The bone is usually the least urgent thing about a fracture.
Most fractures are not emergencies. What makes them dangerous is what lies next to the bone — the artery, the nerve, the muscle compartment, or the breach in the skin that has let the outside world in. A displaced fracture that is splinted and reviewed in the morning is usually fine; a fracture with a threatened limb is not.
So the discipline in this chapter is to describe the injury systematically and then look immediately past it: what is the neurovascular status, is the skin intact, and is the pain out of proportion? Those three questions separate the fractures that can wait from the ones that cannot.
🩺 Where this lives: Acute compartment syndrome is missed because people wait for the wrong sign. The classic teaching of "the five Ps" leads students to look for pulselessness — but compartment pressure exceeds capillary perfusion pressure long before it exceeds arterial pressure, so the pulse is usually still present while the muscle is dying. By the time a limb is pulseless, the window has closed. The finding that matters is pain out of proportion to the injury, made worse by passive stretch, and it appears early.
💡 A note on numbers. This chapter gives no doses, no antibiotic choices, no compartment pressure thresholds and no fracture grading systems. Antibiotic choice follows local guidance; compartment syndrome is a clinical diagnosis and quoting a pressure figure risks encouraging someone to wait for a measurement; and classification grades differ between sources. The trauma primary survey is covered in the Trauma chapter, the painful joint in its own Medicine chapter, and wound infection principles in the Wounds chapter.
Describing a fracture
Two habits are worth building. The X-ray rule — two views, two joints, and two occasions where doubt remains — exists because a single view can hide a displacement entirely and because the joint above and below is where the associated injury hides. And every fracture description ends with the neurovascular status: pulses, capillary refill, sensation and motor function distal to the injury, documented before and after any manipulation or splinting.
Compartment syndrome
WHY THE "FIVE Ps" MISLEAD
The classical list — pain, pallor, paraesthesiae, paralysis,
pulselessness — is ordered almost exactly backwards for
clinical usefulness.
PAIN OUT OF PROPORTION comes FIRST and is the sign to act
on. It is severe, unrelenting, and not relieved by
ordinary analgesia.
PAIN ON PASSIVE STRETCH of the muscles within the
compartment is the most useful examination finding.
The compartment feels TENSE and swollen.
PARAESTHESIAE come later.
PARALYSIS and PULSELESSNESS come LAST — by which time
irreversible muscle necrosis has usually occurred.
THE PULSE IS TYPICALLY PRESENT. Compartment pressure only
needs to exceed capillary pressure to stop perfusion of
muscle; it does not need to exceed arterial pressure. A
palpable pulse is entirely compatible with a dying limb.
COMMON SETTINGS: tibial and forearm fractures, crush
injury, a tight cast or circumferential dressing,
reperfusion after vascular injury, and burns.
WHAT TO DO
SPLIT the cast and dressings down to skin immediately —
this alone can relieve it and costs nothing
Keep the limb at heart level, not elevated, so as not to
reduce perfusion pressure further
URGENT surgical referral for FASCIOTOMY
Watch for rhabdomyolysis and acute kidney injury after
reperfusion
It is a CLINICAL diagnosis. Where measurement is available
it may support the decision, but a normal-sounding number
should never override convincing clinical findings.
Open fractures
💡 Exam angle: the priorities in an open fracture are examinable as a sequence — antibiotics early, tetanus status, photograph then cover with a sterile dressing, splint, assess neurovascular status, and urgent debridement. The two behaviours examiners like to test are the ones that sound helpful and are not: repeatedly uncovering the wound to show colleagues (which contaminates it further), and delaying antibiotics until a surgical decision is made. Time to antibiotics and time to debridement are what drive the infection rate.
Fractures with a characteristic complication
FIVE WORTH KNOWING COLD
SCAPHOID
Fall on an outstretched hand, tenderness in the
ANATOMICAL SNUFFBOX. The initial X-ray is frequently
NORMAL. The blood supply enters distally, so a proximal
fracture risks AVASCULAR NECROSIS and non-union.
THEREFORE: immobilise on clinical suspicion and re-image
or re-assess later. "X-ray normal, discharged" is the
classic error.
