitney U-tests. Results: Many specimens with titanium particles showed no visible resorption at al, and a few showed dramatic osteolysis. After 14 days, the osteolytic effect was significant. Partice refill made no difference. Titanium particles over 10 μm had minor effect. Fluid pressure always caused bone resorption, and significantly more so than particles both after 5 and 14 days. Discussion: There was lesser variability in fluid pressure induced osteolysis, which might be due to a different signalling pathway. Titanium particles have an osteolytic effect in this model, but in spite of the massive amount of particles, the effect was less predictable than with pressure

Aims

The association of auraptene (AUR), a 7-geranyloxycoumarin, on osteoporosis and its potential pathway was predicted by network pharmacology and confirmed in experimental osteoporotic mice.

INTRODUCTION. Bone resorption around hip stems, in particular periprosthetic bone loss, is a common observation post-operatively. A number of factors influence the amount of bone loss over time and the mechanical environment following total hip replacement (THR) is important; conventional long stem prostheses have been shown to transfer loads distally, resulting in bone loss of the proximal femur. More conservative, short stems have been recently introduced to attempt to better replicate the physiological load distribution in the femur. The aim of this study was to evaluate the bone mineral density (BMD) change over time, in a femur implanted with either a short or a long stem. METHODS. Finite element models of two implants, a short (Minihip, Corin, UK) and long (Metafix, Corin, UK) hip stem were used to simulate bone remodeling under a physiological load condition (stair climbing). The magnitudes and directions of the muscle forces and joint reaction force were obtained from Heller et al (2001, 2005). An unimplanted femur was also simulated. A strain-adaptive remodelling theory (Scannel & Prendergast 2009) was utilised to simulate remodelling in the bone after virtual implantation. COMSOL Multiphysics software was used for the analysis. The strain component of the remodelling stimulus was strain energy density per unit mass. This was calculated in the continuum model from the strain energy density, and apparent density. Bone mass was adapted using a site-specific approach in an attempt to return the local remodelling stimulus to the equilibrium stimulus level (calculated from the unimplanted femur). The minimal inhibitory signal proposed by Frost (1964), was included in the model and described by a ‘lazy zone’, where no bone remodelling occurred. The three dimensional geometry of the femur was constructed from computed tomography data of the donor (female, 44 years old, right side). Elemental bone properties were assigned from the Hounsfield Unit values of the CT scans. The elastic modulus of the bone was assumed to be isotropic and was determined using a relationship to the apparent bone density (Frost 1964, Rho 1995). The Poisson's ratio for the bone regions varied between 0.2 and 0.32 depending on the apparent density of the bone (Stulpner 1997). The period of implantation analysed was 2 years. The muscle forces and joint contact loads applied were ramped linearly from zero to full load over a period of two weeks, representing the estimated post operative rest period of a patient. RESULTS AND DISCUSSION. The overall percentage BMD change observed for Gruen zones 1 through to 7, were −14%, +4%, +40%, +12%, +4%, 0%, 12% respectively at 2 years for the Minihip. The corresponding overall percentage BMD change observed for Gruen zones 1 through to 7 for the Metafix were −8%, −2%, 18%, 26%, +12%, −9%, −42% respectively (Figure 1,2). CONCLUSIONS. Considerably more bone resorption occurs in Gruen zone 7 with the long stem. Long stem designs distrupt the mechanical environment more than short stems, and lead to a greater bone mineral reduction over time

Abstract

Aims: To examine the relationship between the Interleukin 6 (IL-6) −174 G> C promoter polymorphism and exercise-induced femoral cortical bone resorption. Methods: The skeletal response to exercise was assessed in 130 male Caucasian army recruits. Five cross-sectional magnetic resonance images of the right femur were obtained before and after a 10 week period of basic physical training, and changes in cross-sectional cortical area calculated. Recruits were genotyped for the −174 G> C IL-6 promoter polymorphism. Results: Genotype frequencies (GG 36%, GC 47%, CC 22 17%) were in Hardy-Weinberg Equilibrium. The mean percentage change in proximal femoral cross sectional cortical area was strongly IL-6 genotype-dependent, with GG homozygotes losing 6.8 ± 3.82% in cortical area, GC gaining +5.5 ± 4.88%, and CC gaining +17.3 ± 9.46% (p=0.007 for linear trend). These changes persisted throughout the right femur and were significant in the femur as a whole (p=0.03). Conclusion: This study demonstrates a linear relationship between a functional polymorphism in the IL-6 gene and femoral cortical remodelling during strenuous physical exercise. Previous studies have suggested an important role for IL-6 in the regulation of bone mass in postmenopausal women, and in the invasion of bone by metastatic tumour deposits. These data extend these observations to the regulation of bone mass in healthy males, supporting a fundamental role for IL-6 in the regulation of bone mass and bone remodelling in humans

Wear particles commonly used for experiments may carry adherent endotoxin on their surfaces, which may be responsible for the observed effects. In this study, we attached titanium plates to the tibiae of 20 rats. After osseointegration, endotoxin-contaminated or uncontaminated high-density-polyethylene (HDPE) particles were applied. Contaminated specimens showed a dramatic resorption of bone after seven days but new bone filled the site again at 21 days. Uncontaminated specimens showed no resorption. In 18 rats we implanted intramuscularly discs of ultra-high-molecular-weight polyethylene (UHMWPE) with baseline or excess contamination of endotoxin. Excess endotoxin disappeared within 24 hours and the amount of endotoxin remained at baseline level (contamination from production). Uncontaminated titanium discs did not adsorb endotoxin in vivo. The endotoxin was measured by analytical chemistry. Locally-applied endotoxin stimulated bone resorption similarly to that in experiments with wear particles. Endotoxin on the surface of implants and particles appeared to be inactivated in situ. A clean implant surface did not adsorb endotoxin. Our results suggest that endotoxin adhering to orthopaedic implants is not a major cause for concern

Inadequate bone stock is often found in revision surgery of femoral components of total knee replacements. Our aim was to test the hypothesis that these remodelling patterns can be explained by stress shielding, and that prosthetic bonding characteristics affect maintenance of bone mass. We made a three-dimensional finite-element model of an average male femur with a cemented femoral knee component. This model was integrated with iterative remodelling procedures. Two extreme prosthetic bonding conditions were analysed and gradual changes in bone density were calculated. The long-term bone loss under the femoral knee component resembled clinical findings which confirms the hypothesis that stress shielding can cause distal femoral bone loss. Our study predicts, contrary to clinical findings, that an equilibrium situation is not reached after two years, but that bone resorption may continue. This hidden bone loss may be so drastic that large reconstructions are needed at the time of revision

Matrix metalloproteinases (MMPs) may have a role in the process of aseptic loosening. Doxycycline has been shown to inhibit MMPs. Our aim was to investigate the potential pharmacological effect of doxycycline on aseptic loosening. We used radiolabelled mouse calvariae cultured with human interface membrane cells from aseptically loosened hips. Bone resorption was confirmed in this model. The effect of doxycycline was assessed by culturing dead radiolabelled bone discs with cells from the interface membrane with doxycycline. The control group consisted of the same culture system without doxycycline. Supernatant . 45. calcium and the total . 45. calcium remaining in the bone discs at the completion of the culture were used to measure osteolysis. We found that doxycycline can inhibit osteolysis at the interface membrane of aseptically loosened hips. This may have therapeutic implications for the treatment of patients with aseptic loosening of total joint replacements

Introduction: In a rat model, fluid pressure causes more bone resorption than particles. Does pressure also cause more inflammation?. Materials and Methods: Rats received a titanium plate at the proximal tibia. A central plug was inserted. After 5 weeks of osseointegration, the central plug was changed to either a piston or a hollow plug with titanium particles. Commercially pure titanium particles with 90% of particles lesser than 3,6 microns were used. The pressure piston was subjected to a transcutanous force of 8N. Each episode of pressure comprised 20 pressure cycles at 0.17 Hz, applied twice a day. 39 rats were randomized to 3 groups: Titanium particles (n=13), fluid pressure (n=13) and controls with neither particles nor fluid pressure (n=13). The rats were killed after 3 days. 6 rats in each group were used for histology and the others for gene expression. Extraction of total RNA was performed using the TRIspin method. Primers for cat K, RANK, RANKL, OPG IL-1, IL-b, TNF-a, iNOS and COX-2 were used. Each sample was normalized to 18S rRNA. Histology was evaluated qualitatively. Differences between the groups were analyzed by Kruskal Wallis and Mann-Whitney U-test. Results: Both particles and fluid pressure increased the expression of osteoclastic genes. Particles induced an elevated expression of IL-6 and RANK compared to both controls and fluid pressure. There was a tendency that particles induced more expression of other inflammatory genes compared to fluid pressure. Histology: The controls showed only few osteoclasts at the bone surface. The particle group showed osteoclasts at the surface towards the particles. In contrast, the pressure group showed resorption cavities spread out inside the bone. Discussion: Although there was more resorption in the pressure group, there was a lesser inflammatory response. This suggests that pressure-induced resorption is mediated via different pathways

A common location for radius fracture is the proximal radial head. With the arm in neutral position, the fracture usually happens in the anterolateral quadrant (Lacheta et al., 2019).

If traditional surgeries are not enough to induce bone stabilization and vascularization, or the fracture can be defined grade III or grade IV (Mason classification), a radial head prosthesis can be the optimal compromise between bone saving and recovering the “terrible triad”.

A commercially available design of radial head prosthesis such as Antea (Adler Ortho, Milan, Italy) is characterized by flexibility in selecting the best matching size for patients and induced osteointegration thanks to the Ti-Por^® radial stem realized by 3D printing with laser technique (Figure 1). As demonstrated, Ti-Por^® push-out resistance increased 45% between 8 −12 weeks after implantation, hence confirming the ideal bone-osteointegration. Additional features of Antea are: bipolarity, modularity, TiN coating, radiolucency, hypoallergenic, 10° self-aligning.

The osteointegration is of paramount importance for radius, in fact the literature is unfortunately reporting several clinical cases for which the fracture of the prosthesis happened after bone-resorption. Even if related to an uncommon activity, the combination of mechanical resistance provided by the prosthesis and the stabilization due to the osteointegration should cover also accidental movements.

Based upon Lacheta et al. (2019), after axial compression-load until radii failure, all native specimens survived a compression-load of 500N, while the failure happened for a mean compression force of 2560N.

The aim of this research study was to test the mechanical resistance of a radial head prosthesis obtained by 3D printing. In detail, a finite element analysis (FEA) was used to understand the mechanical resistance of the core of the prosthesis and the potential bone fracture induced in the radius with simulated bone- resorption (Figure 2a). The critical level was estimated at the height for which the thickness of the core is the minimum (Figure 2b).

Considered boundary conditions:

- Full-length prosthesis plus radius out of the cement block equal to 60mm (Figure 2a);

Figure 3 shows the results in terms of maximum stress on the core of the prosthesis and the risk of fracture (Schileo et al., 2008).

According to the obtained results, the radial head prosthesis shows promising mechanical resistance despite of the simulated bone-resorption for all applied loads except for 2560N. The estimated mechanical limit for the material in use is 200MPa. The risk of fracture is in agreement with the experimental findings (Lacheta et al. (2019)), in fact bone starts to fail for the minimum reported failure load, but only for osteoporotic conditions.

The presented FEA aimed at investigating the behavior of a femoral head prostheses made by 3D printing with simulated bone-resorption. The prosthesis shows to be a skilled solution even during accidental loads.

For any figures or tables, please contact the authors directly.

Aims

It has been hypothesized that proximal radial neck resorption (PRNR) following press-fit radial head arthroplasty (RHA) is due to stress-shielding. We compared two different press-fit stems by means of radiographs to investigate whether the shape and size of the stems are correlated with the degree of PRNR.

Similar to the radiological findings in rapidly destructive arthrosis of the hip joint (RDA), subchondral insufficiency fracture of the femoral head (SIF) can result in progressive femoral head collapse of unknown etiology. We thus examined the osteoclast activity in hip joint fluid in SIF with progressive collapse in comparison to that in RDA. Twenty-nine hip joint fluid samples were obtained intraoperatively with whole femoral heads from 12 SIF patients and 17 RDA patients. SIF cases were classified into subgroups based on the presence of ≥2mm collapse on preoperative radiographs: SIF with progressive collapse (n=5) and SIF without progressive collapse (n=7). The levels of tartrate-resistant acid phosphatase (TRACP)-5b, interleukin-8, vascular endothelial growth factor (VEGF), and matrix metalloproteinase (MMP)-9 were measured. Numbers of multinuclear giant cells at the subchondral region were assessed histopathologically using mid-coronal slices of each femoral head specimen. Median levels of all markers and median numbers of multinuclear giant cells in SIF with progressive collapse were significantly higher than those in SIF without progressive collapse, while there were no significant differences in SIF with progressive collapse versus RDA. Regression analysis showed that the number of multinuclear giant cells correlated positively with the level of TRACP-5b in joint fluid. This study suggests an association of increased osteoclast activity with the existing condition of progressive collapse in SIF, which was quite similar to the findings in RDA. Therefore, high activation of osteoclast cell may reflect the condition of progressive collapse in SIF as well as RDA.

Aims

Surgeons and most engineers believe that bone compaction improves implant primary stability without causing undue damage to the bone itself. In this study, we developed a murine distal femoral implant model and tested this dogma.

The radiographs of sixty-four patients with seventy humeral head replacements were reviewed for signs of stress shielding. Forty-nine were implanted for rheumatoid arthritis, twenty-one for osteoarthritis. The radiographic follow-up averaged 5. 3 years. Measurements of cortex thickness were performed in four regions along the stem of the implant and the differences between the post-operative radiograph and radiograph at follow-up were calculated. The size of the stem in relation to the diameter of the humerus was calculated using validated measures, resulting in the relative stem size.

A reduction of 1.6 millimeters or more was considered to be a significant reduction, because this lay outside of the calculated 95% normal range for the group as a whole. In six patients (9%) a significant reduction, in cortical thickness was observed in the proximal lateral region of the humeral stem. Five of these had rheumatoid arthritis and one osteoarthritis. In the stress shielding group the relative stem size was found to be significantly higher (p=0. 013) than in the non-stress shielding group (0. 58 versus 0. 48). Osteoporosis, especially present in rheumatoid arthritis, could well be a risk factor. It was concluded that stress shielding is a long-term complication of shoulder arthroplasty and that the relative stem size is an important factor in its genesis. These resorptive processes may lead to a higher risk of failure of the implant and gives an increased risk for mid-stem fractures, due to cantilever loading. It is also desirable to preserve the proximal bone stock, considering the difficulties that arise when, for whatever reason, revision of the implant is necessary.

Osteoclast Associated Receptor (OSCAR) is a novel member of leucocyte receptor complex (LCR)-encoded family expressed by pre-osteoclasts and mature osteoclasts (OC). Blocking of OSCAR binding to its putative ligand has been shown to inhibit osteoclast formation. To date there is no data available regarding the expression of OSCAR in tissues associated with osteolysis and the objective of this study is to determine if OSCAR is expressed adjacent to focal bone osteolysis near failed implants. A total of 22 samples (10 Peri-implant tissue and 12 OA) were studied. OSCAR antibodies were a gift from R& D Systems Inc. (Minneapolis, MN, USA). The tissues were analysed semi-qualitatively using semi-quantitative scoring (SQA) independently by two observers. Non-parametric Mann Whitney-U test was used to test statistical significance. Dual labelling for OSCAR and CD68 expression was also carried out. Strong expression of OSCAR was seen in the majority of multinucleated cells in peri-implant tissues while OA tissues showed very low levels of OSCAR expression. Dual labelling studies revealed that the cells expressing OSCAR also expressed CD68. There was a significant difference in the expression of OSCAR between peri-implant tissue and OA synovial tissue (p< 0.003). This study shows that OSCAR is expressed at high levels by the numerous CD68 multinucleated cells present is these tissues in peri-implant tissues. These findings and recent reports on the role OSCAR may play in OC formation indicate that OSCAR could be an important mediator of peri-implant osteolysis

Peri-prosthetic osteolysis and subsequent aseptic loosening is the most common reason for revising total hip replacements. Wear particles originating from the prosthetic components interact with multiple cell types in the peri-prosthetic region resulting in an inflammatory process that ultimately leads to peri-prosthetic bone loss. These cells include macrophages, osteoclasts, osteoblasts and fibroblasts. The majority of research in peri-prosthetic osteolysis has concentrated on the role played by osteoclasts and macrophages. The purpose of this review is to assess the role of the osteoblast in peri-prosthetic osteolysis.

In peri-prosthetic osteolysis, wear particles may affect osteoblasts and contribute to the osteolytic process by two mechanisms. First, particles and metallic ions have been shown to inhibit the osteoblast in terms of its ability to secrete mineralised bone matrix, by reducing calcium deposition, alkaline phosphatase activity and its ability to proliferate. Secondly, particles and metallic ions have been shown to stimulate osteoblasts to produce pro inflammatory mediators in vitro. In vivo, these mediators have the potential to attract pro-inflammatory cells to the peri-prosthetic area and stimulate osteoclasts to absorb bone. Further research is needed to fully define the role of the osteoblast in peri-prosthetic osteolysis and to explore its potential role as a therapeutic target in this condition.

