Orthopedic Trauma & Compartment Syndrome

Trauma questions look like they are testing knowledge of injuries. They are almost always testing sequence.

The knowledge required is rarely obscure. What separates a correct answer from a wrong one is knowing which thing happens first, and why doing it second causes harm.

Three sequencing rules generate most of this chapter.

Resuscitate before you fix. An operation is itself a physiological insult, and a major fixation performed on an unresuscitated patient can kill them.

Decompress before you image. Compartment syndrome is a clinical diagnosis, and a limb sent for imaging to confirm it is a limb losing muscle.

Cover before you finish. An open fracture is a soft-tissue emergency, and definitive skeletal fixation without a plan for soft-tissue cover produces infected metal.

India makes this chapter unusually concrete. The Ministry of Road Transport and Highways recorded 4,87,707 road accidents in 2024, with 1,77,175 deaths and 4,71,441 injuries, roughly 485 deaths every day. Two-thirds of those killed were between 18 and 45.

1. The Second Hit

A severely injured patient mounts a systemic inflammatory response to the injury itself. This is the first hit.

Any subsequent insult, including a long operation with blood loss, reaming of a medullary canal, hypothermia and further tissue handling, lands on an already primed immune system. This is the second hit, and it is what converts a survivable injury into multi-organ failure and acute respiratory distress syndrome.

The lethal triad describes the state to avoid: hypothermia, acidosis and coagulopathy, each of which worsens the other two.

This is why the timing of fracture fixation in a polytrauma patient is a decision about physiology rather than about the fracture. The bone will wait. The patient may not.

Damage control versus early total care

Damage control orthopaedics means rapid temporary stabilisation, almost always with an external fixator, taking minutes rather than hours, with definitive fixation deferred until the patient is physiologically restored.

Early total care means definitive fixation at the first operation, which avoids a second anaesthetic and allows earlier mobilisation.

The modern position, sometimes called early appropriate care, is that the choice is made on measured resuscitation status rather than on a fixed rule. Lactate, base deficit, pH, temperature and coagulation together answer the question.

A patient whose lactate is falling, base deficit is correcting and temperature is normal tolerates definitive fixation. A patient who is cold, acidotic and coagulopathic gets an external fixator and a warm bed.

The evidence that early femoral nailing reduces pulmonary complications is real, and so is the evidence that the same operation performed on an unresuscitated patient increases them. Both are true, which is precisely why the decision is physiological.

Tranexamic acid

The CRASH-2 trial showed that tranexamic acid reduces all-cause mortality in bleeding trauma patients without increasing vascular occlusive events, and that it is highly cost-effective.

The time window is the examinable point. Benefit depends on early administration, and treatment beyond three hours from injury is unlikely to help and may be harmful.

The injury you have not found yet

Roughly one in ten significant injuries in a polytrauma patient is missed during the primary and secondary surveys, and the pattern is predictable.

Missed injuries cluster in the patient who is intubated, distracted by a dominant injury, or taken straight to theatre. Hands, feet, the cervical and thoracic spine and the non-dominant limb are the usual sites, because they are neither life-threatening nor obvious.

The tertiary survey exists for exactly this. It is a complete head-to-toe re-examination with a review of every image, performed once the patient is awake and stable, conventionally within 24 hours.

A missed scaphoid or Lisfranc injury rarely kills anyone, but it is often what determines whether a survivor returns to work.

2. The Bleeding Pelvis

A disrupted pelvic ring can hold several litres of blood, and the patient exsanguinates into a space nobody can compress.

Most of the bleeding is venous, from the presacral plexus, and from the cancellous surfaces of the broken bones themselves. Arterial bleeding accounts for a minority of cases but a majority of deaths.

That distribution dictates the sequence. Reduce the volume of the pelvis first, because venous and bony bleeding tamponades once the ring is closed.

The binder

A pelvic binder is applied at the level of the greater trochanters, not the iliac crests.