FEMORAL NECK
Typically an elderly patient after a low-energy fall. The
leg is SHORTENED and EXTERNALLY ROTATED. Risk of
avascular necrosis of the femoral head.
It carries substantial mortality — largely from the
patient's comorbidity, immobility and delirium rather
than the bone itself, which is why these patients need
medical as well as surgical care, early surgery where
possible, and attention to bone health afterwards.
SUPRACONDYLAR HUMERUS (child)
Fall on an outstretched hand. CHECK AND DOCUMENT the
radial pulse and the nerves — brachial artery and nerve
injury are recognised, and missed vascular injury leads
to contracture.
HUMERAL SHAFT → RADIAL NERVE palsy, giving WRIST DROP.
FIBULAR NECK → COMMON PERONEAL nerve, giving FOOT DROP.
IN CHILDREN, remember that the growth plate is weaker than
ligament, so what would sprain an adult often fractures a
child. Suspected growth plate injury needs orthopaedic
assessment because of the risk to future growth.
Bone and joint infection
Septic arthritis destroys a joint within days, which is why a hot, swollen, exquisitely painful joint that the patient refuses to move at all is an emergency rather than an outpatient problem. Aspirate before antibiotics where possible, and arrange urgent washout — the same source-control logic as an abscess. In osteomyelitis, remember that plain X-ray changes appear late, so a normal early film excludes nothing. And in this region, tuberculosis of bone and spine belongs in the differential for a chronic bone or joint problem.
Clinical reasoning: four presentations
🔍 Case 1 — pain despite the analgesia
PresentationA young man with a tibial fracture in a full cast has severe unrelenting pain unrelieved by repeated analgesia. Passive extension of his toes is agonising. His foot pulses are present, so the team is reassured and increases the analgesia.
TrapUsing the pulse to exclude compartment syndrome.
ReasoningCompartment pressure need only exceed capillary pressure to stop muscle perfusion, so a palpable pulse is entirely compatible with a dying limb. Pain out of proportion with pain on passive stretch is the diagnosis.
AnswerSplit the cast and dressings to skin immediately, keep the limb at heart level, and make an urgent surgical referral for fasciotomy. Escalating analgesia masks the only reliable early sign.
🔍 Case 2 — a normal scaphoid X-ray
PresentationA 22-year-old fell on an outstretched hand and is tender in the anatomical snuffbox. The wrist X-ray is reported as normal. He is discharged with simple analgesia and no follow-up.
ErrorTrusting an early normal film.
ReasoningScaphoid fractures are frequently invisible on initial imaging. Because the blood supply enters distally, a missed proximal fracture risks avascular necrosis and non-union with permanent wrist dysfunction.
AnswerImmobilise on clinical suspicion and arrange re-assessment and repeat imaging per local pathway. Snuffbox tenderness with a normal film is treated as a fracture until proven otherwise.
🔍 Case 3 — the wound everyone wanted to see
PresentationA man has an open tibial fracture after a road traffic accident. Over two hours the dressing is removed four times for different staff to inspect the wound. Antibiotics are deferred until the surgical team decides on a plan.
Two errorsRepeated exposure, and delayed antibiotics.
ReasoningEach uncovering adds contamination, and time to antibiotics is one of the strongest determinants of deep infection and subsequent osteomyelitis, which is very difficult to eradicate.
AnswerGive antibiotics early per local guidance, check tetanus status, photograph once, cover with a sterile dressing and leave it, splint, document neurovascular status, and arrange urgent debridement.
🔍 Case 4 — a child who will not walk
PresentationA 6-year-old refuses to bear weight and holds his knee still. He is febrile, and the knee is hot and swollen. The X-ray is normal, so he is treated as a viral arthritis and sent home.
DangerSeptic arthritis, and a normal X-ray means nothing.
ReasoningA hot swollen joint that a child refuses to move, with fever, is septic arthritis until proven otherwise — and it destroys cartilage within days. Radiographic changes in bone and joint infection appear late.
AnswerUrgent orthopaedic referral, aspirate before antibiotics where possible, and arrange washout. Also consider osteomyelitis, and in this region tuberculosis for a more chronic presentation.
