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BACKGROUND: Many older persons with degenerative physical functions use walking aids to improve their ambulation ability. The aim of this study was to investigate the effects of walking aids with different configurations on shoulder joint motion in older persons. METHODS: The 3D motion capture system VICON was applied to collect data on gait parameters and shoulder motion characteristics of 6 older persons walking either independently or with the assistance of a footed walking frame and a wheeled walking frame. The different effects of walking aids on gait parameters and the shoulder joint motion of older individuals were quantitatively analyzed. RESULTS: The gait parameters of the older individuals changed significantly when they used walking frames to assist walking. Compared to independent walking, the range of motion of the shoulder joint was reduced by 79.92% in flexion when walking with a wheeled walking frame. Meanwhile, the range of motion in flexion, extension, and external rotation increased by 76.04%, 85.55%, and 110.99%, respectively, when walking with a footed walking frame. CONCLUSION: The motion characteristics of shoulder joints in older persons were significantly affected by using different walking aids. These changes in shoulder joint motion characteristics will lead to potential diseases related to the shoulder musculoskeletal system. These findings are beneficial to determine a walking aid for older people.
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Articulación del Hombro , Humanos , Anciano , Anciano de 80 o más Años , Fenómenos Biomecánicos , Caminata , Marcha , PieRESUMEN
BACKGROUND: Different posterior inclinations of tibial component after unicompartmental knee arthroplasty (UKA) may lead to different biomechanical characteristics of the knee joint. This finite element study was designed to investigate the tibiofemoral contact pressures after UKA with different posterior inclinations of tibial component. METHODS: Finite element model of a healthy knee joint was constructed, and mobile-bearing (MB) UKA models with 5 different posterior inclinations (3°, 5°, 7°, 9° and 11°) of tibial components were simulated. The maximum contact pressures of tibial plateau cartilage in the lateral compartment and polyethylene insert in the medial compartment were calculated based on the ground reaction force and the angle of the knee flexion obtained by 3D motion capture system. RESULTS: The loading ratio of medial and lateral compartments during standing stance (medial 54.49%, lateral 45.51%) and tibial anterior displacement (134 N, 3.89 mm) of healthy knee was basically consistent with previous experimental data. The maximum contact pressures of the medial meniscus and lateral tibial plateau cartilage of the healthy knee during standing stance were 2.14 MPa and 1.57 MPa, respectively. At the static standing phase, the maximum contact pressures of the polyethylene insert decreased from 17.90 to 17.29 Mpa, and the maximum contact pressures of the tibial plateau cartilage in the lateral compartment increased from 0.81 to 0.92 Mpa following an increase in the posterior inclination of the tibial component. At the first peak of ground reaction force, the maximum contact pressures of polyethylene insert increased from 22.37 to 25.16 MPa, and the maximum contact pressures of tibial plateau cartilage in the lateral compartment increased from 3.03 to 3.33 MPa, with the increase in the posterior inclination of the tibial component. At the second peak of ground reaction force, the maximum contact pressures of polyethylene insert decreased from 2.34 to 2.22 MPa with the increase in posterior inclination of tibial component. CONCLUSION: The preoperative and postoperative finite element models of MB UKA were well established. The results showed that the maximum contact pressures of the polyethylene insert did not change significantly with the increase in the posterior inclination of the tibial prosthesis, while the maximum contact pressures of the tibial plateau cartilage of the lateral compartment increased when the posterior inclination of the tibial prosthesis was > 7°. Our results also show that the maximum contact pressures were greater with an excessive inclination angle (11°) of the tibial component, and the pressures of the tibial plateau cartilage in the lateral compartment were more concentrated on the posterior area. This study, therefore, proposes that excessive osteotomy should be avoided.
