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“Is it broken or just fractured?” Fundamentals of bone healing

  
  

 

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All bone breaks are, technically, fractures.  These fractures come in many different flavors:  green stick or complete, simple vs open (bone fragments have come through the skin; "compound" was used in the past to describe this type of fracture), comminuted (multiple fragments), displaced (fragments are separated from where they belong), or angulated.  But, all these fractures share in the process by which they heal.

PHASES OF FRACTURE HEALING

There are three major phases of fracture healing, two of which can be further sub-divided to make a total of five phases:


• 1. Reactive Phase
o i. Initial injury leading to fracture and inflammatory phase
o ii. Granulation tissue formation


• 2. Reparative Phase
o iii. Cartilage Callus formation
o iv. Lamellar bone deposition


• 3. Remodeling Phase
o v. Remodeling to original bone contour

fracture healing resized 600

 


Reactive
After fracture, bleeding occurs at the fracture site and damaged adjacent tissue; blood cells are released into the tissues adjacent to the injury site.  White blood cells come into the site to remove debris and help fight infection.  Soon after fracture, the blood vessels constrict, stopping any further bleeding.   Within a few hours after fracture, the extravascular blood cells form a blood clot, known as a hematoma. All of the cells within the blood clot degenerate and die.   Some of the cells outside of the blood clot, but adjacent to the injury site, also degenerate and die.  These processes stimulate the formation of new blood vessels bringing in oxygen, nutrients, and cells that will lead to the subsequent reparative phase.  Within this same area, the fibroblasts survive and replicate. They form a loose aggregate of cells, interspersed with small blood vessels, known as granulation tissue.

Reparative
Days after fracture, the cells of the periosteum replicate and transform. The periosteal cells proximal to the fracture gap develop into chondroblasts which form hyaline cartilage. The periosteal cells distal to the fracture gap develop into osteoblasts which form woven bone. The fibroblasts within the granulation tissue develop into chondroblasts which also form hyaline cartilage. These two new tissues grow in size until they unite with their counterparts from other parts of the fracture. In combination, this creates a new mass of heterogeneous tissue which is known as the fracture callus. Eventually, the fracture gap is bridged by the hyaline cartilage and woven bone formed in the callus, restoring early stability to the fractured bone.
The next phase is the replacement of the hyaline cartilage and woven bone with lamellar bone. The replacement process is known as endochondral ossification with respect to the hyaline cartilage and bony substitution with respect to the woven bone. Substitution of the woven bone with lamellar bone precedes the substitution of the hyaline cartilage with lamellar bone. The lamellar bone begins forming soon after the collagen matrix of either tissue becomes mineralized. At this point, the mineralized matrix is penetrated by channels, each containing a microvessel and numerous osteoblasts. The osteoblasts form new lamellar bone upon the recently exposed surface of the mineralized matrix. This new lamellar bone is in the form of trabecular bone. Eventually, all of the woven bone and cartilage of the original fracture callus is replaced by trabecular bone, restoring most of the bone's original strength.
Remodeling
The remodeling process substitutes the trabecular bone with compact bone. The trabecular bone is first resorbed by osteoclasts, creating a shallow resorption pit known as a "Howship's lacuna". Then osteoblasts deposit compact bone within the resorption pit. Eventually, the fracture callus is remodeled into a new shape which closely duplicates the bone's original shape and strength. The remodeling phase takes 3 to 5 years depending on factors such as age or general condition.

When a patient breaks a bone, doctors take measures to encourage strong, quick repair. First, the fracture must be in the appropriate position for healing, and then it must be held in position for the period necessary for healing.  This may be possible in a cast or splint, or surgery may be required for reduction (putting the fracture back into position) and for stabilization.  Interventions after fracture may include:


• Closed reduction and immobilizing the break. If necessary, a physician will move bone segments back into place before immobilizing the fracture using a cast or brace.
• Surgery. Some patients may need surgery to reduce and stabilize a fracture — a process that can involve metal plates, screws, pins, or rods.
• Therapy. If a patient is in a cast for a long period of time, he or she may benefit from physical therapy to regain full use of stiff or weak muscles.


Complications of Fracture Healing
The main complications include:
1. Delayed Union: Poor blood supply or infection.
2. Non-Union: Bone loss or wound contamination.
3. Fibrous Union: Improper immobilization
4. Infection

Patients can also take measures to speed healing.
While healing is happening:
• Avoid tobacco products, which can slow the healing process.
• Eat a well balanced diet for the energy and nutrition healing bones need.
• Increase your intake of calcium, which helps build strong bones.
• Only take pain relievers as directed. Certain anti-inflammatory medications can inhibit your body’s ability to heal breaks.
• Get plenty of rest. Your body is working hard to heal and needs recovery time.
• Follow your doctor’s instructions to give yourself every opportunity for successful healing.

-- Lawrence Lee, MD

 

References

  • Brighton, Carl T. and Robert M. Hunt (1986), "Histochemical localization of calcium in the fracture callus with potassium pyroantimonate: possible role of chondrocyte mitochondrial calcium in callus calcification", Journal of Bone and Joint Surgery, 68-A (5): 703-715
  • Brighton, Carl T. and Robert M. Hunt (1991), "Early histologic and ultrastructural changes in medullary fracture callus", Journal of Bone and Joint Surgery, 73-A (6): 832-847
  • Brighton, Carl T. and Robert M. Hunt (1997), "Early histologic and ultrastructural changes in microvessels of periosteal callus", Journal of Orthopaedic Trauma, 11 (4): 244-253
  • Ham, Arthur W. and William R. Harris (1972), "Repair and transplantation of bone", The biochemistry and physiology of bone, New York: Academic Press, p. 337-399
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Comments

Great post! I didn't aware about fracture healing but after read this post many things I come to know. So nicely you represent the whole points and well explained about the complications of fracture healing. Thanks for sharing such an informative post.
Posted @ Wednesday, June 12, 2013 2:37 AM by ZehrCenter @ Hip Joint Pain Treatment
Animal Healing 
 
Really i appreciate the effort you made to share the knowledge.The topic here i found was really effective to the topic which i was researching for a long time. 
 
Posted @ Tuesday, December 10, 2013 4:27 AM by Judy Inman
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