Biomechanical analysis of a transverse olecranon fracture model using tension band wiring.

PURPOSE

To determine (1) the most distal site at which a tension band construct can maintain bony alignment during dynamic loading of a transverse, length-stable olecranon osteotomy; (2) the location of displacement during cyclical loading; and (3) the ultimate load to failure of the fixation.

METHODS

We divided 23 non-osteoporotic, fresh-frozen upper extremities into 4 groups. We created transverse osteotomies at 25% of the olecranon surface in group 1, 50% in group II, 75% in group III, and 100% in group IV. We used standard tension band wiring technique to stabilize each osteotomy. We mounted specimens on a biomechanical testing machine at 90° elbow flexion and subjected them to a 150-N sinusoidal load through the triceps tendon at 1 Hz for 500 cycles. An optical motion tracking system synchronized with the testing machine-measured displacement of the osteotomy in any plane. On completion of cycling, we loaded specimens at 1 mm/s until 2-mm displacement occurred. We analyzed data to determine the effect of the location of the osteotomy on load to failure and location of displacement.

RESULTS

Of the 23 specimens, 21 survived the cycling process. The 2 specimens that failed were both in group II (50%). Excluding these 2 specimens, the average displacement at the 3 virtual points was less than 1.05 mm in all 4 osteotomy groups. There were no statistical differences between groups. Load to failure was 476, 361, 511, and 610 N for groups I to IV, respectively. Differences between groups were not statistically significant.

CONCLUSIONS

The stability achieved with tension band wire fixation did not vary with the location of the osteotomy.

CLINICAL RELEVANCE

Based on this biomechanical study, when it is properly executed, tension band wire fixation may be used effectively for transverse, length-stable fractures of the olecranon regardless of the amount of articular surface included on the proximal fragment.