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BackgroundDecellularized allograft tendons are highly regarded for their accessibility and the reduced risk of immune rejection, making them a promising choice for grafting due to their favorable characteristics. However, effectively integrating reconstructed tendons with host bone remains a significant clinical challenge.PurposeThis study aims to investigate the relationship between the duration of tendon exposure to trypsin and its impact on tendon biomechanical properties and healing capacity.MethodsMorphological assessments and biochemical quantifications were conducted. Allograft tendons underwent heterotopic transplantation into the anterior cruciate ligament (ACL) in a rabbit model, with specimens harvested 6 weeks post-surgery for a comparative analysis of cell adhesion strength and mechanical performance. Duration-response curves were constructed using maximum stress and cell adhesion quantity as primary indicators.ResultsThe trypsin treatment enhanced cell adhesion on the tendon surface. Adhesion rates in the control group vs. the experimental groups were as follows: 3.10 ± 0.56% vs. 4.59 ± 1.51%, 5.36 ± 1.24%, 6.12 ± 1.98%, and 8.27 ± 2.34% (F = 6.755, p = 0.001). However, increasing treatment duration led to a decline in mechanical properties, with the ultimate load (N) in the control vs. experimental groups reported as 103.30 ± 10.51 vs. 99.59 ± 4.37, 93.15 ± 12.38, 90.42 ± 7.87, and 82.68 ± 6.89, F = 4.125 (p = 0.013).ConclusionThe findings reveal an increasing trend in adhesion effectiveness with prolonged exposure duration, while mechanical strength declines. The selection of the optimal processing duration should involve careful consideration of the benefits derived from both outcomes.

Abstract Background Skier’s thumb is a type of injury to the ulnar collateral ligament of the metacarpophalangeal joint of the thumb, which can result in bone fragmentation and joint instability. Objective The objective of this study was to compare the traditional Kirschner wire fixation method with the U-shaped Kirschner wire method for treating small bone fragments with displacement, rotation, or instability in skier’s fractures. Method A retrospective study was conducted on 30 patients with skier’s thumb who were treated at Tianjin Hospital from January 2019 to December 2021. Patients were divided into two groups: Group A received traditional Kirschner wire fixation, while Group B received U-shaped Kirschner wire fixation. Functional assessments and complications during the perioperative period were evaluated. Results Both surgical methods significantly reduced postoperative pain and increased joint range of motion. Group B had a lower incidence of pain during follow-up and showed significant functional improvement in Tip-pinch and Grip tests compared to Group A. U-shaped Kirschner wire fixation significantly reduced complications during the perioperative period. Conclusion The U-shaped Kirschner wire internal fixation is a safe and effective treatment for the thumb proximal phalanx base ulnar side avulsion fracture.

ObjectiveTo compare the clinical outcomes of microwave-assisted intralesional curettage(MAIC) with those of en bloc resection and autogenous fibular reconstruction (EBR-AFR) for treating grade III giant cell tumor of the bone (GCTB) of the distal radius and to elucidate the indications for wrist preservation surgery.Materials and methodsIn this retrospective study, 19 patients with grade III GCTB of the distal radius who underwent surgery at three medical institutions were included and categorized based on their surgical pattern. Seven patients underwent MAIC and internal fixation with bone cement (MAIC group) and 12 underwent EBR-AFR (EBR-AFR group). To evaluate the function of the affected limb postoperatively, wrist range of motion, grip strength, Musculoskeletal Tumor Society (MSTS) scores were recorded.ResultsThe follow-up time of the MAIC group was 73.57 ± 28.61 (36–116) months, with no recurrence or lung metastasis. In contrast, the follow-up time of the EBR-AFR group was 55.67 ± 28.74 (36–132) months, with 1 case of local recurrence (8.3%, 1/12) and 1 case of lung metastasis (8.3%, 1/12). The wrist flexion, extension, supination, pronation, grip strength were better in the MAIC group than in the EBR-AFR group. Although there was no statistically significant difference in the MSTS score between the two groups, it is noteworthy that the MAIC group exhibited significantly superior emotional acceptance and hand positioning compared to the EBR-AFR group(p < 0.05).ConclusionThe functional outcomes of the MAIC group are better. The treatment strategy for grade III GCTB of the distal radius should be determined based on the specific preoperative imaging findings. Nevertheless, MAIC can be the preferred surgical approach for most patients with grade III GCTB of the distal radius, particularly for young patients.

