Skip Navigation LinksHome > Spring 2009 - Volume 21 - Issue 1 > Contribution of Stepping While Standing to Function and Seco...
Pediatric Physical Therapy:
doi: 10.1097/PEP.0b013e31818f57f2
Research Report

Contribution of Stepping While Standing to Function and Secondary Conditions Among Children with Cerebral Palsy

Eisenberg, Sharon PT, MSc; Zuk, Luba PT, PhD; Carmeli, Eli PT, PhD; Katz-Leurer, Michal PT, PhD

Free Access
Article Outline
Collapse Box

Author Information

Physical Therapy Department, The Stanley Steyer School of Health Professions, Sackler Faculty of Medicine, Tel-Aviv University, Tel Aviv, Israel

Address correspondence to: Michal Katz-Leurer, PhD, Sackler Faculty of Medicine, Physical Therapy Department, School of Health Professions, Tel-Aviv University, Tel-Aviv 69978, Israel. E-mail: michalkz@post.tau.ac.il

Collapse Box

Abstract

Purpose: To explore the feasibility and efficacy of stepping while standing and its effect on function and prevalence of secondary conditions among children with severe cerebral palsy.

Methods: Of 22 children with severe cerebral palsy, 11 underwent treatment using a Hart Walker (HW) device, and the other 11 underwent a passive standing program. Constipation prevalence and adverse events were recorded. Bone quantitative ultrasound was performed for the tibia. The Pediatric Evaluation of Disability Inventory was used to assess activities of daily life.

Results: Children exposed to the HW improved bowel function, but no added quantitative benefit to bone was observed when compared with passive standing. Children using the HW were able to take steps independently in the device, but did not reach a functional walking level.

Conclusions: Providing a child who is nonambulatory the opportunity to walk may be important both for participation in activities of daily living and social roles and for preventing secondary conditions.

Back to Top | Article Outline

INTRODUCTION

Cerebral palsy (CP), a static, nonprogressive disorder, is caused by brain injury during the prenatal, perinatal, or postnatal period and is the major developmental disability affecting function in children. It is characterized by the inability to control motor function, and affects the child’s ability to explore, speak, learn, and become independent.1

Individuals with CP are at a higher risk for secondary conditions because multiple body systems are affected during the developmental years. Secondary conditions include impairments, functional limitations, or disabilities resulting from the primary condition or pathology.2 Brain damage is the primary insult in CP and affects developing motor control and musculoskeletal growth. Researchers have identified numerous secondary conditions affecting people with CP including osteoporosis, fractures, contractures, degenerative joint disease, dental problems, constipation, cardiovascular disorders, and social isolation.2 Studies have shown that children and adolescents with CP are at a higher risk for secondary conditions when compared with their less severely affected peers.3,4

The use of standers in the treatment of children who are unable to stand or walk by themselves is extensive. Standers permit lower-extremity weight-bearing, which increases muscle strength and postural control, improves visual, upper limb, and oral motor skills, and increases social communication. At the same time, weight-bearing (WB) activities may prevent secondary conditions by maintaining or even improving the physiological status of the pulmonary, renal, and gastrointestinal systems, bone mineral density, contractures and deformities.5,6,7 Stuberg demonstrated that an 8-week standing program for children with CP, performed for 60 minutes 4 to 5 times a week produced significant increases in bone mineral density (BMD) in the patella, tibial plateau, and supracondylar femur.8 Animal research models have demonstrated that even greater increases in BMD may occur with intermittent weight-bearing as opposed to static WB exercise.8–10 Wilmshurst et al11 showed that BMD was positively associated with the degree of immobility and non-WB status of a group of children with CP, and Henderson et al12 found that BMD of children with spastic CP correlated positively with ambulatory status.

Children with CP have the option for independent ambulatory mobility with a choice of different walkers. Some, like the Kaye Walker, require that children use their hands to maintain themselves in the upright position. Others, like the Can-Dan Walking Support™, and Arrow Walker™, provide a hands-free position and support the child with a seat or harness. One of the newer hands-free walkers, the David Hart Walker (HW) Orthosis has a customized brace section for the pelvis/lower limbs and is attached to a wheeled frame with a spring-loaded weight-bearing/relieving device, which provides both weight-bearing support and leg alignment while allowing upper extremity freedom. This device allows even a child with severe disabilities to experience independent walking.

