Determinants of gait as applied to children with cerebral palsy.

In the present study, we quantified the isolated contributions of eight determinants of gait on the vertical center of mass (CoM) displacement of both typically developing children and children with cerebral palsy (CP). The role of these determinants, on vertical excursion, has never been examined for children or children with CP. We hypothesized that the relative contributions of the determinants to vertical CoM excursion of children with CP would be the same as the age-matched controls. We found that based on the similarities in the determinants effect on gait between the controls and adults reflect that children of this age walk with a mature gait. When applied to subjects with CP the determinant analysis found similar, but slightly exaggerated effects of those of the controls. All determinants that negatively affect CoM excursion were significantly worse in the children with CP, while those determinants that decreased excursion were varied. Heel rise, single support knee flexion, and pelvic obliquity had similar effects for on both groups. Pelvic rotation resulted in more excursion reduction in the controls, while leg inclination was more beneficial in reducing the CP groups excursion. The main cause for increased vertical excursion of the CoM in the children with CP was the increased knee flexion of both legs during double support. This excessive lowering of the CoM means that extra work is done to raise the CoM over the single support leg. The situation is aggravated by the fact that the CoM was lifted higher than typical because of the heel lifting during single support. Although these determinants allow quantification of the effects of gait kinematics and provide some useful information for gait they are limited in their ability to quantify the dynamics and kinetics of gait that are important for individuals with walking disabilities.

Gross Motor Function Classification System and outcome tools for assessing ambulatory cerebral palsy: a multicenter study.

The relationships between different levels of severity of ambulatory cerebral palsy, defined by the Gross Motor Function Classification System (GMFCS), and several pediatric outcome instruments were examined. Data from the Gross Motor Function Measure (GMFM), Pediatric Orthopaedic Data Collection Instrument (PODCI), temporal-spatial gait parameters, and oxygen cost were collected from six sites. The sample size for each assessment tool ranged from 226 to 1047 participants. There were significant differences among GMFCS levels I, II, and III for many of the outcome tools assessed in this study. Strong correlations were seen between GMFCS level and each of the GMFM sections D and E scores, the PODCI measures of Transfer and Mobility, and Sports and Physical Function, Gait Velocity, and Oxygen Cost. Correlations among tools demonstrated that the GMFM sections D and E scores correlated with the largest number of other tools. Logistic regression showed GMFM section E score to be a significant predictor of GMFCS level. GMFM section E score can be used to predict GMFCS level relatively accurately (76.6%). Study data indicate that the assessed outcome tools can distinguish between children with different GMFCS levels. This study establishes justification for using the GMFCS as a classification system in clinical studies.

Posterior-only unit rod instrumentation and fusion for neuromuscular scoliosis.

STUDY DESIGN: A retrospective study to determine the efficacy of posterior-only unit rod instrumentation and fusion in a skeletally immature neuromuscular scoliosis population. OBJECTIVE: To determine whether the posterior-only approach to this population adequately addresses the concerns of correction of scoliosis and pelvic obliquity, maintenance of that correction over time, and the incidence of crankshaft phenomenon. SUMMARY OF BACKGROUND DATA: Controversy exists regarding the need for anterior release to improve curve flexibility and the need to obtain an anterior arthrodesis in those skeletally immature patients at risk for crankshafting with continued anterior growth. METHODS: From 1992 through 1997, 28 consecutive skeletally immature patients with neuromuscular scoliosis underwent posterior-only unit rod instrumentation and fusion for the treatment of progressive, symptomatic spinal deformities. Preoperative, immediate postoperative, and final follow-up radiographs were analyzed with respect to scoliosis and pelvic obliquity correction, maintenance of that correction over time, and the development of the crankshaft phenomenon as evidenced by loss of correction and/or increased rib-vertebral angle difference. The average age of the patients was 12.8 years and the average follow-up was 58 months with a minimum of 2 years. RESULTS: Twenty-six patients were available for final follow-up. The initial Cobb angle correction averaged 66%, with 75% of the pelvic obliquity corrected. These corrections were maintained over time. Before surgery 27 of 28 patients were Risser 0, 1, or 2. The triradiate cartilage was open in nine patients, and five patients were < or =10 years of age. At the final follow-up 22 of the 26 patients were Risser 5 and 4 were Risser 4. There was one patient with increased rib-vertebral angle difference over the length of follow-up, with no loss of frontal or sagittal plane alignment. CONCLUSIONS: These results indicate that even in the very young neuromuscular patient, acceptable amounts of curve correction can be achieved and maintained with posterior-only unit rod instrumentation and fusion. The biomechanical stiffness of this construct seemed to be able to prevent the crankshaft phenomenon in the majority of those patients at risk.

