A broken bone heals
Bone heals by making new bone rather than a scar. A common break is at the lower end of the radius, just above the wrist, from a fall onto an outstretched hand.
X-ray of a broken lower end of the radius from the front, with lines that measure the tilt of its joint surfaceWikimedia Commons, Mikael Häggström from an original by Lucien Monfils, CC BY-SA 3.0 (Radial inclination of distal radius fracture.jpg)
Healing runs in stages. Blood from torn vessels clots around the broken ends. Within days, cells move in and build a soft callus of cartilage and fibrous tissue that bridges the gap. Over the next weeks bone replaces it, as a hard callus, and most breaks in adults are firm after six to twelve weeks.
Over the following months and years the bone is remodelled. The callus is trimmed back until the bone has nearly its old shape. A cast or splint keeps the ends lined up and still while this happens, since movement between them slows healing.
Sources
- Susan Standring (ed.), Gray's Anatomy, 42nd ed. (2020), chapter on bone and cartilage.
- J. Gordon Betts and others, Anatomy and Physiology (Houston: OpenStax, 2013), section 6.5.
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