Self Regulated Physical Activity and Bone Growth Enhancement in Premature Infants

Overview

Premature very low birth weight (VLBW) infants were placed in two groups matched for birth age. The control group received traditional joint compression exercises designed to decrease bone density loss. Exercises lasted approximately 10 minutes each day 5 days a week. The experimental group were placed in a "prepod", an elastic fabric pod shaped garment or sack on entry into the study and remained in the pod essentially 24 hours a day, with brief breaks for bathing, parental skin to skin experiences,etc. An ultrasound of the left tibia was done on entrance into the study at 31 to 32 weeks gestation and again at completion of the study 4 weeks later. Results showed that experimental infants in pods had slightly less bone density loss than their peers receiving traditional therapy. An incidental finding was that the experimental infants in pods had a significantly shorter length of stay.

During fetal development the developing babe pushes against the uterine wall, often kicking and punching the unfortunate mother, especially during the last few months of pregnancy. The striking out against the resistance of the uterine wall causes joint compression in the arms, legs, and spine and that sensory feedback triggers bone growth. Unfortunately in the premature infant they are robbed of that exercise opportunity and are either splayed out in an incubator trying to copy with movement against gravity or swaddled so that movement isn't really an option. As a result bone density loss occurs in essentially all premature infants and osteopenia or significant loss can be an issue. Between 1995 and 2008 there was a good deal of work done on identifying the importance of exercise and movement for premature infants. Moyer-Mileur was the leading researcher in the USA who demonstrated that simple exercise programs could prevent or decrease bone density loss. Although there is a shortage of trained therapists to provide these exercises safely they became a fairly common practice by 2010. At about that time the neonatologists at the Asante facility asked to incorporate the exercises into the NICU therapy program and after appropriate training the exercises began. The Asante NICU is highly developmentally oriented. Infants grow 150 million brain cells an hour during the last few months of pregnancy. Any of the multiple stressors of prematurity can create cortisol and affect that brain growth. For that reason therapists became concerned with the joint compression exercises. While they were good for bone and muscle health the exercises were not always welcomed by the infant. Even the most gentle compassionate therapist is not always welcome if the infant just wants to sleep or be left alone. Therapists sought a system that could provide the needed exercise but in a manner more developmentally appropriate. It took two years of experimenting with different types of materials and different strengths of elasticity before the Prepod design finally evolved. Then the obvious hypothesis was - Will the Prepod be as effective in decreasing bone density loss as the traditional therapy exercises?? After multiple issues replacing originally planned DEXA measurements with safer UTS measurements, the first subjects were enrolled in 2013. Unfortunately in 2015 an issue with the ultrasound machine was identified; the anti-theft anklets the infants wore emitted signals that had corrupted the data. The study needed to be restarted in 2015, removing the anklets prior to measurement. It then proceeded without incident, with expected completion late 2018. At the IRB (Institutional Review Board) review winter of 2017 the overseeing group concluded that the data for length of stay was so compelling that continuing the study wasn't likely to change anything and basically amounted to withholding care from the traditional exercise infants. They ordered early closure of the study, despite the small number of study participants.