Where should the pins be placed to decrease the failure rate after fixation of a Mayo IIA olecranon fracture? A biomechanical analysis.

BACKGROUND: Clinically, treatment of Mayo IIA olecranon fractures (MIOF) using pins is associated with a high rate of failure. The purpose of our study was to compare the biomechanical stability and strength of four different fracture fixation configurations and to recommend the best method for the clinical treatment of MIOFs.

METHODS: Twenty synthetic ulnar models were created and equally divided into 4 different fracture fixation groups: a double cortical configuration using Kirschner (K) wires; a double cortical configuration using transcortical pins; an intramedullary pin system; and an intramedullary pin system with a 3-mm distance between the eyelet and the proximal end of the olecranon (loose fixation). The stiffness and strength of all specimens were tested under a loading rate of 2 mm/min. Between-group differences were evaluated using an independent t-test, with significance set at P < 0.05.

RESULTS: Stiffness and strength were significantly better for the K-wire than intramedullary group: stiffness, 63.467±14.063 N/mm and 36.243±5.625 N/mm, respectively (P=0.009); and strength, 624.293±148.728 N and 406.486±74.109 N, respectively (P=0.019). There was no difference in stiffness (P=0.370) or strength (P=0.929) between the use of transcortical pins and K-wires. Moreover, a 3-mm prominence of the pin at the olecranon did not have a negative effect on either stiffness (P=0.494) or strength (P=0.391).

CONCLUSIONS: Our biomechanical analysis indicated that using a double cortical pin configuration provided the best stability and strength and, thus, may lower the risk of fracture fixation failure. The use of either K-wires or pins in the double cortical configuration did not influence fixation stability. A loose double cortical configuration might decrease fracture stability, although there differences were not significant.