Abstract. Objective. To investigate the safety and cost-effectiveness of interscalene brachial plexus block/regional anaesthesia (ISB-RA) in patients undergoing reverse total shoulder replacement. Methods. This retrospective study included 15 patients with symptomatic rotator cuff arthropathy who underwent reverse total shoulder arthroplasty (rTSA) under ISB-RA without general anaesthesia in the beach chair position from 2010 to 2018. The mean patient age was 77 years (range 59–82 years). Patients had associated medical comorbidities: American Society of Anesthesiologists (ASA) grade 2–4. Assessed parameters were: duration of anaesthesia, intra-operative systolic blood pressure variation, sedation and vasopressor use, duration of post-operative recovery, recovery scores, length of stay, and complications. A robust cost analysis was also performed. Results. The mean (range) duration of anaesthesia was 38.66 (20–60) min. Maximum and minimum intra-operative systolic blood pressure ranges were 130–210 and 75–145 mmHg, respectively (mean [range] drop, 74.13 [33–125] mmHg). Mean (range) propofol dose was 1.74 (1–3.0) mg/kg/h. The Median (interquartile range) post-operative recovery time was 30 (20–50) min. The mean (range) postoperative recovery score (local scale, range 5–28 where lower values are superior) was 5.2 (5–8). The mean (range) length of stay was 8 (1–20 days); the two included patients with ASA grade 2 were both discharged within 24 hours. One patient with predisposing history developed pneumonia; however, there were no complications related to ISB-RA. The mean (range) cost per patient was £101.36 (£59.80-£132.20). Conclusions. Our data demonstrate that rTSA under ISB-RA is safe, cost-effective and a potentially viable alternative for patients with multiple comorbidities. Notably, patients with ASA grade 2 who underwent rTSA under ISB-RA had a reduced length of stay and were discharged within 24 hours

Regional anaesthetic for foot surgery has been discussed as a method of post operative analgesia. Ankle block as the sole anaesthetic for foot surgery has not been extensively reviewed in the literature. We aimed to describe our experience of forefoot surgery under ankle block alone. 21 consecutive forefoot procedures (18 patients) were carried out under ankle block. The blocks were performed by the senior authors. A mixture of 10ml 2% Lidocaine with 10ml 0.5 % Bupivacaine was administered to the superficial peroneal, deep peroneal, sural and saphenous nerves. Ankle tourniquet was employed in all procedures. The patients were contacted post operatively and completed a standardised questionnaire including an incremented pain assessment ranging from 0-10 (0 no pain, 10 severe pain). 17 female and 1 male patients were contacted (age range 33-67y). Procedures included 13 first metatarsal osteotomies, 3 cheilectomies, 2 first MTP joint replacements, and 5 fusions. 14 patients requested a short acting sedative (midazolam). 5 patients (27 %) reported some discomfort during the block procedure (average pain score 1.2). No patients reported any pain during their operation(s). 4 patients (22%) required supplementation of the block. Average pain score at 6, 12, 24 and 48 hours following surgery were 0.66, 2.9, 2.4 and 1.3 respectively. All patients were discharged home and walking on the same day. None complained of nausea or required parenteral analgesia; there were no readmissions. Each patient confirmed they would have surgery under local block rather than general anaesthesia and would recommend this technique to family and friends. Forefoot surgery under ankle block alone is safe and effective. Anaesthesia obtained permits the majority of forefoot procedures and provides lasting post-operative analgesia. Combined with intraoperative sedation, use of ankle tourniquet and same day discharge, it has very high patient acceptance and satisfaction

