Exponent provides the highest quality technical and scientific support to assist our clients with complex issues related to spine biomechanics. We specialize in providing rapid, focused, market-sensitive solutions to complex issues. Our engineers have extensive expertise in spine implant evaluation, spine implant retrieval analysis, finite-element modeling, and evaluation of spine biomechanics and spinal injuries, and we are widely published in these areas. We use these capabilities to help our clients solve a variety of challenges associated with device design, device performance, and interaction with the environment.
Spine Implant Performance Evaluation
We perform mechanical and materials evaluation of spinal implants for clients with needs pertaining to patent evaluation/infringement issues, third-party design reviews, or in vitro testing for FDA regulatory submissions. Evaluations can also be conducted to assess spine implant performance, to answer specific questions related to materials (metal, polymers, and combinations) and functionality (dynamic stabilization, fusion, or motion preservation). We also have extensive experience in conducting biomechanical evaluations using cadaveric models and validated finite-element (FE) models of the spine. Our experience with in vivo animal models also can provide insight into mechanisms of metal ion release, tissue reaction (histology), and scanning microscopic evaluation (SEM) of spinal devices.
Implant Retrieval Analysis
We have established international retrieval programs to collect explanted spine implants, including fusion instrumentation, total disc replacements, and dynamic stabilization devices. As part of this program, we have developed custom-made implant retrieval kits and device-specific forms. Our international repository has provided us with the opportunity to examine retrieved spinal implants for wear patterns, failure mechanisms, corrosion, and deformation. We also have the expertise to assist our clients with evaluation of fluid and tissue surrounding the implant, including histology, trace metal, and particle analysis.
Spine-Related Testing Capabilities
Our laboratories have state-of-the art equipment and capabilities such as:
- MTS® Spine Wear Simulator
- Able to simulate International Organization for Standardization (ISO) 18192 and American Society for Testing and Materials (ASTM) F2423 and adaptable to custom loading profiles
- Testing load frames
- Load range from 100N to 30kN; displacement range from micron resolution to as much as 1000 mm of travel
- Temperature-controlled testing environments
- Custom fixtures created at competitive machine-shop rates
- Standard ASTM methods
- Tissue testing applications: ligaments, muscle, disc, endplates
- Cadaveric testing
- Established relationships with donor foundations
- Developed experimental protocols and obtained institutional review board (IRB) approval
- Dissection and specimen preparation facilities on site
- Imaging capabilities
- High-resolution imaging for bone, soft tissues, and implants
- Real-time radiographic imaging
- Access to computed tomography (CT), magnetic resonance imaging (MRI), and dual energy x-ray absorptiometry (DEXA)
Finite-Element Modeling 
Our group has extensive experience developing and using detailed, validated FE models of the thoracolumbar and cervical spine for evaluation of surgical procedures and specific spinal instrumentation. Specifically, we can incorporate the following:
- Subject-specific model geometry based on medical images (x-ray, CT, MRI, intravascular ultrasound (IVUS), microCT, optical microscopy, cryosections)
- Non-homogeneous bone moduli based on bone mineral density (via calibrated CT)
- Nonlinear, tensile-only representations for major spinal ligaments
- State-of-the-art intervertebral disc representation
- Robust contact algorithms for facet interactions
- Customized implant geometries
We have an onsite computational cluster capable of handling high-performance computational analyses. Our cluster includes:
- 48 AMD Opteron™ computing ores
- High-speed Myrinet interconnects
- 96 gigabytes RAM
- 4 terabytes of storage
Additional Research Experience
In addition to the expertise described previously, our engineers have wide-ranging research knowledge and are extensively published in:
- Burst fractures and osteoporotic vertebral compression fractures
- Facet joint mechanics
- Intervertebral disc mechanics (annulus fibrosus, nucleus pulposus, and endplate)
- Spine finite-element analysis
- Spinal manipulation
- Tissue and trace-metal analysis
- Wear and corrosion evaluation of retrieved implants
- Medical imaging evaluations and characterization
- In vivo characterization of low-back pain