Cite this article: Bone Joint J 2013;95-B:1021–5.

Aims

The primary aim of this study was to compare the wear properties of vitamin E-diffused, highly crosslinked polyethylene (VEPE) and one formulation of moderately crosslinked and mechanically annealed ultra-high molecular weight polyethylene (ModXLPE) in patients five years after primary total hip arthroplasty (THA). The secondary aim was to assess the clinical results of patients treated with VEPE by evaluating patient-reported outcome measures (PROMs), radiological evidence of fixation, and the incidence of mechanical failure.

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.

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. Methods. Periprosthetic femoral trabecular bone specimens were obtained from patients suffering from chronic PJI of the hip and knee (n = 20). Microbiological analysis was performed on preoperative joint aspirates and tissue specimens obtained during revision surgery. Microstructural and cellular bone parameters were analyzed in bone specimens by histomorphometry on undecalcified sections complemented by tartrate-resistant acid phosphatase immunohistochemistry. Data were compared with control specimens obtained during primary arthroplasty (n = 20) and aseptic revision (n = 20). Results. PJI specimens exhibited a higher bone volume, thickened trabeculae, and increased osteoid parameters compared to both control groups, suggesting an accelerated bone turnover with sclerotic microstructure. On the cellular level, osteoblast and osteoclast parameters were markedly increased in the PJI cohort. Furthermore, a positive association between serum (CRP) but not synovial (white blood cell (WBC) count) inflammatory markers and osteoclast indices could be detected. Comparison between different pathogens revealed increased osteoclastic bone resorption parameters without a concomitant increase in osteoblasts in bone specimens from patients with Staphylococcus aureus infection, compared to those with detection of Staphylococcus epidermidis and Cutibacterium spp. Conclusion. This study provides insights into the local bone metabolism in chronic PJI, demonstrating osteosclerosis with high bone turnover. The fact that Staphylococcus aureus was associated with distinctly increased osteoclast indices strongly suggests early surgical treatment to prevent periprosthetic bone alterations. Cite this article: Bone Joint Res 2023;12(10):644–653

Aims. The aim of this study was to analyze how proximal radial neck resorption (PRNR) starts and progresses radiologically in two types of press-fit radial head arthroplasties (RHAs), and to investigate its clinical relevance. Methods. A total of 97 patients with RHA were analyzed: 56 received a bipolar RHA (Group 1) while 41 received an anatomical implant (Group 2). Radiographs were performed postoperatively and after three, six, nine, and 12 weeks, six, nine, 12, 18, and 24 months, and annually thereafter. PRNR was measured in all radiographs in the four radial neck quadrants. The Mayo Elbow Performance Score (MEPS), the abbreviated version of the Disabilities of the Arm, Shoulder, and Hand questionnaire (QuickDASH), and the patient-assessed American Shoulder and Elbow Surgeons score - Elbow (pASES-E) were used for the clinical assessment. Radiological signs of implant loosening were investigated. Results. The mean follow-up was six years (2 to 14). PRNR started after a mean of 7.5 weeks (SD 2.1) and progressed significantly during the first two years, by the end of which the bone resorption stabilized. PRNR was detected in 81% (n = 45) of patients in Group 1 and 88% (n = 36) in Group 2. The final mean PRNR was 3.0 mm (SD 2.3) in Group 1 and 3.7 mm (SD 2.5) in Group 2. The mean MEPS, QuickDASH, and pASES-E were 95.9 (SD 11.5), 4.4 (SD 9.2), and 94.8 (SD 10.9) in Group 1 and 92.2 (SD 16.2), 9.9 (SD 21.5), and 90.8 (SD 15) in Group 2, respectively. No significant differences were observed between groups in the clinical and radiological outcomes. No correlations were found between PRNR and the clinical results. Conclusion. PRNR after press-fit RHA is a common radiological finding that develops in the first 24 months before stabilizing definitively. PRNR does not affect the clinical results or implant survival in the mid term. Cite this article: Bone Joint J 2023;105-B(8):905–911

Abstract. OBJECTIVE. Knee varus malalignment increases medial knee compartment loading and is associated with knee osteoarthritis (OA) progression and severity. 1. Altered biomechanical loading and dysregulation of joint tissue biology drive OA progression, but mechanistic links between these factors are lacking. Subchondral bone structural changes are biomechanically driven, involve bone resorption, immune cell influx, angiogenesis, and sensory nerve invasion, and contribute to joint destruction and pain. 2. We have investigated mechanisms underlying this involving RANKL and alkaline phosphatase (ALP), which reflect bone resorption and mineralisation respectively. 3. and the axonal guidance factor Sema3A. Sema3A is osteotropic, expressed by mechanically sensitive osteocytes, and an inhibitor of sensory nerve, blood vessel and immune cell invasion. 4. Sema3A is also differentially expressed in human OA bone. 5. HYPOTHESIS: Medial knee compartment overloading in varus knee malalignment patients causes dysregulation of bone derived Sema3A signalling directly linking joint biomechanics to pathology and pain. METHODS. Synovial fluid obtained from 30 subjects with medial knee OA (KL grade II-IV) undergoing high tibial osteotomy surgery (HTO) was analysed by mesoscale discovery and ELISA analysis for inflammatory, neural and bone turnover markers. 11 of these patients had been previously analysed in a published patient-specific musculoskeletal model. 6. of gait estimating joint contact location, pressure, forces, and medial-lateral condyle load distribution in a published data set included in analyses. Data analysis was performed using Pearson's correlation matrices and principal component analyses. Principal Components (PCs) with eigenvalues greater than 1 were analysed. RESULTS. PC1 (32.94% of variation) and PC2 (25.79% of variation) from PCA analysis and correlation matrices separated patients according to correlated clusters of established inflammatory markers of OA pain and progression (IL6/IL8, r=0.754, p<0.001) and anti-inflammatory mediators (IL4/IL10, r=0.469, p=0.005). Bone turnover marker ALP was positively associated with KL grade (r=0.815, p=0.002) and negatively associated with IL10 (r=−0.402, p=0.018) and first peak knee loading pressures (r=−0.688, p=0.019). RANKL was positively associated with IL4 (r=0.489, p=0.003). Synovial fluid Sema3A concentrations showed separate clustering from all OA progression markers and was inversely correlated with TNF-α (r=−0.423, p=0.022) in HTO patients. Sema3A was significantly inversely correlated with total predicted force in the medial joint compartment (r=−0.621, p=0.041), mean (r=−0.63, p=0.038) and maximum (r=−0.613, p=0.045) calculated medial compartment joint pressures during the first phase and mean (r=−0.618, p=0.043) and maximum (r=−0.641, p=0.034) medial compartment joint pressures during midstance outputs of patient-specific musculoskeletal model. CONCLUSIONS. This study shows joint inflammatory status and mechanical overloading influence subchondral bone-remodelling. Synovial Sema3A concentrations are inversely correlated to patient-specific musculoskeletal model estimations of pathological medial overloading. This study reveals Sema3A as a biological mediator with capacity to induce OA pain and disease progression that is directly regulated by gait mechanical loading. 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. Bone turnover markers (BTMs) follow distinct trends after fractures and limited evidence suggests differential levels in BTMs in patients with delayed healing. The effect of vitamin D, and other factors that influence BTMs and fracture healing, is important to elucidate the use of BTMs as surrogates of fracture healing. We sought to determine whether BTMs can be used as early markers of delayed fracture healing, and the effect of vitamin D on BTM response after fracture. Methods. A total of 102 participants aged 18 to 50 years (median 28 years (interquartile range 23 to 35)), receiving an intramedullary nail for a tibial or femoral shaft fracture, were enrolled in a randomized controlled trial comparing vitamin D. 3. supplementation to placebo. Serum C-terminal telopeptide of type I collagen (CTX; bone resorption marker) and N-terminal propeptide of type I procollagen (P1NP; bone formation marker) were measured at baseline, six weeks, and 12 weeks post-injury. Clinical and radiological fracture healing was assessed at three months. Results. CTX and P1NP concentrations peaked at six weeks in all groups. Elevated six-week CTX and P1NP were associated with radiological healing at 12 weeks post-injury (odds ratio (OR) 10.5; 95% confidence interval 2.71 to 53.5, p = 0.002). We found no association between CTX or P1NP and functional healing. Baseline serum 25(OH)D showed a weak inverse relationship with P1NP (p = 0.036) and CTX (p = 0.221) at 12 weeks, but we observed no association between vitamin D supplementation and either BTM. Conclusion. Given the association between six-week BTM concentrations and three-month radiological fracture healing, CTX and P1NP appear to be potential surrogate markers of fracture healing. Cite this article: Bone Joint Res 2022;11(4):239–250

Introduction and Objective. In recent years, along with the extending longevity of patients and the increase in their functional demands, the number of annually performed RSA and the incidence of complications are also increasing. When a complication occurs, the patient often needs multiple surgeries to restore the function of the upper limb. Revision implants are directly responsible for the critical reduction of the bone stock, especially in the shoulder. The purpose of this paper is to report the use of allograft bone to restore the bone stock of the glenoid in the treatment of an aseptic glenoid component loosening after a reverse shoulder arthroplasty (RSA). Materials and Methods. An 86-years-old man came to our attention for aseptic glenoid component loosening after RSA. Plain radiographs showed a complete dislocation of the glenoid component with 2 broken screws in the neck of glenoid. CT scans confirmed the severe reduction of the glenoid bone stock and critical bone resorption and were used for the preoperative planning. To our opinion, given the critical bone defect, the only viable option was revision surgery with restoration of bone stock. We planned to use a bone graft harvested from distal bone bank femur as component augmentation. During the revision procedure the baseplate with a long central peg was implanted “on table” on the allograft and an appropriate osteotomy was made to customize the allograft on the glenoid defect according to the CT-based preoperative planning. The Bio-component was implanted with stable screws fixation on residual scapula. We decided not to replace the humeral component since it was stable and showed no signs of mobilization. Results. The new bio-implant was stable, and the patient gained a complete functional recovery of the shoulder. The scheduled radiological assessments up to 12 months showed no signs of bone resorption or mobilization of the glenoid component. Conclusions. The use of bone allograft in revision surgery after a RSA is a versatile and effective technique to treat severe glenoid bone loss and to improve the global stability of the implant. Furthermore, it represents a viable alternative to autologous graft since it requires shorter operative times and reduces graft site complications. There are very few data available regarding the use of allografts and, although the first studies are encouraging, further investigation is needed to determine the biological capabilities of the transplant and its validity in complex revisions after RSA

During the last decades, several research groups have used bisphosphonates for local application to counteract secondary bone resorption after bone grafting, to improve implant fixation or to control bone resorption caused by bone morphogenetic proteins (BMPs). We focused on zoledronate (a bisphosphonate) due to its greater antiresorptive potential over other bisphosphonates. Recently, it has become obvious that the carrier is of importance to modulate the concentration and elution profile of the zoledronic acid locally. Incorporating one fifth of the recommended systemic dose of zoledronate with different apatite matrices and types of bone defects has been shown to enhance bone regeneration significantly in vivo. We expect the local delivery of zoledronate to overcome the limitations and side effects associated with systemic usage; however, we need to know more about the bioavailability and the biological effects. The local use of BMP-2 and zoledronate as a combination has a proven additional effect on bone regeneration. This review focuses primarily on the local use of zoledronate alone, or in combination with bone anabolic factors, in various preclinical models mimicking different orthopaedic conditions. Cite this article: I. Qayoom, D. B. Raina, A. Širka, Š. Tarasevičius, M. Tägil, A. Kumar, L. Lidgren. Anabolic and antiresorptive actions of locally delivered bisphosphonates for bone repair: A review. Bone Joint Res 2018;7:548–560. DOI: 10.1302/2046-3758.710.BJR-2018-0015.R2

Aims. LY3023414 is a novel oral phosphatidylinositol 3-kinase (PI3K)/mammalian target of rapamycin (mTOR) dual inhibitor designed for advanced cancers, for which a phase II clinical study was completed in March 2020; however, little is known about its effect on bone modelling/remodelling. In this study, we aimed to explore the function of LY3023414 in bone modelling/remodelling. Methods. The function of LY3023414 was explored in the context of osteogenesis (bone formation by osteoblasts) and osteoclastogenesis (osteoclast formation and bone resorption). Murine preosteoblast MC3T3-E1 cell line and murine bone marrow-derived macrophage cells (BMMs) were subjected to different treatments. An MTS cell proliferation assay was used to examine the cytotoxicity. Thereafter, different induction conditions were applied, such as MCSF and RANKL for osteoclastogenesis and osteogenic media for osteogenesis. Specific staining, a bone resorption assay, and quantitative real-time polymerase chain reaction (qRT-PCR) were subsequently used to evaluate the effect of LY3023414. Moreover, small interfering RNA (siRNA) was applied to knockdown Akt1 or Akt2 for further validation. Lastly, western blot was used to examine the exact mechanism of action. Results. LY3023414 attenuated PI3K/protein kinase B (Akt)/GSK3-dependent activation of β-catenin and nuclear factor-activated T cell 1 (NFATc1) during osteogenesis and osteoclastogenesis, respectively. LY3023414 mainly inhibited osteoclast formation instead of mature osteoclast function. Moreover, it suppressed osteogenesis both in the early stage of differentiation and late stage of calcification. Similarly, gene knockdown of Akt isoforms by siRNA downregulated osteogenic and osteoclastogenic processes, indicating that Akt1 and Akt2 acted synergistically. Conclusion. LY3023414 can suppress osteogenesis and osteoclastogenesis through inhibition of the PI3K/Akt/GSK3 signalling pathway, which highlights the potential benefits and side effects of LY3023414 for future clinical applications. Cite this article: Bone Joint Res 2021;10(4):237–249

Hip and knee arthroplasty (HKA) are two of the most successful orthopaedic procedures. However, one major complication necessitating revision surgery is osteolysis causing aseptic loosening of the prosthesis. JAK-STAT has been demonstrated to influence bone metabolism and can be regulated by microRNA (miRNA). Adult patients with osteolysis or aseptic loosening undergoing revision HKA were recruited. Age and gender matched patients undergoing primary hip or knee arthroplasty were our controls. Samples of bone, tissue and blood were collected and RNA isolation was performed. The best quality samples were used for RNA-sequencing. Data analysis was performed using RStudio and Galaxy to identify differentially expressed genes. Western blotting of IL6 was used to confirm protein expression. Five circulating miRNA were identified which had 10 differentially expressed genes in bone and 11 differentially expressed genes in tissue related to the JAK-STAT pathway. IL6 in bone and EpoR in bone were highly significant and IL6 in tissue, MPL in bone, SOCS3 in tissue, JAK3 in bone and SPRED1 in bone were borderline significant. Western blot results demonstrated up-expression of IL6 in bone tissue of revision patients. Periprosthetic osteolysis and aseptic loosening can be attributed to miRNA regulation of the JAK-STAT pathway in osteoblasts and osteoclasts, leading to increased bone resorption. These findings can be used for further experiments to determine utility in the clinical setting for identifying diagnostic markers or therapeutic targets

Paget's disease of bone (PDB) is characterised by increased bone resorption and development of an erratic bone structure that is highly fragile and susceptible to fracture. In addition, altered joint biomechanics lead to arthritis, more often in the hip and pelvis, resulting in disability and a Total hip Arthroplasty (THA) may be required. THA in PDB is associated with more complications compared to normal population. There is no consensus on the type of arthroplasty that performs better in people with PDB. To our knowledge, there is no meta-analysis in literature on this rare problem. We undertook a systematic review and meta-analysis to compare the effectiveness of cemented versus cementless THA in patients with PDB. PRISMA guidelines were followed. Search strings were generated based on Boolean operators for identification of the reference articles. 31 studies were included overall. Revision rate was lower in the cementless group compared to the cemented group (chi square=4.36, p=0.04), aseptic loosening was lesser in the cementless group compared to the cemented group (chi square=4.13, p=0.04). The type of the arthroplasty did not affect the infection rate (chi square=2.51, p=0.11), pre and post op Harris Hip Score showed statistically significant difference, but there was no difference between types of arthroplasty. We conclude that THA with uncemented components is better and provided lower revision and aseptic loosening when compared to cemented groups in patients with PDB

Bone regeneration is pivotal for the healing of fractures. In case this process is disturbed a non-union can occur. This can be induced by environmental factors such as smoking, overloading etc. Co-morbidities such as diabetes, osteoporosis etc. may be more intrinsic factors besides other disturbances in the process. Those pathways negatively influence the bone regeneration process. Several intrinsic signal transduction pathways (WNT, BMP etc.) can be affected. Furthermore, on the transcriptional level, important mRNA expression can be obstructed by deregulated miRNA levels. For instance, several miRNAs have been shown to be upregulated during osteoporotic fractures. They are detrimental for osteogenesis as they block bone formation and accelerate bone resorption. Modulating those miRNAs may revert the physiological homeostasis. Indeed, physiological fracture healing has a typical miRNA signature. Besides using molecular pathways for possible treatment of non-union fractures, providing osteogenic cells is another solution. In 5 clinical cases with non-union fractures with defects larger than 10 cm, successful administration of a 3D printed PCL-TCP scaffold with autologous bone marrow aspirate concentrate and a modulator of the pathogenetic pathway has been achieved. All patients recovered well and showed a complete union of their fractures within one year after start of the regenerative treatment. Thus, non-union fractures are a diverse entity. Nevertheless, there seem to be common pathogenetic disturbances. Those can be counteracted at several levels from molecular to cell. Compositions of those may be the best option for future therapies. They can also be used in a more personalized fashion in case more specific measurements such as miRNA signature and stem cell activity are applied

