Effects of integrated intrinsic foot muscle exercise with foot core training device on balance and body composition among community-dwelling adults aged 60 and above.

BACKGROUND: Evidence on the effects of plantar intrinsic foot muscle exercise in older adults remains limited. This study aimed to evaluate the effect of an integrated intrinsic foot muscle exercise program with a novel three-dimensional printing foot core training device on balance and body composition in community-dwelling adults aged 60 and above. METHODS: A total of 40 participants aged ≥ 60 years were enrolled in this quasi-experimental, single-group, pretest-posttest design; participants were categorized into two groups, those with balance impairment and those without balance impairment. The participants performed a 4-week integrated intrinsic foot muscle exercise program with a three-dimensional printing foot core training device. The short physical performance battery (SPPB) and timed up and go test were employed to evaluate mobility and balance. A foot pressure distribution analysis was conducted to assess static postural control. The appendicular skeletal muscle mass index and fat mass were measured by a segmental body composition monitor with bioelectrical impedance analysis. The Wilcoxon signed rank test was used to determine the difference before and after the exercise program. RESULTS: Among the 40 enrolled participants (median age, 78.0 years; female, 80.0%; balance-impaired group, 27.5%), the 95% confidence ellipse area of the center of pressure under the eyes-closed condition was significantly decreased (median pretest: 217.3, interquartile range: 238.4; median posttest: 131.7, interquartile range: 199.5; P = 0.001) after the exercise. Female participants without balance impairment demonstrated a significant increase in appendicular skeletal muscle mass index and a decrease in fat mass. Participants in the balance-impaired group exhibited a significant increase in SPPB. CONCLUSIONS: Integrated intrinsic foot muscle exercise with a three-dimensional printing foot core training device may improve balance and body composition in adults aged 60 and above. TRIAL REGISTRATION: ClinicalTrials.gov ID: NCT05750888 (retrospectively registered 02/03/2023).

Effects of Muscle Fatigue and Recovery on the Neuromuscular Network after an Intermittent Handgrip Fatigue Task: Spectral Analysis of Electroencephalography and Electromyography Signals.

Mechanisms underlying exercise-induced muscle fatigue and recovery are dependent on peripheral changes at the muscle level and improper control of motoneurons by the central nervous system. In this study, we analyzed the effects of muscle fatigue and recovery on the neuromuscular network through the spectral analysis of electroencephalography (EEG) and electromyography (EMG) signals. A total of 20 healthy right-handed volunteers performed an intermittent handgrip fatigue task. In the prefatigue, postfatigue, and postrecovery states, the participants contracted a handgrip dynamometer with sustained 30% maximal voluntary contractions (MVCs); EEG and EMG data were recorded. A considerable decrease was noted in EMG median frequency in the postfatigue state compared with the findings in other states. Furthermore, the EEG power spectral density of the right primary cortex exhibited a prominent increase in the gamma band. Muscle fatigue led to increases in the beta and gamma bands of contralateral and ipsilateral corticomuscular coherence, respectively. Moreover, a decrease was noted in corticocortical coherence between the bilateral primary motor cortices after muscle fatigue. EMG median frequency may serve as an indicator of muscle fatigue and recovery. Coherence analysis revealed that fatigue reduced the functional synchronization among bilateral motor areas but increased that between the cortex and muscle.

Finite element analysis after rod fracture of the spinal hybrid elastic rod system.

