ANKLE STRENGTHENING TO IMPROVE GAIT AND FUNCTION IN CEREBRAL PALSY—A PILOT STUDY

Abstract

Purpose/Hypothesis: The purpose of this investigation was to determine if increases in ankle strength can improve gait and function in persons with cerebral palsy (CP). Despite recognizing that muscle weakness is a major impairment in CP, many of the current treatments (e.g. tendon lengthening, Botulinum toxin, orthotics) purposely weaken or result in further weakening of the muscles. Number of Subjects: Twelve subjects (3 males; 9 females, age 10 + 3 years) with spastic diplegia CP and Gross Motor Function Classification System (GMFCS) levels; I n = 5, II n = 5, III n = 2. Materials/Methods: Subjects were randomly assigned to one of four groups: 1) dorsiflexor (DF) group [n = 3], 2) plantarflexor (PF) group [n = 4], 3) dorsi-plantarflexor (DF/PF) group [n = 2], and 4) control group [n = 3] undergoing no strength training program. Subjects in the 3 training groups participated in a 12-week, 3×/week progressive resistance strength training program on an isokinetic dynamometer (concentric/eccentric @ 30 and 90o/s). Pre and post training, the subjects underwent tests for plantarflexor spasticity, end range dorsiflexion, ankle strength, GMFM66 (Gross Motor Function Measure), GMFM-wrj (walk, run, jump) and gait speed. Paired t test and correlations were used to assess changes and relationships (P < 0.05). Results: Results indicated no increase in spasticity or decrease in end range dorsiflexion. There was a significant increase in strength in the trained muscles (P = 0.007). The strength increase was greater for the plantarflexors of PF group (0.46 Nm/kg) than for the dorsiflexors of the DF group (0.20 Nm/kg). For the DF/PF group, the strength increase of the dorsiflexors was not as much as those of the DF group, whereas the strength increase of the plantarflexors was slightly greater than those of the PF group. The muscles that were not trained were unchanged. GMFM66 results showed increases in the 3 training groups and a decrease for the control group (1.0, 1.8, 2.7 and −2.7 for the DF, PF, DF/PF, Control groups, respectively). Results for the GMFM-wrj indicated larger improvements than the GMFM66. There was a significant increase in the GMFM-wrj for the training groups (P = 0.041). Further, the correlation between change in strength and change in GMFM-wrj was r = 0.84 (P = 0.001). Gait speed was increased for the PF group (8.0 cm/s) and for the DF/PF group (2.4 cm/s). The increase in the PF group was primarily due to a 6.4 cm increase in stride length. Speed was unchanged for the DF group (−1.1 cm/s) and for the control group (−1.5 cm/s). Conclusions: Results from this study seem to indicate that increases in ankle strength are possible in individuals with CP. Function was improved for all of the strength training groups. Gait speed improved with strengthening of the plantarflexors but not with isolated dorsiflexor strength training. Clinical Relevance: If the results hold true for a larger investigation, strengthening rather than weakening the plantarflexors, may improve gait and function in persons with CP. Funding: NIH- Ankle Strengthening to Improve Gait and Function in CP (R01 NS046434).