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PURPOSE: To evaluate the changes in contact characteristics of the tibiofemoral joint resulting from a meniscal ramp lesion in the medial meniscus. METHODS: Twelve cadaveric knees (six matched pairs) were subjected to a 600 N axial load using a custom testing jig, which allowed for knee positioning at 0°, 45°, and 90° of flexion without other constraints. The knees were randomly assigned to either a ramp lesion group (n = 6) or a posterior root lesion group (n = 6). Four testing conditions were examined: (1) intact, (2) isolated ramp lesion, (3) isolated posterior root tear of the medial meniscus, and (4) combined ramp lesion and posterior root tear of the medial meniscus. Contact characteristics were evaluated using a flexible pressure sensor, the I-Scan System. RESULTS: Peak contact pressure in isolated ramp lesions (4.15 ± 0.98 MPa, P = 0.206) showed non-significant increases compared to the intact condition (3.86 ± 1.32 MPa). Peak contact pressure in isolated posterior root tears (4.58 ± 1.70 MPa, P = 0.040) and, combined ramp and posterior root lesions (4.67 ± 1.47 MPa, P = 0.003) were significantly higher than that in the intact condition. The knee flexion position significantly affected the medial tibiofemoral joint's contact area, contact pressure, and peak contact pressure (P < 0.001 for all). CONCLUSION: Isolated ramp lesions did not significantly impact force transmission, contact area, or contact pressure. In contrast, isolated root lesions and combined ramp and posterior root tears of the medial meniscus significantly intensified the changes in contact characteristics in the medial tibiofemoral joint compared to the intact condition. LEVEL OF EVIDENCE: Level III.
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Cadáver , Articulação do Joelho , Meniscos Tibiais , Lesões do Menisco Tibial , Humanos , Lesões do Menisco Tibial/fisiopatologia , Lesões do Menisco Tibial/cirurgia , Fenômenos Biomecânicos , Articulação do Joelho/fisiopatologia , Meniscos Tibiais/fisiopatologia , Meniscos Tibiais/cirurgia , Masculino , Lesões do Ligamento Cruzado Anterior/fisiopatologia , Lesões do Ligamento Cruzado Anterior/cirurgia , Pessoa de Meia-Idade , Feminino , Idoso , Suporte de Carga/fisiologia , PressãoRESUMO
PURPOSE: This study aimed to investigate the optimal tension for the reconstruction of the distal radioulnar ligaments (DRULs) in the treatment of the distal radioulnar joint (DRUJ) instability. METHODS: A total of eight human cadaver upper extremities were used. First, the Tekscan sensor film system was used to measure the contact characteristics of the intact DRUJ. Following this, the DRULs were resected, and the measurement was repeated. The DRULs were then reconstructed according to Adams' procedure, and the contact forces under different initial tension were compared with that of the intact group to obtain the optimal tension. At that point, the contact force of the DRUJ was close to normal. The reliability of the obtained tension was verified by translational testing, which reflected the stability of the DRUJ. RESULTS: In the neutral position, the contact force, area, and pressure inside DRUJ were 0.51 ± 0.10 N, 64.08 ± 11.58 mm2, and 8.33 ± 2.42 kPa, respectively. After the DRULs were resected, they were 0.19 ± 0.02 N, 41.75 ± 5.01 mm2, and 4.86 ± 1.06 kPa, respectively. The relationship between the tension and contact force was linear regression (Y = 0.0496x + 0.229, R2 = 0.9575, P < 0.0001). According to the equation, when the tension was 3.64-7.68 N, the contact force was close to normal. There was no statistical difference in the stability of the reconstructed DRUJ under this tension compared with the intact group (P = 0.08). CONCLUSION: By comparing the contact forces under different reconstruction tensions with the normal value, we obtained the optimal tension, which can provide the theoretical basis for the clinical treatment of chronic DRUJ instability.