Commonly confused
Confusion
The distinction
Why it matters
Pulse present vs no compartment syndrome
Pressure need only exceed capillary pressure
The pulse is usually still there.
Pain vs pain on passive stretch
Passive stretch pain is the key finding
Appears early, before paralysis.
Escalating analgesia vs investigating
Unrelenting pain is the signal
Analgesia masks the only early sign.
Normal X-ray vs no scaphoid fracture
Initial films are frequently normal
Missed fracture risks avascular necrosis.
Closed vs open fracture
Any nearby wound means open
Changes urgency and infection risk.
Inspecting vs covering a wound
Cover once and leave it
Each exposure adds contamination.
Septic arthritis vs transient synovitis
Fever with refusal to move at all
A joint is destroyed within days.
Normal X-ray vs no osteomyelitis
Radiographic changes appear late
Early films are unreliable.
Rapid revision
MUST-KNOW FACTS
1. Describe: which bone, where, PATTERN, DISPLACEMENT, open or closed.
2. ALWAYS document NEUROVASCULAR STATUS distal to the injury.
3. Document it BEFORE and AFTER manipulation or splinting.
4. X-RAY RULE: two views, two joints, two occasions if in doubt.
5. Any wound near a fracture is an OPEN fracture until proven otherwise.
6. COMPARTMENT SYNDROME: PAIN OUT OF PROPORTION is the earliest sign.
7. PAIN ON PASSIVE STRETCH is the key examination finding.
8. THE PULSE IS USUALLY PRESENT — it does not exclude the diagnosis.
9. Paralysis and pulselessness are LATE — the limb is already lost.
10. SPLIT the cast and dressings to skin immediately.
11. Keep the limb at HEART LEVEL, not elevated.
12. Treatment is urgent FASCIOTOMY.
13. Watch for rhabdomyolysis and acute kidney injury after reperfusion.
14. It is a CLINICAL diagnosis — do not wait for a pressure measurement.
15. OPEN FRACTURE: antibiotics EARLY, tetanus, photograph, cover, splint.
16. Then urgent surgical DEBRIDEMENT and stabilisation.
17. DO NOT repeatedly uncover the wound.
18. Time to antibiotics and debridement drives the infection rate.
19. Deep infection may become OSTEOMYELITIS, which is hard to eradicate.
20. SCAPHOID: snuffbox tenderness, X-ray often NORMAL initially.
21. Blood supply enters distally — risk of AVASCULAR NECROSIS.
22. Immobilise on suspicion and re-image.
23. FEMORAL NECK: elderly, SHORTENED and EXTERNALLY ROTATED leg.
24. Substantial mortality — these need medical care as well as surgery.
25. SUPRACONDYLAR HUMERUS in a child — check RADIAL PULSE and nerves.
26. HUMERAL SHAFT → RADIAL nerve → WRIST DROP.
27. FIBULAR NECK → COMMON PERONEAL nerve → FOOT DROP.
28. In children the GROWTH PLATE is weaker than ligament.
29. SEPTIC ARTHRITIS destroys a joint in DAYS.
30. Hot, swollen, refuses ALL movement, febrile — emergency.
31. ASPIRATE BEFORE ANTIBIOTICS where possible; urgent washout.
32. OSTEOMYELITIS: X-ray changes appear LATE — a normal film excludes nothing.
33. A child who will not use a limb has a problem until proven otherwise.
34. Consider TUBERCULOSIS of bone and spine in this region.
💡 Exam angle: three ideas answer most questions here. A present pulse does not exclude compartment syndrome. A normal X-ray does not exclude a scaphoid fracture or osteomyelitis. And a child who refuses to move a joint has septic arthritis until someone proves otherwise.
Syllabus points
Describing a fracture systematically
The X-ray rule and neurovascular documentation
Compartment syndrome: pain out of proportion
Why the five Ps mislead
Why the pulse is usually present
Splitting the cast and fasciotomy
Open fractures and early antibiotics
Why the wound is covered once
Scaphoid fracture and avascular necrosis
Femoral neck fracture in the elderly
Supracondylar fracture and the radial pulse
Nerve injuries by fracture site
Septic arthritis and osteomyelitis
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