RESUMEN
Competency-based grading (CBG) can take different forms in different subject areas. We present a method for implementing CBG in a biomechanics course with nine primary learning objectives. Competency in each learning objective is measured by the student's ability to correctly answer knowledge questions and solve analytical problems in the field of biomechanics. The primary goal of implementing CBG was to provide more opportunities for lower-performing students to learn the material and to demonstrate that learning. To determine the efficacy of CBG to improve student learning, the primary measure was course grade distribution before and after implementation of CBG. The course grade distribution data indicated that CBG has primarily helped midperforming students to improve their grades. Because of the limitations of course grades as a measure of learning, we also performed analysis of student performance on successive attempts which indicated initial and secondary attempts are best, with student success declining on subsequent attempts. Anecdotally, many students improved performance, and thus their grade, on the (optional) final exam attempts. Limitations of the study include the limited course offerings with CBG (three), and that effects of COVID-19 may be confounding CBG data. Also, the approach places nearly all the grade on quizzes or exams. However, the approach could be modified to include homework grades, projects, and the like. Overall, the student learning in this course and implementation appears to be only positively affected, so this approach appears to have benefits in a biomechanics course.
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Aprendizaje , Estudiantes , Humanos , Fenómenos Biomecánicos , Curriculum , MotivaciónRESUMEN
Micropipette users commonly experience problems in the hand and upper limbs. Mechanical factors are thought to contribute to osteoarthritis (OA) initiation and progression in the basilar thumb joint. Finite element analysis can be used to examine the effects of micropipette design on contact mechanics measures within the basilar thumb joint. This pilot study examined the effect of micropipette handle diameter (12 mm, 25 mm, and 40 mm) and the presence of a finger rest on contact area, contact force, and peak contact pressure in the basilar thumb joint. All contact mechanics measures decreased with increasing handle diameter with significant differences between the 12 mm diameter and the 40 mm diameter handles (contact area down about 30 mm2, contact force down about 15 N, and peak pressure down about 1 MPa). Decreasing contact mechanics measures with increasing diameter matched our expectations that contact measures would decrease with a more open grip. Contact mechanics measures were higher (p < 0.05) with a finger rest for contact area and force. We expected peak contact pressure and contact area to decrease with the presence of a finger rest. The unexpected outcome may have been due to non-randomized testing order and fatigue during testing.
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Dedos , Pulgar , Proyectos Piloto , Fenómenos Biomecánicos , Mano , Fuerza de la Mano , Articulaciones de los DedosRESUMEN
The etiology of subchondral bone cysts (SBCs) is not fully understood. Mechanical trauma and fluid pressure are two mechanisms believed to cause their formation and growth. The equine stifle joint provides a natural animal model for studying SBCs. Computed tomography images of an extended yearling cadaveric stifle joint were segmented using ScanIP to isolate bones and relevant soft tissues. Three model geometries were created to simulate cyst sizes of approximately 0.03 cm3 (C1), 0.5 cm3 (C2), and 1 cm3 (C3). A uniform pressure resulting in 3000 N force was applied at the proximal end of the femur. Two types of simulations, filled-cyst and empty-cysts with uniform pressure loads, were used to simulate fluid pressurization. Our models suggest that shear stresses are likely the cause of failure for the subchondral bone and not pressurized fluid from the joint. Bone stresses did not begin to increase until cyst pressures were greater than 3 MPa. For all cyst sizes, fluid pressure must rise above what is likely to occur in vivo in order to increase bone shear stress, shown to be most critical. Synovial fluid pressure acts upon a porous trabecular bone network, soft tissue, and marrow, so the continuum nature of our model likely overestimates the predicted effects of fluid pressures.
