What is Plagiocephaly
Deformational Plagiocephaly (DP), a medical condition more commonly known as ‘flat head syndrome’ (FHS), which occurs when an infant’s head becomes flatten and or misshaped due to the head continually resting on a surface that does not conform or support the shape of a baby’s head. Infant heads are soft to allow for the initial passage through the birth canal and then the incredible brain growth that occurs in the first year of life. During the early months of life they are more susceptible to being “molded” into a flat shape or taking the form of the surface that the skull is in contact with.
Plagiocephaly develops when an infant’s rapidly growing head attempts to expand, and meets some type of resistance— either prenatally in the mother’s womb, or more commonly after delivery because the back or side of a baby’s head is pressed against a mattress, car seat or other flat surface.
This condition affects many infants, especially since the widespread introduction of the “Back to Sleep” campaign which recommends that babies are placed to sleep on their back (supine sleep) that was introduced in 1994 and has made significant inroads to reducing the number of SID’s (Cot Deaths) by an estimated 46% in some countries. However, the by-product of the supine sleeping is a significant increase of FHS which is now at epidemic proportions according the AAP (American Academy of Pediatrics) affecting nearly 50% of all baby by the age of 2 moments. (www.aap.org, 2013)
Babies suffering from Torticollis are also at risk of developing FHS due the nature of the condition which is a tight or shortened muscle in one side of the neck causes the head to tilt or turn to one side, resulting in the infant resting its head in the same position.
A report issued by the AAP looked at the long term developmental outcomes in infants with FHS. More evidence is emerging but it has long since been acknowledged by the medical profession that the affects of FHS are not limited to aesthetics.
Infants with FHS comprise of a high-risk group for development difficulties presenting as subtle problems during the school-age years. Many studies have indicated other issues include the Miller and Clarren report (Robert I Miller) that showed 39.37% of patients with FHS required an individual education plan. In a report issued in the Journal of Developmental & Behavioural Pediatrics on Neurodevelopmental Implications of “Deformational” Plagiocephaly show that 33% of patients displayed mild to significant mental developmental issues when measure against the MDI (Mental Developmental Index – BSID- III). Further studies indicate that before any intervention, infants with deformational plagiocephaly show significant delays in both mental and psychomotor development. Also of particular note is that no child with deformational plagiocephaly showed accelerated development. (Kordestani, 2006)
Analysis of the deformation of each model (Fig. 13) shows that the ClevaFoam® model deformed more than the stiffer case of only the mattress. Furthermore, greater contact area between the cranium and its support was predicted for ClevaFoam® support condition (Fig. 14) — 2,959 mm2 for the mattress and 5,644 mm2 for the pillow. This increase in contact area for the pillow support leads to a reduction in the contact pressure (i.e. the contact force per unit area) since the force (i.e. the gravitational load, which was 8.55 N) is the same for each model. Thus the mattress support was predicted to apply an average contact pressure of 2.9 kPa to the skull while the pillow applied an average pressure of 1.5 kPa.
Figure 13: Cross-sectional view of contact areas between skull and each support material: (a) mattress and (b) foam pillow. Yellow regions indicate contact areas between the various bodies in the model.
Fig. 14. Oblique view of occipital contact areas (yellow regions) for (a) standard mattress and (b) ClevaFoam®support condition. Greater contact area is apparent for the ClevaFoam model.
A benefit of using the finite element method is the ability to predict internal loading and deformation of the tissues. Two measures of loading were examined for the two models: von Mises stress (indicative of the forces generated within the tissue) and strain energy density (indicative of the energy of deformation). Contours of stress (Fig. 15) show that stress was not distributed uniformly within the contact region. Local concentrations were predicted around the suture regions for both models. In particular local stress in these regions was up to an order of magnitude higher than the man contact pressure. Furthermore, a larger region of highly loaded tissue was predicted for the occipital region of the mattress support. This trend was more pronounced when examining the strain energy density of the exterior cranial tissue (Fig. 16). Both stress and strain-energy density were more localized to the sutures for the pillow support condition. In general, stresses were relatively low (< 25 kPa) in the occipital region of both models.
Figure 15: Von Mises stress distribution in occipital region of skull for each support type: (a) mattress and (b) foam pillow. Lower stresses were predicted for the foam pillow support condition.
Figure 16: Strain energy density for occipital region of skull for each support type: (a) mattress and (b) pillow. Lower strain energy density was predicted for the foam pillow support condition.
In conclusion, simulations of supine rest of an infant cranium in contact with two different supporting materials, (i) a generic infant mattress and (ii) a Clevamama® ClevaFoam™ Baby Pillow, supported a hypothesis that use of the compliant polyurethane foam pillow can reduce mean contact pressure at the occiput by increasing contact area through greater conformant deformation. This study represents a first step in determining the local mechanical environment in the tissue of the contact region for an infant head resting in a supine position. The ability to study this mechanical environment opens the possibility of further study of the role of mechanical loading in the development of deformational plagiocephaly.