Real-Time Monitoring with a Controlled Advancement Drill May Decrease Plunge Depth

Although drill use is fundamental to orthopaedic surgery, the risk of plunging past the far cortex and potentially damaging the surrounding soft tissues remains unavoidable with conventional drilling methods. A dual motor drill may decrease that risk by providing controlled drill-bit advancement and real-time monitoring of depth and energy expenditure. We hypothesized that using the dual motor drill would decrease plunge depth regardless of the user's level of experience.

Sixty-six subjects of varying operative experience (20 attending orthopaedic surgeons, 20 orthopaedic surgery residents, and 26 senior medical students) drilled 3 holes with a conventional drill and 3 holes with a dual motor drill in a bicortical Sawbones block set in ballistic gel. The depth of drill penetration into the ballistic gel was measured for each hole using a digital caliper.

Overall, subjects plunged less with the dual motor drill (0.9 mm) than with the conventional drill (4.2 mm) (p < 0.001). This finding was consistent within each group: attending surgeons (0.9 compared with 3.2 mm; p = 0.02), residents (1.0 compared with 3.0 mm; p < 0.001), and students (0.7 compared with 6.0 mm; p < 0.001). Plunge depths were also stratified into 3 categories: 0 to <2 mm, 2 to 5 mm, and >5 mm. Using the dual motor drill, subjects were more likely to plunge <2 mm (97% plunged, on average, 0 to <2 mm and 3% plunged, on average, 2 to 5 mm), whereas subjects were more likely to plunge deeper with the conventional drill (27% plunged, on average, 0 to <2 mm, 45% plunged, on average, 2 to 5 mm, and 27% plunged, on average, >5 mm). Notably, no subject plunged ≥2 mm on the third attempt with the dual motor drill. Attending surgeons (p = 0.02) and residents (p = 0.01) plunged less than students with the conventional drill. There was no significant difference between attending surgeons and residents with the conventional drill (p = 0.96). There was no significant difference in plunge depth between groups using the dual motor drill.

The dual motor drill significantly decreased plunge depth for both surgically experienced and inexperienced subjects. Although inexperienced subjects performed worse with the conventional drill than those with experience, there was no difference in their performance with the dual motor drill.

Use of a controlled advancement drill may decrease the chance of plunge-related neurovascular injury during in vivo drilling.