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Quistes Óseos , Animales , Quistes Óseos/diagnóstico por imagen , Quistes Óseos/veterinaria , Epífisis , Fémur/diagnóstico por imagen , Caballos , Humanos , Rodilla de Cuadrúpedos , Estrés MecánicoRESUMEN
The basilar thumb joint is the joint second most commonly affected by osteoarthritis (OA) in the hand. Evaluation of dorsal subluxation of the thumb during a functional task such as key pinch could help assess OA risk. The objectives of this study were to determine the best imaging angle for measuring thumb dorsal subluxation during key pinch and to compare subluxation to corresponding OA grades on the Eaton-Glickel, Outerbridge, and International Cartilage Repair Society scales. Eleven cadaveric forearm specimens were rigged to simulate key pinch. A mobile c-arm captured anteroposterior (AP) view images of the hand and was rotated in 5 deg increments toward the ulnar aspect of the arm up to 60 deg. Dorsal subluxation was measured on each image and compared to determine which angle captured maximum subluxation. The resulting best imaging angle was used for comparisons between dorsal subluxation of the thumb and OA grades for the basilar thumb joint. The max subluxation was in the AP view for most specimens. There was a significant correlation between subluxation and the Eaton-Glickel grade (p = 0.003, R2 = 0.779), but not with either Outerbridge grades (p = 0.8018) or International Cartilage Repair Society grades (p = 0.7001). Our results indicate that dorsal thumb subluxation during key pinch should be measured in the AP view of the forearm/hand. Dorsal thumb subluxation during key pinch had a significant correlation with the Eaton-Glickel radiographic measure of OA but not with more accurate visual classifications of OA.
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Pulgar , HumanosRESUMEN
Laxity of the anterior oblique ligament (AOL) and/or the dorsoradial ligament (DRL) are believed to contribute to the progression of osteoarthritis in the trapeziometacarpal joint through increased dorsal subluxation. Stress radiographs during functional tasks, such as key pinch, can be used to evaluate such joint instability. Cadaveric experiments can explore joint contact pressures as well as subluxation under varying conditions, to gain knowledge about joint mechanics. The disturbance of supporting tissues, such as the joint capsule, during experiments may affect the recorded stability of the joint. To evaluate potential effects of opening the joint capsule and severing the AOL, eleven cadaveric specimens were rigged to simulate key pinch. An anteroposterior (AP) radiograph of the hand was recorded for each specimen while intact, after partially opening the joint capsule and after sectioning the AOL. First metacarpal subluxation levels were compared between the intact joint, partially open joint capsule, and sectioned AOL. Neither opening the joint capsule nor cutting the AOL had a statistically significant effect on metacarpal subluxation. The results indicate that partially opening the joint capsule has a negligible effect on joint mechanics and support recent studies that postulate that the AOL plays a less substantial role in preventing subluxation.
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Huesos del Metacarpo , Pulgar , Articulaciones Carpometacarpianas , Humanos , Ligamentos ArticularesRESUMEN
Equine subchondral bone cysts (SBCs) develop most often in the medial femoral condyle (MFC) of yearlings intended for performance. SBCs often cause lameness and can cause secondary injuries to the meniscus and tibial cartilage. A novel surgical technique using a transcondylar lag screw (TLS) across an MFC SBC has shown success in lameness resolution and radiographic healing of MFC SBC. In a previous study using finite element analysis, our lab showed that a TLS stimulated bone formation on the inner surface of the SBC and altered third principal stress vectors to change the direction of surface compression to align with the screw axis. This work extended the previous study, which was limited by the use of only one idealized SBC. Our objective was to test SBCs of several sizes and shapes in a newly developed equine stifle FEM with a TLS to determine how cyst size affects bone formation stimulation. This study found that a transcondylar screw is most effective in stimulating bone formation in cysts of greater height (proximal-distal). The TLS increases stress stimulus in the bone around the cyst to promote bone apposition and directs compression across the cyst. If full penetration of the screw through the cyst is possible, it is recommended that the transcondylar screw be used to treat subchondral bone cysts. For the treatment of smaller cysts that are not accessible by the current screw surgical approach, future work could study the efficacy of a dual-pitch headless screw that may reach smaller cysts.
