Inferior load generated by preloaded versus manually loaded haemorrhoid banding devices: the effect of 'creep relaxation'

Abstract

BACKGROUND: The efficacy of rubber band ligation of haemorrhoids relies on the load generated on haemorrhoidal tissue by bands as they return to their preformed shape after being deployed. 'Preloaded' haemorrhoid banding devices are widely available, but the effect of the resultant prolonged stretch on bands while stored in this manner has never been examined by comparing these to manually loaded devices, which are stretch immediately prior to being deployed. A difference could have clinical relevance, potentially resulting in a higher rate of clinical failure. The present study aimed to investigate any difference in load generated by preloaded versus manually loaded devices. METHODS: A preloaded and a manually loaded device were selected for comparison. Each type was measured on a testing rig. The device type, load generated by each band and the time to expiry were recorded. RESULTS: A total of 137 haemorrhoid bands were tested: 66 preloaded and 71 manually loaded. There was a statistically significant overall reduction in load generated by preloaded versus manually loaded devices (284.0 versus 272.1 g, mean difference -11.9 g, 95% confidence interval -17.5 to -6.3 g, P = 0.0001). Adjusted for time, the load generated by preloaded bands fell 3.7 g (95% confidence interval 2.7-4.8, P < 0.001) for each month closer to the expiry date. CONCLUSIONS: The load generated by haemorrhoid bands from preloaded devices is lower and deteriorates significantly towards their expiry date compared with bands from manually loaded devices. This is mostly likely due to their storage in a stretched state. This should be considered by clinicians when using haemorrhoid banding devices.