[Choice of an optimal free graft for replacement urethroplasty in extensive urethral strictures]

Irrespective of the type and properties of a free graft in urethroplasty, survival of the graft depends on blood circulation in the nutrient bed. We made an experimental trial to study engraftment of free grafts of buccal and lingual mucosa on different types of the nutrient bed. Free flaps (78 buccal and 86 lingual mucosa samples) were taken from 52 male Wistar rats (300 to 470 body mass). Grafting was made on different types of nutrient bed - skeletal muscle, subcutaneous fat and penile tunica albuginea. Histological examination of the grafts was made 2, 4, 7 and 14 days after transplantation. The process of engraftment followed all the stages of nonspecific inflammation. The alteration stage (48 hours) is characterized by marked epithelial atrophy, necrosis of most of the cross-striate muscular fibers of the graft, necrotic alterations of the nutrient bed, primarily in the suture area. Excudation and emigration (2-4 days)--by continued necrotic changes with infiltration of the graft with neutrophilic leukocytes, edema of the upper layer stroma and infiltrate extention on the nutrient bed. Proliferation (day 7)--by attenuation of necroinflammatory processes, decline of leukocyte infiltration, formation of blood vessels in the subepithelial base of the graft. Regeneration (day7-14)--by recovery of the epithelial graft layer, development of granulation tissue in the submucosal base. The best engraftment was registered on transplantation on penile tunica albuginea (buccal graft--93.4%, lingual one--88.9%). Successful implantation on the muscle occurred in 90.7% for buccal and 87.9% for lingual grafts. On fat tissue buccal transplant failed in 19, lingua--in 23.89% transplantations. Thus, staging in interaction between different grafts and types of nutrient bed do not depend on characteristics of the bed and graft. Necroinflammatory changes in the buccal graft change for proliferative processes earlier than in the lingual one. Proliferative and regenerative processes develop earlier on penile tunica albuginea. Alteration and exudation are more pronounced on subcutaneous fat.