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Artroplastia de Reemplazo de Rodilla , Prótesis de la Rodilla , Artroplastia de Reemplazo de Rodilla/métodos , Fenómenos Biomecánicos , Análisis de Elementos Finitos , Articulación de la Rodilla/cirugía , Tibia/cirugía , Polietileno , Meniscos Tibiales/cirugíaRESUMEN
Cervical laminectomy has usually been applied in treating cervical spinal cord tumour. However, spinal instability after laminectomy was observed with high occurrence rate, due to excising of posterior structures. This study was to investigate the biomechanical performances of ligament repair on the cervical stability in lamina repair surgery. A finite element of cervical spine model (C2-C7) was developed, and lamina repair surgery with and without ligament repair was simulated at C3-C6 segments. All models were loaded with pure moment of 1.5 Nm to produce flexion, extension, lateral blending and axial torsion. Compared to intact model, the range of motion (ROM) at C2-C3, C6-C7 increased by 12.8%-113.6% in lamina repair model (LRM), while the change of ROM in other segments was less than 9.2%. The change of ROM in all segments in the lamina and ligament repair model (LLRM) was less than 7.2%. The maximal intradiscal pressure (IDP) in adjacent segment (C2-C3 and C6-C7) increased by 73.7%, and the maximal stresses in capsular ligament increased by 168.6% in LRM model. By the other hand, the change of facet joint contact stress, IDP and stresses in capsular ligament in LLRM model were less than 11.5%. The differences of stresses on bone-screw interface and screw-plate system in C4,C5 between LRM and LLRM were less than 5.9 MPa (2.7%), but this value in C3 and C6 were up to 105.7 MPa (41.8%). Laminectomy without reconstruction of posterior ligament resulted larger mobility in the adjacent segments, which might induce spinal instability as postoperative complications. Repairing or preserving the posterior ligament in the lamina repair is benefit to spinal integrity and stability.
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Laminectomía , Fusión Vertebral , Fenómenos Biomecánicos , Vértebras Cervicales/cirugía , Fusión Vertebral/métodos , Ligamentos Articulares , Rango del Movimiento ArticularRESUMEN
Orthopedic implants are widely used for the treatment of bone defects caused by injury, infection, tumor and congenital diseases. However, poor osseointegration and implant failures still occur frequently due to the lack of direct contact between the implant and the bone. In order to improve the biointegration of implants with the host bone, surface modification is of particular interest and requirement in the development of implant materials. Implant surfaces that mimic the inherent surface roughness and hydrophilicity of native bone have been shown to provide osteogenic cells with topographic cues to promote tissue regeneration and new bone formation. A growing number of studies have shown that cell attachment, proliferation and differentiation are sensitive to these implant surface microtopography. This review is to provide a summary of the latest science of surface modified bone implants, focusing on how surface microtopography modulates osteoblast differentiation in vitro and osseointegration in vivo, signaling pathways in the process and types of surface modifications. The aim is to systematically provide comprehensive reference information for better fabrication of orthopedic implants.
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BACKGROUND AND OBJECTIVE: Hybrid surgery, incorporating cervical disc replacement and anterior cervical discectomy and fusion, has shown good clinical results in the treatment of multilevel cervical spondylosis according to early follow-ups. This study investigated the surgical strategy of hybrid surgery for two-level cervical spondylosis by distinguishing the biomechanical characteristics with different incorporating modes. METHOD: A finite element model of a healthy cervical spine including C2-T1 was developed, and hybrid surgery was simulated by replacing at one level with Prestige-LP and fusion at another level with the anterior plate in C3-C5 (Hybrid-S1: replaced at C3-C4, Hybrid-S2: replaced at C4-C5), and in C4-C6 (Hybrid-M1: replaced at C4-C5, Hybrid-M2: replaced at C5-C6) and in C5-C7 (Hybrid-U1: replaced at C5-C6, Hybrid-U2: replaced at C6-C7). The motion of C2 vertebrae in flexion, extension, axial rotation, and lateral bending was imposed on all hybrid models following the displacement control testing protocol. RESULTS: The largest range of motion (ROM) in a healthy spine was observed at C5-C6, followed by C3-C4, C4-C5 and C6-C7. On average, the ROM at the replaced segment increased by 175.7%, 202.7%, 176.3%, 117.1%, 139.4%, and 236.0% in Hybrid-S1, Hybrid-S2, Hybrid-M1, Hybrid-M2, Hybrid-U1, and Hybrid-U2, respectively. The facet joint stress at the replaced segment increased by 186.9%, 124.4%, 111.1%, 60.3%, 62.7%, and 144.7%, and the adjacent intradiscal pressure (IDP) increased by 45.2%, 38.7%, 2.7%, 2.1%, 13.9%, and 20.1%. CONCLUSIONS: Incorporating mode in hybrid surgery affects cervical biomechanics. Hybrid surgery with replacement at a segment with a greater ROM and fusion at a segment with a lower ROM can results in fewer changes in terms of overall cervical stiffness, ROM at the operative level, facet joint stress, and adjacent IDP. In hybrid surgery, it is better to implement disc replacement at a level with a greater ROM and fusion of another segment.
