Metatarsals do not move as a unit
By Katie Bell
Diabetes mellitus and peripheral neuropathy are associated with altered movement in individual metatarsal segments that is not always consistent with movement of the forefoot as a whole, according to research from Chicago that may have implications for foot ulcer prevention.
“We think differences in the magnitude and quality of motion between individual metatarsals may be related to the location of tissue breakdown,” said first author Frank DiLiberto, PT, PhD, OCS, FAAOMPT, an assistant professor in the Department of Physical Therapy at Rosalind Franklin University of Medicine and Science in Chicago. “Further work should be performed to fully delineate this potential relationship.”
The study included 15 participants with diabetic peripheral neuropathy who did not have deformity or ulceration and 15 healthy matched controls. Researchers examined in vivo kinematic angular excursions of individual metatarsal segments and a unified forefoot segment as participants walked barefoot on a level walkway. Specifically, a five-segment foot model that included the first, third, and fifth metatarsals, calcaneus, and tibia was used to investigate relative 3D angular excursions throughout the terminal stance phase of walking.
In the patients with diabetic neuropathy, sagittal plane motion was reduced in all individual metatarsals and the unified forefoot relative to the controls, while only third metatarsal excursion was reduced in the frontal plane. In the transverse plane, participants with diabetic neuropathy had reduced motion in the third and fifth metatarsals and the unified forefoot.
Coupling of individual metatarsals and unified forefoot motion was strong in the sagittal plane in both groups, but variable coupling in the frontal and transverse planes suggests the metatarsals do not collectively function as a unit during walking. The findings were published in October 2015 by Gait & Posture.
Although the study authors suggest individual metatarsal kinematics provide further understanding of the diabetic neuropathic process, they recommend additional study to determine if the observed kinematic profile is associated with the development and location of deformity and tissue breakdown in individuals with diabetic peripheral neuropathy.
“The differential motion within the forefoot in people with diabetes mellitus and peripheral neuropathy, or in comparison to normal foot function, may be related to elevated pressures and increased ulceration risk [not specifically assessed in this study]. It is reasonable to continue to use orthotics to address elevated plantar pressures and try to optimize in-shoe kinematics,” DiLiberto said. “While I do not know of studies demonstrating the effect of intrinsic strengthening or metatarsal mobilization in people with diabetes mellitus or peripheral neuropathy, it may be beneficial to include these components in preventive protocols.”
The differences evident in the magnitude and coupling between motion in the individual metatarsals and the unified forefoot suggest it may be more accurate to consider forefoot movement in terms of a medial segment and a lateral segment rather than a single forefoot region.
“Our data suggest that measuring individual metatarsal motion is not the same as measuring unified forefoot motion,” DiLiberto said. “Based on our findings, we recommended the use of a two-segment forefoot model to better represent foot function. This recommendation may be the most relevant in the examination of transverse and frontal plane motion. Further work is also recommended to determine the clinical relevance and impact of a more specific modeling approach. More specific modeling may lead to better detection of pathology and guide interventions.”
The approach taken by DiLiberto and colleagues represents a paradigm shift in research design that could have significant clinical implications for patients with diabetes, said Smita Rao, PT, PhD, assistant professor of physical therapy at New York University in New York City.
“This is a novel approach compared to many existing studies because most current foot models assess the forefoot as a whole,” Rao said. “Studying metatarsal motion in individuals with diabetes and neuropathy but no deformity may provide valuable insights that are important to develop targeted intervention that will help prevent deformities in this population.”
Rao and colleagues analyzed forefoot motion in terms of its medial and lateral components in a 2010 study of 15 individuals with diabetic neuropathy and 15 controls, but some of their findings differ from those of DiLiberto et al.
“In contrast to our previous work, where we found a rigid first metatarsal segment and less rigid lateral forefoot [in the group with diabetes], DiLiberto et al found a normal first metatarsal and a more rigid third metatarsal,” Rao said. “These phenotypes of foot function and their relevance to deformity progression must be investigated in future studies.”
Katie Bell is a freelance writer based in New York City.
DiLiberto FE, Tome J, Baumhauer JF, et al. Individual metatarsal and forefoot kinematics during walking in people with diabetes mellitus and peripheral neuropathy. Gait Posture 2015;42(4):435-441.
Rao S, Saltzman CL, Yack HJ. Relationships between segmental foot mobility and plantar loading in individuals with and without diabetes and neuropathy. Gait Posture 2010;31(2):251-255.