Biomedical subjects

Nicole M Grosland

Publications and source records attributed to Nicole M Grosland.

8 recordsLinked to original sources

PubMed2006

Cartilage contact pressure elevations in dysplastic hips: a chronic overload model.

BACKGROUND: Developmental dysplasia of the hip (DDH) is a condition in which bone growth irregularities subject articular cartilage to higher mechanical stresses, increase susceptibility to subluxation, and elevate the risk of early osteoarthritis. Study objectives were to calculate three-dimensional cartilage contact stresses and to examine increases of accumulated pressure exposure over a gait cycle that may initiate the osteoarthritic process in the human hip, in the absence of trauma or surgical intervention. METHODS: Patient-specific, non-linear, contact finite element models, constructed from computed tomography arthrograms using a custom-built meshing program, were subjected to normal gait cycle loads. RESULTS: Peak contact pressures for dysplastic and asymptomatic hips ranged from 3.56 - 9.88 MPa. Spatially discriminatory cumulative contact pressures ranged from 2.45 - 6.62 MPa per gait cycle. Chronic over-pressure doses, for 2 million cycles per year over 20 years, ranged from 0.463 - 5.85 MPa-years using a 2-MPa damage threshold. CONCLUSION: There were significant differences between the normal control and the asymptomatic hips, and a trend towards significance between the asymptomatic and symptomatic hips of patients afflicted with developmental dysplasia of the hip. The magnitudes of peak cumulative contact pressure differed between apposed articular surfaces. Bone irregularities caused localized pressure elevations and an upward trend between chronic over-pressure exposure and increasing Severin classification.

Journal Article↗

PubMed2006

Intra-articular contact stress distributions at the ankle throughout stance phase-patient-specific finite element analysis as a metric of degeneration propensity.

A contact finite element (FE) formulation is introduced, amenable to patient-specific analysis of cumulative cartilage mechano-stimulus attributable to habitual functional activity. CT scans of individual human ankles are segmented to delineate bony margins. Each bone surface is projected outward to create a second surface, and the intervening volume is then meshed with continuum hexahedral elements. The tibia is positioned relative to the talus into a weight-bearing apposition. The articular members are first engaged under light preload, then plantar-/dorsi-flexion kinematics and resultant loadings are input for serial FE solutions at 13 instants of the stance phase of level walking gait. Cartilage stress histories are post-processed to recover distributions of cumulative stress-time mechano-stimulus, a metric of degeneration propensity. Consistency in computed contact stress exposures presented for seven intact ankles stood in contrast to the higher magnitude and more focal exposures in an incongruously reduced tibial plafond fracture. This analytical procedure provides patient-specific estimates of degeneration propensity due to various mechanical abnormalities, and it provides a platform from which the mechanical efficacy of alternative surgical interventions can be estimated.

Ankle Injuries↗

PubMed2006

Loading and boundary condition influences in a poroelastic finite element model of cartilage stresses in a triaxial compression bioreactor.

BACKGROUND: We developed a poroelastic finite element (FE) model of cartilage in dynamic triaxial compression to parametrically analyze the effects of loading and boundary conditions on a baseline model. Conventional mechanical tests on articular cartilage such as confined and unconfined compression, indentation, etc., do not fully allow for modulation of compression and shear at physiological levels whereas triaxial compression does. A Triaxial Compression Bioreactor, or TRIAX, has been developed to study chondrocyte responses to multi-axial stress conditions under cyclic loading. In the triaxial setting, however, a cartilage explant's physical testing environment departs from the ideal homogeneous stress state that would occur from strict linear superposition of the applied axial and transverse pressure. METHOD OF APPROACH: An axisymmetric poroelastic FE model of a cartilage explant (4 mm diameter, 1.5 mm thick) in cyclic triaxial compression was created. Axial and transverse loads (2 MPa at 1 Hz.) were applied via a platen and containment sheath. Parameters of interest included the rise time and magnitude of the applied load, in addition to the containment sheath modulus and the friction coefficient at the cartilage/platen interfaces. Metrics of interest in addition to whole explant axial strain included axial (surface normal) stress, shear stress, pore pressure, and the fluid load carriage fraction within the explant. RESULTS: Strain results were compared to experimental data from explants tested in the TRIAX under conditions similar to the baseline model. Explant biomechanics varied considerably over numbers of load cycles and parameter values. Cyclic loading caused an increase in accumulated strain for the various loading and boundary conditions. CONCLUSIONS: Unlike what would be expected from linear superposition of the homogeneous stresses from the applied axial and transverse pressure, we have shown that the stress state within the TRIAX is considerably heterogeneous. Both the boundary influences (variation in the sheath modulus and friction coefficient) and the loading history (due to poroelastic material behavior) interact in a highly nonlinear manner to influence that heterogeneity.

Bioreactors↗

PubMed2004

New methods for assessing cartilage contact stress after articular fracture.

Progress in reducing the incidence and severity of posttraumatic arthritis depends in part on avoiding deleterious stress levels at residual local incongruities. Systematic efforts to elucidate factors adversely influencing cartilage's mechanical environment in turn depend on the availability of suitable modalities to assess intraarticular contact stresses. This has been and remains a challenging biomechanical problem. Technologic approaches used in the past have included mathematical analyses and indwelling physical sensors, each with advantages and limitations. Two emerging, mutually complementary capabilities show promise of dramatically altering the state of the art in this important field. The first of these methodologies, voxel-based contact finite element analysis, provides accurate computational estimates of cartilage stress on a patient-specific basis, and does so while accommodating arbitrarily idiosyncratic patterns of local articular incongruity. The second methodology, instrumentational, involves transient pressure distribution recordings using specially designed piezoresistive array sensors. Operational considerations for both of these new assessment technologies are described, and promising directions for future development are outlined.

