The effect of drill trajectory on proximity to the posterior interosseous nerve during cortical button distal biceps repair

Purpose: The aim of this study was to evaluate the effect that different drill trajectories across the radius have on the proximity of the drill tip to the posterior interosseous nerve (PIN). Methods: In 10 cadaveric specimens, we drilled from the bicipital tuberosity across the radius using 4 different trajectories: (1) aiming across the radius at 90° to the longitudinal axis of the radius, (2) distally at 45°, (3) ulnarly, and (4) radially. We measured the distance between the tip of the drill as it exited the dorsal cortex of the radius and the PIN. Results: Aiming 90° across the radius and aiming ulnarly across the radius resulted in a distance of 11.2 ± 3.2 mm (95% confidence interval [CI], 8.9 to 13.5 mm) and 16.0 ± 3.8 mm (95% CI, 13.3 to 18.7 mm), respectively, between the drill tip and the PIN. Aiming the drill 45° distally and aiming radially resulted in a distance of only 2.0 ± 2.2 mm (95% CI, 0.5 to 3.6 mm) and 4.2 ± 2.2 mm (95% CI, 2.6 to 5.8 mm), respectively. The differences were found to be statistically significant. Conclusions: On the basis of the results of this anatomic study, when using the cortical button distal biceps repair technique, we recommend drilling across the radius at 90° to its longitudinal axis and aiming from 0° to 30° ulnarly, with the patient's forearm in full supination. This provides an increased margin of safety to prevent injury to the PIN compared with drilling radially or distally. Clinical Relevance: By avoiding distal and radial drilling, the risks of PIN injury should be minimized during distal biceps tendon repair.