Pull-off characteristics of double-shanked compared to single-shanked ligation clips: an animal study

BACKGROUND: The use of surgical ligation clips is considered as the gold standard for the closure of vessels, particularly in laparoscopic surgery. The safety of clips is mainly achieved by the deep indentation of the metal bar with a high retention force. A novel double-shanked (DS) titanium clip was compared to two single-shanked clips with respect to axial and radial pull-off forces. METHODS: In a porcine model (8 animals, 51±1 kg), arteries were prepared immediately after euthanisation, assigned to either a medium (2–4 mm; n=120) or a medium-large (3.5–7 mm; n=120) clip size group, and clipped with the appropriate clip size. After dissection, axial and radial pull-off forces were measured. RESULTS: The axial pull-off force of the DS-Clip was higher than one single-shanked clip and comparable to the other single-shanked clip, and overall was linearly correlated to the cross-sectional area of the clip. The radial pull-off force of the DS-Clip was significantly higher than both single-shanked clips and, for the single-shanked clips, was correlated to the total clip thickness. The variation of radial pull-off force was lower for the DS-Clip due to a defined catch in the clip applier. CONCLUSIONS: The radial pull-off force was lower than the axial pull-off force in total and therefore appears to be the critical point of dislocation. Due to the higher total holding mass, the DS-Clip provided a clear advantage in this regard and might therefore decrease the dislocation rate. The catch in the applier increases the reproducibility in clip placement.