Interpretation of the observed biomechanical alterations
Comprehensive gait analysis is a fundamental step in identifying gait
disorders associated with amputation. However, to date, there is limited
evidence regarding biomechanical alterations in patients who have
undergone toe amputation. One study showed that patients who had
undergone first ray amputation displayed poor walking capacity with
kinematic alterations in hip extension4. The current
study expands on this previous knowledge by showing that patients with a
history of multiple non-first ray amputations displayed biomechanical
alterations characterized by a lack of push-off accompanied by kinematic
changes in lower hip extension. These biomechanical alterations would be
attributed, at least in part, to the loss of function in the second to
fourth toes. Toe amputation reduces leverage, which is required to
produce plantar flexor torque during the terminal stance. It should be
noted that the patient included in this study had undergone amputation
of the third toe in the contralateral limb, suggesting that the poor
walking capacity and biomechanical alterations might be a consequence of
bilateral toe amputation.
Notably, the biomechanical alterations in the ipsilateral limb were
accompanied by an increased vertical first peak GRF in the contralateral
limb. The identification of biomechanical alterations in the
contralateral limb is valuable, as this may provide insight into
musculoskeletal comorbidities after amputation. Increased axial lower
limb loading at heel contact may lead to faster progression of existing
osteoarthritis13. Knee osteoarthritis is a major
comorbidity associated with amputation14. Although no
data are available on the prevalence of these comorbidities after
partial toe amputation, our findings serve as a foundation for future
cohort studies on musculoskeletal comorbidities after partial toe
amputation.
Considering
that, nearly one-third of the individuals require re-amputation within 1
year following an initial toe amputation15, an
enhanced understanding of the disease trajectory after initial
amputation is needed. Elevated plantar pressure is a major risk factor
of diabetic ulcers especially at metatarsal16, a
precursor for amputation17. Our patient displayed
reduced step length in the ipsilateral limb, which reduces peak plantar
pressure during level walking18. On the other hand,
the COP during the terminal stance in the ipsilateral foot was localized
at the first metatarsal, which may cause excessive plantar pressure in
this region, the common location for foot ulcers19.
These altered biomechanics in the ipsilateral foot highlight the
importance of careful observation following the initial amputation to
prevent secondary amputation.