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Instabilidade Articular , Ulna , Fenômenos Biomecânicos , Cadáver , Humanos , Instabilidade Articular/cirurgia , Ligamentos , Rádio (Anatomia)/cirurgia , Reprodutibilidade dos Testes , Ulna/cirurgia , Articulação do Punho/cirurgiaRESUMO
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.
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Artroplastia do Joelho/métodos , Prótese do Joelho , Patela/cirurgia , Articulação Patelofemoral/cirurgia , Desenho de Prótese , Suporte de Carga/fisiologia , Estudos de Casos e Controles , Análise de Elementos Finitos , Humanos , Modelos Anatômicos , Articulação Patelofemoral/fisiopatologia , Polietileno , Estresse MecânicoRESUMO
PURPOSE: To determine whether distal radioulnar joint (DRUJ) contact characteristics were altered in patients with malunited distal radius fractures. METHODS: We obtained computed tomography scans at 5 positions of both wrists of 6 patients who had unilateral malunited distal radius fractures with dorsal angulation from 10° to 20° and ulnar variance less than 3 mm. We reconstructed 3-dimensional images and mapped contact regions of DRUJ by calculating the shortest distance between the 2 opposing bones. The contact areas of the DRUJ were measured and the contact region centers were calculated and analyzed. The values of the malunited side were compared with those of the contralateral uninjured side. RESULTS: In the uninjured wrist, the contact areas of the DRUJ increased slightly from wrist flexion to extension and ulnar deviation. In the malunited wrist, we found the contact areas of DRUJ to be progressively reduced from 20° flexion to neutral, 40° extension, and 20° extension, to ulnar deviation. The centroid of this area on the sigmoid notch moved to distal from flexion to extension. Compared with the contralateral uninjured wrist, the contact area significantly decreased during wrist extension and ulnar deviation, and significantly increased during wrist flexion. The centroids of this area on sigmoid notch all moved volarly in all selected wrist positions. CONCLUSIONS: The contact areas of the DRUJ and the centroid of contact area on sigmoid notch are altered in patients with malunited distal radius fractures. The contact area of the DRUJ increases during wrist flexion and decreases during wrist extension and ulnar deviation. The centroids of the contact area on sigmoid notch move volarly during wrist flexion-extension and ulnar deviation. CLINICAL RELEVANCE: The in vivo findings suggest that alterations in joint mechanics may have an important role in the dysfunction associated with these injuries.
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Fraturas Mal-Unidas/fisiopatologia , Fraturas do Rádio/fisiopatologia , Rádio (Anatomia)/fisiopatologia , Ulna/fisiopatologia , Articulação do Punho/fisiopatologia , Idoso , Fenômenos Biomecânicos , Feminino , Fraturas Mal-Unidas/diagnóstico por imagem , Humanos , Imageamento Tridimensional , Masculino , Pessoa de Meia-Idade , Rádio (Anatomia)/diagnóstico por imagem , Amplitude de Movimento Articular/fisiologia , Tomografia Computadorizada por Raios X , Ulna/diagnóstico por imagem , Articulação do Punho/diagnóstico por imagemRESUMO
An improved understanding of contact mechanics in the ankle joint is paramount for implant design and ankle disorder treatment. However, existing models generally simplify the ankle joint as a revolute joint that cannot predict contact characteristics. The current study aimed to develop a novel musculoskeletal ankle joint model that can predict contact in the ankle joint, together with muscle and joint reaction forces. We modelled the ankle joint as a multi-axial joint and simulated contact mechanics between the tibia, fibula and talus bones in OpenSim. The developed model was validated with results from experimental studies through passive stiffness and contact. Through this, we found a similar ankle moment-rotation relationship and contact pattern between our study and experimental studies. Next, the musculoskeletal ankle joint model was incorporated into a lower body model to simulate gait. The ankle joint contact characteristics, kinematics, and muscle forces were predicted and compared to the literature. Our results revealed a comparable peak contact force and the same muscle activation patterns in four major muscles. Good agreement was also found in ankle dorsi/plantar-flexion and inversion/eversion. Thus, the developed model was able to accurately model the ankle joint and can be used to predict contact characteristics in gait.
