Fracture healing methods
• Methods of fracture healing
– Indirect fracture healing
– Primary bone healing
– Distraction histogenesis
Bone makes a valiant plan to revisit to its original shape and form after having suffered humiliating fractures thanks to a myriad of incriminating forces. Bone is exclusive in healing itself completely with a tissue that’s indistinguishable from the first tissue hence there’s no scar left. The term bone regeneration and not fracture healing is more specific. Bone is repaired by callus, which may be a new tissue which will develop externally or internally. The external callus envelops opposing ends of bone fragments. An internal callus forms between the bone ends. During the first two days at the fracture site and away from the fracture site, in the deep layer of the periosteum the osteogenic cells proliferate and lift the fibrous layer of the periosteum away from the bone. Marrow cells also proliferate but to a lesser degree. These osteogenic cells differentiate into osteoblasts, which form the bone trabeculae resembling the embryonic tissue. The osteogenic cells lying away from the fracture site due to inadequate vascularity differentiate into chondroblasts and chondrocytes, which form the cartilage. The cartilage is finally converted into the bone by help of endochondral ossification. Internal callus is formed by the mesenchymal cells that convert into the pro-osteoblasts and later to osteoblasts laying down new bone. Remodeling is an activity of osteoclasts, which slowly remove the necrotic bone and make cavities. Osteoblasts line these cavities and lay new bone.
METHODS OF FRACTURE HEALING
A fracture heals by 3 ways , indirect, direct and distraction histogenesis as described by Ilizarov.
INDIRECT FRACTURE HEALING
Indirect fracture healing is the common method of the fracture healing where both the external and internal callus are formed. Hunter has described six stages during this method of healing.
Stage of Impact
This stage extends from the moment of impact until the complete dissipation of energy causing fractures.
Stage of Induction
Following fractures, cells possessing osteogenic potential are activated. Other inducing factors are BMP (bone morphogenic protein), fall in oxygen tension and bioelectric effects.
Stage of Inflammation
In this stage, the disruption of blood supply results in necrosis of the bone ends. There is hemorrhage, cellular proliferation and vascular ingrowths.
Stage of Soft Callus
Here the hematoma is organized with fibrous tissue, cartilage and woven bone. Here Fragments are united with fibrous or the cartilaginous of the tissue or both.
Stage of Hard Callus
Bone fragments are firmly united with bone. If here the immobilization is complete,or the membranous bone healing takes place. If incomplete bone heals by endochondral ossification.
Stage of Remodeling
Here fiber bone is converted to lamellar bone. Medullary canal is reconstituted and callus diameter begins to decrease in size that takes a few of months to several years. However, there’ll be no remodeling of rotational misalignment. Stage of remodeling method of fracture healing is seen in the fractures treated by plaster immobilization and other sorts of external and a few limited internal fixation techniques.
Problems associated with indirect fracture healing
• Less anatomic union.
• Chances of malunion significant.
• Delayed joint mobilization.
• Possibility of fracture disease
|An above elbow cast (Example of indirect fracture healing)|
Primary Bone Healing
Primary Bone Healing type of bone are repair is seen when the bone fragments are anatomically reduced and rigidly fixed. This cannot be obtained by closed methods of fracture treatment but can be achieved by operative reduction and fixation with special techniques of plate and screws. Here ideally no external callus forms and there is no interposing fibrous tissue or cartilage tissue between the fracture sites. The fracture site is bridged by direct haversian remodeling which is nearly an immediate osteon-to-osteon hook-up. The osteoclasts act as cutter heads to get rid of the bone and are within the forefront promptly followed by osteoblasts behind laying down new bone. Primary bone healing type of bone healing usually occurs in fractures treated by AO techniques developed by Swiss association for osteosynthesis.
|Healing of fracture|
Distraction histogenesis may be a recent concept described by Ilizarov. Here bone are repair is induced by the gradual distraction of osteotomic and the fracture after an interval of induction says 5 to 7 days. For osteogenesis to occur the fracture or osteotomy must be stabilized and a slow distraction at the speed of 1 mm per day should tend . For details, see discussion on Ilizarov.
Problems in primary bone healing
• Risk of anesthesia
• Fracture hematoma lost
• Bone healing is slower
• Bone healing is inferior to indirect healing
• There is Difficult to asses the radiological union as no callus is seen
• Implant failure is a possibility
• Needs another operation to remove the implants
• Chances of refracture are high
• Only advantage seems is the good anatomical reduction and the chances of early mobilization
Factors affecting fracture repair
Factors favoring union
• Adequate circulation
• Hormones like growth hormone, parathormone, thyroxin, etc.
• Good nutrition and mineral supplements help passively
• Bioelectric fixation Factors detrimental to union
• Poor circulation
• Segmental fractures
• Soft tissue interposition
• Inadequate and improper immobilization, etc.