Placing it too high is the commonest practical error and achieves nothing, because the mechanical lever that closes an open-book injury acts through the trochanters.

If closing the ring and transfusion do not stabilise the patient, the options are preperitoneal pelvic packing and angiographic embolisation. Resuscitative endovascular balloon occlusion of the aorta has not been shown superior to packing, and its role remains a matter of local protocol rather than established superiority.

3. Open Fractures

An open fracture is a soft-tissue injury with a wound that communicates with the fracture. The bone is the least of it.

The Gustilo-Anderson classification is graded by soft tissue, not by the bone.

Two things about this classification are commonly got wrong.

It is definitively assigned at the time of debridement, not in the emergency department, because the true extent of devitalised tissue is not visible through a small skin wound. High-energy injuries are routinely upgraded in theatre.

IIIC is defined by the arterial injury, not the wound size. A small puncture with a divided popliteal artery is IIIC.

Infection risk rises sharply through the grades, with reported sepsis rates around 4 per cent for IIIA and far higher for IIIB and IIIC.

What actually reduces infection

Antibiotics as early as possible, ideally within an hour of injury, are the single most effective intervention. This matters more than the exact timing of surgery, and it is the step most often delayed while imaging and referrals are arranged.

A first-generation cephalosporin is standard, with additional Gram-negative cover for higher grades and specific cover for heavily contaminated agricultural or aquatic wounds. Tetanus status is checked in every case.

The traditional six-hour rule for debridement is not supported by evidence. Current standards permit debridement within a reasonable window, commonly cited as up to 12 to 24 hours for most injuries, performed by an appropriately skilled team rather than urgently by whoever is available.

Immediate surgery is still required for gross contamination, vascular compromise and compartment syndrome.

The remaining principle is orthoplastic. Skeletal fixation and soft-tissue cover are planned together, and early definitive cover, generally within 72 hours, reduces infection. Metal under an open wound becomes infected metal.

4. Compartment Syndrome

This is the diagnosis that costs limbs, and it is missed because the sign everyone looks for is the one that does not appear.

The pathophysiology

Tissue pressure inside a closed fascial compartment rises above the pressure needed to perfuse the capillaries. Venous outflow is obstructed first, which raises pressure further, which obstructs more outflow.

Muscle is ischaemic long before any large artery is occluded. Arterial pulses are therefore usually present in an established compartment syndrome.

A palpable pulse does not exclude the diagnosis and never has. Pulselessness, if it occurs at all, is a very late finding.

The clinical signs, ranked by usefulness

Pain out of proportion to the injury is the earliest and most important. Pain on passive stretch of the muscles within the compartment is the most reliable examination sign, because it directly loads the ischaemic muscle.

Paraesthesia in the distribution of a nerve traversing the compartment is the earliest objective neurological sign.

Paralysis and pulselessness are late and indicate damage already done. The classical five Ps are actively misleading if used as a checklist, because four of them appear too late to be useful.

An increasing analgesic requirement in a patient with a tibial fracture is a warning sign in its own right.

Measuring pressure

Compartment pressure measurement is not needed when the clinical picture is clear. It is needed when the patient cannot report pain: the unconscious, the intubated, the child, and the patient with a regional block.

Delta pressure is diastolic blood pressure minus compartment pressure, and a value at or below 30 mmHg supports fasciotomy.

Recent work adds a refinement worth knowing. A single reading is less informative than a trend, because patients who develop compartment syndrome show a steady rise in compartment pressure over hours while those who do not show a natural decline. Continuous or serial monitoring reduces both delayed and unnecessary fasciotomy.

Hypotension matters here in a way that catches people out. Delta pressure depends on diastolic blood pressure, so a hypotensive patient can develop compartment syndrome at a lower absolute compartment pressure.

Treatment

Split every circumferential dressing, bandage and cast down to skin, since a cast that is only bivalved still constricts.

Keep the limb at the level of the heart. Elevating it reduces arterial inflow pressure and worsens perfusion, which is the opposite of what is intended.