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Espondilosis , Humanos , Fenómenos Biomecánicos , Vértebras Cervicales/cirugía , Discectomía/métodos , Rango del Movimiento Articular , Espondilosis/cirugíaRESUMEN
Understanding the effects of sloped roads in the pedestrian environment on the body during ambulation with a walking frame can help design friendlier living environments for elderly individuals. A survey of the characteristics of walking frames used in different pedestrian environments was investigated in five communities, and a controlled study of the effects of a sloped road on a subject with different walking frames was carried out as foundational research in the laboratory. A synchronous acquisition system consisting of a wireless motion capture module and a physiological information recording module was applied to collect data on the motion of the shoulder joint and skin conductance response (SCR) of fingers in one participant. Force data were collected from sensors placed on the four legs of the walking frame. The experimental data obtained during different tasks were quantitatively analyzed. Compared to flat ground, the shoulder joint rotated in the opposite direction in horizontal and internal/external planes when using a wheeled walking frame on an uphill road, and the supportive force decreased on both uphill and downhill roads. The range of motion of the shoulder joint reduced and the direction of the shoulder joint motion changed when using a footed walking frame on both uphill and downhill roads. Additionally, the peak value of the supportive force on the uphill road appeared in the first 50% of the gait cycle, which was earlier than in the other cases. In addition, walking on the uphill road with a walking frame had a maximum SCR value, which means a greater impact of psychological arousal. Biomechanics of the shoulder joint and psychological arousal are closely related to the ease of walking on a sloped road with a walking frame. These findings are beneficial for designing more appropriate environments for elderly individuals who walk with aids.
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Peatones , Anciano , Fenómenos Biomecánicos , Marcha/fisiología , Humanos , Extremidad Inferior/fisiología , Caminata/fisiologíaRESUMEN
Multi-level spinal fusion has been reported in some cases to lead to adjacent segment disease (ASD) and proximal junctional kyphosis (PJK). The purpose of this study was to demonstrate a polyether-ether-ketone (PEEK) rod fixation system implanted adjacent to a two-level lumbar fusion would have a lower risk of PJK than three-level lumbar fusion, which was investigated by comparing the biomechanical effects on the adjacent level after surgical procedures. Four finite element (FE) models of the lumbar-sacral spine (intact model (INT), L4-S1 fusion model (L4-S1 FUS), L3-S1 fusion model (L3-S1 FUS), and single-level PEEK rod semi-rigid fixation adjacent to L4-S1 fusion model (FUSPRF)) were established. Displacement-controlled finite element (FE) analysis was used during the simulation. Compared with the two-level fusion model (L4-S1 FUS), both three-level implanted models (L3-S1 FUS and FUSPRF) showed an increase intersegmental rotation angle, and maximum von-Mises stress on the disc annulus. The results also showed that the intersegmental rotation, stress on the disc annulus and maximum stress on the rod were lower in the FUSPRF model than the L3-S1 FUS model. Though the maximum screw stress was higher in the FUSPRF model than the L3-S1 FUS model under all moments except for torsion, the maximum screw stress in the two models were far below the yield strength of titanium alloy. As the parameters above have been indicated as risk factors for PJK, it can be concluded that hybrid single-level PEEK rod semi-rigid fixation and two-level lumbar fusion have a lower risk of PJK than three-level lumbar fusion.
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Fusión Vertebral , Fenómenos Biomecánicos , Análisis de Elementos Finitos , Vértebras Lumbares/diagnóstico por imagen , Vértebras Lumbares/cirugía , Región Lumbosacra , Rango del Movimiento Articular , Fusión Vertebral/métodosRESUMEN
Ankle sprain is the most common injury during parachute landing. The biomechanical behavior of the tissues can help us understand the injury mechanism of ankle inversion. To accurately describe the injury mechanism of tissues and assess the effect of ankle protection, a stable time of landing was obtained through the dynamic stability test. It was used for the boundary condition of the foot finite element (FE). The FE model was provided a static load equal to half of the bodyweight applied at the distal tibia and fibula; a foot-boot-brace FE model was established to simulate the landing of subjects on an inversion inclined platform of 0-20°, including non-, external, and elastic ankle braces. Compared with the non-ankle brace, both the external and elastic ankle braces decreased the peak strains of the cal-fibular, anterior Ta-fibular, and posterior Ta-fibular ligaments (15.2-33.0%), and of the peak stress of the fibula (15.2-24.5%). For the strain decrement of the aforementioned ligaments, the elastic brace performed better than the external ankle brace under the inversion of the 10° condition. The peak stress of the fibula (15.6 MPa) decreased up to 24.5% with an elastic brace and 5.6-10.3% with an external brace. The findings suggested that the behaviors of lateral ankle ligaments and fibula were meaningful for the functional ability of the ankle. This provides some suggestions regarding the optimal design of ankle protection.