Regional anaesthetic for foot surgery has been discussed as a method of post operative analgesia. Ankle block as the sole anaesthetic for foot surgery has not been extensively reviewed in the literature. We aimed to describe our experience of forefoot surgery under ankle block. Sixty-six consecutive forefoot procedures (59 patients) were carried out under ankle block. Patients were contacted post operatively and completed a standardised questionnaire including an incremental pain assessment ranging from 0-10 (0 no pain, 10 severe pain). Forty nine female and 10 male patients (age range 20-85y) were included. Procedures included 33 first metatarsal osteotomies, 15 cheilectomies, 3 first MTP joint replacements, 5 fusions, 4 excision of neuroma and 6 other procedures. 22 patients (33% of cases) reported discomfort during the block procedure (average pain score 1.5). 6 patients reported pain during their operation(s), average score 0.26. Average pain scores at 6, 12, 24 and 48 hours following surgery were 2.0, 3.2, 2.7 and 2.1 respectively. All patients were discharged home and walking on the same day. There were no readmissions. Each patient confirmed they would have surgery under regional block rather than general anaesthesia and would recommend this technique to family and friends. There are many advantages in being able to perform these relatively small procedures under regional anaesthesia. The anaesthesia obtained permits the majority of forefoot procedures and provides lasting post-operative analgesia. Combined with intra-operative sedation, use of ankle tourniquet and same day discharge; it has very high patient acceptance and satisfaction

Single shot interscalene blocks are an effective analgesic for arthroscopic shoulder surgery. However, patients receiving these blocks are often found to be in significant pain when the block wears off, usually in the late evening or early hours of the morning. Overnight admission is currently routine in our unit, to ensure adequate analgesia can be administered during this period. Recent studies have suggested that adding dexamethasone to the local anaesthetic agent can prolong the duration of the block. We carried out a prospective study to assess whether addition of dexamethasone to brachial plexus blocks could reduce patient's post-operative analgesic demands and allow safe discharge on the same day after surgery. Twenty-six patients undergoing arthroscopic shoulder surgery during a morning theatre list, had ultrasound guided brachial plexus blocks using a mixture of 0.25% bupivacaine 20–30ml with 2–3mg of dexamethasone. All were admitted to the ward afterwards for analgesia and physiotherapy. Pain numerical rating scores (0–10) were recorded at rest in recovery one hour postoperatively by the attending anaesthetist and on active movement of the shoulder joint 24 hours after surgery by the attending physiotherapist. A standardised analgesia regime was prescribed with regular and as required medication, including as required strong opiates. Mean pain scores in recovery were 0.31 and on the morning after surgery were 2.38. Sixteen out of 26 required no further analgesia, with only 3 out of the 10 who did requiring opiates. The use of dexamethasone provides adequate analgesia for a prolonged period for most patients after brachial plexus block for shoulder surgery and does not result in a significant analgesic requirement when the block wears off. This may provide support for avoiding overnight admission in selected patients after arthroscopic shoulder surgery

Our goal is to repurpose drugs to block the growth of lung metastases, the lethal process in osteosarcoma. We therefore screened the NCI-panel of 114 FDA-approved oncology drugs to identify agents that potently reduce growth of osteosarcoma spheroids (sarcospheres). We first developed a system to routinely generate large numbers of highly-uniform spherical sarcospheres (1/well) with a 400um diameter, to most closely simulate micrometatases. Our primary drug screen (Z’-factor=0.70+0.10) utilized sarcospheres from three highly-metastatic human osteosarcoma cell lines (LM7, 143B, and MG63.3) in the presence and absence of MAP chemotherapeutics. Dose-response experiments with 13 of the most effective drugs confirmed initial results and allowed comparison with each drug's toxicity on normal human osteoblasts and normal small airway epithelial cells. Romidepsin, a HDAC inhibitor (HDACi), had the most favorable toxicity/efficacy ratios (TD. 50. /IC. 50. =57–580, depending on cell line). The only other HDACi in the panel of FDA-approved drugs (vorinostat) also ranked highly in the screen. Since newer HDACi's may have improved toxicity/efficacy ratios, we compared romidepsin and vorinostat with the three other HDACi's that are FDA-approved (belinostat, panobinostat, and valproic acid) plus one that is in clinical trials (entinostat). Romidepsin (C. max. /IC. 50. =36–360) and belinostat (C. max. /IC. 50. =14–20) reduced sarcosphere growth at clinically-achievable levels, in the presence or absence of MAP. Importantly, both romidepsin and belinostat were synergistic with MAP (BLISS scores=5–15). Propidium iodide staining showed that both romidepsin and MAP substantially induced cell death throughout the sarcospheres. Our results strongly support future studies to determine effects of romidepsin and belinostat on growth of lung metastases in vivo

