Cartilage degeneration stands as the main pathological hallmark of joint diseases such as osteoarthritis (OA), characterized by the degradation of cartilage matrix, abnormal cell function, and disruption of structural integrity. This series of changes poses a severe threat to patients’ quality of life. The significant impact of mechanical stimuli on cartilage health and function has long been widely acknowledged, and research on its underlying mechanisms has become relatively systematic and in-depth. However, the specific pathways in which mechanical stimuli affect cartilage, as well as the hidden laws and intrinsic mechanisms behind them, are still in the process of continuous exploration, gradual revelation, and ongoing refinement. This article reviews the research progress in the field of mechanical stimuli and articular cartilage in 2024, indicating that it demonstrated characteristics of greater diversity in research subjects, broader perspectives, and more innovative techniques, further expanding our understanding of the role of mechanical factors in cartilage degeneration. The mechanical regulation-based therapeutic strategies are also explored, such as exercise therapy, biomechanical correction, chemical drug therapy, acupotomy therapy, and tissue engineering, providing theoretical foundations and practical directions for the prevention and treatment of degenerative joint diseases. Future research should concentrate on the integration of multi-scale and multi-perspective mechanisms as well as clinical translation to promote the application of precision medicine in the field of cartilage degeneration.
Knee osteoarthritis (OA) is a primary cause of joint dysfunction. Knee osteotomy has garnered significant attention due to its potential to delay the progression of knee OA and enhance joint function. As a pivotal biomechanical factor in the onset and progression of OA, the accurate correction of abnormal knee alignment is the central objective of knee osteotomy. This article systematically reviews the biomechanical research progress related to knee osteotomy, with a focus on the precision and personalized correction of force line. The development of new classification system and measurement technology of force line is summarized, the biomechanical mechanism of knee OA induced by abnormal mechanical load is analyzed, and the goal of force line and clinical application progress of knee osteotomy is discusses, so as to provide a new perspective and idea for the clinical treatment of knee OA with knee osteotomy.
Traumatic brain injury caused by blast shock waves represents a significant type of injury in modern warfare and civilian explosion accidents. Its high incidence and complexity have attracted a widespread attention, and the injury mechanism and cranial brain protection have become current research hotspots. This review first analyzes the dynamic load characteristics of blast shock waves and introduces the development and verification of cranial brain constitutive and finite element models to explore the mechanical responses of the cranial brain at tissue and cellular levels under blast waves and bullet impacts. Subsequently, the current state of research on injury mechanisms at tissue and cellular levels and cranial brain protection, is systematically summarized based on domestic and international studies. Finally, the current research challenges and future development directions are outlined, and the importance of interdisciplinary cooperation and innovation to promote the research and application transformation of blast-induced traumatic brain injury is emphasized. The findings provide a valuable reference for enhancing the comprehension of injury mechanism and fostering multi-disciplinary integration and protective helmet development.
To analyze the reverse mechano-electric effect of the layered structure of articular cartilage and its influencing factors.
The cartilage samples were classified according to their physiological thickness (approximately 0.4 mm for the upper layer, 1 mm for the middle layer, and 0.6 mm for the lower layer). Through a non-contact external electric field testing method, how different influencing factors affected the reverse mechano-electric effect of articular cartilage was analyzed.
When the electric field spacing decreased, water content increased, and in vitro time decreased, the displacement of normal layered cartilage in a non-contact electric field increased by 18, 10, 15 μm, respectively. In the case of simulated arthritis defects, as the defect depth and radius increased, the overall deviation deflection of articular cartilage gradually decreased by about 7 μm.
The three-layer cartilage differed in their reverse mechano-electricity effects, showing the greatest deflection in the middle layer at 90% water content, under 7 mm electric field spacing, and after 12 hours ex vivo.
To investigate the effects of patient bone mass differences on the stability of unicondylar knee arthroplasty (UKA) prostheses.
A UKA finite element model was established to quantify the effects of five different bone quality conditions on the proximal tibial von Mises stress, bone-prosthesis fixation interface contact stress, and bone-prosthesis fixation interface micromotion, using the medial knee force and joint motion predicted by the individualized UKA musculoskeletal multibody dynamics model as boundary conditions.