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Personalized plates (P-Plates) could provide improved clinical outcomes in joint fusion by enabling perfect geometric matching between irregular bone and implants. However, there is no unified application framework for P-Plates for joint fusion. The objective of this study was to develop such a framework for P-Plates for tibiotalocalcaneal arthrodesis. A patient-specific bone model was constructed based on CT images, and the P-Plate was preliminarily designed to match the bones. Finite element method was used to optimize the stress distribution and to evaluate the biomechanical performance of the P-Plate by comparing it with a traditional plate (T-Plate). Then, the P-Plate was manufactured via electron beam melting and implanted into the foot of a patient. Increasing the size of the preliminary designed plate alleviated the stress concentration and reduced the risk of failure. The maximum stresses of the plate and screw (214.3 MPa, 99.05 MPa) and the maximum tensile force of the screw in the P-Plate (181.4 N) fixation system were lower than those in the T-Plate (217.4 MPa, 255.4 MPa, and 230.1 N, respectively). The P-Plate was well-matched to the bone, and no complications occurred. The P-Plate achieved American Orthopaedic Foot & Ankle Society and Short-Form-36 scores of 64 and 75, respectively, 36 months post operation, which suggests that it could improve clinical outcomes. The design and fabrication methods, as well as mechanical and postoperative performance evaluation methods, for the P-Plate were systematically developed and provide a reference for constructing a unified application framework for P-Plate use in tibiotalocalcaneal arthrodesis.
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Artrodesis , Placas Óseas , Fenómenos Biomecánicos , Tornillos Óseos , Humanos , Impresión TridimensionalRESUMEN
OBJECTIVE: To analyze the characteristics of foot and ankle deformity with ulceration in patients with spina bifida, to conclude experiences on management with improved Ilizarov method in one stage. METHODS: 77 cases suffering foot and ankle deformity with ulceration of spina bifida were included from January 2008 to June 2019, in which 30 male and 47 female, aged 6-46 years with an average age of 22.86 years. There were 10 cases on left, 14 on right and 53 on both. The improved Ilizarov method combined soft tissue surgery, bone osteotomy and Ilizarov technique in one stage, by which the ulcer was dressed aseptically and avoid weight bearing preoperatively, no special treatment, no debridement, no flap coverage and no bacterial culture. Antibiotics were given for 3 days routinely, and the dressing was removed 5 days later. If there was exudation, gauze could be used to wrap continually, if there was no swelling and exudation, no need further more caring. General appearance and radiological image of ulcer and deformity were observed during the period of evaluation and treatment, surgical method and complications, foot & ankle function and overall function were evaluated using AOFAS scoring system and special table designed by authors. RESULTS: 77 cases were followed up for 6-132 months with an average of 50.5 months. Achilles tendon subcutaneous lengthening was performed in 2 cases, posterior tibial tendon and Achilles tendon simultaneous released for 31cases, subtalar joint arthrodesis 25 cases, calcaneus osteotomy 5 cases, triple osteotomy 28 cases, ankle arthrodesis 19 cases, internal rotation osteotomy of tibia was performed in 1 case and 1 case in external rotation osteotomy. There were 67 cases using Ilizarov fixators and 10 cases using Hybrid fixators for immobilization and correction. Stable feet were obtained and ulcers healed simultaneously when all deformities of foot and ankle had been corrected. The healing time of ulcer was average 26.5 days ranging 7-36 days, and there was no infection or delayed healing occurred in any case. Ankle ankylosis in 25 cases, 3 cases of pin tract infection, 2 wires were broken. The AOFAS score significantly increased from 70.5 ± 4.5 preoperative to 81.6 ± 3.9 postoperative; based special table evaluating, Excellent 28 cases, Good 42 cases, Fair7 cases. CONCLUSION: The patients with foot & ankle deformity and ulceration suffered from spinal bifida can be treated by improved Ilizarov method in one stage, and the results are satisfactory with short treatment period and decreased complications. TRANSLATIONAL POTENTIAL OF THIS ARTICLE: The characteristics of foot and ankle deformity with ulceration inpatients with spina bifida have been analyzed and the experiences on management with improved Ilizarovmethod in one stage have been summarized in this study, which updated treatment concept of neurogenic deformity with ulceration on foot and ankle joint.