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Articulação do Tornozelo , Tornozelo , Articulação do Tornozelo/fisiologia , Marcha/fisiologia , Extremidade Inferior , Músculos , Fenômenos BiomecânicosRESUMO
OBJECTIVES: The objective of this study was to analyze the occlusal contact characteristics of the food-impacted teeth using a new digital technique. METHODS: A 3D occlusal analysis method was developed for studying the occlusal contact characteristics of teeth affected by food impaction. In this self-controlled study, food-impacted molars from 20 participants constituted the experimental group. The corresponding healthy teeth on the opposite side served as the control group. Variables such as occlusal force (OF), occlusal contact area (OCA), and the number and distribution of occlusal contact points (OCN) in the mesio-distal directions were measured and compared between the two groups. RESULTS: There was no statistical significant difference in the values of OF, OCA and OCN between the food-impacted molars and the healthy control molars (P > 0.05). However, paired T-tests indicated significant difference in the proportion of mesial OF, OCA, and OCN in the second molars of the experimental group (0.22, 0.28 and 0.28, respectively) and the control group (0.66, 0.63, and 0.63 respectively) (P < 0.001). CONCLUSIONS: The abnormal distribution of occlusal contacts in the second molar, primarily characterized by excessive occlusal contact in the distal direction may contribute to the occurrence of food impaction. CLINICAL SIGNIFICANCE: The present study identified variations in the distribution of occlusal contacts and occlusal component force in food-impacted teeth. These findings can assist dentists in making more targeted occlusal adjustments, or applying other treatment modalities, to effectively address food impaction.
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Força de Mordida , Alimentos , Dente Molar , Dente Impactado , Humanos , Feminino , Masculino , Adulto Jovem , Adulto , Dente Impactado/diagnóstico por imagem , Oclusão Dentária , Imageamento Tridimensional/métodosRESUMO
To reveal the influence of surface morphology characteristics in mixed lubrication on the contact characteristics of the rolling interface, a random three-dimensional rough surface model based on Gaussian distribution theory was established. The model utilizes the finite element method (FEM) to simulate the regular contact and tangential sliding behavior of micro-asperities at the rolling interface in mixed lubrication conditions. The connection bearing capacity of models with varied roughness in mixed lubrication was studied. Furthermore, the effect of various sliding and normal indentation amounts on the normal and friction stress was investigated. The simulation result reveals that the roughness of the surface influences the distribution of the lubricating oil film. The lubricating oil layer between the interfaces with a lower roughness has a higher bearing capacity due to its more uniform distribution of peaks and valleys. An increase in the normal indentation amount raises the friction stress and normal stress. In contrast, an increase in sliding lowers the normal pressure, substantially impacting the fluctuation of the friction coefficient dramatically. Finally, the random three-dimensional rough surface model is verified by comparing it with the experimental data in the related literature.
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Compared with conventional drilling (CD), ultrasonic vibration-assisted drilling(UVAD) is experimentally proven a promising method to reduce the cutting temperature. But sometimes cutting temperature also becomes higher in UVAD than in CD. To further make clear the cutting temperature mechanisms in UVAD, this study aims to study the effect of tool's ultrasonic vibration on the cutting heat generation and heat dissipation at a relatively micro level. Firstly, drilling experiments are designed to explore the variations of cutting heat under different ultrasonic vibrations. Then, to analyze the influence of ultrasonic vibration on the cutting heat theoretically, a kinematic model is developed to describe the dynamic contact between the cutting edge and workpiece in UVAD. Besides, a cutting heat analysis model based on the contact characteristics in UVAD is proposed to study and compare the variations of cutting heat generation. The effect of ultrasonic vibration on the cutting heat generation, heat dispassion, and the resultant cutting temperature under different machining in UVAD conditions are discussed. It is indicated from the theoretical analysis that more cutting heat tends to be produced due to the significantly increased sliding velocity on the cutting edge-workpiece interface when the ultrasonic vibration is applied. The analysis agrees with the experimental results that the cutting temperature in dry UVAD is higher than in dry CD. But on the other hand, ultrasonic vibration can also improve the lubrication and cooling effect under appropriate machining conditions, which is beneficial to the reduction in cutting temperature. The investigation shows the multifaceted influences of ultrasonic vibration on the cutting temperature in the drilling process in detail, which provides a reference for UVAD parameter optimization.