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Análisis de Elementos Finitos , Osteogénesis , Animales , Quistes Óseos , Tornillos Óseos , Fémur , Caballos , TibiaRESUMEN
Use of piezoelectric materials to harvest energy from human motion is commonly investigated. Traditional piezoelectric materials are inefficient at low frequencies but composite structures can increase efficiency at these frequencies. Compliant layer adaptive composite stack (CLACS) is a new piezoelectric PZT (lead zirconate titanate) structure designed for orthopedic implants to use loads generated during walking to provide electrical stimulation for bone healing. The CLACS structure increases power efficiency and structural properties as compared to PZT alone. The purpose of this study was to investigate the effects of compliant layer and encapsulation thicknesses on strain-related parameters for CLACS predicted by finite element models. Percent changes in strain as compliant layer thickness increased were compared to percent changes in power experimentally produced by CLACS given similar geometries and loading conditions. Percent changes in PZT z-strain matched the trends for increases in experimental power, but was not directly proportional. PZT z-strain and radial strain increased as compliant layer and top and bottom encapsulation thickness increased. PZT z-strain and radial strain decreased as side encapsulation thickness increased for a normalized distributed force on the PZT. The overall goal of this study was to inform future design decisions regarding CLACS structures specifically for use in orthopedic implants.
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Materiales Biocompatibles/química , Suministros de Energía Eléctrica , Plomo/química , Prótesis e Implantes , Titanio/química , Circonio/química , Estimulación Eléctrica , Análisis de Elementos Finitos , Humanos , Caminata , Cicatrización de HeridasRESUMEN
OBJECTIVE: To predict the bone formation stimulus of a transcondylar screw across an equine subchondral bone cyst (SBC) in an equine medial femoral condyle (MFC). STUDY DESIGN: Finite element modeling (FEM) of an equine MFC with a 2 cm3 SBC under several transcondylar screw conditions. SAMPLE POPULATION: The right stifle of a yearling thoroughbred without stifle disease that had been euthanized for reasons unrelated to this study and donated to the University. METHODS: The FEM was derived from computed tomography of a yearling thoroughbred and analyzed in ABAQUS v6.14. The transcondylar screw was modeled as a 4.5-mm stainless steel cylinder. The region of interest was the centrodistal MFC, and bone stimulus was calculated. The stimulus threshold for bone formation (BFT) was >60 MPa and is presented as the percentage of total bone surface area (BFA) and frontal plane maps. Principal compressive stress vectors were also determined. Tested variables were daily cycles, load, and screw compression and position. RESULTS: At 750 cycles and 900-N load, <3% of the BFA exceeded the BFT. Increases in BFA > BFT occurred proportionally with load, screw compression, and daily cycles (steps). Compressive stress was oriented vertically on the SBC surface without a screw but aligned with the long axis of well-placed lag screws. Screw placement through the void also increased the number and magnitude of compressive vectors. CONCLUSION: This model predicted that a transcondylar lag screw across an MFC SBC increased surface BFA stimulation and reoriented the compression vector. Increasing screw compression, load, and steps per day increased the bone formation stimulus. CLINICAL SIGNIFICANCE: This study provides evidence that supports the use of a lag screw thorough an MFC SBC to promote bone formation.