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Anterior percutaneous endoscopic cervical discectomy (APECD) is a common treatment for cervical spondylotic radiculopathy (CSR). In this study, the effects of various channel diameters and approach angles on cervical vertebrae on postoperative outcomes in APECD surgery were explored. A finite element model of intact cervical C3-C7 was constructed and then modified to obtain six surgical models. Range of motion (ROM) and intradiscal pressure (IDP) were calculated under different conditions of flexion (Fle), extension (Ext), lateral bending, and axial rotation. During Fle and bending to the left (LB), the ROM was closer to the intact model when the angle of approach was 90°. During bending to the left (LB) and rotation to the left (LR), the ROM changed considerably (43.2%, 33.7%, respectively) where the angle of approach was 45°. As the surgical channel diameter increased, the extent of the change in ROM compared with the intact model also increased. IDP decreased by 48% and 49%, respectively, compared with the intact model at the C5-C6 segment where the angle of approach was 45° and 60° during Fle, while it changed little at 90°, by less than 10%. The IDP was increased noticeably by 117.6%, 82.1%, and 105.8%, for channel diameters of 2, 3 and 4 mm, respectively. And declined noticeably during LB and LR (LB: 27.1%, 27.1%, 38.5%; LR: 37.4%, 35.5%, 48.7%). The results demonstrated that the shorter the surgical path, the smaller surgical diameter, the less the biomechanical influence on the cervical vertebra.
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Vértebras Cervicales/cirugía , Discectomía , Endoscopía , Adulto , Fenómenos Biomecánicos , Calibración , Vértebras Cervicales/fisiopatología , Análisis de Elementos Finitos , Humanos , Masculino , Modelos Anatómicos , Presión , Rango del Movimiento Articular , Reproducibilidad de los ResultadosRESUMEN
Neck injury is one of the most frequent spine injuries due to the complex structure of the cervical spine. The high incidence of neck injuries in collision accidents can bring a heavy economic burden to the society. Therefore, knowing the potential mechanisms of cervical spine injury and dysfunction is significant for improving its prevention and treatment. The research on cervical spine dynamics mainly concerns the fields of automobile safety, aeronautics, and astronautics. Numerical simulation methods are beneficial to better understand the stresses and strains developed in soft tissues with investigators and have been roundly used in cervical biomechanics. In this article, the simulation methods for the development and application of cervical spine dynamic problems in the recent years have been reviewed. The study focused mainly on multibody and finite element models. The structure, material properties, and application fields, especially the whiplash injury, were analyzed in detail. It has been shown that simulation methods have made remarkable progress in the research of cervical dynamic injury mechanisms, and some suggestions on the research of cervical dynamics in the future have been proposed.
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Vértebras Cervicales/diagnóstico por imagen , Vértebras Cervicales/lesiones , Traumatismos del Cuello/fisiopatología , Lesiones por Latigazo Cervical/diagnóstico por imagen , Fenómenos Biomecánicos , Simulación por Computador , Femenino , Análisis de Elementos Finitos , Humanos , Procesamiento de Imagen Asistido por Computador/métodos , Incidencia , Masculino , Modelos Anatómicos , Modelos Teóricos , Cuello , Factores Sexuales , Estrés Mecánico , Vibración , Lesiones por Latigazo Cervical/fisiopatologíaRESUMEN
Follower loads are used to simulate physiological compressive loads on the human spine. These compressive loads represent the load-carrying capacity of the human cervical spine and play an important role in maintaining its stability. However, under different follower loads the biomechanical response of the cervical spine is unknown. Therefore, the aim of this study was to determine the effect of follower load on the biomechanics of the cervical spine. A three-dimensional nonlinear finite element (FE) model of the cervical spine (C3-C7) was developed and validated. Using this FE model, we evaluated the effect of different follower loads (0 N, 50 N, 100 N, and 150 N) on the range of motion (ROM), facet joint forces (FJFs), and intradiscal pressure (IDP) in the cervical spine. In addition, a moment of 1 Nm was applied in three anatomical planes (sagittal, coronal, and transverse planes) to simulate different postures. The results indicate that as follower load was increased, the ROM of the cervical spine in extension decreased (4.06°-0.95°), but increased in other postures (flexion 4.19°-6.04°, lateral bending 1.74-3.03°, axial rotation 2.64°-4.11°). Follower loads increased the FJF in all postures (0 N-52 N). In lateral bending (LB), FJFs were only generated in the ipsilateral facet joints. In axial rotation (AR), there was large asymmetry in the FJF, which increased as follower load increased. The IDP of each segment increased nonlinearly with increasing follower load in all postures (0.01 MPa-1.23 MPa). In summary, follower loads caused changes in motion and loading patterns in the cervical spine (C3-C7). Therefore, in common daily activities, we should pay attention to the muscle strength of the neck through exercise to adapt to the biomechanical changes in the cervical spine following an increase in follower load. Graphical Abstract Follower load is defined as the compressive load directed approximately along the axis of the spine. The purpose of this investigation was to determine the effect of the follower compressive load on biomechanics of the cervical spine. To do so, a three-dimensional nonlinear FE model of the cervical spine (C3-C7) was built and validated. Using this FE model of the cervical spine, we evaluated the effect of different follower loads (0 N, 50 N, 100 N, 150 N) on range of motion, facet joint force, and IDP in the cervical spine. In this study, the follower load was applied to the finite element model by connector elements. At the same time, a moment of 1 Nm was applied in the three anatomical planes to simulate different postures.
