How long does a broken 4th metacarpal generally take to heal?

Depends on the break. It depends on the location of the fracture and how much comminution there is. Hand fractures are a little different from other fractures, as non-healing is much less of a problem than stiffness. X-rays typically lag behind what is really going on, so once the fracture is non-painful when tapped upon, it is healed (usually 2 weeks in children and 3-4 weeks in adults.) avoid stiffness!