The influences of bone strength on the proximal tibia von Mises stress and bone-prosthesis fixation interface contact stress were not obvious, and the difference in peak values of the proximal tibia von Mises stress between two groups of models with the largest difference in bone strength was not more than 5%, and the difference in peak values of the bone-prosthesis fixation interface contact stress was only 2.37 MPa. However, the influence of bone strength on the bone-prosthesis fixation interface micromotion was significant, and the weaker bones were more prone to cause the bone-prosthesis fixation interface micromotion. However, bone strength had a significant effect on the bone-prosthesis fixation interface micromotion, and weak bone was more likely to cause changes in the bone-prosthesis fixation interface micromotion. Compared to patients with the neutral bone quality, the prosthesis fixation interface micromotion increased by 84.67% at 20% gait cycles for patients with the weakest bone quality.
UKA patients with a weaker bone quality have a higher risk of prosthesis loosening. It is recommended that surgeons should carefully choose their surgical strategy in order to reduce the rate of postoperative revision in UKA.
To investigate stress distributions of the knee joint at 0 and 15th day after anterior cruciate ligament reconstruction (ACLR) under a compressive force through the axis of the femoral shaft onto the proximal femur.
A three-dimensional (3D) finite element model of the human knee joint incorporating viscoelastic material properties was developed. The one-dimensional (1D) Prony series viscoelastic constitutive model parameters for articular cartilage, menisci, ligaments, and anterior cruciate ligament (ACL) grafts were determined by fitting experimental creep curves. The viscoelastic parameters of ACL grafts at 15th day after ACLR surgery were extrapolated. Finite element simulations were then performed to analyze the von Mises stress distributions in knee ligaments, ACL grafts, articular cartilage, and menisci under 1.5 kN vertical downward compressive load applied to the femur, with loading durations of 1 second and 600 seconds.
At 15th day after ACLR surgery, the initial relaxation modulus and equilibrium modulus of human ACL grafts remained elevated compared to native ACL tissues, resulting in a significantly higher stress concentration within the grafts relative to healthy ACL. Despite the compromised mechanical properties of the grafts after ACLR surgery, the vertical downward compressive force applied to the femur under both short-term (1 s) and prolonged (600 s) loading durations, exhibited a minimal biomechanical impact on articular cartilage and meniscal structures.
Following ACLR, vertical compressive loads during weight-bearing rehabilitation exercises such as standing demonstrate minimal impact on articular cartilage and meniscus, while promoting fibrous regeneration of the graft. This renders such exercises a prudent early-stage rehabilitation strategy. Graft preparation requires balanced consideration of elastic and viscous properties, with grafts exhibiting higher relaxation modulus and viscosity coefficient than healthy ACL proving more effective in maintaining early postoperative knee stability.
To study the effect of medial collateral ligament (MCL) release on the squatting motion followling total knee arthroplasty (TKA) and provide reference data for ligament release during knee replacement surgery.
Based on CT and MRI images of a volunteer, a three-dimensional (3D) geometric anatomical model of the natural knee joint including bone tissues and major soft tissues was established. A finite element model of the artificial knee joint was established by simulating TKA surgery. The squatting motion after 30% release of the upper end, lower end, and both ends of the MCL was simulated, and motion characteristic data of the knee joint at flexion/extension angles from 0° to 135° were obtained.
The effects of ligament release at different locations on knee squatting motion varied. After releasing the lower end, the medial translation, posterior translation, superior translation, and adduction of the femur relative to the tibia increased by 13.74%, 3.83%, 9.74%, and 2.37%, respectively, while the external rotation decreased by 36.8%. After releasing the upper end, the medial translation and posterior translation increased by 10.65% and 10%, respectively, while the superior translation, adduction, and external rotation decreased by 4.52%, 33.89%, and 67.1%, respectively. After releasing both ends, the medial translation, posterior translation, and superior translation increased by 14.77%, 9.39%, and 22.56%, respectively, while the adduction and external rotation decreased by 15.62% and 47.3%, respectively.
After MCL released, the medial translation, anterior translation, superior translation, and abduction of the femur relative to the tibia increased, while the external rotation decreased. Releasing the lower end had the least effect on these femoral movements, showing an obvious advantage.
To investigate the effect of postoperative reduction quality in femoral neck fracture internal fixation on mechanical properties of the femoral head from the perspective of trabecular bone biomechanics.
