ESMAC edition:17 location:Antalya, Turkey date:11-13 September 2008
This study investigated the interrater reliability and concurrent validity of a hand-held dynamometer in children with cerebral palsy. This assessment protocol was used to evaluate strength outcome and progression over time after multilevel orthopaedic surgery (MLS) of the lower limbs.
Isometric strength can be reliably measured by a hand-held dynamometer in patients with cerebral palsy after MLS. Findings of this study indicate that early rehabilitation including strength training is recommendable.
Orthopaedic surgery aims at improving functional ability of children with CP, however it is known to initially reduce muscle strength, particularly in the presence of pre-existing weakness. Few studies have examined the progression of muscle strength following MLS in children with CP1,2. This study aims at evaluating strength outcome and progression over time in this patient group after MLS. The assessment device for strength, a hand-held dynamometer, was evaluated for reliability and validity.
PATIENTS/MATERIALS and METHODS
Inclusion criteria for both studies were: hospitalization following MLS, diagnosis of spastic cerebral palsy and a GMFCS score of < 4. For the reliability study, 28 children with CP (mean age 14y2m; range 9y6m – 18y10m) were recruited. Maximum isometric strength (M. Gastrocnemius, Mm. Vasti, M. Quadriceps, M. Hamstrings, M. Gluteus medius, M. Gluteus maximus) was evaluated by two testers using a portable hand-held dynamometer at two measurement points. To evaluate concurrent validity, muscle strength was also evaluated using the Manual Muscle Testing (MMT) of Daniels and Wothingham by the two testers. For the strength outcome study, strength measurements of 31 children (mean age 13y11m; range 5y9m – 27y5m) were performed before surgery, at the beginning of the rehabilitation program and at discharge. All children received conventional rehabilitation and a three times weekly strength-training program. Statistical analysis was carried out to assess the interrater reliability (Intraclass Correlation Coefficients) and concurrent validity of the dynamometer (Spearman rank correlation coefficients). To evaluate the progression of strength over time, Friedman tests were applied with post-hoc Wilcoxon signed rank tests.
The present study showed excellent reliability coefficients of strength measurements by use of a hand-held dynamometer in this patient group after MLS. Good to high correlation coefficients between the values of the dynamometer and those of the MMT supported the concurrent validity. Friedman tests indicated a highly significant difference in strength for all muscle groups between the three measurements (p<0.0001). Post-hoc tests showed a highly significant decrease of strength for all muscle groups after surgery (p<0.0001) and a highly significant increase of strength after the rehabilitation program for all muscle groups (p<0.0001). At discharge, the strength of M. Gastrocnemius, Mm. Vasti and M. Quadriceps even reached its preoperative level.
The results of this study indicated a decrease in muscle strength after MLS, but also the possibility to increase strength already in the early rehabilitation phase. Some muscle groups even reached preoperative levels at discharge from the hospital. The more proximal muscle groups did not reach preoperative levels and probably need a longer training period to become stronger.
 Patikas D et al. Arch Phys Med Rehabil 2006;87:1161-1169.
 Seniorou M et al. Gait Posture. 2007;26:475-481.