Between 2004 and 2006, 11 children with severe CP who had never walked before began using the HW device. The aims of the present study were to (1) explore the feasibility of using the HW device with children who have CP and are nonambulatory, (2) compare functional skill development between children in a passive standing program and children using the HW device, and (3) compare prevalence and severity of decreased bone density and constipation between groups in the HW program and those in a passive standing program.

Back to Top | Article Outline

METHODS

The study was designed as a 6-month follow-up of 22 children. Eleven children in addition to their physical therapy sessions began the trial with the HW device whereas the other 11 children attending a special education school continued with a passive standing program in their physical therapy treatment.

Back to Top | Article Outline
Participants

Eleven children with severe CP (6 boys and 5 girls) used the HW device. All subjects were new patients of the Child Development Center at the “Ziv” hospital in the north of Israel and were selected according to the following criteria: (1) aged between 3.5 and 10 years at the first visit to the clinic, (2) diagnosis of CP spastic quadriplegic and categorized by the gross motor function classification system (GMFCS) as level 4 or 5,13 (3) inability to stand and walk with a traditional walker/rollator because of insufficient upper extremity control, (4) attempts steps when in a supported standing position, and (5) flexion contracture of the hips and the knees of less than 30°.

Eleven children with CP matched for age and sex served as controls. They attended a special education school in the hospital area, and all met the same inclusion criteria. They all underwent a program in a standing frame (SF) in the school as part of the physical therapy session.

The study was approved by the hospital ethics committee and informed consent was obtained from both parents before the initiation of the study. The descriptive characteristics of both groups are presented in Table 1.

Table 1
Table 1
Image Tools
Back to Top | Article Outline
Measurement Tools
Feasibility of the Program.

All children were followed up for 6 months, and at entry into the study each parent and the treating physical therapist were provided with a diary and requested to keep a daily record of the standing and stepping (HW) or the standing frame (SF) sessions during the last week of the each month. The diary included information on use of the equipment (HW or SF) and the duration of use (in minutes) of each session. Parents and the treating physical therapist were asked to record in a second diary any adverse event (falls, fractures, dizziness, etc.) during the experience with the equipment.

Back to Top | Article Outline
Parental Satisfaction and Experience with HW.

At the end of the follow-up period, a satisfaction questionnaire was completed by the parents. This questionnaire was designed by the investigative team and used a 5-level ordinal scale to rate satisfaction of the HWs overall utility. Parents were asked to identify any difficulties or adverse effects associated with the use of the device and were also asked, using a 3-level ordinal scale, about the child’s cooperation in using the HW device. For example: which is the most appropriate statement to describe the child’s reaction to the HW? (a) The child asks to use the walker. (b) The child agrees to use the walker when asked. (c) The child does not agree to use the walker when asked.

Back to Top | Article Outline
Effectiveness of the Program
Functional Performance.
Back to Top | Article Outline
Evaluation of activities of daily life.

The Pediatric Evaluation of Disability Inventory (PEDI) was used to assess activities of daily life.14 The PEDI is a structured parental interview that assesses functional skills (capability) and caregiver assistance. It covers the domains of self-care (73 items), mobility (59 items), and social functioning (65 items). We used the scaled scores that estimate skills in older children whose functional abilities lag behind those expected of 7.5-year-old children who are healthy.14 The PEDI is sensitive to changes over time. The internal consistency for PEDI scales has scores ranging from 0.95 to 0.99 and a mean standard error of measurement of 0.09.14,15 The smallest change in a PEDI score considered to be associated with a minimal but clinically important difference in skill ranges from 6 to 15 points (mean, 11.5; SD, 2.8) for all PEDI scales.16

Back to Top | Article Outline
Mobility Parameters Recorded Among the HW Group.
Back to Top | Article Outline
Walking speed.

The mean walking speed was measured by manually timing the duration of an unconstrained 5-m walk. Measurements were made within the midrange of a 7-m long walkway.17

Back to Top | Article Outline
Walking endurance.

