Biomechanical comparison of interfragmentary compression in transverse fractures of the olecranon.

Compression and absolute stability are important in the management of intra-articular fractures. We compared tension band wiring with plate fixation for the treatment of fractures of the olecranon by measuring compression within the fracture. Identical transverse fractures were created in models of the ulna. Tension band wires were applied to ten fractures and ten were fixed with Acumed plates. Compression was measured using a Tekscan force transducer within the fracture gap. Dynamic testing was carried out by reproducing cyclical contraction of the triceps of 20 N and of the brachialis of 10 N. Both methods were tested on each sample. Paired t-tests compared overall compression and compression at the articular side of the fracture. The mean compression for plating was 819 N (sd 602, 95% confidence interval (CI)) and for tension band wiring was 77 N (sd 19, 95% CI) (p = 0.039). The mean compression on the articular side of the fracture for plating was 343 N (sd 276, 95% CI) and for tension band wiring was 1 N (sd 2, 95% CI) (p = 0.038). During simulated movements, the mean compression was reduced in both groups, with tension band wiring at -14 N (sd 7) and for plating -173 N (sd 32). No increase in compression on the articular side was detected in the tension band wiring group. Pre-contoured plates provide significantly greater compression than tension bands in the treatment of transverse fractures of the olecranon, both over the whole fracture and specifically at the articular side of the fracture. In tension band wiring the overall compression was reduced and articular compression remained negligible during simulated contraction of the triceps, challenging the tension band principle.