Changes in gait mechanics and muscle activity with wedge height in an orthopaedic boot.

Background: Orthopaedic boots with wedging are commonly used in the treatment of individuals with Achilles tendon rupture to immobilize the foot in plantar flexion and approximate tendon ends.

Research Question: To describe changes in muscle activity of the triceps surae and gait mechanics with the use of wedges in an orthopaedic boot immediately and after an accommodation period.

Methods: Muscle activity of the triceps surae and gait parameters (vertical ground reaction force, knee extension power, gait speed) were collected using surface electromyography and motion capture in 12 healthy individuals. Participants walked in an instrumented orthopaedic boot with 0, 3, and 5 wedges tested in random order. Participants were provided a one hour accommodation period where time spent walking was collected. This was followed by a repeat assessment of triceps surae activity and gait.

Results: Peak and integrated EMG in the medial gastrocnemius (p = 0.001, p < 0.001) and soleus (p = 0.010, p < 0.001) significantly decreased with increasing number of wedges. Peak and integrated EMG had a slight but non-significant decrease with increasing number of wedges in the lateral gastrocnemius (p = 0.151, p = 0.077). Vertical ground reaction force decreased (p = 0.019) and peak knee extension power increased (p = 0.003) with increasing number of wedges. There were no statistically significant differences in gait speed with wedges (p = 0.450). There were no significant changes in EMG or gait parameters from pre- to post-accommodation period.

Significance: A combination of factors yield decreased triceps surae activity in individuals wearing an orthopaedic boot with wedges - decreasing loading on the immobilized limb and shifting power generation proximally.