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Several studies have demonstrated that young infants who present with unexplained fractures have a higher frequency of joint hypermobility, either in themselves or their parents, compared to the general population. The joint hypermobility is often associated with the autosomal dominant hypermobile form of Ehlers Danlos Syndrome (h-EDS) in which the mother is far more likely the affected parent. Most of these infants have metabolic bone disease as their radiographs often show poor bone mineralization. Some have alleged these infants were abused, while others have stated infants who have h-EDS or a parent with h-EDS are at increased risk to fracture as a result of a permanent, intrinsic connective tissue abnormality in the bone of the infant with h-EDS.If these infants were not abused and the fractures were from an intrinsic bone abnormality with an increased risk to a fracture, this increased fracture risk would be expected to persist throughout the lifetime of the affected infant. However, this is not the case as the propensity to fracture in these infants is transient with few fractures after 6 months of age. This observation begs for another explanation for the etiology of the increased fracture risk as an infant, but much less so after 6 months of age.I believe there is a different mechanism to explain this transient, increased fracture risk in infants with joint hypermobility from h-EDS born to mothers with h-EDS. In such a mother-infant pair with h-EDS the infant has joint hypermobility and the mother’s uterus has hyperelasticity. I hypothesize that both of these factors cause diminished fetal bone loading when the infant with joint hypermobility strikes the uterus with hyperelasticity. Simple principles of physics are used to demonstrate this. Diminished fetal bone loading causes diminished fetal and young infant bone strength for the first 6 months of life that begins to normalize after about 6 months of age.This hypothesis would explain the transient nature of the increased fracture risk for once born, these factors would cease to be present in the postnatal time period, but their influence would last for about 6 months. This finding has important implications in child abuse investigations of infants with unexplained fractures.



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