A biomechanical comparison of multidirectional nail and locking plate fixation in unstable olecranon fractures

The main theoretic advantage of proximal olecranon fracture intramedullary fixation is decreased soft-tissue irritation and, potentially, less subsequent hardware removal. Despite this possible benefit, questions remain as to whether intramedullary devices are capable of controlling olecranon fractures to the same extent as locking plates. This study evaluates the ability of a novel multidirectional locking nail to stabilize comminuted fractures and directly compares its biomechanical performance with that of locking olecranon plates.

We implanted 8 stainless steel locking plates and stainless steel intramedullary nails to stabilize a simulated comminuted fracture in 16 fresh-frozen cadaveric elbows. Flexion-extension, varus-valgus, gap distance, and rotational 3-dimensional angular displacement analysis was conducted over a 60° motion arc (30° to 90°) to assess fragment motion through physiologic cyclic arcs of motion and failure loading. Displacements in all planes were compared.

Both implants showed less than 1° of motion in all measured planes and allowed less than 1 mm of gapping through all loads tested until ultimate failure. All failures occurred by sudden, catastrophic means. The mean failure weight for the nail was 14.4 kg compared with 8.7 kg for the plate (P = .02). The nail survived 1102 cycles, whereas the plate survived 831 cycles (P = .06).

In simulated comminuted olecranon fractures, the multidirectional locking intramedullary nails sustained significantly higher maximum loads than the locking plates. The two implants showed no significant differences in fragment control or number of cycles survived. Surgeons can expect the multidirectional locking nails to stabilize comminuted fractures at least as well as locking plates.