Bone Abstracts

Bone loading is a primary determinant of bone strength in later childhood and adulthood. Our understanding of how mechanical stimuli generated by foetal kicking and movements impact skeletal development is still limited. Many studies suggest that a sufficient and balanced supply of energy, proteins, vitamins, calcium, phosphorus, and other nutrients is an essential prerequisite for normal bone development. However, only few studies highlight the contribution of the biomechanical environment in utero on the fetal skeleton. Recent studies have provided new insight suggesting a role for stress stimulation in ossification events and for strain stimuli in joint morphogenesis. This stimulation is known to be critical for prenatal musculoskeletal development. Infants whose movement in utero is reduced subsequently suffer from joint dysplasia and thin hypomineralized bones and demonstrate that embryonic movement is crucial for appropriate skeletogenesis. This has been confirmed in different animal models. We present the cases of two patients seen in our Bone Clinic at Sainte-Justine University Hospital between 2013 and 2018. They all presented fractures of lower limbs at an early age (2,5 and 5 months respectively), and were found to have low bone mineral density upon DXA testing. A shared characteristic between patients was that all two pregnancies presented with a polyhydramnios of unknown etiology in the third trimester, as assessed by routine ultrasound. They presented no family history of bone disease, and genetic testing for neuromuscular diseases or bone fragility was negative in all patients. They showed to be catching up on bone mineral density within the year following the onset of fractures without receiving anti-osteoporotic treatments. Based on the mechanostat theory, we hypothesize that polyhydramnios plays as a significant risk factor for low bone mineral density. A larger amount of liquid in the amniotic cavity could limit the rate and intensity of limb loading, resulting in lower peak force applied on the spine as well. To the best of our knowledge, this is the first case series to investigate a connection between polyhydramnios and bone strength in the perinatal period. It could lead the way to researches connecting pre-birth biomechanical factors to bone health in infancy.

Disclosure: The authors declared no competing interests.