BACKGROUND:The plantarflexor weakness is a common muscle defect in patients with spastic cerebral palsy and Charcot-Marie-Tooth,which clinically manifests abnormal gaits,and the relationship between plantarflexor weakness and abnormal gaits is unclear. OBJECTIVE:To explore the biomechanical behavior of the lower limb under the action of a single factor of plantarflexor weakness to reveal the mechanism of abnormal gait induced by plantarflexor weakness and to provide guidance for the rehabilitation training of patients with plantarflexor weakness. METHODS:A predictive framework of musculoskeletal multibody dynamics in the sagittal plane was established based on OpenSim Moco to predict lower limb joint angles and muscle activation changes during walking in normal subjects.The validity of the framework was verified by combining the inverse kinematics and electromyogram activation time of the experimental data.Reduced isometric muscle forces were used to model plantarflexor weakness and to compare predicted lower extremity joint angles,joint moments,and muscle energy expenditure with normal subjects to analyze the effects of plantarflexor weakness on lower extremity biomechanics. RESULTS AND CONCLUSION:(1)The Moco-based prediction framework realistically predicted the biomechanical changes of the lower limbs during walking in normal subjects(joint angles:normalized correlation coefficient≥0.73,root mean square error≤7.10°).(2)The musculoskeletal model used a small stride support phase to increase the"heel-walking"gait during plantarflexor weakness.When the plantarflexor weakness reached 80%,the muscle energy expenditure was 5.691 4 J/kg/m,and the maximum activation levels of the gastrocnemius and soleus muscles were 0.72 and 0.53,which might cause the plantarflexor weakness patients to be more prone to fatigue when walking.(3)Muscle energy expenditure was significantly higher when the weakness of plantarflexors exceeded 40%,and the joint angles and moments of the lower limbs deteriorated significantly when the weakness of plantarflexors exceeded 60%,suggesting that there may be a"threshold"for the effect of plantarflexor weakness on gait,which may correspond to the point at which health care professionals should intervene in the clinical setting.

Osteoporotic proximal humeral fracture (OPHF) is one of the common osteoporotic fractures in the aged, with an incidence only lower than vertebral compression fracture, hip fracture, and distal radius fracture. OPHF, secondary to osteoporosis and characterized by poor bone quality, comminuted fracture pattern, slow healing, and severely impaired shoulder joint function, poses a big challenge to the current clinical diagnosis and treatment. In the field of diagnosis, treatment, and rehabilitation of OPHF, traditional Chinese and Western medicine have accumulated rich experience and evidence from evidence-based medicine and achieved favorable outcomes. However, there is still a lack of guidance from a relevant consensus as to how to integrate the advantages of the two medical systems and achieve the integrated diagnosis and treatment. To promote the diagnosis and treatment of OPHF with integrated traditional Chinese and Western medicine, relevant experts from Orthopedic Expert Committee of Geriatric Branch of Chinese Association of Gerontology and Geriatrics, Youth Osteoporosis Group of Orthopedic Branch of Chinese Medical Association, Osteoporosis Group of Orthopedic Surgeon Branch of Chinese Medical Doctor Association, and Osteoporosis Committee of Shanghai Association of Integrated Traditional Chinese and Western Medicine have been organized to formulate Expert consensus on the diagnosis and treatment of osteoporotic proximal humeral fracture with integrated traditional Chinese and Western medicine ( version 2024) by searching related literatures and based on the evidences from evidence-based medicine. This consensus consists of 13 recommendations about the diagnosis, treatment and rehabilitation of OPHF with integrated traditional Chinese medicine and Western medicine, aimed at standardizing, systematizing, and personalizing the diagnosis and treatment of OPHF with integrated traditional Chinse and Western medicine to improve the patients ′ function.

Objective To assess the biomechanical differences between the artificial ankle joints INBONE Ⅱ and INFINITY after total ankle arthroplasty(TAA)to provide more scientific and individualized treatment options for patients.Methods A patient-individualized TAA lower extremity MSK MBD model was established using the musculoskeletal(MSK)multibody dynamics(MBD)software AnyBody.The ankle joint contact force,motion,and contact characteristics of artificial ankle joint surfaces were predicted.Results The geometric shape of the articular surface of the artificial ankle had no significant effect on the ankle contact force,but it affected the range of motion and contact characteristics of the articular surface.Compared with INBONE Ⅱ,the coronal plane articular surface arc height of INFINITY was lower,and increased the inversion-eversion and external rotation-internal rotation movements by 7.91%and 2.61%,respectively.Sagittal plane matching was lower,and reduced posterior-anterior and inferior-superior movements by 21.75%and 21.23%,respectively,and medial-lateral movement increased by 49.26%.INFINITY exhibited lower matching with decreases of 18.48%,30.42%,and 26.36%in the medial,lateral,and total joint surface contact areas,respectively.However,the center of the pressure motion trajectory was concentrated on the medial side,while avoiding edge contact stress concentration and reducing the risk of joint dislocation and premature wear of the tibial component.Conclusions The smaller geometric constraints of the INFINITY artificial ankle joint demonstrated better biomechanical performance,thereby promoting improved postoperative ankle joint functional recovery.