Deficits in eccentric versus concentric torque in children with spastic cerebral palsy.

PURPOSE: The purposes of this study were to determine whether ambulatory children with spastic cerebral palsy (CP) had abnormal isokinetic eccentric peak torque values at the knee and ankle, and to gain further insights on the influence of spasticity on voluntary force production in this population. METHODS: Twenty-four children with spastic CP (mean = 11.1+/-2.6 yr) and twenty children of comparable age with no neuromotor pathology (mean = 10.3+/-2.6 yr) participated in an isokinetic testing protocol on a Biodex dynamometer that measured eccentric and concentric peak torques of the knee extensors, knee flexors, ankle dorsiflexors, and ankle plantarflexors. Angular velocity of the eccentric trials was 30 degrees x s(-1) and of the concentric trials was 30 degrees x s(-1), 60 degrees x s(-1), and 120 degrees x s(-1). Peak torque values were normalized by body weight and compared across groups by using ANOVA procedures. Eccentric to concentric (E/C) peak torque ratios at 30 degrees x s(-1) were computed for each muscle and compared across groups. The torque values in CP were also expressed as a percent of the mean normalized value of the comparison group and compared across conditions using repeated measures ANOVA (P < 0.05). RESULTS: Children with CP demonstrated decreased eccentric and concentric peak torques for all muscle groups tested. The relative deficit in eccentric torque was less than the concentric torque and the decrement in concentric torque across speeds was greater in CP for all muscle groups except the ankle dorsiflexors. The E/C ratios for the knee extensors and flexors were also greater in CP. CONCLUSIONS: Children with CP have diminished eccentric as well as concentric peak torques at the knee and ankle. The influence of spasticity on voluntary force production can be inferred from the bias toward greater eccentric torque and the greater decrement in concentric torque across speeds in children with spastic CP.

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.

Electromechanical delay and reflex response in spastic cerebral palsy.

OBJECTIVE: Electromechanical delay (EMD) and reflex response in patients with spastic cerebral palsy (CP) were quantified and compared with those in normally developing individuals. It was hypothesized that the increased muscle stiffness associated with spasticity must make EMD shorter than the EMD of normally functioning muscles. DESIGN: Electromechanical reflex behavior was assessed in a case-control study. SETTING: Motion Analysis and Motor Performance Laboratory, University of Virginia, a tertiary clinical referral center and research facility. PARTICIPANTS: A volunteer sample of 12 children diagnosed with spastic CP and 12 age-matched, normally developing children recruited from the local community and clinical services. RESULTS: EMD in the patients with spasticity was significantly shorter than in the normally developing subjects, 40.5 msec and 54.7 msec, respectively. The spastic group also had greater reflex activity, rate of force development, and antagonistic muscle activation. Knee flexion angle did not influence EMD in either group. CONCLUSIONS: Increased biomechanical stiffness in spastic muscle results in abnormally reduced EMD. Reciprocal excitation of antagonistic cocontraction was uniquely observed in the spastic group, but did not explain the reduced EMD.

Muscle force production and functional performance in spastic cerebral palsy: relationship of cocontraction.

OBJECTIVE: To determine cocontraction's relation to strength and motor function in children with spastic cerebral palsy (CP). DESIGN: Prospective evaluation with a convenience sample of 10 subjects. SETTING: Pediatric rehabilitation center at a tertiary care hospital. PATIENTS: Ten ambulatory children with spastic CP, mean age 5 to 14yrs. MAIN OUTCOME MEASURES: A single comprehensive assessment of hamstring and quadriceps muscle strength; gait analysis while monitoring electromyographic (EMG) activity in those muscles; administration of the Gross Motor Function Measure (GMFM); heart-rate monitoring during quiet rest versus gait to compute an energy expenditure index (EEI). Cocontraction ratios and magnitudes were determined for the gait and strength testing trials using the EMG data. RESULTS: Cocontraction ratios during strength tests correlated directly with those during free gait. Cocontraction magnitude and total EMG magnitude had an inverse relationship to EEI; children with more muscle activity in the agonist and antagonist tended to be more energy efficient. Knee extensor muscle strength correlated positively with the GMFM and gait velocity. Neither cocontraction ratio nor magnitude during gait was related to strength. CONCLUSIONS: Children with CP used a similar muscle activation strategy across two different motor tasks. Strength and cocontraction were uniquely related to different aspects of motor function. Further research is needed to quantify more precisely cocontraction and force to EMG relations in this population.

Joint angular velocity in spastic gait and the influence of muscle-tendon lengthening.