BACKGROUND: The spinal hybrid elastic (SHE) rod dynamic stabilization system can provide sufficient spine support and less adjacent segment stress. This study aimed to investigate the biomechanical effects after the internal fracture of SHE rods using finite element analysis. METHODS: A three-dimensional nonlinear finite element model was developed. The SHE rod comprises an inner nitinol stick (NS) and an outer polycarbonate urethane (PCU) shell (PS). The fracture was set at the caudal third portion of the NS, where the maximum stress occurred. The resultant intervertebral range of motion (ROM), intervertebral disc stress, facet joint contact force, screw stress, NS stress, and PCU stress were analyzed. RESULTS: When compared with the intact spine model, the overall trend was that the ROM, intervertebral disc stress, and facet joint force decreased in the implanted level and increased in the adjacent level. When compared with the Ns-I, the trend in the Ns-F decreased and remained nearly half effect. Except for torsion, the PS stress of the Ns-F increased because of the sharing of NS stress after the NS fracture. CONCLUSIONS: The study concluded the biomechanical effects still afford nearly sufficient spine support and gentle adjacent segment stress after rod fracture in a worst-case scenario of the thinnest PS of the SHE rod system.

Kansuinine A Ameliorates Atherosclerosis and Human Aortic Endothelial Cell Apoptosis by Inhibiting Reactive Oxygen Species Production and Suppressing IKKß/IκBα/NF-κB Signaling.

Reactive oxygen species (ROS)-induced vascular endothelial cell apoptosis is strongly associated with atherosclerosis progression. Herein, we aimed to examine whether Kansuinine A (KA), extracted from Euphorbia kansui L., prevents atherosclerosis development in a mouse model and inhibits cell apoptosis through oxidative stress reduction. Atherosclerosis development was analyzed in apolipoprotein E-deficient (ApoE-/-) mice fed a high-fat diet (HFD) using Oil Red O staining and H&E staining. Human aortic endothelial cells (HAECs) were treated with KA, followed by hydrogen peroxide (H2O2), to investigate the KA-mediated inhibition of ROS-induced oxidative stress and cell apoptosis. Oil Red O staining and H&E staining showed that atherosclerotic lesion size was significantly smaller in the aortic arch of ApoE-/- mice in the HFD+KA group than that in the aortic arch of those in the HFD group. Further, KA (0.1-1.0 µM) blocked the H2O2-induced death of HAECs and ROS generation. The H2O2-mediated upregulation of phosphorylated IKKß, phosphorylated IκBα, and phosphorylated NF-κB was suppressed by KA. KA also reduced the Bax/Bcl-2 ratio and cleaved caspase-3 expression, preventing H2O2-induced vascular endothelial cell apoptosis. Our results indicate that KA may protect against ROS-induced endothelial cell apoptosis and has considerable clinical potential in the prevention of atherosclerosis and cardiovascular diseases.

Association Between Targeted Aortic Segment Tortuosity and Stent-Graft-Induced New Entry After Thoracic Endovascular Aortic Repair for Aortic Dissection or Intramural Hematoma.

OBJECTIVE. The aim of this study was to investigate the association between the tortuosity of the targeted aortic segment (TAS) for stent-graft implantation and distal stent-graft-induced new entry (SINE) after thoracic endovascular aortic repair (TEVAR) for aortic dissection or intramural hematoma. MATERIALS AND METHODS. We retrospectively analyzed data from 70 patients who underwent TEVAR using a single stent-graft between 2006 and 2016, and the tortuosity index of the TAS was measured. The patients were divided into high and low TAS tortuosity groups according to the median value of the tortuosity index. The incidence of distal SINE was compared between the two groups. RESULTS. The cumulative incidence of distal SINE at 2 years after TEVAR was 39% in patients in the high TAS tortuosity group and 7% in patients in the low TAS tortuosity group. The incidence of distal SINE was higher in patients in the high TAS tortuosity group than in those in the low TAS tortuosity group (p < 0.01, log-rank test). Multivariate Cox regression showed a higher risk of distal SINE in the high TAS tortuosity group (adjusted hazard ratio, 4.56 [95% CI, 1.40-14.86]; p = 0.01). CONCLUSION. Patients with high TAS tortuosity have a higher incidence of distal SINE after TEVAR. More caution must be exercised during follow-up of patients with high TAS tortuosity after TEVAR.

Application of an interspinous process device after minimally invasive lumbar decompression could lead to stress redistribution at the pars interarticularis: a finite element analysis.