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Vértebras Cervicales/fisiología , Disco Intervertebral/fisiología , Rango del Movimiento Articular/fisiología , Articulación Cigapofisaria/fisiología , Adulto , Fenómenos Biomecánicos/fisiología , Análisis de Elementos Finitos , Humanos , Masculino , Fenómenos Mecánicos , Fuerza Muscular/fisiología , Postura/fisiología , Presión , Rotación , Soporte de Peso/fisiologíaRESUMEN
BACKGROUND: Quantitative areas is of great measurement of wound significance in clinical trials, wound pathological analysis, and daily patient care. 2D methods cannot solve the problems caused by human body curvatures and different camera shooting angles. Our objective is to simply collect wound areas, accurately measure wound areas and overcome the shortcomings of 2D methods. RESULTS: We propose a method with 3D transformation to measure wound area on a human body surface, which combines structure from motion (SFM), least squares conformal mapping (LSCM), and image segmentation. The method captures 2D images of wound, which is surrounded by adhesive tape scale next to it, by smartphone and implements 3D reconstruction from the images based on SFM. Then it uses LSCM to unwrap the UV map of the 3D model. In the end, it utilizes image segmentation by interactive method for wound extraction and measurement. Our system yields state-of-the-art results on a dataset of 118 wounds on 54 patients, and performs with an accuracy of 0.97. The Pearson correlation, standardized regression coefficient and adjusted R square of our method are 0.999, 0.895 and 0.998 respectively. CONCLUSIONS: A smartphone is used to capture wound images, which lowers costs, lessens dependence on hardware, and avoids the risk of infection. The quantitative calculation of the 3D wound area is realized, solving the challenges that 2D methods cannot and achieving a good accuracy.
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Teléfono Inteligente , Heridas y Lesiones/diagnóstico por imagen , Algoritmos , Humanos , Imagenología TridimensionalRESUMEN
Intermediate screw fixation at the fracture level has been widely accepted to treat thoracolumbar burst fractures, but no study has shown the effect of the extent and location of fixation. The effect of the extent and location of fixation on short- or long-segment pedicle screw fixation through intermediate screw fixation at the fracture level in the treatment of thoracolumbar burst fractures is discussed.Posterior intermediate screw fixation techniques in treating T12 vertebral fracture models were simulated and compared using finite element methods; the fixation techniques included M3-L1 (bilateral 3 monoaxial pedicle screw fixation from L1 to T11), M3-L2, M4-L1 (bilateral 4 monoaxial pedicle screw fixation from L1 to T10), M4-L2, M4-L3, and M5-L2 (bilateral 5 monoaxial pedicle screw fixation from L2 to T10). Range of motion (ROM) and largest von Mises stress (LVMS) of the instrumentations were recorded and analyzed.No significant differences were observed in the mean ROM of all states of motion between the M3-L1 model and the other fixation models except for M5-L2. The LVMS of the pedicle screws and rods all occurred during flexion. The LVMS values of the pedicle screws were larger in the M3-L2 fixation model and M4-L3 fixation model than in the other fixation models. The M3-L1 model presented a significantly smaller mean LVMS of the pedicle screws in all states of motion than the M3-L2 model (Pâ=â.026). The LVMS values of the rods were larger in the M3-L2 fixation model, M4-L3 fixation model, and M4-L2 fixation model than in the other fixation models. No significant differences were observed in the mean LVMS of the rods in all states of motion among all the fixation models.When choosing short-segment pedicle screw fixation with the screwing of fractured vertebrae to treat thoracolumbar fractures, we suggest M3-L1 over M3-L2. More severe injuries can be considered to identify an alternative treatment to long-segment monoaxial pedicle fixation constructs such as the M4-L1 and M5-L2 techniques.