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Quistes Óseos/veterinaria , Tornillos Óseos/veterinaria , Fémur/cirugía , Enfermedades de los Caballos/cirugía , Animales , Fenómenos Biomecánicos , Quistes Óseos/cirugía , Cadáver , Fémur/patología , Caballos , Rodilla de CuadrúpedosRESUMEN
OBJECTIVE: To predict bone and medial meniscal stresses and contact pressures in an equine stifle with a medial femoral condyle (MFC) intact or with a 2-cm3 subchondral bone void, under varying degrees of internal femoral rotation (IFR). STUDY DESIGN: Finite element model (FEM) of a cadaveric equine stifle loaded to 8000 N. METHODS: The FEM was constructed from computed tomography (CT) of the right, extended stifle of a yearling. The CT image was segmented into relevant anatomic structures and meshed into 4-node tetrahedrons. Bone material properties were assigned according to Hounsfield units, soft tissue properties were estimated from published data, and the model was loaded to 8000 N in 155° extension. RESULTS: The main stresses found in the intact MFC were in compression, with very small areas of shear and tension. Adding a 2-cm3 MFC void increased peak compression stress by 25%, shear by 50%, and tension by 200%. An MFC void also increased tension and shear placed on the medial meniscus by 30%. Under load, IFR of 2.5° and 5° increased MFC peak stresses 8%-21%. CONCLUSION: A 2-cm3 MFC void in an equine stifle FEM increased stress in the bone and meniscus. Internal femoral rotation slightly increased predicted bone stress. CLINICAL SIGNIFICANCE: Increases in bone and meniscal stress predicted in an MFC with a void provide evidence to understand the persistence of voids and mechanism of damage to the medial meniscus.
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Huesos/fisiología , Análisis de Elementos Finitos , Caballos , Animales , Fenómenos Biomecánicos , Humanos , Presión , Estrés MecánicoRESUMEN
Subchondral lucency (SCL), also referred to as subchondral bone cysts, can cause clinical problems in horses and humans. In humans, SCLs occur in youths and adolescents [1] due to mechanical factors (often related to athletics) and in skeletally mature individuals secondary to osteoarthritis (OA). In horses, SCL most commonly occurs in the medial femoral condyle (MFC) of growing horses (without OA), and causes lameness. The cause of equine SCL is debated, but bone trauma due to overload is the likely mechanism. Investigating the biomechanics of the healthy and cystic MFC is important to understand cyst growth and to provide a foundation for new treatment strategies. We hypothesize that SCL alters the mechanical environment of surrounding bone, which in the presence of continued loading, may lead to enlargement of the SCL. In this study, we developed and validated a finite element model of an equine stifle joint and investigated the stresses associated with varying sizes of SCL. We found substantial differences in tensile and shear stress at various stages of SCL development that suggest further bone damage leading to SCL enlargement. These data provide a first step in understanding of the altered mechanics of subchondral bone surrounding a SCL. Additional studies may provide the basis for improved treatment strategies for SCL in young horses, and may improve the understanding of SCL in humans.
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Quistes Óseos , Fémur , Articulaciones , Rodilla de Cuadrúpedos , Estrés Mecánico , Animales , Fenómenos Biomecánicos , CaballosRESUMEN
BACKGROUND: Scapholunate ligament injury is a commonly occurring carpal ligament injury. Pathology associated with scapholunate ligament injury depends on several factors such as the time after injury, type of injury (instability) and the development of osteoarthritis. The aim of this study was to investigate and compare contact mechanics in the lunocapitate and scaphocapitate joints in the normal, injured (scapholunate dissociation) and repaired (postoperative) wrist. METHODS: Four human subjects with scapholunate ligament dissociation participated in this study. MR images of normal (contralateral), injured and postoperative wrists were obtained during relaxed condition and during active light grasp. Relaxed MR images were used to construct model geometry (bones with cartilage) for the capitate, lunate and scaphoid. Kinematic transformations were obtained by using image registration between the unloaded and functionally loaded image sets. Joint surface contact mechanics were then calculated. FINDINGS: All contact measures (contact force, pressure, mean pressure and area) tended to increase with injury in both articulations. A significantly higher contact area was found in the injured scaphocapitate joint compared to normal. A significant increase in peak pressure was observed in the postoperative state compared to normal. INTERPRETATION: Injury to the scapholunate ligament increased contact measures, suggesting a risk for onset of osteoarthritis in both the scaphocapitate and lunocapitate joints. Surgical repair appeared to restore most measures of contact mechanics to near normal values, more so for the lunocapitate joint when compared to scaphocapitate joint. The elevated postoperative peak pressures indicate the difficulty to fully restore joint mechanics.