Osteoporosis is a progressive, chronic disease of bone metabolism, characterized by decreased bone mass and mineral density, predisposing individuals to an increased risk of fractures. The use of animal models, which is the gold standard for the screening of anti-osteoporosis drugs, raises numerous ethical concerns and is highly debated because the composition and structure of animal bones is very different from human bones. In addition, there is currently a poor translation of pre-clinical efficacy in animal models to human trials, meaning that there is a need for an alternative method of screening and evaluating new therapeutics for metabolic bone disorders, in vitro. The aim of this project is to develop a 3D Bone-On-A-Chip that summarizes the spatial orientation and mutual influences of the key cellular components of bone tissue, in a citrate and hydroxyapatite-enriched 3D matrix, acting as a 3D model of osteoporosis. To this purpose, a polydimethylsiloxane microfluidic device was developed by CAD modelling, stereolithography and replica molding. The device is composed by two layers: (i) a bottom layer for a 3D culture of osteocytes embedded in an osteomimetic collagen-enriched matrigel matrix with citrate-doped hydroxyapatite nanocrystals, and (ii) a upper layer for a 2D perfused co-culture of osteoblasts and osteoclasts seeded on a microporous PET membrane. Cell vitality was evaluated via live/dead assay. Bone deposition and bone resorption was analysed respectively with ALP, Alizarin RED and TRACP staining. Osteocytes dendrite expression was evaluated via immunofluorescence. Subsequently, the model was validated as drug screening platform inducing osteocytes apoptosis and administrating standard anti-osteoporotic drugs. This device has the potential to substitute or minimize animal models in pre-clinical studies of osteoporosis, contributing to pave the way for a more precise and punctual personalized treatment

Anatomically, bone consists of building blocks called osteons, which in turn comprise a central canal that contains nerves and blood vessels. This indicates that bone is a highly innervated and vascularized tissue. The function of vascularization in bone (development) is well-established: providing oxygen and nutrients that are necessary for the formation, maintenance, and healing. As a result, in the field of bone tissue engineering many research efforts take vascularization into account, focusing on engineering vascularized bone. In contrast, while bone anatomy indicates that the role of innervation in bone is equally important, the role of innervation in bone tissue engineering has often been disregarded. For many years, the role of innervation in bone was mostly clear in physiology, where innervation of a skeleton is responsible for sensing pain and other sensory stimuli. Unraveling its role on a cellular level is far more complex, yet more recent research efforts have unveiled that innervation has an influence on osteoblast and osteoclast activity. Such innervation activities have an important role in the regulation of bone homeostasis, stimulating bone formation and inhibiting resorption. Furthermore, due to their anatomical proximity, skeletal nerves and blood vessels interact and influence each other, which is also demonstrated by pathways cross-over and joint responses to stimuli. Besides those closely connected sytems, the immune system plays also a pivotal role in bone regeneration. Certain cytokines are important to attract osteogenic cells and (partially) inhibit bone resorption. Several leukocytes also play a role in the bone regeneration process. Overall, bone interacts with several systems. Aberrations in those systems affect the bone and are important to understand in the context of bone regeneration. This crosstalk has become more evident and is taken more into consideration. This leads to more complex tissue regeneration, but may recapitulate better physiological situations

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

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

Although bone morphogenetic protein 2 (BMP-2) has been FDA-approved for spinal fusion for decades, its disadvantages of promoting osteoclast-based bone resorption and suboptimal carrier (absorbable collagen sponge) leading to premature release of the protein limit its clinical applications. Our recent study showed an excellent effect on bone regeneration when BMP-2 and zoledronic acid (ZA) were co-delivered based on a calcium sulphate/hydroxyapatite (CaS/HA) scaffold in a rat critical-size femoral defect model. Therefore, the aim of this study was to evaluate whether local application of BMP-2 and ZA released from a CaS/HA scaffold is favorable for spinal fusion. We hypothesized that CaS/HA mediated controlled co-delivery of rhBMP-2 and ZA could show an improved effect in spinal fusion over BMP-2 alone. 120, 8-week-old male Wistar rats (protocol no. 25-5131/474/38) were randomly divided into six groups in this study (CaS/HA, CaS/HA + BMP-2, CaS/HA + systemic ZA, CaS/HA + local ZA, CaS/HA + BMP-2 + systemic ZA, CaS/HA + BMP-2 + local ZA). A posterolateral spinal fusion at L4 to L5 was performed bilaterally by implanting group-dependent scaffolds. At 3 weeks and 6 weeks, 10 animals per group were euthanized for µCT, histological staining, or mechanical testing. µCT and histological results showed that the CaS/HA + BMP-2 + local ZA group significantly promoted bone regeneration than other treated groups. Biomechanical testing showed breaking force in CaS/HA + BMP + local ZA group was significantly higher than other groups at 6 weeks. In conclusion, the CaS/HA-based biomaterial functionalized with bioactive molecules rhBMP-2 and ZA enhanced bone formation and concomitant spinal fusion outcome. Acknowledgements: Many thanks to Ulrike Heide, Anna-Maria Placht (assistance with surgeries) as well as Suzanne Manthey & Annett Wenke (histology)

Patients with bone and muscle weakness from disuse have higher risk of fracture and worse post-injury mortality rates. The goal of this current study was to better inform post-fracture rehabilitation strategies by investigating if physical remobilization following disuse by hindlimb unloading improves osteochondral callus formation compared to continued disuse by hindlimb suspension (HLS). We hypothesized that continued HLS would impair callus bone and cartilage formation and that physical rehabilitation after HLS would increase callus properties. All animal procedures were approved by the VCU IACUC. Skeletally mature, male and female C57BL/6J mice (18 weeks) underwent HLS for 3 weeks. Mice then had their right femur fractured by open surgical dissection (stabilized with 24-gauge pin). Mice were then either randomly assigned to continued HLS or allow normal physical weight-bearing remobilization (HLS + R). Mice allowed normal cage activity throughout the experiment served as controls (GC). All mice were sacrificed 14-days following fracture with 4-8 mice (male and female) per treatment. Data analyzed by respective ANOVA with Tukey post-hoc (*p< 0.05; # p < 0.10). Male and female mice showed conserved and significant decreases in hindlimb callus bone formation from continued HLS versus HLS + R. Combining treatment groups regardless of mouse sex, histological analyses using staining on these same calluses demonstrated that HLS resulted in trends toward decreased cartilage cross-sectional area and increased osteoclast density in woven bone versus physically rehabilitated mice. In support of our hypothesis, physical remobilization increases callus bone formation following fracture compared to continued disuse potentially due to increased endochondral ossification and decreased bone resorption. In all, partial weight-bearing exercise immediately following fracture may improve callus healing compared to delayed rehabilitation regimens that are frequently used

Bone remodelling is mediated through the synchronism of bone resorption (catabolism) by osteoclasts and bone formation (anabolism) by osteoblasts. Imbalances in the bone remodelling cycle represent an underling cause of metabolic bone diseases such as osteoporosis, where bone resorption exceeds formation (1). Current therapeutic strategies to repair osteoporotic bone fractures focus solely in targeting anabolism or supressing catabolism (2). However, these therapeutics do not reverse the structural damage present at the defect site, ultimately leading to impaired fracture healing, making the repair of osteoporotic fractures particularly challenging in orthopaedics. Herein, we focus on investigating a combined versatile pro-anabolic and anti-catabolic effect of Magnesium (Mg. 2+. ) to modulate bone cell behaviour (3), to develop an engineered biomimetic bio-instructive biomaterial scaffold structurally designed to enhance bone formation while impeding pathological osteoclast resorption activities to facilitate better bone healing and promote repair. Pre-osteoblasts MC3T3-E1 (OBs) and osteoclasts progenitors RAW 264.7 (OCs) cell lines were cultured in growth media exposed to increasing concentrations of MgCl. 2. (0, 0.5, 1, 10, 25 and 50mM) and the optimal concentration to concurrently promote the differentiation of OBs and inhibit the differentiation or funtion of RANKL-induced OCs was assessed. We next used Fluorescence Lifetime Imaging Microscopy to investigate changes in the metabolic pathways during OBs and OCs differentiation when exposed to increasing MgCl. 2. concentrations. We developed a range of magnesium-incorporated collagen scaffolds to permit the spatiotemporal release of Mg. 2+. within the established therapeutic window, and to investigate the behaviour of bone cells in a 3D environment. In our results, we reported an increase in the expression of the bone formation markers osteocalcin and osteopontin for OBs exposed to 10mM MgCl. 2. , and a significant downregulation of the osteoclast-specific markers TRAP and cathepsin K in RANKL-induced OCs differentiation when exposed to 25mM MgCl. 2. Moreover, 25mM MgCl. 2. induced changes in the energy metabolism of OCs from a predominantly oxidative phosphorylation towards a more glycolytic pathway suggesting a regulatory effect of Mg. 2+. in the underlying mechanisms of osteoclasts formation and function. The developed porous collagen-magnesium scaffolds significantly reduced the expression of early osteoclastogenic markers RANK and NFkB, and an elevated expression of the osteogenic markers Runx2 and Col1A1 was reported after 7 days. Our research to date has provided evidences to demonstrate the potential of Mg. 2+. to concurrently enhance osteogenesis while inhibiting osteoclastogenesis in vitro, potentially introducing new targets for developing therapies to repair osteoporotic bone fractures

Shoulder arthroplasty is effective at restoring function and relieving pain in patients suffering from glenohumeral arthritis; however, cortex thinning has been significantly associated with larger press-fit stems (fill ratio = 0.57 vs 0.48; P = 0.013)1. Additionally, excessively stiff implant-bone constructs are considered undesirable, as high initial stiffness of rigid fracture fixation implants has been related to premature loosening and an ultimate failure of the implant-bone interface2. Consequently, one objective which has driven the evolution of humeral stem design has been the reduction of stress-shielding induced bone resorption; this in-part has led to the introduction of short stems, which rely on metaphyseal fixation. However, the selection of short stem diametral (i.e., thickness) sizing remains subjective, and its impact on the resulting stem-bone construct stiffness has yet to be quantified. Eight paired cadaveric humeri (age = 75±15 years) were reconstructed with surgeon selected ‘standard’ sized and 2mm ‘oversized’ short-stemmed implants. Standard stem sizing was based on a haptic assessment of stem and broach stability per typical surgical practice. Anteroposterior radiographs were taken, and the metaphyseal and diaphyseal fill ratios were quantified. Each humerus was then potted in polymethyl methacrylate bone cement and subjected to 2000 cycles of compressive loading representing 90º forward flexion to simulate postoperative seating. Following this, a custom 3D printed metal implant adapter was affixed to the stem, which allowed for compressive loading in-line with the stem axis (Fig.1). Each stem was then forced to subside by 5mm at a rate of 1mm/min, from which the compressive stiffness of the stem-bone construct was assessed. The bone-implant construct stiffness was quantified as the slope of the linear portion of the resulting force-displacement curves. The metaphyseal and diaphyseal fill ratios were 0.50±0.10 and 0.45±0.07 for the standard sized stems and 0.50±0.06 and 0.52±0.06 for the oversized stems, respectively. Neither was found to correlate significantly with the stem-bone construct stiffness measure (metaphysis: P = 0.259, diaphysis: P = 0.529); however, the diaphyseal fill ratio was significantly different between standard and oversized stems (P < 0.001, Power = 1.0). Increasing the stem size by 2mm had a significant impact on the stiffness of the stem-bone construct (P = 0.003, Power = 0.971; Fig.2). Stem oversizing yielded a construct stiffness of −741±243N/mm; more than double that of the standard stems, which was −334±120N/mm. The fill ratios reported in the present investigation match well with those of a finite element assessment of oversizing short humeral stems3. This work complements that investigation's conclusion, that small reductions in diaphyseal fill ratio may reduce the likelihood of stress shielding, by also demonstrating that oversizing stems by 2mm dramatically increases the stiffness of the resulting implant-bone construct, as stiffer implants have been associated with decreased bone stimulus4 and premature loosening2. The present findings suggest that even a small, 2mm, variation in the thickness of short stem humeral components can have a marked influence on the resulting stiffness of the implant-bone construct. This highlights the need for more objective intraoperative methods for selecting stem size to provide guidelines for appropriate diametral sizing. For any figures or tables, please contact the authors directly

Breast cancer is the most frequent malignancy in women with an estimation of 2.1 million new diagnoses in 2018. Even though primary tumours are usually efficiently removed by surgery, 20–40% of patients will develop metastases in distant organs. Bone is one of the most frequent site of metastases from advanced breast cancer, accounting from 55 to 58% of all metastases. Currently, none of the therapeutic strategies used to manage breast cancer bone metastasis are really curative. Tailoring a suitable model to study and evaluate the disease pathophysiology and novel advanced therapies is one of the major challenges that will predict more effectively and efficiently the clinical response. Preclinical traditional models have been largely used as they can provide standardization and simplicity, moreover, further advancements have been made with 3D cultures, by spheroids and artificial matrices, patient derived xenografts and microfluidics. Despite these models recapitulate numerous aspects of tumour complexity, they do not completely mimic the clinical native microenvironment. Thus, to fulfil this need, in our study we developed a new, advanced and alternative model of human breast cancer bone metastasis as potential biologic assay for cancer research. The study involved breast cancer bone metastasis samples obtained from three female patients undergoing wide spinal decompression and stabilization through a posterior approach. Samples were cultured in a TubeSpin Bioreactor on a rolling apparatus under hypoxic conditions at time 0 and for up to 40 days and evaluated for viability by the Alamar Blue test, gene expression profile, histology and immunohistochemistry. Results showed the maintenance and preservation, at time 0 and after 40 days of culture, of the tissue viability, biological activity, as well as molecular markers, i.e. several key genes involved in the complex interactions between the tumour cells and bone able to drive cancer progression, cancer aggressiveness and metastasis to bone. A good tis sue morphological and microarchitectural preservation with the presence of lacunar osteolysis, fragmented trabeculae locally surrounded by osteoclast cells and malignant cells and an intense infiltration by tumour cells in bone marrow compartment in all examined samples. Histomorphometrical data on the levels of bone resorption and bone apposition parameters remained constant between T0 and T40 for all analysed patients. Additionally, immunohistochemistry showed homogeneous expression and location of CDH1, CDH2, KRT8, KRT18, Ki67, CASP3, ESR1, CD8 and CD68 between T0 and T40, thus further confirming the invasive behaviour of breast cancer cells and indicating the maintaining of the metastatic microenvironment. The novel tissue culture, set-up in this study, has significant advantages in comparison to the pre-existent 3D models: the tumour environment is the same of the clinical scenario, including all cell types as well as the native extracellular matrix; it can be quickly set-up employing only small samples of breast cancer bone metastasis tissue in a simple, ethically correct and cost-effective manner; it bypasses and/or decreases the necessity to use more complex preclinical model, thus reducing the ethical burden following the guiding principles aimed at replacing/reducing/refining (3R) animal use and their suffering for scientific purposes; it can allow the study of the interactions within the breast cancer bone metastasis tissue over a relatively long period of up to 40 days, preserving the tumour morphology and architecture and allowing also the evaluation of different biological factors, parameters and activities. Therefore, the study provides for the first time the feasibility and rationale for the use of a human-derived advanced alternative model for cancer research and testing of drugs and innovative strategies, taking into account patient individual characteristics and specific tumour subtypes so predicting patient specific responses

