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OBJECTIVES: To quantify dental forces during double-lumen tube intubations with different laryngoscopy techniques. DESIGN: Experimental biomechanical mannequin study. SETTING: Two German university hospitals. PARTICIPANTS: One hundred four anesthesiologists with varying levels of experience. INTERVENTIONS: Participants performed a sequence of intubations on a mannequin equipped with hidden forces sensors in the maxillary incisors. Different laryngoscopy techniques were evaluated under normal and difficult airway conditions. Direct laryngoscopy was compared with different videolaryngoscopy techniques: the C-MAC with a Macintosh blade, the GlideScope, and the KingVision with hyperangulated blades. MEASUREMENTS AND MAIN RESULTS: A total of 624 intubations were evaluated. In normal airway conditions, the median (interquartile range [range]) peak forces were significantly lower when the GlideScope (15.7 (11.3-22.0 [2.1-110.5]) N) was used compared with direct laryngoscopy (21.0 (14.1-28.5[4.7-168.6]) N) (p = 0.007). In difficult airways, resulting forces were reduced using hyperangulated videolaryngoscopes (GlideScope: -13.7 N [p < 0.001]; KingVision: -11.9 N [p < 0.001]) compared with direct laryngoscopy, respectively. The time to intubation was prolonged with the use of the KingVision (25.5 (17.1-41.9[9.2-275.0])s [p < 0.001]) in comparison to direct laryngoscopy (20.8 (15.9-27.4[8.7-198.6]) s). The C-MAC demonstrated the shortest time to intubation. CONCLUSIONS: Although hyperangulated videolaryngoscopes improve dental strain, clinicians also should consider the time to intubation, which is shortest with nonhyperangulated videoblades, when choosing a laryngoscopy technique on an individual patient basis.
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Laringoscópios , Laringoscopia , Humanos , Incisivo , Intubação Intratraqueal/métodos , Laringoscopia/métodos , Manequins , Gravação em VídeoRESUMO
PURPOSE: Mechanical impingement at the narrow radioulnar space of the tuberosity is believed to be an etiological factor in the injury of the distal biceps tendon. The aim of the study was to compare the pressure distribution at the proximal radioulnar space between 2 fixation techniques and the intact state. METHODS: Six right arms and 6 left arms from 5 female and 6 male frozen specimens were used for this study. A pressure transducer was introduced at the height of the radial tuberosity with the intact distal biceps tendon and after 2 fixation methods: the suture-anchor and the cortical button technique. The force (N), maximum pressure (kPa) applied to the radial tuberosity, and the contact area (mm2) of the radial tuberosity with the ulna were measured and differences from the intact tendon were detected from 60° supination to 60° pronation in 15° increments with the elbow in full extension and in 45° and 90° flexion of the elbow. RESULTS: With the distal biceps tendon intact, the pressures during pronation were similar regardless of extension and flexion and were the highest at 60° pronation with 90° elbow flexion (23.3 ± 53.5 kPa). After repair of the tendon, the mean peak pressure, contact area, and total force showed an increase regardless of the fixation technique. Highest peak pressures were found using the cortical button technique at 45° flexion of the elbow and 60° pronation. These differences were significantly different from the intact tendon. The contact area was significantly larger in full extension and 15°, 30°, and 60° pronation using the cortical button technique. CONCLUSIONS: Pressures on the distal biceps tendon at the radial tuberosity increase during pronation, especially after repair of the tendon. CLINICAL RELEVANCE: Mechanical impingement could play a role in both the etiology of primary distal biceps tendon ruptures and the complications occurring after fixation of the tendon using certain techniques.