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Hueso Semilunar/fisiopatología , Hueso Escafoides/fisiopatología , Traumatismos de la Muñeca/fisiopatología , Articulación de la Muñeca/fisiopatología , Adulto , Fenómenos Biomecánicos , Femenino , Fuerza de la Mano , Humanos , Inestabilidad de la Articulación/cirugía , Ligamentos Articulares/cirugía , Imagen por Resonancia Magnética , Masculino , Fenómenos Mecánicos , Osteoartritis/patología , Periodo Posoperatorio , Presión , Rotación , Traumatismos de la Muñeca/cirugíaRESUMEN
The design of products and processes is an important area in engineering. Students in engineering schools learn fundamental principles in their courses but often lack an opportunity to apply these methods to real-world problems until their senior year. This article describes important elements that should be incorporated into a senior capstone design course. It includes a description of the general principles used in engineering design and a discussion of why students often have difficulty with application and revert to trial and error methods. The structure of a properly designed capstone course is dissected and its individual components are evaluated. Major components include assessing resources, identifying projects, establishing teams, understanding requirements, developing conceptual designs, creating detailed designs, building prototypes, testing performance, and final presentations. In addition to the course design, team management and effective mentoring are critical to success. This article includes suggested guidelines and tips for effective design team leadership, attention to detail, investment of time, and managing project scope. Furthermore, the importance of understanding business culture, displaying professionalism, and considerations of different types of senior projects is discussed. Through a well-designed course and proper mentoring, students will learn to apply their engineering skills and gain basic business knowledge that will prepare them for entry-level positions in industry.
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Ingeniería Biomédica/educación , Educación Profesional/organización & administración , Diseño de Equipo , Equipos y Suministros , Aprendizaje Basado en Problemas/organización & administración , Enseñanza/organización & administración , Ingeniería Biomédica/economía , Evaluación Educacional , Modelos Educacionales , Modelos Organizacionales , Estados UnidosRESUMEN
Measurement of static alignment of articulating joints is of clinical benefit and can be determined using image-based registration. We propose a method that could potentially improve the outcome of image-based registration by using initial manual registration. Magnetic resonance images of two wrist specimens were acquired in the relaxed position and during simulated grasp. Transformations were determined from voxel-based image registration between the two volumes. The volumes were manually aligned to match as closely as possible before auto-registration, from which standard transformations were obtained. Then, translation/rotation perturbations were applied to the manual registration to obtain altered initial positions, from which altered auto-registration transformations were obtained. Models of the radiolunate joint were also constructed from the images to simulate joint contact mechanics. We compared the sensitivity of transformations (translations and rotations) and contact mechanics to altering the initial registration condition from the defined standard. We observed that with increasing perturbation, transformation errors appeared to increase and values for contact force and contact area appeared to decrease. Based on these preliminary findings, it appears that the final registration outcome is sensitive to the initial registration.
