Purpose of the study: Platelet rich fibrin (PRF) favours proliferation of tenocytes and synthesis of extracellular matrix. The purpose of this study was to demonstrate the technical feasibility of adding a PRF envelope during arthroscopic rotator cuff repair to favour short-term vascularisation of the tendon-trochiter zone vascularization. Material and method: Twenty patients aged over 55 years with a posterosuperior rotator cuff tear were included in this prospective randomized controlled study. The double strand technique was used for all patients. Patients were selected at random for insertion of a PRF envelope between the tendon and the trochiter. There were thus two groups of ten patients. The SSV, SST, VAS and Constant scores were noted. Vascularization was assessed with Power Doppler ultrasound at 6 weeks and 3 months by an independent operator unaware of the study group. Results: There were no complications during or after the operations. Postoperatively, all patients increased their SSV, SST, VAS and Constant scores significantly. Vascularization of the tendon-trochiter zone, as assessed by Power Doppler, was significantly higher in the PRF group at 6 weeks. It was unchanged in the two groups at 3 months. Discussion: Arthroscopic rotator cuff repair with adjunction of a PRF envelope is technically feasible and increases vascularizaton of the tendon-trochiter zone at 6 weeks. Conclusion: PRF can improve the tendon healing rate for rotator cuff tears

Aims. Alcoholism is a well-known detrimental factor in fracture healing. However, the underlying mechanism of alcohol-inhibited fracture healing remains poorly understood. Methods. MicroRNA (miR) sequencing was performed on bone mesenchymal stem cells (BMSCs). The effects of alcohol and miR-19a-3p on vascularization and osteogenic differentiation were analyzed in vitro using BMSCs and human umbilical vein endothelial cells (HUVECs). An in vivo alcohol-fed mouse model of femur fracture healing was also established, and radiological and histomorphometric analyses were used to evaluate the role of miR-19a-3p. The binding of miR-19a-3p to forkhead box F2 (FOXF2) was analyzed using a luciferase reporter assay. Results. miR-19a-3p was identified as one of the key regulators in the osteogenic differentiation of BMSCs, and was found to be downregulated in the alcohol-fed mouse model of fracture healing. In vitro, miR-19a-3p expression was downregulated after ethanol administration in both BMSCs and HUVECs. Vascularization and osteogenic differentiation were independently suppressed by ethanol and reversed by miR-19a-3p. In addition, the luciferase reporter assay showed that FOXF2 is the direct binding target of miR-19a-3p. In vivo, miR-19a-3p agomir stimulated callus transformation and improved the alcohol-impaired fracture healing. Conclusion. This study is the first to demonstrate that the miR-19a-3p/FOXF2 axis has a pivotal role in alcohol-impaired fracture healing, and may be a potential therapeutic target. Cite this article: Bone Joint Res 2022;11(6):386–397

Topographic anatomy and general distribution of LFCA is well described in anatomy textbooks. Its contribution to the vascularization of specific anatomic structures in the hip region is poorly defined. The purpose of this study was to demonstrate the importance of LFCA in hip circulation, especially in the vascularization of hip abductors.

The LFCA was specifically studied in 30 hips from 26 fresh cadavers after injection of common iliac artery or aorta with colored silicone for a more extensive hip vascular study. 24 hours after intra-arterial setting of silicone, dissection was performed through the anterior iliofemoral approach to expose the artery and its branches from the origin to the terminal distribution.

In all specimens, the ascending branch of the LFCA was found as consistent supplier of gluteus minimus, gluteus medius, and tensor fasciae latae muscles by a variable number of branches. The proximal part of the abductor muscles was mainly supplied by the superior gluteal artery. We conclude, that ligating the ascending branch of the LFCA during anterior approach to the hip joint is likely to affect the vascularity and function of the abductor muscles especially in situations when perfusion of these muscles by the superior gluteal artery is compromised.

Purpose of the study: During resurfacing arthroplasty, excessive valgus of the femoral neck or an insufficient surgical technique can lead to formation of a notch in the femoral head. Although the mechanisms weakening the femoral neck and subsequent fractures are well described, the effects of altered blood supply via the retinacular vessels on potential ischemia of the femoral head are largely unknown. The purpose of our study was to assess blood supply to the femoral head when a notch occurred in the femoral neck during total hip replacement surgery and to deduct possible implications concerning the resurfacing procedure.

Material and methods: Blood supply to the femoral head was measured with laser Doppler fluorometry in 14 hips undergoing total hip replacement for osteoarthritis via a lateral approach with anterior dislocation. An optical laser probe for the fluorometry (Moor Instruments, Wilmington Delewar, 20 mW laser, probe length 780 nm) was introduced via a 3.5 mm hole drilled in the antrolaeral quadrant of the femoral head (leg in neutral position). The position of the probe was checked on the x-ray of the femoral head after resection. A notch was simulated in the lateral posterior portion of the femoral neck using a bone gouge.