We have examined the deterioration of implant fixation after withdrawal of parathyroid hormone (PTH) in rats. First, the pull-out force for stainless-steel screws in the proximal tibia was measured at different times after withdrawal. The stimulatory effect of PTH on fixation was lost after 16 days. We then studied whether bisphosphonates could block this withdrawal effect. Mechanical and histomorphometric measurements were conducted for five weeks after implantation. Subcutaneous injections were given daily. Specimens treated with either PTH or saline during the first two weeks showed no difference in the mechanical or histological results (pull-out force 76 N vs 81 N; bone volume density 19% vs 20%). Treatment with PTH for two weeks followed by pamidronate almost doubled the pull-out force (152 N; p < 0.001) and the bone volume density (37%; ANOVA, p < 0.001). Pamidronate alone did not have this effect (89 N and 25%, respectively). Thus, the deterioration can be blocked by bisphosphonates. The clinical implications are discussed

More than half of patients with neck of femur (NOF) fractures report their pain as severe to very severe in the first 24hrs. Opioids remain the most commonly used analgesia and are effective for static pain but not dynamic pain. Opioids provide suboptimal analgesia when patients are in a dynamic transition state and their side-effects are a source of morbidity in these patients. The Fascia Iliaca Compartment Block (FICB) involves infiltration of the fascia iliaca compartment with a large volume of low concentrated local anaesthetic to reduce pain by affecting the femoral and lateral cutaneous nerve of the thigh. The London Quality Standards for Fractured neck of femur services (2013) stated that the FICB should be routinely offered to patients. We performed an audit of patient outcomes following the introduction of the FICB across three centres. We performed a two-cycle audit across two hospitals in 2014/15. The first cycle audited compliance with the NICE guidance in the management and documentation of pain and AMTS (Abbreviated Mental Test Scores) in patients. The second cycle was conducted following the integration of the FICB into the multidisciplinary NOF fracture protocol across three hospital sites. Data was collected on numeric pain scores, pre and post-op AMTS and opioid requirements. There were 40 patients audited with 20 in the first cycle prior to the introduction of the FICB and 20 following this. In the second cycle, there was a statistically significant improvement (p<0.001) in the difference between the pre and post-op AMTS. The preliminary findings in this audit support the use of the FICB adjunct to analgesia in the pre-operative management of NOF fracture patients. The FICB is a safe procedure and the organisational learning of this procedure through a multidisciplinary approach can significantly improve the outcomes of NOF fracture patients

Currently, fibrin glue obtained from fibrinogen and thrombin of human and animal blood are widely investigated to use as injectable hydrogel for tissue engineering which contributes to minimally invasive surgery, superior biodegradability, cell attachment, proliferation and regenerating new tissue. However, most of them fail to achieve to be used for tissue engineering application because of a risk of immune response and poor mechanical properties. To overcome the limitation of fibrin glue and to reduce the usage of products from human and animal blood, the artificial fibrin glue materials were developed. Recently, cellulose nanofiber (CNF) as reinforcing agent has been explored for many tissue engineering applications such as bone and cartilage due to its impressive biological compatibility, biodegradability and mechanical properties. CNF was extracted from cassava pulp. PEO-PPO-PEO diacrylate block copolymer is a biodegradable synthetic polymers which is water insoluble hydrogel after curing by UV light at low intensity. To enhance the cell adhesion abilities, gelatin methacrylate (GelMA), the denature form of collagen was used to incorporate into hydrogel. The aim of this study was to develop the artificial fibrin glue from CNF reinforced PEO-PPO-PEO diacrylate block copolymer/GelMA injectable hydrogel. CNF/PEO-PPO-PEO diacrylate block copolymer/GelMA injectable hydrogels were prepared with 2-hydroxy-1-(4-(hydroxy ethoxy) phenyl)-2-methyl-1-propanone (Irgacure 2959) as a photoinitiator. The physicochemical properties were investigated by measuring various properties such as thickness, gel fraction, mechanical properties and water uptake. At optimal preparation condition, CNF reinforced injectable hydrogel was successful prepared after curing with UV light within 7 minutes. This hydrogel showed gel fraction and water uptake of 81 and 85%, respectively. The cytotoxicity, cell adhesion and proliferation of CNF reinforced injectable hydrogel was presented. Cellulose nanofiber from casava pulp was successfully used to prepare injectable hydrogel as artificial fibrin glue for tissue engineering. The hydrogel showed good physical properties which can be applied to use for tissue engineering application