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Automatización , Procesamiento de Imagen Asistido por Computador , Fuerza de la Mano , Humanos , Imagen por Resonancia Magnética , Presión , Radio (Anatomía)/anatomía & histología , Radio (Anatomía)/fisiología , Rotación , Articulación de la Muñeca/anatomía & histología , Articulación de la Muñeca/fisiologíaRESUMEN
Joint injuries and the resulting posttraumatic osteoarthritis (OA) are a significant problem. There is still a need for tools to evaluate joint injuries, their effect on joint mechanics, and the relationship between altered mechanics and OA. Better understanding of injuries and their relationship to OA may aid in the development or refinement of treatment methods. This may be partially achieved by monitoring changes in joint mechanics that are a direct consequence of injury. Techniques such as image-based finite element modeling can provide in vivo joint mechanics data but can also be laborious and computationally expensive. Alternate modeling techniques that can provide similar results in a computationally efficient manner are an attractive prospect. It is likely possible to estimate risk of OA due to injury from surface contact mechanics data alone. The objective of this study was to compare joint contact mechanics from image-based surface contact modeling (SCM) and finite element modeling (FEM) in normal, injured (scapholunate ligament tear), and surgically repaired radiocarpal joints. Since FEM is accepted as the gold standard to evaluate joint contact stresses, our assumption was that results obtained using this method would accurately represent the true value. Magnetic resonance images (MRI) of the normal, injured, and postoperative wrists of three subjects were acquired when relaxed and during functional grasp. Surface and volumetric models of the radiolunate and radioscaphoid articulations were constructed from the relaxed images for SCM and FEM analyses, respectively. Kinematic boundary conditions were acquired from image registration between the relaxed and grasp images. For the SCM technique, a linear contact relationship was used to estimate contact outcomes based on interactions of the rigid articular surfaces in contact. For FEM, a pressure-overclosure relationship was used to estimate outcomes based on deformable body contact interactions. The SCM technique was able to evaluate variations in contact outcomes arising from scapholunate ligament injury and also the effects of surgical repair, with similar accuracy to the FEM gold standard. At least 80% of contact forces, peak contact pressures, mean contact pressures and contact areas from SCM were within 10 N, 0.5 MPa, 0.2 MPa, and 15 mm2, respectively, of the results from FEM, regardless of the state of the wrist. Depending on the application, the MRI-based SCM technique has the potential to provide clinically relevant subject-specific results in a computationally efficient manner compared to FEM.
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Simulación por Computador , Análisis de Elementos Finitos , Imagen por Resonancia Magnética , Fenómenos Mecánicos , Traumatismos de la Muñeca/cirugía , Articulación de la Muñeca/cirugía , Adulto , Fenómenos Biomecánicos , Estudios de Factibilidad , Humanos , Masculino , Persona de Mediana Edad , Presión , Resultado del Tratamiento , Adulto JovenRESUMEN
This study was undertaken to assess magnetic resonance imaging (MRI)-based radiocarpal surface contact models of functional loading in a clinical MRI scanner for future in vivo studies, by comparison with experimental measures from three cadaver forearm specimens. Experimental data were acquired using a Tekscan sensor during simulated light grasp. Magnetic resonance (MR) images were used to obtain model geometry and kinematics (image registration). Peak contact pressures (PPs) and average contact pressures (APs), contact forces and contact areas were determined in the radiolunate and radioscaphoid joints. Contact area was also measured directly from MR images acquired with load and compared with model data. Based on the validation criteria (within 25% of experimental data), out of the six articulations (three specimens with two articulations each), two met the criterion for AP (0%, 14%); one for peak pressure (20%); one for contact force (5%); four for contact area with respect to experiment (8%, 13%, 19% and 23%), and three contact areas met the criterion with respect to direct measurements (14%, 21% and 21%). Absolute differences between model and experimental PPs were reasonably low (within 2.5 MPa). Overall, the results indicate that MRI-based models generated from 3T clinical MR scanner appear sufficient to obtain clinically relevant data.
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Imagen por Resonancia Magnética , Modelos Anatómicos , Articulación de la Muñeca/anatomía & histología , Fenómenos Biomecánicos , Fuerza de la Mano , Humanos , Presión , Articulación de la Muñeca/fisiologíaRESUMEN
We investigated the effects of scapholunate ligament injury on in vivo radiocarpal joint mechanics using image-based surface contact modeling. Magnetic resonance images of 10 injured and contralateral normal wrists were acquired at high resolution (hand relaxed) and during functional grasp. Three-dimensional surface models of the radioscaphoid and radiolunate articulations were constructed from the relaxed images, and image registration between the relaxed and grasp images provided kinematics. The displacement driven models were implemented in contact modeling software. Contact parameters were determined from interpenetration of interacting bodies and a linear contact rule. Peak and mean contact pressures, contact forces and contact areas were compared between the normal and injured wrists. Also measured were effective (direct) contact areas and intercentroid distances from the grasp images. Means of the model contact areas were within 10 mm(2) of the direct contact areas for both articulations. With injury, all contact parameters significantly increased in the radioscaphoid articulation, while only peak contact pressure and contact force significantly increased in the radiolunate articulation. Intercentroid distances also increased significantly with injury. This study provides novel in vivo contact mechanics data from scapholunate ligament injury and confirms detrimental alterations as a result of injury.
