Fracture Classification & Healing

A fracture is any break in the structural continuity of bone, cartilaginous epiphysis, or articular surface. For NEET PG, the high-yield triad is: how we classify fractures (descriptive, Gustilo–Anderson for open injuries, AO/OTA, plus paediatric Salter–Harris), the biology of healing (haematoma → remodelling), and the outcomes of healing (union, delayed union, non-union, malunion). Master the cut-offs and named systems below — they recur every year.

Definition & basic descriptive terminology

Every fracture in a clinical question is described along several axes. Knowing the vocabulary lets you decode any stem.

Feature	Terms used
Skin integrity	Closed (simple) vs Open (compound — skin/mucosa breached, bone communicates with exterior)
Completeness	Complete vs Incomplete (greenstick, buckle/torus, hairline)
Pattern	Transverse, oblique, spiral, comminuted (>2 fragments), segmental, butterfly fragment
Displacement	Translation, angulation, rotation, shortening/distraction
Mechanism	Traumatic, stress (fatigue/insufficiency), pathological
Special	Avulsion, impacted, depressed, compression (crush)

High-yield: A spiral fracture is caused by a torsional/rotational force; a transverse fracture by a direct/bending force; a butterfly fragment by bending plus axial load. In a child, a non-ambulatory infant with a spiral femur fracture should raise suspicion of non-accidental injury.

A pathological fracture occurs through abnormal bone (osteoporosis, metastasis, myeloma, simple bone cyst, giant cell tumour) with trivial or no trauma. A stress fracture occurs in normal bone subjected to repetitive submaximal load (military recruits — march fracture of 2nd/3rd metatarsal; tibia in runners).

Open (compound) fractures — Gustilo–Anderson classification

This is the single most tested classification in trauma. It grades open long-bone fractures by wound size, soft-tissue damage, contamination, and vascular status — and dictates antibiotic choice and prognosis.

Type	Wound	Soft tissue / energy	Other features
I	< 1 cm, clean	Minimal damage, low energy	Simple fracture pattern
II	1–10 cm	Moderate damage, some crush	Moderate comminution/contamination
III	> 10 cm	Extensive soft-tissue loss, high energy	Highly contaminated
IIIA	—	Adequate periosteal/soft-tissue coverage despite extensive injury	Coverage possible without flap
IIIB	—	Extensive periosteal stripping, needs flap coverage	Bone exposed; massive contamination
IIIC	—	Any open fracture with arterial injury requiring repair	Regardless of wound size

High-yield: Any open fracture associated with a vascular injury needing repair is Gustilo type IIIC — even if the wound is only 1 cm. Likewise, segmental fractures, farmyard/highly contaminated wounds, shotgun injuries, and those presenting after long delay are automatically type III.

Mnemonic for coverage — IIIA Adequate, IIIB Bare bone needs flap, IIIC Circulation lost.

Antibiotic guidance (must-know):

• Type I & II → first-generation cephalosporin (cefazolin).
• Type III → add an aminoglycoside (gram-negative cover).
• Farm injuries / heavy soil contamination → add penicillin/metronidazole for Clostridium (clostridial myonecrosis) cover.
• Tetanus prophylaxis in all.

High-yield: The most important single step in open-fracture management is early thorough debridement and irrigation plus IV antibiotics within the "golden" early window (modern evidence emphasises antibiotics ASAP rather than a rigid 6-hour rule). Higher Gustilo grade = higher infection and non-union rate.

AO/OTA classification (alphanumeric)

The AO/OTA system codes fractures numerically so they are universally comparable.

• First digit = bone: 1 humerus, 2 radius/ulna, 3 femur, 4 tibia/fibula.
• Second digit = segment: 1 proximal, 2 diaphyseal (shaft), 3 distal.
• Letter = pattern: A simple, B wedge, C complex/comminuted (increasing severity A→C).