To ensure clinical relevance, the in vitro engineering of tissues for implantation requires artificial replacements to possess properties similar to native anatomy. Our overarching study is focussed on developing a bespoke bone-tendon in vitro model replicating the anatomy at the flexor digitorum profundus (FDP) tendon insertion site at the distal phalanx. Anatomical morphometric analysis has guided FDP tendon model design consisting of hard and soft tissue types. Here, we investigate potential materials for creation of the model's bone portion by comparison of two bone cements; brushite and genex (Biocomposites Ltd). 3D printed molds were prepared based on anatomical morphometric analysis of the FDP tendon insertion site and used to cast identical bone blocks from brushite and genex cements. Studies assessing the suitability of each cement type were conducted e.g. setting times, pH on submersion in culture medium and interaction with fibrin gels. Data was collected using qualitative imaging and qualitative measurements (N=3,n=6) for experimental conditions. Both brushite (BC) and genex (GC) cements could be cast into bespoke molds, producing individual blocks and were mixed/handled with appropriate setting times. On initial submersion in culture medium, BC caused a reduction in pH values (7.49 [control]) to 6.85) while GC remained stable (7.59). Reduction in pH value also affected fibrin gel interaction where gel was seen to be detaching/not forming around BC and medium discolouration was noted. This was not observed in GC. While GC outperformed BC in initial tests, repeated washing of BC led to pH stabilisation (7.5,3xwashes), consistent with their further use in this model. This study has compared BC and GC as materials for bone block production. Both materials show promise, and current work assessing material properties and cell proliferation are needed to inform our choice for use in our FDP-tendon-bone interface model. This research was supported by an ORUK Studentship award (ref:533). Genex was kindly provided by Biocomposites, Ltd

Osteoarthritis (OA) is the most common degenerative joint disorder. Its multifactorial etiology includes age, sex, joint overloading, genetic or nervous influences. In particular, the autonomic nervous system is increasingly gaining in importance. Its two branches, the sympathetic (SNS) and parasympathetic nervous system, are well-balanced under healthy conditions. OA patients seem to be prone to an autonomic imbalance and therefore, we analyzed their autonomic status. More than 200 participants including patients with early and late stage knee OA (before and 1 year after knee replacement surgery) and healthy probands (age-matched) were analyzed. Heart rate variability was measured via electrocardiogram to assess long-term sympathetic (low-frequency=LF) and parasympathetic (high-frequency=HF, pRR50) activities or general variability (RMSSD, SDRR). Serum cortisol concentrations were measured by ELISA. Perceived chronic stress (PSQ) was assessed via questionnaire. Multivariant regression was performed for data analysis. LF/HF value of early OA was slightly increased compared to healthy controls but significantly higher compared to late OA patients before (p>0.05) and after TKR (p>0.01). HF in late OA patients before TKR was significantly decreased compared to patients after TKR (p>0.001) or healthy controls (p>0.05). Healthy probands exhibited the highest SDRR values, early OA patients had slightly lower levels and late OA patients before TKR displayed significantly reduced SDRR (p>0.001). The same differences were observed in pRR50 and RMSSD. Serum cortisol concentrations and PSQ scores increased in late OA patients before TKR. At the time point of TKR, women with beta blocker medication had significantly higher age (71 ± 9 years) than those without (63 ± 12 years)(p>0.01). An autonomic dysfunction with sympathetic dominance occurs in OA patients. The fact that beta blocker medication in women delayed the need of TKR indicates that SNS inhibition might counteract OA. Future therapeutic interventions for OA should consider a systemic approach with special regard on the ANS