Bone is a connective tissue that undergoes constant remodeling. Any disturbances during this process may result in undesired pathological conditions. A single nucleotide substitution (596T-A) in exon eight which leads to a M199K mutation in human RANKL was found to cause osteoclast-poor autosomal recessive osteopetrosis (ARO). Patients with ARO cannot be cured by hematopoietic stem cell transplantation and, without proper treatments, will die in their early age. To date, how this mutation alters RANKL function has not been characterized. We thus hypothesized that hRANKL M199 residue is a structural determinant for normal RANKL-RANK interaction and osteoclast differentiation. By sharing our findings, we aim to achieve an improved clinical outcome in treating bone-related diseases such as osteoporosis, ARO and osteoarthritis. Site-directed mutagenesis was employed to create three rat RANKL mutants, replacing the methionine 200 (human M199 equivalent residue) with either lysine (M200K), alanine (M200A) or glutamic acid (M200E). Recombinant proteins were subsequently purified through affinity chromatography and visualized by Coomassie blue staining and western blot. MTS was carried out before osteoclastogenesis assay in vitro to measure the cellular toxicity. Bone resorption pit assay, immuno-fluorescent staining, luciferase reporter assay, RT-PCR, western blot and calcium oscillation detection were also conducted to explore the biological effect of rRANKL mutants. Computational modeling, thermal Shift Assay, western blot and protein binding affinity experiments were later carried out for structural analyses. rRANKL mutants M200K/A/E showed a drastically reduced ability to induce osteoclast formation and did not demonstrate features of competitive inhibition against wild-type rRANKL. These mutants are all incapable of supporting osteoclastic polarization and bone resorption or activating RANKL-induced osteoclast marker gene transcription. Consistently, they were unable to induce calcium flux, and also showed a diminished induction of IκBa degradation and activation of NF-kB and NFATc1 transcriptional activity. Furthermore, the transcriptional activation of the antioxidant response element (ARE) crucial in modulating oxidative stress and providing cytoprotection was also unresponsive to stimulation with rM200s. Structural analyses showed that rM200 is located in a hydrophobic pocket critical for protein folding. Thermal shift and western blot assays suggested that rM200 mutants formed unstructured proteins, with disturbed trimerisation and the loss of affinity to its intrinsic receptors RANK and OPG. Taken together, we first demonstrates the underlying cause of M199-meidated ARO in a cellular and molecular level by establishing a phenotype in BMMs similar to observed in human samples. Further investigation hints the structural significance of a hydrophobic pocket within the TNF-like region. Combined with pharmaceutical studies on small-molecule drugs, this finding may represent a therapeutic target motif for future development of anti-resorptive treatments

Minimally invasive surgery for the restoration of bone tissues lost due to diseases and trauma is preferred by the health care system as the related costs are continuously increasing. Recently, efforts have been paid to optimize injectable calcium phosphate (CaP) cements which have been recognized as excellent alloplastic material for osseous augmentation because of their unique combination of osteoconductivity, biocompatibility and mouldability. The sol-gel synthesis approach appears to be the most suitable route towards performing injectable calcium phosphates. Different strategies used to prepare bioactive and osteoinductive injectable CaP are reported. CaP gels complexed with phosphoserine-tethered poly(ε-lysine) dendrons (G3-K PS) designed to interact with the ceramic phase and able to induce osteogenic differentiation of human mesenchymal stem cells (hMSCs) is discussed. Recently, attention has been given to the modification of hydroxyapatite with Strontium (Sr) due to its dual mode of action, simultaneously increasing bone formation (stimulating osteoblast differentiation) while decreasing bone resorption (inhibiting osteoclast differentiation). The effect of systems based on strontium modified hydroxyapatite (Sr-HA) at different composition on proliferation and osteogenic differentiation of hMSC is described. One more approach is based on the use of antimicrobial injectable materials. It has been demonstrated that some imidazolium, pyridinium and quaternary ammonium ionic liquids (IL) have antimicrobial activity against some different clinically significant bacterial and fungal pathogens. Here, we report several systems based on IL at different alkyl-chain length incorporated in Hydroxyapatite (HA) through the sol-gel process to obtain an injectable material with simultaneous opposite responses toward osteoblasts and microbial proliferation

Abstract. Objectives. Currently, total hip replacement surgery is an effective treatment for osteoarthritis, where the damaged hip joint is replaced with an artificial joint. Stress shielding is a mechanical phenomenon that refers to the reduction of bone density as a result of altered stresses acting on the host bone. Due to solid metallic nature and high stiffness of the current orthopaedic prostheses, surrounding bones undergo too much bone resorption secondary to stress shielding. With the use of 3D printing technology such as selective laser melting (SLM), it is now possible to produce porous graded microstructure hip stems to mimics the surrounding bone tissue properties. Method. In this study we have compared the physical and mechanical properties of two triply periodic minimal surface (TPMS) lattice structure namely gyroid and diamond TPMS. Based on initial investigations, it was decided to design, and 3D print the gyroid and diamond scaffolds having pore size of 800 and 1100 um respectively. Scaffold of each type of structure were manufactured and were tested mechanically in compression (n=8), tension (n=5) and bending (n=1). Results. Upon FEA validation of the scaffold in Abaqus, the desired scaffold for hip implant application was evaluated to have a young's modules of 12.15 GPa, yield strength of 242 MPa and porosity of 55%. Topology and lattice optimization were performed using nTopology to design an optimised graded porous hip implant based on stress shielding reduction. It was understood that the designed optimised hip implant can reduce the stress shielding effect by more than 65% when compared to the conventional generic implant. Conclusions. The designed hip implant presented in this work shows clinical promise in reducing bone loss while having enhanced osseointegration with the surrounding cortical bones. Hence, this will help reduce the risk of periprosthetic fracture and the probability of revision surgery

Abstract. Objectives. Osteocytes function as critical regulators of bone homeostasis by sensing mechanical signals. Stimulation of the mechanosensitive ion channel, Piezo1 promotes bone anabolism and deletion of Piezo1 in osteoblasts and osteocytes decreases bone mass and bone strength in mice. This study determined whether loading of osteocytes in vitro results in upregulation of the Piezo1 pathway. Methods. Human MSC cells (Y201), embedded in type I collagen gels and differentiated to osteocytes in osteogenic media 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 Piezo1 activation assessed by RNAseq analysis (NovaSeq S1 flow cell 2 × 100bp PE reads). To mimic mechanical load and activate Piezo1, Y201s were differentiated to osteocytes in 3D gels for 13 days and treated, with Yoda1 (5µM, 2 hours, n=4); vehicle treated cells served as controls (n=4). Extracted RNA was subjected to RT-qPCR and data analysed by Minitab. Results. Low mRNA expression of PIEZO1 in unloaded cells was upregulated 5-fold following 1-hr of mechanical load (p=0.003). In addition, the transcription factor NFATc1, a known regulator of Piezo1 mechanotransduction, was also upregulated by load (2.4-fold; p=0.03). Y201 cells differentiated in gels expressed the osteocyte marker, SOST. Yoda1 upregulated PIEZO1 (1.7-fold; p=0.057), the early mechanical response gene, cFOS (4-fold; p=0.006), COL1A1 (3.9-fold; p=0.052), and IL-6 expression (7.7-fold; p=0.001). Discussion. This study reveals PIEZO1 as an important mechanosenser in osteocytes. Piezo 1 mediated increases in the bone matrix protein, type I collagen, and IL-6, a cytokine that drives inflammation and bone resorption. This provides a direct link between mechanical activation of Piezo 1, bone remodelling and inflammation, which may contribute to mechanically-induced joint degeneration in osteoarthritis. Mechanistically, we hypothesise this may occur through promoting Ca2+ influx and activation of the NFAT1 signalling pathway

Aims. Osteopetrosis (OP) is a rare hereditary disease that causes reduced bone resorption and increased bone density as a result of osteoclastic function defect. Our aim is to review the difficulties, mid-term follow-up results, and literature encountered during the treatment of OP. Methods. This is a retrospective and observational study containing data from nine patients with a mean age of 14.1 years (9 to 25; three female, six male) with OP who were treated in our hospital between April 2008 and October 2018 with 20 surgical procedures due to 17 different fractures. Patient data included age, sex, operating time, length of stay, genetic type of the disease, previous surgery, fractures, complications, and comorbidity. Results. The mean follow-up period was 92.5 months (25 to 140). Bony union was observed in all of our patients. Osteomyelitis developed in two patients with femoral shaft fractures, and two patients had peri-implant stress fractures. Conclusion. Treatment of fractures in OP patients is difficult, healing is protracted, and the risk of postoperative infection is high. In children and young adults with OP who have open medullary canal and the epiphyses are not closed, fractures can be treated with surgical techniques such as intramedullary titanium elastic nail (TENS) technique or fixation with Kirschner (K)-wire. Cite this article: Bone Joint J 2020;102-B(8):1082–1087

Introduction. Reinforcement ring with allograft bone is commonly used for acetabular reconstruction of bone defects because it can achieve stable initial fixation of the prosthesis. It is not clear whether the allograft bone can function as a viable host bone and provide long-standing structural support. The purpose of this study was to assess to long-term survival of the reinforcement rings and allograft bone incorporation after acetabular revisions. Methods. We retrospectively reviewed 39 hips (37 patients) who underwent reconstruction of the acetabulum with a Ganz reinforcement ring and allograft bone in revision total hip arthroplasty. There were 18 females and 19 males with a mean age of 55.9 years (35–74 years). The minimum postoperative follow-up period was 10 years (10∼17 years). We assessed the acetabular bone defect using the Paprosky's classification. We determined the rates of loosening of the acetabular reconstructions, time to aseptic loosening, integration of the allograft bone, resorption of the allograft bone, and survival rate. Aseptic loosening of the acetabular component was defined as a change in the cup migration of more than 5 mm or a change in the inclination angle of more than 5° or breakage of the acetabular component at the time of the follow-up. Graft integration was defined as trabecular remodelling crossing the graft-host interface. Resorption of the allograft bone was classified as minor (<1/3), moderate (1/3–1/2) or severe (>1/2). Kaplan-Meier survivorship analysis was performed for aseptic loosening of the acetabular component. The results. The acetabular bone defects were classified as follows: 8 type II hips (4 type IIB, 4 type IIC), and 31 type III hips (17 type IIIA, 14 type IIIB). Fourteen (35.9%) of 39 hips was defined as aseptic loosening of an acetabular component. Loosening was more frequent in type IIIB (57.1%) than in type IIIA hips (29.4%). Mean time to aseptic loosening of the acetabular reconstructions was 6.3 years in type IIIA and from 5 years in type IIIB defects, respectively. Allograft bone incorporation was satisfactory in 66.7% of hips. There was minor bone resorption in 14.3% and moderate bone resorption in 10.2%. In 9 hips (23.1%), severe resorption of the allograft bone was observed and early component loosening was observed in these cases. The survival rate of acetabular component at 10 years of follow-up was 63.6% (95% confidence interval, 49–77%) with aseptic loosening as endpoints. Conclusions. The long-term survival rate of acetabular revision using the reinforcement ring and allograft bone in the reconstruction of severe acetabular bone defects was unsatisfactorily low due to loosening of acetabular components. Because of unfavorable graft incorporation into a host bone, an alternative component and structural support may be employed in the reconstruction of severe acetabular bone defects

Previously, we have demonstrated reduced biomechanical bone strength and matrix quality in Tachykinin (Tac)1-deficient mice lacking the sensory neuropeptide substance P (SP). A similar distortion of bone microarchitecture was described for α-calcitonin gene-related pepide (α-CGRP)-deficient mice. In previous studies we observed alterations in cell survival and differentiation capacity of bone cells isolated from wildtype mice when stimulated with SP and α-CGRP. We assume that changes in sensory neurotransmitter balance modulate bone cell metabolism thereby possibly contributing to inferior bone quality. In order to explore this hypothesis, we investigated and compared metabolic parameters in osteoblasts and osteoclasts isolated from SP- and α-CGRP-deficient mice and wildtype (WT) controls. Bone marrow-derived macrophages (BMMs) and osteoblast-like cells from female C57Bl/6J (WT-control), Tac1-deficient (Tac1-/−) and α-CGRP-deficient (α-CGRP-/−) mice were isolated and differentiated according to established protocols (Niedermair et al., 2014). Cell metabolism studies were performed for enzyme activity and cell survival. We observed reduced numbers of BMM from Tac1-/− and α-CGRP-/− mice after initial seeding compared to WT but no changes in viability. Osteoblast-like cells from Tac1-/− mice tend to migrate out faster from bone chips compared to WT-controls whereas migration of osteoblast-like cells from α-CGRP-/− mice was not affected. Osteoblasts and osteoclast/BMM cultures from WT mice endogenously synthesize and secrete SP as well as α-CGRP at a picomolar range. We found no changes regarding BMM or osteoblast proliferation from both, Tac1-/− and α-CGRP-/− mice when compared to WT-controls. Caspase 3/7-activity was reduced by trend in osteoclast/BMM cultures of α-CGRP-/− mice and significantly reduced in osteoclast/BMM cultures of Tac1-/− mice compared to WT-controls. We found significantly higher Caspase 3/7-activity in osteoblasts of Tac1-/− mice after 14 days of osteogenic culture conditions when compared to WT-controls whereas osteoblasts of α-CGRP-/− mice were unaffected. Cathepsin K enzyme activity was significantly reduced in osteoclast/BMM cultures of Tac1-/− and α-CGRP-/− mice compared to WT-controls. ALP activity of Tac1-/− osteoblasts was higher after 7 days and reduced after 21 days of osteogenic culture compared to WT-controls whereas ALP activity of osteoblasts of α-CGRP-/− mice was unchanged. Acccording to our in vitro observations, we suggest some reduction in bone resorption rate but concomitantly a reduction in bone formation rate in Tac1-/− mice compared to WT-controls resulting in a net bone loss in these mice as bone resorption is faster than bone formation. Furthermore, we assume that bone resorption rate is slightly reduced in α-CGRP-/− mice but bone formation rate seems to be unchanged. Therefore we hypothesize that additional conditions present in vivo might contribute to the inferior bone properties of α-CGRP-/− mice

The triple taper polished cemented stem (C-stem, DePuy) was developed to promote calcar loading, and reduce proximal femoral bone resorption and aseptic loosening. We aimed to evaluate the changes in peri-prosthetic bone mineral density using Dual Energy X-ray Absorbtiometry (DEXA) after total hip arthroplasty (THA) using the C-stem prosthesis. One hundred and three patients were recruited voluntarily through and single institution for THA. The prosthesis used was the triple-taper polished cemented C-Stem (De Puy, Warsaw, Indiana, USA). DEXA scans were performed pre- operatively, then at day for, three months, nine months, 18 months and 24 months post-operativley. Scans were analysed with specialised software (Lunar DPX) to measure bone mineral density (BMD) in all seven Gruen zones at each time interval. Changes in calcar BMD were also correlated with patient age, sex, surgical approach, pre-operative BMD and post-operative mobility to identify risk factors for periprosthetic bone resorption. One hundred and three patients underwent 103 primary THA over a five-year period (98 osteoarthritis; 5 AVN). No femoral components were loose at the two year review and none were revised. The most marked bone resorption occured in Gruen zones 1 and 7, and was best preserved in zone 5. BMD decreased rapidly in all zones in the first three months post-operatively, after which the rate of decline slowed substantially. BMD was better preserved medially (zones 6 and 5) than laterally (zones 2 and 3) at 24 months. There was delayed recovery of BMD in all zones except zones 4 and 5. High pre-operative T-scores (>2.0) in the spine, ipsilateral and contralateral femoral neck were associated with the higher post-operative BMD and less bone resorption at all time intervals in Gruen zone 7. Pre-operative osteopenia and osteoporosis were associated with low BMD and accelerated post-operative bone resorption in zone 7. Patients whose mobility rendered them housebound had lower post-operative BMD, and accelerated post-operative BMD loss in zone 7 when compared to non-housebound patients. Females had a lower post-operative BMD and greater loss of BMD in zone 7. Patient age and surgical approach did not effect post-operative BMD or rate of bone resorption in zone 7. The triple-taper femoral stem design did not show an increase in periprosthetic bone density at the proximal femur at two years post-operative. Calcar bone resorption is accelerated by low pre-operative BMD, poor post-operative mobility, and in females. Age and surgical approach do not have significant effects on calcar bone remodelling

Introduction and Objective. Alveolar bone resorption following tooth extraction or periodontal disease compromises the bone volume required to ensure the stability of an implant. Guided bone regeneration (GBR) is one of the most attractive technique for restoring oral bone defects, where an occlusive membrane is positioned over the bone graft material, providing space maintenance required to seclude soft tissue infiltration and to promote bone regeneration. However, bone regeneration is in many cases impeded by a lack of an adequate tissue vascularization and/or by bacterial contamination. Using simultaneous spray coating of interacting species (SSCIS) process, a bone inspired coating made of calcium phosphate-chitosan-hyaluronic acid was built on one side of a nanofibrous GBR collagen membrane in order to improve its biological properties. Materials and Methods. First, the physicochemical characterizations of the resulting hybrid coating were performed by scanning electron microscopy, X-ray photoelectron, infrared spectroscopies and high-resolution transmission electron microscopy. Then human mesenchymal stem cells (MSCs) and human monocytes were cultured on those membranes. Biocompatibility and bioactivity of the hybrid coated membrane were respectively evaluated through MSCs proliferation (WST-1 and DNA quantification) and visualization; and cytokine release by MSCs and monocytes (ELISA and endothelial cells recruitment). Antibacterial properties of the hybrid coating were then tested against S. aureus and P. aeruginosa, and through MSCs/bacteria interactions. Finally, a preclinical in vivo study was conducted on rat calvaria bone defect. The newly formed bone was characterized 8 weeks post implantation through μCT reconstructions, histological characterizations (Masson's Trichrome and Von Kossa stain), immunohistochemistry analysis and second harmonic generation. Biomechanical features of newly formed bone were determined. Results. The resulting hybrid coating of about 1 μm in thickness is composed of amorphous calcium phosphate and carbonated poorly crystalline hydroxyapatite, wrapped within chitosan/hyaluronic acid polysaccharide complex. Hybrid coated membrane possesses excellent bioactivity and capability of inducing an overwhelmingly positive response of MSCs and monocytes in favor of bone regeneration. Furthermore, the antibacterial experiments showed that the hybrid coating provides contact-killing properties by disturbing the cell wall integrity of Gram-positive and Gram-negative bacteria. Its combination with MSCs, able to release antibacterial agents and mediators of the innate immune response, constitutes an excellent strategy for fighting bacteria. A preclinical in vivo study was therefore conducted in rat calvaria bone defect. μCT reconstructions showed that hybrid coated membrane favored bone regeneration, as we observed a two-fold increase in bone volume / total volume ratios vs. uncoated membrane. The histological characterizations revealed the presence of mineralized collagen (Masson's Trichrome and Von Kossa stain), and immunohistochemistry analysis highlighted a bone vascularization at 8 weeks post-implantation. However, second harmonic generation analysis showed that the newly formed collagen was not fully organized. Despite a significant increase in the elastic modulus of the newly formed bone with hybrid coated membrane (vs. uncoated membrane), the obtained values were lower than those for native bone (approximately 3 times less). Conclusions. These significant data shed light on the regenerative potential of such bioinspired hybrid coating, providing a suitable environment for bone regeneration and vascularization, as well as an ideal strategy to prevent bone implant-associated infections