A 2-minute walking test was carried out within a 7-m circular walkway. The distance covered in the 2-minute time interval was used as an estimate of cardiopulmonary and musculoskeletal endurance.18

Back to Top | Article Outline
Secondary Conditions.
Back to Top | Article Outline
Bowel function.

A diary which the parent and/or the physical therapist maintained throughout the follow-up period was used to assess bowel function. Constipation was defined as 2 bowel movements per week or 2 of the following on more than 1 of 4 occasions: straining, hard stools, and feeling of incomplete evacuation.19

Back to Top | Article Outline
Bone quantitative ultrasound.

Quantitative ultrasound evaluation of bone was performed using the Omnisense 7000S ultrasound bone sonometer device, designed to measure speed of sound (SOS) of axially transmitted ultrasonic waves. The examinations were performed at 2 body sites: distal third of radius and midshaft tibia. The radius examination served as a control in the non-WB area. The site of examination for the radius reading was defined as the point halfway between the edge of the olecranon and the tip of the distal phalanx of the outstretched third digit of the left hand. The position of the examination needed the child’s hand to be extended and externally rotated. This position was very inconvenient for the majority of the children, and was not performed with those who felt uncomfortable. Mid-tibia bone quantitative ultrasound (BQUS) measurement was performed with the patient prone and the knee flexed at 90°. The site of examination was the point halfway between the edge of the heel and the proximal edge of the knee.

The BQUS device was calibrated before each examination against a control block supplied by the manufacturer. A special pediatric transducer was placed on the site and rotated without lifting the transducer from the skin. SOS measurements were taken repeatedly. When the SOS score was reproduced 3 times in a row at the premarked location, that measurement was used. The reproducibility of BQUS has been investigated in several studies. These studies reported an intra- and interoperator measurement coefficient of variation for the Omnisense device between 0.8% and 1.68% at the radius and 0.3% to 1.03% at the tibia, which did not significantly affect the reported data.20,21 In this study, the maximum accepted intraoperator variability was 0.6% to 0.7% at either site. Z scores (the difference between the patient’s value and the age-specific mean value divided by the reference group’s standard deviation) were calculated for each patient. The reference group was represented by more than 2000 healthy children.22

Back to Top | Article Outline
Exposure Quantification.

To quantify the exposure to each device (HW or SF), a time and weight quantification was done. Information from the parental and therapist diaries concerning frequency and duration usage of each device was summarized. The weight load on the child’s legs during standing was measured using an electronic strain gauge weight scale at entry time to the program and at the end of the follow-up period 6 months later.

Back to Top | Article Outline
Procedures

Before the study began, all subjects were receiving physical therapy based on neurodevelopmental treatment (NDT) principles. Treatment included passive stretching of lower limb muscles (eg, hamstrings, gastrosoleus), followed by techniques for reducing spasticity and facilitating more normal patterns of movement while working on motor functions (including lower-extremity weight-bearing activities). A standing program in a SF 4 times a week for 30 minutes was part of the NDT treatment. Parents were encouraged to use a SF at home, for example during the time the child watches television. All the children in the study underwent the NDT treatment program. The control subjects continued with the program which included the standing sessions. Children in the study group, however, did not use the SF but practiced a standing and stepping program in the HW.

The HW is a gait trainer that provides support to allow the child to walk. It has a customized brace section for the trunk, pelvis, and lower limbs attached via a spring-loaded weight-relieving attachment to a wheeled frame, which provides both weight-bearing support and leg alignment while allowing upper extremity freedom. In this study, all the children wore piedro orthotic boots as part of the HW. No ankle foot orthosis (AFO) was used.

The brace was fitted around the child’s trunk, pelvis, and lower limbs and was adjusted to the child’s individual needs so as to optimize the child’s lower extremity alignment, and to provide support and directional control of the limbs. The brace was fitted while the child was supine, and then transferred to the wheeled frame. The frame’s support mechanism offered the child an adjusted amount of WB support and gait guidance during walking. No modifications were made in the original device.