Correct hypotension, then perform fasciotomy without delay. The leg has four compartments and is decompressed through two incisions. Wounds are left open and closed or grafted later.

The forearm equivalent left untreated becomes Volkmann ischaemic contracture, the fixed flexion deformity that follows muscle necrosis and fibrosis.

5. Crush Syndrome

Crush syndrome is the systemic consequence of prolonged muscle compression, and it is a disease of reperfusion rather than of compression.

While the limb is compressed, the damaged muscle is isolated. When the weight is lifted, potassium, myoglobin, phosphate and urate flood the circulation at once.

Three things then happen. Hyperkalaemia can cause immediate cardiac arrest. Myoglobin precipitates in renal tubules and produces acute kidney injury. Fluid sequesters into the injured muscle and produces hypovolaemia.

The counterintuitive and examinable point is that fluid resuscitation should begin before extrication where that is possible, so that the circulation is loaded before the potassium arrives.

Treatment is aggressive intravenous fluid, urgent management of hyperkalaemia, and monitoring for renal failure. Fasciotomy is performed for genuine compartment syndrome in salvageable muscle, but opening a limb full of already necrotic muscle adds an infection risk without benefit.

6. Vascular Injury and the Mangled Limb

Hard signs of arterial injury are pulsatile bleeding, an expanding haematoma, a palpable thrill or audible bruit, and clear distal ischaemia. These mandate exploration rather than further investigation.

Soft signs, including a history of significant bleeding, a small stable haematoma or an unexplained neurological deficit, justify measuring the ankle-brachial index and imaging.

The recurring examination scenarios are knee dislocation with popliteal artery injury, supracondylar humerus fracture with brachial artery compromise, and shaft fractures with segmental displacement.

Sequence again decides the answer. Reduce and stabilise the skeleton first where the ischaemia is caused by displacement, because reduction often restores flow. Where the vessel is divided, a temporary shunt allows perfusion while the skeleton is fixed, and definitive repair follows.

The mangled limb decision involves the patient's physiology, the warm ischaemia time, the state of the plantar nerves and soft tissues, and the realistic function of a salvaged limb. Scoring systems such as the mangled extremity severity score inform the discussion but do not decide it.

7. Spinal Injury in the Trauma Patient

Two distinctions carry most of the marks.

Spinal shock is a neurological state; neurogenic shock is a circulatory one. Spinal shock is the transient loss of all cord function below the level of injury, including reflexes, and it resolves over days. Its end is signalled by return of the bulbocavernosus reflex.

Neurogenic shock is hypotension with bradycardia, caused by loss of sympathetic outflow in injuries above roughly the sixth thoracic level. This is the opposite of the tachycardia of hypovolaemic shock, and mistaking it for bleeding leads to over-transfusion, while assuming it too readily leads to a missed haemorrhage.

Complete versus incomplete injury cannot be assessed until spinal shock has resolved, and the presence of sacral sparing, meaning perianal sensation or voluntary anal contraction, indicates an incomplete injury with a better prognosis.

High-dose methylprednisolone is no longer recommended in acute spinal cord injury, since the harms outweigh a marginal and disputed benefit.

8. Worked Examples

Example 1. A 24-year-old with a closed tibial shaft fracture in a cast reports escalating pain 8 hours after admission, requiring increasing morphine. The dorsalis pedis pulse is easily palpable and the foot is warm. What is the next step?

Treat this as compartment syndrome. A palpable pulse does not exclude it, because the pressure needed to obstruct capillaries and small veins is far below that needed to occlude a major artery, so pulses are typically present throughout. Escalating analgesic requirement is itself a warning sign.

Split the cast and all dressings down to skin immediately, keep the limb at heart level rather than elevating it, examine for pain on passive stretch of the toes, and proceed to fasciotomy without waiting for imaging.

Example 2. A polytrauma patient has a femoral shaft fracture, a splenic injury and a lactate of 6 mmol/L with a base deficit of −9 and a temperature of 34.5 degrees Celsius. Should the femur be nailed now?