High-yield: In AO, severity increases A → B → C. So a "33-C" is a complex distal femur fracture. This ordering (simple → wedge → multifragmentary) is a favourite one-liner.

Paediatric fractures — Salter–Harris (physeal injuries)

Children's fractures behave differently because of the open physis (growth plate), thick periosteum, and remodelling potential. Physeal injuries are graded by Salter–Harris.

Type	Anatomy of fracture line	Mnemonic (SALTR)	Prognosis
I	Through physis only (Slipped)	S = Slip / Straight across	Good
II	Physis + metaphysis (Thurston-Holland fragment) — commonest	A = Above	Good
III	Physis + epiphysis (intra-articular)	L = Lower	Guarded — needs anatomical reduction
IV	Epiphysis + physis + metaphysis	T = Through/Together	Poor — growth arrest risk
V	Crush of physis	R = Rammed/cRush	Worst — growth arrest, often diagnosed late

High-yield: Salter–Harris II is the most common. Types III–V are intra-articular or crushing and carry the highest risk of growth disturbance/limb-length discrepancy, hence often need open reduction and internal fixation. Type V is frequently missed on initial X-ray.

Other classic paediatric patterns: greenstick (incomplete, cortex broken on one side), buckle/torus (compression buckle of metaphyseal cortex — very stable), and plastic deformation (bowing without a clear fracture line).

Stages of fracture healing (secondary / endochondral healing)

Most fractures treated non-operatively or with relative stability heal by secondary (indirect) healing via callus, driven by interfragmentary micromotion. There are classically five overlapping stages.

Haematoma → Inflammation → Soft (fibrocartilaginous) callus → Hard (bony) callus → Remodelling

1. Haematoma formation (0–48 h): Bleeding from torn vessels and periosteum forms a fracture haematoma; clot acts as a fibrin scaffold.
2. Inflammation (1–7 days): Cytokines (TNF-α, IL-1, IL-6), platelet-derived growth factor, BMP-2/7, TGF-β recruit inflammatory cells and mesenchymal stem cells. Macrophages clear debris.
3. Soft callus / fibrocartilaginous callus (1–3 weeks): Chondrocytes and fibroblasts lay down type II collagen cartilage and fibrous tissue bridging the gap; provides initial mechanical stability.
4. Hard callus / bony callus (3–6 weeks → up to months): Endochondral ossification converts cartilage to woven bone; angiogenesis brings osteoblasts. Callus becomes radiologically visible.
5. Remodelling (months to years): Osteoclasts and osteoblasts (Wolff's law — bone remodels along stress lines) convert woven bone to lamellar bone, restoring the medullary canal and original contour. Children remodel far more efficiently.

High-yield: Soft (fibrocartilaginous) callus is the FIRST callus formed and the FIRST radiological sign of healing in secondary union. The progression of callus composition is fibrous/cartilage (type II collagen) → woven bone → lamellar bone. BMP-2 and BMP-7 are osteoinductive growth factors used to augment healing.

Primary (direct) healing

Occurs with rigid anatomical fixation and absolute stability (e.g., compression plating, lag screw) where there is no callus.

• Contact healing — gap < 0.01 mm and strain < 2%: osteons cross directly via cutting cones.
• Gap healing — gap up to ~0.8–1 mm: lamellar bone fills the gap first, then remodels.

High-yield: Absence of visible callus is the radiological hallmark of primary bone healing under rigid fixation. Excessive interfragmentary strain (>10%) leads to non-union; very low strain (<2%) favours direct healing — this is Perren's strain theory.

Radiological & clinical signs of union

Clinical union: no tenderness or mobility at fracture site, no pain on stressing/weight-bearing, ability to use the limb. Radiological union: bridging callus across the fracture line on at least 3 of 4 cortices (on two orthogonal views), trabeculae crossing the fracture, and obliteration of the fracture line.

High-yield: Bridging of 3 out of 4 cortices on X-ray = radiological union — a classic single-best-answer fact.