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

Introduction and Objective. Curative resection of proximal humerus tumours is now possible in this era of limb salvage with endoprosthetic replacement considered as the preferred reconstructive option. However, it has also been linked with mechanical and non-mechanical failures such as stem fracture and aseptic loosening. One of the challenges is to ensure that implants will endure the mechanical strain under physiological loading conditions, especially crucial in long surviving patients. The objective is to investigate the effect of varying prosthesis length on the bone and implant stresses in a reconstructed humerus-prosthesis assembly after tumour resection using finite element (FE) modelling. Methods. Computed tomography (CT) scans of 10 humeri were processed in Mimics 17 to create three-dimensional (3D) cortical and cancellous solid bone models. Endoprostheses of different lengths manufactured by Stryker were modelled using Solidworks 2020. The FE models were divided into four groups namely group A consisting of the intact humerus and groups B, C and D composed of humerus-prosthesis assemblies with a body length of 40, 100 and 120 mm respectively and were meshed using linear 4-noded tetrahedral elements in 3matic 13. The models were then imported into Abaqus CAE 6.14. Isotropic linear elastic behaviour with an elastic modulus of 13400, 2000 and 208 000 MPa were assigned to the cortical bone, cancellous bone and prosthesis respectively and a Poisson's ratio of 0.3 was assumed for each material. To represent the lifting of heavy objects and twisting motion, a tensile load of 200 N for axial loading and a 5 Nm torsional load for torsional loading was applied separately to the elbow joint surface with the glenohumeral joint fixed and with all contact interfaces defined as fully bonded. A comparative analysis against literature was performed to validate the intact model. Statistical analysis of the peak von Mises stress values collected from predicted stress contour plots was performed using a one-way repeated measure of analysis of variance (with a Bonferroni post hoc test) using SPSS Statistics 26. The average change in stress of the resected models from the intact state were then determined. Results. The validation of the intact humerus displayed a good agreement with literature values. The peak bone stress occurred distally above the coronoid and olecranon fossa closer to the load application region in the intact and resected bone models with a significant amount of loading borne by the cortical bone, while the peak implant stress occurred at the bone-prosthesis contact interface under both loading conditions. Based on the results obtained, a statistically significant difference (p =.013) in implant stress was only seen to occur between groups B and C under tension. Results illustrate initiation of stress shielding with the bone bearing lesser stress with increasing resection length which may eventually lead to implant failure by causing bone resorption according to Wolff's law. The peak implant stress under torsion was 3–5 times the stress under tension. The best biomechanical behaviour was exhibited in Group D, having the least average change in stress from the intact model, 5% and 3.8% under tension and torsion respectively. It can be deduced that the shorter the prosthesis length, the more pronounced the effect on cortical bone remodelling. With the maximum bone and implant stresses obtained being less than their yield strength, it can be concluded that the bone-implant construct is safe from failure. Conclusions. The developed FE models verified the influence of varying the prosthesis length on the bone and implant stresses and predicted signs of stress shielding in longer endoprostheses. By allowing for 2 cm shortening in the upper extremity and post-surgical scarring, it is beneficial to err towards a shorter endoprosthesis

Charcot neuroarthropathy is a rare but serious complication of diabetes, causing progressive destruction of the bones and joints of the foot leading to deformity, altered biomechanics and an increased risk of ulceration. Management is complicated by a lack of consensus on diagnostic criteria and an incomplete understanding of the pathogenesis. In this review, we consider recent insights into the development of Charcot neuroarthropathy. It is likely to be dependent on several interrelated factors which may include a genetic pre-disposition in combination with diabetic neuropathy. This leads to decreased neuropeptides (nitric oxide and calcitonin gene-related peptide), which may affect the normal coupling of bone formation and resorption, and increased levels of Receptor activator of nuclear factor kappa-B ligand, potentiating osteoclastogenesis. Repetitive unrecognized trauma due to neuropathy increases levels of pro-inflammatory cytokines (interleukin-1β, interleukin-6, tumour necrosis factor α) which could also contribute to increased bone resorption, in combination with a pre-inflammatory state, with increased autoimmune reactivity and a profile of monocytes primed to transform into osteoclasts - cluster of differentiation 14 (CD14). Increased blood glucose and loss of circulating Receptor for Advanced Glycation End-Products (AGLEPs), leading to increased non-enzymatic glycation of collagen and accumulation of AGLEPs in the tissues of the foot, may also contribute to the pathological process. An understanding of the relative contributions of each of these mechanisms and a final common pathway for the development of Charcot neuroarthropathy are still lacking. Cite this article: S. E. Johnson-Lynn, A. W. McCaskie, A. P. Coll, A. H. N. Robinson. Neuroarthropathy in diabetes: pathogenesis of Charcot arthropathy. Bone Joint Res 2018;7:373–378. DOI: 10.1302/2046-3758.75.BJR-2017-0334.R1

The objective of this study was to investigate the effects of different doses rhBMP-2 on bone healing in an ovine lumbar interbody fusion model. In this study 22 sheep underwent two level lumbar interbody fusion using a ventrolateral approach with secondary dorsal fixation at L1/2 and L3/4. After randomization in one level a PEEK-cage was implanted filled with one of three doses rhBMP-2 (0,5mg; 1mg; 2mg) delivered on an ACS. The other level received an empty PEEK-cage or ACS filled cage. Animals were sacrificed after 3 and 6 months and decalcified histology was performed. This included histomorphological analysis well as histomorphometry of the tissues within the cage. At 3 months after surgery the groups treated with rhBMP-2 showed higher amounts of bone tissue within the cage. At 6 months the amounts of bone tissue increased in all groups, were still lower in the groups without growth factor. At 3 months there was only one active osteolysis in the cage/ACS. 7 of 8 segments of the rhBMP-2 groups had a compromised bone structure around the implant. These areas were filled with fibrous tissue and fibrocartilage. This finding was not detected in the groups without rhBMP-2 at 3 months. At 6 months most of the segments with an empty cage or cage/ACS showed a chronic inflammation. Predominant cells were macrophages and giant cells. The groups treated with rhBMP-2 showed only a few mild chronic inflammatory reactions. The well-known dose dependent effect of rhBMP-2 on bone healing could also be recognized in our study. Attention has to be payed to the proinflammatory properties of the growth factor. Consistent with other studies we found 2 strong inflammatory reactions, each one in the lowest and highest dose group. Also, the potential for causing transient bone resorptions, according to the results of others, was demonstrated. At 3 months 7 of 8 segments treated with rhBMP-2 showed compromised peri-implant bone. Osteoblasts, but not osteoclasts, were seen in the periphery of these areas. It can be concluded that there where bone resorptions which already merged into an increased osteoblastic activity. Usually resorptions occur between 2 and 12 weeks and are followed by a period of increased osteoblastic activity. This finding wasn't recognized at 6 months anymore. Striking is that at 6 months most of the segments without rhBMP-2 showed a compromised bone structure around the implant with a mild to mainly moderate chronic inflammatory reaction. This cannot be attributed to the growth factor. Also, the ACS is degraded at 6 months and is unlikely a possible explanation. Therefore, the cage as a reason must be considered and it has to be questioned whether PEEK is the optimal material for interbody cages

Osteoporosis is a mineral bone disease arising from the predominance of osteoclastic bone resorption. Bisphosphonates which inhibit osteoclasts are commonly used in osteoporosis treatment, but are not without severe adverse effects like osteonecrosis of the jaw. The mechanisms behind the development of such phenomena is not well understood. Bone homeostasis is achieved through an intimate cross-talk between osteoclasts and osteoblasts. Thus, it is important to visualise activities of these cells simultaneously in situ. Currently, there are means to visualise osteoclast shape and numbers with tartrate-resistant alkaline phosphatase (TRAP) staining but no practical and accurate methods to quantify osteoclast activity in situ. This investigation aims to establish the use of ELF97, a substrate of TRAP, to visualise and quantify osteoclast activity. This provides vital clues to mechanisms of various bone disorders. TRAP dephosphorylation of ELF97 results in a detectable fluorescent product at areas of osteoclast activity. Osteoclastic activity was initiated in zebrafish by inducing crush injuries in tail fin rays. Colocalisation of ELF97 fluorescence with osteoclast-specific DsRed in transgenic zebrafish, visualised under confocal microscopy, is used to further establish the specificity of ELF97 to sites of osteoclastic activity. Quantification is established by comparing fluorescence between wild type, osteoclast-deficient mutants and bisphosphonate-treated zebrafish. The utility of ELF97 will also be investigated in terms of the stability of the florescent product. The investigation revealed that ELF97 and DsRed fluorescence were found commonly at crush sites with osteoclastic activity. Wild type zebrafish had greater fluorescence compared to osteoclast-deficient (p<0.0001) and bisphosphonate-treated zebrafish (p<0.0001) after 7 and 14 days post-crush, revealing that fluorescence from ELF97 corresponds to expected osteoclastic activity. Fluorescence of tail fins treated with ELF97 did not diminish over a period of 21 days of storage, demonstrating its stability. ELF97 is thus a useful means to visualise osteoclast activity, potentially crucial in more advanced investigations to understand bone disorders. It could be used in combination with other cellular markers in whole biological samples to study and experimentally manipulate bone remodelling

Fracture healing results in increased markers of bone turnover and callus formation. The exact patterns of these changes after different type and locations of fractures as well as weight bearing are unknown. Bone markers and the callus index were measured prospectively for 6 month following osteosynthesis of different fractures of the lower limb. Serum and urin samples were collected at day 0, 1, 3, 7 and after 2, 6, 12 and 24 weeks. X-rays were taken direct postoperatively and after 6 and 24 weeks. Labarotory parameters for bone formation were: bone-specific alkaline phosphatase (BnAP), Osteocalcin (OC), procollagen type I N- and type III C-terminal propeptide (PINP, PIIICP); markers for bone resorption were: free and peptid-bound forms of urinary pyridinium crosslinks (Dpd, Pyr,), N – terminal propeptides of type I collagen (NTx). All fractures healed within 6 month without complications. Results: We present preliminary data obtained from 12 adults (10 male, 2 female, mean age 45±15 years). a great variability of bone formation and resorption markers was observed during the first two weeks, probably due to the type trauma and amount of soft tissue injury. Accelerated bone resorption, and a decrease of bone formation was observed during the first week. Thereafter, an increase in OC and BnAP was noted despite persistently elevated bone resorption markers. With increasing weigth bearing, a decrease of bone resorption markers with unchanged or slightly increasing levels of bone formation markers occured. Conclusions: No fracture specific trends for changes in bone remodelling markers were observed. Accelerated bone resorption is followed by increased bone formation; the longer and steeper the increase on bone resorption, the later and more pronounced the increase in bone formation. For further evaluation of the relationship between changes in bone remodeling markers and fracture healing, more patients will be included into the ongoing study

Total shoulder arthroplasty (TSA) is an effective treatment for end-stage glenohumeral arthritis. The use of high modulus uncemented stems causes stress shielding and induces bone resorption of up to 63% of patients following TSA. Shorter length stems with smaller overall dimensions have been studied to reduce stress shielding, however the effect of humeral short stem varus-valgus positioning on bone stress is not known. The purpose of this study was to quantify the effect of humeral short stem varus-valgus angulation on bone stresses after TSA. Three dimensional models of eight male cadaveric humeri (mean±SD age:68±6 years) were created from computed tomography data using MIMICS (Materialise, Belgium). Separate cortical and trabecular bone sections were created, and the resulting bone models were virtually reconstructed three times by an orthopaedic surgeon using an optimally sized short stem humeral implant (Exactech Preserve) that was placed directly in the center of the humeral canal (STD), as well as rotated varus (VAR) or valgus (VAL) until it was contacting the cortex. Bone was meshed using a custom technique which produced identical bone meshes permitting the direct element-to-element comparison of bone stress. Cortical bone was assigned an elastic modulus of 20 GPa and a Poisson's ratio of 0.3. Trabecular bone was assigned varying stiffness based on CT attenuation. A joint reaction force was then applied to the intact and reconstructed humeri representing 45˚ and 75˚ of abduction. Changes in bone stress, as well as the expected bone response based on change in strain energy density was then compared between the intact and reconstructed states for all implant positions. Both varus and valgus positioning of the humeral stem altered both the cortical and trabecular bone stresses from the intact states. Valgus positioning had the greatest negative effect in the lateral quadrant for both cortical and trabecular bone, producing greater stress shielding than both the standard and varus positioned implant. Overall, the varus and standard positions produced values that most closely mimicked the intact state. Surprisingly, valgus positioning produced large amounts of stress shielding in the lateral cortex at both 45˚ and 75˚ of abduction but resulted in a slight decrease in stress shielding in the medial quadrant directly beneath the humeral resection plane. This might have been a result of direct contact between the distal end of the implant and the medial cortex under loading which permitted load transfer, and therefore load-reduction of the lateral cortex during abduction. Conversely, when the implant was placed in the varus angulation, noticeable departures in stress shielding and changes in bones stress were not observed when compared to the optimal STD position. Interestingly, for the varus positioned implant, the deflection of the humerus under load eliminated the distal stem-cortex contact, hence preventing distal load transfer thus precluding the transfer of load

Introduction. Total shoulder arthroplasty (TSA) is an effective treatment to restore shoulder function and alleviate pain in the case of glenohumeral arthritis [1]. Stress shielding, which occurs when bone stress is reduced due to the replacement of bone with a stiffer metallic implant, causes bone resorption of up to 9% of the humeral cortical thickness following TSA [2]. Shorter length stems and smaller overall geometries may reduce stress shielding [3], however the effect of humeral head backside contact with the resection plane has not yet been fully investigated on bone stress. Therefore, the purpose of this study was to quantify the effect of humeral head contact conditions on bone stresses following TSA. Methods. 3D models of eight male left cadaveric humeri (68±6 years) were generated from CT data using MIMICS. These were then virtually prepared for reconstruction by an orthopaedic surgeon to accept a short-stem humeral implant (Exactech Equinoxe® Preserve) that was optimally sized and placed centrally in the humeral canal. The humeral head was positioned in the inferior-medial position such that contact was achieved on the medial cortex, and no contact existed on the lateral cortex. Three different humeral head backside contact conditions were investigated (Figure 1); full backside contact (FULL), contact with only the inferior-medial half of the resection (INF), and contact with only the superior-lateral half of the resection (SUP). Cortical bone was assigned an elastic modulus of 20 GPa and a Poisson's ratio of 0.3. Trabecular bone was assigned varying stiffness based on CT attenuation [4]. A joint reaction force was then applied representing 45˚ and 75˚ of abduction [5]. Changes in bone stress, as well as the expected bone response based on change in strain energy density [6] was then compared between the intact and reconstructed states. Results. For cortical bone, the full backside contact altered bone stress by 28.9±5.5% compared to intact, which was significantly less than the superior (37.0±3.9%, P=0.022) and inferior (53.4±3.9%, P<0.001) backside contact conditions. Similar trends were observed for changes in trabecular bone stress relative to the intact state, where the full backside contact altered bone stress by 86.3±27.9% compared to intact, compared to the superior and inferior contact conditions, which altered bone stress by 115.2±45.0% (P=0.309) and 197.4±80.2% (P=0.024), respectively. In terms of expected bone response, both the superior and inferior contact resulted in an increase in bone volume with resorbing potential compared to the full contact (Figure 2). Discussion and Conclusions. The results of this study show that full humeral head backside contact with the humeral resection plane is preferable for short stem humeral TSA implants with the head in the inferior-medial position. As expected, the superior contact typically increased resorption potential in the medial quadrant due to the lack of load transfer, however interestingly the inferior contact increased resorption potential in both the lateral and medial quadrants. Analysis of implant micromotion showed that medial liftoff of the implant occurred, which resulted in a lack of load transfer in the most medial aspect of the resection plane. For any figures or tables, please contact the authors directly

