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.