Continuing Education Activity

Bimalleolar fractures are a type of ankle fracture that involve both the lateral and medial malleoli at the distal ends of the fibula and tibia, respectively. These two bones articulate with the talus to form the ankle or tibiotalar joint. The bimalleolar fracture accounts for 60% of all ankle fractures, with an incidence of 187 fractures per 100,000 people. This fracture is a bimodal distribution, most likely to affect older women and young males and those over 60 years old. Surgery is the primary treatment of bimalleolar fracture because it is an unstable fracture. This activity reviews the evaluation and management of bimalleolar fractures and studies the interprofessional team's role in evaluating and treating patients.

Objectives:

• Identify the etiology of bimalleolar fractures.
• Review the appropriate process for the evaluation of bimalleolar fractures.
• Summarize the management options available for bimalleolar fractures.
• Outline some interprofessional team strategies for improving care coordination and communication to advance bimalleolar fractures and improve outcomes.

Introduction

Bimalleolar fractures are a type of ankle fracture that involve both the lateral and medial malleoli at the distal ends of the fibula and tibia, respectively. These two bones articulate with the talus to form the ankle or tibiotalar joint. The ankle is supported by ligaments on both the medial and lateral sides that stabilize the foot under the leg and lock the fibula and tibia together. Bimalleolar fractures can affect these ligaments, too. Damage to the ligaments, instead of a fracture of one of the malleoli, still produces an unstable fracture that will likely need surgical intervention.[1][2][3][4]

Etiology

According to the Lauge Hansen classification: supination and external rotation injuries are the most common cause of bimalleolar fractures. Eversion is considered the most common reason which can cause all damage.[5]

Epidemiology

Ankle fractures account for 9% of all fractures. In the United States, ankle fractures are the most common lower limb fractures and are the most frequent fracture or injury in the emergency room. The bimalleolar fracture accounts for 60% of all ankle fractures, with an incidence of 187 fractures per 100,000 people. This fracture has a bimodal distribution and most commonly affects older women and young males. Ankle fracture is the third most common fracture overall; in athletes, it is the most frequently encountered fracture. Also, this is the third most frequent fracture in patients over 60 years of age.[3][2] 

History and Physical

A focused and thorough history should be obtained to identify any comorbidities or conditions that may be detrimental to healing. Important findings will include diabetes with or without peripheral neuropathy, peripheral vascular disease, osteopenia, alcohol use, tobacco use, and malignancy. Chronic medications such as corticosteroids can also cause prolonged healing. So, it is necessary to ask about medication history. These should be identified before any physical exam takes place. The patient history should investigate multiple aspects of the injury, including time from injury to presentation, pain location, and possibly the mechanism of injury. It can be helpful if the patient is able to describe the injurious event and the force directed toward the ankle, along with the intensity of this force. Higher levels of force should raise the suspicion of more complications.

On physical examination, the clinician should begin with the affected limb by examining for gross deformity and skin changes that may indicate a change in neurovascular status or open wounds that may indicate an open fracture. It is also important to examine the knee, fibula, tibia, ankle, and foot and look for any signs of fracture like swelling, redness, hematoma formation, and lateral or medial tenderness malleolus or the proximal head of the fibula. The inability to bear weight on the injured foot indicates a fracture, and palpation can identify the fracture's exact location.

The clinician must ensure that the foot and ankle's neurovascular state is intact, including palpating pedal pulses and assessing the motor function, sensation, capillary refill time, and pulses at the injury site. Examine both the active and passive range of motion of the joint, as well as weight-bearing status. Also, assess if there are any signs of open wounds or compartment syndrome.[1][7][11]

Anatomy

The ankle joint is in the mortise and tenon joint classification. As stated above, the ankle is composed of the tibia, fibula, and talus articulating with each other, and these articulations are supported by strong ligamentous support on either side. The medial collateral ligament, or deltoid ligament, is a triangular-shaped ligamentous complex composed of 4 ligaments that stabilize the medial aspect of the ankle by anchoring the tibia to the foot. These four ligaments are named the anterior tibiotalar ligament, posterior tibiotalar ligament, tibiocalcaneal ligament, and tibionavilcuar ligament, and they are divided into two portions: superficial and deep.[6]

The superficial fibers extend from the medial malleolus to the navicular, sustentaculum tali of the calcaneus and the talus. The deep portion is the strongest portion and extends from the medial malleolus to the talus. The deltoid ligament is the most common ligamentous injury during the medial malleolar fracture, causing joint instability. When the deltoid ligament ruptures instead of the medial malleolus fracturing during a bimalleolar ankle fracture, it is known as a "bimalleolar equivalent" fracture.[7] The most common mechanism of injury that damages this ligament is foot eversion or an external rotation force due to the intense medial stresses these forces produce.