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Fijación Interna de Fracturas/métodos , Tornillos Pediculares/efectos adversos , Fracturas de la Columna Vertebral/cirugía , Adulto , Fenómenos Biomecánicos , Análisis de Elementos Finitos , Humanos , Vértebras Lumbares/lesiones , Vértebras Lumbares/cirugía , Masculino , Rango del Movimiento Articular , Vértebras Torácicas/lesiones , Vértebras Torácicas/cirugía , Tomografía Computarizada EspiralRESUMEN
[This corrects the article DOI: 10.1155/2017/8614341.].
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OBJECTIVES: No studies have compared monoaxial and polyaxial pedicle screws with regard to the von Mises stress of the instrumentation, intradiscal pressures of the adjacent segment and adjacent segment degeneration. METHODS: Short-segment monoaxial/polyaxial pedicle screw fixation techniques were compared using finite element methods, and the redistributed T11-L1 segment range of motion, largest maximal von Mises stress of the instrumentation, and intradiscal pressures of the adjacent segment under displacement loading were evaluated. Radiographic results of 230 patients with traumatic thoracolumbar fractures treated with these fixations were reviewed, and the sagittal Cobb's angle, vertebral body angle, anterior vertebral body height of the fractured vertebrae and adjacent segment degeneration were calculated and evaluated. RESULTS: The largest maximal values of the von Mises stress were 376.8 MPa for the pedicle screws in the short-segment monoaxial pedicle screw fixation model and 439.9 MPa for the rods in the intermediate monoaxial pedicle screw fixation model. The maximal intradiscal pressures of the upper adjacent segments were all greater than those of the lower adjacent segments. The maximal intradiscal pressures of the monoaxial pedicle screw fixation model were larger than those in the corresponding segments of the normal model. The radiographic results at the final follow-up evaluation showed that the mean loss of correction of the sagittal Cobb's angle, vertebral body angle and anterior vertebral body height were smallest in the intermediate monoaxial pedicle screw fixation group. Adjacent segment degeneration was less likely to be observed in the intermediate polyaxial pedicle screw fixation group but more likely to be observed in the intermediate monoaxial pedicle screw fixation group. CONCLUSION: Smaller von Mises stress in the pedicle screws and lower intradiscal pressure in the adjacent segment were observed in the polyaxial screw model than in the monoaxial pedicle screw fixation spine models. Fracture-level fixation could significantly correct kyphosis and reduce correction loss, and adjacent segment degeneration was less likely to be observed in the intermediate polyaxial pedicle screw fixation group.
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Fijación Interna de Fracturas/instrumentación , Vértebras Lumbares/lesiones , Tornillos Pediculares , Fracturas de la Columna Vertebral/cirugía , Vértebras Torácicas/lesiones , Adulto , Análisis de Varianza , Fenómenos Biomecánicos , Diseño de Equipo , Femenino , Análisis de Elementos Finitos , Fijación Interna de Fracturas/métodos , Humanos , Vértebras Lumbares/diagnóstico por imagen , Vértebras Lumbares/fisiopatología , Masculino , Persona de Mediana Edad , Presión , Radiografía , Rango del Movimiento Articular , Reproducibilidad de los Resultados , Estudios Retrospectivos , Fracturas de la Columna Vertebral/diagnóstico por imagen , Fracturas de la Columna Vertebral/fisiopatología , Vértebras Torácicas/diagnóstico por imagen , Vértebras Torácicas/fisiopatología , Índices de Gravedad del Trauma , Resultado del TratamientoRESUMEN
Flat foot is one of the common deformities in the youth population, seriously affecting the weight supporting and daily exercising. However, there is lacking of quantitative data relative to material selection and shape design of the personalized orthopedic insole. This study was to evaluate the biomechanical effects of material hardness and support height of personalized orthopedic insole on foot tissues, by in vivo experiment and finite element modeling. The correction of arch height increased with material hardness and support height. The peak plantar pressure increased with the material hardness, and these values by wearing insoles of 40° were apparently higher than the bare feet condition. Harder insole material results in higher stress in the joint and ligament stress than softer material. In the calcaneocuboid joint, the stress increased with the arch height of insoles. The material hardness did not apparently affect the stress in the ankle joints, but the support heights of insole did. In general, insole material and support design are positively affecting the correction of orthopedic insole, but negatively resulting in unreasonable stress on the stress in the joint and ligaments. There should be an integration of improving correction and reducing stress in foot tissues.