Bottom-up tissue engineering (TE) strategies employing microscale living materials as building blocks provide a promising avenue for generating intricate 3D constructs resembling native tissues. These microtissue units exhibit high cell densities and a diverse extracellular matrix (ECM) composition, enhancing their biological relevance. By thoughtfully integrating different cell types, the establishment of vital cell-cell and cell-matrix interactions can be promoted, enabling the recreation of biomimetic micro-niches and the replication of complex morphogenetic processes. Notably, by co-assembling blood vessel-forming endothelial cells with supportive stromal cells, microtissues with stable capillary beds, referred to as vascular units (VUs), can be generated. Through a modular TE approach, these VUs can be further combined with other microtissues and biomaterials to construct large-scale vascularized tissues from the bottom up. Integration of VUs with technologies such as 3D bioprinting and microfluidics allows for the creation of structurally intricate and perfusable constructs. In this presentation, we will showcase examples of VUs and explore their applications in regenerative medicine and tissue modeling. Acknowledgements: This work was supported by project EndoSWITCH (PTDC/BTM-ORG/5154/2020) funded by FCT (Portuguese Foundation for Science and Technology)

Regenerative medicine (RM) promises to restore both the mechanical functionality and the biological composition of tissues after damage. Three-dimensional scaffolds are used in RM to host cells and let them produce proteins that are the building blocks of the native tissues. While regenerating tissues evolve over time through dynamic biomechanical and biochemical changes, current scaffolds’ generation are passive causing mechanical mismatch, suboptimal growth, and pain. Furthermore, current scaffolds ignore the complexity of the reciprocal bio-mechanics regulation, hindering the design of the next-gen scaffolds. To regenerate tissues and organs, biofabrication strategies that impart spatiotemporal control over cell-cell and cell-extracellular matrix communication, often through control over cell and material deposition and placement, are being developed. To achieve these targets, the spatiotemporal control over biological signals at the interface between cells and materials is often aimed for. Alternatively, biological activity can be triggered through the control of mechanical cues, harnessing more fundamental know-how in mechanobiology that could be combined with biofabrication strategies. Here, I present some of our most recent advancements in merging mechanobiology with biofabrication that enabled the control of cell activity, moving towards enhanced tissue regeneration as well as the possibility to create more complex 3D in vitro models to study biological processes

Recently, technologies to culture one or more cell types in three dimensions have attracted a great deal of attention in tissue engineering. Particularly, the improved viability, self-renewal capacity, and differentiation potential have been reported for stem cell spheroids. However, it is crucial to modulate spheroid functions with instructive signals to use multi-cellular spheroids in tissue engineering. We have been developing ECM-mimicking fibrous materials decorated with cell-instructive cues, which were incorporated within 3D stem cell spheroids to fine-tune their functions as modular building blocks for bottom-up tissue-engineering applications. In particular, we created composite spheroids of human adipose-derived stem cells (hADSCs) incorporating nanofibers coated with instructive signal of either transforming growth factor-β3 or bone morphogenetic growth factor-2 for chondrogenesis or osteogenesis of stem cells, respectively. The bilayer structure of osteochondral tissue was subsequently mimicked by cultivating each type of spheroid inside 3D-printed construct. The in vitro chondrogenic or osteogenic differentiation of hADSCs within the biphasic construct under general media was locally regulated by each inductive component. More importantly, hADSCs from each spheroid proliferated and sprouted to form the integrated tissue with interface of bone and cartilage tissue. This approach may be applied to engineer complex tissue with hierarchically organized structure

