Types of non union

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types of non-union fracture classification Weber Cech hypertrophic atrophic

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Here is a comprehensive overview of the types of non-union based on the Weber & Cech classification (1976), which remains the most widely used system worldwide.

Definition

Non-union is a fracture that has failed to heal and shows no potential to heal without further intervention. It can also be defined as a fracture failing to show clinical or radiological improvement over 3 months. In practice, the term is generally not applied until 6 months after injury. - Bailey & Love's Short Practice of Surgery, 28th Ed.

Classification (Weber & Cech, 1976)

Non-unions are divided into two broad groups based on biological viability (vascularity) at the fracture site:

GROUP 1: VIABLE (Hypervascular / Reactive) Non-Unions

Biology is intact - the fracture ends have adequate blood supply and bone-forming capacity. The problem is mechanical (insufficient stability).

1. Hypertrophic Non-Union ("Elephant Foot")

Appearance: Abundant callus formation around both bone ends, producing a bulbous "elephant foot" shape on X-ray
Vascularity: Rich - good blood supply
Cause: Excessive micromotion / inadequate stabilization
Bone scan: Hot (increased uptake)
Treatment: Stabilization alone (plate, IM nail) - no bone graft needed. Biology is intact; rigid fixation allows fibrocartilage to mineralize, typically within 8 weeks
Campbell's Operative Orthopaedics, 15th Ed.

2. Hypertrophic Non-Union ("Horse Hoof")

Appearance: Moderate callus (less than elephant foot), persistent fracture line
Vascularity: Adequate
Cause: Less severe mechanical instability than elephant foot
Treatment: Stabilization +/- bone graft

3. Oligotrophic Non-Union

Appearance: Minimal or no callus, but bone ends are still viable
Vascularity: Adequate (confirmed by bone scan - shows increased uptake, unlike atrophic)
Cause: Distraction of bone ends, soft tissue interposition, or malreduction - the gap prevents contact even though biology is intact
Distinction from atrophic: Bone scan shows increased uptake (oligotrophic) vs. "cold cleft" (atrophic)
Treatment: Mechanical compression or bone grafting to restore contact + stabilization
Rockwood & Green's Fractures in Adults, 10th Ed. 2025

Diagram showing hypertrophic (left), oligotrophic (center), and atrophic (right) non-unions with vascular supply

GROUP 2: NON-VIABLE (Avascular / Areactive) Non-Unions

Biology is compromised - poor vascularity, little/no bone-forming capacity. The problem is both biological AND mechanical.

4. Torsion Wedge Non-Union

Appearance: A butterfly/wedge fragment with impaired vascularity
Cause: Butterfly fragment loses its blood supply, preventing incorporation
Treatment: Stabilization + bone graft

5. Comminuted Non-Union

Appearance: Multiple fragments, some or all avascular
Cause: High-energy injury with extensive devascularization
Treatment: Stabilization + aggressive bone grafting

6. Defect Non-Union

Appearance: A segment of bone is missing (from trauma, infection, or previous surgery)
Cause: Bone loss
Treatment: Bone transport (Ilizarov), vascularized fibular graft, or Masquelet technique

7. Atrophic Non-Union (True Atrophic)

Appearance: No callus at all, tapered/rounded bone ends, sclerosis and medullary canal closure
Vascularity: Poor to absent
Cause: Host factors (diabetes, smoking, malnutrition, radiation), severe soft tissue stripping, open fractures
Bone scan: Cold ("cold cleft" between areas of activity)
Treatment: Mandatory debridement/excision of avascular bone ends + aggressive biological stimulus (autograft, BMP) + rigid stabilization
Rockwood & Green's Fractures in Adults, 10th Ed. 2025

5. Pseudoarthrosis (Synovial / False Joint)

A special subtype - considered an extreme form of hypertrophic non-union in which chronic excessive motion leads to the formation of a synovial pseudocapsule around the fracture gap containing fluid, mimicking a true synovial joint. Medullary canals become sealed. On bone scan, a "cold cleft" appears between two "hot" areas.

Rockwood & Green's Fractures in Adults, 10th Ed. 2025; Campbell's Operative Orthopaedics, 15th Ed.

Infected (Septic) Non-Union

A separate classification dimension - any of the above types can be septic or aseptic. Septic non-unions are far more difficult to treat, typically requiring staged management: infection control first (with debridement and external fixation), then bone grafting after eradication of infection.

Summary Table

Type	Callus	Vascularity	Core Problem	Key Treatment
Hypertrophic (Elephant Foot)	Abundant	Good	Instability	Stabilize only
Hypertrophic (Horse Hoof)	Moderate	Good	Instability	Stabilize ± graft
Oligotrophic	Minimal	Adequate	Gap/distraction	Contact + stabilize ± graft
Torsion Wedge	Variable	Poor (fragment)	Avascular fragment	Stabilize + graft
Comminuted	Absent	Poor	Devascularization	Stabilize + graft
Defect	Absent	Poor	Bone loss	Bone transport / Masquelet
Atrophic	Absent	Poor/absent	Biology failure	Debride + graft + stabilize
Pseudoarthrosis	Variable	Variable	Chronic motion/false joint	Resect pseudocapsule + stabilize

Key clinical principle: Hypertrophic non-unions are a mechanical problem - stabilization alone is curative. Atrophic non-unions are a biological problem - both stability and biology (bone graft) must be restored. Oligotrophic sits between the two and often requires both.

Sources: Rockwood & Green's Fractures in Adults, 10th Ed. 2025; Campbell's Operative Orthopaedics, 15th Ed. 2026; Bailey & Love's, 28th Ed.; Pye's Surgical Handicraft, 22nd Ed.

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