Fracture principles: healing, classification, treatment and complications

Overview

Every fracture question rests on a few principles: how bone heals, how a fracture is described, how it is treated (reduce, hold, rehabilitate), and which complications to watch for. Two emergencies dominate the MCQs: the open fracture and compartment syndrome.

Definition and types of fracture

A fracture is a break in the continuity of a bone (or of a growth plate or joint surface).

Describing a fracture on X-ray

• Open or closed (skin broken over the fracture = open, previously "compound").
• Bone, site (diaphysis, metaphysis, intra-articular).
• Pattern: transverse, oblique, spiral (twisting), comminuted (more than two fragments), segmental, impacted, avulsion, compression.
• Displacement: translation, angulation, rotation, shortening (described by the position of the distal fragment).

Fractures in children

• Greenstick: one cortex breaks and the other bends.
• Torus (buckle): the cortex crumples from compression, usually distal radius.
• Plastic deformation: bone bends without a visible break.
• Physeal injuries: Salter-Harris types.

Classification systems to know

How fractures heal

Indirect healing (by callus): the usual way

Occurs when there is some movement at the fracture (casts, splints, intramedullary nails, bridging plates, external fixators).

• A little movement stimulates callus; too much movement prevents union (strain theory: very high strain gives fibrous tissue).
• The inner cambium layer of the periosteum supplies bone-forming cells; children's thick periosteum explains rapid healing.

Direct (primary) healing: no callus

• Occurs only with absolute stability: fragments compressed and held rigidly (compression plate, lag screws).
• Osteoclast cutting cones cross the fracture line followed by osteoblasts laying lamellar bone (contact healing); small gaps fill directly (gap healing).
• No external callus is seen on X-ray; the fracture line simply fades.

Union and consolidation

• Union: callus bridges the fracture; bone moves as one piece but is still tender and not ready for full load.
• Consolidation: fracture line obliterated by bone, painless, full strength.

Perkins timetable (rough guide): a spiral upper limb fracture unites in 3 weeks; double it for consolidation; double again for the lower limb; double again for a transverse fracture. Children heal faster.

Factors that delay healing

• Local: poor blood supply (e.g. scaphoid waist, femoral neck, distal third of tibia, talar neck), severe soft tissue damage, infection, too much movement, gap or soft tissue between fragments, pathological bone.
• General: old age, smoking, diabetes, malnutrition, steroids, NSAIDs (possibly), cytotoxic drugs.

Principles of treatment

First, treat the patient

Follow ATLS: airway, breathing, circulation (with haemorrhage control), disability, exposure. A dramatic limb fracture must not distract from a life-threatening injury.

Then the fracture: reduce, hold, rehabilitate

1. Reduce (if displaced and reduction matters)

• Closed reduction under analgesia or anaesthesia (traction in the line of the bone, then reverse the mechanism).
• Open reduction when closed fails, for intra-articular fractures, or with soft tissue interposed.
• Not every fracture needs reduction (e.g. undisplaced, or minor angulation in a child who will remodel).

2. Hold

Indications for internal fixation:

• Fractures that cannot be reduced or held closed (e.g. displaced forearm shaft fractures in adults).
• Intra-articular displaced fractures.
• Unstable fractures likely to redisplace.
• Fractures that unite poorly (e.g. displaced femoral neck).
• Pathological fractures.
• Multiple injuries (early stabilisation reduces complications such as fat embolism and ARDS).
• To allow early nursing and mobilisation in the elderly.

3. Rehabilitate (exercise): reduce swelling (elevation), keep joints moving, restore muscle power and return to function.

Open fractures

Gustilo-Anderson classification

The final grade is set in theatre after debridement. A farmyard-contaminated small wound is treated as grade III. Infection risk rises with grade (under 2% in grade I to over 10% in grade III).

Emergency department steps

1. ATLS assessment and resuscitation.
2. IV antibiotics as soon as possible: ATLS uses a weight-based first-generation cephalosporin (cefazolin) for all, adding cover (e.g. aminoglycoside) for severe grades; clindamycin in severe penicillin allergy. Delay beyond about 3 hours raises the infection rate. Follow the local protocol.
3. Tetanus prophylaxis (toxoid, with immunoglobulin if not immunised).
4. Remove gross contamination, photograph the wound, cover with a saline-soaked sterile dressing; do not keep reopening it, do not probe it.
5. Realign and splint the limb; recheck pulses and neurology after any manipulation.
6. Watch for compartment syndrome (an open wound does not prevent it).

In theatre

• Debridement and lavage (excise dead and contaminated tissue, extend the wound, remove loose devitalised bone, copious saline).
• Stabilise the fracture (external fixator or internal fixation depending on contamination and grade).
• Early soft tissue cover (primary closure for clean low-grade wounds; delayed closure, skin graft or flap, ideally with orthopaedic and plastic surgeons together).
• Antibiotics are stopped soon after definitive wound cover (Bailey: about 48 hours after closure; Apley: total course not more than about 72 hours).