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Cotovelo , Rádio (Anatomia) , Cadáver , Feminino , Humanos , Masculino , Rádio (Anatomia)/cirurgia , Ruptura , Supinação , Tendões/cirurgiaRESUMO
PURPOSE: The aim of this study was to compare several osteosynthesis techniques (intramedullary headless compression screws, T-plates, and Kirschner wires) for distal epiphyseal fractures of proximal phalanges in a human cadaveric model. METHODS: A total of 90 proximal phalanges from 30 specimens (index, ring, and middle fingers) were used for this study. After stripping off all soft tissue, a transverse distal epiphyseal fracture was simulated at the proximal phalanx. The 30 specimens were randomly assigned to 1 fixation technique (30 per technique), either a 3.0-mm intramedullary headless compression screw, locking plate fixation with a 2.0-mm T-plate, or 2 oblique 1.0-mm Kirschner wires. Displacement analysis (bending, distraction, and torsion) was performed using optical tracking of an applied random speckle pattern after osteosynthesis. Biomechanical testing was performed with increasing cyclic loading and with cyclic load to failure using a biaxial torsion-tension testing machine. RESULTS: Cannulated intramedullary compression screws showed significantly less displacement at the fracture site in torsional testing. Furthermore, screws were significantly more stable in bending testing. Kirschner wires were significantly less stable than plating or screw fixation in any cyclic load to failure test setup. CONCLUSIONS: Intramedullary compression screws are a highly stable alternative in the treatment of transverse distal epiphyseal phalangeal fractures. Kirschner wires seem to be inferior regarding displacement properties and primary stability. CLINICAL RELEVANCE: Fracture fixation of phalangeal fractures using plate osteosynthesis may have the advantage of a very rigid reduction, but disadvantages such as stiffness owing to the more invasive surgical approach and soft tissue irritation should be taken into account. Headless compression screws represent a minimally invasive choice for fixation with good biomechanical properties.
Assuntos
Fios Ortopédicos , Fraturas Ósseas , Fenômenos Biomecânicos , Placas Ósseas , Parafusos Ósseos , Cadáver , Fixação Interna de Fraturas , Fraturas Ósseas/cirurgia , HumanosRESUMO
OBJECTIVE: To investigate the postural and metabolic benefits a walker with adjustable elbow support (LifeWalker [LW]) can provide for ambulation in population with impairment. The clinical outcomes from the elbow support walker will be compared with standard rollator (SR) and participants predicate device (PD). DESIGN: Case-crossover study design. SETTING: Clinical laboratory. PARTICIPANTS: Individuals aged between 18 and 85 years using a rollator walker as primary mode of assistance and certified as medically stable by their primary physician. Participants (N=30; 80% women [n=24]) recruited from a convenient sample provided voluntary consent and completed the study. INTERVENTION: Not applicable. MAIN OUTCOME MEASURES: The trunk anterior-posterior (AP) sway (during the 10-meter walk test), oxygen consumption (during the 6-minute walk test), the mean forearm load offloaded to the elbow support as percentage of body weight, and mean peak hand grip load (during the 25-meter walk test) were measured. RESULTS: Ambulating with a LW led to (1) reduced trunk sway in the AP direction [(ZLW vs PD= -2.34, P=.018); (ZLW vs SR= -3.461, P=.001)]; (2) reduced erector spinae muscle activation at the left lumbar L3 level [(ZLW vs PD= -2.71, P=.007); (ZLW vs SR= -1.71, P=.09)]; and (3) improved gait efficiency [(ZLW vs PD= -2.66, P=.008) Oxygen cost; (ZLW Vs. SR= -2.66, P=.008) Oxygen cost]. Participants offloaded between 39% and 46% of their body weight through the elbow support armrest while ambulating with the LW. Irrespective of the walker used, participants exerted â¼5%-6% of their body weight in gripping the walker handles during walking. CONCLUSIONS: Using the forearm support-based LW led to upright body posture, offloaded portions of body weight from the lower extremity, and improved gait efficiency during ambulation in comparison to the SR and the participants' own PD. Further studies focusing on population-specific benefits are recommended.