BACKGROUND: Joint angular velocity (the rate of flexion and extension of a joint) is related to the dynamics of muscle activation and force generation during walking. Therefore, the goal of this research was to examine the joint angular velocity in normal and spastic gait and changes resulting from muscle-tendon lengthening (recession and tenotomy) in patients who have spastic cerebral palsy. METHODS: The gait patterns of forty patients who had been diagnosed with spastic cerebral palsy (mean age, 8.3 years; range, 3.7 to 14.8 years) and of seventy-three age-matched, normally developing subjects were evaluated with three-dimensional motion analysis and electromyography. The patients who had cerebral palsy were evaluated before muscle-tendon lengthening and nine months after treatment. RESULTS: The gait patterns of the patients who had cerebral palsy were characterized by increased flexion of the knee in the stance phase, premature plantar flexion of the ankle, and reduced joint angular velocities compared with the patterns of the normally developing subjects. Even though muscle-tendon lengthening altered sagittal joint angles in gait, the joint angular velocities were generally unchanged at the hip and knee. Only the ankle demonstrated modified angular velocities, including reduced dorsiflexion velocity at foot-strike and improved dorsiflexion velocity through mid-stance, after treatment. Electromyographic changes included reduced amplitude of the gastrocnemius-soleus during the loading phase and decreased knee coactivity (the ratio of quadriceps and hamstring activation) at toe-off. Principal component analyses showed that, compared with joint-angle data, joint angular velocity was better able to discriminate between the gait patterns of the normal and cerebral palsy groups. CONCLUSIONS: This study showed that muscle-tendon lengthening corrects biomechanical alignment as reflected by changes in sagittal joint angles. However, joint angular velocity and electromyographic data suggest that the underlying neural input remains largely unchanged at the hip and knee. Conversely, electromyographic changes and changes in velocity in the ankle indicate that the activation pattern of the gastrocnemius-soleus complex in response to stretch was altered by recession of the complex.

Asymmetric hip deformity and subluxation in cerebral palsy: an analysis of surgical treatment.

Thirty-seven cerebral palsy patients were followed with measurements of the migration index (MI), infrapelvic obliquity, and suprapelvic obliquity over a mean period of 73 months to evaluate the development of the windblown deformity. The infrapelvic asymmetry was apparent before the suprapelvic obliquity; however, 65% eventually had both. The final pattern of infrapelvic obliquity and the most subluxed hip could not be predicted from initial radiographs or from the pattern of scoliosis. Hip subluxation strongly correlated with the degree of femoral adduction and weakly with the magnitude of suprapelvic obliquity. The suprapelvic obliquity and scoliosis increased over time and influenced the final windblown appearance. Soft-tissue surgeries did not have a significant effect on the final MI. Severe abduction deformities generally followed ipsilateral adductor releases. Finally, despite improvement in the MI of the initially more subluxed hip, 33% of patients still had one hip with a MI >50%.

Interrelationships of strength and gait before and after hamstrings lengthening.

Muscle-tendon lengthenings are an essential part of the orthopaedic management of static and dynamic joint contractures associated with cerebral palsy. Although these procedures typically have a positive biomechanical effect on joint alignment, the potential negative effects of alterations in tendon length on muscle strength and gait function have not been well documented in these patients, in whom muscle weakness is a prevalent clinical symptom. The purpose of this study was to examine the change in strength values of the hamstring and quadriceps muscle groups during a 9-month postoperative period in patients who had undergone hamstring tendon lengthenings, in comparison to an operative "no hamstring surgery" control group, and to relate baseline strength and postoperative changes to gait function in these patients. Results for the "hamstring surgery" group indicated that although hamstring strength declined initially, the strength increased with time and was similar to preoperative values by 9 months. Quadriceps strength measured at 30 degrees of knee flexion increased significantly during the recovery period as a direct result of improvements in knee extension. Although hamstring surgery produced an immediate effect on passive motion and knee-joint alignment, functional improvement, as evidenced by increased stride length, was not evident until strength values approximated or exceeded preoperative values.

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.

Quantification of cocontraction in spastic cerebral palsy.

Antagonist cocontraction was hypothesized to limit net moment production in children with spastic diplegic cerebral palsy (CP). A second hypothesis was that concontraction would vary with joint angle. To test these hypotheses, surface EMG activity and moment data from the quadriceps and hamstrings muscle groups were obtained from children with CP and compared with normally developing children during isometric flexion and extension exertions. A biomechanical model was developed to predict individual moments produced by the agonist and antagonist muscle groups. Concontraction was defined as the percentage of the net moment that was negated by the antagonist moment. The model performed well in predicting the measured moment as illustrated by high R2 correlation coefficients and low prediction errors. The mean maximum moment produced was greater in normally developing children than children with CP in both flexion and extension. Antagonist cocontraction during extension was greater in children with CP (12.2 +/- 14.4%) than in normally developing children (4.9 +/- 3.8%), implying that antagonist cocontraction is one explanation for the observed extension weakness in children with CP. However, during flexion, cocontraction was not significantly different between the two groups. Cocontraction differed significantly with joint angle in both groups during flexion and in the normally developing children during extension. Although quantifying coactivation based on EMG activity alone produced similar results, it underestimated the effect of the antagonist. The quantification of cocontraction has potential applications for characterizing spastic muscle dysfunction and thereby improving clinical outcomes in children with CP.

