Biomechanical analysis of titanium-alloy and biodegradable implants in dual plate osteosynthesis for AO/ASIF type 33-C2 fractures.

Background and objective: Treating geriatric osteoporotic distal femur fractures has always presented challenges, but developing biodegradable materials has brought new opportunities for therapeutic intervention. Despite this progress, there currently needs to be more evidence-based biomechanical guidelines for using dual plate fixation and biodegradable materials in treating osteoporotic comminuted distal femoral fractures.In this study, finite element analysis was conducted to evaluate the mechanical effectiveness of different implant materials (titanium alloys, biodegradable materials, and combinations of both) in the fixation of physiological and osteoporotic distal femoral fractures. Methods: We constructed finite element models of 33-C2 fractures and three types of plates: the Lateral Less Invasive Stabilization System (LISS) plate, the titanium-alloy medial plate (TAP), and the biodegradable plate (BP). To evaluate the biomechanical advantages in both physiological femur (PF) and osteoporotic femur (OF) conditions, three scenarios were developed: LISS + TAP, LISS + BP, and double biodegradable plates (DBPs). Five loading conditions were applied to measure structural stiffness, fracture micromotion, and implant stress: medio-lateral four-point bending, antero-posterior four-point bending, axial loading, torsional loading, and sideways falling. Several parameters were examined, including peak Von Mises Stress (VMS) of the femur and lateral plate, maximum displacement, bending angle, torsional angle of fracture, and risk of fracture. Results: In four-point bending tests, the lateral plate of the DBPs group exhibited a slightly lower peak VMS compared to the LISS + TAP and LISS + BP groups. When subjected to axial loading, the stiffness values of the LISS + TAP (OF) were 1.42 times and 1.86 times higher than LISS + BP (OF) and DBPs (OF) groups, and the peak VMS of lateral plate of DBPs (OF) construct was approximately 2% and 16% lower than that of the LISS + TAP (OF) and LISS + BP (OF) constructs. Under torsional loading, DBPs (OF) demonstrated rotational stiffness that was respectively 2% and 52% greater than that of LISS + TAP (OF) and LISS + BP (OF). Regarding the peak VMS of femur, the values of DBPs (OF) were almost 8% and 15% lower than those of LISS + TAP (OF) and LISS + BP (OF). Conclusions: The use of DBPs at 11.33 GPa facilitated early mobilization of load-bearing joints but exhibited limited ability to support full weight-bearing activities. Though LISS + TAP met practical strength requirements, one should consider the potential biological irritation and stress shielding. Thus, employing a combination of biodegradable and metal internal fixation is a valid approach to effectively treat weight-bearing joint fractures in clinical practice.

Stability of internal fixation systems based on different subtypes of Schatzker II fracture of the tibial plateau: A finite element analysis.

Background: Schaztker II fracture is the most common type of the tibial plateau fractures (TPF). There has been a large number of cadaveric biomechanical studies and finite element simulation studies to explore the most stable fixation methods for this type of fracture, which were based on a single fracture morphology. But differences among fracture morphologies could directly affect the stability of internal fixation systems. In this sense, we verified the stability of existing internal fixation modalities by simulating Schatzker II fractures with different fracture morphologies. Objectives: To compare the stability of different filler types combined with locked compression plate/screw in different subtypes of Schatzker II TPF. Methods: Four subtypes of Schatzker II were created based on 3D map of TPF. Each of the subtypes was fixed with LCP/screw or LCP/screw combined with different fill types. Stress distribution, displacement distribution, and the load sharing capacity of the filler were assessed by applying the maximum load during gait. In addition, repeated fracture risks of depressed fragment were evaluated regarding to the ultimate strain of bone. Results: The stress concentration of the implant in each scenario was located on the screw at the contact site between the plate and the screw, and the filler of the defect site significantly reduced the stress concentration of the implant (Subtype A: Blank group 402.0 MPa vs. Experimental group 315.2 ± 5.5 MPa; Subtype C: Blank group 385.0 MPa vs. Experimental group 322.7 ± 12.1 MPa). Displacement field analysis showed that filler significantly reduced the reduction loss of the depressed fragment (Subtype A: Blank group 0.1949 mm vs. Experimental group 0.174 ± 0.001 mm; Subtype C: 0.264 mm vs. 0.253 ± 0.002 mm). Maximum strain was in subtype C with the value of 2.3% ± 0.1% indicating the greatest possibility of failure risk. And with the increase of its modulus, the bearing capacity of filler increased. Conclusion: The existence of filler at the defect site can effectively reduce the stress concentration of the implant and the reduction loss of the collapsed block, thus providing good stability for Schatzker II fracture. In subtype A fracture, the modulus of filler presented the slightest influence on the stability, followed by subtype C, while the stability of subtype B was most influenced by the modulus of filler. Therefore, it is necessary to evaluate the preoperative patient imaging data adequately to select the appropriate stiffness of the filler.