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Desenho de Equipamento/métodos , Antebraço/fisiopatologia , Transtornos Motores/reabilitação , Postura , Andadores , Idoso , Peso Corporal , Estudos Cross-Over , Cotovelo/fisiopatologia , Feminino , Marcha , Força da Mão , Humanos , Extremidade Inferior , Masculino , Pessoa de Meia-Idade , Limitação da Mobilidade , Transtornos Motores/fisiopatologia , Consumo de Oxigênio , Tronco/fisiopatologia , Caminhada , Suporte de CargaRESUMO
PURPOSE: Shortening osteotomy of the proximal radius might represent a potential salvage procedure in symptomatic radiocapitellar osteoarthritis, which could decrease radiocapitellar load while preserving the native radial head. In an in-vitro biomechanical investigation, we sought to determine whether shortening osteotomy of the proximal radius (1) decreases the radiocapitellar joint pressure upon axial loading and (2) retains valgus stability of the elbow. In addition, the anatomic configuration of the lesser sigmoid notch was evaluated to assess possible contraindications. METHODS: Axial loading (0-400 N) and valgus torque (7.5 N m) over the full range of motion were applied to 14 fresh-frozen specimens before and after shortening osteotomy of the proximal radius by 2.5 mm. Radiocapitellar and ulnohumeral load distribution during axial compression was evaluated using a digital pressure mapping sensor. Valgus displacement was analyzed with a 3D camera system. The inclination angle (α) of the lesser sigmoid notch was assessed via 50 CT scans. RESULTS: Up to axial loading of 250 N, shortening osteotomy caused a significant decrease in radiocapitellar contact pressures (p < 0.041). Valgus stability of specimens did not differ before and after shortening osteotomy (n.s.). The mean inclination angle (α) of the lesser sigmoid notch was 11.3° ± 6.3°. 46% had an inclination angle of ≤ 10° (type I). 46% had an inclination angle of 11°-20° (type II). In 8%, the inclination angle was >20° (type III). CONCLUSION: Shortening osteotomy of the proximal radius can decrease radiocapitellar contact pressures during axial loading of up to 250 N. Primary valgus stability is not relevantly influenced by this procedure. In few patients, shortening osteotomy may cause radioulnar impingement of the radial head at the distal edge of the lesser sigmoid notch due to an inclination angle of >20°. Shortening osteotomy might be a promising treatment option to decrease pain levels in case of isolated radiocapitellar osteoarthritis.
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Articulação do Cotovelo/cirurgia , Osteoartrite/cirurgia , Osteotomia/métodos , Rádio (Anatomia)/cirurgia , Idoso , Idoso de 80 Anos ou mais , Fenômenos Biomecânicos , Cadáver , Cotovelo , Articulação do Cotovelo/fisiopatologia , Epífises/cirurgia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Osteoartrite/fisiopatologia , Pressão , Amplitude de Movimento Articular , TorqueRESUMO
PURPOSE: Double plating has been promoted, in recent years, as an alternative treatment method for proximal ulna fractures. This study aimed to compare the biomechanical properties of double-plate osteosynthesis with posterior plate fixation using a novel investigational design utilizing a 3-dimensional camera system to analyze fracture micromotion. METHODS: Fourteen fresh-frozen specimens were available for this study. Mayo type IIA fractures of the olecranon were created and internal fixation was performed with either an angular stable posterior plate or angular stable double plates. Fracture micromotion was evaluated by means of digital image correlation with a 3-dimensional camera system before and after dynamic cyclic loading from 15° to 90° of elbow flexion with a pulling force of 25 N to 80 N. RESULTS: Micromotion of fragments was less pronounced in double-plate osteosynthesis when compared with single plates before and after cyclic loading. However, overall results were similar. Two of the single plates failed during cyclic loading but there were no failures in the double plates. CONCLUSIONS: This biomechanical analysis shows that single and double plating results in comparable stability of fixation. Although the double-plating technique tends to provide more stable fixation, relevant differences were not observed. CLINICAL RELEVANCE: Double plating potentially represents an efficient option for fixation of proximal ulna fractures. It could decrease the risk of soft tissue complications owing to their low profile and the superior soft tissue coverage.
