Hyaline cartilage death is the process by which bone is formed by replacing the dead cartilage. Interstitial growth (happens from within the hyaline cartilage as it is a soft tissue, while bone tissue is hard) is the process by which the bone is elongated (mostly in long bones such as the humerus or during fetal development). When the rate of hyaline cartilage death is faster than the rate of interstitial growth, it means that the bone is being formed quicker than it's being elongated which will lead to a shorter bone. This is one of the problems that leads to some forms of dwarfism.
