The influence of flange compliance and mechanical loading on the tissue response to percutaneous devices

The failure of most percutaneous devices (PD) is caused by infection initiated by a lack of a tight seal at the skin-device interface. This interface can be disrupted by both extrinsic and intrinsic forces. Many stress reduction methods have been proposed, the most common being the application of a subcutaneous flange. It is widely believed that the bending compliance of the flange plays a significant role in the success or failure of a PD. A study was conducted to observe the effect of flange compliance on local host response in both a functional and nonfunctional setting. Two PDs having flanges with different bending rigidities were implanted percutaneously in goats (n = 8). After a healing period of 2 weeks, half of these devices were externally stimulated with a random load. All the implants were retrieved after 4 weeks and evaluated histologically. The tissue capsule was significantly thicker and the incidence of severe fibrosis and/or necrosis was higher at the flange rim of the functional implants, irrespective of flange compliance. The more compliant devices were encapsulated with a thick fibrous capsule more frequently than the less compliant ones, irrespective of functional status. The more compliant devices also had a greater incidence of foreign body giant cells in the corner region and elicited severe acute inflammation at the corner and top of the flange more frequently than the less compliant implants.(ABSTRACT TRUNCATED AT 250 WORDS)