The influence of an orthopaedic walker boot on forefoot force.

Background: In the treatment of an Achilles tendon rupture the patients are commonly equipped with an orthopaedic walker boot with wedges. To what extent this influences the tensile force placed on the Achilles tendon is unclear.
Purpose: To assess the forefoot force and describe changes in muscle activity of the medial gastrocnemius, soleus and tibialis anterior when using one or three wedges during ambulation in a weightbearing orthopaedic walker boot.
Methods: The force on the forefoot was measured with a force sensor insole and muscle activity of the medial gastrocnemius, soleus and tibialis anterior were measured using surface electromyography in 10 healthy participants. Three different types of ambulation were performed (walking without crutches (unass.), walking with crutches (+crutch) and walking with crutches and verbal instructions to place body weight on heel (heel+crutch) with one and three heel wedges respectively.
Findings: The total peak force displayed an interaction where forefoot force decreased when wearing three wedges only for the +crutch ambulation type (80N, p=0.001) although there was a trend to decrease with three wedges also for the heel+crutch ambulation type (48N, p=0.05). The relative peak force on the forefoot showed a main effect with a significant decrease when using three wedges compared to one wedge across all three ambulation types (19.1%, p=0.009).
Interpretation: The force on the forefoot and hereby the Achilles tendon significantly decreased when using three wedges compared to one wedge. These findings have important implications for the rehabilitation post Achilles tendon rupture.
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