Hammering versus drilling of sharp and obtuse trocar-point k-wires.

Kirschner wire characteristics affect the heating of bone during insertion and the subsequent strength of fixation. We inserted 90 sharp and 90 obtuse trocar-tip K-wires into 90 fresh frozen human cadaver metacarpals using either a drill or a pneumatic hammer. The temperature elevation, insertion time and extraction force were measured for four K-wire insertion combinations: drilling sharp; drilling obtuse; hammering sharp; hammering obtuse. Hammering resulted in significantly lower temperature elevations than drilling. Hammering sharp K-wires resulted in the highest extraction forces. The first and fifth metacarpals showed significantly lower temperature elevations than the other metacarpals, while the insertion time was significantly higher in the second and third metacarpal than in the other metacarpals. Hammering sharp trocar-tip K-wires minimises thermal damage to bone and gives the strongest fixation.