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Fenómenos Biomecánicos/fisiología , Ligamentos Articulares/lesiones , Imagen por Resonancia Magnética/métodos , Traumatismos de la Muñeca/patología , Articulación de la Muñeca/patología , Adulto , Anciano , Femenino , Humanos , Hueso Semilunar/lesiones , Hueso Semilunar/fisiopatología , Masculino , Persona de Mediana Edad , Hueso Escafoides/lesiones , Hueso Escafoides/fisiopatología , Estrés Mecánico , Traumatismos de la Muñeca/fisiopatología , Articulación de la Muñeca/fisiología , Adulto JovenRESUMEN
Disruption of the scapholunate ligament can cause a loss of normal scapholunate mechanics and eventually lead to osteoarthritis. Surgical reconstruction attempts to restore scapholunate relationship show improvement in functional outcomes, but postoperative effectiveness in restoring normal radiocarpal mechanics still remains a question. The objective of this study was to investigate the benefits of surgical repair by observing changes in contact mechanics on the cartilage surface before and after surgical treatment. Six patients with unilateral scapholunate dissociation were enrolled in the study, and displacement driven magnetic resonance image-based surface contact modeling was used to investigate normal, injured and postoperative radiocarpal mechanics. Model geometry was acquired from images of wrists taken in a relaxed position. Kinematics were acquired from image registration between the relaxed images, and images taken during functional loading. Results showed a trend for increase in radiocarpal contact parameters with injury. Peak and mean contact pressures significantly decreased after surgery in the radiolunate articulation and there were no significant differences between normal and postoperative wrists. Results indicated that surgical repair improves contact mechanics after injury and that contact mechanics can be surgically restored to be similar to normal. This study provides novel contact mechanics data on the effects of surgical repair after scapholunate ligament injury. With further work, it may be possible to more effectively differentiate between treatments and degenerative changes based on in vivo contact mechanics data.
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Ligamentos/lesiones , Articulación de la Muñeca/cirugía , Adulto , Fuerza de la Mano , Humanos , Ligamentos/fisiología , Ligamentos/cirugía , Hueso Semilunar , Masculino , Persona de Mediana Edad , Modelos Biológicos , Procedimientos de Cirugía Plástica , Hueso Escafoides , Resultado del Tratamiento , Articulación de la Muñeca/fisiología , Adulto JovenRESUMEN
The objective of this study was to validate the MRI-based joint contact modeling methodology in the radiocarpal joints by comparison of model results with invasive specimen-specific radiocarpal contact measurements from four cadaver experiments. We used a single validation criterion for multiple outcome measures to characterize the utility and overall validity of the modeling approach. For each experiment, a Pressurex film and a Tekscan sensor were sequentially placed into the radiocarpal joints during simulated grasp. Computer models were constructed based on MRI visualization of the cadaver specimens without load. Images were also acquired during the loaded configuration used with the direct experimental measurements. Geometric surface models of the radius, scaphoid and lunate (including cartilage) were constructed from the images acquired without the load. The carpal bone motions from the unloaded state to the loaded state were determined using a series of 3D image registrations. Cartilage thickness was assumed uniform at 1.0 mm with an effective compressive modulus of 4 MPa. Validation was based on experimental versus model contact area, contact force, average contact pressure and peak contact pressure for the radioscaphoid and radiolunate articulations. Contact area was also measured directly from images acquired under load and compared to the experimental and model data. Qualitatively, there was good correspondence between the MRI-based model data and experimental data, with consistent relative size, shape and location of radioscaphoid and radiolunate contact regions. Quantitative data from the model generally compared well with the experimental data for all specimens. Contact area from the MRI-based model was very similar to the contact area measured directly from the images. For all outcome measures except average and peak pressures, at least two specimen models met the validation criteria with respect to experimental measurements for both articulations. Only the model for one specimen met the validation criteria for average and peak pressure of both articulations; however the experimental measures for peak pressure also exhibited high variability. MRI-based modeling can reliably be used for evaluating the contact area and contact force with similar confidence as in currently available experimental techniques. Average contact pressure, and peak contact pressure were more variable from all measurement techniques, and these measures from MRI-based modeling should be used with some caution.
