Effects of Surgical Decompression on Ankle Stiffness During Gait: Biomechanical Differences within a Cohort of Chiari Patients


Symptoms commonly associated with Chiari 1 include headache, clumsiness, grip weakness, instability of gait, dizziness, paresthesiae and numbness. Furthermore, cervical myelopathy is associated with muscular fatigue that can affect activities of daily living.


This study examined the gait of 15 female subjects (eight who had previously undergone surgical decompression) in accordance with an IRB-approved protocol. The average age was 44.3 ±9.9yrs, height 1.6 ±0.06m and weight 78.3 ±24.2kg. Subjects were evaluated in a standard gait lab settting, using a ten camera Vicon system and two AMTI forceplates. Subjects walked at a selfselected speed. Data for three trials were recorded and processed using the Vicon software for performing inverse dynamics analyses. The focus of the gait evaluation was on the plantarflexor moment at the ankle joint during the push-off phase of gait.


Chiari patients who had undergone decompression surgery had significantly higher values for both the magnitude of the maximum ankle moment (119 vs 97 Nm, p=0.01) and plantarflexor muscle stiffness (273.7 vs 233 Nm/rad, p< 0.05).

Discussion and Conclusions

The key conclusion from this gait study on a limited cohort of Chiari 1 patients is that decompression surgery is associated with higher ankle joint moments and plantarflexor muscle stiffness during steady overground locomotion. This could be related to recovery from symptoms related to syringomyelia or other pathologies affecting muscle tone. Further research needs to be conducted to examine whether similar findings occur at more proximal joints and whether these biomechanical measurements relate to qualitative improvements in the gait of Chiari patients following decompression surgery.


The authors acknowledge generous funding from the Conquer Chiari Foundation.