trabecular

Trabecular bone, also called cancellous or spongy bone, consists of thin interconnecting plates and rods (trabeculae) arranged along lines of mechanical stress, forming a honeycomb-like structure that is highly porous (50-90% porosity) compared to dense cortical bone (5-10% porosity). It has a much higher surface area-to-volume ratio, making it more metabolically active and responsive to hormonal changes (e.g., estrogen, PTH) and remodeling than cortical bone. This is why trabecular-rich sites like the vertebral bodies, femoral neck, and distal radius are the earliest and most severely affected sites in osteoporosis, leading to characteristic fragility fractures (vertebral compression fractures, Colles' fractures, hip fractures). On histology, trabecular bone shows interconnected bony spicules with marrow spaces containing hematopoietic or fatty marrow. The term also applies to non-skeletal structures: trabeculae carneae are irregular muscular ridges in the ventricles of the heart; splenic trabeculae are fibrous connective tissue septae extending from the capsule that carry blood vessels and support the splenic parenchyma; and trabecular meshwork in the eye is the spongy tissue at the iridocorneal angle responsible for aqueous humor drainage—dysfunction here causes open-angle glaucoma due to increased intraocular pressure. Clinically, DEXA scans assess bone mineral density, which heavily reflects trabecular bone loss in osteoporosis, and trabecular bone score (TBS) is an emerging tool to assess microarchitecture. Understanding trabecular vs cortical bone physiology is essential for understanding osteoporosis, Paget's disease, and fracture patterns.