Ideal pin length and interval in tension band wiring using ring pins for transverse olecranon fractures: a biomechanical study.

Background: Several clinical and biomechanical studies on tension band wiring (TBW) using a ring-pin system have been conducted, but no consensus has been reached on the ideal surgical technique. In this study, we aimed to determine the ideal interval and length of ring pins for the treatment of transverse olecranon fractures using TBW with a ring-pin system.

Methods: A biomechanical study was performed using 32 fourth-generation composite ulnae and a ring-pin system specially designed for TBW. Four groups of eight sawbones were created based on the interval and length of the ring pins. A cyclic loading test was performed to measure stability during the active range of motion exercises. A load-to-failure test measured the maximal load until fixation loss.

Results: All groups were stable, with a micromotion of < 1.0 mm, except for Group 3 (length: 50 mm, interval: 10 mm) during the cyclic loading test. The mean micromotion and displacement of Group 3 were significantly higher than those of Groups 2 and 4 (length: 90 mm, interval: 10 mm). The maximal load to failure in Group 3 was significantly lower than that of Groups 2 and 4.

Conclusion: Inserting two ring pins in parallel at a 10-mm interval with a length of ≥ 70 mm for TBW in transverse olecranon fractures is recommended. Further widening of the pin interval provides no biomechanical benefit and may result in technical difficulties owing to the anatomical features of the ulna; in summary, 50-mm ring pins show significantly lower mechanical strength.