Assuntos
Placas Ósseas , Articulação do Cotovelo/fisiopatologia , Fixação Interna de Fraturas , Fraturas da Ulna/fisiopatologia , Fraturas da Ulna/cirurgia , Idoso , Idoso de 80 Anos ou mais , Cadáver , Feminino , Consolidação da Fratura , Humanos , Aumento da Imagem , Masculino , Amplitude de Movimento Articular , Fraturas da Ulna/diagnóstico por imagem , Suporte de CargaRESUMO
BACKGROUND/AIMS: Common systems for the quantification of cellular contraction rely on animal-based models, complex experimental setups or indirect approaches. The herein presented CellDrum technology for testing mechanical tension of cellular monolayers and thin tissue constructs has the potential to scale-up mechanical testing towards medium-throughput analyses. Using hiPS-Cardiac Myocytes (hiPS-CMs) it represents a new perspective of drug testing and brings us closer to personalized drug medication. METHODS: In the present study, monolayers of self-beating hiPS-CMs were grown on ultra-thin circular silicone membranes and deflect under the weight of the culture medium. Rhythmic contractions of the hiPS-CMs induced variations of the membrane deflection. The recorded contraction-relaxation-cycles were analyzed with respect to their amplitudes, durations, time integrals and frequencies. Besides unstimulated force and tensile stress, we investigated the effects of agonists and antagonists acting on Ca2+ channels (S-Bay K8644/verapamil) and Na+ channels (veratridine/lidocaine). RESULTS: The measured data and simulations for pharmacologically unstimulated contraction resembled findings in native human heart tissue, while the pharmacological dose-response curves were highly accurate and consistent with reference data. CONCLUSION: We conclude that the combination of the CellDrum with hiPS-CMs offers a fast, facile and precise system for pharmacological, toxicological studies and offers new preclinical basic research potential.
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Células-Tronco Pluripotentes Induzidas/citologia , Canais Iônicos/agonistas , Canais Iônicos/antagonistas & inibidores , Miócitos Cardíacos/citologia , Estresse Mecânico , Técnicas de Cultura de Células/métodos , Diferenciação Celular , Humanos , Células-Tronco Pluripotentes Induzidas/efeitos dos fármacos , Lidocaína/farmacologia , Contração Miocárdica/efeitos dos fármacos , Miócitos Cardíacos/efeitos dos fármacos , Miócitos Cardíacos/fisiologia , Verapamil/farmacologia , Veratridina/farmacologiaRESUMO
We compare experimental and computational results for the actions of the cardioactive drugs Lidocaine, Verapamil, Veratridine, and Bay K 8644 on a tissue monolayer consisting of mainly fibroblasts and human-induced pluripotent stem cell-derived cardiomyocytes (hiPSc-CM). The choice of the computational models is justified and literature data is collected to model drug action as accurately as possible. The focus of this work is to evaluate the validity and capability of existing models for native human cells with respect to the simulation of pharmaceutical treatment of monolayers and hiPSc-CM. From the comparison of experimental and computational results, we derive suggestions for model improvements which are intended to computationally support the interpretation of experimental results obtained for hiPSc-CM.
Assuntos
Fármacos Cardiovasculares/farmacologia , Células-Tronco Pluripotentes Induzidas/citologia , Modelos Biológicos , Miócitos Cardíacos/citologia , Miócitos Cardíacos/efeitos dos fármacos , Cardiotônicos/farmacologia , Frequência Cardíaca/efeitos dos fármacos , HumanosRESUMO
The mechanical behavior of the large intestine beyond the ultimate stress has never been investigated. Stretching beyond the ultimate stress may drastically impair the tissue microstructure, which consequently weakens its healthy state functions of absorption, temporary storage, and transportation for defecation. Due to closely similar microstructure and function with humans, biaxial tensile experiments on the porcine large intestine have been performed in this study. In this paper, we report hyperelastic characterization of the large intestine based on experiments in 102 specimens. We also report the theoretical analysis of the experimental results, including an exponential damage evolution function. The fracture energies and the threshold stresses are set as damage material parameters for the longitudinal muscular, the circumferential muscular and the submucosal collagenous layers. A biaxial tensile simulation of a linear brick element has been performed to validate the applicability of the estimated material parameters. The model successfully simulates the biomechanical response of the large intestine under physiological and non-physiological loads.