Critical size bone defects are frequently caused by accidental trauma, oncologic surgery, and infection. Distraction osteogenesis (DO) is a useful technique to promote the repair of critical size bone defects. However, DO is usually a lengthy treatment, therefore accompanied with increased risks of complications such as infections and delayed union. Herein, we developed an innovative intramedullary biodegradable magnesium (Mg) nail to accelerate bone regeneration in critical size bone defect repair during DO. We observed that Mg nail induced almost 4-fold increase of new bone formation and over 5-fold of new vessel formation at 2 weeks after distraction. Mg nail upregulated the expression of calcitonin gene-related peptide (CGRP) in the new bone as compared with the DO alone group. We further revealed that blockade of the sensory nerve by overdose capsaicin blunted Mg nail enhanced critical size bone defect repair during the DO process. Moreover, inhibitors/antagonist of CGRP receptor, FAK, and VEGF receptor blocked the Mg nail stimulated vessel and bone formation. In summary, we revealed, for the first time, a CGRP-FAK-VEGF signaling axis linking sensory nerve and endothelial cells, which may be the main mechanism underlying Mg-enhanced critical size bone defect repair when combined with DO, suggesting a great potential of Mg implants in reducing DO treatment time for clinical applications

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

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

Serial section electron microscopy (SSEM) was initially developed to map the neural connections in the brain. SSEM eventually led to the term ‘Connectomics’ to be coined to describe process of following a cell or structure through a volume of tissue. This permits the true three-dimensionality to be appreciated and relationships between cells and structures. The purpose of this study was to utilize this methodology to interrogate S. aureus infected bone. Bone samples were harvested from mice tibia infected with S. aureus and were fixed, decalcified, and osmicated. The samples were paraffin embedded and 5-micron sections were cut to identify regions of bacterial invasion into the osteocyte-lacuna-canalicular-network (OLCN). This area was cut from the paraffin block, deparaffinized, post-fixed and reprocessed into epoxy resin. Serial sections were cut at 60nm and collected onto Kapton tape utilizing the Automated Tape-collecting Ultramicrotome (ATUMtome) system. Samples were mounted onto 4” silicon wafers and post-stained with 2% uranyl acetate followed by 0.3% lead citrate and carbon coated. A ZEISS GeminiSEM 450 scanning electron microscope fitted with an electron backscatter diffusion detector was used to image the sections. The image stack was aligned and segmented using the open-source software, VASTlite. 264 serial sections were imaged, representing approximately 40 × 45 × 15-micron (x, y, z) volume of tissue. 70% of the canaliculi demonstrated infiltration by S. aureus. This study demonstrates that SSEM can be applied to the skeletal system and provide a new solution to investigate the OLCN system. It is feasible that this methodology could be implemented to investigate why some canaliculi are resistant to colonization and potentially opens up a new direction for the prevention of chronic osteomyelitis. In order to make this a realistic target, automated segmentation methodologies utilizing machine learning must be developed and applied to the bone tissue datasets

Digital Ventilated Cages (DVC) offer an innovative technology to obtain accurate movement data from a single mouse over time [1]. Thus, they could be used to determine the occurrence of a tendon damage event as well as inform on tissue regeneration [2,3]. Therefore, using the mouse model of tendon experimental damage, in this study it has been tested whether the recovery of tissue microarchitecture and of extracellular matrix (ECM) correlates with the motion data collected through this technology. Mice models were used to induce acute injury in Achilles tendons (ATs), while healthy ones were used as control. During the healing process, the mice were housed in DVC cages (Tecniplast) to monitor animal welfare and to study biomechanics assessing movement activity, an indicator of the recovery of tendon tissue functionality. After 28 days, the AT were harvested and assessed for their histological and immunohistochemical properties to obtain a total histological score (TSH) that was then correlated to the movement data. DVC cages showed the capacity to distinguish activity patterns in groups from the two different conditions. The data collected showed that the mice with access to the mouse wheel had a higher activity as compared to the blocked wheel group, which suggests that the extra movement during tendon healing improved motion ability. The histological results showed a clear difference between different analyzed groups. The bilateral free wheel group showed the best histological recovery, offering the highest TSH score, thus confirming the results of the DVC cages and the correlation between movement activity and structural recovery. Data obtained showed a correlation between TSH and the DVC cages, displaying structural and movement differences between the tested groups. This successful correlation allows the usage of DVC type cages as a non-invasive method to predict tissue regeneration and recovery. Acknowledgements: This research is part of the P4FIT project ESR13, funded by the H2020-ITN-EJD MSCA grant agreement No.955685

