What can cause a fracture of the first or seventh rib?

The plaintiff was a demolition worker employed by a subcontractor for the demolition works, and the second defendant was the main contractor for the fitting-out works of the unit. In the afternoon of that day, the plaintiff was working for the first defendant. He put the dismantled mud and waste into an environmental protection recycling bucket near the underground gate of the unit. At that time, he was standing on the bucket full of mud and waste. The distance between the bucket and the ground is more than 6 feet. During work, fell from the side of the bucket to the ground and was injured. The plaintiff was subsequently granted legal aid to assist him in recovering employees' compensation and common law personal injury compensation for bodily injuries caused by the accident of the right thoracic pneumothorax.

Injuries were as follows:
(1) Fracture of the first and seventh ribs of the right thorax;
(2) Right thoracic pneumothorax;
(3) collapsed lung;
(4) Abrasion on the right elbow;
(5) right shoulder injury;
(6) right hip injury; and
(7) Injured right knee.