Background. Stemless prostheses are recognized to be an effective solution for anatomic total shoulder arthroplasty (TSA) while providing bone preservation and shortest operating time. Reverse shoulder arthroplasty (RSA) with stemless has not showed the same effectiveness, as clinical and biomechanical performances strongly depend on the design. The main concern is related to stability and bone response due to the changed biomechanical conditions; few studies have analyzed these effects in anatomic designs through Finite Element Analysis (FEA), however there is currently no study analyzing the reverse configuration. Additionally, most of the studies do not consider the effect of changing the neck-shaft angle (NSA) resection of the humerus nor the proper assignment of spatial bone properties to the bone models used in the simulations. The aim of this FEA study is to analyze bone response and primary stability of the SMR Stemless prosthesis in reverse with two different NSA cuts and two different reverse angled liners, in bone models with properties assigned using a quantitative computed tomography (QCT) methodology. Methods. Sixteen fresh-frozen cadaveric humeri were modelled using the QCT-based finite element methodology. The humeri were CT-scanned with a hydroxyapatite phantom to allow spatial bone properties assignment [Fig. 1]. Two implanted SMR stemless reverse configurations were considered for each humerus: a 150°-NSA cut with a 0° liner and a 135°-NSA cut with a 7° sloped liner [Fig. 2]. A 105° abduction loading condition was simulated on both the implanted reverse models and the intact (anatomic) humerus; load components were derived from previous dynamic biomechanical simulations on RSA implants for the implanted stemless models and from the OrthoLoad database for the intact humeri. The postoperative bone volume expected to resorb or remodel [Fig. 3a] in the implanted humeri were compared with their intact models in sixteen metaphyseal regions of interest (four 5-mm thick layers parallel to the resection and four anatomical quadrants) by means of a three-way repeated measures ANOVA followed by post hoc tests with Bonferroni correction. In order to evaluate primary stability, micromotions at the bone-Trabecular Titanium interface [Fig. 3b] were compared between the two configurations using a Wilcoxon matched-pairs signed-rank test. The significance level α was set to 0.05. Results. With the exception of the most proximal layer (0.0 – 5.0 mm), the 150°-NSA configuration showed overall a statistically significant lower bone volume expected to resorb (p = 0.011). In terms of bone remodelling, the 150°-NSA configuration had again a better response, but fewer statistically significant differences were found. Regarding micromotions, there was a median decrease (Mdn = 3.2 μm) for the 135°-NSA configuration (Mdn = 40.3 μm) with respect to the 150°-NSA configuration (Mdn = 43.5 μm) but this difference was non-significant (p = 0.464). Conclusions. For the analyzed SMR Stemless configurations, these results suggest a reduction in the risk of bone resorption when a 0° liner is implanted with the humerus cut at 150°. The used QCT-based methodology will allow further investigation, as this study was limited to one single design and load case. For any figures or tables, please contact the authors directly

INTRODUCTION. It is generally accepted that strong hammering is necessary for the press fit fixation of a joint prosthesis. In this regard, large stress must remain within bone tissues for a long period. This residual stress is, however, some different from the feasible mechanical stimuli for bone tissues because that is stationary, continuous and directed from within outward unlike physiological conditions. The response on this residual stress, which may induce the disorder of the fixation of implant, has not been discussed, yet. In the present study, we designed an experimental method to exert a stationary load from inside of a femur of a rat by inserting a loop spring made from a super elastic wire of titanium alloy. Response of the femur was assessed by bone morphology mainly about the migration of the wire into the bone twelve weeks after the implantation. MATERIALS AND METHODS. We developed a method using a loop spring made of super elastic wire of titanium alloy, which can maintain sufficient magnitude of stress in a rat femur during the experimental period. The loop spring was fabricated with a wire of 0.4 mm diameter before the quenching process. Eleven Wistar rats of ten weeks old were used for the experiments. The loop spring was inserted the right femur, as shown in Figure 1. The left femur was remained intact. The compressive load was added from within outward of bone marrow when the spring was compressed with the insertion into a bone marrow of a rat femur, as shown in Figure 2. The average contact stress was calculated by dividing the elastic force by the spring and bone contact area. The contact stress was distributed from 62 to 94 MPa, which are sufficiently lower than the yield stress of cortical bone [1]. The assessment of bone morphology around the implanted loop spring was performed by micro-CT imaging after the twelve weeks of cage activity. RESULTS. To assess the migration of the spring in the femur, we measured the distance from the endocortical surface to the periphery of the spring, on the micro CT image, as shown in Figure 3. Apparent migration of the spring wire was observed on nine specimens among the eleven. Deep migration over 0.3 mm was observed at three cases. DISCUSSION. The migration of the wire in cortical bone was accompanied with the bone resorption on the surface of the wire toward outside. Therefore, the present findings suggest that stationary load at the implant surface can induce endosteal bone resorption and prosthesis dislocation and protrusion. CONCLUSION. We developed a method for configuring a stationary stress field in a rat femur using a loop spring with the super elasticity. It was found that stationary stress about 70 MPa can induce bone resorption

Introduction. The objective of this study was to investigate the effects of different doses rhBMP-2 on bone healing in an ovine lumbar interbody fusion model. Methods. In this study 22 sheep underwent two level lumbar interbody fusion using a ventrolateral approach with secondary dorsal fixation at L1/2 and L3/4. After randomization in one level a PEEK-cage was implanted filled with one of three doses rhBMP-2 (0,5mg; 1mg; 2mg) delivered on an ACS. The other level received an empty PEEK-cage or ACS filled cage. Animals were sacrificed after 3 and 6 months and decalcified histology was performed. This included histomorphological analysis as well as histomorphometry of the tissues within the cage. Results. At 3 months after surgery the groups treated with rhBMP-2 showed higher amounts of bone tissue within the cage. At 6 months the amounts of bone tissue increased in all groups, but were still lower in the groups without growth factor. At 3 months there was only one active osteolysis in the cage/ACS. 7 of 8 segments of the rhBMP-2 groups had a compromised bone structure around the implant. These areas were filled with fibrous tissue and fibrocartilage. This finding was not detected in the groups without rhBMP-2 at 3 months. At 6 months most of the segments with an empty cage or cage/ACS showed a chronic inflammation. Predominant cells were macrophages and giant cells. The groups treated with rhBMP-2 showed only a few mild chronic inflammatory reactions. Discussion. The well-known dose dependent effect of rhBMP-2 on bone healing could also be recognized in our study. Attention has to be payed for the proinflammatory properties of the growth factor. Consistent with other studies we found 2 strong inflammatory reactions, each one in the lowest and highest dose group. Also the potential for causing transient bone resorptions, according to the results of others, was demonstrated. At 3 months 7 of 8 segments treated with rhBMP-2 showed compromised peri-implant bone. Osteoblasts, but not osteoclasts, were seen in the periphery of these areas. It can be concluded that there where bone resorptions which already merged into an increased osteoblastic activity. Usually resorptions occur between 2 and 12 weeks and are followed by a period of increased osteoblastic activity. This finding wasn”t recognized at 6 months anymore. Striking is that at 6 months most of the segments without rhBMP-2 showed a compromised bone structure around the implant with a mild to mainly moderate chronic inflammatory reaction. This cannot be attributed to the growth factor. Also the ACS is degraded at 6 months and is unlikely a possible explanation. Therefore, the cage as a reason must be considered and it has to be questioned whether PEEK is the optimal material for interbody cages

Aims. Limb salvage in bone tumour patients replaces the bone with massive segmental prostheses where achieving bone integration at the shoulder of the implant through extracortical bone growth has been shown to prevent loosening. This study investigates the effect of multidrug chemotherapy on extracortical bone growth and early radiological signs of aseptic loosening in patients with massive distal femoral prostheses. Methods. A retrospective radiological analysis was performed on adult patients with distal femoral arthroplasties. In all, 16 patients were included in the chemotherapy group with 18 patients in the non-chemotherapy control group. Annual radiographs were analyzed for three years postoperatively. Dimensions of the bony pedicle, osseointegration of the hydroxyapatite (HA) collar surface, bone resorption at the implant shoulder, and radiolucent line (RLL) formation around the cemented component were analyzed. Results. A greater RLL score (p = 0.041) was observed at three years postoperatively, with those receiving chemotherapy showing greater radiological loosening compared with those not receiving chemotherapy. Chemotherapy patients experience osteolysis at the shoulder of the ingrowth collar over time (p < 0.001) compared with non-chemotherapy patients where osteolysis was not observed. A greater median percentage integration of the collar surface was observed in the non-chemotherapy group (8.6%, interquartile range (IQR) 0.0% to 37.9%; p = 0.021) at three years. Bone growth around the collar was observed in both groups, and no statistical difference in amount of extracortical bony bridging was seen. Conclusion. Multidrug chemotherapy affects the osseointegration of ingrowth collars and accelerates signs of radiological loosening. This may increase the risk of aseptic loosening in patients with massive segmental implants used to treat bone cancer. Cite this article: Bone Joint Res 2020;9(7):333–340

Introduction: The long term success of impaction grafting depends on the remodelling process during incorporation. This project was designed to characterise any differences in the biochemical markers of bone turnover following revision hip arthroplasty performed with or without impaction grafting. Methods: 87 patients undergoing revision hip arthroplasty were entered into this prospective study and grouped according to whether impaction allograft was used or not. Biochemical markers of bone turnover were assessed pre-operatively and post-operatively on day 2, day 9, week 6, 6 months and 1 year. Osteocalcin, pro-collagen type-I N-terminal propeptide and bone specific alkaline phosphatase were measured as bone formation markers. C-telopeptide, pyridinoline and deoxypyridinoline were measured as bone resorption markers. Results: All patients had a successful radiological and clinical outcome at one year. 50 patients with radiologically defined host-graft union were compared with 37 patients who did not receive allograft. Markers of bone formation tended to rise by day 9 but the rise in osteocalcin was delayed in the graft group and was significantly lower at 6 months in comparison to the non-graft group (p=0.002). Alkaline phosphatase levels remained significantly elevated at one year in the graft group (p=0.027) whilst levels in the non-graft group had normalised. Markers of bone resorption also rise in both groups but with no significant differences between the groups. Discussion: Following impaction grafting, new bone formation may be delayed in comparison to revisions performed without graft. The pattern of markers of bone resorption did not differ significantly between the groups suggesting that there is no large scale resorption of the impacted allograft in these cases. These results provide a biochemical insight into the bone formation and bone resorption processes during allograft incorporation

Introduction: The long term success of impaction grafting depends on the remodelling process during incorporation. This project was devised to characterise any differences in the biochemical markers of bone turnover following revision hip arthroplasty performed with or without impaction grafting. Methods: 87 patients were entered into this prospective study and grouped according to whether impaction allograft was used or not. Biochemical markers of bone turnover were assessed pre-operatively and post-operatively on day 2, day 9, week 6, 6 months and 1 year. Osteocalcin, procollagen type-I N-terminal propeptide and bone specific alkaline phosphatase were measured as bone formation markers. C-telopeptide, pyridinoline and deoxypyridinoline were measured as bone resorption markers. Results: All patients had a successful outcome at one year. 50 patients with radiologically defined host-graft union were compared with 37 patients who did not receive an allograft. Markers of bone formation tended to rise by day 9 but the rise in osteocalcin was delayed in the graft group and was significantly lower at 6 months in comparison to the non-graft group (p=0.002). Alkaline phosphatase levels remained significantly elevated at one year in the graft group (p=0.027) whilst levels in the non-graft group had normalised. Markers of bone resorption also rise in both groups but with no significant differences between the groups. Discussion: Following impaction grafting, new bone formation may be delayed in comparison to revisions performed without graft. The pattern of markers of bone resorption did not differ significantly between the groups suggesting that there is no large scale resorption of the impacted allograft in these cases. These results provide a biochemical insight into the bone formation and bone resorption processes during allograft incorporation

Summary. Arginine supplementation is helpful in treatment of osteoporosis. Introduction. Nitric oxide (NO) is a short-lived free radical involved in several biological processes as a bioregulator and as a second messenger. It inhibits osteoclastic bone resorption in vitro and regulates bone remodeling. Zolendronic acid has been established as a treatment for post menopausal osteoporosis. Study was done to compare the efficacy of Nitic oxide donor (L-arginine) with that of Zolendronic acid for the treatment of osteoporosis. Method. The study was not designed to compare these two drugs against a placebo, because the beneficial effects of Zolendronic acid in treatment of osteoporosis are well established. Institutional Review Board approvals were obtained. One hundred patients of osteoporosis having T score of −2.5 or more, were randomised to receive L-arginine) or Zolendronic acid. All patients received 1.0 g of calcium and 400 IU of vitamin D supplementation per day. In addition Group I patients received L-arginine (2 gm.) per day while Group II patients received zoledronic acid 5 mg i.v. over 15 min. Patient were followed at regular intervals clinically, by biochemical investigations and at one year for DEXA scan. Results. Patients in both groups improved clinically and bio-chemically over one year period. T score on DEXA scan at one year showed improvement in bone density. Average pretreatment T score was −3.65 in group I and −3.52 in group II. At one year followup average T score was −2.9 in group I and −2.6 in group II. Difference was not statistically significant. Discussion. Oral administration of L-arginine in pharmacological doses induces growth hormone and insulin like growth factor-1 responses and stimulates nitric oxide synthesis. Growth hormone and insulin like growth factor-1 are important mediator of bone turnover and osteoblastic bone formation. While nitric oxide is potent inhibitor of osteoclastic bone resorption because of this dual effect on physiological regulator of bone remodeling. L-arginine could potentially increase bone formation over bone resorption and consequently increase bone mass. Oral supplementation of L-arginine may be novel strategy in prevention and treatment of osteoporosis

Aim: Urinary C-terminal telopeptide of type I collagen (u-CTx) has been reported to be a sensitive biochemical marker of bone turnover. There have been two assays for urinary CTx, which are u-aCTx and u-BCTx. A newly developed immunoassay for serum CTx (s-CTx) is now available for assessment of bone resorption. We have both evaluated the effects of menopause, and osteoporosis on the measurements of serum CTx and compared them to urinary CTx assays. Subjects: 79 premenopausal healthy women, 80 post-menopausal healthy women, 61 osteoporotic patients with vertebral fractures and 34 osteoporotic patients with hip fractures. Results: Bone resorption markers were increased after menopause. There was no significant difference among s-CTx, u-aCTx and u-BCTx in the T-scores of post-menopausal group over premenopausal group (T -score; s-CTx:2.3, u-aCTx:1.8, u-BCTx:2.1). Patients with vertebral fractures and patients with hip fracture had elevated levels of bone resorption markers compared to age-matched healthy postmenopousal women. There was no significant difference among s-CTx, u-aCTx and u-BCTx in the T-scores against postmenopausal group in vertebral fracture group (T -score; s-CTx:0.8, u-aCTx:0.9, u-BCTx:0.7) and in hip fracture group women (T-score; s-CTx:1.1, u-aCTx: 1.3 u-BCTx: 1.3). Conclusions: These findings indicate that s-CTx reflects the increase of bone resorption associated with menopause and osteoporosis with vertebral fractures and hip fractures

Aseptic loosening is a growing problem for orthopaedic surgeons and the importance of elevated hydrostatic pressure in its development in vivo is now well documented, but the mechanisms by which pressure could enhance loosening are unclear. We have demonstrated that hydrostatic pressures increased MP synthesis of cytokines, chemokines, PGE2 and M-CSF in vitro, all of which are implicated in bone resorption. 1,25-dihydroxy vitamin D3 (1,25D3) has a pivotal role in bone resorption. It stimulates osteoclastic bone resorption and formation, causes fusion of committed osteoclast precursor cells and activates mature osteoclasts in vitro. Under the correct conditions, macrophages (MP) have the ability to differentiate into osteoclasts. Research has shown that MP can synthesise 1,25D3 and changes in this synthesis occur during MP differentiation. We therefore examined how the application of hydrostatic pressure to MP in vitro influenced their synthesis of 1,25D3. In this study, normal human peripheral blood MP (5x105/ml) were cultured for 7 days then exposed to physiological pressure (34.5x10-3MPa) and/or UHMWPE particles (8mg/ml) and the effect on synthesis of 1,25D3 by endogenous 1a-hydroxylase (1aOHase) was studied. MP were incubated with H3-25, hydroxy vitamin D and 1,25D3 synthesis was analysed by HPLC. 1,25D3 synthesis was increased in cells under pressure by an average of 17% compared to static controls. In situ hybridisation (ISH) was used to demonstrate expression of 1aOHase. Image analysis showed a small increase in 1aOHase mRNA in response to pressure and to particles, and a larger increase to the two stimuli simultaneously. Expressed as % of maximum +Pressure + Particles 100%;+ Particles 59%; +Pressure 37%; No Stimulus < 0.1%. These results suggest that 1,25D3 may be one of the factors which stimulates osteoclastic bone resorption in aseptic loosening. As both these stimuli are likely to be present in vivo, such synthesis could further exacerbate loosening

Aims

Tissue inhibitors of metalloproteinases (TIMPs) are the endogenous inhibitors of the zinc-dependent matrix metalloproteinases (MMP) and A disintegrin and metalloproteinases (ADAM) involved in extracellular matrix modulation. The present study aims to develop the TIMPs as biologics for osteoclast-related disorders.