Biomechanical Phenomena↗

PubMed2004

Adaptive meshing technique applied to an orthopaedic finite element contact problem.

Finite element methods have been applied extensively and with much success in the analysis of orthopaedic implants. Recently a growing interest has developed, in the orthopaedic biomechanics community, in how numerical models can be constructed for the optimal solution of problems in contact mechanics. New developments in this area are of paramount importance in the design of improved implants for orthopaedic surgery. Finite element and other computational techniques are widely applied in the analysis and design of hip and knee implants, with additional joints (ankle, shoulder, wrist) attracting increased attention. The objective of this investigation was to develop a simplified adaptive meshing scheme to facilitate the finite element analysis of a dual-curvature total wrist implant. Using currently available software, the analyst has great flexibility in mesh generation, but must prescribe element sizes and refinement schemes throughout the domain of interest. Unfortunately, it is often difficult to predict in advance a mesh spacing that will give acceptable results. Adaptive finite-element mesh capabilities operate to continuously refine the mesh to improve accuracy where it is required, with minimal intervention by the analyst. Such mesh adaptation generally means that in certain areas of the analysis domain, the size of the elements is decreased (or increased) and/or the order of the elements may be increased (or decreased). In concept, mesh adaptation is very appealing. Although there have been several previous applications of adaptive meshing for in-house FE codes, we have coupled an adaptive mesh formulation with the pre-existing commercial programs PATRAN (MacNeal-Schwendler Corp., USA) and ABAQUS (Hibbit Karlson and Sorensen, Pawtucket, RI). In doing so, we have retained several attributes of the commercial software, which are very attractive for orthopaedic implant applications.

Biomechanical Phenomena↗

PubMed2003

Impact of impaired wrist motion on hand and upper-extremity performance(1).

PURPOSE: To quantify and compare the disabilities caused by reduced and absent wrist motion using objective measurements of task performance and perceived disability, and to assess the compensatory motions of the shoulder, elbow, forearm, and trunk caused by impaired wrist motion. METHODS: A clinical study of 21 normal subjects was done to measure physical performance and to assess wrist function under conditions of reduced (30 degrees flexion and 30 degrees extension) and nearly absent wrist motion using established physical tests and questionnaires (Disabilities of the Arm, Shoulder, and Hand [DASH], Patient Rated Wrist Evaluation [PRWE], and a study-specific survey). The clinical study also measured compensatory motions of the shoulder, elbow, forearm, and trunk. RESULTS: Average times to perform the Jebsen test and activities of daily living (ADLs) test increased for both motion-restricted conditions of the wrist but did not differ significantly between the conditions. Questionnaire scores regarding function were significantly worse for both motion-restricted conditions and poorest for nearly absent motion. Average compensatory motions in the extremity and trunk statistically increased for both motion-restricted conditions but were not marked and did not differ between the conditions. High variability among subjects occurred in all physical tests and questionnaires for both motion-restricted conditions. CONCLUSIONS: Perceived disability from reduced wrist motion appeared greater than measured functional loss using common physical tests and outcome surveys.

Activities of Daily Living↗

PubMed2002

A voxel-based formulation for contact finite element analysis.

To date, voxel-based finite element models have not been feasible for contact problems, owing to the inherent stair-step boundary discontinuities. New preprocessing techniques are reported herein to mesh these boundaries smoothly, for purposes of contact stress analysis. Further, new techniques are reported to concentrate the mesh resolution automatically near the articular surface, thus reducing the problem size to levels compatible with executing nonlinear problems on contemporary engineering workstations. Close approximations to Hertzian analytical solutions were obtained for spherical and cylindrical geometries meshed in this manner, and an illustrative anatomical contact problem of the human hip joint is presented.

Computer Simulation↗

PubMedDate not supplied

Impact of simulated proximal interphalangeal arthrodeses of all fingers on hand function.

PURPOSE: To evaluate the impact of simulated proximal interphalangeal (PIP) arthrodeses on hand performance and to assess the resulting compensatory metacarpophalangeal (MCP) joint motions in healthy subjects. METHODS: Fifteen healthy subjects were tested under 2 conditions: (1) with unrestricted distal interphalangeal, PIP, and MCP joints and (2) with the PIP joint fixed at 40 degrees of flexion in all 4 fingers of 1 hand and unrestricted MCP and distal interphalangeal joints. Subjects performed the Jebsen hand function test and 13 activities of daily living. Perceived difficulty in performing tasks was assessed with a study-specific questionnaire. The motion of each finger was monitored using a motion analysis system. RESULTS: The average time to complete the Jebsen test did not increase significantly with simulated PIP arthrodesis, nor did subjects perceive the tasks to be more difficult. Activities of daily living tasks requiring power grasp did not show significant increases in MCP flexion or abduction. Precision handling tasks requiring greater PIP joint flexion did show increased MCP flexion and were associated with greater perceived difficulty. CONCLUSIONS: Our study showed a minimal overall impact from simulated arthrodeses of all 4 fingers at the PIP joints in 40 degrees of flexion when measured by selected lower-demand activities of daily living in healthy subjects. Precision handling tasks that normally use higher degrees of PIP joint flexion, however, were perceived to be more difficult to perform and required greater compensatory motion at the MCP joints. This study does not address directly the impairment that patients with generalized hand arthritis may experience after PIP joint arthrodesis. TYPE OF STUDY/LEVEL OF EVIDENCE: Prognostic, Level I.

Activities of Daily Living↗