Evaluation of Heat Generation in Unidirectional Versus Oscillatory Modes During K‐Wire Insertion in Bone

Abstract

Heat generation during insertion of Kirschner wires (K-wires) may lead to thermal osteonecrosis and can affect the construct fixation. Unidirectional and oscillatory drilling modes are options for K-wire insertion, but understanding of the difference in heat generation between the two modes is lacking. The goal of this study was to compare the temperature rise during K-wire insertion under these two modes and provide technical guidelines for K-wire placement to minimize thermal injury. Ten orthopedic surgeons were instructed to drill holes on hydrated ex vivo bovine bones under two modes. The drilling trials were evaluated in terms of temperature, thrust force, torque, drilling time, and tool wear. The analysis of variance showed that the oscillatory mode generated significantly lowered peak bone temperature rise (13% lower mean value, p = 0.036) over significantly longer drilling time (46% higher mean time, p < 0.001) than the unidirectional mode. Drilling time had significant effect on peak bone temperature rise under both modes (p < 0.001) and impact of peak thrust force was significant under oscillatory mode (p < 0.001). These findings suggest that the drilling mode choice is a compromise between peak temperature and bone exposure time. Shortening the drilling time was the key under both modes to minimize temperature rise and thermal necrosis risk. To achieve faster drilling, technique analysis found that "shaky" and intermittent drilling with moderate thrust force are preferred techniques by small vibration of the drill about the K-wire axis and slight lift-up of the K-wire once or twice during drilling.

Comparison of k‐wire insertion using oscillatory and unidirectional drilling modes under constant thrust force

“…During steady‐state drilling, while peak spindle speed was similar under the two drilling modes (1300–1400 rpm under unidirectional mode and 1200–1300 rpm under oscillatory mode), due to the oscillation nature, the oscillatory mode had 54% lower average spindle speed, leading to lower cutting speed, smaller material removal rate, and thus shallower drilling depth as well as longer total thermal exposure time for bone. These findings aligned with results from previous surgeon‐based studies 27 . If avoidance of the torque oscillation with high peak values at the transient stage or the long heat exposure time of the bone was of specific concern during k‐wire insertion, the unidirectional mode should be considered.…”

“…Preliminary trials showed that these three wight levels (5, 7, and 9 kg) yielded an average constant thrust force of 66, 83, and 102 N, correspondingly. Such range was a good replication of thrust force range (about 50–110 N) applied by surgeons during K‐wire insertions 27 . Under each loading level, a new and sharp trocar tip K‐wire with 2 mm diameter and 15° bevel angle (as shown in Figure 2D,E) was used under each mode to drill four holes along the longitudinal direction on a single bone sample, as shown by the eight holes drilled in Figure 1C.…”

“…Note that this study was meant to conduct quantitative analysis of the K‐wire insertion process from the machining perspective to gain better understanding of the heat generation under different modes and thrust forces. The continuous drilling with constant thrust force used in this study might not be the optimal technique in clinical practice as it could block bone debris evacuation and heat dissipation 27 . This study was ex vivo rather than in vivo in nature to help better control the experimental condition and be able accurately measure temperature rise.…”

“…The oscillatory mode was reported to reduce the bone temperature rise and tissue damage around the drilling site. 25,26 To compare the temperature rise during K-wire insertion under these two modes and provide technical guidelines for K-wire placement to minimize thermal injury, Luo et al 27 instructed orthopedic surgeons to conduct K-wire insertion trials under both modes. It was found that the oscillatory mode generated lower bone temperature rise but needed longer drilling time than the unidirectional mode and shortening the drilling time is the key under both modes to control temperature rise and reduce the risk of thermal necrosis.…”

Hollow Notched K‐Wires for Bone Drilling With Through‐Tool Cooling

“…Hutchinson et al found that insertion of external fixation pins into pre‐drilled holes generated lower temperature than insertions without predrilling. Luo et al reported that, during the K‐wire drilling by orthopedic surgeons, (i) the oscillatory drilling mode had lower bone temperature rise than the unidirectional mode due to lower material removal rate and (ii) the shaky and intermittent drilling techniques had lower bone temperature rise than continuous drilling because of improved debris evacuation and heat convection.…”