Results: Mean patient age was 65 years (range 48–77 years). There were eight men and six women. Two measurements were made: one after dislocation of the hip and the second after simulating the notch. A significant decrease in blood supply measured at more than 50% was observed in all but four hips after simulating the notch. The median decrease in blood flow was 76% (4.4–90.4, p< 0.001).

Conclusion: The retinacular vessels appear to be equally important for the blood supply for osteoarthritic and non-osteoarthritic femoral heads. A notch occurring during hip resurfacing would not only weaken the mechanical resistance of the neck but would also increase the risk of osteonecrosis and subsequent loosening of the femoral component. Consequently, approaches compromising retinacular blood supply (for example the posterior approach) would add a supplementary danger for the integrity and viability of the femoral head.

Sufficient vascularization is essential for osseointegration of biomaterials and their substitution by new bone. Angiogenic growth factors such as VEGF are promising agents to promote the vascularization of bone substitutes. To optimize the efficacy of VEGF delivery a continuous administration of low concentrations of VEGF seems to be beneficial. We hypothesized that a long-term release of VEGF from calcium phosphate ceramics may induce a sustained angiogenic response and sufficiently promote biomaterial vascularization in vivo.

Vascular endothelial growth factor (VEGF, Genentech Inc., South San Francisco, USA.) was co-precipitated onto biphasic calcium phosphate ceramics (BCP, 80% HA, 20% β-TCP) at a concentration of 1μg/ml and 5μg/ml. The passive release and the cell-mediated release of VEGF were analyzed over 19 days by ELISA. For in vivo investigations BCP ceramics were implanted into a cranial window preparation in Balb/c mice. Angiogenesis and vascularization were investigated over 28 days by means of intravital microscopy. Functional capillary density (FCD, mm/mm²) served as parameter of biomaterial vascularization.

Co-precipitation of VEGF onto BCP ceramics resulted in a significant improvement of protein retention as compared to conventional adsorption of the growth factor [Cumulative VEGF release: Adsorption: 320 ± 2.6 ng/ml, Co-precipitation 116 ± 14.6 ng/ml (p< 0.05)]. Murine bone marrow cells differentiated towards osteoclasts mediated a sustained release of co-precipitated VEGF. Preliminary in vivo results showed a significant increase of functional capillary density after implantation of BCP ceramics co-precipitated with VEGF as compared to negative controls [day 7: 1.7 ± 0.2 mm/mm² vs. 0.9 ± 0.5 mm/mm²; day 14: 6.1 ± 0.3 mm/mm² vs. 2.1 ± 0.6 mm/mm²; day 28: 8.7 ± 0.3 mm/mm² vs. 3.9 ± 0.7 mm/mm², p< 0.05]. At 14 and 28 days after implantation, FCD induced by BCP ceramics co-precipitated with VEGF was significantly higher as compared to FCD induced by ceramics adsorbed with the VEGF [day 14: 6.1 ± 0.3 mm/mm² vs. 4.0 ± 1.4 mm/mm²; day 28: 8.7 ± 0.3 mm/mm² vs. 5.9 ± 0.7 mm/mm², p< 0.05].

The release kinetics critically influences the efficacy and the risks of local VEGF administration. By applying a co-precipitation technique the initial high liberation rate of VEGF was reduced and a sustained cell-mediated release at low concentrations was achieved. In vivo, VEGF promoted angiogenesis and vascularization of BCP ceramics. Vessel formation was more pronounced if VEGF was co-precipitated onto ceramics as compared to superficial adsorption of the growth factor, indicating that VEGF delivery at later stages of the healing process is beneficial. The present study provides evidence that, by delivering VEGF in a sustained manner at low local concentrations biomaterial vascularization can be markedly enhanced.

Aims: Aims of this study was to perform a quantitatively evaluation of newly formed bone, vascular density (VD) and their correlation in animal model of posterolateral spinal fusion based on skeletal stem cells (SSCs) combined with a coral.

Methods: 15 rabbits received cell-material constructs, 15 rabbits were sham-operated (decortication of transverse apophyses), 15 rabbits received material alone. After 6 months the animals were sacrified. We performed a semi-quantitative and quantitative histologycal analysis of the fusion mass. To assess the VD, sections of the fusion mass were immunolabelled for alpha-smooth muscle actin as a vascular marker.

Results: No complete fusion was observed in all groups and no bone was formed in the interapophyseal region. Aboundant newly formed bone was observed in the peri-apophyseal regions in 60% of cases. The quantitative analysis showed a significantly higher amount of bone and VD in animals treated with cells and/or biomaterial alone compared to sham (p< 0.05). Periapophyseal VD and new bone formation was significantly higher compared to interapophyseal region in all groups (p< 0.05). Positive correlation exist between newly formed bone and vascolar density (p = 0,0009).

