Mark F. Abel

Functional outcomes of strength training in spastic cerebral palsy

OBJECTIVE To determine clinical effectiveness of strength training in children with spastic cerebral palsy. DESIGN Prospective before and after trial in which subjects participated in a 6-week strength training program. All received before and after isometric strength evaluation of eight muscle groups in both lower extremities with a hand-held dynamometer, 3-D gait analysis at free and fast speeds, administration of the Gross Motor Function Measure (GMFM), and assessment of energy expenditure during gait. SETTING Pediatric rehabilitation center at a tertiary care hospital. PATIENTS Eleven children met inclusion criteria for participation. Six had spastic diplegia, were limited community ambulators, and demonstrated less than 50% of normal muscle strength. Five had spastic hemiplegia and demonstrated a 20% strength asymmetry in at least two muscles across extremities. RESULTS Each group had significant strength gains in the muscles targeted. The entire cohort had higher gait velocity primarily as a result of increased cadence, with greater capacity to walk faster. GMFM Dimension 5 also improved, with no change in energy expenditure. Asymmetry in strength improved in hemiplegia, with no change in asymmetry in support times or joint motion across extremities. CONCLUSIONS This study reinforced the relationship of strength to motor function in cerebral palsy and further demonstrated the effectiveness of strengthening in this population.

The evolution of gait in childhood and adolescent cerebral palsy.

A longitudinal study over a mean of 32 months was conducted on 18 subjects with spastic diplegia, ranging in age from 4 to 14 years. Three-dimensional gait analyses were performed to compare the temporal and kinematic data across the two time intervals. The comparison revealed a deterioration of gait stability evidenced by increases in double support and decreases in single support with time and growth (p < 0.05). Kinematic analysis revealed a loss of excursion about the knee, ankle, and pelvis (p < 0.05). Additionally, passive range-of-motion analysis revealed a decrease in the popliteal angle over time (p < 0.05). In conclusion, this longitudinal investigation revealed that, in contrast to the gait of children with intact motor function, ambulatory ability tends to worsen over time in spastic cerebral palsy. Insight into the natural progression of gait function in cerebral palsy is essential when evaluating the change in motor status over time or the effects of an intervention in this population.

What does the Ashworth scale really measure and are instrumented measures more valid and precise

This study aimed to explore the limitations of the Ashworth scale for measuring spasticity. An isokinetic dynamometer to quantify resistance to passive stretch and surface EMG was used to verify if a stretch response occurred and, if so, at what joint angle. The authors sought to determine which components of passive resistance (magnitude, rate of change, onset angle of stretch, or velocity dependence) were most related to Ashworth scores and which were related to motor function in cerebral palsy (CP). Twenty-two individuals with spastic CP (11 males, 11 females; mean age 11.9 years, SD 4.3) and a comparison group of nine children without CP (four males, five females; mean age 11.3 years, SD 2.5) participated in the study. The group with CP included those with a diagnosis of spastic diplegia, hemiplegia, or quadriplegia, distributed across Gross Motor Functional Classification Levels. Procedures included: (1) clinical assessment at the knee joint, (2) functional assessments, and (3) isokinetic assessment of passive resistance torque in hamstrings and quadriceps at three velocities. EMG data were recorded simultaneously to identify stretch responses. Detecting stretch responses using the Ashworth scale compared with instrumented measures showed near complete agreement at extremes of the scale, with marked inconsistencies in mid-range values. Ashworth scores were correlated with instrumented measures, particularly for the quadriceps, with higher correlations to the rate of change in resistance (stiffness) and onset angle of stretch than to peak resistance torque. Those with greater resistance tended to have poorer function with isokinetic relations typically stronger.

Spasticity versus strength in cerebral palsy: relationships among involuntary resistance, voluntary torque, and motor function.

Despite the lack of consensus of the role of spasticity in the observed motor disability in cerebral palsy (CP), alleviation of spasticity remains a primary focus in the clinical management of these patients. The purposes of this study were to: (1) quantify voluntary torque and passive resistance across speeds in the hamstrings and quadriceps muscle groups with respect to the presence of stretch responses and/or passive muscle stiffness in patients with CP compared to age‐related children without disability, and (2) relate these parameters to each other and to functional performance, as measured by the Gross Motor Function Measure (GMFM), in CP. Included were 23 subjects with CP, sub‐grouped by the presence or absence of stretch responses as determined by electromyography, and 9 subjects without CP. Results indicated that peak torque was considerably greater in the comparison group than for each of the CP groups and resistance was greater in the CP group with spasticity compared to the nonspastic CP group in both muscles at all speeds. Stiffness differed between the spastic CP group and the comparison group only for the quadriceps at the fastest speed. Higher passive resistance torque and stiffness were correlated with decreased voluntary torque, particularly for the antagonists, and with lower GMFM scores. In conclusion, strength and motor function are related to the magnitude of resistance torque and stiffness in CP, although the small amount of variance explained reinforces the multidimensional nature of this disorder, and the challenges inherent in managing it.

RELATION OF GAIT ANALYSIS TO GROSS MOTOR FUNCTION IN CEREBRAL PALSY

The Gross Motor Function Measure (GMFM) and computerized gait analysis are commonly used to assess patients with cerebral palsy (CP). The authors investigated correlations between the GMFM and gait parameters in 32 children aged 3 to 18 (mean 8.9) years with spastic CP. Of the gait parameters, cadence and normalized velocity correlated most strongly with the GMFM score, and hip and knee excursion and percentage single support also correlated directly with the GMFM. In a stepwise multiple regression, cadence alone was a significant predictor of GMFM score. Time and distance parameters, hip and knee excursion in the sagittal plane and GMFM values all moved consistently further from pediatric norms as functional severity increased. The study confirms that gait is representative of general motor status in CP and that the GMFM and gait analysis are complementary measures in the functional assessment of these children.