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BACKGROUND: Double-row (DR) and transosseous-equivalent (TOE) techniques for rotator cuff repair offer more stability and promote better tendon healing compared with single-row (SR) repairs and are preferred by many surgeons. However, they can lead to more disastrous retear patterns with failure at the medial anchor row or the musculotendinous junction. The biomechanics of medial cuff failure have not been thoroughly investigated thus far. PURPOSE: To investigate the intratendinous strain distribution within the supraspinatus tendon depending on repair technique. STUDY DESIGN: Controlled laboratory study. METHODS: Twelve fresh-frozen cadaveric shoulders were used. The intratendinous strain within the supraspinatus tendon was analyzed in 2 regions-(1) at the footprint at the greater tuberosity and (2) medial to the footprint up to the musculotendinous junction-using a high-resolution 3-dimensional camera system. Testing was performed at submaximal loads of 40 N, 60 N, and 80 N for intact tendons, after SR repair, after DR repair, and after TOE repair. RESULTS: The tendon strain of the SR group differed significantly in both regions from that of the intact tendons and the TOE group at 40 N (P≤ .043) and from the intact tendons, the DR group, and the TOE group at 60 N and 80 N (P≤ .048). SR repairs showed more tendon elongation at the footprint and less elongation medial to the footprint. DR and TOE repairs did not provide significant differences in tendon strain when compared with the intact tendons. However, the increase in tendon strain medial to the footprint from 40 N to 80 N was significantly more pronounced in the DR and TOE group (P≤ .029). CONCLUSION: While DR and TOE repair techniques more closely reproduced the strains of the supraspinatus tendon than did SR repair in a cadaveric model, they showed a significantly increased tendon strain at the musculotendinous junction with higher loads in comparison with the intact tendon. CLINICAL RELEVANCE: DR and TOE rotator cuff reconstructions lead to a more anatomic tendon repair. However, their use has to be carefully evaluated whenever tendon quality is diminished, as they lead to a more drastic increase in tendon strain medial to the footprint, putting these repairs at risk of medial cuff failure.
Assuntos
Lesões do Manguito Rotador , Manguito Rotador , Fenômenos Biomecânicos , Cadáver , Humanos , Manguito Rotador/cirurgia , Lesões do Manguito Rotador/cirurgia , Técnicas de Sutura , Tendões/cirurgiaRESUMO
BACKGROUND: Additional stabilization of the "comma sign" in anterosuperior rotator cuff repair has been proposed to provide biomechanical benefits regarding stability of the repair. PURPOSE: This in vitro investigation aimed to investigate the influence of a comma sign-directed reconstruction technique for anterosuperior rotator cuff tears on the primary stability of the subscapularis tendon repair. STUDY DESIGN: Controlled laboratory study. METHODS: A total of 18 fresh-frozen cadaveric shoulders were used in this study. Anterosuperior rotator cuff tears (complete full-thickness tear of the supraspinatus and subscapularis tendons) were created, and supraspinatus repair was performed with a standard suture bridge technique. The subscapularis was repaired with either a (1) single-row or (2) comma sign technique. A high-resolution 3D camera system was used to analyze 3-mm and 5-mm gap formation at the subscapularis tendon-bone interface upon incremental cyclic loading. Moreover, the ultimate failure load of the repair was recorded. A Mann-Whitney test was used to assess significant differences between the 2 groups. RESULTS: The comma sign repair withstood significantly more loading cycles than the single-row repair until 3-mm and 5-mm gap formation occurred (P≤ .047). The ultimate failure load did not reveal any significant differences when the 2 techniques were compared (P = .596). CONCLUSION: The results of this study show that additional stabilization of the comma sign enhanced the primary stability of subscapularis tendon repair in anterosuperior rotator cuff tears. Although this stabilization did not seem to influence the ultimate failure load, it effectively decreased the micromotion at the tendon-bone interface during cyclic loading. CLINICAL RELEVANCE: The proposed technique for stabilization of the comma sign has shown superior biomechanical properties in comparison with a single-row repair and might thus improve tendon healing. Further clinical research will be necessary to determine its influence on the functional outcome.