Conclusions: Interapophyseal region is scarcely vascolarized. The study shows a positive correlation between VD and osteogenesis. The inadequacy of staminal cells could be related with the poor survival after the implant. For the use of stam cells in the APL are necessary more studies in order to clarify the survival and in situ differentiation of the grafted cells in short and mid term.

Introduction. The objective of the work is construction of a multi-bioactive scaffold based on that allows a space/time control over the regeneration of damaged bones by Medication-Related Osteonecrosis of the Jaw using a minimal invasive approach based on the injection of the fast-degrading pro neuro and angiogenic ELR (Elastin-Like Recombinamers) based hydrogels. Method. Chemical crosslinking facilitated the creation of multi-bioactive scaffolds using ELRs with reactive groups. Cell-loaded multi-bioactive scaffolds, prepared and incubated, underwent evaluation for adhesion, proliferation, angiogenic, and neurogenic potential. In vitro assessments utilized immunofluorescence staining and ELISA assays, while live-recorded monitoring and live-dead analysis ensured cytocompatibility. In rat and rabbit models, preformed scaffolds were subcutaneously implanted, and the regenerative process was evaluated over time. Rabbit models with MRONJ underwent traditional or percutaneous implantation, with histological evaluation following established bone histological techniques. Result. A 3D scaffold using ELR that combines various peptides with different degradation rates to guide both angiogenesis and neurogenesis has been developed. Notably, scaffolds with different degradation rates promoted distinct patterns of vascularization and innervation, facilitating integration with host tissue. This work demonstrates the potential for tailored tissue engineering, where the scaffold's bioactivities and degradation rates can control angiogenesis and neurogenesis. In an animal model of medication-related osteonecrosis of the jaw (MRONJ), the scaffold showed promising results in promoting bone regeneration in a necrotic environment, as confirmed by histological and imaging analyses. This study opens avenues for novel tissue-engineering strategies where precise control over vascularization and nerve growth is crucial. Conclusion. A groundbreaking dual approach, simultaneously targeting angiogenesis and innervation, addresses the necrotic bone in MRONJ syndrome. Vascularization and nerve formation play pivotal roles in driving reparative elements for bone regeneration. The scaffold achieves effective time/space control over necrotic bone regeneration. The authors are grateful for funding from the Spanish Government (PID2020-118669RA-I00)

INTRODUCTION. Stimulation of angiogenesis via the delivery of growth factors (GFs) like vascular endothelial growth factor (VEGF) is a promising strategy for the treatment of avascular necrosis (AVN). Tyraminated poly-vinyl-alcohol hydrogels (PVA-Tyr), which have the ability to covalently incorporate GFs, were proposed as a platform for the controlled delivery of therapeutic levels VEGF to the necrotic areas[1]. Nevertheless, PVA hydrophilicity and bioinertness limits its integration with the host tissues. The aim of this study was to investigated the effectiveness of incorporating gelatin, an FDA-approved, non-immunogeneic biomaterial with biological recognition sites, as a strategy to facilitate blood vessels invasion of PVA-Tyr hydrogels and to restore the vascular supply to necrotic tissues. METHODS. Progressively higher gelatin concentrations (0.01–5wt%) were incorporated in the PVA-Tyr network. Hydrogel physico-chemical properties and endothelial cell attachment were evaluated. Afterwards, the capability of the released VEGF and gelatin to promote vascularization was evaluated via chorioallantoic membrane (CAM) assay. VEGF-loaded PVA-Tyr hydrogels with or without gelatin (n=7) were implanted in a subcutaneous mouse model for 3 weeks. Vascularization (CD31+ cells) and cell infiltration (H&E) were evaluated. Finally, AVN was induced in 6 weeks old male piglets as previously described [2]. A transphyseal hole (3mm) was drilled and PVA-Tyr hydrogels with 1% gelatin were delivered in the defects. Piglets were euthanized after 4 weeks and microCT analysis was performed. RESULTS. The incorporation of 1% gelatin significantly enhanced cell attachment without compromising hydrogels physical properties, degradation time, VEGF retention and release. Thus, this gelatin concentration was selected for further analysis. Additionally, the covalent incorporation of VEGF or gelatin to the PVA-Tyr network does not hamper their bioactivity, as both still promoted neo-angiogenesis in a CAM assay. Following subcutaneous implantation, the presence of gelatin did not increase the cellular infiltration in the PVA-Tyr hydrogels. Nevertheless, higher vascular infiltration was observed in the groups where either gelatin or VEGF were included. Additionally, preliminary microCT results indicated that the delivery of PVA-Tyr hydrogels containing 1% gelatin in an AVN model was effective in preventing the necrosis-associated resorption of the bone. DISCUSSION & CONCLUSIONS. These results indicated that the presence of either gelatin or VEGF was sufficient to promote vascular infiltration. Additionally, preliminary results suggested the suitability of the developed hydrogels to treat AVN