The lateral collateral ligaments are composed of three ligaments: the anterior talofibular ligament (ATFL), calcaneofibular ligament (CFL), and posterior talofibular ligament (PTFL). These secure the lateral aspect of the ankle by anchoring the fibula to the foot. These ligaments restrict inversion and internal rotation forces.[8]

The syndesmosis is a long interosseous membrane that holds the fibula and tibia together and is composed of 4 ligaments at its most distal end. These ligaments are the anterior inferior tibiofibular ligament (AITFL), the posterior inferior tibiofibular ligament (PITFL), the inferior transverse ligament, and the interosseous ligament, which is the most distal aspect of the interosseous membrane itself. These ligaments hold the fibular within the incisura of the tibia and help keep the integrity of the ankle joint. Syndesmotic tears or sprains can result from hyper-dorsiflexion trauma and rotational injuries.[9][4][5][6][7][8]

Evaluation

According to the Ottawa Ankle Rules, the clinician should not order ankle radiographs unless there is pain or tenderness in the ankle malleoli along with one of the following:

• The presence of tenderness at the tip of lateral or medial malleolus within or 6 cm above these structures
• Patients should not be able to bear their weight after the injury weight-bearing.

Radiological Features

Plain-film Radiographs

Ankle X-ray is the best initial investigation, requiring three views:

• Anterior-posterior view: assesses the soft tissue swelling and checks for any subtle fractures.
• Mortise view: this view is done by putting the foot in 15 to 20 degrees of internal rotation. It evaluates the talus positioning and the syndesmosis widening.
• Lateral view: serves to assess fractures in the lateral view and for determining any effusion in the ankle joint

Sometimes the tenderness is present in the proximal leg in addition to the widening of the syndesmosis, without obvious fracture in the ankle; however, there is a fracture in the proximal fibula. It provides a clue to the rupture of the syndesmosis. This presentation calls for a radiograph of the proximal tibia and fibula to diagnose a specific injury called a Maisonneuve fracture, which is a spiral fracture in the proximal third of the fibula.

Usually, weight-bearing films, if possible, are the best option to diagnose syndesmotic injuries.

CT

• CT is mostly for potential posterior malleolar fractures and to give an idea about the degree of impact. 

MRI

• MRI is only indicated to assess soft tissues, i.e., cartilage or ligament injuries.  

Ultrasound

• Ultrasound is also sometimes useful for ligament assessment, but the results are user-dependent[1][10][11]

Classifications

The most common classification systems used to explain ankle fractures are the Lauge-Hansen and Danis-Weber systems. Each has its uses in classifying these fractures to identify the best way to treat the injury.

The Lauge-Hansen classification attempts to identify the fracture pattern based on the motion of the talus in the ankle joint. The classification system is broken into four groups: supination-adduction, pronation-abduction, supination-external rotation, and pronation-external rotation. Each mechanism of injury is associated with specific fracture patterns.[12]

The Danis-Weber divides the lateral malleolus into three distinct areas and classifies the fracture of the lateral malleolus based on where the fibula was fractured. This classification is more basic and is more relevant when it comes to operative decision-making.[12]

Treatment / Management

In treatment, assessment of the patient and the injury should proceed systematically according to ATLS guidelines. The primary survey should come first, ruling out any life-threatening injuries. Then, the examiner can manage the ankle fracture, first checking if there is any neurovascular damage that requires an urgent ankle reduction to regain the foot's vascularity and to avoid long-term sequence. A skin integrity examination is essential because open fractures can be treated primarily by external fixators. Open fractures can lead to delayed union, infection, and skin necrosis. 

Most bimalleolar fractures are unstable fractures and require treatment with open reduction internal fixation (ORIF). The management plan can be for either operative or non-operative treatment.

Non-operative 

Uses a below-knee cast for six weeks or a total contact cast for three months in patients with diabetes; indicated if the fracture is stable or when the patient cannot tolerate surgical fixation. It needs repeat ankle X-rays in a week to check for any displacement. Also, patients should be on thromboprophylaxis. 

