Ans to this q
Reading File
Finding Sources
Reading File
Answer: 2. Movement at fracture site
Correct Answer: Option 2 — Movement at fracture site
Explanation
Callus formation is the hallmark of indirect (secondary) fracture healing, which occurs via endochondral ossification. The key driver of callus production is interfragmentary movement (IFM) — i.e., micromotion at the fracture site.
The mechanism:
- Micromotion at the fracture gap causes a greater inflammatory response and stimulates mesenchymal cells from surrounding soft tissues to migrate to the fracture ends.
- These cells differentiate into chondrocytes, forming cartilage in the well-vascularized granulation tissue.
- This cartilage scaffold undergoes endochondral ossification, forming the external bridging callus.
- The size of the callus is directly proportional to the magnitude of interfragmentary motion — more movement → larger callus.
"A degree of axial micromotion at the fracture site is desirable and can promote callus formation... applying cyclic interfragmentary micromotion for short periods of time leads to a larger area of callus formation compared with those fractures that are rigidly fixed." — Rockwood and Green's Fractures in Adults, 10th ed.
Why the other options are wrong:
| Option | Effect on Healing |
|---|---|
| Rigid immobilization | Suppresses callus — promotes primary (direct) cortical healing with cutting cones; excessively rigid fixation can inhibit external callus formation (Goodship et al.) |
| Compression plating | Also promotes primary/direct bone healing without callus — the goal of compression plating is to achieve absolute stability and eliminate interfragmentary motion |
| Intraosseous (intramedullary) nailing | Allows some micromotion and can form callus, but is not the best answer here; the question asks what promotes callus, and movement is the direct stimulus |
Bottom line: Callus formation requires relative stability with some interfragmentary movement (e.g., functional bracing, external fixation with some flexibility). Rigid fixation (compression plates, screws achieving absolute stability) bypasses callus and heals by direct cortical remodeling.
This is a shared conversation. Sign in to Orris to start your own chat.