Editing Bone fracture (section)

==Pathophysiology==
{{Main|Bone healing}}
[[File:613 Stages of Fracture Repair.jpg|thumb|500px|upright=0.4|Stages in Fracture Repair: The healing of a bone fracture follows a series of progressive steps: (a) A fracture hematoma forms. (b) Internal and external calli form. (c) Cartilage of the calli is replaced by trabecular bone. (d) Remodeling occurs.]]
The natural process of healing a fracture starts when the injured bone and surrounding tissues bleed, forming a fracture [[hematoma]]. The [[clotting|blood coagulates]] to form a blood [[clot]] situated between the broken fragments.<ref>{{Cite web |last=Silva |first=Joana Cavaco |date=2018-07-11 |others=William Morrison, M.D. (medical reviewer) |title=Bone fracture repair: Procedures, risks, and healing time |url=https://www.medicalnewstoday.com/articles/322419 |access-date=2022-04-21 |website=[[Medical News Today]] |language=en |archive-date=23 March 2022 |archive-url=https://web.archive.org/web/20220323202620/https://www.medicalnewstoday.com/articles/322419 |url-status=live }}</ref> Within a few days, [[angiogenesis|blood vessels grow]] into the jelly-like matrix of the blood clot. The new blood vessels bring [[white blood cell|phagocyte]]s to the area, which gradually removes the non-viable material. The blood vessels also bring [[fibroblast]]s in the walls of the vessels and these multiply and produce [[collagen]] fibres. In this way, the blood clot is replaced by a matrix of collagen. Collagen's rubbery consistency allows bone fragments to move only a small amount unless severe or persistent force is applied.{{cn|date=June 2021}}

At this stage, some of the fibroblasts begin to lay down [[bone matrix]] in the form of collagen monomers. These monomers spontaneously assemble to form the bone matrix, for which bone crystals ([[calcium hydroxyapatite]]) are deposited in amongst, in the form of insoluble [[crystal]]s. This mineralization of the collagen matrix stiffens it and transforms it into bone. In fact, bone ''is'' a mineralized collagen matrix; if the mineral is dissolved out of bone, it becomes rubbery. Healing bone [[Fibrocartilage callus|callus]] on average is sufficiently mineralized to show up on [[X-ray]] within 6 weeks in adults and less in children. This initial "woven" bone does not have the strong mechanical properties of mature bone. By a process of remodelling, the woven bone is replaced by mature "lamellar" bone. The whole process may take up to 18 months, but in adults, the strength of the healing bone is usually 80% of normal by 3 months after the injury.{{cn|date=June 2021}}

Several factors may help or hinder the bone healing process. For example, [[tobacco]] smoking hinders the process of bone healing,<ref name="pmid20303894">{{cite journal |doi=10.1016/j.surge.2009.10.014 |pmid=20303894 |title=The effects of smoking on fracture healing |journal=The Surgeon |volume=8 |issue=2 |pages=111–6 |year=2010 |last1=Sloan |first1=A. |last2=Hussain |first2=I. |last3=Maqsood |first3=M. |last4=Eremin |first4=O. |last5=El-Sheemy |first5=M. }}</ref> and adequate nutrition (including [[calcium]] intake) will help the bone healing process. Weight-bearing stress on bone, after the bone has healed sufficiently to bear the weight, also builds bone strength.

Although there are theoretical concerns about [[NSAIDs]] slowing the rate of healing, there is not enough evidence to warrant withholding the use of this type analgesic in simple fractures.<ref>{{cite journal |doi=10.1100/2012/606404 |pmid=22272177 |pmc=3259713 |title=Do Nonsteroidal Anti-Inflammatory Drugs Affect Bone Healing? A Critical Analysis |journal=The Scientific World Journal |volume=2012 |pages=1–14 |year=2012 |last1=Pountos |first1=Ippokratis |last2=Georgouli |first2=Theodora |last3=Calori |first3=Giorgio M. |last4=Giannoudis |first4=Peter V. |doi-access=free }}</ref>

===Effects of smoking===
{{Main|Health effects of tobacco}}
Smokers generally have lower bone density than non-smokers, so they have a much higher risk of fractures. There is also evidence that smoking delays bone healing.<ref>{{cite journal |doi=10.1007/s00198-004-1640-3 |pmid=15175845 |title=Smoking and fracture risk: A meta-analysis |journal=Osteoporosis International |volume=16 |issue=2 |pages=155–62 |year=2004 |last1=Kanis |first1=J. A. |last2=Johnell |first2=O. |last3=Oden |first3=A. |last4=Johansson |first4=H. |last5=De Laet |first5=C. |last6=Eisman |first6=J. A. |last7=Fujiwara |first7=S. |last8=Kroger |first8=H. |last9=McCloskey |first9=E. V. |last10=Mellstrom |first10=D. |last11=Melton |first11=L. J. |last12=Pols |first12=H. |last13=Reeve |first13=J. |last14=Silman |first14=A. |last15=Tenenhouse |first15=A. |s2cid=19890259 }}</ref>