PROJECT SUMMARY/ABSTRACT
The first metatarsophalangeal joint (MTPJ1) is one of the sites most often affected by osteoarthritis, leading to a
condition called hallux rigidus (HR). This is very common, estimated to affect 25% of the adult population and
increasing in prevalence with age. The number of patients seen by the Veterans Health Administration (VHA) for
HR has more than doubled over the last decade. In contrast to degenerative osteoarthritis at the hip and knee,
which is commonly treated with joint replacement arthroplasties, the most common surgical treatment for severe
HR is arthrodesis, which eliminates joint function. This approach does not allow modification of footwear,
interferes with some activities (e.g., yoga, Pilates) and may lead to secondary complications such as
metatarsalgia and mobility restrictions. To date, various designs for MTPJ1 arthroplasties have been proposed,
but none have been particularly successful, with high failure rates due to loosening and regular reports of
migration of the implant. This may be in part because of the relatively small amount of cortical bone in the
metatarsal head and proximal phalanx regions, making it difficult to achieve adequate fixation of the prosthetic
components. Development of new implants aimed at addressing these problems has been limited by the
sparseness of the literature regarding the mechanical environment of the MTPJ1. Similarly, there is very little
detailed information on the typical 3D movement of the MTPJ1 required during activities of daily living. Our recent
work has established the groundwork for a computational-based modeling workflow that is intended to optimize
the design of a novel MTPJ1 implant, and we have had some initial success in generating new, evidence-based
implant concepts. In this project, we intend to advance this work, increasing our ability to further MTPJ1 implant
technology through computational and robotic gait simulation-based testing. This will ultimately lead to improved
patient outcomes. We intend to achieve these aims by: 1) characterizing pathological and healthy MTPJ1
function during different activities of daily living; 2) using a robotic gait simulator to measure the effectiveness of
existing and novel MTPJ1 implants at restoring joint function; and 3) further refining our musculoskeletal and
finite element models of MTPJ1 to improve their accuracy and provide further validation of their ability to generate
useful results. We believe this work has the potential to reinvigorate the study of MTPJ1 arthroplasty, which at
present is primarily driven by ideas and not data. The knowledge disseminated from this research will allow
surgeons and patients to make better decisions regarding surgical treatments for HR. Specifically, these data
will help better understand the disease process of HR and lead to more physiologic MTPJ1 replacements, that
will ultimately result in an improvement in mobility and quality of life for Americans with HR. Upon completion,
our group will have obtained the expertise to undertake a large clinical trial investigating surgical treatment of
HR with the goals of developing a more rigorous classification of HR, and better insight into the various causes
of MTPJ1 pain (e.g., dorsal first metatarsal osteophytes or MTPJ1 cartilage damage or sesamoid arthropathy).