Epigenomic imbalance drives abnormal transcriptional processes, promoting the onset and progression of cancer. Although defective gene regulation generally affects carcinogenesis and tumor suppression networks, tumor immunogenicity and immune cells involved in antitumor responses may also be affected by epigenomic changes, which may have significant implications for the development and application of epigenetic therapy, cancer immunotherapy, and their combinations. Herein, we focus on the impact of epigenetic regulation on tumor immune cell function and the role of key abnormal epigenetic processes, DNA methylation, histone post-translational modification, and chromatin structure in tumor immunogenicity, and introduce these epigenetic research methods. We emphasize the value of small-molecule inhibitors of epigenetic modulators in enhancing antitumor immune responses and discuss the challenges of developing treatment plans that combine epigenetic therapy and immunotherapy through the complex interaction between cancer epigenetics and cancer immunology.

Objectives Previous studies on the mechanism and scope of interosseous membrane injury in Maisonneuve fractures have been inconsistent. In order to better guide clinical treatment, the characteristics and mechanism of interosseous membrane injuries and proximal 1/3 fibular fracture in typical Maisonneuve fracture were investigated. Methods The study comprised 15 patients between January 2019 and June 2021 with Maisonneuve fracture. All patients received X‐ray and MRI examination of the calf and ankle joint, and CT scanning of the ankle joint. The injuries of medial structure, inferior tibiofibular syndesmosis, fibula, posterior malleolus, and interosseous membrane were evaluated. Results MR images of the calf showed that the injury of interosseous membrane (IOM) was from the syndesmosis to the proximal fibular fracture site in two patients, with a range of 32.3 and 29.8 cm, respectively. In the other 13 patients, the IOM rupture was not only confined to the distal third of the calf, but also close to the fibula fracture, and the IOM was intact between the two fracture sites. The range of distal IOM rupture was 3.7–12.2 cm, with an average of 8.06 ± 2.35 cm. The proximal IOM was completely ruptured from the fibular side at the site of the fibular fracture and the range was 4.1–9.1 (average: 6.75 ± 1.64) cm. The average length of the integrate middle segment of the IOM was 14.55 ± 4.11 (5.6–20.3) cm. MR images of the calf also showed partial rupture of the posterior tibial muscle at the ending point on the fibula in 15 cases, partial rupture of soleus muscle and flexor hallucis longus in seven cases. Conclusions The rupture of the IOM was caused by a combination of abduction and external rotation violence. It was manifested in two forms, most of which was not only distal end but also near fibular fracture site ruptures with the middle part intact, and a few were ruptures of the IOM from the ankle to the near fibular fracture site. The tibialis posterior muscle may be related to the location of the fibular fracture.

Abstract Objective The aims of this work are to present a classification of “complex fracture” and “simple fracture”, to compare their features, treatments and prognosis in patients with giant cell tumour with pathologic fractures around the knee, and to determine the best surgical method for patients who have giant cell tumour around the knee with different degrees of fracture. Methods Data from 130 patients with pathologic fractures from giant cell tumour around the knee who underwent surgical treatment from March 2000 to November 2015 at 6 institutes around China were collected and analysed. A multicentric study design was used to explore the epidemiological features and to compare differences in the surgical procedures and prognosis of the two fracture groups. The mean age at diagnosis was 37.1 years old (range, 13-77 years). The median follow-up was 126.5 months, ranging from 68 to 370 months. Results The general clinical and imaging features of the groups of patients with simple and complex fractures, namely, sex, age, the lesion site, living or working environment, eccentric growth patterns, Campanacci grading system, and duration of symptoms before treatment, showed varying degrees of differences, but with no statistical significance (p > 0.05). The incidence rate of surrounding soft tissue mass was 35.2% (32/91) in the group with simple fractures, whereas it was 87.2% (34/39) in the group with complex fractures, which showed a significant difference (p