Outcomes that go wrong — delayed union, non-union, malunion

Term	Definition	Key features
Delayed union	Healing slower than expected for that bone/site but still progressing	Fracture line visible, scanty callus; still has potential to unite
Non-union	Healing has stopped; will not unite without intervention	No progression for ~3 months and no progress over 3 consecutive months (FDA: 9 months); pain/mobility persist
Malunion	United, but in a non-anatomical position	Angulation, rotation, shortening; functional/cosmetic deficit

Types of non-union:

• Hypertrophic ("elephant-foot") — abundant callus but no bridging, due to excessive movement / inadequate immobilisation with good blood supply. Treatment: provide stability (rigid fixation).
• Atrophic — no callus, poor vascularity/biology (gap, soft-tissue interposition, infection, devascularised bone). Treatment: bone grafting + stable fixation (biology + stability).
• Oligotrophic — minimal callus, often after displacement/distraction.

High-yield: Hypertrophic non-union = mechanical problem → give stability. Atrophic non-union = biological problem → give bone graft (and stability). Bone scan: hypertrophic is "hot"; atrophic is "cold/avascular."

Factors that delay/impair fracture healing

A favourite list question. Group them as local vs systemic.

Local factors: open fracture/severe soft-tissue injury, infection, inadequate immobilisation or excessive motion, bone gap/soft-tissue interposition, comminution, poor blood supply / segmental fractures, intra-articular fractures (synovial fluid lyses clot), bone loss.

Systemic factors: advancing age, diabetes mellitus, smoking (nicotine — strongly impairs healing), malnutrition (protein, vitamin C and D deficiency), corticosteroids, NSAIDs (inhibit prostaglandin-mediated osteogenesis), chemotherapy, anaemia, immunosuppression.

High-yield: Bones notorious for avascular necrosis and non-union due to retrograde/precarious blood supply: scaphoid (proximal pole), femoral head (subcapital neck #), talus (body), and the diaphysis of long bones at the watershed zone. Mnemonic for AVN-prone bones: "Scared Foot Tackles" → Scaphoid, Femoral head, Talus.

Investigation of choice

• Plain radiograph (X-ray) — two orthogonal views (AP + lateral), including the joint above and below — is the first and primary investigation for any suspected fracture.
• CT — for complex intra-articular fractures (tibial plateau, calcaneus, acetabulum, pilon), pre-operative planning, and to assess union in equivocal cases.
• MRI — best for occult/stress fractures, scaphoid fractures with normal initial X-ray, marrow oedema, and soft-tissue/ligamentous injury.
• Bone scan (technetium-99m) — occult/stress fractures (becomes positive 2–3 days after injury) and to differentiate hypertrophic (hot) vs atrophic (cold) non-union.

High-yield: Suspected scaphoid fracture with a normal X-ray → treat as a fracture (thumb spica), repeat X-ray in 10–14 days, or get an MRI (investigation of choice for occult scaphoid #).

Management — principles & "drug/treatment of choice"

The four R's: Resuscitate → Reduce → Restrict (immobilise/Retain) → Rehabilitate.

1. Reduction — closed (manipulation) or open (surgical) to restore alignment.
2. Hold / fixation — POP cast, traction, external fixator, or internal fixation (plates, screws, intramedullary nails, K-wires).
3. Rehabilitation — early mobilisation to prevent fracture disease (stiffness, disuse osteopenia, sympathetic dystrophy).

High-yield: Intramedullary interlocking nailing is the implant of choice for diaphyseal (shaft) fractures of femur and tibia in adults — it is load-sharing and allows early weight-bearing. Compression plating gives absolute stability (primary healing) and is used for forearm shaft and many intra-articular fractures. External fixation is preferred for Gustilo IIIB/IIIC open fractures with severe soft-tissue compromise.

