Page 44 - Orthopedic Casting Manual

Review - Stages of Bone Healing

The bone healing process can be divided into four over lapping stages:
inflammation, soft callus formation, hard callus formation, and remodeling.
Each stage is characterized by distinct cellular and molecular events that

ul timately lead to the restoration of the bone's structure and function.

Bones are essential structures of the human body, providing suppor t, protection,

and facilitating movement. Despite their remar kable strength, bones can
sometimes break or fracture due to trauma, repetitive stress, or under lying
medical conditions. Understanding the bone healing process is crucial for
heal thcare professionals and patients alike, as it infor ms the appropriate

management of bone injuries and ensures optimal recover y.

INFLAMMATION
Immediatel y after a bone injur y, the bod y initiates an inflammator y response. Blood vessels at the fracture site rupture, le ading
to the for mation of a hematoma (a blood clot). The hematoma st abilizes the fracture site and ser ves as a provisional matr ix for
the migration of cells invol ved in bone rep air. Inflammator y cells, such as white blood cells, infil trate the injur y site to remove
de ad tissue and prevent infection. Additionall y, cells c alled cy tokines and growth factors are rele ased, which help recruit cells
necessar y for bone he aling.

Soft Callus Formation
Dur ing the soft c allus for mation st age, specialized cells c alled chondroblasts produce a soft, fibroc ar tilaginous matr ix that
br idges the gap bet ween the broken bone ends. This soft c allus, composed pr imar il y of collagen, provides initial st abilit y and
ser ves as a sc affold for new bone for mation. The soft c allus also plays a crucial role in re-est ablishing the blood suppl y to the
fracture site, as new blood vessels begin to infil trate the he aling tissue.

Hard Callus Formation
As the he aling process progresses, the soft c allus is graduall y replaced by a hard c allus made of woven bone. Osteoblasts, the
cells responsible for new bone for mation, lay down a mineralized matr ix that hardens the c allus. This hard c allus provides
incre ased strength and r igidit y to the fracture site, fur ther st abilizing the broken bone ends. The hard c allus st age c an last
several weeks to months, depending on the sever it y of the injur y and individual factors such as age, nutr ition, and overall he al th.

Remolding
The final st age of bone he aling is remodeling, dur ing which the hard c allus is transfor med into mature, lamellar bone. This
process is facilit ated by osteoclasts, cells that bre ak down and remove excess bone tissue, and osteoblasts, which continue to
deposit new bone. Remodeling c an t ake several months to ye ars, depending on the size and complexit y of the fracture. The end
resul t is a full y restored bone that closel y resembles its pre-injur y structure and function.