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Pie Plano/fisiopatología , Pie Plano/rehabilitación , Ortesis del Pié , Pie/fisiopatología , Ortopedia/métodos , Articulación del Tobillo/fisiopatología , Cartílago/fisiopatología , Niño , Simulación por Computador , Diseño de Equipo , Análisis de Elementos Finitos , Dureza , Humanos , Ligamentos/fisiopatología , Masculino , Presión , Zapatos , Programas Informáticos , Estrés Mecánico , Tomografía Computarizada por Rayos XRESUMEN
OBJECTIVES: No studies have compared monoaxial and polyaxial pedicle screws with regard to the von Mises stress of the instrumentation, intradiscal pressures of the adjacent segment and adjacent segment degeneration. METHODS: Short-segment monoaxial/polyaxial pedicle screw fixation techniques were compared using finite element methods, and the redistributed T11-L1 segment range of motion, largest maximal von Mises stress of the instrumentation, and intradiscal pressures of the adjacent segment under displacement loading were evaluated. Radiographic results of 230 patients with traumatic thoracolumbar fractures treated with these fixations were reviewed, and the sagittal Cobb's angle, vertebral body angle, anterior vertebral body height of the fractured vertebrae and adjacent segment degeneration were calculated and evaluated. RESULTS: The largest maximal values of the von Mises stress were 376.8 MPa for the pedicle screws in the short-segment monoaxial pedicle screw fixation model and 439.9 MPa for the rods in the intermediate monoaxial pedicle screw fixation model. The maximal intradiscal pressures of the upper adjacent segments were all greater than those of the lower adjacent segments. The maximal intradiscal pressures of the monoaxial pedicle screw fixation model were larger than those in the corresponding segments of the normal model. The radiographic results at the final follow-up evaluation showed that the mean loss of correction of the sagittal Cobb's angle, vertebral body angle and anterior vertebral body height were smallest in the intermediate monoaxial pedicle screw fixation group. Adjacent segment degeneration was less likely to be observed in the intermediate polyaxial pedicle screw fixation group but more likely to be observed in the intermediate monoaxial pedicle screw fixation group. CONCLUSION: Smaller von Mises stress in the pedicle screws and lower intradiscal pressure in the adjacent segment were observed in the polyaxial screw model than in the monoaxial pedicle screw fixation spine models. Fracture-level fixation could significantly correct kyphosis and reduce correction loss, and adjacent segment degeneration was less likely to be observed in the intermediate polyaxial pedicle screw fixation group.
Asunto(s)
Humanos , Masculino , Femenino , Adulto , Persona de Mediana Edad , Vértebras Torácicas/lesiones , Fracturas de la Columna Vertebral/cirugía , Tornillos Pediculares , Fijación Interna de Fracturas/instrumentación , Vértebras Lumbares/lesiones , Presión , Vértebras Torácicas/fisiopatología , Vértebras Torácicas/diagnóstico por imagen , Fenómenos Biomecánicos , Radiografía , Índices de Gravedad del Trauma , Reproducibilidad de los Resultados , Estudios Retrospectivos , Análisis de Varianza , Rango del Movimiento Articular , Fracturas de la Columna Vertebral/fisiopatología , Fracturas de la Columna Vertebral/diagnóstico por imagen , Resultado del Tratamiento , Análisis de Elementos Finitos , Diseño de Equipo , Fijación Interna de Fracturas/métodos , Vértebras Lumbares/fisiopatología , Vértebras Lumbares/diagnóstico por imagenRESUMEN
BACKGROUND: Finite element models have been widely used to predict biomechanical parameters of the cervical spine. Previous studies investigated the influence of position of rotational centers of prostheses on cervical biomechanical parameters after 1-level total disc replacement. The purpose of this study was to explore the effects of axial position of rotational centers of prostheses on cervical biomechanics after 2-level total disc replacement. METHODS: A validated finite element model of C3-C7 segments and 2 prostheses, including the rotational center located at the superior endplate (SE) and inferior endplate (IE), was developed. Four total disc replacement models were used: 1) IE inserted at C4-C5 disc space and IE inserted at C5-C6 disc space (IE-IE), 2) IE-SE, 3) SE-IE, and 4) SE-SE. All models were subjected to displacement control combined with a 50 N follower load to simulate flexion and extension motions in the sagittal plane. For each case, biomechanical parameters, including predicted moments, range of rotation at each level, facet joint stress, and von Mises stress on the ultra-high-molecular-weight polyethylene core of the prostheses, were calculated. RESULTS: The SE-IE model resulted in significantly lower stress at the cartilage level during extension and at the ultra-high-molecular-weight polyethylene cores when compared with the SE-SE construct and did not generate hypermotion at the C4-C5 level compared with the IE-SE and IE-IE constructs. CONCLUSIONS: Based on the present analysis, the SE-IE construct is recommended for treating cervical disease at the C4-C6 level. This study may provide a useful model to inform clinical operations.