The incidence of osteoporotic thoracolumbar vertebral fracture (OTLVF) in the elderly is gradually increasing. The kyphotic deformity caused by various factors has become an important characteristic of OTLVF and has received increasing attention. Its clinical manifestations include pain, delayed nerve damage, sagittal imbalance, etc. Currently, the definition and diagnosis of OTLVF with kyphotic deformity in the elderly are still unclear. Although there are many treatment options, they are controversial. Existing guidelines or consensuses pay little attention to this type of fracture with kyphotic deformity. To this end, the Lumbar Education Working Group of the Spine Branch of the Chinese Medicine Education Association and Editorial Committee of Chinese Journal of Trauma organized the experts in the relevant fields to jointly develop Clinical guidelines for the diagnosis and treatment of osteoporotic thoracolumbar vertebral fractures with kyphotic deformity in the elderly ( version 2024), based on evidence-based medical advancements and the principles of scientificity, practicality, and advanced nature, which provided 18 recommendations to standardize the clinical diagnosis and treatment.

Reconstructing three-dimensional (3D) models from two-dimensional (2D) images is necessary for preoperative planning and the customization of joint prostheses. However, the traditional statistical modeling reconstruction shows a low accuracy due to limited 3D characteristics and information loss. In this study, we proposed a new method to reconstruct the 3D models of femoral images by combining a statistical shape model with Laplacian surface deformation, which greatly improved the accuracy of the reconstruction. In this method, a Laplace operator was introduced to represent the 3D model derived from the statistical shape model. By coordinate transformations in the Laplacian system, novel skeletal features were established and the model was accurately aligned with its 2D image. Finally, 50 femoral models were utilized to verify the effectiveness of this method. The results indicated that the precision of the method was improved by 16.8%-25.9% compared with the traditional statistical shape model reconstruction. Therefore, the method we proposed allows a more accurate 3D bone reconstruction, which facilitates the development of personalized prosthesis design, precise positioning, and quick biomechanical analysis.
Imaging, Three-Dimensional/methods* ; Tomography, X-Ray Computed/methods* ; Femur/surgery* ; Models, Statistical ; Lower Extremity

Humans ; Asthma/drug therapy* ; Biological Therapy

Objective To compare the biomechanical effects of contiguous three-level cervical Hybrid surgery[anterior cervical discectomy and fusion (ACDF) + cervical disc arthroplasty ( CDA)] and three-level ACDF. Methods The finite element model of C1-T1 cervical-thoracic spine was developed based on CT data. Three models were simulated by the implantation of Prestige LP and Zero-P prostheses, including two Hybrid models (AFA, Prestige LP implanted at C3-4 and C5-6 segments and Zero-P implanted at C4-5 segment; FAF, Zero-P implanted at C3-4 and C5-6 segments and Prestige LP implanted at C4-5 segment) and three-level ACDF model(FFF). The changes in range of motion (ROM) of adjacent levels during flexion, extension, lateral bending and axial rotation, the overall ROM, as well as the intradiscal pressure ( IDP) and facet contact force ( FCF) of adjacent levels were compared. Results The ROM in adjacent levels and the overall ROM of the AFA modelwere closer to the intact model, and the maximum increases in the ROM of the adjacent levels for the FAF and FFF models were 15. 0% and 23. 4% , respectively. For AFA, FAF and FFF models, the maximum increases in the maximum IDP of adjacent levels were 19. 0% , 66. 7% , 147. 6% , and the maximum increases in FCF were 17. 4% , 55. 7% , 80. 1% , respectively. Conclusions This study provides biomechanical basis for three-level cervical Hybrid surgery in treating patients with the contiguous three-level cervical degenerative disc disease.

