Evaluation of the wound healing potential in human beings from the subcutaneous insertion of expanded polytetrafluoroethylene tubes.

Subcutaneous insertion of expanded polytetrafluoroethylene tubes with local anesthesia constitutes a minimally invasive model permitting quantitative and qualitative studies of the wound healing potential in human beings. Light and electron microscopic examination of these implants in rats showed a normally appearing granulation tissue. The amount of hydroxyproline accumulated in the expanded polytetrafluoroethylene tubes may be assayed and converted to collagen content. In 28 surgical patients, the collagen content increased from 6.6 microg/cm (interquartile range: 5.1 to 9.9) after 5 days to 12.4 microg/cm (7.1 to 16.8) after 10 days (p < 0.05). The median ratio between the higher and lower collagen amount measured in two expanded polytetrafluoroethylene tubes inserted for an identical period within the same patient was 1.25 (1.10 to 1.81). This variability ratio was not related to the amount of collagen accumulated or the duration of implantation. There was a tendency for higher collagen amounts in the middle section than in the ends of the expanded polytetrafluoroethylene tubes, with a median ratio between the two sections equaling 1.12 (0.96 to 1.58); (p > 0.05). No infectious or hemorrhagic complications from the insertion occurred in any of the patients. Increments of collagen deposition with time may be easily assessed by this expanded polytetrafluoroethylene tube model, which is inexpensive and has high patient acceptance. Measurement variability was encountered, which has to be taken into account when designing clinical trials.