Assuntos
Lesões do Manguito Rotador , Manguito Rotador , Fenômenos Biomecânicos , Cadáver , Humanos , Manguito Rotador/cirurgia , Lesões do Manguito Rotador/cirurgia , Ombro/cirurgia , Técnicas de SuturaRESUMO
Three-dimensional (3D) full-field measurements provide a comprehensive and accurate validation of finite element (FE) models. For the validation, the result of the model and measurements are compared based on two respective point-sets and this requires the point-sets to be registered in one coordinate system. Point-set registration is a non-convex optimization problem that has widely been solved by the ordinary iterative closest point algorithm. However, this approach necessitates a good initialization without which it easily returns a local optimum, i.e. an erroneous registration. The globally optimal iterative closest point (Go-ICP) algorithm has overcome this drawback and forms the basis for the presented open-source tool that can be used for the validation of FE models using 3D full-field measurements. The capability of the tool is demonstrated using an application example from the field of biomechanics. Methodological problems that arise in real-world data and the respective implemented solution approaches are discussed.
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Análise de Elementos Finitos , Software , Algoritmos , Reprodutibilidade dos TestesRESUMO
BACKGROUND: Osteoporosis is associated with the risk of fractures near the hip. Age and comorbidities increase the perioperative risk. Due to the ageing population, fracture of the proximal femur also proves to be a socio-economic problem. Preventive surgical measures have hardly been used so far. METHODS: 10 pairs of human femora from fresh cadavers were divided into control and low-volume femoroplasty groups and subjected to a Hayes fall-loading fracture test. The results of the respective localization and classification of the fracture site, the Singh index determined by computed tomography (CT) examination and the parameters in terms of fracture force, work to fracture and stiffness were evaluated statistically and with the finite element method. In addition, a finite element parametric study with different position angles and variants of the tubular geometry of the femoroplasty was performed. FINDINGS: Compared to the control group, the work to fracture could be increased by 33.2%. The fracture force increased by 19.9%. The used technique and instrumentation proved to be standardized and reproducible with an average poly(methyl methacrylate) volume of 10.5 ml. The parametric study showed the best results for the selected angle and geometry. INTERPRETATION: The cadaver studies demonstrated the biomechanical efficacy of the low-volume tubular femoroplasty. The numerical calculations confirmed the optimal choice of positioning as well as the inner and outer diameter of the tube in this setting. The standardized minimally invasive technique with the instruments developed for it could be used in further comparative studies to confirm the measured biomechanical results.
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Fêmur/cirurgia , Fenômenos Mecânicos , Idoso , Idoso de 80 Anos ou mais , Fenômenos Biomecânicos , Cadáver , Feminino , Fêmur/diagnóstico por imagem , Análise de Elementos Finitos , Fraturas Ósseas/cirurgia , Humanos , Masculino , Polimetil Metacrilato , Padrões de Referência , Tomografia Computadorizada por Raios XRESUMO
Ski jumping performance is strongly affected by wind. Flight technique optimization for maximizing jump length is a highly complex motor-control task that also depends on the wind. Pontryagin's minimum principle was used in this study to gain a better understanding on how wind influences flight technique optimization. Optimum time courses of the angle of attack α of the skis and of the body-to-ski angle ß were computed for seven realistic wind scenarios on the large hill and on the flying hill. The optimum values of α were smaller at headwind, and larger at tailwind when compared to the optimum time course at calm wind. The optimum values of ß were the smallest possible ones at the given flight technique constraints, except for the last part of the flight. Optimum adjustments of α increased the jump lengths between 0 and 1.8â¯m on the large hill, and between 0 and 6.4â¯m on the flying hill. Maximum jump length increases were achieved at the highest headwind speed. Even larger jump length effects can be achieved by using smaller ß-angles, which might be possible in headwind conditions, but this is associated with increased problems to keep the flight stable.
