摘要

Objectives: The occurrence of ‘retrograde flow along the cannula/needle tract’ during filler injections has not been extensively addressed. The retrograde flow phenomenon can be described as follows: as the cannula creates a tract in the tissue, filler can spread within this potential space. This is because filler material tends to spread towards areas of least resistance. According to rheology, the extent of flow depends on the filler's cohesivity and the applied compression force. Conclusion: In conclusion, the retrograde phenomenon is a unidirectional lateral dispersion of filler material along cannula/needle tract where is the area of least resistance. The primary factors influencing this phenomenon are filler cohesivity and compression force applied during injection. Ultrasound can help assessing the amount of Back-flow and expecting the proper outcome.