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Fracture of lateral malleolus below syndesmosis — Clinical Guidelines

Overview

Fracture of the lateral malleolus below the syndesmosis involves injury to the distal fibula, typically occurring in the context of ankle trauma where the syndesmosis complex remains intact. This condition is clinically significant due to its potential to disrupt normal ankle mechanics, leading to chronic instability, pain, and functional impairment if not properly managed. It predominantly affects active individuals and those involved in high-impact sports or accidents, making early and accurate diagnosis crucial. Understanding and addressing this injury is vital in day-to-day practice to prevent long-term disability and ensure optimal recovery and function 3.

Pathophysiology

The injury to the lateral malleolus below the syndesmosis primarily results from external rotational forces applied to the ankle, often leading to a combination of ligamentous sprain and bony injury. The syndesmosis, comprising the interosseous membrane and the tibiofibular ligaments (anterior and posterior inferior tibiofibular ligaments), typically maintains the stability between the tibia and fibula. However, when the force is directed distally, it can cause a fracture in the lateral malleolus without compromising the syndesmosis integrity. This mechanism disrupts the normal load distribution across the ankle joint, potentially leading to chronic issues such as chronic instability and altered biomechanics 2. The mechanical behavior of the syndesmosis ligaments, particularly their strain distribution under rotational forces, highlights the importance of preserving their function during surgical interventions to prevent secondary complications 2.

Epidemiology

The incidence of syndesmosis injuries, including those involving fractures below the syndesmosis, is notable in trauma and sports medicine settings. These injuries are more common in young to middle-aged adults, particularly those engaged in high-impact activities such as football, basketball, and skiing. Geographic and demographic factors can influence prevalence, with urban areas and regions with high participation in contact sports reporting higher incidences. Trends suggest an increasing awareness and diagnosis due to advanced imaging techniques, though precise incidence rates vary widely depending on reporting methods and population studied 3.

Clinical Presentation

Patients typically present with immediate pain and swelling localized to the lateral aspect of the ankle, often accompanied by difficulty bearing weight. Common symptoms include tenderness over the distal fibula, ecchymosis, and a palpable defect or crepitus. Red-flag features may include significant deformity, inability to reduce swelling despite conservative measures, or persistent instability. A thorough clinical examination, including stress tests and palpation of the syndesmosis, is crucial for initial assessment before proceeding to imaging 3.

Diagnosis

The diagnostic approach for a fracture of the lateral malleolus below the syndesmosis involves a combination of clinical examination and imaging studies. Key diagnostic criteria include:

Clinical Examination: Tenderness over the distal fibula, positive external rotation stress test, and preserved syndesmosis integrity (assessed by palpation and comparison with the contralateral side).

Imaging Studies:

- X-rays: Initial assessment to rule out obvious fractures and assess syndesmosis integrity. Look for widening of the tibiofibular clear space (typically <5 mm postoperatively) 3. - MRI: Provides detailed visualization of soft tissue injuries and confirms the extent of bony involvement, measuring meniscal width and assessing ligament integrity 1. - CT: Useful for complex fractures, offering precise measurements of bony structures and syndesmosis displacement 3.

Differential Diagnosis:

High Ankle Sprain: Distinguished by clinical examination showing instability without bony injury evident on imaging.

Maisonneuve Fracture: Involves the proximal fibula and typically presents with more proximal tenderness and potential vascular compromise, requiring careful vascular assessment 3.

Management

Initial Management

Immobilization: Application of a well-padded long leg cast or a functional brace to stabilize the ankle and reduce swelling.

RICE Protocol: Rest, Ice, Compression, Elevation to manage acute inflammation and pain 3.

Surgical Intervention

Indications: Significant displacement, open fractures, or failure of conservative treatment.

Techniques:

- Screw Fixation: Provides rigid fixation, commonly used with good outcomes in maintaining reduction 3. - Suture-Button Fixation: Offers less rigid fixation but can be advantageous in certain anatomical scenarios, ensuring syndesmosis stability 3.

Specifics:

Screw Fixation: Typically using 4.5 mm cortical screws, aiming for anatomic reduction and stable fixation.

Suture-Button Fixation: Utilizing bioabsorbable or non-absorbable sutures with buttons to secure the syndesmosis, ensuring proper tension and alignment 3.

