In vivo biomechanical comparison of hammering vs drilling of Kirschner wires; a pilot study in rabbits

Hammering K-wires is superior to drilling with irrigation

Cooling during drilling Kirschner wires is not always effective in preventing thermal related damage. In this study, we used a human in vitro model and compared temperature elevation, insertion time, and extraction force between three Kirschner wire insertion methods-drilling with and without irrigation and pneumatic hammering. Forty five Kirschner wires were inserted into 15 fresh human cadaver metacarpals. All three insertion methods were applied in each metacarpal. Drilling without irrigation resulted in a temperature elevation of 67.25 +/- 5.4 degrees C with significantly lower values for drilling with irrigation (4.15 +/- 0.6 degrees C) and pneumatic hammering (31.52 +/- 3.4 degrees C). The insertion time for pneumatic hammering (47.63 +/- 8.8 s) was significantly lower compared to drilling without irrigation (263.16 +/- 36.5 s) and drilling with irrigation (196.10 +/- 28.5 s). Extraction forces after drilling without irrigation, drilling with irrigation, and pneumatic hammering were 39.85 +/- 4.1 N, 57.81 +/- 6.5 N, and 62.23 +/- 6.7 N, respectively. Pneumatic hammering is superior to drilling without irrigation, especially when irrigation is not possible.

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.