BACKGROUND: An interspinous process device, the Device for Intervertebral Assisted Motion (DIAM™) designed to treat lumbar neurogenic disease secondary to the lumbar spinal stenosis, it provides dynamic stabilization after minimally invasive (MI) lumbar decompression. The current study was conducted using an experimentally validated L1-L5 spinal finite element model (FEM) to evaluate the limited decompression on range of motion (ROM) and stress distribution on a neural arch implanted with the DIAM. METHODS: The study simulated bilateral laminotomies with partial discectomy at L3-L4, as well as unilateral and bilateral laminotomies with partial discectomy combined with implementation of the DIAM at L3-L4. The ROM and maximum von Mises stresses in flexion, extension, lateral bending, and axial torsion were analyzed in response to the hybrid protocol in comparison with the intact model. RESULTS: The investigation revealed that decreased ROM, intradiscal stress, and facet joint force at the implant level, but considerably increased stress at the pars interarticularis were found during flexion and torsion at the L4, as well as during extension, lateral bending, and torsion at the L3, when the DIAM was implanted compared with the defect model. CONCLUSION: The results demonstrate that the DIAM may be beneficial in reducing the symptoms of stress-induced low back pain. Nevertheless, the results also suggest that a surgeon should be cognizant of the stress redistribution at the pars interarticularis results from MI decompression plus the application of the interspinous process device.

Stress distribution of the patellofemoral joint in the anatomic V-shape and curved dome-shape femoral component: a comparison of resurfaced and unresurfaced patellae.

PURPOSE: Whether to resurface the patella in knee replacement remains a controversial issue. The geometrical design of the trochlear groove in the femoral component could play an important role in determining the stress distribution on the patellofemoral joint, but this has not been sufficiently reported on. This study attempted to determine the effect of implant design on contact mechanics by means of a finite element method. METHODS: Two designs, an anatomical V-shape design (VSD) and a dome-shape design (DSD), for the anterior trochlear surface in a contemporary femoral component were chosen for examining the contact characteristics. The use and absence of patella resurfacing was simulated. The stress and strain distribution on the patellar bone and the polyethylene component were calculated for comparison. RESULTS: Without patellar resurfacing, the maximal compressive strain in the patellar bone in the VSD model was about 20 % lower than the DSD model. On the other hand, with resurfacing, the maximal strain for the VSD model was 13.3 % greater than for DSD. Uneven stress distribution at the bone-implant interface was also noted for the two designs. CONCLUSION: The femoral component with a V-shape trochlear groove reduced the compressive strain on the unresurfaced patella. If resurfacing the patella, the femoral component with a curved domed-shape design might reduce the strain in the remaining patellar bone. Uneven stress could occur at the bone-implant interface, so design modifications for improving fixation strength and medialization of the patellar button would be helpful in reducing the risk of peg fracture or loosening. LEVEL OF EVIDENCE: III.

Biomechanical evaluation of a new pedicle screw-based posterior dynamic stabilization device (Awesome Rod System)--a finite element analysis.