Outcome tools used for ambulatory children with cerebral palsy: responsiveness and minimum clinically important differences

This prospective longitudinal multicenter study of ambulatory children with cerebral palsy (CP) examined changes in outcome tool score over time, tool responsiveness, and used a systematic method for defining minimum clinically important differences (MCIDs). Three hundred and eighty‐one participants with CP (Gross Motor Function Classification System [GMFCS] Levels I–III; age range 4–18y, mean age 11y [SD 4y 4mo]; 265 diplegia, 116 hemiplegia; 230 males, 151 females). At baseline and follow‐up at least 1 year later, Functional Assessment Questionnaire, Gross Motor Function Measure, Pediatric Quality of Life Inventory, Pediatric Outcomes Data Collection Instrument, Pediatric Functional Independence Measure, temporal–spatial gait parameters, and oxygen cost were collected. Adjusted standardized response means determined tool responsiveness for nonsurgical (n=292) and surgical (n=87) groups at GMFCS Levels I to III. Most scores reaching medium or large effect sizes were for GMFCS Level III. Nonsurgical group change scores were used to calculate MCID thresholds for ambulatory children with CP. These values were verified by examining participants who changed GMFCS levels. Tools measuring function were responsive when a change large enough to cause a change in GMFCS level occurred. MCID thresholds assess change in study populations over time, and serve as the basis for designing prospective intervention studies.

Gait assessment of fixed ankle-foot orthoses in children with spastic diplegia

OBJECTIVE To evaluate the effectiveness of ankle-foot orthoses (AFOs) in spastic diplegic cerebral palsy patients for whom orthoses were indicated to control equinus or pes planovalgus deformities. DESIGN A retrospective, cross-sectional assessment was performed on diplegic subjects who had suitable barefoot and AFO gait trials on the same day. PATIENTS Thirty-five subjects with a mean age of 8.7 yrs were included. Eighteen wore braces to control equinus and 17 to control pes planovalgus and crouch. OUTCOME MEASURES Gait data assessed in all subjects included temporal-distance factors and sagittal kinematics. Force plate data to determine joint moments and powers were obtained in 20. Repeated measures analysis of variance was used to compare across conditions and indications. RESULTS The cohort demonstrated increased velocity (10 cm/sec; p < .001), stride length (10 cm; p < .001), and percent single-limb support (1.8%; p < .002) using AFOs compared with barefoot gait. In braces, ankle excursion was reduced (p < .0001), while pelvic, hip, and knee excursions were increased to account for the temporal changes (p < .009). Effects were similar in both indication groups. In neither indication group did the AFO significantly alter knee position in stance. Kinetic analysis showed a reduction of abnormal power burst (p < .05) in early stance and an increase in late stance ankle moment (p < .05) with AFOs. Differences in gait characteristics and bracing effects are shown for both indication groups. CONCLUSION Compared with barefoot gait, AFOs enhanced gait function in diplegic subjects. Benefits resulted from elimination of premature plantar flexion and improved progression of foot contact during stance. Effects on proximal joint alignment were not significant.

Muscle-tendon surgery in diplegic cerebral palsy: functional and mechanical changes.

A prospective assessment of muscle-tendon (M-T) surgery was conducted on 30 patients with spastic diplegia. Muscle-tendon surgery consisted of recessions or releases to improve gait function by correcting restricted joint motion and joint malalignment. Functional-outcome measures included the Gross Motor Function Measure (GMFM) and temporal gait factors. Kinematic gait data were evaluated to determine the mechanical effects. The mean age at surgery was 8.7 years (4-20 years), and 3.5 muscle tendon units per extremity were recessed or released at surgery. The primary kinematic change for the hip and the knee was a shift in the sagittal joint position with minimal effects on overall excursion. Changes in ankle-joint dynamics after gastrocsoleus recessions included a reduction in plantarflexion and a shift in the timing of maximal dorsiflexion to later in stance. Improvements in walking velocity and stride length were evident by 6 month after surgery. Functional changes from M-T surgery included a 25% increase in velocity and an 18% increase in stride length over preoperative values seen at 9 months after surgery. Improvements in these parameters were maintained at 2 years after surgery. The GMFM total score showed minimal change after surgery with improvements occurring primarily in the standing dimension and the walking, running, and jumping dimensions.

Strategies for Increasing Walking Speed in Diplegic Cerebral Palsy

The study was designed to determine the strategies used by diplegic subjects to change walking speed. Two groups, limited community ambulators and community ambulators, were compared with controls to determine if ability to increase speed would decrease as a function of motor impairment. Compared with matched controls, diplegic subjects were slower and relied more on cadence to increase speed. The ability to change velocity and stride length was significantly less in the diplegic groups than in controls and accounted for the wider difference in their fast walking velocity. Velocity and stride length decreased, whereas stance time increased as a function of motor involvement. In the limited community ambulators, pelvic excursion was increased, whereas hip and knee excursion was reduced. By assessing fast speed, differences between controls and diplegic groups became more apparent.

Evaluation of CT scans and 3-D reformatted images for quantitative assessment of the hip.

Hip measurements using three-dimensional (3-D) images and computed tomography (CT) scans were evaluated. The 3-D measurements proved more accurate than CT measurements of femoral and acetabular anteversion. Additionally, accurate 3-D measurements (> 99%) of the femoral neck-shaft angle were provided. Acetabular anteversion determinations by CT scans were systematically decreased as pelvic flexion increased, whereas accuracy was > 96% with 3-D images. The 3-D software allows image rotation in all three reference planes, which minimizes positional errors. A case study is provided to exemplify the shortcomings of conventional imaging techniques and the utility of the quantitative 3-D protocol.