Maisonneuve Fracture

Maisonneuve fracture is a spiral fracture of the proximal third of the fibula associated with disruption of the distal tibiofibular syndesmosis and the deltoid ligament (or a medial malleolus fracture). The energy passes up the interosseous membrane to exit at the proximal fibula, so the ankle injury may look minor.

It is the pronation external rotation stage III or IV injury in the Lauge-Hansen classification (the tibiofibular syndesmosis and the interosseous membrane fail, and the fibula breaks proximal to the syndesmosis). It accounts for about 1 to 7% of ankle fractures.

It is frequently missed because the knee and proximal leg are not imaged. Complications are chronic syndesmotic instability, ankle arthritis, malunion of the fibula, peroneal nerve injury (the nerve winds around the fibular neck), compartment syndrome and venous thromboembolism.

Pathophysiology.

An external rotation force on a pronated foot tears the deltoid ligament (or fractures the medial malleolus), then the anterior inferior tibiofibular ligament, then the interosseous membrane to the level of the fibular fracture, and finally the posterior ligament or a posterior malleolus fragment. The talus is free to shift laterally.

Medial ankle pain, swelling and bruising with inability to bear weight, and tenderness over the deltoid ligament. The key finding is tenderness over the proximal fibula and along the leg. Examine the knee and the lateral leg in all ankle injuries.

Check the common peroneal nerve (foot drop, sensation over the dorsum of the foot and first web space) and the neurovascular state. Squeeze the calf and test external rotation of the foot (the syndesmosis stress test).

• Ankle radiographs: anteroposterior, mortise and lateral views. A widened medial clear space (over 4 mm), a widened tibiofibular clear space (over 6 mm), a fracture of the medial malleolus or posterior malleolus, and a loss of tibiofibular overlap.
• Full length tibia and fibula radiographs, including the knee, to show the proximal fibular fracture.
• Weight bearing or stress radiographs of the ankle when the findings are equivocal.
• CT or MRI for syndesmotic injury, posterior malleolus fragments and osteochondral lesions.

Differential diagnosis.

• Isolated deltoid ligament rupture and Weber C ankle fracture.
• Bimalleolar ankle fracture and trimalleolar ankle fracture.
• Fibular shaft fracture and syndesmotic sprain.
• Tibial plateau fracture.

Initial management. Reduce any ankle dislocation, apply a well padded backslab with the ankle neutral, elevate the leg and check the neurovascular state. Immobilise the knee and leg when there is a proximal fibular fracture. Treat pain and skin tension.

Definitive treatment. The injury is unstable and needs surgery to restore the syndesmosis.

• Reduce and fix the syndesmosis with one or two syndesmotic screws (3.5 mm, 3 or 4 cortices) placed 2 cm proximal to the joint with the ankle neutral and the fibula reduced into the incisura, or suture button devices.
• The proximal fibula is usually not fixed, because restoring the syndesmosis allows it to heal. Fix a fibular fracture that is displaced or involves the distal third.
• Repair or fix the medial malleolus (two 4.0 mm cancellous lag screws) or the deltoid ligament if the joint cannot be reduced. Fix an unstable posterior malleolus fragment.
• Intraoperative stress test (the hook test and external rotation stress under fluoroscopy) confirms stability.
• Postoperative: backslab then boot. Non-weight bearing for 6 weeks, then progressive weight bearing and physiotherapy. A syndesmotic screw may be removed after 3 months if painful, though this is not routine.
• Non-operative care applies only to a stable injury (a rare finding) or patients unfit for surgery, with a short leg cast for 6 weeks.

Operative antibiotic prophylaxis. Cefazolin 2 g intravenously (3 g when weight is 120 kg or over) within 60 minutes before incision as a single dose (repeat after 4 hours or blood loss over 1500 mL); with severe penicillin allergy, vancomycin 15 mg/kg intravenously starting 90 to 120 minutes before incision as a single dose, with levels and creatinine checked in prolonged cases.

Thromboprophylaxis. Enoxaparin 40 mg subcutaneously once daily for the period of immobilisation and restricted weight bearing (usually 4 to 6 weeks) in patients with a lower limb cast or non-weight bearing, started within 24 hours of injury or after surgery (20 mg once daily at creatinine clearance under 30 mL/min; adjust by anti-Xa level in obesity and renal impairment; check the platelet count on days 5 to 14 for heparin induced thrombocytopenia). Add mechanical prophylaxis as needed.

Analgesia.

• Paracetamol 1 g orally every 6 hours as needed for up to 5 to 7 days (maximum 4 g daily; 3 g daily when weight is under 50 kg, with chronic alcohol use or hepatic impairment).
• Ibuprofen 400 mg orally every 8 hours with food for up to 5 days (maximum 1200 mg daily); avoid with eGFR under 30 mL/min/1.73 m2, peptic ulcer, heart failure or anticoagulant use.
• Oral morphine 5 to 10 mg every 4 hours as needed for severe pain for up to 3 days (start 2.5 to 5 mg with age over 75 or eGFR under 30 mL/min/1.73 m2; avoid exceeding 60 mg in 24 hours without senior review); monitor sedation and respiration and prescribe a laxative.

Monitoring. Neurovascular status, peroneal nerve function and compartments every 4 hours for 24 hours. Radiographs after fixation, at 2 weeks, 6 weeks, 3 months and 12 months. Syndesmotic alignment, ankle range and gait at each visit. Late arthritis and syndesmotic widening on follow up.

Referral and escalation. Refer every Maisonneuve injury to orthopaedics within 24 hours. Emergency referral for a pulseless or dislocated foot, open fracture, peroneal nerve palsy that progresses, or compartment syndrome.

Special groups.

• Older adults: osteoporotic bone and poor skin raise the risk of failure of fixation; use suture button devices or screws with care, and assess bone health.
• Diabetes: higher risk of infection, wound breakdown and Charcot arthropathy; longer non-weight bearing (8 to 12 weeks).
• Children: rare; consider a plastic deformation of the fibula.
• Kidney impairment: avoid ibuprofen and reduce morphine doses.