RESNA 28th Annual Conference - Atlanta, Georgia
Kelly M. Baker, MS1, Lucy Lu 4, Kathy Reiners3, Sahar Hassani, MS3, Jeffrey D. Ackman, MD3, Jeffrey P. Schwab, MD2 , Gerald F. Harris, PhD, PE1,2,3
1Orthopaedic and Rehabilitation Engineering Center (OREC), Milwaukee, WI
2Department of Orthopaedic Surgery, Medical College of Wisconsin, Milwaukee, WI
3Motion Analysis Laboratory, Shriners Hospital for Children, Chicago, IL
4Department of Biostatistics, Medical College of Wisconsin, Milwaukee, WI
Anterior walkers are a rehabilitative aid prescribed to children with cerebral palsy. These assistive devices are placed in front of the patient and repeatedly advanced during the gait cycle. Analysis of the kinematics of patients using anterior walkers may lead to improved rehabilitation. The purpose of this study is to characterize upper extremity (UE) motion in 20 children with spastic diplegic cerebral palsy (CP) who use anterior walkers for ambulation. Results indicate that such patients exhibit an increased heart rate and decreased walking speed with anterior walker usage. The Gross Motor Function Measure results correspond to those reported by other researchers. The unique morphology of the shoulder, elbow, and wrist joint kinematics is described.
Cerebral palsy; kinematics; rehabilitation; upper extremity; walker
Cerebral palsy (CP) is a movement disorder produced by an insult to the brain (1). It has symptoms including postural instability, muscle weakness, and spasticity. The Centers for Disease Control and Prevention (CDC) estimate that 2.8 per 1,000 children in the United States develop CP each year (2). The lower extremities are frequently affected, with walkers commonly prescribed to help overcome ambulatory difficulties. The walker allows the upper extremities to become more involved in the movement process. Currently, it is difficult to prescribe a walker for a patient with cerebral palsy because each patient’s condition is variable and it is not known or understood how a walker affects a patient biomechanically. Analysis of the kinematics of patients using anterior walkers may lead to improved rehabilitation efforts.
As a precursor to this study, our group developed an upper extremity (UE) motion analysis system (3). This study, utilizing that system, reports quantitative measures of UE kinematics in 20 children with CP who use anterior walkers for ambulation. By eventually comparing these results to our previous analysis of posterior walker results, we hope to develop a more universal method for prescribing walkers to children with CP (4).
To date, there is no quantitative characterization of UE kinematics in subjects using anterior walkers. This study reports quantitative measures of UE kinematics in 20 children with cerebral palsy, who routinely utilize an anterior walker for ambulation.
The study takes place at two institutions (Shriners Hospital for Children, Chicago, and the Medical College of Wisconsin, Milwaukee). Testing included use of a Vicon motion analysis system and an internally developed UE kinematic model (3).
Patient visits included an initial screening visit and a testing visit. The visits have a one month separation period to allow patients to become acclimated to the anterior walker if they do not already use one. Following informed consent patients undergo gait analysis and physical examination, which involves a heart rate monitor test, and Gross Motor Function Measure (GMFM). An acceptable gait cycle is defined by foot strike to ipsilateral foot strike (5) with no marker dropout.
Twenty patients (aged: 12.6 ± 3.1 years) have been tested. To characterize motion, the method of fitting a Fourier series to the kinematic data was used (6). By use of the least squares method, we fit our data to the linear model:
where Yij = the data for the ith % of a cycle and the jth trial, f = max no. of terms for the model set by R2 analysis, aO, al , bl= constants, and error has a mean of zero.
From this model, predicted values at each percentage of the gait cycle were determined for each patient.
Heart Rate Monitor: Heart rate monitor results indicate that the average resting heart rate is 92.7 beats/min and the average walking heart rate is 137.7 beats/min. The average walking speed is 19.1 meters/min, with an average energy expenditure index value 4.2 beats/meter.
|Resting Heart Rate||beats/min||92.7||10.7|
|Walking Heart Rate||beats/min||137.7||18.0|
|Energy Expenditure Index*||beats/m||4.2||4.3|
GMFM: The GMFM results indicate that the average Standing Assessment Score is 75.5 ± 21.3% and the average Walking, Running, and Jumping Assessment Score is 51.2 ± 15.8%.
|Standing Assessment (D) (%)||75.5||21.3|
|Walking, Runnin, Jumping Assessment (E) (%)||51.2||15.8|
Shoulder : Joint kinematic and statistical model results indicate that during walker usage, both the right and left shoulders are in extension. The shoulder angle averages between 20.5-24.5º on the right side with a 95% confidence interval (CI) ranging between 9.1-35.2º. On the left side, the shoulder angle is between 17.7-23.0º with a 95% CI ranging between 7.5-32.5º.
Elbow :Both the right and left elbows for an anterior walker user are in flexion.The right elbow angle averages between 81.5-93.2º with a 95% CI ranging between 71.9-102.4º.The left elbow angle averages between 100.6-109.6º with a 95% CI ranging between 94.3-116.0º.
Wrist :Right and left wrists are in extension. The wrist angle averages between 17.3-27.6º on the right side with a 95% CI ranging between 7.4-37.7º. On the left side, the wrist angle averages between 16.1-24.5º with a 95% CI ranging between 6.9-34.1º. The sagittal plane data (mean ± 95%CI) is shown in Fig. 1.
The American Heart Association cites normal resting heart rate for an average 12 year old as 60-80 beats/min and the target heart rate (while exercising) between 104 and 156 beats/min (7,8). The normal walking speed for a child between 7 and 13 years old is 68.4 m/min (8). Our patients have a higher resting heart rate and a much lower walking speed. The GMFM showed results that were similar to those found by other researchers (9,10). Our D score finding was higher than that reported by Damiano and Abel (65.5±28.2%) and McCarthy et al (50.5±40.1), but it was still within their standard deviations. Our E score result was very close to Damiano and Abel (52.5±33.6%) and within a standard deviation of McCarthy et al (44.5±37.1%) (9,10).
Shoulder motion exhibits six peaks (P 1-P 6) during each gait cycle (GC). Greatest extension is seen at 11, 33, and 52% of the GC during loading/mid stance, terminal stance, and pre-swing on the right side, and at 11, 48, and 96% of the GC during loading/mid stance, terminal stance, and terminal swing on the left side. Least extension is seen at 23, 38, and 85% of the GC during mid stance, terminal stance, and mid swing on the right side, and at 0, 36, and 71% of the GC during initial contact, terminal stance, and initial swing on the left side. Elbow and wrist motion exhibits two peaks (P 1, P 2). Patients have greatest elbow flexion at 77% of the GC during mid swing on both right and left sides and least elbow flexion at 39 and 38% of the GC during terminal stance on the right and left sides, respectively. Patients have the greatest wrist extension at 34 and 36% of the GC during terminal stance on the right and left sides, respectively, and the least wrist extension at 70 and 74% during initial swing on the right and left sides, respectively.
This project is supported by NIDRR grant H133G010069.
Kelly M. Baker
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