Beads but no collar; the significance of an asymptomatic rib bone healing pattern in infants

Summary 

When a long bone, such as a rib, is broken, the position of the break can be seen in the following weeks by a temporary collar of a collagen based material (callus) which holds the broken ends together during the repair process. However in infants a different pattern is sometimes found at autopsy, in which the repair material occurs as widely spaced “beads” along the shaft of the rib. The consistency of the bead material corresponds to the progress of repair in the normal way, but there is no focal region as would be expected in a clean break or greenstick fracture. It is proposed that this results from micro-fractures in the compact bone forming the outer aspect of the rib when it is bent excessively, during thoracic compression such as required in Cardiopulmonary Resuscitation, (CPR), or when the infant is “grabbed” when about to slip from the hands of a carer. The compact bone surface is covered by a relatively very elastic layer, the periosteum, which carries nerves sensitive to stretch or tearing of this periosteum. It is proposed that the local stretch induced in the periosteum bridging these micro-fractures is insufficient to cause these nerves to signal pain and so the condition is asymptomatic, and may be quite common in infancy. It should not be confused with imposed trauma.