Objective To compare the biomechanical properties of percutaneous cement discoplasty (PCD) in the spinal column between different implant‐endplate friction. Methods A validated L3‐Scarumfinite element (FE) model was modified for simulation. In the PCD model, the L4/5 level was modified based on model 1 (M1) and model 2 (M2). In M1, the interaction between bone cement and endplate was defined as face‐to‐face contact with a friction coefficient of 0.3; in M2, the contact was defined as a Tie constraint. 7.5 N m moments of four physiological motions and axial load of 15, 100 and 400 N preload were imposed at the top of L3. The range of motion (ROM) and interface stress analysis of endplates, annulus fibrosus and bone cement of the operated level were calculated for comparisons among the three models. Results The ROM of M1 and M2 increased when compared with the intact model during flexion (FL) (17.5% vs 10.0%), extension (EX) (8.8% vs −8.8%), left bending (LB) (19.0% vs −17.2%) and left axial rotation (LR) (34.6% vs −3.8%). The stress of annulus fibrosus in M1 and M2 decreased in FL (−48.4% vs −57.5%), EX (−25.7% vs −14.7%), LB (−47.5% vs −52.4%), LR (−61.4% vs −68.7%) and axis loading of 100 N (−41.5% vs −15.3%), and 400 N (−27.9% vs −27.3%). The stress of upper endplate of M1 and M2 increased in FL (24.6% vs 24.7%), LB (82.2% vs 89.5%), LR (119% vs 62.4%) and axis loading of 100 N (64.6% vs 45.5%), and 400 N (58.2% vs 24.3%), but was similar in EX (2.9% vs 0.3%). The stress of lower endplate of M1 and M2 increased in FL (170.9% vs 175.0%), EX (180.8% vs 207.7%), LB (302.6% vs 274.7%), LR (332.4% vs 132.8%) and axis loading of 100 N (350.7% vs 168.6%), and 400 N (165.2% vs 106.7%). Conclusion Percutaneous cement discoplasty procedure could make effect on the mobility or stiffness. The fusion of bone cement and endplate might have more biomechanical advantages, including of the decreasing rate of implant subsidence and dislocation, and the increase spine stability.

Abstract Objective The purpose of this study was to investigate the incidence, location, and related factors of deep venous thrombosis (DVT) of the bilateral lower extremities after intertrochanteric fractures in the elderly. Methods Retrospective analysis was performed on the elderly patients with intertrochanteric fracture who were admitted from January 2017 to December 2019. At admission, patients receive routine ultrasound Doppler scanning of bilateral lower extremities to detect DVT; those with DVT were assigned to the case group and those without DVT to the control group. Patient data on demographics, comorbidities, injury-related data, and laboratory test results at admission were extracted. Logistic regression analyses were conducted to identify the independent risk factors associated with DVT. Results Five hundred seventy-eight patients were included, among whom 116 (20.1%) had DVT. Among those with DV, 70.7% (82/116) had DVT of the distal type, 24 (29.6%) had DVT of the proximal type, and 10 (10.4%) had mixed DVT. In 76.7% (89/116) of patients, DVT occurred in the fractured extremity, 9.5% (11/116) in the bilateral and 13.8% (16/116) in the non-fractured extremity. Multivariate analyses identified obesity, delay to admission, increased D-dimer level (> 1.44 mg/L) and reduced albumin (< 31.7 g/L) as independent factors. Conclusions Admission incidence of DVT was high in elderly patients with intertrochanteric fractures, especially the proximal DVT. Identification of associated risk factors is useful for individualized assessment risk of DVT and early targeted interventions.

