Modified tension band wiring technique for olecranon fractures: where and how should the K-wires be inserted to avoid articular penetration?

Objective: Articular penetration of K-wires is a possible complication of the modified tension band wiring technique. However, there is no clear information or evidence regarding the entry point or introduction angle for K-wires to avoid this complication. The aim of this experimental study was to evaluate the effect of varying K-wire insertion points and angles on the risk for articular penetration during modified tension band wiring for olecranon fractures. Methods: All anatomical measurements were made on 50 cadaveric ulnas, and all other measurements were performed on exact foam replications of the 50 cadaveric ulnas. Morphometric measurements, including olecranon height and heights of the central, radial and ulnar facets of the semilunar notch, were taken. In the sagittal plane, articular angle and tubercle angle were measured. Two 1.6-mm parallel K-wires were inserted from 0, 5 and 8 mm anterior to the dorsal cortex of the olecranon process at angles of 20° and 30°. K-wire articular penetration was evaluated both visually and radiographically. Results: The mean central, radial and ulnar heights of the semilunar notch were 17.3 mm (14.7–20.0), 16.2 mm (12.0–21.0) and 15.8 mm (13.30–20.5), respectively. We observed no articular penetration at the 0-mm level at 20° and 30° (0 mm 20° and 0 mm 30°, respectively) or at 5 mm 20°. At 8 mm 30° wire introduction, more than 64% articular penetration was observed on either facet. The sequence from least to most likely to cause articular penetration was: 0 mm = 5 mm 20° 5 mm 30° = 8 mm 20° 8 mm 30°. The radial height of the semilunar notch was negatively correlated to the risk of articular penetration, when the wire was introduced at 8 mm 30°, 8 mm 20° and 5 mm 30° (all p 0.047). There were poor correlations between radiological and direct observational assessments, particularly for 8 mm 20°and 5 mm 30°. The frequency of intra-articular positioning for those observed to be radiologically extra-articular was 4/28 (14.3%) for 8 mm 30°, 4/7 (57.1%) for 8 mm 20° and 5/6 (83.3%) for 5 mm 30°. Conclusion: When applying the modified tension band wiring technique to prevent articular penetration, K-wires should be inserted in the first 5 mm from dorsal cortex of the olecranon process at a maximum angle of 20°. Moreover, if the wires are required to be inserted more anteriorly because of the anatomical configuration of the fracture, they should be inserted at a shallow angle in the sagittal plane in relation to the proximal cortex of the ulna.