HIF-1α in Osteoarthritis: From Pathogenesis to Therapeutic Implications.

Osteoarthritis is a common age-related joint degenerative disease. Pain, swelling, brief morning stiffness, and functional limitations are its main characteristics. There are still no well-established strategies to cure osteoarthritis. Therefore, better clarification of mechanisms associated with the onset and progression of osteoarthritis is critical to provide a theoretical basis for the establishment of novel preventive and therapeutic strategies. Chondrocytes exist in a hypoxic environment, and HIF-1α plays a vital role in regulating hypoxic response. HIF-1α responds to cellular oxygenation decreases in tissue regulating survival and growth arrest of chondrocytes. The activation of HIF-1α could regulate autophagy and apoptosis of chondrocytes, decrease inflammatory cytokine synthesis, and regulate the chondrocyte extracellular matrix environment. Moreover, it could maintain the chondrogenic phenotype that regulates glycolysis and the mitochondrial function of osteoarthritis, resulting in a denser collagen matrix that delays cartilage degradation. Thus, HIF-1α is likely to be a crucial therapeutic target for osteoarthritis via regulating chondrocyte inflammation and metabolism. In this review, we summarize the mechanism of hypoxia in the pathogenic mechanisms of osteoarthritis, and focus on a series of therapeutic treatments targeting HIF-1α for osteoarthritis. Further clarification of the regulatory mechanisms of HIF-1α in osteoarthritis may provide more useful clues to developing novel osteoarthritis treatment strategies.

Benefits and Mechanisms of Exercise Training for Knee Osteoarthritis.

Knee osteoarthritis is a chronic degenerative disease. Cartilage and subchondral bone degeneration, as well as synovitis, are the main pathological changes associated with knee osteoarthritis. Mechanical overload, inflammation, metabolic factors, hormonal changes, and aging play a vital role in aggravating the progression of knee osteoarthritis. The main treatments for knee osteoarthritis include pharmacotherapy, physiotherapy, and surgery. However, pharmacotherapy has many side effects, and surgery is only suitable for patients with end-stage knee osteoarthritis. Exercise training, as a complementary and adjunctive physiotherapy, can prevent cartilage degeneration, inhibit inflammation, and prevent loss of the subchondral bone and metaphyseal bone trabeculae. Increasing evidence indicates that exercise training can improve pain, stiffness, joint dysfunction, and muscle weakness in patients with knee osteoarthritis. There are several exercise trainings options for the treatment of knee osteoarthritis, including aerobic exercise, strength training, neuromuscular exercise, balance training, proprioception training, aquatic exercise, and traditional exercise. For Knee osteoarthritis (KOA) experimental animals, those exercise trainings can reduce inflammation, delay cartilage and bone degeneration, change tendon, and muscle structure. In this review, we summarize the main symptoms of knee osteoarthritis, the mechanisms of exercise training, and the therapeutic effects of different exercise training methods on patients with knee osteoarthritis. We hope this review will allow patients in different situations to receive appropriate exercise therapy for knee osteoarthritis, and provide a reference for further research and clinical application of exercise training for knee osteoarthritis.

Senescence and cell death in chronic liver injury: roles and mechanisms underlying hepatocarcinogenesis.

Chronic liver injury (CLI) is a complex pathological process typically characterized by progressive destruction and regeneration of liver parenchymal cells due to diverse risk factors such as alcohol abuse, drug toxicity, viral infection, and genetic metabolic disorders. When the damage to hepatocytes is mild, the liver can regenerate itself and restore to the normal state; when the damage is irreparable, hepatocytes would undergo senescence or various forms of death including apoptosis, necrosis and necroptosis. These pathological changes not only promote the progression of the existing hepatopathies via various underlying mechanisms but are closely associated with hepatocarcinogenesis. In this review, we discuss the pathological changes that hepatocytes undergo during CLI, and their roles and mechanisms in the progression of hepatopathies and hepatocarcinogenesis. We also give a brief introduction about some animal models currently used for the research of CLI and progress in the research of CLI.