Design of variable stiffness insole based on diabetics plantar pressure during gait period / 中国康复理论与实践

ObjectiveTo analyze the characteristics of plantar pressure of diabetic patients during gait cycle, and to design a offloading insole with variable stiffness. MethodsThe plantar pressure experiment was carried out and a database including 157 subjects was established. The differences of plantar pressure distribution were analyzed among diabetic patients with and without peripheral neuropathy, and healthy people. The insole pressure area was divided, and porous units were filled in different insole areas according to the pressure gradient. The fed-calf-insole finite element model of diabetic patients was constructed. The simulation analysis of different insole schemes was carried out under the conditions of push-off, footheel-strike and dynamic neutrality posture, and to explore the most reasonable insole stiffness design. ResultsCompared with the healthy group, the percentage of peak pressure and high pressure in the left and right heel areas of diabetic neuropathy patients showed a decreasing trend, in which the left peak pressure was significantly reduced by 11% (P = 0.026) and the percentage of high pressure was significantly reduced by 9.8% (P = 0.02). When the porous elements of 2.5 MPa and 1.9 MPa were used in the high pressure area of the insole metatarsal and high pressure area of the heel, the peak plantar pressure of footheel-strike, dynamic neutral and push-off was reduced by 42.4%, 27.4% and 26.4%, and the peak stress of the soft tissue was reduced by 49.8%, 43.6% and 25.1%, respectively. ConclusionThere is a higher risk of ulcer in the metatarsal region than in the heel region for diabetic patients. The variable stiffness insoles based on the optimization of plantar pressure and internal stress under multi-posture can effectively reduce the peak pressure of plantar and peak stress of soft tissue during walking, which provides a reference for the design of variable stiffness insoles.

Structural Design and Optimization of Cushioning Insole with Variable Stiffness / 医用生物力学

Objective An X-shaped cushioning insole with variable stiffness was designed to explore its effects on plantar pressure and internal stress of diabetic patients with toe amputation. Methods Based on CT images, the feet-calf finite element model of diabetic patients with toe amputation was established, and the insole was divided into different areas according to distribution characteristics of the planter pressure. The three-dimensional (3D) printed cushioning insole with an X-shaped sandwich structure was designed. The modulus of the sandwichstructure was changed by changing thickness of the sandwich structure panel. For simulation analysis, the divided area was filled with the X-shaped sandwich structure with different modulus. Results The peak plantar pressure of diabetic patients with toe amputation was in calcaneal region, and the combined insoles with 1. 2 mpanel thickness in toe area, 1. 4 mm panel thickness in metatarsal area, 2. 0 mm panel thickness in middle area and 1. 6 mm panel thickness in heel area had the best decompression effect. Compared with bare feet, the peak pressure in heel area of the insole, the peak pressure in phalangeal head area and the stress in plantar softissues were reduced by 40. 18% , 31. 7% , and 50. 44% , respectively. Conclusions The 3D printed insoles with variable stiffness can effectively reduce surface pressure and internal stress of the sole and reduce probability of the 2nd toe amputation

A Continuum Constitutive Model of skeletal Muscle at Variable Strain Rate / 医用生物力学

Objective Aiming at the problem that mechanical properties for the continuum of muscle tissues cannot be considered in active and passive behaviors of different structurally coupled muscles, a method of passive and active coupling in the same constitutive equation was proposed to construct ahyperelastic active and passive constitutive model of skeletal muscle continuum. Methods In order to calibrate parameters of the passive constitutive model, the uniaxial tensile experiment method and conditions were given, and through theoretical derivation, the specific method of using experimental data to solve the passive model parameters was introduced. In order to verify effectiveness of the active model, the model was verified with an example. Results The curves predicted by the model were in good agreement with the experimental output stress-stretch ratio curves. At the same strain, the maximum error of passive stress and total stress were only 20 kPa and 40 kPa. Conclusions The continuum hyperelastic constitutive model can better simulate active and passive behavior of skeletal muscles, which is beneficial for modeling and simulation of human muscles in further study.

Finite element analysis on biomechanical properties of medial collateral ligament of elbow joint under different flexion angles / 生物医学工程学杂志

Three-dimensional finite element model of elbow was established to study the effect of medial collateral ligament (MCL) in maintaining the stability of elbow joint. In the present study a three-dimensional geometric model of elbow joint was established by reverse engineering method based on the computed tomography (CT) image of healthy human elbow. In the finite element pre-processing software, the ligament and articular cartilage were constructed according to the anatomical structure, and the materials and contacts properties were given to the model. In the neutral forearm rotation position and 0° flexion angle, by comparing the simulation data of the elbow joint with the experimental data, the validity of the model is verified. The stress value and stress distribution of medial collateral ligaments were calculated at the flexion angles of elbow position in 15°, 30°, 45°, 60°, 75°, 90°, 105°, 120°, 135°, respectively. The result shows that when the elbow joint loaded at different flexion angles, the anterior bundle has the largest stress, followed by the posterior bundle, transverse bundle has the least, and the stress value of transverse bundle is trending to 0. Therefore, the anterior bundle plays leading role in maintaining the stability of the elbow, the posterior bundle plays supplementary role, and the transverse bundle does little. Furthermore, the present study will provide theoretical basis for clinical recognizing and therapy of elbow instability caused by medial collateral ligament injury.

Relationship between level of serum triglyceride and early pain after posterior lumbar interbody fusion / 局解手术学杂志

Objective To investigate the relationship between the level of serum triglyceride and early pain after posterior lumbar interbody fusion.Methods A total of 79 patients who were admitted into our hospital from March 2016 to December 2016 were selected into the study,and these patients were divided into two groups according to the degree of pain which means 32 cases in the minor pain group and 47 cases in the intermediate pain group.The difference of serum triglyceride level 3 days after operation were compared between the two groups.Pearson correlation analysis was performed to test the correlation between the level of serum triglyceride and early post-surgical pain.Logistic regression analysis was performed to test the risk factors for early post-surgical pain.Results The data indicated the level of pain was significant higher in the intermediate pain group than that of the minor pain group.Level of serum triglyceride had a significantly positive correlation with the level of post-surgical pain and it was the risk factor of pain after posterior lumbar interbody fusion.Conclusion The level of serum triglyceride is the risk factor of early post-surgical pain of lumbar single level interbody infusion,and it should be adjusted in the perioperative treatment.

Analysis on risk factor for lumbar disc herniation after decompression / 局解手术学杂志

Objective The study aimed to identify risk factors of lumbar disc herniation in patients after decompression,and provide theoretical basis for postoperaive rehabilitation.Methods A told of 169 patients with lumbar spinal stenosis underwent bilateral partial laminectomy were included in the study,24 patients in herniation group,and 145 patients without develop postoperative acute sciatica as a control group.The radiographic variables were measured.The threshold of risk factors was evaluated by multiple logistics analysis and receiver operating characteristic curve(ROC) analysis.Results The results revealed that preoperative retrolisthesis during extension was the independent risk factor for lumbar disc herniation(1.24,95％CI[1.07～1.43];P<0.01).The area under the curve(AUC) was 0.801,and the cutoff value was 6.89％.Conclusion The preoperative retrolisthesis was the risk factor of lumbar disc herniation.