Estimating the location of the posterior interosseus nerve during an extensor digitorum communis-splitting approach: a comparison of methods using the transepicondylar distance.

Background: The posterior interosseus nerve (PIN) may be encountered when using the extensile extensor digitorum communis (EDC)-splitting approach to the elbow. An accurate means of estimating its location remains elusive. The purpose of this investigation is to identify whether the methods described in previous studies can be improved upon to more accurately estimate the PIN's location using the transepicondylar distance (TED).

Methods: Forty-five fresh-frozen cadavers were dissected using the EDC-splitting approach. Method A (N = 39) used an electronic caliper measuring along the midlateral border of the radius from the lateral epicondyle (LE) and radiocapitellar joint in supination, neutral position, and pronation. Method B (N = 16) used a sterile tape measure, measuring from the LE in pronation only along an axis from the LE to Lister's tubercle passing through the center capitellum.

Results: In method A, the mean TED was 63.4 ± 6.1 mm. Of the 6 measurements, the TED was most correlated to the actual distance to the PIN from the LE in pronation (68.3 ± 7.3 mm; R = 0.266). The median difference between the estimated and actual distances was -5.6 mm (-19.3 mm to 7.6 mm). In method B, the mean TED was 68.4 ± 8.7 mm, and the mean measured distance from the LE in pronation was 68.7 ± 9.4 mm. The TED closely correlated with the measured distance to the PIN (R = 0.95,  < .001). The mean difference between the estimated and actual distances was ±2.0 mm (range -4.0 mm to 2.0 mm), significantly more precise than method A ( = .007).

Conclusion: Using a tape measure, the TED predicted the PIN's location within a mean ±2 mm in pronation along an axis from the LE to Lister's tubercle, using an EDC-splitting approach. This technique is simple and comparatively more accurate than those used previously.