The program began with 30-minute sessions, 4 times a week but the children as well as parents were encouraged to use the HW device. One way of motivating the children to continue using the HW device was through group activity sessions during the physical therapy session in the treating center, or by asking the parents to use it at home while going out to the shopping center or to the neighborhood playground.

The beginning of the intervention period was used to accustom the children to the HW and to teach the caregiver how to position the children in the HW and to assist in resolving any problems, as well as to encourage adherence to the program. During the training sessions, manual assistance was provided to assist the lower extremities to perform the gait pattern.

During the standing session in the HW or during the SF activity session, heart rate (HR) was obtained using a wireless heart rate monitoring device (Polar, Finland).

A certified physical therapist with >10 years of clinical experience in pediatrics carried out all the assessments which were conducted at entry time and 6 months later. In addition, at the end of each month the physical therapist contacted each child’s family and treating therapist and reminded them to fill out the diary regarding exposure frequency and duration, any adverse events, and the bowel activity data.

Back to Top | Article Outline
Data Analysis

Descriptive analyses of the demographic and medical characteristics are presented in Table 1. Differences between groups at entry time were assessed; continuous variable differences were assessed using a Student t test; for categorical variables a chi square test was used. The distribution of outcome measures showed similar patterns as in a normal curve [Kolmogorov-Smirnov (K-S) test for normality; PEDI scale score range between K-S z: 0.60–0.80, p 0.54–0.86; BQUS z values range between K-S z: 0.80–0.84, p 0.48–0.53; HR values range between K-S z: 0.56–0.87, p 0.43–0.90]. Treatment effect on PEDI score, BQUS z score, and HR at rest and during exposure to the device (SF or HW) was subjected to a repeated measures ANOVA with a between subjects factor of group (study vs control) and a within subject factor of time (entry time, 6-month follow-up). As no difference in the proportion of children who suffered constipation was found at entry time, the difference in that proportion at the end of follow-up was subject to the chi square test. The change in walking parameters among the HW group was subject to a paired t test. Results were considered statistically significant at a confidence level p ≤ 0.05. Data were analyzed using a SPSS-v.12 statistical package (SPSS, Chicago, Ill).

Back to Top | Article Outline

RESULTS

Table 2 presents the exposure parameter to vertical WB among both groups. The exercise diaries of the HW participants showed a significant increase in the duration per week of vertical weight-bearing exposure compared with no change for the controls (F1,20 = 7.9, p = 0.01). Children in the HW group doubled the time per week in standing and stepping position compared to base line. There was no significant difference in the percent of body weight-bearing on the lower extremity during the 6 months of follow-up, or between groups.

Table 2
Table 2
Image Tools

Significant differences between groups in the PEDI mean score was found at entry time (Table 3). The HW group exhibited a higher significant mean score in the self-care and social function domain (p ≤ 0.01). There was no significant difference in those scores between groups during the follow-up period (p > 0.05). The mobility domain showed a similar mean value at entry time in both groups. A significant change was seen while using the HW in the mobility domain at entry time in the HW group (pair t test, t = 7.6, p < 0.01). In addition, a significant improvement in the mobility domain over time was seen while using the HW in the HW group (pair t test, t = 2.2, p = 0.03).

Table 3
Table 3
Image Tools

Insignificant differences between groups in the QUS z mean score were found at entry time. The HW group exhibited an insignificantly lower mean score (p = 0.12). During the intervention period both groups exhibited a decline in the mean QUS z scores with no significant differences between groups (F1,20 = 1.42, p = 0.25). When combining both study samples in to one group, there was a significant moderate association between standing time and bone quality (BQ) (rp = 0.47, p = 0.02); a longer time spent in an upright position correlates with better BQ.

The proportion of participants with constipation (54.5%) was the same in both groups at entry time (see Fig. 1). After 6 months of follow-up, a significant reduction in that proportion was noted among the HW group, with no change among the controls (p = 0.02).

Fig. 1
Fig. 1
Image Tools

A significant improvement in mean distance covered during 2 minutes was found among the HW group. All children, except one, increased the distance. At the end of the study, the children’s mean walking speed was 0.08 m/sec, far below functional walking speed.

