INTRODUCTION
The number of soft tissue filler injections performed in the United States continues to increase. According to the annual report of the American Society of Plastic Surgery, 2,676,907 soft tissue filler injections (unspecified) were performed in 2018, which represents a 3-fold increase compared to the year 2000.1 Recent studies have provided evidence that the number of soft tissue filler associated cases of blindness has concomitantly increased.2 Between 2015 and 2018, 48 cases were published,2 compared to 98 reported cases between 1906 and 2015.3 Cho et al. simulated the underlying pathophysiologic mechanism of this catastrophic adverse event by using a perfused cadaveric model.4 They were able to identify an association between the intraarterial application of the filler material to the supratrochlear artery and the embolization of retinal arteries.4
The retinal arteries are linked to a vast network of collateral arteries forming anastomoses with the contralateral side and connecting the external carotid artery circulation with the internal carotid artery.5 A recent anatomic report provided evidence that the facial arteries vary highly between individuals and even between the sides of the face in the same person (2-dimensional variation). However, it was shown that the variation in depth (3-dimensional variation) is less, indicating that facial arteries respect their fascial planes but vary within that plane.5 This high variability in the location of the facial arterial vasculature results in the potential for accidental intraarterial injections for even the most expert injectors.6
Soft tissue filler injections are performed using either sharp tip needles or blunt tip cannulas. Previous studies have shown that injecting with a needle oriented perpendicular to (in contact with) the bony surface distributes the filler material into all fascial planes, whereas injecting with a cannula parallel to the bone surface positions product solely in the inserted plane.7,8 These 2 studies reveal that the injector also contributes to safety in soft tissue filler injections as the product can change planes during needle injections, potentially leading to intraarterial application of the product.
The retinal arteries are linked to a vast network of collateral arteries forming anastomoses with the contralateral side and connecting the external carotid artery circulation with the internal carotid artery.5 A recent anatomic report provided evidence that the facial arteries vary highly between individuals and even between the sides of the face in the same person (2-dimensional variation). However, it was shown that the variation in depth (3-dimensional variation) is less, indicating that facial arteries respect their fascial planes but vary within that plane.5 This high variability in the location of the facial arterial vasculature results in the potential for accidental intraarterial injections for even the most expert injectors.6
Soft tissue filler injections are performed using either sharp tip needles or blunt tip cannulas. Previous studies have shown that injecting with a needle oriented perpendicular to (in contact with) the bony surface distributes the filler material into all fascial planes, whereas injecting with a cannula parallel to the bone surface positions product solely in the inserted plane.7,8 These 2 studies reveal that the injector also contributes to safety in soft tissue filler injections as the product can change planes during needle injections, potentially leading to intraarterial application of the product.