Objective To investigate the effects of design parameters such as neck-shaft angle, femoral offset and anteversion angle of total hip arthroplasty ( THA) prosthesis on contact forces of the hip. Methods A musculoskeletal multi-body dynamic model of THA was established based on AnyBody software. The effects of single or multiple factors on hip contact force were studied when the neck-shaft angle, eccentricity and anteversion angle varied within ±10°, ±20 mm and ±10°, respectively. Results The maximum hip contact force increased by 26. 08% when femoral offset was reduced by 20 mm. The maximum hip contact force increased by 5. 99% when the neck-shaft angle increased by 10°. When the anteversion angle increased by 10°, the hip contact force decreased at 0% -24% of gait cycle, with the peak decreasing by 19. 16% . However, the hip contact force was significantly increased at 38% -70% of gait cycle, with the peak increasing by 67. 78% . Conclusions In extramedullary design of the femoral stem, based on reconstruction of the patient’s anatomical parameters, the offset of the femoral stem can be appropriately increased, and the neck-shaft angle and anteversion angle can bereduced to avoid increasing forces on the hip.

Objective Aiming at the medial prosthetic loosening failure and lateral cartilage degeneration after unicompartmental knee arthroplasty ( UKA), the effects of prosthetic installation errors of joint line in UKA on knee contact mechanics and kinematics during different physiologic activities were studied using musculoskeletal multi-body dynamic method. Methods Taking the medial natural joint line as 0 mm error, six installation errors ofjoint line including ±2 mm, ±4 mm and ±6 mm were considered respectively, and seven musculoskeletal multi body dynamic models of medial UKA were established, to comparatively study the variations in knee contact mechanics and kinematics during walking and squatting. Results At 70% of walking gait cycle, compared with 0 mm error, the medial prosthetic contact force was increased by 127. 3% and the contact force of the lateral cartilage was decreased by 12. 0% under 2 mm elevation in joint line, the medial prosthetic contact force was close to 0 N, but the lateral cartilage contact forces were increased by 10. 1% under 4 mm reduction in joint line. The tibiofemoral total contact forces were increased by 19. 7% and decreased by 14. 2% under 2 mm elevation and 2 mm reduction in joint line, respectively. At the 100°knee flexion during squatting, compared with 0 mm error, the medial prosthetic contact force and the tibiofemoral total contact force increased by 31. 6% and 11. 1% under 2 mm elevation in joint line, and decreased by 24. 5% and 8. 5% under 2 mm reduction in joint line, respectively. The change in the lateral cartilage contact force was not marked. Moreover, at 70% of walking gait cycle, the varus angle decreased, the internal rotation and the anterior translation increased along with the elevation of joint line in UKA, while it was just the opposite along with the reduction of joint line in UKA. The trends of the varus valgus movement and anterior-posterior translation during squatting were consistent with those during swing phase of walking, but the trend of the internal-external rotation was opposite. Conclusions In order to reduce the risk of medial prosthetic loosening failure and lateral cartilage degeneration, it is recommended that the installation error of joint line in UKA should be controlled in the range of -2 mm to +2 mm. This study provides theoretical basis for UKA clinical failure caused by changes in joint line

The surgical installation accuracy of the components in unicompartmental knee arthroplasty (UKA) is an important factor affecting the joint function and the implant life. Taking the ratio of the medial-lateral position of the femoral component relative to the tibial insert (a/A) as a parameter, and considering nine installation conditions of the femoral component, this study established the musculoskeletal multibody dynamics models of UKA to simulate the patients' walking gait, and investigated the influences of the medial-lateral installation positions of the femoral component in UKA on the contact force, joint motion and ligament force of the knee joint. The results showed that, with the increase of a/A ratio, the medial contact force of the UKA implant was decreased and the lateral contact force of the cartilage was increased; the varus rotation, external rotation and posterior translation of the knee joint were increased; and the anterior cruciate ligament force, posterior cruciate ligament force and medial collateral ligament force were decreased. The medial-lateral installation positions of the femoral component in UKA had little effect on knee flexion-extension movement and lateral collateral ligament force. When the a/A ratio was less than or equalled to 0.375, the femoral component collided with the tibia. In order to prevent the overload on the medial implant and lateral cartilage, the excessive ligament force, and the collision between the femoral component and the tibia, it is suggested that the a/A ratio should be controlled within the range of 0.427-0.688 when the femoral component is installed in UKA. This study provides a reference for the accurate installation of the femoral component in UKA.
Humans ; Arthroplasty, Replacement, Knee ; Knee Joint/surgery* ; Knee Prosthesis ; Gait ; Rotation