BACKGROUND: Pedicle-screw-based posterior dynamic stabilization devices are designed to alleviate the rate of accelerated degeneration of the vertebral level adjacent to the level of spinal fusion. A new pedicle-screw-based posterior dynamic stabilization device- the Awesome Dynamic Rod System was designed with curve cuts on the rods to provide flexibility. The current study was conducted to evaluate the biomechanical properties of this new device. METHODS: Finite element models were developed for the intact spine (INT), the Awesome Dynamic Rod Implanted at L4-L5 (AWE), a traditional rigid rod system implanted at L4-L5 along with an interbody cage (FUS), and the Awesome Dynamic Rod System implanted at L4-L5 along with an interbody cage as an adjunct to fusion procedures and extension of dynamic fixation to L3-L4 (AWEFUS). The models were subjected to axial loads and pure moments and evaluated by a hybrid method on range of motion (ROM)s, disc stresses, pedicle screws stresses, and facet joint contact forces. RESULTS: FUS sustained the lowest L4-L5 ROM decrement in flexion and torsion. AWE demonstrated the lowest adjacent level ROM increment in all moments except for extension at L3-L4, and AWEFUS showed the greatest ROM increment at L2-L3. AWE demonstrated lowest adjacent segment disc stress in flexion, lateral bending and torsion at L3-L4. AWEFUS showed the highest disc stress increment in flexion, extension, and lateral bending, and the lowest disc stress decrement in torsion at L2-L3. AWE sustained greater adjacent facet joint contact forces than did FUS in extension and lateral bending at L3-L4, and AWEFUS demonstrated the greatest contact forces concentrating at L2-L3. CONCLUSION: The results demonstrate that the Awesome Dynamic Rod System preserved more bridged segment motion than did the traditional rigid rod fixation system except in extension. However, the Awesome Dynamic Rod System bore a greater facet joint contact force in extension. The Awesome Dynamic Rod System did protect the adjacent level of fusion segments, but led to much greater ROM, disc stresses, and facet joint contact forces increasing at the adjacent level of instrumented segments.

Patellofemoral kinematics during deep knee flexion after total knee replacement: a computational simulation.

PURPOSE: Actions requiring deep knee flexion, such as kneeling and squatting, are challenging to perform after total knee replacement (TKR), though many manufactures emphasize that their knee prostheses could safely achieve high flexion. Little is known about the patellofemoral kinematics during deep flexion. This study aimed to track the movement of the patella during kneeling and squatting through dynamic computational simulation. METHODS: A validated knee model was used to analyse the patellar kinematics after TKR, including shifting, tilting and rotation. The data were captured from full extension to 135° of knee flexion. For kneeling, an anterior force of 500 N was applied perpendicularly on the tibial tubercle as the knee flexed from 90° to 135°. For squatting, a ground reaction force was applied through the tibia from full extension to 135° of flexion. RESULTS: This study found that patellar shifting and rotation in kneeling were similar to those while squatting. However, during kneeling, the patella had a greater medial tilt and showed signs of abrupt patellar tilt owning to an external force being concentrated on the tibial tubercle. CONCLUSIONS: In terms of squatting and kneeling movements, the latter is a more strenuous action for the patellofemoral joint after TKR due to the high forces acting on the tibial tubercle. It is suggested that overweight patients or those requiring high flexion should try to avoid kneeling to reduce the risk of the polyethylene wear. Further modification of trochlear geometry may be required to accommodate abrupt changes in patellar tilting. LEVEL OF EVIDENCE: II.

Research and Development of a 3D-Printed Dynamic Finger Flexion Orthosis for Finger Extension Stiffness-A Preliminary Study.

Finger extension stiffness is a common post-traumatic complication that results in the hand's functional impairment. In clinical practice, a dynamic splint enables the patient to stretch the affected finger independently. However, current dynamic splints have drawbacks, such as limited stretching efficacy, and interfere with the hand's functional activities. Therefore, this study aimed to develop a dynamic finger flexion orthosis capable of stretching each finger joint using additive manufacturing (AM) technology, thereby enabling hand functional activity, and analyze the clinical improvement in the range of motion (ROM). One subject with a hand fracture was recruited while undergoing a 7-week home-based rehabilitation program for the orthosis. The outcome measurements included the total active motion (TAM), the tip-to-finger distance (TPD), and the score on the Disability of Arm, Shoulder, and Hand (DASH) questionnaire. The results show that the TAM of the participant's fingers increased by 72.7 degrees on average, the TPD decreased by 3.5 cm on average, and the DASH score decreased to 9.5 points. The 7-week home-based rehabilitation program for the orthosis resulted in a 53.6% increase in the TAM on average. The developed orthosis improved hand function and enabled a more complete ROM in finger flexion.