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In this paper, laser texturing is performed on the surface of Mn-Cu and Fe-Zn damping alloys and the tribological properties of the samples with various surface weaves under dry-sliding conditions are investigated. The results show that the surface weave parameters affect the size of the contact surface and change the number of micro-convex bodies at the contact interface. This leads to changes in the tangential damping of the contact and further affects the magnitude of the friction coefficient. Additionally, the damping properties significantly affect the wear mechanism and make it more prone to adhesive wear.
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Anodic bonding is broadly utilized to realize the structure support and electrical connection in the process of fabrication and packaging of MEMS devices, and the mechanical and electrical characteristics of the bonded interface of structure exhibit a significant impact on the stability and reliability of devices. For the anodic bonding structure, including the gold electrode of micro accelerometers, the elastic/plastic contact model of a gold-silicon rough surface is established based on Hertz contact theory to gain the contact area and force of Gauss surface bonding. The trans-scale finite element model of a silicon-gold glass structure is built in Workbench through the reconstruction of Gauss surface net by the reverse engineering technique. The translation load is added to mimic the process of contact to acquire the contact behaviors through the coupling of mechanical and electrical fields, and then the change law of contact resistance is obtained. Finally, the measurement shows a good agreement between the experimental results, theoretical analysis and simulation, which indicates there is almost no change of resistance when the surface gap is less than 20 nm and the resistance is less than 5Ω, while the resistance changes rapidly after the gap exceeds 20 nm.
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Talus implants can be utilized in cases of talus avascular necrosis and has been regarded as a promising treatment method. However, existing implants are made of stiff materials that directly oppose natural cartilage. The risk of long-term cartilage wear and bone fracture from the interaction between the cartilage and stiff implant surfaces has been documented in post-hemiarthroplasty of the hip, knee and ankle joints. The aim is to explore the effects of adding a layer of compliant material (polycarbonate-urethane; PCU) over a stiff material (cobalt chromium) in talus implants. To do so, we obtained initial ankle geometry from four cadaveric subjects in neutral standing to create the finite element models. We simulated seven models for each subject: three different types of talus implants, each coated with and without PCU, and a biological model. In total, we constructed 28 finite element models. By comparing the contact characteristics of the implant models with their respective biological model counterparts, our results showed that PCU coated implants have comparable contact area and contact pressure to the biological models, whereas stiff material implants without the PCU coating all have relatively higher contact pressure and smaller contact areas. These results confirmed that adding a layer of compliant material coating reduces the contact pressure and increases the contact area which in turn reduces the risk of cartilage wear and bone fracture. The results also suggest that there can be clinical benefits of adding a layer of compliant material coating on existing stiff material implants, and can provide valuable information towards the design of more biofidelic implants in the future.
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Tálus , Uretana , Humanos , Cimento de PolicarboxilatoRESUMO
Customized talus implants have been regarded as a better treatment alternative to talus avascular necrosis than traditional surgical fusion because of its ability to maintain joint mobility while ameliorating pain. Despite the use of ankle hemiarthroplasty clinically, the cartilage contact characteristics of adjacent bones remain unclear. This study aims to use finite element modeling to evaluate the contact characteristics of three types of cobalt-chrome talus implants in three postures, in four subjects. This study also compared the contact area, contact pressure, and peak contact pressure of the implant models with a reference biological model. Among the various biological and implant models, our results showed that the biological models generally had the largest contact areas and smallest peak contact pressures, whereas the implant-type models had smaller contact areas and relatively larger peak contact pressure. Moreover, among the three implant types, customized-scale models showed a larger total contact area than that of the SSM-scale and universal-scale models, but their variation was relatively limited. The results from this study can have significance in future endeavors into ankle joint modeling, as well as being able to improve implant design to enhance recovery outcomes for patients who may benefit from talar replacement.