Background: The joint with hip dysplasia is more likely to develop osteoarthritis because of the higher contact pressure, especially in the socket. The lateral center-edge angle (LCEA) is the major indicator for hip dysplasia via radiography. However, the pathological conditions of LCEA angles in the range of 18°–25° are still controversial, which challenges precise diagnosis and treatment decision-making.Objective: The purpose of this study is to investigate the influence of anterior center-edge angle (ACEA) on the mechanical stress distribution of the hip joint, via finite element analysis, to provide insights into the severity of the borderline development dysplasia.Methods: From 2017 to 2019, there were 116 patients with borderline developmental dysplasia of the hip (BDDH) enrolled in this research. Based on the inclusion criteria, nine patients were involved and categorized into three LCEA groups with the maximal ACEA differences. Patient-specific hip joint models were reconstructed from computed tomography scans, and the cartilages, including the labrum, were established via a modified numerical method. The finite element analysis was conducted to compare the stress distributions due to the different ACEA.Results: As ACEA decreased, the maximum stress of the acetabulum increased, and the high stress area developed toward the edge. Quantitative analysis showed that in the cases with lower ACEA, the area ratio of high stress increased, and the contact facies lunata area significantly affected the stress distribution.Conclusion: For patients with BDDH, both the ACEA and the area of facies lunata played essential roles in determining the severity of hip dysplasia and the mechanical mechanism preceding osteoarthritis.

Microwave ablation has been used to treat bone tumors in extremities for more than 30 years. With improved recognition, updated microwave equipment, and expanded clinical application, microwave ablation has recently been widely used to treat bone tumors. To standardize the application of microwave ablation in the clinical treatment of bone tumors in the limbs, research results and clinical experience involving the use of microwave ablation to treat bone tumors in the limbs have been summarized, and a clinical guideline has been designed. This guideline is aimed at providing a reliable clinical basis for indications, preoperative evaluation and decision‐making, perioperative treatment, complications, and other issues via evidence‐based medicine. Two aspects are considered—percutaneous microwave ablation and intraoperative microwave ablation of bone tumors in extremities. Ultimately, the guideline is intended to standardize treatment and improve the clinical efficacy of microwave ablation of bone tumors in extremities.

Osteosarcoma is a malignant bone tumor, and clinically detectable metastases can be detected in ~ 15–20% of patients when they seek medical advice; patients with metastatic disease have extremely poor prognosis. Here, we examined the involvement of the microRNA miR‐505 in osteosarcoma. Eighty‐four patients seeking treatment for osteosarcoma were included in the study group (SG), and 63 healthy subjects were allocated to the control group (CG). Normal human bone cells MG‐63 and U20S cells were transfected with miR‐505 mimics, miR‐NC, HMGB1 RNA for targeted inhibition (si‐HMGB1), and si‐NC to examine the effects on HMGB1 expression. Cell proliferation, invasion, and apoptosis were measured using CCK‐8, scratch assays, and flow cytometry (FCM), respectively, and the relationship between miR‐505 and HMGB1 was determined using the dual‐luciferase reporter assay. In patient tissues and serum, miR‐505 was expressed at a low level, and HMGB1 was expressed at a high level, with an area under curve of > 0.9. Furthermore, the expression of miR‐505 and HMGB1 in tissues had a positive association with that in the serum, whereas the expression of miR‐505 had a negative association with that of HMGB1 in tissues only. Overexpression of miR‐505 and silencing of HMGB1 suppressed the proliferation, migration, and invasion of osteosarcoma cells and increased the rate of apoptosis, whereas the co‐transfected miR‐505 mimics + si‐HMGB1 demonstrated a more significant inhibitory effect on the proliferation and invasion of osteosarcoma cells and a higher apoptosis rate. miR‐505 may inhibit the proliferation and invasion and promote apoptosis of osteosarcoma cells by targeting and suppressing HMGB1.

