Radicals generated by bone cutting and fracture

When bone fractures, a remarkably high yield of radicals is generated. By working at 77K, these are stable enough for detection and study. Major species have been identified by ESR (EPR) spectroscopy as alkyl peroxyl radicals and RCH2· radicals. Also, a species thought to be O·− radicals, formed in the mineral phase, was detected in relatively low yield. It is suggested that as a break is generated, the mineral crystallites separate at grain boundaries with no major chemical damage, but that the tightly bound collagen strands running through the mineral phase are forced to break homolytically. Some probably react together, others react with oxygen, while the remainder are trapped in their primary form. The characteristic hyperfine triplet is assigned in part to RCH2· radicals from glycine units, which constitute about one-third of the total amino acid components in collagen, and in part to RNHO radicals. The possible significance of the formation of active radicals during bone fracture is discussed