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Articulação do Tornozelo , Tálus , Tornozelo , Articulação do Tornozelo/cirurgia , Análise de Elementos Finitos , Humanos , Amplitude de Movimento Articular , Tálus/cirurgiaRESUMO
BACKGROUND: Motion axial system may affect contact stress of hinge knee prosthesis. However, it is unclear which axial system provides the better biomechanical effect. Therefore, the aim of this study was to compare the contact stress and stress distribution on the tibial insert and the bushing of hinge knee prostheses with a biaxial (BA) system and a spherical center axial (SA) system during a gait cycle. METHODS: Three-dimensional finite-element (FE) models of the prostheses with different motion systems were included. The comparisons between experimental tests and FE analyses were performed to verify the models. Dynamic implicit FE analyses were performed to investigate the peak contact stresses and stress distributions on the tibial insert and the bushing. RESULTS: The peak contact stresses on the tibial insert and the bushing of the BA prosthesis were higher than those of the SA prosthesis during most gait cycles. The contact time on the bushing is short in the SA prosthesis. The stress distributions on the superior surface of the tibial insert in the BA prosthesis were at the posterior side, but of the SA prosthesis were not fixed. CONCLUSION: The SA prosthesis has a lower peak contact stress on tibial insert and bushing than the BA prosthesis; in addition, the SA prosthesis has a 'self-adjustment' mechanism which could disperse high stress on the tibial insert to decrease the risk of wear and damage. The comparison could help designers and surgeons to better understand the future design of rotating hinge knee prostheses which should be able to achieve multiaxial motion and complete weight bearing by the tibial condylar to transmit the axial force better.
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Artroplastia do Joelho/instrumentação , Prótese do Joelho , Fenômenos Biomecânicos , Análise de Elementos Finitos , Marcha , Humanos , Articulação do Joelho/fisiopatologia , Articulação do Joelho/cirurgia , Desenho de Prótese , Amplitude de Movimento Articular , Estresse Mecânico , Tíbia/cirurgia , Suporte de CargaRESUMO
BACKGROUND: The transosseous-equivalent (TOE) rotator cuff repair construct has become the gold standard for the repair of medium and large rotator cuff tears. Repair failure, however, continues to be a problem. One contributing factor may be the inability of the TOE repair to replicate the native footprint contact characteristics during shoulder movement, especially in rotation. This results in higher strain across the repair, which leads to gapping and predisposes the construct to failure. In an effort to better reproduce the native compression forces throughout the footprint, an augmented TOE construct supplemented with lateral edge fixation is proposed, and the contact characteristics were compared with those of the gold standard TOE construct. HYPOTHESIS: The augmented TOE repair will demonstrate improved footprint contact characteristics when compared with the classic TOE repair. STUDY DESIGN: Controlled laboratory study. METHODS: Ten fresh-frozen cadaveric shoulders underwent supraspinatus repair using both the classic TOE double-row construct and the augmented TOE repair. For the augmented repair, 2 luggage tag sutures were used to secure the lateral edge and incorporated into the lateral row anchors. A Tekscan pressure sensor (Tekscan Inc) placed under the repaired tendon was used to collect footprint contact area, force, peak pressure, and contact pressure data for each construct. RESULTS: The augmented construct demonstrated significantly greater contact forces (average difference, 4.9 N) and significantly greater contact pressures (average difference, 23.1 kPa) at all degrees of abduction and all degrees of rotation. At 30° of internal and 30° of external rotation at both 0° and 30° of shoulder abduction, the augmented construct demonstrated significantly greater peak contact pressures. CONCLUSION: The augmented construct showed superior contact characteristics when compared with the classic TOE technique. The addition of lateral edge fixation to the classic TOE repair significantly improves bone-tendon contact characteristics with minimal additional surgical effort. CLINICAL RELEVANCE: The results of this study indicate that lateral augmentation of the classic TOE repair produces a biomechanically superior construct that may optimize tendon healing.