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Esqui/fisiologia , Vento , Simulação por Computador , HumanosRESUMO
A non-anatomical reinsertion of the supraspinatus medially to the original footprint to avoid over-tensioning of the tendon in large and retracted tears is one surgical option in rotator cuff (RC) repair. The purpose of the study was to determine the biomechanical effects on the glenohumeral joint with regard to this surgical technique. A modified musculoskeletal computational shoulder model was used to evaluate the change in moment arms and muscle forces of the RC and the co-contracting muscles and the alteration of the joint reaction forces (compressive and shear forces) after reinsertion of the supraspinatus 5 mm, 10 mm, 15 mm and 20 mm medially to the original footprint. A medialization of the supraspinatus reduces its moment arm in glenohumeral abduction. In case of a medialization of the attachment of 15 mm and 20 mm, the supraspinatus restricts glenohumeral abduction at 54° and 68°. In glenohumeral forward flexion and in lower degrees of internal rotation the moment arm of the supraspinatus increases for a medialized tendon attachment and decreases in external rotation in relation to the anatomical condition. A medialization of the supraspinatus insertion point yields in an increase in muscle force for abduction, internal and external rotation. In the present model a medially non-anatomic reinsertion reduces significantly the compressive glenohumeral joint reaction and the glenohumeral stability. Moreover, the results show that a medialization of the supraspinatus leads to a reduction of the supraspinatus moment arm especially in abduction. This leads to an increase of a compensatory supraspinatus load for stabilization the humerus in space, which may potentially cause a postoperative overload of the tendon-bone-complex.
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Simulação por Computador , Articulações/fisiologia , Fenômenos Fisiológicos Musculoesqueléticos , Manguito Rotador/patologia , Ombro/fisiologia , Cicatrização , Fenômenos Biomecânicos , Humanos , Movimento/fisiologia , Contração Muscular , Amplitude de Movimento Articular/fisiologia , Rotação , Articulação do Ombro/fisiologiaRESUMO
If conservative treatment of osteoporotic vertebral compression fractures fails, vertebro- or kyphoplasty is indicated. Usually, polymethylmethacrylate cement (PMMA) is applied coming along with many disadvantageous features. Aluminum-free glass-polyalkenoate cement (GPC) appears to be a benefit alternative material. This study aimed at comparing the mean stress values in human vertebrae after kyphoplasty with PMMA and GPC (IlluminOss™) at hand of a finite element analysis. Three models were created performing kyphoplasty using PMMA or IlluminOss™, respectively, at two native, human lumbar vertebrae (L4) while one remains intact. Finite element analysis was performed using CT-scans of every vertebra. Moreover the PMMA-treated vertebra was used as a model as analyses were executed using material data of PMMA and of GPC. The unimpaired, spongious bone showed potentials of 0.25 MPa maximally. After augmentation stress levels showed fivefold increase, rising from externally to internally, revealing stress peaks at the ventral border of the spinal canal. At central areas of cement 1 MPa is measured in both types of cement. Around these central areas the von Mises stress decreased about 25-50% (0.5-0.75 MPa). If workload of 500 N was applied, the stress appeared to be more centralized at the IlluminOss™-model, similar to the unimpaired. Considering the endplates the GPC model also closely resembles the unimpaired. Comparing the PMMA-treated vertebral body and the GPC-simulation, there is an obvious difference. While the PMMA-treated model showed a central stress peak of 5 MPa, the GPC-simulation of the same vertebral body presents lower stress of 1.2-2.5 MPa. Finite element analysis showed that IlluminOss™ (GPC), used in kyphoplasty of vertebral bodies, creates lower level stress and strain compared to standardly used PMMA, leading to lower stress concentrations on the cranial and caudal vertebral surface especially. GPC appears to own advantageous biological and clinical relevant features.
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Cimentos Ósseos/uso terapêutico , Análise de Elementos Finitos , Cifoplastia , Fraturas por Osteoporose/cirurgia , Fraturas da Coluna Vertebral/cirurgia , Idoso , Idoso de 80 Anos ou mais , Osso Esponjoso/patologia , Osso Cortical/cirurgia , Feminino , Cimentos de Ionômeros de Vidro/química , Humanos , Masculino , Polimetil Metacrilato/química , Estresse MecânicoRESUMO
BACKGROUND: Irreparable rotator cuff tears lead to superior translation of the humeral head. Numerous surgical management options are available to treat the condition. PURPOSE: To compare superior capsule stability among different types of patch grafting in irreparable rotator cuff tears. METHODS: Six cadaveric shoulders were tested in a custom-designed shoulder testing system. Superior translation of the humerus and subacromial contact pressure were quantified in an intact condition (condition 1), after cutting the supraspinatus tendon (condition 2), and after additionally cutting the superior capsuloligamentous complex (condition 3). The results were compared among 3 types of patch grafting, in which capsule reconstruction was achieved by glenoidal 3-point (condition 4) or 2-point (condition 5) fixation or by affixing a graft below the acromion (condition 6). RESULTS: No significant difference in subacromial pressure was measured by reconstruction with 2 or 3 anchors compared with conditions 1 and 2 (P > .05). However, with 3-point fixation, lower levels of pressure were measured than with 2-point fixation. Moreover, superior translation values were lower with 3-point fixation; the same applied for values of the preserved capsule as compared with the torn capsule. In condition 6, a significant increase in pressure in the neutral position was documented (P < .05). CONCLUSION: The superior capsuloligamentous complex plays an important role in stabilizing the glenohumeral joint. The results suggest that with additional medial anchoring at the coracoid base, the depressing and centering effect of the superior complex can probably be regained in a more physiological way compared with a reconstructed capsule with 2 glenoid attachments or with an interpositional graft below the acromion.
