A stereological analysis of fibrosis and inflammatory reaction induced by four different synthetic slings.

Objectives: To analyse quantitatively, using stereological methods, the density of the collagen fibres induced by four types of sling materials, and verify by a histopathological analysis the corresponding inflammatory reaction, as fibrosis secondary to sling implantation is considered responsible for restoring urethral support and re-establishing continence in women with stress urinary incontinence, and new synthetic materials that promote adequate fibrosis with the least intensity and duration have been proposed to substitute the aponeurotic sling.

Materials And Methods: The study comprised 70 isogenic white Wistar rats divided into three groups: group A (30 rats) had 8 x 4 mm strips of silicone and porcine small intestine submucosa (SIS) implanted in the abdominal subcutaneous tissues; group B (30 rats) had 8 x 4 mm strips of polycaprolactone and polylactic acid copolymers and monofilament polypropylene (PLP) implanted the abdominal subcutaneous layer; while a control group of 10 rats had dissection and suturing with 5/0 Nylon in the abdominal subcutaneous layer, as used to fix the strips in the other rats. Picro-Sirius staining was used to assess collagen fibres, and haematoxylin-eosin for the histopathological study. At 7, 30 and 90 days after surgery, 10 rats from each group were killed and assessed.

Results: After 7 days all the materials induced a moderate inflammatory reaction that did not differ from that in the control group. At 30 days there was no difference between the control and polycaprolactone and polylactic acid copolymers, having the least inflammatory reaction. PLP and silicone produced a moderate inflammatory reaction, while the porcine SIS induced a more intense reaction. At 90 days there was a more intense inflammatory reaction in polycaprolactone and polylactic acid copolymers than before but it was less than with PLP and silicone, which again were no different. During this period the inflammatory reaction induced by SIS was greater. The stereological analysis indicated that collagen fibres induced by polycaprolactone and polylactic acid copolymers and PLP were less dense (61% and 65%, respectively), and significantly less than with silicone (85%) and SIS (86%).

Conclusion: PLP was the best nonabsorbable material as it induced a less intense inflammatory reaction than the other tested materials. As porcine SIS was completely absorbed the intense fibrosis induced is useful, as it is exclusively responsible for the urethral support later after surgery.