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Lesões do Manguito Rotador/cirurgia , Manguito Rotador/cirurgia , Tendões/cirurgia , Idoso , Idoso de 80 Anos ou mais , Fenômenos Biomecânicos , Cadáver , Humanos , Masculino , Pessoa de Meia-Idade , Rotação , Técnicas de Sutura , SuturasRESUMO
BACKGROUND: Several approaches to spring ligament reconstruction have been reported. However, a comparative study of nonanatomic and anatomic techniques with respect to biomechanical responses, such as kinematics and contact characteristics, has not been previously performed via a finite element analysis. The purpose of this study was to evaluate the biomechanical results of such spring ligament reconstructions via a finite element analysis. METHODS: A three-dimensional finite element model of the foot was developed and validated, and four reconstruction methods were simulated. The talonavicular dorsiflexion and abduction, hindfoot valgus, and contact characteristics in the Chopart joints were quantified in each model. RESULTS: Nonanatomic reconstructions corrected the talonavicular and hindfoot deformities to a greater extent than the anatomic reconstructions. The anatomic techniques also corrected the abduction and dorsiflexion deformities, although they presented insufficient power to correct for hindfoot valgus. None of the procedures restored the contact characteristics of the talonavicular and calcaneocuboid joints to those of a normal condition. CONCLUSION: Nonanatomic reconstruction of the spring ligament complex provided the greatest correction for midfoot and hindfoot misalignments in flatfoot. Severe deformities with large amounts of midfoot pronation and hindfoot valgus may be better treated with nonanatomic reconstruction methods. The spring ligament reconstruction method may mitigate the need for nonanatomic bony procedures associated with complications and allows for the preservation of the triple joint complex.
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Análise de Elementos Finitos , Pé/anatomia & histologia , Pé/fisiologia , Imageamento Tridimensional , Ligamentos Articulares/anatomia & histologia , Ligamentos Articulares/fisiologia , Adulto , Fenômenos Biomecânicos/fisiologia , Pé/diagnóstico por imagem , Humanos , Imageamento Tridimensional/métodos , Ligamentos Articulares/diagnóstico por imagem , MasculinoRESUMO
Objective: To establish the model of compression fracture of acetabular dome, and to measure the contact characteristics of acetabular weight-bearing area of acetabulum after 3 kinds of internal fixation. Methods: Sixteen fresh adult half pelvis specimens were randomly divided into 4 groups, 4 specimens each group. Group D was the complete acetabulum (control group), and the remaining 3 groups were prepared acetabular dome compression fracture model. The fractures were fixed with reconstruction plate in group A, antegrade raft screws in group B, and retrograde raft screws in group C. The pressure sensitive films were attached to the femoral head, and the axial compression test was carried out on the inverted single leg standing position. The weight-bearing area, average stress, and peak stress were measured in each group. Results: Under the loading of 500 N, the acetabular weight-bearing area was significantly higher in group D than in other 3 groups ( P<0.05), and the average stress and peak stress were significantly lower than in other 3 groups ( P<0.05). The acetabular weight-bearing area were significantly higher in group B and group C than in group A, and the average stress and peak stress were significantly lower than in group A ( P<0.05). There was no significant difference in the above indexes between group B and group C ( P>0.05). Conclusion: For the compression fracture of the acetabular dome, the contact characteristics of the weight-bearing area can not restore to the normal level, even if the anatomical reduction and rigid internal fixation were performed; compared with the reconstruction plate fixation, antegrade and retrograde raft screws fixations can increase the weight-bearing area, reduce the average stress and peak stress, and reduce the incidence of traumatic arthritis.
