An employee had just finished helping a co-worker secure a 9-foot section of wire trough, that was secured to a cross member that was elevated approximately 11.5 feet above the concrete floor. The employee was descending a fiberglass step ladder when the ladder shifted from beneath him in one quick movement, causing him to lose his balance and fall approximately 5 feet. The employee suffered an L-1 lumbar fracture and was admitted to the hospital.