Colles' wrist fracture. Frontal X-ray of the hand and wrist bones of a patient with a type of wrist fracture known as a Colles' fracture. The fractured area is at lower centre. The ends of the arm bones (ulna and radius) have been broken at the wrist, having been displaced up and over the bones of the hand. This type of fracture is usually caused by using the hand to break a fall. It is common in the elderly, whose bones have been weakened by osteoporosis. Treatment involves the surgical repositioning of the bones followed by immobilisation in a cast. The injury slightly increases the risk of developing arthritis in the joint.