Tibial periprosthetic fracture is an important complication of the Oxford Unicompartmental Knee Replacement (OUKR). Primary fixation of cementless OUKR tibial components relies on the interference-fit of the ‘keel’ and a slot in the proximal tibia. Clinically used double blade keel saws (DKS) create slots with two grooves, generating stress concentrations where fractures may initiate. This study aimed to investigate slot factors that may influence incidence of tibial periprosthetic fractures. Slots were made in PCF20 polyurethane foam using the DKS plus/minus adjuvant rasping, single blade keel saw (SKS), and rasp-only. Round and square slots were machined with milling cutters. Compact tensile tests were conducted per ASTM E399 to determine tensile load to fracture (TLTF) and results were validated using bovine tibia. Cementless OUKR components were implanted into slots in custom polyurethane blocks and compressed to failure to determine anatomical load to fracture (ALTF). A custom MATLAB program calculated slot roundness from cross-sectional images. Round slots had higher TLTF (29.5N, SD=2.7) than square (25.2N, SD=1.7, p<0.05) and DKS slots (23.3N, SD=2.7, p<0.0001). Fractures occurred at the round slot apices, square slot corners, and deepest DKS slot grooves. ALTF was not significantly different between square and round slots. Adjuvant rasping made DKS slots significantly rounder, resulting in significantly higher TLTF, but rasping did not increase ALTF. ALTF was significantly higher for SKS (850N, SD=133, p<0.01) and rasp-only (912N, SD=100, p<0.001) slots compared to standard DKS slots (703N, SD=81). Round keel slots minimise stress concentrations and increase TLTF but do not increase ALTF. The SKS and rasp-only slots retain material at slot ends and have significantly higher ALTF. Future studies should assess saw blades that retain material and round slot ends to evaluate if their use may significantly reduce the incidence of tibial periprosthetic fracture

Extracellular matrix (ECM) mechanical cues guide healing in tendons. Yet, the molecular mechanisms orchestrating the healing processes remain elusive. Appropriate tissue tension is essential for tendon homeostasis and tissue health. By mapping the attainment of tensional homeostasis, we aim to understand how ECM tension regulates healing. We hypothesize that diseased tendon returns to homeostasis only after the cells reach a mechanically gated exit from wound healing. We engineered a 3D mechano-culture system to create tendon-like constructs by embedding patient-derived tendon cells into a collagen I hydrogel. Casting the hydrogel between posts anchored in silicone allowed adjusting the post stiffness. Under this static mechanical stimulation, cells remodel the (unorganized) collagen representing wound healing mechanisms. We quantified tissue-level forces using post deflection measurements. Secreted ECM was visualized by metabolic labelling with non-canonical amino acids, click chemistry and confocal microscopy. We blocked cell-mediated actin-myosin contractility using a ROCK inhibitor (Y27632) to explore the involvement of the Rho/ROCK pathway in tension regulation. Tissue tension forces reached the same homeostatic level at day 21 independent of post compliance (p = 0.9456). While minimal matrix was synthesized in early phases of tissue formation (d3-d5), cell-deposited ECM was present in later stages (d7-d9). More ECM was deposited by tendon constructs cultured on compliant (1Nm) compared to rigid posts (p = 0.0017). Matrix synthesized by constructs cultured on compliant posts was less aligned (greater fiber dispersion, p = 0.0021). ROCK inhibition significantly decreased tissue-level tensional forces (p < 0.0001). Our results indicate that tendon cells balance matrix remodeling and synthesis during tissue repair to reach an intrinsically defined “mechanostat setpoint” guiding tension-mediated exit from wound healing towards homeostasis. We are identifying specific molecular mechanosensors governing tension-regulated healing in tendon and investigate the Rho/ROCK system as their possible downstream pathway