What is the recommended treatment for a patient with an avulsion fracture of the fibula?

Management of Fibular Avulsion Fracture

For a patient with an avulsion fracture of the fibula, treatment depends critically on fracture stability: stable, minimally displaced fractures (<2mm displacement, medial clear space <4mm) should be managed conservatively with immediate weight-bearing as tolerated in a removable boot, while displaced fractures (>2mm), those with ankle mortise instability, or fragments causing chronic pain warrant surgical fixation to prevent chronic ankle instability.

Initial Assessment and Imaging

• Obtain standard three-view ankle radiographs (anteroposterior, lateral, and mortise views) including the base of the fifth metatarsal 1
• Weight-bearing radiographs are preferred when possible to assess dynamic stability, as the most important criterion in treatment of malleolar fractures is stability 1
• Consider an anterior talofibular ligament view radiograph in children with lateral ankle sprain, as this special view identifies occult fibular avulsion fractures in 26% of cases not seen on traditional three-view radiographs 1
• If the fragment appears at the tip of the fibula on standard views, obtain special oblique views to confirm the true origin of the fragment 2

Stability Criteria

A medial clear space of <4mm confirms stability and indicates conservative management is appropriate 1, 3

Indicators of instability requiring surgical consideration include 1, 3:

• Displacement >2mm
• Medial tenderness, bruising, or swelling
• Fibular fracture above the syndesmosis
• Bi- or trimalleolar fractures
• Open fracture or high-energy mechanism
• Increased displacement under varus stress 4

Conservative Management (Stable Fractures)

For nondisplaced or minimally displaced fractures with maintained joint congruity:

• Use crutches for the first 10 days maximum if needed for pain and edema control, as short-period immobilization decreases pain and swelling while improving functional outcomes 5
• Transition to immediate weight-bearing as tolerated in a removable boot after the initial 10-day period 5, 3
• Continue the cam boot for a total duration of 4-6 weeks from injury 5
• Avoid immobilization beyond 6 weeks, as this results in suboptimal outcomes including stiffness and delayed recovery 5

Critical Conservative Management Pitfalls

• Do not keep patients non-weight-bearing on crutches for the full 4-6 weeks—this represents outdated management that delays recovery 5
• Avoid rigid casting for 4+ weeks, as this produces worse functional outcomes than the cam boot approach 5
• Obtain follow-up radiographs to detect late displacement that may occur after initial conservative management 3

Surgical Management

Surgery is indicated when:

• Displacement exceeds 2mm 3
• Ankle mortise instability is present 3
• Fragment causes chronic pain despite conservative treatment 6
• The fragment increases displacement under varus stress 4

Surgical Technique and Findings

• Both the anterior talofibular ligament (ATFL) and calcaneofibular ligament (CFL) are typically attached to the avulsion fragment 4
• Average fragment size is 6.3mm (width) by 5.2mm (length) 4
• Motion between the fragment and fibula prevents spontaneous healing, making fixation critical 4
• Screw fixation of the fragment to the fibula is the standard approach 4, 7
• For very small fragments where fixation is not possible, a modified Gould-Broström procedure with anchor sutures can be performed 7
• Concomitantly address ankle instability when present during surgical treatment 6

Surgical Outcomes

• Primary fixation prevents rotational instability and efficiently restores function and stability 4
• Surgical treatment generally results in substantial improvement in clinical and radiographic outcomes with relatively low complication rates 6
• Clinical outcomes may not be affected by the presence of ankle instability or fragment size 6

Special Considerations

Pediatric Population

• Chronic ankle instability in children can result from dysfunctional lateral ligamentous complex as a consequence of bony avulsion nonunion 7
• Fractures that fail to unite result in dysfunction of the ATFL with consequent chronic ankle instability 7
• MRI should be requested for pediatric patients with suspected avulsion fractures 7

Associated Injuries

• This avulsion fracture is pathognomonic of rupture of the superior peroneal retinaculum with or without peroneal tendon displacement when associated with calcaneus, talus, or other ankle fractures 8
• Recognition and proper management of underlying peroneal tendon pathology by immobilization or surgery may prevent future tendon dysfunction 8
• Check for cartilage lesions in the lateral talus, which occur in some cases 4

Rare Variant

• Although fibular avulsion fractures are common, ATFL avulsion from the talus (rather than fibula) is extremely rare but should be considered when a fragment is seen at the tip of the fibula 2

Post-Treatment Rehabilitation

• After immobilization period, gradual return to weight-bearing activities with supportive footwear is recommended 5
• Rehabilitation should include early physical training, muscle strengthening, and balance training 3
• Physical therapy to restore range of motion and strength is beneficial 5
• Avoid premature return to high-impact activities before adequate healing 5

High-Risk Populations

Patients with diabetes, neuropathy, or osteoporosis require more cautious management with longer immobilization periods 3