Bayonet Tip versus Drill Tip Wires: Are they Deflected Similarly by Bone?

BACKGROUND

The use of percutaneous wires is a crucial part of the Ilizarov technique, the success of which relies partly upon the accurate insertion of percutaneous wires in order to achieve adequate fixation. Currently, there is uncertainty about which of the two types of wire is superior – the drill tip or the bayonet tip wire.

TECHNIQUE

The aim of the experiment was to test whether there was a significant difference in the degree to which each type of Ilizarov wire was deflected by bone. The apparatus was constructed as depicted in Figure 1. Each bone was sequentially drilled using the different Ilizarov wires and the measurements of deflection recorded. The bone was drilled at 5-mm intervals to ensure that fresh bone was encountered on each recording. The drill operator was blinded to the type of Ilizarov wire used for each recording; the wires were changed and positioned for drilling out of sight of the drill operator.

Figure 1.

Schematic of the apparatus.

DISCUSSION

There was no difference in the distance which the two wire types were deflected by bone at the 1% level (P > 0.99). The results are shown in Table 1. The drilling efficiency and temperature elevation of different wires has been tested by Piska et al.¹ The distance by which a wire is deflected by bone is important as increased deflection may increase both the risk of damaging neurovascular structures and of repeated insertion attempts becoming necessary. While the amount of thrust may be important in the deflection of wires, these two types of wire were deflected by similar amounts despite the fact that different thrusts were probably required for their insertion.

Table 1.

Results

	Bayonet tip wire set	Drill tip wire set
Mean distance from zero (mm)	7.0	7.0
SD	3.9	3.6
Variance	15	13
Number of recordings	20	20