Back to Top | Article Outline

DISCUSSION

The main findings of this study indicate that no adverse events occurred during the 6-month follow-up. Children exposed to the HW had improved bowel function, but no additional benefit on BQ compared with passive standing was observed. In addition, all children exposed to the HW were able to take steps independently with the device, but up to the end of the follow-up they walked very slowly and did not reach a functional walking speed.

The mean time exposure to the HW per week increased significantly during the 6-month period with no adverse events reported by therapists or parents. It is important to note that all the children were able to express themselves by talking or by using signs. In this way, most children agreed to use the equipment but none asked to use it. Parents and therapists were both satisfied with the HW except for parents of the older and larger children who encountered some difficulties while lifting the child in and out of the HW frame. Wright et al23 evaluated the long-term use (3 years) of the HW among 20 children with CP and found that the HWs inability to accommodate larger children was the primary reason for its discontinuation. In their study, as in ours, most parents found it difficult to take the child in and out of the HW and brace.

At the end of the follow-up, the children in the study group used the HW for 4.5 hours, compared with 2.1 standing hours per week in the controls. In this study, we found an association between exposure time to standing in the SF or being in the HW and BQ as assessed by the BQUS in all participants. However, we did not find any significant differences between groups. A longer time spent in an upright position with WB correlates with better BQ.

Osteogenic signals from the muscles combined with loading of the bone due to gravity are the 2 possible mechanisms by which standing may stimulate bone formation and prevent bone depletion. It may be that the loading component of WB is the most dominant factor in determining BQ, while the additional stepping activity in the HW has no significant effect on BQ.

There is little evidence for the use of a standing program as a way to maintain or improve BMD. Furthermore, no guidelines exist for a standing program for children with CP, and the treating physical therapist is left to decide the frequency, duration, type of standing regimen, and frame, based on one’s clinical experience. The evidence which does exist showed a reduction in bone density in children with CP when a standing program is interrupted for 2 to 3 months,7 or that immobilization of young children with CP, usually after orthopedic operative procedures, is associated with diminished BMD in the lumbar spine.3 On the other hand, another study presents the results of an 8-month program of weight-bearing physical activity which enhances bone mineral accrual in children with CP. Those studies support the concept that a relationship exists between WB and BQ, and a minimal period of unloading or loading is enough to change the BQ among children with CP.24 For children and adolescents who are healthy, the mechanical loading set point (“mechanostat”) that stimulates bone formation as theorized by Frost25 may necessitate a relatively high-impact stimulus. However, for children whom mobility is limited, such as those with severe CP, the bone formation set point may be lowered and minimal loading would be sufficient to stimulate bone formation.

Further, increasing evidence suggests that childhood is an especially critical period for bone mineral accrual which is a major component of bone strength.26 It might be important to expose children with limited mobility to the HW as soon as possible especially when they are young. In this study, it was found that duration of use with the HW increases with time. In addition, the feasibility of using the HW was found to be higher while the child is small, which increased the response rate to the device.

Another finding is the favorable effect of the HW exposure on constipation. Children in the HW group exhibited a significant reduction in constipation rate with no change among the controls. This finding might be related to the stepping activity while standing or might be due to a 2.25 average time increase in the upright position among the HW group or due to the combination of these two.

Underlying mechanisms regarding the association between physical exercise and constipation are unclear, but a favorable effect on colonic motility, decreased blood flow to the gut, biomechanical bouncing of the gut during stepping, and compression of the colon by abdominal musculature have all been reported.27 The reduction in the number of children who suffer from constipation was the first phenomena which parents reported at the follow-up session.

Walking velocity at the end of the HW training period was very slow and was not a functional walking speed. But the ability to move independently in erect position to any desired direction is an important experience for children. Many parents stated that one of the most important features of the HW is the opportunity it gives to the child for participation with family and peers.

Back to Top | Article Outline

LIMITATIONS

The main limitation of this study is that it is a follow-up based on a convenient sample of children exposed to the HW with controls matched for age and sex, which may lead to the significant baseline differences between groups in the PEDI score on social and self-care function (mean difference between groups of 19.8 and 10.6 point, respectively). It was established previously that an 11% change in PEDI scores is a “clinically important difference,” which means that a true change is observed.16 It may be assumed that an 11% difference in scores between groups is also “a true difference.” The familiarization process using the HW and the training session as in any active treatment is based on communication with the child and the child’s motivation. In addition, those differences might reflect wider real differences between groups in other parameters that can affect the results of the study.