Objective To explore the effect of kartogenin (KGN) on proliferation and chondrogenic differentiation of human umbilical cord mesenchymal stem cells (hUCMSC) in vitro, and the synergistic effects of KGN and transforming growth factor (TGF)‐β3 on hUCMSC. Methods Human umbilical cord mesenchymal stem cells were isolated and cultured. Then the differentiation properties were identified by flow cytometry analysis. HUCMSC were divided into four groups: control group, KGN group, TGF‐β3 group, and TK group (with TGF‐β3 and KGN added into the medium simultaneously). Cells in all groups were induced for 21 days using the suspension ball culture method. Hematoxylin and eosin, immunofluorescence, and Alcian blue staining were used to analyze chondrogenic differentiation. Real‐time reverse transcriptase polymerase chain reaction was performed to investigate genes associated with chondrogenic differentiation. Result Hematoxylin and eosin staining showed that cells in the TGF‐β3 group and the TK group had formed cartilage‐like tissue after 21 days of culture. The results of immunofluorescence and Alcian blue staining showed that compared with the control group, cells in the KGN and TGF‐β3 groups demonstrated increased secretion of aggrecan after 21 days of culture. In addition, cells in the group combining KGN with TGF‐β3 (5.587 ± 0.27, P

The morphological characteristics of tendons have been thoroughly evaluated via microscopy. Optical microscopy and electron microscopy are the most commonly used techniques for tendon tissue observation. According to the principles of both microscopy types, preparation and evaluation methods vary. Simple optical microscopy is commonly used in the observation of cells and extracellular matrix, and many stains, including hematoxylin–eosin, Van Gieson, Prussian blue, Alcian blue, and toluidine blue, are used for evaluating cells, collagen fiber arrangement, and noncollagenous proteins. Histological scoring systems have been used in many studies for semi‐quantification. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) are the most commonly used electron microscopy types, and special consideration is needed for the fixation and embedding protocols. Glutaraldehyde followed by osmium is most commonly used in the chemical fixation of tendon tissue, followed by epoxy resin embedment. Longitudinal sections captured in SEM images show the arrangement of collagen fibrils and the cells and lipid drops among them, while cross sections captured in TEM images show the diameter and distribution of collagen fibrils. SEM and TEM are used together for comprehensive evaluations. This mini review is focused on the preparation methodology and related evaluation indexes for the morphological evaluation of tendons.

Abstract While osteoarthritis is a common degenerative disease, ankle osteoarthritis is a subdivision that has received little attention. Two effective ways to treat osteoarthritis of the ankle are total ankle replacement (TAR) and ankle arthrodesis (AAD). Whether TAR or AAD is more beneficial for treatment is controversial. The purpose of this meta‐analysis was to compare the efficiency (clinical outcome and patient satisfaction) and safety (complications and survival) of these two procedures. The Preferred Reporting Items for Systematic Reviews and Meta‐Analyses (PRISMA) statement was performed as a guideline for this study. Three electronic databases, PubMed, Web of Science, and Cochrane Library, were searched up to May 2019, with no language restrictions. Prospective or retrospective comparative studies were identified. The outcomes included clinical outcome, patient satisfaction, complications, and survival. Review Manager (Revman) 5.3 software was used to conduct the data analysis. We only selected literature from the past 5 years (no earlier than 2015). Seven comparative studies were included. There were six cohort studies and one cross‐sectional study. The Newcastle–Ottawa Scale (NOS) was used to assess the quality of cohort studies, and The Agency for Healthcare Research and Quality (AHRQ) checklist was chosen to assess the quality of cross‐sectional studies. No significant difference was observed for efficiency and safety. Clinical outcome was included in five studies with four different scoring systems. Two of them used the American Orthopaedic Foot & Ankle Society (AOFAS) questionnaire scores to assess the two procedures (mean difference, −4.26; 95% confidence interval [CI], −11.37–2.85; P = 0.24; I2 = 1%). Patient satisfaction (risk ratio [RR], 0.96; 95% CI, 0.65–1.40; P = 0.82; I2 = 54%), complications (RR, 1.15; 95% CI, 0.16–8.21; P = 0.89; I2 = 84%), and survival (RR, 1.91; 95% CI, 0.33–11.08; P = 0.47; I2 = 90%) showed no significant difference between the TAR group and the AAD group. This meta‐analysis showed no statistically significant difference between TAR and AAD in clinical outcome, patient satisfaction, complications, and survival. This revealed that TAR and AAD could appear to have similar results in these aspects. Therefore, the present results are not sufficient to conclude which of these two methods is better. Further studies are needed to obtain more clues.