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Fenómenos Biomecánicos/fisiología , Huesos del Carpo/fisiología , Imagen por Resonancia Magnética/métodos , Modelos Biológicos , Articulación de la Muñeca/fisiología , Huesos del Carpo/diagnóstico por imagen , Cartílago Articular/fisiología , Simulación por Computador , Humanos , Hueso Semilunar/diagnóstico por imagen , Hueso Semilunar/fisiología , Presión , Radiografía , Radio (Anatomía)/diagnóstico por imagen , Radio (Anatomía)/fisiología , Reproducibilidad de los Resultados , Hueso Escafoides/diagnóstico por imagen , Hueso Escafoides/fisiología , Estrés Mecánico , Articulación de la Muñeca/diagnóstico por imagenRESUMEN
Investigations of in vivo joint mechanics are important for understanding the joint function under functional loading and the mechanisms of pathology. In this study we used magnetic resonance imaging (MRI) based joint contact modeling to evaluate in vivo joint contact mechanics in the human wrist. MRI scans were performed on the wrists of four subjects while they maintained light grasp of a cylinder, and with the same wrist relaxed. 3D models of the radius, scaphoid and lunate, including cartilage surface data, were constructed from the relaxed image data. These models were transformed into the loaded configuration, as determined from the grasp image data, and contact mechanics were evaluated. The resulting contact pressures, areas and forces were then analyzed for each articulation and for each subject. Contact areas were measured directly from grasp MRI images for comparison to the model predictions. The first-ever estimates for in vivo radioscaphoid and radiolunate contact pressure agreed reasonably well with previous cadaveric studies. This investigation also produced novel in vivo scapholunate contact results that were similar to radiolunate data. The specimen-specific contact area comparison generally showed substantial variability between the models and the direct measurements from MRI. On average, the models were within about 10% of the direct MRI measurements for radioscaphoid and scapholunate contact areas, but radiolunate contact areas from the model were only within 55% of the direct measurements. Overall, the results of the study suggest that MRI-based modeling has substantial potential for evaluation of in vivo joint contact mechanics, especially as technology and methodology improve.
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Huesos de la Mano/fisiología , Fuerza de la Mano/fisiología , Imagenología Tridimensional , Modelos Biológicos , Articulación de la Muñeca/fisiología , Muñeca/fisiología , Adulto , Femenino , Huesos de la Mano/diagnóstico por imagen , Humanos , Imagen por Resonancia Magnética , Masculino , Persona de Mediana Edad , Radiografía , Muñeca/diagnóstico por imagen , Articulación de la Muñeca/patologíaRESUMEN
A parametric investigation was conducted to determine the effects on the load estimation method of varying: (1) the thickness of back-plates used in the two-dimensional finite element models of long bones, (2) the number of columns of nodes in the outer medial and lateral sections of the diaphysis to which the back-plate multipoint constraints are applied and (3) the region of bone used in the optimization procedure of the density-based load estimation technique. The study is performed using two-dimensional finite element models of the proximal femora of a chimpanzee, gorilla, lion and grizzly bear. It is shown that the density-based load estimation can be made more efficient and accurate by restricting the stimulus optimization region to the metaphysis/epiphysis. In addition, a simple method, based on the variation of diaphyseal cortical thickness, is developed for assigning the thickness to the back-plate. It is also shown that the number of columns of nodes used as multipoint constraints does not have a significant effect on the method.