Question

multiple choice 2 points
which of the following is the correct sequence of events in the healing of a bone fracture?
soft callus formation \\(\
ightarrow\\) hard callus formation \\(\
ightarrow\\) hematoma formation \\(\
ightarrow\\) bone remodeling
hematoma formation \\(\
ightarrow\\) hard callus formation \\(\
ightarrow\\) soft callus formation \\(\
ightarrow\\) bone remodeling
bone remodeling \\(\
ightarrow\\) soft callus formation \\(\
ightarrow\\) hard callus formation \\(\
ightarrow\\) hematoma formation
hematoma formation \\(\
ightarrow\\) soft callus formation \\(\
ightarrow\\) hard callus formation \\(\
ightarrow\\) bone remodeling
bone remodeling \\(\
ightarrow\\) hard callus formation \\(\
ightarrow\\) soft callus formation \\(\
ightarrow\\) hematoma formation

Explanation:

Identify the physiological stages of bone healing

Bone fracture repair is a highly regulated physiological process that occurs in four distinct, sequential stages:

1. Hematoma formation: Immediately after a fracture, blood vessels rupture, forming a blood clot (hematoma) at the injury site to stabilize the area.
2. Soft callus formation: Fibroblasts and osteoprogenitor cells invade the hematoma, producing collagen fibers and fibrocartilage to form a temporary soft (fibrocartilaginous) callus.
3. Hard callus formation: Osteoblasts replace the fibrocartilage with spongy bone, converting the soft callus into a hard (bony) callus.
4. Bone remodeling: Over several months, osteoclasts and osteoblasts remodel the bony callus, replacing spongy bone with compact bone to restore the bone's original shape and strength.

Evaluate the given options

Let us analyze the sequence presented in each option:

• Option 1: Starts with soft callus formation. This is incorrect because hematoma formation must occur first.
• Option 2: Hematoma formation \(

ightarrow\) hard callus formation \(
ightarrow\) soft callus formation. This is incorrect because soft callus formation must precede hard callus formation.

• Option 3: Starts with bone remodeling. This is incorrect because remodeling is the final stage of healing.
• Option 4: Hematoma formation \(

ightarrow\) soft callus formation \(
ightarrow\) hard callus formation \(
ightarrow\) bone remodeling. This matches the correct physiological sequence.

• Option 5: Starts with bone remodeling. This is incorrect.

Answer:

• (A) Soft callus formation \(

ightarrow\) hard callus formation \(
ightarrow\) hematoma formation \(
ightarrow\) bone remodeling

• (B) Hematoma formation \(

ightarrow\) hard callus formation \(
ightarrow\) soft callus formation \(
ightarrow\) bone remodeling

• (C) Bone remodeling \(

ightarrow\) soft callus formation \(
ightarrow\) hard callus formation \(
ightarrow\) hematoma formation

• **(D) Hematoma formation \(

ightarrow\) soft callus formation \(
ightarrow\) hard callus formation \(
ightarrow\) bone remodeling (Correct answer)**

• (E) Bone remodeling \(

ightarrow\) hard callus formation \(
ightarrow\) soft callus formation \(
ightarrow\) hematoma formation