Lower limb fractures and dislocations (including hip fractures)

Overview

Lower limb injuries range from the low-energy hip fracture of the frail elderly to high-energy femoral, tibial and pelvic injuries in young road accident victims. The hip fracture is the most important single topic: know the blood supply, the classification, and which operation suits which fracture.

Hip fractures in the elderly

Who and why

• Elderly, osteoporotic, mostly women; a simple fall.
• In a young adult a hip fracture needs high energy (or suggests a pathological bone).
• Mortality is high (the patient's general health matters as much as the fracture); early surgery and early mobilisation reduce complications.

Clinical features

• Unable to bear weight after a fall; groin pain (sometimes referred to the knee).
• Displaced fracture: leg shortened and externally rotated.
• Impacted (Garden I) fracture: patient may still walk; minimal deformity. A painful hip after a fall with a normal-looking film needs a lateral view, repeat imaging, or MRI.

Anatomy: why the site matters

Garden classification (intracapsular)

Treatment

• Operate early (ideally within about 36-48 hours) after correcting fluids, anaemia and medical problems.
• Mobilise the day after surgery; thromboprophylaxis; pressure care; delirium prevention; bone health (osteoporosis treatment) and falls assessment.
• Conservative treatment (traction) only for those too ill for anaesthesia.

Complications

• General: pneumonia, DVT/PE, pressure sores, delirium, urinary infection, death.
• Local (intracapsular): avascular necrosis (head collapse months to years later), non-union, implant cut-out, dislocation of a prosthesis.
• Local (extracapsular): malunion (coxa vara, shortening, external rotation), implant cut-out.

Hip dislocation

Posterior dislocation (by far the commonest)

• Dashboard injury: knee strikes the dashboard with hip and knee flexed; the femur is driven backwards.
• Leg is shortened, flexed, adducted and internally rotated.
• Often with a fracture of the posterior wall of the acetabulum or the femoral head.
• Check the knee too (patella fracture, posterior cruciate tear from the same blow) and the femoral shaft.

Complications:

• Sciatic nerve injury (about 10-20%), mostly the common peroneal division: foot drop, numb foot.
• Avascular necrosis of the femoral head; risk rises with delay: reduce as an emergency, within about 6 hours.
• Secondary osteoarthritis, myositis ossificans, recurrent dislocation (rare).

Treatment: urgent closed reduction under general anaesthesia (traction in line with the femur, hip flexed to 90°); CT afterwards to look for fragments in the joint; open reduction and fixation for irreducible dislocations, trapped fragments or large wall fractures.

Anterior dislocation

Rare; forced abduction and external rotation. Leg abducted and externally rotated, slightly flexed; head felt in the groin; femoral nerve and vessels at risk.

Central dislocation

The head is driven through the floor of the acetabulum: really an acetabular fracture (see the pelvic fractures chapter).

Femoral shaft fractures

• Usually young adults, high-energy injury. In the elderly, a shaft fracture after minor trauma suggests a pathological fracture.
• Blood loss can reach about 1.5 litres into the thigh (closed); bilateral or open fractures can cause shock.
• Muscle pull: proximal fragment flexed and abducted (iliopsoas, gluteals); distal fragment pulled up and back.
• Associations: fat embolism, ARDS, ipsilateral hip dislocation or femoral neck fracture, knee ligament injury.

Management:

1. ATLS; fluids; analgesia (femoral nerve block).
2. Traction splint (e.g. Thomas splint) in the emergency department: reduces pain, blood loss and fat embolism.
3. Definitive: locked intramedullary nail (closed, early, within 24 hours when possible); external fixation for damage control in unstable patients or severe open fractures.
4. Children: brief traction then spica cast (infants and young children; remodelling allows some angulation), flexible intramedullary nails or other fixation in older children and adolescents. A shaft fracture in a child under 2 raises concern about abuse.

Complications: shock, fat embolism, infection (open), malunion, non-union, knee stiffness, DVT.

Knee injuries

Patella fracture

• Direct blow (dashboard): comminuted (stellate).
• Indirect: violent quadriceps contraction: transverse fracture with separation; patient cannot straight-leg raise (extensor mechanism broken).
• Displaced transverse fracture: tension band wiring; undisplaced with intact extension: cylinder cast or brace.

Tibial plateau fracture

• Valgus force on the extended knee (bumper injury): lateral plateau most often.
• Schatzker classification (I-VI; I-III lateral, IV medial, V-VI bicondylar).
• Intra-articular: aim for anatomical reduction, buttress plating, bone graft for depression.
• Watch for compartment syndrome and common peroneal injury.

Knee dislocation

• High-energy; often reduces spontaneously, so may be missed.
• Popliteal artery injury is common (tethered at the adductor hiatus and soleal arch): check pulses, ankle-brachial index; if abnormal, CT angiography or exploration. An ischaemic limb needs revascularisation within about 6 hours.
• Common peroneal nerve injury (foot drop).
• Multiple ligament tears needing later reconstruction.

Soft tissue knee injuries (often tested)

Tibial shaft fractures

• The commonest long-bone fracture to be open (subcutaneous anteromedial border).
• High risk of compartment syndrome (anterior compartment).
• Distal third has a poor blood supply and little muscle cover: delayed union and non-union.
• Treatment: undisplaced closed fractures can go in an above-knee cast; displaced or unstable fractures: locked intramedullary nail; open grade III injuries: debridement, external fixation or nail, plastic cover.
• Above-knee cast: pad the fibular neck to protect the common peroneal nerve.

Ankle fractures

• Usually a twisting injury (foot fixed, body rotates).
• Ottawa rules for X-ray: tender bone along the back or tip of the lateral or medial malleolus, or the patient cannot take four steps (both at injury and in the department).

Danis-Weber classification (level of the fibular fracture)

• Unstable if both sides of the ankle ring are broken: bimalleolar, trimalleolar (with posterior malleolus), or lateral malleolus + deltoid ligament tear (medial tenderness, talar shift on X-ray).

• Maisonneuve fracture: proximal fibula fracture with ankle syndesmosis and medial injury: examine the whole leg.
• Displaced unstable fractures: reduce promptly (skin at risk), then ORIF.
• Inversion sprain commonly tears the anterior talofibular ligament; eversion injures the deltoid ligament.

Foot injuries

Nerves at risk in lower limb injuries

Quick revision

• Hip fracture: elderly woman, short externally rotated leg.
• Intracapsular displaced: AVN/non-union → hemiarthroplasty (THR if fit); young → urgent fixation.
• Undisplaced intracapsular → screws; intertrochanteric → DHS; subtrochanteric/unstable → nail.
• Posterior hip dislocation: dashboard, flexed-adducted-internally rotated, sciatic nerve, reduce within about 6 h.
• Femoral shaft: up to 1.5 L blood loss, traction splint, locked IM nail, fat embolism.
• Knee dislocation: popliteal artery and common peroneal nerve.
• Tibia: most often open; compartment syndrome; distal third non-union; IM nail.
• Ankle Weber A stable, C unstable; Maisonneuve = high fibula.
• Calcaneum: fall from height, check spine; talar neck: AVN of body; second metatarsal: march fracture.

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

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