Rib histology after unsuccessful cardiopulmonary resuscitation in infants suffering sudden death from natural causes; implications for injury mechanism and timing.

Aims: To describe whether haemorrhage into the fracture gap, bone marrow, or periosteum, and loss of osteocyte nuclei from infant rib fracture margins, are true markers of vitality or may be seen solely as a consequence of cardiopulmonary resuscitation attempts.
Methods and Results: A description is provided of histological findings in sampled rib fractures in a retrospective consecutive series of infants, aged 1 month to 1 year, who suffered sudden death. All had undergone cardiopulmonary resuscitation (CPR) and were investigated by use of skeletal survey, whole body computed tomography (CT), and invasive postmortem (PM). There was no suspicion of child abuse. 15 infants were studied, 9 of whom had anterior/anterolateral rib fractures; slides were available with consent for use in seven. Skeletal survey identified no fractures. CT and PM showed 46 fractures, 27 of which were examined histologically. Marrow cavity haemorrhage> 2 mm in diameter was seen in 55% of fractures; easily identifiable red cells were seen in the fracture gap in 36%, and beneath the periosteum in 36%. Loss of intact osteocytes from lacunae in bone fragments at the fracture margins relative to distant areas was obvious in 50% of fractures.
Conclusions: Anterior rib fractures, visible on CT and histologically, are common after CPR in infants. Empty lacunae and bleeding into the fracture gap, into the marrow cavity and beneath the periosteum are all frequent in CPR-related infant rib fractures, and should not be used to discriminate between true in-vivo injury and perimortem injury.
(© 2020 John Wiley & Sons Ltd.)