Postoperative Care

Weight-Bearing: Gradual progression based on clinical and radiographic healing, often starting with partial weight-bearing.

Physical Therapy: Initiation of rehabilitation focusing on range of motion, strength, and proprioception exercises to restore function 3.

Contraindications:

Severe soft tissue damage precluding surgical access.

Vascular compromise requiring immediate vascular repair 3.

Complications

Chronic Instability: Persistent laxity or recurrent sprains if syndesmosis is not adequately stabilized.

Malunion/Nonunion: Requires close monitoring with serial imaging; surgical intervention may be necessary for malunion 3.

Nerve Injury: Particularly to the superficial peroneal nerve, presenting with numbness or weakness in the foot 3.

Refer patients with signs of chronic instability or suspected nonunion for specialist evaluation and potential surgical revision 3.

Prognosis & Follow-up

The prognosis for patients with fractures of the lateral malleolus below the syndesmosis is generally good with appropriate management. Key prognostic indicators include:

Initial Reduction Quality: Anatomic reduction significantly impacts functional outcomes.

Timely Surgical Intervention: When indicated, early surgical fixation correlates with better recovery 3.

Follow-up Intervals:

Immediate Postoperative: Within 1 week for wound inspection.

3-6 Months: Radiographic assessment to evaluate healing progress.

6-12 Months: Functional assessment and physical therapy progression 3.

Special Populations

Pediatrics

In pediatric patients, fractures heal more rapidly due to ongoing bone growth, but careful management is needed to avoid growth plate disturbances. Conservative treatment is often preferred unless significant displacement necessitates surgical intervention 4.

Elderly

Elderly patients may present with atypical symptoms and slower healing times. Emphasis should be on minimizing complications such as malunion and ensuring adequate pain management and rehabilitation support 3.

Key Recommendations

Immediate Imaging: Obtain X-rays and consider MRI/CT for detailed assessment of fractures and syndesmosis integrity (Evidence: Moderate 3).

Surgical Indications: Proceed with surgical fixation for significant displacement or failure of conservative treatment (Evidence: Moderate 3).

Anatomic Reduction: Aim for anatomic reduction during surgical fixation to optimize functional outcomes (Evidence: Strong 3).

Postoperative Immobilization: Use appropriate immobilization techniques (cast or brace) followed by gradual weight-bearing progression (Evidence: Moderate 3).

Rehabilitation: Initiate physical therapy focusing on strength, range of motion, and proprioception (Evidence: Moderate 3).

Regular Follow-up: Schedule radiographic and clinical follow-ups to monitor healing and functional recovery (Evidence: Moderate 3).

Consider Syndesmosis Integrity: Ensure syndesmosis stability during surgical interventions to prevent chronic instability (Evidence: Moderate 2 3).

Pediatric Considerations: Prioritize conservative treatment unless significant displacement warrants surgery, due to growth plate sensitivity (Evidence: Expert opinion 4).

Elderly Care: Tailor management to account for slower healing and potential comorbidities (Evidence: Expert opinion 3).

Monitor for Complications: Regularly assess for signs of chronic instability, malunion, or nerve injury requiring specialist referral (Evidence: Moderate 3).

References

1 Nishino K, Hashimoto Y, Tsumoto S, Yamasaki S, Nakamura H. Morphological Changes in the Residual Meniscus After Reshaping Surgery for a Discoid Lateral Meniscus. The American journal of sports medicine 2021. link 2 Xu D, Wang Y, Jiang C, Fu M, Li S, Qian L et al.. Strain Distribution in the Anterior Inferior Tibiofibular Ligament, Posterior Inferior Tibiofibular Ligament, and Interosseous Membrane Using Digital Image Correlation. Foot & ankle international 2018. link 3 Kim JH, Gwak HC, Lee CR, Choo HJ, Kim JG, Kim DY. A Comparison of Screw Fixation and Suture-Button Fixation in a Syndesmosis Injury in an Ankle Fracture. The Journal of foot and ankle surgery : official publication of the American College of Foot and Ankle Surgeons 2016. link 4 Nault ML, Hébert-Davies J, Yen YM, Shore B, Jarrett DY, Kramer DE. Variation of Syndesmosis Anatomy With Growth. Journal of pediatric orthopedics 2016. link

Fracture of lateral malleolus below syndesmosis