It may be assumed that children with higher levels of social and self-care skills are more motivated to participate in any activity, and that they are able to understand better what is being asked from them. Therapists identify motivation and family support as being important determinants of motor change for children with CP. Research involving infants developing typically has indicated that child characteristics of temperament28 and motivation29 are potential influences on early motor development. Global issues of family resources, quality of the home environment, family support, parental expectations, and family functioning are potential important influences on motor development.30

The second limitation is the WB assessment method which was used. Recording the weight 3 times, 5 minutes postexposure to the HW or to the SF might not be representative of the total exposure period. The third limitation is that many factors may contribute to low bone mineralization. Those factors have been cited extensively in the literature and include genetic, hormonal, nutritional (especially calcium and vitamin D) and WB physical activity. In this study, only the WB component was assessed and the above factors may affect the results.

Back to Top | Article Outline

CONCLUSION

In this study, it was found that children with severe CP, (GMFCS level V) tolerate stepping activity while standing. All children exposed to the HW doubled by mean the time which they spent in standing position, they were able to take steps independently with the device, but up to the end of the follow-up they walked very slowly. Increase in standing time and stepping activity while standing, improved bowel function. No additional benefit on BQ compared with passive standing was observed. As increasing evidence suggests that childhood is an especially critical period for bone mineral accrual which is a major component of bone strength, it may be important to expose those children to the HW especially when they are young. In this study, it was found that duration of use with the HW device increases over time. In addition, the feasibility of using the HW device was found to be higher while the child is small, which increased the response rate to the device.

In the future, we suggest using a randomized control trial to assess the contribution of stepping and the minimal exposures demands of standing and stepping to improve functional performance and secondary condition prevalence among young children with severe CP and to follow them for longer period to assess long-term effects for such programs.

The ability of offering a previously nonambulatory child the opportunity to walk may be important both for maximizing participation in activities of daily living and social roles and for the possible preventative effect of secondary conditions.

Back to Top | Article Outline

ACKNOWLEDGMENTS

The authors thank Orna, Vivian, Alik, Liora, Hila, and Dr Silia Kozakov from “Ziv” Hospital and the therapists from the “Yovalim” school for giving us the opportunity to conduct this study. They also thank the children who participated in the study and their parents for their assistance during the study.

Back to Top | Article Outline

REFERENCES

1. Jones MW, Morgan E, Shelton JE, et al. Cerebral palsy: introduction and diagnosis (part I). J Pediatr Health Care. 2007;21:146–152.

2. Turk MA, Geremski CA, Rosenbaum PF, et al. The health status of women with cerebral palsy. Arch Phys Med Rehab. 1997;78:S10–S17.

3. Henderson RC. Bone density and other possible predictors of fracture risk in children and adolescents with spastic quadriplegia. Dev Med Child Neurol. 1997;39:224–227.

4. Tasdemir HA, Buyukavci M, Akcay F. Bone mineral density in children with cerebral palsy. Pediatr Int. 2001;43:157–160.

5. Mac Neela JC. An overview of therapeutic positioning for multiply-handicapped persons, including augmentative communication users. Phys Occup Ther Pediatr. 1987;7:39–60.

6. Gudjonsdottir B, Stemmons M. Effects of a dynamic versus a static prone stander on bone mineral density and behavior in four children with severe cerebral palsy. Pediatr Phys Ther. 2002;14:38–46.

7. Lanyon LE, Rubin CT. Static vs dynamic loads as an influence on bone remodelling. J Biomech. 1984;17:897–905.

8. Stuberg WA. Considerations related to weight-bearing programs in children with developmental disabilities. Phys Ther. 1992;72:35–40.

9. Rubin CT, Lanyon LE. Regulation of bone formation by applied dynamic loads. J Bone Joint Surg Am. 1984;66:397–402.

10. Biewener AA, Bertram JE. Structural response of growing bone to exercise and disuse. J Appl Physiol. 1994;76:946–955.