Objective This study was performed to explore the relationship between various clinical factors and the prognosis of limb osteosarcoma. Methods We retrospectively analyzed the clinical data of 336 patients with limb osteosarcoma treated from June 2000 to August 2016 at 7 Chinese cancer centers. Data on the patients’ clinical condition, treatment method, complications, recurrences, metastasis, and prognosis were collected and analyzed. Kaplan–Meier analysis and Cox regression models were used to analyze the data. Results The patients comprised 204 males and 132 females ranging in age from 6 to 74 years (average, 21.1 years). The overall 3- and 5-year survival rates were 65.0% and 55.0%, respectively. The 5-year overall survival rate was 64.0% with standard chemotherapy and 45.6% with non-standard chemotherapy. Cox regression analysis demonstrated that standard chemotherapy, surgery, recurrence, and metastasis were independent factors associated with the prognosis of limb osteosarcoma. Conclusion The survival of patients with limb osteosarcoma can be significantly improved by combining standard chemotherapy and surgery. The overall survival rate can also be improved by adding methotrexate to doxorubicin–cisplatin–ifosfamide triple chemotherapy.

Abstract Giant cell tumors of the distal radius are challenging for surgeons because they are associated with high recurrence rates and poor functional outcomes. Between June 2005 and October 2015, patients with primary giant cell tumors of the distal radius were recruited from seven orthopedic centers in China. The patients’ clinical features and demographic characteristics were obtained from medical records and reviewed retrospectively. Overall, 48 cases of giant cell tumors of the distal radius were assessed in this study. These patients were more likely to be between 20 and 40 years of age, to have a Campanacci grade of III, and to undergo a surgical style of resection. The prevalence of pathological fractures was 12.5% overall (20.0% in men and 4.3% in women). The prevalence of local recurrence was 30.0% overall (38.1% in men and 21.1% in women) during the average follow-up period of 62.5 months, with a pulmonary metastasis rate of 5.0%. Giant cell tumors of the distal radius were predominant in men and were more likely to recur locally than around the knee. These findings suggest that it is crucial to evaluate the optimal surgical approach for balancing local recurrence control and functional outcomes to reduce the disease burden.

Emerging literature indicates the essential roles of long noncoding RNA (lncRNA) in the osteosarcoma (OS). However, the regulatory function and mechanism of FOXD2-AS1 in the OS is still elusive. In present research, the level of FOXD2-AS1 was significantly up-regulated in the OS tissue and cell lines compared to corresponding controls. The aberrant high-expression of FOXD2-AS1 indicated the poor clinical prognosis of OS patients. Transcription factor HIF-1α could bind with the promoter region of FOXD2-AS1 to activate the transcription in OS cells. Functionally, the knockdown of FOXD2-AS1 could repress the malignant biological properties of OS cells in vitro and vivo, including proliferation, invasion, apoptosis and tumor growth. Mechanistically, FOXD2-AS1 inhibited the expression of p21 via interacting with EZH2 to silence p21 gene expression. Overall, we conclude that FOXD2-AS1, induced by transcription factor HIF-1α, acts as an oncogene in the OS tumorigenesis and FOXD2-AS1 interacts with EZH2 to silence p21 protein. This finding could provide a novel insight and potential therapeutic target for the OS.

