The effect of surgically implanted bullet fragments on the spinal cord in a rabbit model

Background: Whether or not to remove bullets or bullet fragments from the s pinal column of a neurologically intact patient has been a subject of conti nual debate. The controversy is due in part to a lack of information about the long-term effects of bullet fragments on spinal cord tissue. Although m any studies have demonstrated the toxic effects of metal fragments on brain tissue, to our knowledge no one has evaluated the effects of the metals co ntained in commercially available bullets on spinal cord tissue. Methods: Copper, aluminum, and lead fragments from three commercially avail able bullet cartridges were implanted in intradural and extradural location s in seventeen New Zealand White rabbits. At an average of 9.8 months, the metal content of specimens of blood, cerebrospinal fluid, and liver were de termined. The spinal cords were harvested and examined histologically. Results: There was a significant increase in the copper revel of blood from the rabbits with an implanted copper fragment compared with that of the co ntrol animals (p = 0.007). Concentrations of copper and lead were not eleva ted, compared with the control values, in the serum or liver. Histological examination of the spinal cords revealed major destruction of both the axon s and the myelin of the dorsal column adjacent to the intradural copper fra gments. intradural fragments of lead caused similar destruction of myelin a nd axons in the dorsal column, but to a lesser degree. Minimal spinal cord or meningeal histological changes were noted around the aluminum intradural fragments, and no pathological changes were found near any fragments place d in an extradural location. Conclusions: The results of this study show that certain metals contained i n commercially available bullets can cause varying degrees of neural destru ction independent of the initial mechanical injury caused by implantation. Of the three metals tested, copper fragments consistently caused a substant ial localized area of neural injury within the spinal cord. Clinical Relevance: In our study, copper fragments caused local neural toxi city involving as much as 10% of the spinal cord area, suggesting that ther e may be a scientific basis for removal of copper fragments lodged in the s pinal cord, even in the absence of a neurological deficit.