Adjuncts for delayed/non-union: bone grafting (autograft from iliac crest = gold standard, osteogenic + osteoinductive + osteoconductive), BMPs, low-intensity pulsed ultrasound, and correction of systemic factors (stop smoking, control diabetes).

Complications of fractures

• Immediate/early: haemorrhage and hypovolaemic shock, visceral/neurovascular injury, fat embolism (24–72 h, classic after long-bone fractures — petechiae, hypoxia, confusion), compartment syndrome.
• Late: delayed/non-union, malunion, avascular necrosis, Volkmann's ischaemic contracture (sequela of untreated forearm compartment syndrome), myositis ossificans (heterotopic bone, classic around elbow), joint stiffness, complex regional pain syndrome (Sudeck's atrophy), post-traumatic osteoarthritis, infection/osteomyelitis, growth disturbance in children.

High-yield: Compartment syndrome — earliest and most reliable symptom is pain out of proportion and pain on passive stretch of the muscles in the compartment. Pulselessness is a late sign — do NOT wait for it. Diagnosis is largely clinical; treatment is emergency fasciotomy. A compartment pressure within 30 mmHg of diastolic BP (delta-P < 30) is an indication to decompress.

Key differentials & "look-alikes"

• Stress fracture vs shin splints vs osteoid osteoma vs infection in a young athlete with leg pain and a normal early X-ray — MRI/bone scan distinguishes.
• Pathological fracture vs simple traumatic fracture — disproportionate trauma, lytic/sclerotic lesion, prior pain. Always image the whole bone and screen for primary malignancy/myeloma.
• Salter–Harris I vs sprain in a child — tenderness over the physis (not the ligament) suggests a physeal injury even with a normal X-ray.
• Hypertrophic vs atrophic non-union — callus quantity on X-ray and vascularity on bone scan, as above.

Recently asked / exam angle

• Gustilo IIIC is defined by arterial injury needing repair, regardless of wound size — repeatedly tested.
• The first radiological sign of healing and first callus is the soft/fibrocartilaginous callus; the sequence of callus collagen is type II → woven → lamellar bone.
• Salter–Harris II is the commonest; type V has the worst prognosis and is most often missed.
• Hypertrophic non-union = give stability; atrophic non-union = give bone graft.
• AO classification: A (simple) → B (wedge) → C (complex) in increasing severity.
• Union criterion: bridging callus across 3 of 4 cortices.
• NSAIDs and smoking delay healing; iliac crest autograft is the gold-standard graft.
• Implant of choice for femoral/tibial shaft = intramedullary interlocking nail.
• Compartment syndrome: pain on passive stretch is earliest; pulselessness is late; delta-P < 30 mmHg → fasciotomy.
• AVN-prone fractures: scaphoid proximal pole, femoral neck, talus.

Rapid revision

1. Open fracture = bone communicates with exterior; grade by Gustilo–Anderson; any vascular repair = IIIC.
2. Type I/II open → cefazolin; type III → add aminoglycoside; soil/farm → add penicillin for Clostridium.
3. Salter–Harris: SALTR — I Slip, II Above (commonest), III Lower, IV Through, V cRush (worst).
4. AO severity: A simple → B wedge → C complex.
5. Secondary healing stages: haematoma → inflammation → soft callus → hard callus → remodelling.
6. Soft (cartilaginous) callus is the first callus and first radiological sign; primary healing has NO callus.
7. Perren's strain theory: strain >10% → non-union; <2% → direct/primary healing.
8. Radiological union = bridging of 3 of 4 cortices.
9. Hypertrophic non-union (elephant-foot, hot scan) → stability; atrophic (cold scan) → bone graft.
10. Healing impaired by infection, NSAIDs, steroids, smoking, diabetes, poor blood supply, soft-tissue interposition.
11. Investigation of choice: X-ray (2 views, joint above & below) first; MRI for occult scaphoid/stress fractures.
12. Compartment syndrome: pain on passive stretch earliest, pulselessness late, delta-P < 30 mmHg → emergency fasciotomy.