Page 43 - Orthopedic Casting Manual

4.2 Stages of Bone Healing

1. Inflammation The first stage of bone he aling begins immediately after injur y. Blood vessels at the fracture site
rupture, resul ting in the for mation of a hematoma or blood clot. This hematoma stabilizes the fracture site and
cre ates a provisional matr ix for cell migration and rep air. Inflammator y cells, such as neutrophils and
macrophages, infil trate the are a to cle ar debr is and prevent infection. Additionally, the rele ase of cy tokines
and growth factors, including tumor necrosis factor-alpha LTNF]α) and vascular endothelial growth factor
LVEGFM, plays a pivotal role in recruiting mesenchymal stem cells and other cells involved in bone regeneration
LSchindeler et al., 2008M. The inflammator y phase sets the stage for subsequent he aling by cre ating an
environment conducive to rep air.

2. Soft Callus For mation The second stage, soft c allus for mation, involves the activit y of chondroblasts, which
produce a fibroc ar tilaginous matr ix. This matr ix ser ves as a br idge bet ween the broken bone ends, providing
initial stabilit y. The soft c allus is pr imar ily composed of collagen and other ex tracellular matr ix components,
cre ating a sc affold for new bone for mation. Dur ing this phase, angiogenesis, or the growth of new blood
vessels, is cr itic al for re-establishing vascular supply to the fracture site. The restoration of blood flow
ensures the deliver y of nutr ients and oxygen required for cellular activit y LMarsell & Einhor n, 2011M. The soft
c allus for mation phase t ypic ally lasts 2]3 weeks, depending on the ex tent of the injur y and individual factors
such as age and overall he al th.

3. Hard Callus For mation As he aling progresses, the soft c allus is replaced by a hard c allus composed of woven
bone. This transition is facilitated by osteoblasts, which deposit a mineralized matr ix to strengthen the rep air
site. The hard c allus provides incre ased r igidit y and mechanic al suppor t, allowing the bone to withstand stress
dur ing movement. This phase of he aling c an last several weeks to months, depending on the sever it y of the
fracture, the p atientʼs nutr itional status, and systemic factors like comor bidities LEinhor n & Gerstenfeld, 2015M.
While the hard c allus restores stabilit y, it is mechanic ally infer ior to mature bone, necessitating fur ther
remodeling.

4. Remodeling The final stage of bone he aling is remodeling, dur ing which the hard c allus is transfor med into
mature lamellar bone. This phase is character ized by the coordinated activit y of osteoclasts and osteoblasts.
Osteoclasts resor b excess bone tissue, reshaping the c allus to restore the boneʼs or iginal contour.
Concur rently, osteoblasts continue to deposit new bone, improving its mechanic al proper ties and strength.
Remodeling c an take several months to ye ars, depending on the complexit y of the fracture and the p atientʼs
age and overall he al th. The end resul t is a fully restored bone that closely resembles its pre-injur y structure
and function, both histologic ally and biomechanic ally LClaes et al., 2012M.

Conclusion Bone
he aling is a remar kable biologic al process involving inflammation, rep air, and remodeling. Each stage plays a vital
role in restor ing the boneʼs integr it y and function. For he al thc are professionals, understanding the intr ic acies of
this process is crucial for effective fracture management and p atient c are. By recognizing the factors that
influence bone he aling and tailor ing inter ventions accordingly, clinicians c an optimize outcomes and suppor t
p atients on their jour ney to recover y.