Biomechanical evaluation of 3D-printed joint-type orthosis for hallux valgus.

BACKGROUND: Orthoses play an important role in the conservative treatment of hallux valgus (HV) with different therapeutic effects. In this study, a new HV orthosis was developed using three-dimensional (3D) printing technology. In addition, its kinematic effect was evaluated using motion analysis. METHODS: Seventeen participants with an HV angle of >20° were included in the study. The first metatarsophalangeal abduction angle before and after the orthosis was measured statically. Subsequently, dynamic first metatarsophalangeal abduction, dorsiflexion angle and ground reaction force with and without the orthosis were recorded and calculated during walking using a Vicon motion analysis system and force plates. The patients' comfort scales were determined after the motion analysis. RESULTS: The angular corrections of the orthosis in the first metatarsophalangeal abduction were 14.6° and 6.3° under static and dynamic conditions, respectively. Reduced hallux dorsiflexion was observed with the orthosis in the early stance phase. However, no significant changes in ground reaction forces were observed. CONCLUSION: The results of our study confirm the potential of the 3D-printed HV orthosis in the static and dynamic correction of deformities while ensuring patient comfort with minimal impact on hallux kinematics, suggesting the potential of our design for long-term use.

Effects of cord pretension and stiffness of the Dynesys system spacer on the biomechanics of spinal decompression- a finite element study.

BACKGROUND: The Dynesys system provides stability for destabilized spines while preserving segmental motion. However, clinical studies have demonstrated that the Dynesys system does not prevent adjacent segment disease. Moreover, biomechanical studies have revealed that the stiffness of the Dynesys system is comparable to rigid fixation. Our previous studies showed that adjusting the cord pretension of the Dynesys system alleviates stress on the adjacent level during flexion. We also demonstrated that altering the stiffness of Dynesys system spacers can alleviate stress on the adjacent level during extension of the intact spine. In the present study, we hypothesized that omitting the cord preload and changing the stiffness of the Dynesys system spacers would abate stress shielding on adjacent spinal segments. METHODS: Finite element models were developed for - intact spine (INT), facetectomy and laminectomy at L3-4 (DEC), intact spine with Dynesys system (IntDyWL), decompressed spine with Dynesys system (DecDyWL), decompressed spine with Dynesys system without cord preload (DecDyNL), and decompressed spine with Dynesys system assembled using spacers that were 0.8 times the standard diameter without cord pretension (DecDyNL0.8). These models were subjected to hybrid control for flexion, extension, axial rotation; and lateral bending. RESULTS: The greatest decreases in range of motion (ROM) at the L3-4 level occurred for axial rotation and lateral bending in the IntDyWL model and for flexion and extension in the DecDyWL model. The greatest decreases in disc stress occurred for extension and lateral bending in the IntDyWL model and for flexion in the DecDyWL model. The greatest decreases in facet contact force occurred for extension and lateral bending in the DecDyNL model and for axial rotation in the DecDyWL model. The greatest increases in ROMs at L2-3 level occurred for flexion, axial rotation and lateral bending in IntDyWL model and for extension in the DecDyNL model. The greatest increases in disc stress occurred for flexion, axial rotation and lateral bending in the IntDyWL model and for extension in the DecDyNL model. The greatest increases in facet contact force occurred for extension and lateral bending in the DecDyNL model and for axial rotation in the IntDyWL model. CONCLUSIONS: The results reveals that removing the Dynesys system cord pretension attenuates the ROMs, disc stress, and facet joint contact forces at adjacent levels during flexion and axial rotation. Removing cord pretension together with softening spacers abates stress shielding for adjacent segment during four different moments, and it provides enough security while not jeopardizes the stability of spine during axial rotation.

Using a 3D-Printed Hand Orthosis to Improve Three-Jaw Chuck Hand Function in Individuals With Cervical Spinal Cord Injury: A Feasibility Study.

