Cancellous

Cancellous bone, also known as trabecular or spongy bone, is one of the two main types of osseous tissue in the skeleton. It has a porous, lattice-like structure that forms the interior of bones and is typically found at the ends of long bones, within vertebral bodies, the pelvis, ribs, and the interior of flat bones such as the sternum.

Its architecture consists of a network of trabeculae—thin plates or rods of bone arranged in a three-dimensional mesh. The spaces between the trabeculae are filled with bone marrow and blood vessels. Each trabecula is composed of lamellar bone with osteocytes housed in lacunae and connected by canaliculi, enabling nutrient exchange and signaling.

The porous structure provides a high surface area for mineral exchange, helps to keep the skeleton lightweight, and allows the transmission and distribution of mechanical loads through the bone. The marrow spaces within cancellous bone store hematopoietic tissue in children and become increasingly yellow marrow with age; these spaces are also a site of hematopoiesis in adults to a lesser extent.

Remodeling of cancellous bone occurs relatively rapidly compared with cortical bone, driven by osteoclasts and osteoblasts at the endosteal surface. This remodeling enables adaptation to mechanical stresses and contributes to mineral homeostasis.

Clinical relevance includes the susceptibility of cancellous bone to loss in osteoporosis, where reduced trabecular density and connectivity increase fracture risk, especially in vertebrae and the hip. Imaging and bone density measurements often reflect changes in trabecular architecture, and treatments for osteoporosis aim to preserve or restore cancellous bone structure.