Aim. The aim of the study was to define the peculiarities of bone remodeling and identify specific parameters to development to heterotopic ossification. Materials and methods. Markers of bone formation (Osteocalcin, serum type 1 procollagen (N-terminal) (tP1NP)) and bone resorption (serum collagen type 1 cross-linked C-telopeptide (β-CTx)) were determined by the electrochemiluminiscence immunoassay “ECLIA” for Elecsys user cobas immunoassay analyser. In the study were included 23 patients with spinal cord injury – first group (average age 26.8 ± 3.9, duration of spinal cord injury from 3 to 12 months) and 23 healthy people's appropriate age and gender (average age 30.6 ± 6.0, years). In the first group included 11 patients with spinal cord injury with the presence of heterotopic ossification – subgroup I and 12 patients with spinal cord injury without heterotopic ossification – subgroup II. Results. The results of examination showed that patients of first group had significantly higher bone markers than control group: P1NP (256.7±48.2 ng/ml vs 49.3±5.1 ng/ml, p<0.001), serum β-CTx (1.47±0.23 ng/ml vs 0.45±0.04 ng/ml, p<0.0001), osteocalcin (52.2±9.8 ng/ml vs 24.9±2.08 ng/ml, p<0.001). There were obtained that levels of bone remodeling markers in patients with HO were significantly higher in comparison with patients without HO: P1NP (404.9±84.9 ng/ml vs 133.2±15.7 ng/ml, p<0.001), serum β-CTx (1.75±0.23 ng/ml vs 0.28±0.14 ng/ml, p<0.0001), osteocalcin (87.1±18.9 ng/ml vs 29.4±3.7 ng/ml, p<0.001). Conclusion. The bone formation and bone resorption markers in patient of first group were significantly higher than in healthy individuals of appropriate age. The rate of bone turnover markers in patient with HO was considerably higher than in patient without HO and the process of formation dominated over the resorption in patient with HO

The inflammatory cascade associated with prosthetic implant wear debris, in addition to diseases such as rheumatoid arthritis and periodontitis, it is shown to drastically influence bone turnover in the local environment. Ultimately, this leads to enhanced osteoclastic resorption and the suppression of bone formation by osteoblasts causing implant failure, joint failure, and tooth loosening in the respective conditions if untreated. Regulation of this pathogenic bone metabolism can enhance bone integrity and the treatment bone loss. The current study used novel compounds that target a group of enzymes involved with the epigenetic regulation of gene expression and protein function, histone deacetylases (HDAC), to reduce the catabolism and improve the anabolism of bone material in vitro. Human osteoclasts were differentiated from peripheral blood monocytes and cultured over a 17 day period. In separate experiments, human osteoblasts were differentiated from human mesenchymal stem cells isolated from bone chips collected during bone marrow donations, and cultured over 21 days. In these assays, cells were exposed to the key inflammatory cytokine involved with the cascade of the abovementioned conditions, tumour necrosis factor-α (TNFα), to represent an inflammatory environment in vitro. Cells were then treated with HDAC inhibitors (HDACi) that target the individual isoforms previously shown to be altered in pathological bone loss conditions, HDAC-1, −2, −5 and −7. Analysis of bone turnover through dentine resorptive measurements and bone mineral deposition analyses were used to quantify the activity of bone cells. Immunohistochemistry of tartrate resistant acid phosphatase (TRAP), WST-assay and automated cell counting was used to assess cell formation, viability and proliferation rates. Real-time quantitative PCR was conducted to identify alterations in the expression of anti- and pro-inflammatory chemokines and cytokines, osteoclastic and osteoblastic factors, in addition to multiplex assays for the quantification of cytokine/chemokine release in cell supernatant in response to HDACi treatments in the presence or absence of TNFα. TNFα stimulated robust production of pro-inflammatory cytokines and chemokines by PBMCs (IL-1β, TNFα, MCP1 and MIP-1α) both at the mRNA and protein level (p < 0 .05). HDACi that target the isoforms HDAC-1 and −2 in combination significantly suppressed the expression or production of these inflammatory factors with greater efficacy than targeting these HDAC isoforms individually. Suppression of HDAC-5 and −7 had no effect on the inflammatory cascade induced by TNFα in monocytes. During osteoclastic differentiation, TNFα stimulated the size and number of active cells, increasing the bone destruction observed on dentine slices (p < 0 .05). Targeting HDAC-1 and −2 significantly reduced bone resorption through modulation of the expression of RANKL signalling factors (NFATc1, TRAF6, CatK, TRAP, and CTR) and fusion factors (DC-STAMP and β3-integerin). Conversely, the anabolic activity of osteoblasts was preserved with HDACi targeting HDAC-5 and −7, significantly increasing their mineralising capacity in the presence of TNFαthrough enhanced RUNX2, OCN and Coll-1a expression. These results identify the therapeutic potential of HDACi through epigenetic regulation of cell activity, critical to the processes of inflammatory bone destruction

Polyethylene wear-debris induced inflammatory osteolysis is known as the main cause of aseptic loosening and long term revision total hip arthroplasty. Although recent reports suggest that antioxidant impregnated ultra-high molecular weight polyethylene (UHMWPE) wear-debris have reduce the osteolytic potential in vivo when compared to virgin UHMWPE, little is known about if and/or how PE rate of oxidation affects osteolysis in vivo. We hypothesized that oxidized UHMWPE particles would cause more inflammatory osteolysis in a murine calvarial bone model when compared to virgin UHMWPE. Male C57BL/6 eight weeks old received equal amount of particulate debris overlaying the calvarium of (n=12/group): sham treatment (no particles), 2mg (6,75×107 particles/mg) of endotoxin-free UHMWPE particles (PE) or of endotoxin-free highly oxidized-UHMWPE (OX) particles. In vivo osteolysis was assessed using high resolution micro-CT and inflammation with L-012 probe dependent luminescence. At day 10, calvarial bone was examined using high resolution micro-CT, histomorphometric, immunohistochemistry analyses and qRT-PCR to assess OPG, RANK, RANK-L, IL-10, IL-4, IL-1b and TRAP genes expression using the protocol defined by individual TaqManTM Gene Expression Assays Protocol (Applied Biosystems). In vivo inflammation was significantly higher in the OX (1.60E+06 ± 8.28E+05 photons/s/cm2) versus PE (8.48E+05 ± 3.67E+05) group (p=0.01). Although there was a statistically significant difference between sham (−0.27% ± 2.55%) and implanted (PE: −9.7% ± 1.97%, and OX: − 8.38% ± 1.98%) groups with regards to bone resorption (p=0.02), this difference was not significant between OX and PE (p = 0.14). There was no significant difference between groups regarding PCR analyses for OPG, RANK, RANK-L, IL-10, IL-4, IL-1b and TRAP (p = 0.6, 0.7, 0.1, 0.6, 0.3, 0.4, 0.7 respectively). Bone volume density was significantly decreased in PE (13.3%±1.2%) and OX (12.2%±1.2%) groups when compared to sham (15%±0.9%) (p < 0 .05). Histomorphometric analyses showed a significantly decreased Bone Thickness/Tissue Thickness ratio in the implanted group (0.41±0.01 mm and 0.43±0.01 mm) compared to sham group (0.69± 0.01) (p < 0 .001). However, there were no significant difference between OX and PE (p = 0.2). Our findings suggest that oxidized UHMWPE particles display increased inflammatory potential. Results were not significant regarding in vivo or ex vivo osteolysis. As antioxidant-diffused UHMWPE induce less inflammation activity in vivo, the mechanism by which they cause reduced osteolysis requires further investigation

Reverse shoulder arthroplasty (RSA) has an increasing effective use in the treatment of patients with a variety of diagnoses, including rotator cuff deficiency, inflammatory arthritis, or failed shoulder prostheses. Glenoid bone loss is not uncommonly encountered in these cases due to the significant wear. Severe bone loss can compromise glenoid baseplate positioning and fixation, consequently increasing the risk for early component loosening, instability, and scapular notching. To manage severe glenoid bone deficiencies, bone grafts are commonly used. Although, many studies report outcome of bone grafting in revision RSA, the literature on humeral head autograft for glenoid bone loss in primary RSA is less robust. The purpose of this study is to evaluate the clinical and radiographic outcomes of primary RSA with humeral head autograft for glenoid bone loss at our institution. Institutional review board approval was obtained to retrospectively review the records of 22 consecutive primary RTSA surgeries in 21 patients with humeral head autograft for glenoid bone loss between January 2008 and December 2016. Five patients died during follow-up, three were unable to be contacted and one refused to participate, leaving a final study cohort of 12 patients with 13 shoulders that underwent RSA. All patients had a clinical evaluation including detailed ROM and clinical evaluation using the American Shoulder and Elbow Surgeons (ASES) Score, Constant Score, Western Ontario Osteoarthritis of the Shoulder Index (WOOS), and Short Form-12 (SF-12) questionnaires. Preoperative and postoperative plain radiographs and CT scans were assessed for component position, loosening, scapular notching, as well as graft incorporation, resorption, or collapse. There were 6 males and 6 females, with an average age of 74 ± 6.8 years. The average BMI was 31.7 ± 5.3, and the median ASA score was 3. Average follow-up was 3.4 ± 1.1 years. The average postoperative range of motion measurements for the operative arm are: flexion = 120 ± 37, abduction = 106 ± 23, external rotation = 14 ± 12, internal rotation at 90 degrees of abduction = 49 ± 7, external rotation at 90 degrees of abduction = 50 ± 28. Average functional scores are: ASES: 76.9 ± 19.2, WOOS: 456 ± 347, SF12 physical: 34.2 ± 8.2, SF12 mental: 54.1 ± 10.2, Constant Score: 64.6 ± 14. No evidence of hardware loosening or evidence of bone graft resorption were encountered. On CT, the average of pre operative B-angle was 79.3 ± 9.3 while the pre operative reverse shoulder angle was 101.4 ± 28. Glenoid retroversion average on CT was 13.3 ± 16.6. Post operative baseplate inclination average was 82 ± 7.4 while the baseplate version 7.8 ±10. The operative technique was able to achieve up to 30 degrees of inclination correction and up to 50 degrees of version correction. In conclusion, primary reverse shoulder arthroplasty with humeral head autograft for glenoid bone loss provides excellent ROM and functional outcomes at mid-term follow-up. This technique has a high rate of bone incorporation and small risk of bone resorption at mid term follow up

Aims

Currently, the effect of drug treatment for osteoporosis is relatively poor, and the side effects are numerous and serious. Melatonin is a potential drug to improve bone mass in postmenopausal women. Unfortunately, the mechanism by which melatonin improves bone metabolism remains unclear. The aim of this study was to further investigate the potential mechanism of melatonin in the treatment of osteoporosis.

Previous studies have described an age-dependent distortion of bone microarchitecture for α-CGRP-deficient mice (3). In addition, we observed changes in cell survival and activity of osteoblasts and osteoclasts isolated from young wildtype (WT) mice when stimulated with α-CGRP whereas loss of α-CGRP showed only little effects on bone cell metabolism of cells isolated from young α-CGRP-deficient mice. We assume that aging processes differently affect bone cell metabolism in the absence and presence of α-CGRP. To further explore this hypothesis, we investigated and compared cell metabolism of osteoblasts and bone marrow derived macrophages (BMM)/osteoclast cultures isolated from young (8–12 weeks) and old (9 month) α-CGRP-deficient mice and age matched WT controls. Isolation/differentiation of bone marrow macrophages (BMM, for 5 days) to osteoclasts and osteoblast-like cells (for 7/14/21 days) from young (8–12 weeks) and old (9 month) female α-CGRP−/− and WT control (both C57Bl/6J) mice according to established protocols. We analyzed cell migration of osteoblast-like cells out of femoral bone chips (crystal violet staining), proliferation (BrdU incorporation) and caspase 3/7-activity (apoptosis rate). Alkaline phosphatase (ALP) activity reflects osteoblast bone formation activity and counting of multinucleated (≥ 3 nuclei), TRAP (tartrate resistant acid phosphatase) stained osteoclasts reflects osteoclast differentiation capacity. We counted reduced numbers of BMM from young α-CGRP−/− mice after initial seeding compared to young WT controls but we found no differences between old α-CGRP−/− mice and age-matched controls. Total BMM number was higher in old compared to young animals. Migration of osteoblast-like cells out of bone chips was comparable in both, young and old α-CGRP−/− and WT mice, but number of osteoblast-like cells was lower in old compared to young animals. Proliferation of old α-CGRP−/− BMM was higher when compared to age-matched WT whereas proliferation of old α-CGRP−/− osteoblasts after 21 days of osteogenic differentiation was lower. No differences in bone cell proliferation was detected between young α-CGRP−/− and age-machted WT mice. Caspase 3/7 activity of bone cells from young as well as old α-CGRP−/− mice was comparable to age-matched controls. Number of TRAP-positive multinucleated osteoclasts from young α-CGRP−/− mice was by trend higher compared to age-matched WT whereas no difference was observed in osteoclast cultures from old α-CGRP−/− mice and old WT. ALP activity, as a marker for bone formation activity, was comparable in young WT and α-CGRP−/− osteoblasts throughout all time points whereas ALP activity was strongly reduced in old α-CGRP−/− osteoblasts after 21 days of osteogenic differentiation compared to age-matched WT. Our data indicate that loss of α-CGRP results in a reduction of bone formation rate in older individuals caused by lower proliferation and reduced activity of osteogenic cells but has no profound effects on bone resorption rate. We suggest that the osteopenic bone phenotype described in aged α-CGRP-deficient mice could be due to an increase of dysfunctional matured osteoblasts during aging resulting in impaired bone formation

This study examined the regional variations of cortical and cancellous bone density present in superiorly eroded glenoids. It is hypothesized that eroded regions will contain denser bone in response to localized stress. The shift in natural joint articulation may also cause bone resorption in areas opposite the erosion site. Clinical CT scans were obtained for 32 shoulders (10m/22f, mean age 72.9yrs, 56–88yrs) classified as having E2-type glenoid erosion. The glenoid was divided into four measurement regions - anterior, inferior, posterior, and superior - as well as five depth regions. Depth regions were segmented in two-millimeter increments from zero to 10 millimeters, beginning at the center of the glenoid surface. A repeated-measures multiple analysis of variance (RM-MANOVA) was performed using SPSS statistical software to look for differences and interactions between mean densities in each depth, quadrant, and between genders. A second RM-MANOVA was performed to examine effects of gender and quadrant on cortical to cancellous bone volume ratios. Significance was set at p < 0 .05. Quadrant and depth variables showed significant multivariate main effects (p 0.147 respectively). Quadrant, depth, and their interaction showed significant univariate main effects for cortical bone (p≤0.001) and cancellous bone (p < 0 .001). The lowest bone density was found to be in the inferior quadrant for cancellous bone (307±50 HU, p < 0 .001). The superior quadrant contained the highest mean density for cortical bone (895±97 HU), however it was only significantly different than in the posterior quadrant (865±97 HU, p=0.022). As for depth, it was found that cortical bone is most dense at the glenoid surface (zero to two millimeters, 892±91 HU) when compared to bone at two to eight millimeters in depth (p < 0 .02). Cancellous bone was also most dense at the surface (352±51 HU), but only compared to the eight to 10 millimeters depth (p=0.005). Cancellous bone density was found to decrease with increasing depth. For cortical-to-cancellous bone volume ratios, the inferior quadrant (0.37±0.28) had a significantly lower ratio than all other quadrants (p < 0 .001). The superoposterior region of the glenoid was found to have denser cancellous bone and a high ratio of cortical to cancellous bone, likely due to decreased formation of cancellous bone and increased formation of cortical bone, in response to localized stresses. The inferior quadrant was found to have the least dense cortical and cancellous bone, and the lowest volume of cortical bone relative to cancellous bone. Once again, this is likely due to reduction in microstrain responsible for bone adaptation via Wolff's law. The density values found in this study generally agree with the range of values found in previous studies of normal and arthritic glenoids. An important limitation of this study is the sizing of measurement regions. For a patient with a smaller glenoid, a depth measurement of two millimeters may represent a larger portion of the overall glenoid vault. Segments could be scaled for each patient based on a percentage of each individual's glenoid size

