Locking-plate osteosynthesis versus intramedullary nailing for fixation of olecranon fractures: a biomechanical study

Abstract

Purpose: Intramedullary nailing and locked plating for fixation of olecranon fractures has recently gained popularity. However, these two new technologies have not been compared for their biomechanical efficacy. The aim of this study was to evaluate the biomechanical stability of two newly designed fracture fixation devices for treating olecranon fractures during dynamic continuous loading: the ION intramedullary locking nail and the LCP precontoured locking compression plate.

Methods: Simulated oblique olecranon fractures were created in eight pairs of fresh-frozen cadaver ulnae and stabilised using either the LCP or ION. Specimens were then subjected to continuous dynamic loading (from 25 to 200 N), with a continuous angle alteration between 0° and 90° of flexion, to perform a matched-pairs comparison. Significant differences in the distance between markers surrounding the fracture gap was determined using the Wilcoxon test after four and 300 loading cycles.

Results: The ION resulted in significantly less displacement in the fracture gap at 0° extension (P = 0.036), 45° flexion (P = 0.035) and 90° flexion (P = 0.017) after 300 cycles of continuous loading. The measured displacements were small and were probably not of clinical significance. No mechanical failure or hardware migration was seen with either fixation technique.

Conclusion: This study shows significantly less micromotion for the ION than for the LCP in treating oblique olecranon fractures after 300 cycles of dynamic loading. Both implant types could be appropriate surgical techniques for fixation of selected olecranon fractures and osteotomies.

Fig. 1

Precontoured locking compression plate (LCP): Distally, the ulna is potted in polymethylmethacrylate (PMMA). The triceps tendon is lengthened with nylon sutures for fixation to the cable wire applying the pull force

Fig. 2

Intermedullary olecranon nail (ION): The proximal screw is fixed through an end-cap locking mechanism. Three locking holes in the proximal part and three holes in the distal part perpendicular to each other allow multiplanar locking

Fig. 3

Test setup showing the polymethylmethacrylate (PMMA) potted olecranon with a locking compression plate (LCP) implanted and markers on the lateral side of the osteotomy. The triceps tendon (1) is fixed with nylon sutures to a 1.2-mm wired steel cable, and the dynamically applied pull force (2) works over two bearing pulleys (3, 4). The rotating platform (5) imitates flexion and extension during the test procedure

Fig. 4

During a cycle of the test procedure, elbow motion changed from 0° (extension) to 90° (flexion), and the pull force of the triceps tendon changed from 25 N to 200 N (synchronised and with phase displacement). A maximum force of 200 N is applied in 50° of flexion after 2.5 seconds, and a minimum force of 25 N in flexion of 50° is applied after 7.5 seconds

Fig. 5

Intermedullary olecranon nail (ION) in flexion with a pair of markers on distal and proximal fragments. The range (a and b) between the two pairs of markers is measured as a mean value [x = (a + b)/2] to demonstrate the extent of motion right in the middle (x) between the two fragments