What condition do bones not fuse together?

Bones do not fuse together in conditions such as osteogenesis imperfecta, a genetic disorder that affects collagen production, leading to brittle bones that can fracture easily. Additionally, certain types of Arthritis, like rheumatoid arthritis, can prevent proper bone fusion due to inflammation and joint damage. In young children, the presence of growth plates also keeps bones from fusing until skeletal maturity is reached.