Aim: A study to compare bone remodeling (BMD changes) around the femoral component of a cemented and uncemented THR using DXA scan and Finite element analysis and to check the predictive value of remodelling simulations as a pre-clinical implant testing tool. Methods: Twenty patients were recruited, ten for each implant type (Exeter and ABG-II). All volunteers underwent unilateral hip replacement. No patient had any metabolic bone disease or were on medication that would alter BMD. Each patient had a preopera-tive CT scan of the hip, in order to provide 3D bone shape and density data needed to construct a computer model. Each patient’s changes of BMD over a period of 12 months postoperatively were evaluated in a series of 4 follow-up DXA scans taken at 3 weeks, 3, 6 and 12 months post-op. For the computer simulation, Finite Element (FE) models of the affected femur were constructed for each patient and BMD changes predicted using strain adaptive bone remodelling theory. These patients were clinical followed up to access the hip scores (Merle d’Aubigne Postel). Results: All the patients were Charnely group A and had excellent postoperative hip scores (average pain 5.5, walking 5.4 and range of motion 5.3) The Exeter stem DXA results show bone resorption in Gruen zone 3 (2.8% on average) and 4 (3.3%) whereas there is a tendency for bone deposition at regions 1, 6 and 7 (2% on average). The ABG-II stem results show bone resorption developing at regions 7 and 4 (6% and 2% respectively) and some bone formation at region 6 (2%). The simulation results have a tendency to overestimate amounts of bone resorption (20% at region 7 for the ABG-II, 12% at region 3 for the Exeter). Conclusion: A comparison of the remodelling around a cemented and a non-cemented hip implant show important differences in the emerging patterns of adaptation. To our knowledge, very few published studies provide information on bone remodelling around cemented stems, and compare the results to those of an uncemented stem. Additionally, the simulation results suggest that these formulations can reproduce realistic patterns of bone adaptation. This study aims at providing the means for comparison and subsequent improvement of the accuracy of the simulations and thus helps develop a hip prosthesis that would led to least bone resorption

Biomechanical interpretations of bone adaptation in biological reconstructions following bone tumors would be crucial for orthopedic oncologists, particularly if based on quantitative observations. This would help to plan for surgical treatments, rehabilitative programs and communication with the patients. In particular, outcomes of the Capanna technique, which combines bone allograft and vascularized fibula autograft, lead to stable and durable reconstructions [1, 2], and different remodeling patterns have been described [3] as a response to mechanical loading. However, there are several events that are not understood and require a biomechanical interpretation, as the evolution patterns can evolve towards conditions that threaten the strength of the reconstruction. We aimed to (i) analyze the biomechanical adaptation of a femoral reconstruction after Ewing sarcoma, in terms of morphological and densitometric evolution of bone from CT data, internal loads acting on the bone during movement, mechanical competence of the reconstruction, and (ii) relate in-progress bone resorption to the mechanical stimulus induced by different motor activities. Eight CT datasets of a patient (8 yrs at surgery using the Capanna technique) during 76-month follow-up were available. The evolution of bone morphology, density and moments of inertia was quantified. At the last control, the patient underwent gait analysis (walking, chair rise/sit, stair ascent/descent, squat). We created a multiscale musculoskeletal and finite element model from CT scans and motion analysis data at the end of follow-up, using state-of-the-art modeling workflows [4, 5], to analyze muscle and joint loads, and to compare the mechanical competence of the reconstructed bone with the contralateral limb, in the current real condition and in a possible revision surgery that removed proximal screws. Although there were no reconstruction complications and osteo-fusion with intense remodeling between allograft and autograft was shown, there was a progressive decrease in allograft cortical thickness and density. There were strategies of muscle coordination that led to differences in joint loads between limbs more marked in more demanding motor activities, and generally larger in the contralateral limb. The operated femur presented a markedly low ratio of physiological strain due to load-sharing with the metal implant, particularly in the lateral aspect. A possible revision surgery removing the three most proximal screws would help restore a physiological strain configuration, while the safety of the reconstruction would not be threatened. We suggest that bone resorption is related to load-sharing and to the internal forces exerted during movement, and the mechanical stimulus should be improved by adopting modifications in the surgical treatment and by promoting physical therapy aimed at specific muscle strengthening

Introduction: Activated matrix metalloproteinases (MMPs) are responsible for the osteolytic process in aseptic loosening. Fluvastatin has been shown in previous studies to inhibit MMPs. The purpose of this study was to investigate the potential pharmacological effect of fluvastatin on aseptic loosening. Materials and methods: A radiolabelled mouse calvaria and human interface membrane cells culture system was used to study the effect of fluvastatin on bone resorption induced by interface membrane cells. The experimental conditions were: 1) test culture consisted of culturing a dead radiolabelled bone disc with cells from human interface membrane in culture medium containing fluvastatin for 14 days 2) control culture consisted of similar culture system without fluvastatin and 3) baseline control culture consisted of bone disc only. The bone discs from each test and control groups comparison were from the same parietal bone to ensure equal amount of radioactive calcium in the bone discs at the start of the experiment. Supernatant were sampled on day 7, 10 & 14 for scintillation counting. The total Ca. 45. remained in the bone discs at the completion of the culture were measured by scintillation counting. Eight sets of experiments were performed in this study. The results were expressed as the ratio of Ca. 45. in the fluvastatin exposed culture over culture containing bone disc only. In the control, the results were expressed as ratio of bone disc exposed to cells over culture containing bone disc only. Results: In the supernatant Ca. 45. , both the fluvastatin and control ratios increased with time confirming bone resorption in both culture. The fluvastatin culture consistently showed a lower ratio compared with control indicating an inhibitory effect. In the fluvastatin culture the mean ratios on day 7, 10 & 14 were 0.79, 1.53 and 2.55. The mean ratios in the control culture were 1.03, 1.81 and 3.20 (n = 8, p = 0.0001 ANOVA, General Linear Model). The mean ratio of total Ca. 45. remaining in the bone disc in the fluvastatin culture was 0.87 and the control was 0.70 (p = 0.01, t test). This implies 55% less bone resorption in the presence of fluvastatin. Conclusions: In this in vitro study we found fluvastatin has the ability to inhibit osteolysis by cells from interface membrane of aseptically loosened hips. We believe fluvastatin inhibit bone resorption by MMPs inhibition. This may have therapeutic implication in the treatment of patients with aseptic loosening of total joint replacements

Osteoarthritis (OA) is a chronic degenerative joint disease characterized by progressive cartilage degradation, synovial membrane inflammation, osteophyte formation, and subchondral bone sclerosis. Pathological changes in cartilage and subchondral bone are the main processes in OA. In recent decades, many studies have demonstrated that activin-like kinase 3 (ALK3), a bone morphogenetic protein receptor, is essential for cartilage formation, osteogenesis, and postnatal skeletal development. Although the role of bone morphogenetic protein (BMP) signalling in articular cartilage and bone has been extensively studied, many new discoveries have been made in recent years around ALK3 targets in articular cartilage, subchondral bone, and the interaction between the two, broadening the original knowledge of the relationship between ALK3 and OA. In this review, we focus on the roles of ALK3 in OA, including cartilage and subchondral bone and related cells. It may be helpful to seek more efficient drugs or treatments for OA based on ALK3 signalling in future.

Osteoarthritis (OA) is a highly prevalent degenerative joint disorder characterized by joint pain and physical disability. Aberrant subchondral bone induces pathological changes and is a major source of pain in OA. In the subchondral bone, which is highly innervated, nerves have dual roles in pain sensation and bone homeostasis regulation. The interaction between peripheral nerves and target cells in the subchondral bone, and the interplay between the sensory and sympathetic nervous systems, allow peripheral nerves to regulate subchondral bone homeostasis. Alterations in peripheral innervation and local transmitters are closely related to changes in nociception and subchondral bone homeostasis, and affect the progression of OA. Recent literature has substantially expanded our understanding of the physiological and pathological distribution and function of specific subtypes of neurones in bone. This review summarizes the types and distribution of nerves detected in the tibial subchondral bone, their cellular and molecular interactions with bone cells that regulate subchondral bone homeostasis, and their role in OA pain. A comprehensive understanding and further investigation of the functions of peripheral innervation in the subchondral bone will help to develop novel therapeutic approaches to effectively prevent OA, and alleviate OA pain.

Cite this article: Bone Joint Res 2022;11(7):439–452.

1. In growing rats oestrogen, cortisone and thyroxine in high doses suppress bone formation, and this effect is probably part of a general suppression of body growth. 2. Growth hormone and thyroxine in small doses stimulate both body growth and bone formation. 3. Testosterone has no effect on bone formation. 4. Oestrogen and cortisone suppress bone resorption. The effect of cortisone may be modified in conditions of calcium depletion. 5. Thyroxine appears on the other hand to increase bone resorption. 6. Testosterone has no effect on bone resorption

Multiple myeloma (MM) is an incurable hematological tumor stemming from malignant plasma cells. MM cells accumulate in the bone marrow (BM) and shape the BM niche by establishing complex interactions with normal BM cells, boosting osteoclasts (OCLs) differentiation and causing bone disease. This unbalance in bone resorption promotes tumor survival and the development of drug resistance. The communication between tumor cells and stromal cells may be mediated by: 1) direct cell-cell contact; 2) secretion of soluble factors, i.e. chemokines and growth factors; 3) release of extracellular vesicles/exosomes (EVs) which are able to deliver mRNAs, miRNAs, proteins and metabolites in different body district. Primary CD138+ MM cells were isolated from patients BM aspirates. MM cell lines were cultured alone in complete RPMI-1640 medium or co-cultured with murine (NIH3T3) or human (HS5) BMSC cell lines or murine Raw264.7 monocytes in DMEM medium supplemented with 10% V/V FBS. Silencing of Jagged1 and Jagged2 was obtained by transient expression of specific siRNAs or by lentiviral transduction using a Dox-inducible system (pTRIPZ). EVs were isolated using differential ultracentrifugation. EVs concentration and size were analyzed using Nano Track Analysis (NTA) system. The uptake of PKH26-labelled MM-derived EVs by HS5 or Raw264.7 was measured after 48 hours by confocal microscopy and flow cytometry. Osteoclast (OCL) differentiation of Raw264.7 cells was induced by 50ng/ml mRANKL, co-culturing with MM cells, CM or EVs. OCLs were stained by TRAP Kit and counted. Bone resorption was assessed by Osteo Assay Surface plates. Flow cytometric detection of apoptotic cells was performed after staining with Annexin V. Gene expression was analyzed by qRT-PCR, while protein levels were determined using flow cytometry ELISA or WB. Notch oncogenic signaling is dysregulated in several hematological and solid malignancies. Notch receptors and ligands are key players in the crosstalk between tumor cells and BM cells. We have demonstrated that: 1) the dysregulated Jagged ligands on MM cells trigger the activation of Notch receptors in the nearby stromal cells by cell-cell contact. This results in the release of anti-apoptotic and growth stimulating factors, i.e. IL6 and SDF1; 2) MM cells promote the development of bone lesions boosting osteoclast differentiation by secreting soluble factors (i.e. RANKL) and by the activation of Notch signaling mediated by direct contact with osteoclast precursors; 3) Finally, we present evidences that EVs play a crucial role in the dysregulated interactions of MM cells with the microenvironment and that Notch signaling regulates their release and participate in this cross-talk. These evidences supports the hypothesis that Jagged targeting on MM cells may interrupt the communication between tumor cells and the surrounding milieu, blocking the activation of the oncogenic Notch pathway and finally resulting in the a reduction of MM-associated bone disease and drug resistance

Aseptic loosening of total joint arthroplasty is characterised by osteolysis that is caused by osteoclasts and macrophages. The mechanism of bone resorption is by acidification, dissolution of hydroxyapatite crystals then proteolysis of the bone collagen matrix. The collagen cross-link molecules are cleaved by osteoclasts exposing the N terminal of the cross-link protein - N Telo-peptides (NTx). This represents a highly specific marker for bone resorption. Previously described bone resorption models include radiolabelled animal bones which require the use of animals and radioactive materials or thin dentine slice resorption pits which are only semi-quantitative and technically difficult to produce. NTx could be a potential osteolysis marker in the laboratory investigation of aseptic loosening with the advantage of being cheaper and easier to perform compared to present established marker and also does not require animals or radioactive materials. The aim of this study was to show that NTx generated during osteolysis by cells extracted from human interface membranes of aseptically loosened hips correlates with the established radiolabelled . 45. Ca bone resorption model. Cells from human interface membranes of aseptic loosened hip joints were extracted from the tissue following enzyme digestion. These cells were cultured with dead radiolabelled (. 45. Ca) mice calvaria discs in the presence of 1,25 dihydroxyvitamin D. 3. , hydrocortisone, RANKL and M-CSF. In the control culture no cells were added to the culture system. Calvaria discs used for each experiment comparison were from the same parietal bone. The supernatant culture medium were extracted on day 3, 7, 10 and 14 and assayed for NTx and by scintillation counting. On day 14 the remaining culture medium and cells were assayed by scintillation counting. The remaining bone samples were decalcified and the total remaining . 45. Ca in the bone was measured. All results were expressed as the ratio of bone exposed to cells (BC)/bone only (B). Supernatant samples for . 45. Ca showed a rise in BC/B ratio with time 0.83, 0.88, 0.97 and 1.08 (p= 0.0001). Supernatant samples for NTx also showed a rise with time 1.06, 1.21, 1.41 and 1.40 (p=0.03). In the bottom sampling for . 45. Ca the mean ratio of BC/B was1.8 (p=0.0001) and the BC/B ratio for the remaining radioactivity in the bone at the end of the culture was 0.81(p=0.0007). There was a strong correlation between . 45. Ca and NTx (r= 0.9). The absolute values of . 45. Ca dropped initially due to the uptake of calcium by the cells and this explains our previously unsuccessful attempt to use non radioactive calcium as a marker of bone destruction. We believe this is the first time human interface membrane cells have been shown to release NTx during osteolysis in an in vitro model. Replacing . 45. Ca radiolabelled bone with NTx as a marker represents an important step towards simplifying and reducing the cost of an in vitro model of particle induced osteolysis

This longitudinal microCT study revealed the osteolytic response to a Staphylococcus epidermidis-infected implant in vivoand also demonstrates how antibiotics and/or a low bone mass state influence the morphological changes in bone and the course of the infection. Colonisation of orthopaedic implants with Staphylococcus aureusor S. epidermidisis a major clinical concern, since infection-induced osteolysis can drastically impair implant fixation or integration within bone. High fracture incidence in post-menopausal osteoporosis patients means that this patient group are at risk of implant infection. The low bone mass in these patients may exacerbate infection-induced osteolysis, or alter antibiotic efficacy. Therefore, the aims of this study were to examine the bone changes resulting from a S. epidermidisimplant infection in vivousing microCT imaging, and to determine if a low bone mass stateinfluences the course of the infection and the efficacy of antibiotic therapy. An in vivomodel system using microCT scanning [1], involving the implantation of either a sterile or a S. epidermidis-colonised PEEK screw into the proximal tibia of 24 week-old female Wistar rats, was used to investigate the morphological changes in bone following infection over a 28 day period. In addition, the efficacy of a combination antibiotic therapy (rifampin and cefazolin: administered twice daily from days 7–21 post-screw implantation) for affecting osteolysis was also assessed. A subgroup of animals was subjected to ovariectomy (OVX) at 12 weeks of age, allowing for a 12 week period for bone loss prior to screw implantation at 24 weeks. Bone resorption and formation rates, bone-implant contact and peri-implant bone volume in the proximity of the screw were assessed by microCT scanning at days 0, 3, 6, 9, 14, 20 and 28 days post-surgery. Following euthanasia at day 28, the implanted screw, bone and soft tissues were subjected to quantitative bacteriology as a measure of the efficacy of the antibiotic regimen. In non-OVX animals S. epidermidisinfection induced marked osteolysis, which peaked between 9 and 14 days post-screw implantation. Peak bone resorption was detected at day 6, before recovering to baseline levels at day 14. Infection also resulted in extensive deposition of mineralised tissue, initially within the periosteal region (day 9–14), then subsequently in the osteolytic region at day 20–28. Quantitative bacteriology indicated all non-OVX animals remained infected. Rifampin and cefazolin successfully cleared the infection in 5/6 non-OVX animals group although there was no difference observed in CT-derived bone parameters. OVX resulted in extensive loss of trabecular bone but this did not alter the temporal pattern of infection-induced osteolysis, or mineralised tissue deposition, which was similar to that observed in the non-OVX animals. Similarly, there was no difference in bacterial counts between non-OVX and OVX animals (39,005 colony-forming units (CFU) [range: 3,675–156,800] vs 37,665 CFU [range 3,250–84,000], respectively). Interestingly, antibiotic treatment was less effective in the OVX animals (3/5 remained infected), suggesting that antibiotics have reduced efficacy in OVX animals. This study demonstrates S. epidermidis-induced osteolysis displays a similar temporal pattern in both normal and low bone mass states, with comparable bacterial loads present within the localised infection site

The stem cell fraction of a cell population is finely tuned by stimuli from the external microenvironment. Among these stimuli, a decrease of extracellular pH (pHe) may occur in a variety of physiological and pathological conditions, including hypoxia and inflammation. Also in bone, the maintenance of acid-base balance is fundamental for skeleton homeostasis. Bone cells are extremely sensitive to the effects of interstitial pH. Acidosis inhibits mineral deposition by osteoblasts and activates osteoclast-mediated bone resorption. Moreover, acidosis is associated with inflammation, and in case of bone injury, local short-term acidosis is a crucial regulator of the healing process. Evidence of the role of acidosis as an enhancer of MSC stemness and for their activation as sensors and switcher of inflammation will be discussed