Aims

Adenosine, lidocaine, and Mg²⁺ (ALM) therapy exerts differential immuno-inflammatory responses in males and females early after anterior cruciate ligament (ACL) reconstruction (ACLR). Our aim was to investigate sex-specific effects of ALM therapy on joint tissue repair and recovery 28 days after surgery.

Periprosthetic osteolysis has attracted attention as a cause of loosening after arthroplasty. The aim of the present study was to examine inflammatory cell localization and the occurrence of apoptosis in granulation tissue from patients who required revision arthroplasty due to loosening caused by osteolysis. 7 patients were studied comprising 3 patients who underwent FHR and 4 patients who underwent THR. Their mean age at the time of surgery was 63.6 years. The mean period from their previous operation to revision was 8.8 years. Granulation tissue was collected from around the loosened implant fixed in 4% paraformaldehyde and embedded in paraffin. Sections were cut and were first stained with hematoxylin and eosin. Next, immunohistochemical studies were performed using the avidin-biotin complex method. CD45 was used as the primary antibody to detect T cells, and CD68 was used to detect macrophage-like cells. The activity of the macrophage-like cells was assessed with anti-I-NOS and anti-MMP-9. Apoptosis was investigated using anti-single-stranded DNA (ssDNA). Using another granulation tissue was stored at −80%C, DNA was extracted, and the presence of DNA fragmentation was detected by agarose gel electrophoresis. Vascularization and infiltration by a large number of inflammatory cells were seen along with large multinucleated osteoclas-like cells. Immunohistochemical studies revealed CD45-positive cells primarily around the blood vessels. The CD68-positive cells were mainly multinucleated cells. The multinucleated cells were i-NOS-positive in 4 patients, and were MMP-9-positive in 5 patients. The nuclei of many of the multinucleated cells were positive for ssDNA. Agarose gel electrophoresis of DNA showed a marked ladder pattern at the 170 base pair region. This finding indicated DNA fragmentation or apoptosis. Apoptotic cells were seen in granulation tissue harvested from around loosened implants suggesting that apoptosis may play a role in the pathophysiology of osteolysis

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.

As our understanding of hip function and disease improves, it is evident that the acetabular fossa has received little attention, despite it comprising over half of the acetabulum’s surface area and showing the first signs of degeneration. The fossa’s function is expected to be more than augmenting static stability with the ligamentum teres and being a templating landmark in arthroplasty. Indeed, the fossa, which is almost mature at 16 weeks of intrauterine development, plays a key role in hip development, enabling its nutrition through vascularization and synovial fluid, as well as the influx of chondrogenic stem/progenitor cells that build articular cartilage. The pulvinar, a fibrofatty tissue in the fossa, has the same developmental origin as the synovium and articular cartilage and is a biologically active area. Its unique anatomy allows for homogeneous distribution of the axial loads into the joint. It is composed of intra-articular adipose tissue (IAAT), which has adipocytes, fibroblasts, leucocytes, and abundant mast cells, which participate in the inflammatory cascade after an insult to the joint. Hence, the fossa and pulvinar should be considered in decision-making and surgical outcomes in hip preservation surgery, not only for their size, shape, and extent, but also for their biological capacity as a source of cytokines, immune cells, and chondrogenic stem cells.

Cite this article: Bone Joint Res 2020;9(12):857–869.

Despite its intrinsic ability to regenerate form and function after injury, bone tissue can be challenged by a multitude of pathological conditions. While innovative approaches have helped to unravel the cascades of bone healing, this knowledge has so far not improved the clinical outcomes of bone defect treatment. Recent findings have allowed us to gain in-depth knowledge about the physiological conditions and biological principles of bone regeneration. Now it is time to transfer the lessons learned from bone healing to the challenging scenarios in defects and employ innovative technologies to enable biomaterial-based strategies for bone defect healing. This review aims to provide an overview on endogenous cascades of bone material formation and how these are transferred to new perspectives in biomaterial-driven approaches in bone regeneration.

Cite this article: T. Winkler, F. A. Sass, G. N. Duda, K. Schmidt-Bleek. A review of biomaterials in bone defect healing, remaining shortcomings and future opportunities for bone tissue engineering: The unsolved challenge. Bone Joint Res 2018;7:232–243. DOI: 10.1302/2046-3758.73.BJR-2017-0270.R1.