Does size matter? If you want to minimise the foreign body response, minimise the foreign body

The response of bodily tissue to the presence of a foreign body is well understood, with publications too numerous to cite here. Macrophage response culminating in fibroblastic remodelling and subsequent angiogenesis describes in a few words what is a complex cascade in the body’s response to breach of its defences or implantation of a foreign body. A recent publication summarises well the events commonly associated with implantation of synthetic biomaterials. The paper’s abstract starts with the assertion that “The foreign body reaction composed of macrophages and foreign body giant cells is the end-stage response of the inflammatory and wound healing responses following implantation of a medical device, prosthesis, or biomaterial”, which reflects the consensus from the biomaterials community. Also frequently referred to are surface properties of foreign bodies, for which there is again a consensus that the reaction of the body to a foreign material is related to its surface texture. What seems to be less well published is the dependency between size/bulk of implant and extent of response, but this is most likely to be because it’s obvious that the greater the implant the greater and more prolonged the response.
Tissuemed’s assertion is that a foreign body implanted for a purpose should be as small as possible in order for it to perform its function. Comparing a 40micron patch with a polymerising liquid glue (the manufacturer of whom is likely to recommend that up to 2mm depth may be required), it can be concluded that an area of 5cm x 5cm will require 5ml of “foreign body” compared with the equivalent 0.1ml of patch. If both materials work and both provoke the same FB reaction per se, then presumably the lower bulk device has the upper hand.