Individuals with cervical spinal cord injury (C-SCI) often use a tenodesis grip to compensate for their hand function deficits. Although clinical evidence confirms that assistive devices can help achieve hand function improvements, the currently available devices have some limitations in terms of their price and accessibility and the difference in the user's muscle strength. Therefore, in this study, we developed a 3D-printed wrist-driven orthosis to improve the gripping effect and tested the feasibility of this device by assessing its functional outcomes. A total of eight participants with hand function impairment due to a C-SCI were enrolled, and a wrist-driven orthosis with a triple four-bar linkage was designed. The hand function of the participants was assessed before and after they wore the orthosis, and the outcomes were assessed using a pinch force test, a dexterity test (Box and block test, BBT), and a Spinal Cord Independence Measure Version III questionnaire. In the results, before the participants wore the device, the pinch force was 0.26 lb. However, after they wore the device, it increased by 1.45 lb. The hand dexterity also increased by 37%. After 2 weeks, the pinch force increased by 1.6 lb and the hand dexterity increased by 78%. However, no significant difference was observed in the self-care ability. The results showed that this 3D-printed device with a triple four-bar linkage for individual with C-SCI improved pinch strength and hand dexterity in these patients, but did not improve their self-care ability. It may help patient in the early stages of C-SCI to learn and use the tenodesis grip easily. However, the usability of the device in daily life needs further research.

Biomechanical Effects of a Novel Pedicle Screw W-Type Rod Fixation for Lumbar Spondylolysis: A Finite Element Analysis.

Lumbar spondylolysis involves anatomical defects of the pars interarticularis, which causes instability during motion. The instability can be addressed through instrumentation with posterolateral fusion (PLF). We developed a novel pedicle screw W-type rod fixation system and evaluated its biomechanical effects in comparison with PLF and Dynesys stabilization for lumbar spondylolysis via finite element (FE) analysis. A validated lumbar spine model was built using ANSYS 14.5 software. Five FE models were established simulating the intact L1-L5 lumbar spine (INT), bilateral pars defect (Bipars), bilateral pars defect with PLF (Bipars_PLF), Dynesys stabilization (Bipars_Dyn), and W-type rod fixation (Bipars_Wtyp). The range of motion (ROM) of the affected segment, the disc stress (DS), and the facet contact force (FCF) of the cranial segment were compared. In the Bipars model, ROM increased in extension and rotation. Compared with the INT model, Bipars_PLF and Bipars_Dyn exhibited remarkably lower ROMs for the affected segment and imposed greater DS and FCF in the cranial segment. Bipars_Wtyp preserved more ROM and generated lower stress at the cranial segment than Bipars_PLF or Bipars_Dyn. The injury model indicates that this novel pedicle screw W-type rod for spondylolysis fixation could return ROM, DS, and FCF to levels similar to preinjury.

Shorter screw lengths in dynamic Dynesys fixation have less screw loosening: From clinical investigation to finite-element analysis.

BACKGROUND: The dynamic Dynesys Stabilization System preserves lumbar mobility at instrumented levels. This study investigated the effect of screw length on screw loosening (SL) after dynamic Dynesys fixation and screw displacement during lumbar motion, using clinical investigation and finite-element (FE) analysis. METHODS: Clinical data of 50 patients with degenerative spondylolisthesis treated with decompression and Dynesys fixation in 2011 were analyzed retrospectively. Horizontal sliding displacement and vertical displacement of screw tips at L4 were analyzed postoperatively using displacement-controlled FE analysis at the L4-L5 level with screw lengths 45 (long screw), 36 (median screw), and 27 (short screw), and 6.4 mm in diameter, under flexion, extension, lateral bending, and rotation. RESULTS: In 13 patients (13/50, 26%), 40 screws (40/266, 15%) were loose at mean follow-up of 101.3 ± 4.4 months. Radiographic SL at 35, 40, 45, and 50 mm were 7.7%, 10.7%, 12.1%, and 37.5%, respectively, regardless of the fixation level ( p = 0.009). FE analysis revealed that the long screw model with corresponding longer lever arm had maximal horizontal sliding displacement under all directions and maximal vertical displacement, except for lateral bending. CONCLUSION: Shorter screws in Dynesys fixation may help avoid dynamic SL. Clinically, 50 mm screws showed the greatest SL and median screw screws demonstrated the least displacement biomechanically.