Objectives: We aimed to determine the demographic characteristics of giant cell tumor around the knee in China. Methods: Between March 2000 and June 2014, patients with primary giant cell tumor around the knee were recruited from 6 institutions located in different regions of China, and were reviewed retrospectively the clinical features according to gender and age. Results: 334 qualified patients were included in this study. The sex ratio was 1.14:1 (178/156), with mean ages of 36.9 years in men and 33.1 years in women, constituting a significant difference (P=0.007). The prevalence of pathological fracture was 32.9% overall (28.7% in men and 37.8% in women). The prevalence of simple fracture was significantly higher in women (26.3%) than in men (15.2%), P=0.042. Tumor location and staging did not differ significantly according to sex (P>0.05). However, comparing with >40 years old, those patients aged ≤40 were more likely to have a right knee tumor (56.7% vs. 44.7%, P=0.042), less likely to have Enneking stage 3 disease (18.6% vs. 35.0%, P=0.005), and less likely to have both soft-tissue extension and a mass (18.6% vs. 34.0%, P=0.009). Conclusions: Giant cell tumor around the knee was more common in men than in women, although female patients were younger on average. Further, cases among patients ≤40 years old were observed to be milder than cases among older patients. The results suggest that efficient treatment and preservation of function should both be valued for young patients with giant cell tumor around the knee.

As common bisphosphonates drugs, pamidronate disodium and zoledronic acid have been widely investigated for bone metastases. In this paper, a new “turn-off” model based on carbon dots (CDs) from black tea was established to analyze the two kinds of bisphosphonate drugs, pamidronate disodium and zoledronic acid. Through the new sensor, both of drugs can be quantitative, respectively, with the limit of detection of 5 × 10−9 mol·L−1 and 6 × 10−9 mol·L−1. In addition, the fluorescence of newly prepared CDs can be quenched by two drugs with various degrees via photoinduced electron transfer, which can be perfectly used to distinguish them. Most importantly, this turn-off method has been employed to analyze the two drugs under the influence of foreign interference factors. This method provides a new view and guidance for the rapid analysis and recognition of drugs for bone metastases in vitro and in vivo.

