Fibular Shaft Fractures

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Fibular shaft fractures involve the diaphysis of the fibula. They can occur as isolated injuries (direct blow) or as part of a complex ankle or leg injury (Maisonneuve, Tibia-Fibula fracture).

Mechanism of Injury

• Direct Blow: "Nightstick" fracture. Isolated transverse fracture. Stable. This is typically sustained in contact sports like soccer or rugby where a direct kick or impact occurs to the lateral leg.
• Rotational Force: External rotation of ankle. Energy transmits through syndesmosis → proximal fibula fracture (Maisonneuve). Unstable. The medial structures (deltoid) fail first, then the syndesmosis, then the fibula.
• Axial Load: Fall from height. Usually associated with tibial fracture. The fibula fails under compression, often resulting in comminution.

Epidemiology

• Incidence: Common fracture in active adults. Fibula fractures (including malleolar) constitute a significant portion of ankle trauma.
• Isolated: Football/Soccer (direct kick) is the most common cause.
• Prognosis: Isolated = Excellent union rates. Associated = Depends on other injuries (tibial alignment, chondral damage).
• Risk Factors: Contact sports, osteoporosis in elderly. In the elderly population, fibula fractures may be part of fragility fractures of the ankle.

Anatomy

The fibula acts as a strut for muscle attachment and ankle stability, but plays a minor role in weight transmission.

• Fibula Structure: Long, slender bone. The head is proximal, articulating with the tibia. The neck is just distal to the head (nerve risk). The shaft is triangular in cross-section. The distal end forms the lateral malleolus.
• Weight Bearing: The fibula bears approximately 6-17% of the body's load. This minimal load-bearing allows for fibular resection (e.g., for bone grafts) without significant functional deficit, provided the distal syndesmosis is intact.
• Interosseous Membrane (IOM): A strong fibrous sheet connecting the tibia and fibula. It provides stability for the ankle mortise and serves as an origin for muscles. The fibers run obliquely from proximal-medial (tibia) to distal-lateral (fibula), resisting distal migration of the fibula.
• Common Peroneal Nerve (CPN): The nerve winds around the neck of the fibula, passing from the popliteal fossa into the anterior and lateral compartments. It is highly susceptible to injury here from direct trauma, casts, or surgical retractors.
  • Deep Peroneal Nerve: Supplies the Anterior compartment (Tibialis Anterior, EHL, EDL). Function: Dorsiflexion. Sensation: First dorsal web space.
  • Superficial Peroneal Nerve: Supplies the Lateral compartment (Peroneus Longus/Brevis). Function: Eversion. Sensation: Dorsum of the foot (except 1st web space). Pierces the deep fascia in the distal third of the leg.
• Syndesmosis: The distal tibiofibular joint is maintained by the Anterior Inferior Tibiofibular Ligament (AITFL), Posterior Inferior Tibiofibular Ligament (PITFL), Transverse Ligament, and the distal IOM. It prevents diastasis (widening) of the ankle mortise.

Vascular Supply

• Peroneal Artery: The nutrient artery typically enters the middle third of the fibular shaft.
• Periosteal Supply: The fibula receives a rich blood supply from its multiple muscle attachments (Soleus, Peroneals, Tibialis Posterior, EHL).
• Clinical Relevance:
  • The robust vascularity contributes to high union rates, even in displaced fractures.
  • The middle third of the fibula is the "workhorse" donor site for vascularized bone grafts (e.g., for mandibular or tibial reconstruction) because of its predictable pedicle (peroneal vessels).
  • The distal third has a relatively poorer blood supply, closer to the watershed area of the ankle, which can impact wound healing in surgical cases.

Pathophysiology

• Stability: The fibular shaft itself is not essential for weight bearing stability in the mid-diaphysis. However, the proximal and distal ends are critical for knee (LCL attachment) and ankle stability.
• Ankle Mortise: The Lateral Malleolus (distal fibula) acts as a buttress to prevent lateral shift of the talus. Even 1mm of lateral shift can reduce tibio-talar contact area by 42%, leading to early osteoarthritis.
• Maisonneuve Fracture: A spiral fracture of the proximal third of the fibula associated with a rotational ankle injury. The fracture line location is an indicator of the exit point of the rotational force. If the force exits proximally, it implies that the energy has traveled through the interosseous membrane and syndesmosis, rupturing them.
• Healing: The fibula has a rich muscle envelope (peroneals, soleus, tibialis posterior) which provides excellent blood supply. Non-union is rare. Malunion is generally well tolerated unless it affects the ankle mortise.

History

• Mechanism: Was it a direct blow (e.g., hockey stick, kick)? This suggests an isolated fracture. Was it a twisting injury? This suggests a rotational component and possible syndesmotic injury.
• Pain: Location of pain is key. Mid-calf pain vs Ankle pain. Patients with Maisonneuve fractures may complain only of ankle pain and the proximal fibula tenderness is missed if not palpated.
• Ambulation: Patients with isolated fibula fractures can often bear weight, though painful. Patients with unstable syndesmotic injuries usually cannot.

Physical Examination

• Inspection: Look for deformity, swelling, and bruising. Note any skin tenting or open wounds (rare in isolated fibula). Look specifically for medial ankle bruising ("ecchymosis").
• Palpation:
  • Fibula: Palpate the entire length. The "Squeeze test" (compressing tibia and fibula together at mid-calf) causing distal pain suggests syndesmosis injury.
  • Medial Ankle: Tenderness over the deltoid ligament or medial malleolus is the "red flag" for Maisonneuve.
  • Syndesmosis: Tenderness over the AITFL (anterior ankle).
• Neurovascular Status:
  • Motor: Check Dorsiflexion (Tib Ant) and Great Toe Extension (EHL) for Deep Peroneal Nerve. Check Eversion (Peroneals) for Superficial Peroneal Nerve.
  • Sensory: Check first web space (Deep) and dorsum of foot (Superficial).
  • Pulses: Dorsalis Pedis and Posterior Tibialis.
• Knee: Always assess the knee to rule out associated injuries (LCL, PLC) or proximal tib-fib joint dislocation.

