Extra-articular step osteotomy of the olecranon: A biomechanical assessment

Trans-olecranon chevron osteotomies (COs) remain the gold standard surgical approach to type C fractures of the distal humerus. This technique is associated with a high complication rate and development of an extra-articular olecranon osteotomy may be advantageous. The aim of this study was to compare the load to failure of COs with extra-articular oblique osteotomies (OOs) as well as modified, extra-articular step osteotomies (SOs).

These three osteotomies and their subsequent fixation utilizing a standardized tension band wiring technique were tested in 42 composite analog ulnae models at 20° and 70° of flexion. Triceps loading was simulated with a servo hydraulic testing machine. All specimens were isometrically loaded until failure. Kinematic and force data, as well as interfragmentary motion were recorded.

At 70°, CO failed at a mean load of 963 N (SD 104 N), the OO at 1512 N (SD 208 N) and the SO at 1484 N (SD 153 N), (P<0.001). At 20°, CO failed at a mean load of 707 N (SD 104 N) and OO at 1009 N (SD 85 N) (P=0.006). The highest load to failure was observed for the SO, which was 1277 N (SD 172 N). The load to failure of the SO was significantly higher than the CO as well as the OO.

Extra-articular osteotomies showed a significantly higher load to failure in comparison to traditional CO. At near full extension (20° of flexion), this biomechanical advantage was further enhanced by a step-cut modification of the extra-articular oblique osteotomy.