Final answer:
A Colles fracture is caused by falling onto an outstretched hand, especially in older adults with osteoporosis or during high-speed falls in proactive activities.
Step-by-step explanation:
Grandma Jean suffered a Colles fracture, which is primarily caused by falling onto an outstretched hand. This type of wrist fracture typically happens when someone tries to stop a fall by reaching out with their hand, leading to a complete transverse fracture across the distal radius. This injury results in a posterior and superior displacement of the distal radius fragment, creating a visible deformity that resembles a dinner fork bend of the forearm.
Colles fractures are especially common in older individuals with osteoporosis, as their bones are more prone to breaking. In younger people, it frequently occurs due to high-speed falls during activities like snowboarding or skating. The necessity of surgery for a Colles fracture depends on the severity of the fracture and whether it has led to misalignment of the bone fragments or involvement of the joint surface.