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After menopause, decreased levels of estrogen and progesterone remodel the collagen of the soft tissues thereby reducing their stiffness. Stress urinary incontinence is associated with involuntary urine leakage due to pathological movement of the pelvic organs resulting from lax suspension system, fasciae, and ligaments. This study compares the changes in the orientation and position of the female pelvic organs due to weakened fasciae, ligaments, and their combined laxity. A mixture theory weighted by respective volume fraction of elastin-collagen fibre compound (5%), adipose tissue (85%), and smooth muscle (5%) is adopted to characterize the mechanical behaviour of the fascia. The load carrying response (other than the functional response to the pelvic organs) of each fascia component, pelvic organs, muscles, and ligaments are assumed to be isotropic, hyperelastic, and incompressible. Finite element simulations are conducted during Valsalva manoeuvre with weakened tissues modelled by reduced tissue stiffness. A significant dislocation of the urethrovesical junction is observed due to weakness of the fascia (13.89 mm) compared to the ligaments (5.47 mm). The dynamics of the pelvic floor observed in this study during Valsalva manoeuvre is associated with urethral-bladder hypermobility, greater levator plate angulation, and positive Q-tip test which are observed in incontinent females.
Assuntos
Tecido Conjuntivo/diagnóstico por imagem , Diafragma da Pelve/diagnóstico por imagem , Diafragma da Pelve/fisiopatologia , Pós-Menopausa , Bexiga Urinária/diagnóstico por imagem , Bexiga Urinária/fisiopatologia , Tecido Adiposo/patologia , Idoso , Algoritmos , Cadáver , Colágeno/química , Simulação por Computador , Elasticidade , Elastina/química , Feminino , Análise de Elementos Finitos , Humanos , Ligamentos , Modelos Estatísticos , Movimento , Músculo Liso/patologia , Incontinência Urinária/fisiopatologia , Manobra de ValsalvaRESUMO
Wind is closely associated with the discussion of fairness in ski jumping. To counter-act its influence on the jump length, the International Ski Federation (FIS) has introduced a wind compensation approach. We applied three differently accurate computer models of the flight phase with wind (M1, M2, and M3) to study the jump length effects of various wind scenarios. The previously used model M1 is accurate for wind blowing in direction of the flight path, but inaccuracies are to be expected for wind directions deviating from the tangent to the flight path. M2 considers the change of airflow direction, but it does not consider the associated change in the angle of attack of the skis which additionally modifies drag and lift area time functions. M3 predicts the length effect for all wind directions within the plane of the flight trajectory without any mathematical simplification. Prediction errors of M3 are determined only by the quality of the input data: wind velocity, drag and lift area functions, take-off velocity, and weight. For comparing the three models, drag and lift area functions of an optimized reference jump were used. Results obtained with M2, which is much easier to handle than M3, did not deviate noticeably when compared to predictions of the reference model M3. Therefore, we suggest to use M2 in future applications. A comparison of M2 predictions with the FIS wind compensation system showed substantial discrepancies, for instance: in the first flight phase, tailwind can increase jump length, and headwind can decrease it; this is opposite of what had been anticipated before and is not considered in the current wind compensation system in ski jumping.