Background: The floor-reaction ankle-foot orthosis is commonly prescribed for children with cerebral palsy who walk with excessive ankle dorsiflexion and excessive knee flexion during the stance phase of gait. The purposes of this study were to evaluate the efficacy of this orthosis objectively and to identify clinical parameters that may compromise its function.
Methods: All children with cerebral palsy who had comprehensive gait analyses in both barefoot and braced walking conditions during a single visit to our Motion Analysis Laboratory between January 2001 and August 2007 were identified. Kinematic study parameters included mean sagittal dynamic range of motion of the ankle in stance, peak ankle dorsiflexion in stance, peak knee extension in midstance, and mean foot progression angle in stance. The minimum sagittal knee moment in midstance was also examined in this study for subjects who walked without assistive devices. Range-of-motion and skeletal alignment data obtained from the physical examination record of each subject included knee flexion contracture, popliteal angle, hip flexion contracture, and thigh-foot angle.
Results: Twenty-seven children had quantitative gait analyses (barefoot and with the orthoses in the same visit). The mean sagittal plane dynamic range of motion of the ankle in stance was reduced from 23 degrees +/- 9 degrees when walking barefoot to 10 degrees +/- 3 degrees when the orthosis was worn (p < 0.001), and the mean peak knee extension in midstance improved from 29 degrees +/- 14 degrees of flexion to 18 degrees +/- 14 degrees of flexion (p = 0.013). Strong negative linear correlations were found between the magnitude of knee and hip flexion contractures on physical examination and the amount of peak knee extension in midstance (r = -0.784 and r = -0.705, respectively). A strong positive correlation was found between the mean minimum sagittal knee moment in midstance and the amount of peak knee extension in midstance (r = 0.820). Our investigation did not provide evidence of a correlation between peak knee extension in midstance and any of the following parameters in the orthosis: clinical examination measurements of the thigh-foot angle (r = 0.120), the popliteal angle (r = -0.300), or the mean foot progression angle in the stance phase of gait (r = -0.188).
Conclusions: The floor-reaction ankle-foot orthosis is effective in restricting sagittal plane ankle motion during the stance phase of gait in patients with cerebral palsy. As a result, improvements in knee extension and the sagittal plane knee extensor moment in stance phase are achieved. The best outcomes with this orthosis, as determined by peak knee extension in midstance, were seen in the subjects with knee and hip flexion contracture of < or =10 degrees . Knee and hip flexion contractures of > or =15 degrees were found to limit the efficacy of the orthosis in controlling knee extension in midstance. Such contractures should be considered as contraindications to the prescription of this orthosis or should be addressed (surgically or otherwise) prior to the application of a floor-reaction ankle-foot orthosis in these patients.