The solo student pilot reported that while taxiing to the runway for departure, he attempted to adjust the seat to get a "better view". When he released the seat latch, the seat moved aft, and he was unable to reach the rudder pedals or brake pedals with his feet. He added that he was unable to lean forward because his seat belt was secured. Subsequently, the airplane veered left, he pulled the engine throttle to idle, but the airplane exited the taxiway into a ditch and struck a wire fence.
The airplane sustained substantial damage to the left wing and right horizontal stabilizer.
The student pilot reported that there were no preaccident mechanical failures or malfunctions with the airplane that would have precluded normal operation.