What Is the Ideal Starting Point for an Olecranon Screw? An Anatomic Cadaveric Study.

OBJECTIVE: To assess whether "center-center" position is ideal starting point for minimum fracture displacement when placing an intramedullary (IM) screw in the ulna. METHODS: Thirty-six arms (average age, 82 years) underwent a posterior approach to the olecranon and were randomized into 3 groups: center-center (center in sagittal plane, center in coronal plane), posterior-lateral (posterior in sagittal plane, lateral in coronal plane), and posterior-medial (posterior in sagittal plane, medial in coronal plane). Groups were matched into 18 pairs, and fixation was performed with an IM screw. Primary outcome measure was articular surface displacement on the olecranon. Measurements were compared across each combination of locations using the Kruskal-Wallis rank sums test, and a sign test determined whether each location differed from anatomic reduction. RESULTS: Articular step-off measurements were significantly different between center-center (0.6 mm) and posterior-medial (2.1 mm) groups (P = 0.01) and approached significance with posterior-lateral versus posterior-medial (0.9 mm) locations (P = 0.07). No significant difference was found comparing center-center with posterior-lateral locations (P = 0.7). The articular surface (P = 0.04), posterior cortex (P = 0.02), and medial cortex (P = 0.001) measurements for the posterior-medial starting point were all worse compared with anatomic reduction. CONCLUSIONS: Malreduction of a simulated olecranon fracture was most significant when the starting point for the IM screw was malpositioned medially. A central or laterally based starting point was more forgiving. Avoiding a medially based starting point is crucial for achieving benefits of fixation with an IM screw and reduces the chance of malreduction after fixation.