11. Wilmshurst S, Ward K, Adams JE, et al. Mobility status and bone density in cerebral palsy. Arch Dis Child. 1996;75:164–165.

12. Henderson RC, Lin PP, Greene WB. Bone-mineral density in children and adolescents who have spastic cerebral palsy. J Bone Joint Surg Am. 1995;77:1671–1681.

13. Palisano RJ, Hanna SE, Rosenbaum PL, et al. Validation of a model of gross motor function for children with cerebral palsy. Phys Ther. 2000;80:974–985.

14. Haley SM, Coster WJ, Ludlow LH. Pediatric Evaluation of Disability Inventory (PEDI) [Manual]. Boston, MA: New England Medical Center; 1992.

15. Custers JWH, van der Net J, Hoijtink H, et al. Discriminative validity of the Dutch Pediatric Evaluation of Disability Inventory. Arch Phys Med Rehabil. 2002;83:1437–1441.

16. Iyer LV, Haley SM, Watkins MP, et al. Establishing minimal clinically important differences for scores on the Pediatric Evaluation of Disability Inventory for inpatient rehabilitation. Phys Ther. 2003;83:888–898.

17. Mossberg KA. Reliability of a timed walk test in persons with acquired brain injury. Am J Phys Med Rehabil. 2003;82:385–390.

18. Kosak M, Smith T. Comparison of the 2-, 6-, and 12-minute walk tests in patients with stroke. J Rehabil Res Dev. 2005;42:103–107.

19. Harari D, Gurtwitz JH, Avorn J, et al. Bowel habit in relation to age and gender: findings from the national health interview survey and clinical implications. Arch Intern Med. 1996;156:315–320.

20. Hodgskinson R, Njeh CF, Currey JD, et al. The ability of ultrasound velocity to predict the stiffness of cancellous bone in vitro. Bone. 1997;21:183–190.

21. Van Rijn RR, van der Sluis IM, Lequin MH. Tibial quantitative ultrasound versus whole body and lumbar spine DXA in a Dutch pediatric and adolescent population. Invest Radiol. 2000;35:548–552.

22. Weiss M, Ben-Shlomo AB, Hagag P, et al. Reference database for bone speed of sound measurement by a novel quantitative multi-site ultrasound device. Osteoporos Int. 2000;11. 688–696.

23. Wright F, Belbin G, Slack M, et al. An evaluation of the David Hart Walker Orthosis: a new assistive device for children with cerebral palsy. Phys Can. 1999;51:280–291.

24. Goemaere S, Van Laere M, De Neve P, et al. Bone mineral status in paraplegic patients who do or do not perform standing. Osteoporos Int. 1994;4:138–143.

25. Frost H. Bone “mass” and the “mechanostat”: a proposal. Anat Rec. 1987;219:1–9.

26. Chad KE, Bailey DA, McKay HA, et al. The effect of a weight-bearing physical activity program on bone mineral content and estimated volumetric density in children with spastic cerebral palsy. J Pediatr. 1999;135:115–117.

27. Peters HPF, De Vries WR, VanBerge-Henegouwen GP, et al. Potential benefits and hazards of physical activity and exercise on the gastrointestinal tract. Gut. 2001;48:435–439.

28. Werner EE. Vulnerable but invincible: high-risk children from birth to adulthood. Acta Paediatr. 1997;422:103–105.

29. Thelen E, Smith LB. A Dynamic Systems Approach to the Development of Cognition and Action. Cambridge, MA: The MIT Press; 1994.

30. Bartlett DJ, Palisano RJ. A multivariate model of determinants of motor change for children with cerebral palsy. Phys Ther. 2000;80:598–614.

Keywords:

bone density; cerebral palsy; child; constipation; durable medical equipment; gastrointestinal motility; human movement system; outcome measures; physical therapy/methods; walkers; walking

© 2009 Lippincott Williams & Wilkins, Inc.

Login

Article Tools

Images

Share

Follow PED-PT on Twitter

Search for Similar Articles
You may search for similar articles that contain these same keywords or you may modify the keyword list to augment your search.