🩹 Skeletal System Lesson

PIGS: four bone fracture types

Not all fractures look or behave the same — the mechanism of injury directly determines the fracture pattern, and one specific pattern raises serious clinical concerns in children.

Pathologic

Impacted

Greenstick

Spiral

📖 Full Breakdown

Four fracture types, each tied to a specific mechanism and clinical significance

One of these fracture types can be a red flag for child abuse — knowing this connection has real clinical and legal weight.

Pathologic fractures

Through diseased bone

Occur from minor trauma because the underlying bone is already weakened by disease — osteoporosis or cancer are common causes. The fracture itself may be the first sign that reveals the underlying disease.

Impacted fractures

Compression force

Bone fragments are driven into each other, typically from a compressive force rather than a twisting or bending force.

Greenstick fractures

Incomplete break — children only

One side of the bone bends while the other breaks, similar to how green (living, flexible) wood bends and splinters rather than snapping cleanly — this pattern occurs specifically in children because their bones are more flexible than adult bone.

Spiral fractures

Twisting force

Common in sports injuries, but also clinically and forensically important as a potential indicator of abuse in children, since this fracture pattern can result from someone forcibly twisting a child's limb.

🩺 Clinical / Exam Application

A young child is brought to the emergency room with a spiral fracture of the arm, and the caregiver's explanation of how the injury occurred doesn't match a plausible twisting mechanism. Because spiral fractures specifically result from twisting forces, and this particular mechanism is less common in typical childhood accidents (like falls, which more often cause other fracture types), this fracture pattern raises a clinical red flag prompting further investigation for possible non-accidental trauma — a fracture type doubling as a forensic clue.

⚠️ Exam Alert

The connection between spiral fractures and potential child abuse is a frequently tested clinical and ethical topic — know that this specific fracture PATTERN (not fractures in general) is what raises particular concern, due to the twisting mechanism required to produce it.

🚧 Common Trap

Don't assume greenstick fractures can occur in adults. This fracture type specifically requires the increased bone flexibility found in children — adult bone, being less flexible, is far more likely to break completely rather than bend-and-crack in this characteristic incomplete pattern.

✅ Quick Check

Why does a spiral fracture in a young child sometimes prompt additional investigation beyond just treating the injury itself?

📝 Exam Prep

Common Exam Questions

❓ What are four clinically important fracture types?

✅ Pathologic fractures occur through diseased bone from minor trauma. Impacted fractures involve fragments driven into each other from compression. Greenstick fractures are incomplete breaks seen only in children. Spiral fractures result from twisting force.

❓ Why are greenstick fractures seen only in children?

✅ Children's bones are more flexible than adult bone, allowing one side of the bone to bend while the other cracks, rather than breaking completely — similar to how green (living) wood bends and splinters rather than snapping cleanly.