The effect of drilling angle on posterior interosseous nerve safety during open and endoscopic anterior single-incision repair of the distal biceps tendon

Purpose: The purpose of this study was to define a safe trajectory with regard to iatrogenic posterior interosseous nerve (PIN) injury when drilling the bicipital tuberosity for EndoButton repair (Smith & Nephew Endoscopy, Andover, MA) of distal biceps tendon ruptures. Methods: Ten cadaveric forearms were dissected. The bicipital tuberosity was exposed and the biceps tendon detached. The supinator and PIN were exposed dorsally. A K-wire was drilled perpendicular to the surface of the tuberosity. By use of digital calipers, the distance from the exit point of this wire to the PIN was measured. The length of the bone tunnel was also measured. This wire was removed, and a second was drilled from the same starting point but directed 30 degrees ulnarly. Measurements were repeated. A Wilcoxon signed rank test was used to compare the distances of the K-wire to the PIN and the tunnel lengths for both trajectories. Results: With the perpendicular wire, the mean distance to the PIN was 11.1 mm. When directed 30 degrees ulnarly, the mean distance was 16.4 mm. The difference was significant (P < .001). The mean bone tunnel lengths for the 2 trajectories were 17.8 mm and 18.1 mm; this was not found to be significant (P = .508). Conclusions: When drilling the bicipital tuberosity, we advocate starting at a center-center position on the face of the tuberosity, holding the forearm in maximum supination, and aiming 30 degrees ulnarly to decrease the risk to the PIN. This trajectory does not decrease the bone tunnel length available for implants. Clinical Relevance: This cadaveric anatomic study establishes safety from iatrogenic PIN injury during drilling of the bicipital tuberosity for the purpose of open or endoscopic EndoButton repair of distal biceps tendon ruptures.