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Parafusos Ósseos , Fixação Interna de Fraturas , Fraturas por Compressão , Suporte de Carga , Acetábulo , Cadáver , Fraturas Ósseas , HumanosRESUMO
BACKGROUND: Isolated medial malleolus fractures are typically treated operatively to minimize the potential for articular incongruity, instability, nonunion, and posttraumatic arthritis. The literature, however, has not clearly demonstrated inferior outcomes with conservative treatment of these injuries. This study measured the effects of medial malleolus fracture and its resultant instability on tibiotalar joint contact characteristics. We hypothesized that restoration of anatomical alignment and stability through fixation would significantly improve contact characteristics. METHODS: A Tekscan pressure sensor was inserted and centered over the talar dome in 8 cadaveric foot and ankle specimens. Each specimen was loaded at 700 N in multiple coronal and sagittal plane orientations. After testing fractured samples, the medial malleolus was anatomically fixed before repeat testing. Contact area and pressure were analyzed using a 2-way repeated-measure ANOVA. RESULTS: In treated fractures, contact areas were higher, and mean contact pressures were lower for all positions. These differences were statistically significant in the majority of orientations and approached statistical significance in pure plantarflexion and pure inversion. Decreases in contact area varied from 15.1% to 42.1%, with the most dramatic reductions in positions of hindfoot eversion. CONCLUSIONS: These data emphasize the importance of the medial malleolus in maintaining normal tibiotalar contact area and pressure. The average decrease in contact area after simulated medial malleolar fractures was 27.8% (>40% in positions of hindfoot eversion). Such differences become clinically relevant in cases of medial malleolar nonunion or malunion. Therefore, we recommend anatomical reduction and fixation of medial malleolus fractures with any displacement. LEVEL OF EVIDENCE: Therapeutic Level V-Cadaveric Study.
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Traumatismos do Tornozelo/fisiopatologia , Articulação do Tornozelo/fisiopatologia , Fraturas Ósseas/fisiopatologia , Articulações Tarsianas/fisiopatologia , Traumatismos do Tornozelo/cirurgia , Articulação do Tornozelo/cirurgia , Cadáver , Fixação de Fratura , Fraturas Ósseas/cirurgia , Humanos , Instabilidade Articular/fisiopatologia , Instabilidade Articular/cirurgia , PressãoRESUMO
BACKGROUND: Transosseous-equivalent (TOE) rotator cuff repair can increase contact area and contact pressure between the repaired cuff tendon and bony footprint and can show higher ultimate loads to failure and smaller gap formation compared with other repair techniques. However, it has been suggested that medial rotator cuff failure after TOE repair may result from increased bridging suture tension. PURPOSE: To determine optimum bridging suture tension in TOE repair by evaluating footprint contact and construct failure characteristics at different tensions. STUDY DESIGN: Controlled laboratory study. METHODS: A total of 18 fresh-frozen cadaveric shoulders, randomly divided into 3 groups, were constructed with a TOE configuration using the same medial suture anchor and placing a Tekscan sensing pad between the repaired rotator cuff tendon and footprint. Nine of the 18 shoulders were used to measure footprint contact characteristics. With use of the Tekscan measurement system, the contact pressure and area between the rotator cuff tendon and greater tuberosity were quantified for bridging suture tensions of 60, 90, and 120 N with glenohumeral abduction angles of 0° and 30° and humeral rotation angles of 30° (internal), 0°, and 30° (external). TOE constructs of all 18 shoulders then underwent construct failure testing (cyclic loading and load to failure) to determine the yield load, ultimate load, stiffness, hysteresis, strain, and failure mode at 60 and 120 N of tension. RESULTS: As bridging suture tension increased, contact force, contact pressure, and peak pressure increased significantly at all positions (P < .05 for all). Regarding contact area, no significant differences were found between 90 and 120 N at all positions, although there were significant differences between 60 and 90 N. The construct failure test demonstrated no significant differences in any parameters according to various tensions (P > .05 for all). CONCLUSION: Increasing bridging suture tension to over 90 N did not improve contact area but did increase contact force and pressure. Bridging suture tension did not significantly affect ultimate failure loads. CLINICAL RELEVANCE: Considering the risks of overtensioning bridging sutures, it may be clinically more beneficial to keep bridging suture tension below 90 N.