Impaired microvascular flow motion in subclinical diabetic feet with sudomotor dysfunction.

Impaired cutaneous blood flow and sweating dysfunction might be among the earliest manifestations of diabetic autonomic neuropathy. This study assessed the pathophysiological basis underlying skin vasomotion changes and their relation with progressive sudomotor dysfunction and other autonomic and somatic measures in subclinical diabetic feet. Laser Doppler skin perfusion was assessed on 68 diabetic and 25 control subjects. The low-frequency vasomotion was transformed into three frequency intervals 0.0095-0.021, 0.021-0.052 and 0.052-0.145 Hz, respectively, for the investigation of endothelial, neurogenic and myogenic effects on microcirculatory alterations. The diabetic patients were categorized into three groups by increasing severity of sudomotor dysfunction: SSR+ (sympathetic skin response present; 27 patients), SSR- (SSR absent; 23 patients) and at-risk (SSR absent and of preulcerative cracked skin; 18 patients). All diabetic patients underwent nerve conduction and cardiovascular autonomic studies. The total spectral and endothelial activity was significantly decreased only in the at-risk group. The SSR- group had lower neurogenic vasomotion than the SSR+ group (p<0.05). Although no statistical difference was noted between any group in absolute myogenic spectrum, the SSR- group had higher normalized myogenic activity than the SSR+ group (p<0.01). The larger drop in orthostatic pressure was paralleled by a reduction in the myogenic amplitude (r=-0.33, p<0.01). These results suggested that early impairment of low-frequency flow motion correlated closely with the presence of sudomotor dysfunction of subclinical feet mainly in neurogenic and endothelial components. Impaired systemic vascular tone as manifested by orthostatic hypotension was proportional to the degree of myogenic dysregulation in diabetic patients.

Effect of spacer diameter of the Dynesys dynamic stabilization system on the biomechanics of the lumbar spine: a finite element analysis.

STUDY DESIGN: A finite element analysis to simulate the behavior of lumbar spines implanted with a posterior dynamic neutralization system, Dynesys, under displacement-controlled loading. OBJECTIVE: To investigate whether Dynesys spacers with different diameters would alter the distribution of range of motion, disk stress, and facet contact force at the Dynesys bridging level and the cranial adjacent level. SUMMARY OF BACKGROUND DATA: The Dynesys system is designed to preserve intersegmental motion and reduce loading at adjacent levels, but clinical reports do not support these claims. This system has been shown to be almost as stiff as rigid fixation, which acts to hinder intersegmental motion. Few studies have investigated methods of reducing this stiffness. METHODS: In the finite element study, a previously validated lumbar spine model was used. Five Dynesys constructs with different spacer diameters (0.8, 0.9, 1.0, 1.1, and 1.2 times the original standard size) were implanted into the spine model and bore 4 displacement-controlled loading cases: flexion, extension, torsion, and lateral bending. Resultant range of motions (ROMs), disk stress, and facet contact forces at the bridged level and the cranial adjacent level were compared with the results of a spine model without Dynesys implantation. RESULTS: The results of ROMs, disk stress, and facet contact forces at the bridged levels were all less than those in the intact spine, except for contact forces at the left facet under lateral bending, facet contact forces at the right facet under torsion, and disk stress under torsion. The results of ROMs, disk stress, and facet contact forces at the cranial adjacent levels were all higher than those in the intact spine. CONCLUSIONS: The results of the present study show that changing the diameter of the spacers will alter the stiffness of the Dynesys construct. Dynesys constructs with larger diameters behave stiffer under flexion but behave softer under extension, torsion, and lateral bending. Changing the diameter of the Dynesys spacers does not significantly influence the load distribution at adjacent levels.

