STABILITY OF METAL AND CABLE TENSION BAND CONSTRUCTS FOR SIMULATED OLECRANON FRACTURES

Abstract

Purpose: Presently, tension band figure-of-eight fixation of olecranon fractures is usually performed with stainless steel wire. A polyethylene cable cerclage has been proposed as an alternative to lessen the complications associated with wire. This study compared the stability of tension band constructs for olecranon fracture fixation using a polyethylene cable cerclage or a stainless steel wire cerclage.

Methods: Ten matched pairs of fresh-frozen cadaveric elbows, without radiographic abnormality, were selected for the study. In each specimen, a transverse fracture was created by an osteotomy at the middle of the sigmoid notch of the olecranon. One elbow of each pair was randomized for tension band fixation with a figure-of-eight construct while the other was fixed by tension banding with a loop cerclage. Two different materials, stainless steel wire and isoelastic polyethylene cable, were randomly selected to create the cerclage constructs in each elbow. The triceps tendon was controlled and cyclic loads were applied to the dorsal cortex of the ulna 8 cm distal to the fracture site to create a bending moment. The elbow was initially preconditioned at 45 N for 100 cycles, followed by four periods of 300 cycles each, from 45 N to 120 N in 25 N increments. Dynamic and static fracture gap for the different configurations and materials were recorded.

Results: No difference in static gap was found between the metal figure-of-eight, cable figure-of-eight and cable loop constructs (p> 0.05). The metal loop was found to have significantly greater gap (p=0.0013) than the other 3 constructs. No difference was observed in dynamic gap at the peak loads for any of the constructs (p=0.3379).

Conclusion: This study demonstrated that the biomechanical performance of tension band fixation in an olecranon fracture model using a polyethylene cable in either figure-of-eight or loop construct is similar to that of the stainless steel wire figure-of-eight construct and should be considered as an option to the traditional stainless steel wire. This type of soft and tissue tolerant fixation may lessen the known clinical complications of wire fixation while providing equivalent stability under physiologic loads which would permit early rehabilitation.