Center for Orthopaedic Biomechanics

The Center for Orthopaedic Biomechanics at the University of Denver applies engineering principles to investigate clinically relevant issues. Using a combination of experimental and computational tools, the Center performs research in in-vivo joint mechanics, human motion, musculoskeletal modeling, computational biomechanics, modeling fluid-solid interactions, wearable sensor systems, and implant device testing.

Housed in the Department of Mechanical & Materials Engineering at DU, the Center for Orthopaedic Biomechanics is a dynamic research environment committed to advancing orthopaedic biomechanics, improving patient outcomes and educating students. With current grants from NSF, NIH, implant manufacturers and research foundations, the Center is performing state-of-the-art research and has a strong record of publication and external support. The faculty is committed to student experiences at all levels: undergraduate, MS, PhD and post-doctoral fellows.

Computational Biomechanics Lab
For more than 10 years, the Computational Biomechanics Lab has developed computational models to evaluate the performance of orthopaedic implants and influence implant design. The lab has close relationships with orthopaedic implant manufacturers and experience developing custom model solutions to address a variety of clinically relevant questions. Current modeling efforts include high fidelity models of the knee, spine, hip and shoulder, and whole body musculoskeletal modeling.

The Computational Biomechanics Lab specializes in finite element analysis (FEA) techniques with unique capabilities in applying explicit FEA to predict joint mechanics. The lab has experience
- developing subject-specific models from image data,
- modeling complex changing contact conditions including wrapping of ligaments on bone/cartilage,
- predicting kinematics, contact mechanics and stresses/strains in structures,
- developing realistic loading conditions via musculoskeletal modeling, and
- characterizing the impact of variability sources.
Models developed are typically validated to subject-specific experimental data.

The Computational Biomechanics Lab has a strong record of journal publication and external research funding, and a commitment to working with students from undergraduates to PhD students.

The lab also has excellent working relationships with software partners:
- Simpleware (Exeter, UK)
- Hypermesh (Altair, Troy, MI), and
- Abaqus (Dassault Systemes, Providence, RI)
Human Dynamics Lab
The mission of the Human Dynamics Laboratory is to improve clinical diagnosis and treatment through:
- Biomechanical measurement and analysis
- Design of relevant quantitative tools and techniques
Students and researchers in the Human Dynamics Lab collaborate on experimental research projects with orthopaedic and rehabilitation specialists from University of Denver Athletic Department, University of Colorado School of Medicine, and the local Denver community. The Human Dynamics Lab also maintains strong ties to the Interdisciplinary Movement Science Laboratory (IMSL) located on the University of Colorado Anschutz Medical Campus.

The Human Dynamics Lab specializes in the following:
- measuring human movement, kinetic measurement, and muscle activity with a high degree of accuracy
- creating rigid-body musculoskeletal models of the spine and lower extremity
- developing novel tools for quantitative understanding and clinical transfer for rehabilitation
- high-density electromyography for spatial mapping of muscle activity
Probabilistic Mechanics Lab
The Probabilistic Mechanics Lab performs research themed around variability and its impact on mechanical systems. The laboratory works on both the innovation of new approaches in probabilistic analysis and the application of these techniques to a variety of fields including biomechanics, materials and nanotechnology, and design. Probabilistic and stochastic analysis represent an important emerging field and by its nature highly collaborative.

As a complement to experiments, finite element modeling and statistical analysis, probabilistic analysis provides a method of characterizing the potential impact of variability in parameters on performance. Specifically, input parameters are represented as distributions in order to predict a distribution of performance. In addition to understanding the probabilities associated with a specific level of performance, the input parameters or combination of inputs that most affect performance are also identified. The most common probabilistic approach is Monte Carlo simulation, which involves repeated sampling of the input parameters according to their distributions. While robust, Monte Carlo simulation is computationally expensive; much of the lab’s research has focused on the application of efficient probabilistic methods.

Research projects have investigated:
- Effects of microstructural variability on fatigue of aluminum alloys
- Monte Carlo prediction of polyethylene properties using molecular dynamics
- Understanding how patient, implant and surgical variability influences joint mechanics
- Development of statistical shape models to characterize anatomic variability
Cardiovascular Biomechanics Lab

The DU Cardiovascular Biomechanics Lab is focused on applied and translational research in the field of cardiovascular engineering. The scope of the research projects, directed by Dr. Ali Azadani, encompasses structural heart disease including transcatheter heart valve replacement and development of patient-specific therapeutic strategies.

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Biofluids Lab
The Biofluids Lab has performed a wide variety of projects applying fluid dynamics principles to address real world problems. Applications include: developing novel encapsulation techniques to improve drug delivery, characterizing damage mechanisms of therapeutic DNA and siRNA, and improving pulmonary drug delivery by quantifying particle deposition for patients on mechanical ventilators. The lab regularly combines theory, computational fluid dynamics (CFD) modeling and experimentation at multiple scales to develop novel solutions.

Recently, fluid-solid interactions have been investigated in collaborative work with the Computational Biomechanics Lab. Fluid-solid modeling crosses the disciplinary lines of traditional CFD and particle transport with those of structural mechanics to investigate current issues in biomechanics. Three projects are currently underway:
- Simulating the dynamic behavior of the human lung
- Modeling hydrostatic stiffening effects in bone
- Fluid-enhanced wear of a total knee replacement (TKR) attachment mechanism.
These projects demonstrate capabilities that span biological scales (e.g., the lung model runs from micrometer dimension alveolar sacs to centimeter dimensions for the trachea), strongly couple the tissue/cellular response and fluid mechanics (e.g., hydrostatic stiffening does not occur in dry bone), and in combination with probabilistic methods, drive understanding of the physical behavior (e.g., wear particle transport will be dependent on particle size and shedding location).
Biomaterials and Testing

The Biomaterials and Testing Lab performs a variety of testing to evaluate implant performance and characterize material properties. The lab’s testing experience ranges from coupons under ASTM standards to real components under conditions simulating in-service environments and from metals to polymers and composites. The lab’s expertise includes elastic-plastic behavior and fatigue crack initiation and growth.

Equipment includes large-scale and small-scale servo-hydraulic test machines including environmental chambers and a variety of load cells and extensometers, strain gage measurement systems, sample preparation equipment, optical and scanning electron microscopes, hardness testing and access to the DU machine shop for preparation of specimens and fabrication of custom fixtures.

Testing, failure analysis and consulting services are available.