No. The physiology, not the fracture, decides. Rising lactate, a large base deficit and hypothermia indicate incomplete resuscitation, and a long reamed nailing would deliver a second hit to an already primed inflammatory system, risking acute respiratory distress syndrome and multi-organ failure. Apply an external fixator as damage control, continue resuscitation and rewarming, and convert to definitive fixation once lactate, base deficit and temperature have corrected.

Example 3. A farmer sustains an open tibial fracture with a 3 cm wound contaminated with soil. He arrives 2 hours after injury. Theatre is available in 5 hours. What are the priorities?

Antibiotics immediately, since early administration is the single most effective measure against infection and is more important than the precise timing of surgery. Add Gram-negative cover for the agricultural contamination and check tetanus status. Photograph and dress the wound with a saline-soaked dressing, splint the limb, and assess neurovascular status including a specific look for compartment syndrome.

The old six-hour rule is not evidence-based, so a planned debridement by an appropriately skilled team within a reasonable window is preferable to an immediate operation by whoever is available. Grade the fracture definitively in theatre, not now.

Example 4. A man is rescued after 6 hours trapped under a collapsed wall. His legs are compressed but he is alert and haemodynamically stable. What is the greatest immediate danger and how is it managed?

Reperfusion, not compression. Lifting the weight releases potassium, myoglobin, phosphate and urate into the circulation simultaneously, and hyperkalaemia can cause cardiac arrest within minutes of extrication. Intravenous fluid should be started before the weight is lifted where that is feasible, so the circulation is loaded first. Anticipate hyperkalaemia with monitoring and immediate treatment, give aggressive fluid resuscitation to protect the kidneys from myoglobin precipitation, and monitor for acute kidney injury. Reserve fasciotomy for genuine compartment syndrome in viable muscle.

Example 5. A patient with a cervical spine injury is hypotensive at 80/50 with a heart rate of 52. The abdomen is soft and the pelvis is stable. What is the diagnosis, and what is the trap?

Neurogenic shock, from loss of sympathetic outflow in an injury above roughly T6. The combination of hypotension with bradycardia is the discriminator, since hypovolaemic shock produces tachycardia. Treatment is fluid with vasopressor support rather than continued transfusion alone. The trap runs in both directions: attributing the hypotension to bleeding leads to over-transfusion, while accepting neurogenic shock too readily leads to a missed haemorrhage, so occult bleeding must still be excluded rather than assumed absent.

Summary

Trauma questions test sequence: resuscitate before fixing, decompress before imaging, cover before finishing.

The second hit is the reason a major operation can kill a survivable patient.

The lethal triad is hypothermia, acidosis and coagulopathy.

Damage control means a fast external fixator; early total care means definitive fixation; physiology decides which.

Tranexamic acid works within three hours of injury and not after.

Most pelvic bleeding is venous and bony, so close the ring first; the binder goes on the greater trochanters.

Gustilo-Anderson is graded by soft tissue and assigned definitively in theatre.

IIIC is defined by arterial injury, whatever the wound size.

Antibiotics within an hour matter more than the exact timing of debridement.

The six-hour rule is not evidence-based; gross contamination, ischaemia and compartment syndrome still need immediate surgery.

In compartment syndrome, pulses are present; pain on passive stretch is the reliable sign.

Delta pressure is diastolic minus compartment pressure, and 30 mmHg or less supports fasciotomy.

Measure pressure when the patient cannot report pain, and value trends over single readings.

Split casts to skin, keep the limb at heart level, correct hypotension, then decompress.

Crush syndrome is a reperfusion disease, so start fluids before extrication.

Hard signs of vascular injury mandate exploration; reduce the skeleton first when displacement is the cause.

Neurogenic shock is hypotension with bradycardia; hypovolaemic shock has tachycardia.

Sacral sparing means an incomplete cord injury and a better prognosis.