From patients who underwent hip replacement surgery for femoral neck fractures, a total of 26 femoral head slice specimens were obtained. The central axis of the primary compressive trabeculae was defined as the 0° group, with the intersection point of the primary compressive trabeculae and the femoral calcar serving as the center. By rotating the specimens to simulate different reduction angles, the cut femoral head slice specimens were randomly divided into five groups: -10°, -5°, 0°, 5°, and 10°, representing femoral heads with varying reduction qualities. The specimens were subjected to single compression load tests and fatigue load tests. The load was set from 70 N to 1 400 N, at a frequency of 1 Hz, with 10 000 cycles. Axial stiffness, displacement, and the number of collapse cycles were measured, to compare the biomechanical properties of femoral head specimens under different reduction qualities.
There were differences in the axial stiffness, displacement, and number of collapse cycles among the femoral head specimens in different groups. Under 800 N load, the axial stiffness of 0° group was significantly greater than that of ±10° groups (P<0.05). The axial stiffness of 0° group was also greater than that of the ±5° groups, but the differences were not statistically significant (P>0.05). The axial stiffness of ±5° groups was greater than that of ±10° groups (P<0.05). 0° group had a lower displacement than ±5° groups and ±10° groups. However, the differences in displacement between 0° group and ±5° groups were not statistically significant (P>0.05), while the differences between the 0° group and ±10° groups were statistically significant (P<0.05). The differences in displacement between ±5° groups and ±10° groups were also statistically significant (P<0.05). 0° group had a significantly higher number of collapse cycles than ±10° groups (P<0.05). The number of collapse cycles in 0° group was also higher than that in ±5° groups, but the differences were not statistically significant (P>0.05). The number of collapse cycles in ±5° groups was significantly higher than that ±10° groups (P<0.05).
The quality of reduction after internal fixation of femoral neck fractures significantly affects the biomechanical properties of the femoral head. This study provides a scientific basis for optimizing treatment and postoperative management, aiming to improve clinical outcomes and patients’ quality of life.
To investigate the effects of inclined axial compressive force and flexion moment on the anterior and posterior shear stiffness of the lumbosacral segment.
Six fresh-frozen human cadaveric L5-S1 segments were tested under intact and two progressively impaired structural conditions: intact, a 4-mm bilateral facet joint gap, and anterior discectomy with nucleus pulposus removal plus circumferential release of the inner annular fibers (disc injury). A 300 N axial compressive force was applied either vertically downward or with a 10° or 20° anterior inclination through the disc's shear center. Anterior (0 N to 250 N) and posterior (-50 N to 0 N) shear tests were conducted using a material testing machine. These tests were repeated under a 5 N·m flexion moment. The relative motion between L5 and S1 was measured using a three-dimensional motion capture system.
In the intact state, the inclination of the axial compressive force did not significantly alter anterior or posterior shear stiffness. However, the application of a flexion moment increased anterior shear stiffness by 49.3%. Progressive structural damage resulted in incremental increases in anteroposterior shear translation and corresponding reductions in stiffness. Notably, under combined loading with axial compression and flexion moment, anterior stiffness decreased from 939 N/mm (intact) to 224 N/mm (disc injury), while posterior stiffness decreased from 572 N/mm to 217 N/mm. Within the low-load range, no significant differences in shear stiffness were observed across any structural conditions, regardless of axial force inclination or combined with a flexion moment.
This study supports the clinical view that retro-inclination of the pelvis serves as a compensatory mechanism to enhance segmental shear stability. However, this compensatory capacity gradually diminishes and ultimately fails as spinal degeneration progresses.
To investigate the protective effect of cerebrospinal fluid (CSF) on the spinal cord in patients with scoliosis and evaluate its buffering effect during gravitational traction surgery and in daily life, so as to provide a theoretical guidance for surgical planning and postoperative rehabilitation of scoliosis.
A three-dimensional coupled spinal cord-CSF finite element model was established to simulate the biomechanical responses of the spine under two scenarios: gravitational traction surgery and daily life. Comparative analyses were conducted for conditions with and without CSF, and the buffering effect of CSF was quantitatively assessed.
During simulated gravitational traction surgery, CSF significantly reduced the stress and deformation of the spinal cord, with the stress in spinal cord white and gray matter decreasing by 65%-90% and deformation decreasing by 70%-95%. In the daily life scenario, CSF provided greater protective effects in lateral flexion and anterior-posterior flexion directions, with stress reductions of 60%-85%. However, in torsion, the buffering effect of CSF was relatively weaker, with stress reductions of only 10%-25%.
CSF significantly reduces spinal cord stress and deformation during gravitational traction surgery and in daily life, reducing the risk of injury.
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