Functional Assessment of 3D-Printed Multifunction Assistive Hand Device for Chronic Stroke Patients.

Patients with chronic stroke often have difficulty opening their hands and performing grasping movements. Several passive hand orthoses for assisting hand rehabilitation have been developed and demonstrated to be clinically effective. However, current devices have several limitations, such as supporting only a single grasping motion and using an abnormal grasping posture. Therefore, this study developed a three-dimensional (3D)-printed multifunctional hand device (3DP-MFHD) to solve these problems and evaluated the feasibility of using the device during home rehabilitation. Six participants were enrolled, and each of them was provided with the 3DP-MFHD. In addition to a task-oriented training course, the participants were asked to train at home for 4 weeks for at least 5 days per week and 40 min per day. The results revealed that hand grip force increased by 36.1%, lateral pinch force increased by 17.6%, and the Action Research Arm Test score increased by 54.1%. The 3DP-MFHD is a promising means to facilitate hand rehabilitation and improve hand strength and function in patients with chronic stroke. The 3DP-MFHD can be used as part of home rehabilitation.

Biomechanical Analysis of the FlatFoot with Different 3D-Printed Insoles on the Lower Extremities.

Insoles play an important role in the conservative treatment of functional flat foot. The features of 3D-printed insoles are high customizability, low cost, and rapid prototyping. However, different designed insoles tend to have different effects. The study aimed to use 3D printing technology to fabricate three different kinds of designed insoles in order to compare the biomechanical effects on the lower extremities in flat foot participants. Ten participants with functional flat foot were recruited for this study. Data were recorded via a Vicon motion capture system and force plates during walking under four conditions: without insoles (shoe condition), with auto-scan insoles (scan condition), with total contact insoles (total condition), and with 5-mm wedge added total contact insoles (wedge condition). The navicular height, eversion and dorsiflexion angles of the ankle joint, eversion moment of the ankle joint, and adduction moment of the knee joint were analyzed, and comfort scales were recorded after finishing the analysis. Compared to the shoe condition, all three 3D printed insoles could increase the navicular height and ankle dorsiflexion angle and improve comfort. Among the three insoles, the wedge condition was the most efficient in navicular height support and increasing the ankle dorsiflexion angle.

Novel Modular Spine Blocks Affect the Lumbar Spine on Finite Element Analysis.

Introduction: There are various surgical interventions to manage osteoporotic vertebral compression fracture. Modular spine block (MSB) is a novel intravertebral fixator that can be assembled. This study aimed to quantitatively investigate the force distribution in vertebrae with the various structural designs and implantation methods by finite element analysis (FEA). Methods: A three-dimensional nonlinear FEA of the L3 implanted with MSB was constructed. Different structural designs (solid vs. hollow) and implantation methods (three-layered vs. six-layered and unilateral vs. bilateral) were studied. The model was preloaded to 150 N-m before the effects of flexion, extension, torsion, and lateral bending were analyzed at the controlled ranges of motion of 20°, 15°, 8°, and 20°, respectively. The resultant intervertebral range of motion (ROM) and disk stress as well as intravertebral force distribution were analyzed at the adjacent segments. Results: The different layers of MSB provided similar stability at the adjacent segments regarding the intervertebral ROM and disk stress. Under stress tests, the force of the solid MSB was shown to be evenly distributed within the vertebrae. The maximum stress value of the unilaterally three-layered hollow MSB was generally lower than that of the bilaterally six-layered solid MSB. Conclusions: The MSB has little stress shielding effect on the intervertebral ROM and creates no additional loading to the adjacent disks. The surgeon can choose the appropriate numbers of MSB to fix vertebrae without worrying about poly(methyl methacrylate) extravasation, implant failure, or adjacent segment disease.