How often is compact bone replaced?

How often is compact bone replaced?

• A. Every 5 years
• B. Every 10 years
• C. Every 15 years
• D. Approximately every 10 years

Answer: (D)

Compact bone is not static; it undergoes continual remodeling, where old bone is removed by osteoclasts and new bone is laid down by osteoblasts to form fresh osteons. In adults, the turnover of cortical (compact) bone is relatively slow compared with trabecular bone, so renewing the entire mass of compact bone across the skeleton takes a long time—roughly a decade. That’s why the best answer uses “approximately,” acknowledging some variation among individuals and bones. The other options imply a fixed, shorter or longer interval that doesn’t match the typical decadal rate of cortical bone renewal, given that remodeling occurs everywhere over many years rather than on a strict schedule.

Compact bone is not static; it undergoes continual remodeling, where old bone is removed by osteoclasts and new bone is laid down by osteoblasts to form fresh osteons. In adults, the turnover of cortical (compact) bone is relatively slow compared with trabecular bone, so renewing the entire mass of compact bone across the skeleton takes a long time—roughly a decade. That’s why the best answer uses “approximately,” acknowledging some variation among individuals and bones. The other options imply a fixed, shorter or longer interval that doesn’t match the typical decadal rate of cortical bone renewal, given that remodeling occurs everywhere over many years rather than on a strict schedule.