Faculty Bibliography

The neurovascular anatomy of the carpus and hand is complex. Therefore, precise exposures are required to avoid iatrogenic injury. In general, dorsal exposures are more forgiving than volar exposures because major neurovascular structures lie on the volar aspect of the hand and fingers; however, volar, ulnar, and radial approaches to the carpal bones are also commonly used. Exposure of the metacarpals and phalanges is relatively straightforward by comparison. Exposure of the carpus and hand is also complicated by the dense and often superficial innervation network. Therefore, a thorough knowledge of the pertinent anatomy is required for safe surgical approaches to the wrist and hand.

PURPOSE: Displaced olecranon fractures are often amenable to treatment with open reduction and tension-band wiring. The purpose of this study is to examine the relationships of the tips of K-wires used in a tension-band construct to volar neurovascular structures in the proximal forearm and the proximal radioulnar joint. METHODS: We performed simulated percutaneous pinnings of the proximal ulna under fluoroscopic guidance on 15 cadavers with intact proximal ulnas. The K-wires were drilled obliquely through the tip of the olecranon process and directed to engage the anterior ulnar cortex, distal to the coronoid. Using calipers, we measured the distance from the tip of each pin to the anterior interosseous nerve (AIN), ulnar artery, proximal radioulnar joint (PRUJ), and volar cortex of the ulna, as well as the distance from the volar cortex of the ulna to the AIN and ulnar artery. The angle created by the K-wires and the longitudinal axis of the ulna was measured on both anteroposterior and lateral radiographs. RESULTS: The distance from pin tip to the AIN and ulnar artery measured a mean of 16 mm with a standard deviation of 6 mm and 14 mm with a standard deviation of 5 mm, respectively, with 1 pin abutting the artery. The shortest distance from both the AIN (11 +/- 5 mm) and the ulnar artery (8 +/- 6 mm) was measured with the shallowest angle of insertion, ranging from 10 degrees to 14.9 degrees on lateral radiographs. The mean distance between the pin tip and the PRUJ measured 7 mm with a standard deviation of 4 mm, with 3 pins penetrating the PRUJ. CONCLUSIONS: The impaction of K-wires under the triceps is often approximately 1 cm, which is similar to the distance of the K-wire tips to the AIN and ulnar artery. Our findings suggest that larger insertion angles might help avoid neurovascular injury when the insertion point of the K-wires is at or just proximal to the tip of the olecranon. In this study, the safe zone for pin insertion on the anteroposterior view is 0 degrees to 10 degrees , and on the lateral view it is 20 degrees to 30 degrees . CLINICAL RELEVANCE: This anatomic study was done to diminish the chance of complications resulting from K-wire placement during tension-band wiring for olecranon fractures.