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Ginny Paleg, MS, PT
Instructor
| Joined: | Fri Jul 14th, 2006 |
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| Posts: | 6 |
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Posted: Fri Dec 8th, 2006 01:09 pm |
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Body-weight support treadmill stepping in infants with spina bifida
Smith BA, Moerchen VA, Ulrich BD.
PURPOSE: The overall purpose of this research project is to understand more clearly the developmental trajectory and sensorimotor capacities of infants born with spina bifida and to lay a strong empirically based foundation for designing therapeutic interventions to be tested. More specifically, the goal of this study is to map the developmental trajectory of the stepping and non-stepping responses of babies born with spina bifida over the first postnatal year when in a body-weight supported treadmill (BWST) context.
BACKGROUND/SIGNIFICANCE: Spina bifida (SB) is the second most common congenital birth defect in the United States (need citation). Incidence varies around the world, and is particularly high in developing countries (International Federation for Spina Bifida and Hydrocephalus, 2004). Depending on the level of the lesion, anywhere from 20% (high lumbar lesion) to 90% (sacral lesion) of infants with SB learn to walk (Backer, 2002). Infants with SB who learn to walk usually do so around 3 years of age (Findlay et al., 1987; Swank & Dias, 1992). In contrast to the aggressive physical therapy adults with acquired spinal cord lesions receive early post-lesion, infants with SB typically do not receive therapy until 6-9 months after birth, or 14-17 months post lesion. This lack of therapy is likely due to both the difficulty of identifying developmental delay earlier than 6 months of age and the lack of evidence regarding efficacy of early intervention in this population. Previous studies involving infants with Down syndrome showed that BWST training leads to earlier walking onset (Ulrich, Ulrich, Angulo-Kinzler, & Yun, 2001). The BWST context allows infants opportunities to experience upright posture, practice stepping, and explore the subsystems related to gait. However, infants respond differentially to the treadmill over time. Experimental data for infants with typical development (TD) suggests that muscle strength influences the newborn stepping response across time; during some periods of development the stepping response is deterred by relatively heavy legs (Thelen, Fischer, & Ridley-Johnson, 1984; Thelen et. al, 1984). Infants with DS also respond differently to the BWST context; they begin to step on the treadmill about 10 months later than infants with TD (Ulrich et al., 1995). Before therapeutic interventions can be designed and tested we need to know how and when infants with SB will step on the treadmill.
PARTICIPANTS: Participants were 10 infants born with SB and 6 infants born with TD. Infants with SB have lumber or sacral lesions, 36 weeks or longer gestation, and no other disorders not associated with SB. Infants with TD have no known developmental disorders.
METHODS AND MATERIALS: Newborn stepping response and treadmill stepping behaviors were elicited from infants at 1, 3, 6, 9, and 12 months of age. Newborn stepping response elicitation consisted of 4-6 trials of the infant being held under the arms in a semi-weightbearing position and progressed forward slowly along a firm surface. Treadmill stepping elicitation consisted of infants being supported under the arms in a semi-weightbearing position on a small motorized treadmill. Data was collected during 2 20-second trials in each of the following 6 treadmill conditions: a baseline condition with a stationary treadmill belt, .08 m/s, .12 m/s, .16 m/s, .20 m/s, and .24 m/s. Data collected included digital video of all trials, joint location, EMG, and anthropometric measurements. Joint location information was collected using a Peak Motus 6-camera system and reflective markers placed bilaterally on the bony anatomical landmarks of the iliac crest, greater trochanter, knee joint line, lateral malleolus, and third metatarsophalangeal joint. EMG data was collected bilaterally from the muscle bodies of the tibialis anterior, gastrocnemius, quadriceps femoris, and hamstring muscles.
ANALYSES: Trained behavior coders watched the digital videos and counted the total number of steps (all types) taken during newborn stepping response elicitation trials and treadmill stepping elicitation trials.
RESULTS: Mean total number of newborn stepping response steps taken by infants with TD remained relatively constant from 4.5+/-3 steps at month 1 to 4.5+/- 1.5 steps at month 12. Mean total number of newborn stepping response steps taken by infants with SB decreased from 4.5+/-4.5 steps at month 1 to 2.5+/- 1.5 steps at month 12. Mean number of total treadmill steps taken by infants with TD increased linearly from 90+/-50 steps at month 1 to 160+/- 25 steps at month 12. Mean number of total treadmill steps taken by infants with SB showed a decrease from 60+/-50 steps at month 1 to 40+/-30 steps at month 3. This value remained relatively constant until an increase to 90+/-60 steps at month 12.
CONCLUSIONS: Infants with SB showed a similar response to infants with TD during newborn stepping response elicitation at month 1. In the following months, the performance of infants with SB decreased while the performance of infants with TD remained stable. In the BWST context, infants with SB showed a diminished treadmill stepping response overall when compared to infants with TD. They also showed a period of minimal progress across months 3, 6, and 9. However, infants with SB did respond to the BWST context over the first postnatal year by taking steps, demonstrating potential value for BWST training in this population. BWST training intervention could promote muscle strengthening and take advantage of neural plasticity to promote development of the neuromuscular patterns necessary to support the onset of gait. There is also potential to improve bone density, cardiovascular function, and the integrity of lower spinal sensorimotor function. Infants with SB demonstrate developmental delay as early as 3 months of age and BWST intervention during the first postnatal year has the potential to reduce this delay and promote earlier onset of gait in the population with spina bifida.
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