Familial synspondylism: progressive scoliosis and multiple hernias in a kinship.

A new genetic syndrome is reported of congenital lordoscoliosis due to lumbar segmentation defects and incomplete formation of lumbar vertebrae. The defect arose as a spontaneous mutation and was transmitted in an autosomal dominant fashion. The kindred included a mother and her three offspring. These affected individuals had several dysmorphic features including cavus feet and micrognathia. In addition the syndrome was associated with multiple hernias including inguinal, ventral, and diaphragmatic. These associated problems led to the early death of the first child at age 7 months. The lumbar scoliosis was already evident by that time. The progressive nature of the scoliosis was documented, especially in one child who was lost to follow-up and who was initially seen with a severe spinal deformity. Surgical management was required in members of the kindred, but because of differences in age and severity at the time of surgery, the techniques varied.

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.

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.

Comparison of functional outcomes from orthopedic and neurosurgical interventions in spastic diplegia.

Selective dorsal rhizotomy (SDR) and orthopedic surgery, in the form of muscle-tendon (MT) lengthening surgery are commonly performed in ambulatory children with spastic diplegia to improve their level of motor function. This investigation is a post hoc comparison of the functional effects from each of these surgical options in 30 patients with spastic diplegia who underwent one of these interventions as their initial surgical procedure. Sixteen children underwent SDR and 14 underwent MT surgery in two separate prospective clinical trials. The same functional outcome measures preoperatively and approximately 1 year postoperatively were used in both studies including temporospatial parameters from three-dimensional gait analysis, the total score, and score on each of the five dimensions of the Gross Motor Function Measure (GMFM). Comparisons indicate that patients who underwent SDR had significant improvements in GMFM Dimensions 2, 4, and 5 as well as in total score, although 63% of those studied had a 10% or more reduction in gait velocity. Gait was more predictably improved in the MT group, with only 21% demonstrating reductions in velocity. Conversely, the change in GMFM scores in the MT group was not as pervasive and skewed toward higher skills with only GMFM Dimension 5 and total score improved significantly. Several important hypotheses are derived from these comparisons. Multicenter clinical trials are needed to define more clearly the indications for and to assess more comprehensively the outcomes from each intervention.

Orthotic management of gait in spastic diplegia.

Orthoses are the primary conservative treatment option for control of dynamic equinus in spastic cerebral palsy. Our purpose was to compare the effects of a fixed ankle-foot orthosis (AFO), a supramalleolar orthosis (SMO), and a no-brace condition, but including shoes. Gait analyses were performed on 11 children with spastic diplegia, using a system with four cameras and two concealed force plates. Ensemble averages of time-distance, kinematic, and kinetic parameters were obtained for each condition, and a repeated measures analysis of variance was performed (P < 0.05). Among the important findings were as follows: (1) AFOs significantly reduced ankle excursion, increased dorsiflexion angle at foot strike, increased plantar flexion moment in push-off, decreased ankle power absorbed during loading response, and decreased ankle power generated in push-off; (2) SMOs did not restrict ankle range of motion or significantly alter the power and moment values at the ankle joint. Although neither brace changed stride length and walking speed, AFOs did offer some biomechanical benefits to the child with spastic diplegia, whereas SMOs appeared to have very little measurable effect.

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.

Fuzzy clustering of children with cerebral palsy based on temporal-distance gait parameters.

Temporal-distance parameters for 88 children with the spastic diplegia form of cerebral palsy (CP) are grouped using the fuzzy clustering paradigm. The two features chosen for clustering are stride length and cadence which are normalized for age and leg length using a model based on a population of 68 neurologically intact children. Using information provided by the neurologically intact population and cluster validity techniques, five clusters for the children with cerebral palsy are identified. The five cluster centers represent distinct walking strategies adopted by children with cerebral palsy. Utilizing just four easily obtained parameters--stride length, cadence, leg length and age--and a small number of simple equations, it is possible to classify any child with spastic diplegia and to generate an individual's membership values for each of the five clusters. The clinical utility of the fuzzy clustering approach is demonstrated with pre- and post-operative test data for subjects with cerebral palsy (one neurosurgical and one orthopaedic) where changes in membership of the five clusters provide an objective technique for measuring improvement. This approach can be adopted to study other clinical entities where different cluster centers would be established using the algorithm provided here.