The commonest cause of an obliterative stricture of the membranous urethra is -
Commonest cause of stricture in posterior urethra → Trauma with fracture pelvis
Commonest cause of stricture in anterior urethra → Straddle injuries (direct trauma to the perineal region).
Fall-astride injury
Road-traffic accident with fracture pelvis and rupture urethra
Prolonged catheterization
Gonococcal infection