Concentric Fracture
Definition
An arc-shaped fracture encircling the impact zone, produced by outer-table bending tension at a distance from the focal impact; always post-dates the radiating fractures of the same impact.
- Type
- Arc or loop-shaped fracture surrounding the impact zone
- Timing relative to radial fractures
- Always secondary, forms after radiating fractures
- Appears in
- Bone (skull), glass, and other brittle materials
- Biomechanics
- Created by outer-layer bending tension at a distance from the focal impact point
Common questions
What is a concentric fracture and where do they show up?+
A concentric fracture is an arc-shaped or circular crack that loops around the point where an impact struck. They appear in both bone (skull) and glass evidence. In bone, they form from tension in the outer layer at some distance from the direct impact point.
How do concentric fractures relate to other impact fractures?+
Concentric fractures always come second in time. They post-date radial fractures (cracks that radiate outward from the impact) of the same impact. This timing helps reconstructionists figure out the sequence of blows.
Can concentric fractures appear in glass evidence?+
Yes. In glass, concentric cracks loop around the impact point and join the radial fractures together. They form after the radiating cracks, on the side where the force arrived.
Related terms
- 3R Rule
- The fracture-analysis mnemonic: Radial cracks form at Right angles to the Reverse (far, non-impact) side of the glass. Applied to the fracture...
- Bearing Surface
- The area of the striking implement that was in contact with the skull at the moment of force transfer; its geometry can...
- Depressed Fracture
- A fracture where the impacted skull segment is driven inward beyond the elastic limit; the geometry of the depression reflects the bearing...
- Diffuse Loading
- Force distributed over a broad contact area (as from a fall onto a flat surface or a broad-surface blow); produces a broader...
- Focal Loading
- Force concentrated on a small contact area of the skull surface (as from a hammerhead, poker, or stone edge); produces a discrete...
- GRIM3
- Glass Refractive Index Measurement instrument, third generation. Hot-stage microscopy with sodium D-line illumination; reports RI to ±0.00002.
- Hackle Lines
- Fine secondary cracks on the fracture surface that fan from the origin, perpendicular to the moving crack front. Used to track crack...
- Hering's Principle
- The 1853 observation that a radiating fracture from a subsequent impact is arrested when it reaches a fracture line produced by a...
- PDQ
- Paint Data Query database (RCMP-maintained). Cross-referenced from glass work when a vehicle is identified through paired glass and paint evidence.
- Perimortem Fracture
- A fracture produced at or near the time of death while the bone retains green (fleshed) properties; distinguished by sharp fracture margins...
- Radial Fracture
- Cracks that run outward from the point of impact like spokes on a wheel. Form first, on the side opposite the force.
- Radiating Fracture
- A linear fracture extending outward from the impact point, initiated by inner-table tension as the outer table is compressed; propagates until arrested...
Explained in these topics
- Blunt-Force Trauma: Radiating, Concentric and Depressed FracturesAn arc-shaped fracture encircling the impact zone, produced by outer-table bending tension at a distance from the focal impact; always post-dates the radiating...
- Glass Evidence: Fracture Patterns and Refractive IndexCracks that loop around the impact point, joining adjacent radial cracks. Form second, on the side the force came from.