Missed Syndesmosis

Leading cause of poor outcome in "isolated" fibula fractures. Results in chronic instability, Talar shift, and early post-traumatic arthritis. Requires reconstruction with graft (e.g., semitendinosus) or arthrodesis if late degeneration occurs.

Compartment Syndrome

Check in high-energy injuries or crush injuries. Be vigilant in "tight" leg compartments (Anterior/Lateral). Pain out of proportion to injury, pain with passive stretch of toes. Isolated fibula compartment syndrome is rare but can occur with direct crush.

superficial Peroneal Nerve Entrapment

• Pathology: The Superficial Peroneal Nerve (SPN) pierces the deep fascia in the distal third of the leg, making it vulnerable to tethering in fracture callus or surgical scar tissue.
• Risk: Higher risk with lateral approaches or percutaneous pin placement.
• Presentation: Patients complain of burning pain over the dorsum of the foot, often exacerbated by inversion and plantarflexion (stretching the nerve).
• Signs: Positive Tinel's sign over the scar/fracture site. Sensation may be altered in the dorsal font.
• Management: Desensitization massage, Gabapentin. Surgical neurolysis is reserved for refractory cases.

Complex Regional Pain Syndrome (CRPS)

Can occur after any ankle trauma. Early mobilization and Vitamin C may reduce risk.

Nerve Injury

The Superficial Peroneal Nerve is at risk during lateral approaches (distal third), and the Common Peroneal Nerve is at risk during proximal approaches or from the injury itself. Symptomatic neuromas may require surgical excision.

Non-Operative (Isolated)

• 0-2 Weeks: Boot, WBAT with crutches for comfort. Elevate to reduce swelling.
• 2-6 Weeks: Wean boot. Transition to supportive shoe/brace. Start Physio for ROM (Ankle alphabet) and strengthening (Peroneals/Calf).
• 6+ Weeks: Return to impact activities as pain allows. Most patients return to full sports by 8-12 weeks.
• Milestones:
  • Full weight bearing without pain.
  • Equal ankle dorsiflexion/plantarflexion.
  • Ability to perform single leg hop.

Operative (Syndesmosis)

• 0-2 Weeks: Non-weight bearing (NWB) cast/splint using crutches. Elevation. Wound check at 2 weeks.
• 2-6 Weeks: NWB in tall boot. Range of Motion exercises allowed (Active dorsiflexion/plantarflexion). Avoid external rotation. Protocol varies widely: Suture buttons (TightRope) often allow earlier weight bearing (e.g., WBAT at 2 weeks) compared to rigid screws.
• 6-12 Weeks: Progressive weight bearing. Proprioception training (wobble board). Strengthening (theraband).
• Hardware Removal:
  • Rigid Screws: Traditionally removed at 3-4 months before full unrestricted activity to prevent screw breakage. Activity is restricted until removal and then screw holes heal (6 weeks).
  • Suture Buttons: Stay in permanently unless symptomatic (knot irritation). No activity restriction once healed.

Rehabilitation Protocol Details (Syndesmosis)

• Phase 1 (0-6 Weeks): Protection and Edema Control
  • Goals: Heal soft tissues, protect fixation.
  • Exercises: Toe curls, Knee ROM, Hip strengthening (Straight Leg Raises).
  • Precautions: No weight bearing (for screws). No external rotation torque.
• Phase 2 (6-10 Weeks): Mobility and Strength
  • Goals: Restore full ROM, normalize gait.
  • Exercises: Calf stretching (gastroc/soleus), Ankle 4-way theraband strengthening, Stationary bike (low resistance).
  • Proprioception: Single leg stance eyes open/closed.
• Phase 3 (10+ Weeks): Return to Function
  • Goals: Power, Agility, Sport-specific skills.
  • Exercises: Heel raises (bilateral to single), Plyometrics (box jumps, hopping), Running progression (Walk-Jog-Run).
  • Testing: Hop test (greater than 90% of contralateral side) required for cleared return to play.

Isolated Fibula

• Excellent. 95%+ of patients return to pre-injury level of activity.
• Rapid healing. Pain resolves by 3-4 months usually.
• Long-term functional deficits are rare.

Maisonneuve

• Good, if syndesmosis reduced accurately.
• Risk: Ankle arthritis if reduction is poor (fibula malreduced or syndesmosis widened).
• Stiffness: Stiffer ankle compared to isolated fractures.
• Recovery: Takes longer (6-9 months) for full sports return compared to isolated injuries.

• Protective Gear: Shin guards (Soccer) are effective in preventing direct blow fractures ("Nightstick").
• Return to Play:
  • Isolated: 4-8 weeks. Criteria: Pain-free hopping, full strength, full ROM.
  • Maisonneuve: 4-6 months. Requires solid syndesmotic healing and rehab.

Epidemiology:

• High incidence in community sports (Australian Rules Football, Rugby, Soccer).
• Direct blow injuries common (shin guards checking).

Guidelines:

• Isolated fractures managed by GP or ED with walking boot.
• Suspected syndesmosis referred to Orthopaedics.

AOANJRR:

• Ankle fracture fixation is common procedure. Metalwork removal (syndesmosis screws) is a frequent secondary procedure.