Transmetatarsal amputees, especially those who are diabetic and dysvascular, face reamputation rates that are upwards of 36%, yet research to manage the health and mobility of this population with footwear and prosthetics are few and infrequent. Transmetatarsal amputees are a population that has already demonstrated a susceptibility to non?healing ulceration and amputation, conceptually putting them at an even greater risk for (re)amputation than dysvascular diabetic patients with an intact foot. In contrast to the risk of reamputation, transmetatarsal amputees retain ankle function and a weightbearing residuum. This gives them biomechanical advantages over proximal amputees (e.g. transtibial), highlighting the importance of protecting this group from requiring a proximal amputation (this does not even consider the additional detriments to reamputation such as health risk, diminished mobility, and cost). Despite this, while tremendous effort has been directed at management of the diabetic (intact) foot, there is a lack of research specific to the unique characteristics of transmetatarsal amputees. This population has lost the metatarsophalangeal joint, and thus has diminished forefoot function and forefoot plantar area. These factors may contribute to the noted increase in peak plantar pressures in transmetatarsal amputees, particularly under their residuum. Current prosthetic standards of care for this population includes an extra depth diabetic shoe, custom molded insert with toe filler and a foot plate. The purpose of the insert is to distribute plantar load, the toe filler controls limb motion and maintains shoe shape, and the foot plate provides a stiff forefoot/toe area to restore effective foot length. While these components have exhibited limited success in reducing plantar pressures (vs shoe alone), there is still substantial variability in the function of these components, particularly considering the variation in residual limb length in the transmetatarsal population. It is suspected that stiffer foot plates increase focal loading in the distal limb due to their rigidity; and that very flexible sole plates bend under the residual forefoot, increase peak pressures at the limb/toe filler interface. Therefore both the variability in component stiffness and the lack of control in regards to the location of flexing of these components, may contribute to detrimental function in the current standard of care. This proposal is to first evaluate the plantar pressure management and behavior of the standard of care prosthetic (these data are unreported currently), and then to identify a strategy to design optimal prosthetic componentry for transmetatarsal amputees, based on a combination of novel design features and on patient specific factors such as residual limb length and bodyweight. Due to the minimal data available as guidance, the project's success is dependent on a strong collaborative team including clinicians with specialties in amputee needs, a prosthetist and biomedical engineers involved in the development and use of advanced biomechanical measurement equipment and facilities to prototype orthopaedic devices. Success will be delineated by using specific peak plantar pressure limits and considering functional improvement. The success of this project is anticipated to have a profound positive impact on the management of transmetatarsal residual limbs.
People who have had a surgical amputation of their forefoot / toe region, especially those with diabetes, are at a high risk of needing an additional amputation higher up their leg. There is limited knowledge about how the design of footwear and shoe inserts work to protect these amputees from needing additional surgery. We will study existing devices as well as develop a new device that will do more to protect the limb of the amputee from further surgery, than is currently available.