Operative

ORIF is indicated when the fracture is unstable, such as in a talar shift. The technique uses fibula fixation using plates and screws (lateral malleolus) and medial malleolus fixation using cannulated screws or tension band wiring or plate over medial malleolus in certain types of medial malleolus fractures (Lauge-Hansen supination-adduction fracture pattern). Once the medial and lateral malleoli are reduced and fixated, the syndesmosis should be inspected for injury. If there is a syndesmotic injury, syndesmotic screws should be inserted (there are some intraoperative tests to check syndesmosis integrity, one of them called the Cotton test). If the posterior malleolus fracture is more than 25%, a CT scan is necessary, and it requires posterior fixation using cannulated screws or, in some situations, plating.

In the two options, thromboprophylaxis is necessary until the patient achieves full weight bearing to avoid the risk factor of DVT.[2][13][14][15][1]

Previously, surgeons stated that a reduction of the lateral malleolus was the critical element in treating ankle fractures. Today it is accepted that the deep deltoid ligament is the primary ankle stabilizer preventing lateral talar shift and external rotation of the talus.[16]

Differential Diagnosis

• Ankle sprain
• Osteoarthritis
• Osteosarcoma
• Osteomyelitis
• Achilles rupture
• Septic arthritis
• Tendon dislocation
• Rheumatoid arthritis
• Osteoid osteoma
• Charcot joint
• Pathologic fracture
• Ewing sarcoma
• Gout

Prognosis

Depending on the patient and operation, the bimalleolar fracture can have a poor prognosis. Those at higher risk are the elderly, persons with diabetes, peripheral neuropathy, peripheral vascular disease, and tobacco users. In general, full weight-bearing takes time and can begin after 5 to 6 weeks of immobilization, but this is different for each patient depending on the severity of the injury, quality of bone, and stability of the reduction. With operative intervention, the mortality one year after the surgery is 12% in patients older than 65, increasing to 50% for patients over 95.[2][1][14][17]

Complications

Complications of a bimalleolar ankle fracture can range in severity and include wound infection, wound hematoma, delay of wound healing, dislocation, arthrosis, inadequate reduction, complex regional pain syndrome, compartment syndrome, impingement syndrome, limited range of motion, malunion, malunion, and Charcot arthropathy, mainly in diabetic patients. The long-term complications include deformity, infection, ulceration, ankle osteoarthritis, and amputation. Until the patient reaches full weight-bearing, they must take thromboprophylaxis to prevent the development of DVT or pulmonary embolism.[1][15] 

Postoperative and Rehabilitation Care

Depending on the patient's age, bone density, and comorbidities, bone healing can take between 4 to 8 weeks. Most patients are not weight-bearing for at least four weeks after surgery. Older patients may require a skilled nursing facility or rehab. After a period of non-weight-bearing, patients are typically able to walk in a CAM (controlled ankle motion) boot and begin physical therapy. Full recovery tends to take six months or more. Lower extremity swelling can last for up to 1 year after surgery.

Consultations

• Orthopedic Surgeon
• Podiatrist
• Emergency Physician
• Physical Therapists
• Nurses (pre-op, post-op, home health)

Deterrence and Patient Education

In patients with bimalleolar ankle fractures, since many patients are under surgical management, it is essential to educate them about the importance of postoperative physiotherapy, which results in significant differences in treatment and weight-bearing status. Any delay in the union or struggle to achieve weight-bearing status rates is a red flag, and the patient must be aware of this point. Patients must closely adhere to postoperative instructions and therapy to achieve optimal outcomes.

Pearls and Other Issues

• Do not miss distal or proximal tibio-fibular syndesmotic diastasis. Performed stress exams under fluoroscopy
• If visible, inspect the tibiotalar joint for cartilage damage
• Use Well's Criteria to evaluate the risk of a DVT
• Avoid intra-articular placement of screws by ensuring the distal fibular screws are uni-cortical 

Enhancing Healthcare Team Outcomes

Bimalleolar ankle fracture is considered an unstable fracture, and the orthopedic team should be responsible for its management. The patient may first present to a family clinician or the ED. Managing this fracture requires open communication with the orthopedic surgeon to enhance and improve patient outcomes. Nurses can help with patient evaluation, assist during surgery and provide post-procedural patient care and counsel. Pharmacists can verify pain control mediation and antithrombotic therapy if needed. The physiotherapist's essential role is to help the patient physical health, muscle strength, and weight-bearing abilities after the surgery. The emergency team should perform emergency fracture reduction. After the surgery, all interprofessional team members should follow up with the patient to ensure a full recovery. This team includes:

• Orthopedic team
• Physiotherapy team

At home, the patient must be given thromboprophylaxis prescriptions and equipment like (walker boots, crutches, canes, etc.), and ensure that there is someone at home to help the patient till complete recovery. The interprofessional team model will drive optimal patient outcomes. [Level 5]