The effect of ankle foot orthosis alignment on walking in individuals treated for traumatic lower extremity injuries

Limb salvage surgeries are performed to treat a variety of lower limb pathologies and traumatic injuries. Individuals who have undergone limb salvage surgeries may require an ankle foot orthosis (AFO) to compensate for limb impairments and restore walking ability. Understanding the effects of AFO design parameters on gait biomechanics is important to refine AFO prescription criteria. In this study sagittal plane kinematic and kinetic data, muscle activity and alignment preference were examined as individuals treated for traumatic lower extremity injuries (N=12) walked over level ground with Plantarflexed (PF), Neutral, and Dorsiflexed (DF) aligned AFOs. A PF alignment resulted in earlier center of pressure progression (p<0.007) and a resulting decrease in both internal knee extensor moment (p<0.001) and quadriceps and soleus muscle activity (p<0.014) compared to the Neutral and DF alignments without affecting the lower limb support moment. A clear alignment preference was observed, with eight participants preferring the PF over the Neutral and DF alignments. The increase in internal knee extensor moment between the PF and DF alignments in the present study is consistent with previous investigations in other patient populations, suggesting a more DF aligned AFO may affect the knee joint moment similarly across patient populations. The results of this study suggest AFO alignment is an important design parameter that affects ankle and knee joint moments and muscle activity and should be carefully considered during AFO design and clinical fitting.