Complications of fractures

Classification by time

Compartment syndrome

Definition: raised pressure inside a closed osseofascial compartment that reduces capillary perfusion, causing muscle and nerve ischaemia.

Causes:

• Fractures (most cases), especially tibial shaft (open or closed), forearm and supracondylar fractures in children.
• Crush injury and soft tissue contusion, tight casts or bandages, reperfusion after arterial repair, burns (circumferential), bleeding disorders and anticoagulants, IV extravasation.

Pathophysiology: swelling raises compartment pressure → venous outflow obstructed → capillary perfusion falls → ischaemia → more swelling (vicious circle). Muscle death after about 4-6 hours of ischaemia.

Clinical features (most important first):

Pressure measurement: useful in the unconscious, intubated or uncooperative patient and when in doubt. Measure near (not in) the fracture.

• ΔP = diastolic BP − compartment pressure. A ΔP of 30 mmHg or less is the usual threshold for fasciotomy.
• An absolute pressure of 30 mmHg or more is also used.

Management:

1. Split the cast and all dressings down to skin; remove circumferential bandages.
2. Rest the limb at about heart level; avoid high elevation, which lowers perfusion pressure further.
3. Correct hypotension; give oxygen.
4. If not resolving promptly: urgent fasciotomy of all compartments (leg: four compartments through two incisions, anterolateral and posteromedial). Leave wounds open; close or graft at about 48-72 hours.
5. Stabilise the fracture; watch for myoglobinuria and kidney injury.

Outcome: decompression within about 6 hours usually gives full recovery. Late result: Volkmann ischaemic contracture (forearm flexors after supracondylar fracture: wrist and fingers flexed) or a contracted leg with claw toes.

Fat embolism syndrome

• After long-bone fractures (femur, tibia) and pelvic fractures, especially multiple fractures in young adults; also after nailing.
• Onset usually 24-72 hours after injury.
• Triad: respiratory distress (hypoxia), neurological changes (confusion, restlessness, drowsiness), petechial rash (axillae, chest, conjunctivae, oral mucosa).
• Other: fever, tachycardia, fat globules in urine or sputum, retinal changes, falling platelets and haemoglobin.
• ABG: PaO2 below about 8 kPa (60 mmHg) within the first 72 hours after major injury is suspicious.
• Prevention: early stabilisation of long-bone fractures.
• Treatment: supportive: oxygen, ventilation as for ARDS, fluids. Heparin and steroids are not established treatments.

Crush syndrome

Prolonged limb compression (rubble, vehicle) → muscle necrosis → on release, myoglobin, potassium and acid enter the circulation → acute kidney injury, hyperkalaemia, shock. Treat with aggressive IV fluids before and after release, monitor urine output and potassium.

Delayed union and non-union

• Delayed union: slower than expected but still progressing.
• Non-union: healing has stopped; may form a pseudarthrosis (false joint).
• Common sites: distal third tibia, scaphoid, femoral neck, humeral shaft, lateral humeral condyle in children.

Malunion

Fracture unites in a poor position (angulation, rotation, shortening). Examples: Colles fracture (dinner-fork deformity), supracondylar fracture (cubitus varus, "gunstock" deformity). Children remodel angulation in the plane of joint movement near the physis, but not rotation.

Avascular necrosis

X-ray: the dead segment looks denser than the surrounding (disuse osteoporotic) bone, then collapses. MRI shows it earliest.

Other late complications

• Complex regional pain syndrome (Sudeck atrophy): burning pain out of proportion, swelling, shiny skin, colour and temperature change, stiffness, patchy osteoporosis; classically after a distal radius fracture. Treat with physiotherapy, analgesia and specialist pain care.
• Myositis ossificans (heterotopic ossification): bone forms in a damaged muscle, typically brachialis after elbow injuries or the quadriceps after a thigh contusion; avoid forceful passive stretching and massage.
• Joint stiffness, secondary osteoarthritis, growth disturbance after physeal injury, tendon rupture (extensor pollicis longus after distal radius fracture).

Quick revision

• Callus: haematoma, inflammation, soft callus, hard callus, remodelling; needs a little movement.
• Absolute stability (lag screw, compression plate) gives direct healing without callus; essential for joint surfaces.
• Salter-Harris II commonest; V (crush) worst for growth.
• Reduce, hold, rehabilitate; but ATLS comes first.
• Open fracture: early IV antibiotics, tetanus, photo and saline dressing, splint, then debridement, fixation, cover.
• Gustilo I under 1 cm; II over 1 cm; IIIA coverable; IIIB needs flap; IIIC arterial repair.
• Compartment syndrome: pain out of proportion and on passive stretch; split dressings; fasciotomy if ΔP 30 mmHg or less.
• Fat embolism: 24-72 h, hypoxia, confusion, petechiae; early fixation prevents; oxygen treats.
• Hypertrophic non-union = instability; atrophic = poor biology.

Written by The House Job from standard references (Apley; Bailey & Love; ATLS).

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