Background Peracetic acid and irradiation are common sterilization methods for allograft tendons; however, under some conditions, both methods adversely affect the fiber arrangement and ultimate load of the tendon. An in vitro study showed that low-dose peracetic acid combined with irradiation may be less detrimental to allograft tendon structure and properties, possibly because the breakdown of peracetic acid can lead to an enlargement of the interstitial spaces and an increase in porosity. Questions/purposes Using a rabbit Achilles tendon model, we asked: What is the effect of peracetic acid-ethanol combined irradiation on (1) the histopathology and fiber diameter of the allograft tendon, (2) tensile creep and load-to-failure biomechanical properties of allograft tendons, and (3) healing of the treated tendon in vivo compared with fresh-frozen allograft and peracetic acid-ethanol sterilization at 4 and 8 weeks? Methods The Achilles tendons used in this study were sourced from euthanized 10-week-old male New Zealand White rabbits previously used for ophthalmic experiments. All allografts were divided into three groups: fresh-frozen group (control group, n = 20), peracetic acid-ethanol sterilization group (n =20), and peracetic acid-ethanol combined irradiation group (n = 20). The sterilization protocols were performed per a predetermined plan. In the peracetic acid-ethanol sterilization group, the tendon tissues were covered with the peracetic acid-ethanol sterilization solution (1% peracetic acid for 30 minutes). In the peracetic acid-ethanol combined irradiation group, the tendon tissues were covered with the peracetic acid-ethanol sterilization solution (0.2% peracetic acid for 30 minutes) and were subjected to 15 kGy gamma irradiation. Thirty 10-week-old male New Zealand White rabbits received bilateral Achilles tendon allografts surgically. Tendon samples from each group were harvested at 4 weeks (n = 30) and 8 weeks (n = 30) postoperatively. For each timepoint, eight tissues were used for histologic staining and electron microscopy, 15 tissues were used for biomechanical testing, and seven tissues were used for hydroxyproline assay and quantitative polymerase chain reaction. Histopathology was determined qualitatively by hematoxylin and eosin and Masson staining, while fiber diameter was measured quantitatively by transmission electron microscopy. Biomechanical properties were measured using cyclic loading tests and load-to-failure tests. The healing outcome was quantitatively judged through healing-related genes and proteins. Results At 4 weeks and 8 weeks postoperatively, the peracetic acid-ethanol combined irradiation group visually demonstrated the best continuity and minimal peripheral adhesions. Histologic staining showed that tendon fibers in the peracetic acid-ethanol combined irradiation group maintained consistent alignment without notable disruptions or discontinuities, and there was a qualitatively observed increase in the number of infiltrating cells compared with the control group at the 4-week timepoint (444 ± 49 /mm² versus 256 ± 43 /mm², mean difference 188 /mm² [95% confidence interval 96 to 281]; p < 0.001). At 8 weeks postoperatively, the tendon fiber diameter in the peracetic acid-ethanol combined irradiation groups was similar to that of the control group (0.23 ± 0.04 μm versus 0.21 ± 0.03 μm, mean difference 0.02 μm [95% CI -0.04 to 0.08]; p = 0.56). At 8 weeks postoperatively, the peracetic acid-ethanol combined irradiation group exhibited better properties in terms of both ultimate load (129 ± 15 N versus 89 ± 20 N, mean difference 40 N [95% CI 7 to 73]; p = 0.02) and energy absorption density (17 ± 6 kJ/m² versus 8 ± 4 kJ/m², mean difference 8 kJ/m² [95% CI 0.7 to 16]; p = 0.004) compared with the control group. Gene expression analysis revealed higher expression levels of COL1A1 (2.1 ± 0.8 versus 1.0 ± 0, mean difference 1.1 [95% CI 0.1 to 2.1]; p = 0.003) and MMP13 (2.0 ± 0.8 versus 1.0 ± 0, mean difference 1.0 [95% CI 0.4 to 1.6]; p = 0.03) in the peracetic acid-ethanol combined irradiation group than in the control group. There was a higher amount of collagen Type I in tendons treated with peracetic acid-ethanol combined irradiation than in the control group (0.36 ± 0.03 versus 0.31 ± 0.04, mean difference 0.05 [95% CI 0.01 to 0.09]; p = 0.02). Conclusion Treatment with peracetic acid-ethanol combined irradiation did not have any discernible adverse effect on the histology, fiber diameter, enzymatic resistance, collagen content, or biomechanical strength of the allograft tendons compared with the control group. Peracetic acid-ethanol combined irradiation treatment had a positive impact on remodeling of the extracellular matrix and realignment of collagen fibers. Clinical Relevance This sterilization method could be helpful to expand the scope and frequency with which allogeneic materials are applied. The long-term healing effect and strength of allograft tendons must be tested before clinical use, and it is necessary to conduct comparative studies on autografts and synthetic materials that are currently widely used clinically. [ABSTRACT FROM AUTHOR]

Stoichiometric operation natural gas engine can achieve low emissions and high-power output by combining EGR and three-way catalytic converter. However, under high load conditions, engine performance will be deteriorated due to the knocking limits. The main methods to solve the knocking problems of spark ignition engines are shortening the flame propagation time and reducing the temperature and pressure rise of the end mixture. This paper firstly established a 3D model based on a natural gas engine, and then conducted the numerical simulations to investigate the effects of chamber geometry, hydrogen ratio and EGR ratio on engine knocking and combustion. The validation indicates a satisfied numerical results of chamber pressure and heat release rate. The turbine chamber exhibits relatively better swirl and tumble, thus achieving the highest turbulence intensity. HCNG fuel will increase the knocking tendency of the engine. In the meantime, the addition of hydrogen will also reduce the IMEP of the engine due to the low volume heat value of hydrogen. However, the addition of hydrogen may accelerate the combustion rate at the end of combustion to a certain extent. EGR can significantly reduce the knocking tendency of HCNG engine by reducing the combustion temperature in the cylinder. Compared with the case of 14% EGR rate, the ignition angle of 30% EGR case is advanced by 19 °CA, and the indicated thermal efficiency is increased by 2.06%.