Rørbein

Rørbein, in Norwegian, refers to the long bones of the limbs. These bones are tubular and characterized by a hollow shaft that contains a medullary cavity. The structure provides a strong, lightweight framework for movement and load bearing. Common examples include the femur, tibia, humerus, radius, ulna, and the metacarpals and metatarsals.

Anatomically, a rørbein consists of a diaphysis (the shaft) that is primarily compact bone surrounding the medullary cavity, which houses bone marrow. The ends of the bone are the epiphyses, which contain more spongy (trabecular) bone and contribute to joint surfaces. The outer surface is covered by the periosteum, rich in nerves and blood vessels, while the inner surface lining the cavity is the endosteum. Blood supply reaches the bone through nutrient arteries entering via a nutrient foramen, with additional vessels supplied by periosteal arteries. The cortical bone forms osteons, contributing to strength and resistance to bending.

Growth and remodeling are key features. Long bones grow in length at the epiphyseal plates during development and remodel throughout life through coordinated activity of osteoblasts and osteoclasts, balancing bone formation and resorption. In children, red bone marrow is active for hematopoiesis; in adults, much of the marrow space is yellow marrow composed of fat.

Clinical relevance includes fractures of rørbein, which can vary from hairline to complex injuries. Conditions such as osteoporosis and osteomyelitis can affect these bones, influencing stability and healing.