Tunica vaginalis for correcting penile chordee in a rabbit model: is there a difference in flap versus graft?

We compared tunica vaginalis applied as a flap versus a graft for covering defects in the ventral tunica albuginea in a rabbit model.

We used 18 New Zealand White rabbits in the study. The urethra was mobilized off of the corpus cavernosum. A defect was created in the ventral aspect of the tunica albuginea by excising a 1 x 0.5 cm. rectangular area. The defect was covered by the testicular surface of tunica vaginalis as a vascularized flap in 9 animals and as a graft in 9. At 2, 6 and 12-week intervals 3 animals per group were sacrificed. Transverse sections of the penis at the repair site were stained with hematoxylin and eosin, and Masson's trichrome for microscopy.

Autopsy revealed no contracture in any of the tunica vaginalis flaps. In contrast, the tunica vaginalis grafts had contracted by a mean of 22% (range 20% to 25%) at 2, 38% (range 30% to 44%) at 6 and 42% (range 38% to 48%) at 12 weeks. Microscopic examination of the tunica vaginalis flaps showed evidence of an intact blood supply and viable cremasteric muscle layer but no evidence of necrosis. Collagen remodeling and maturation was noted at 12 weeks. In tunica vaginalis grafts there was evidence of necrosis of all tunica vaginalis layers at 2 weeks with granulation tissue and active fibrosis at the periphery. At 6 and 12 weeks most necrotic tissue was replaced by fibrosis. Osseous metaplasia was identified in 1 graft at 12 weeks.

The optimal use of tunica vaginalis for correction of chordee is as a flap rather than as a free graft. Grafts were associated with significant necrosis and contracture, of which neither was associated with flaps.