Short-Term Effect of Botulinum Toxin A Injection on Spastic Equinovarus Foot in Cerebral Palsy Patients: A Study Using the Foot Pressure Measurement System

OBJECTIVE To evaluate the therapeutic effect of botulinum toxin A (BTX-A) injection on spastic gastrocnemius (GCM) and tibialis posterior muscles (TPo) by using the foot pressure measurement system (FPMS). METHODS Eighteen ambulatory CP patients were recruited in this study. BTX-A was injected into the GCM at a dose of 6-12 units/kg and TPo at a dose of 4-9 units/kg according to the severity of equinus and varus deformity. Foot contact pattern, pressure time integral (PTI), coronal index using the FPMS and Modified Ashworth Scale (MAS), and visual inspection of gait pattern were used for evaluation of the therapeutic effect of BTX-A injection. Clinical and FPMS data were statistically analyzed according to the muscle group. RESULTS A significant decrease in the MAS score of the GCM and TPo was observed, and spastic equinovarus pattern during gait showed improvement after injection. The GCM+TPo injection group showed a significant decrease in forefoot, lateral forefoot pad, and lateral column PTI, and a significant increase in hindfoot PTI and coronal index. In the GCM only injection group, forefoot PTI and lateral column PTI were significantly decreased and hindfoot PTI was significantly increased. The TPo only injection group showed a significant decrease in lateral column PTI and a significant increase in the coronal index. Change in PTI in the hindfoot showed a significant correlation with the change in MAS score of the GCM. Change in PTI of the lateral column and coronal index showed a significant correlation with the change in MAS score of the TPo. CONCLUSION The FPMS demonstrated the quantitative therapeutic effect of BTX-A on abnormal pressure distribution in equinovarus foot in detail. The FPMS can be a useful additional tool for evaluation of the effect of BTX-A injection.