Bimalleolar Ankle Fracture Open Reduction and Internal Fixation

Abstract

Ankle injuries are common, occurring most often among young males and older females. The ankle joint is crucial for stability and gait, making these injuries a significant source of disability.

Ankle injuries are usually treated operatively when there is loss of joint congruity and stability, and in this video, Dr. Agarwal-Harding takes us through the operative fixation of a bimalleolar ankle fracture. He talks about understanding why operative intervention is recommended, techniques involved, and other considerations.

Keywords

Ankle injury; bimalleolar fracture; ankle fracture; bimalleolar ankle fracture.

Case Overview

Background

The ankle is a hinge-type joint made up of the tibia, fibula, and talus. It is usually described as a mortise and tenon joint that is crucial for ambulation and gait stability. Injuries to the ankle joint are common, with an estimated incidence of 4.22/10,000 person-years in the United States¹ and a bimodal peak distribution among young males and older females,² most often due to high-energy and low-energy injuries respectively.³

The ankle is stabilized medially and laterally by osseous-ligamentous structures. On the medial side, this comprises the medial malleolus of the tibia and the deltoid ligament complex. On the lateral side, this comprises the distal fibula or lateral malleolus and the syndesmosis complex. One or both complexes can be disrupted in rotational ankle injuries, either as bony disruption (fracture) or ligamentous disruption (sprain or rupture). Bimalleolar or bimalleolar-equivalent ankle fractures, which specifically involve both these medial and lateral osseous-ligamentous structures, are the most common types of ankle fractures and cause joint instability, with lateral shift of the talus.^4,5 These injuries often require operative fixation to restore joint congruency and prevent post-traumatic arthritis.⁶

Beyond the physical impact of these injuries, they also have larger economic and social implications.^7,8 Surgical repair of an ankle fracture costs an estimated $8,000–$20,000 and may require up to 3 months of lost work-hours for one patient.⁹ Additionally, there have been reports on the psychosocial impact of ankle injuries, including the need for counseling and social support as part of rehabilitation.^10,11

Focused History of the Patient

The patient is a 59-year-old woman who presented to the emergency department with right ankle pain following a fall down stairs. She had no additional injuries from this trauma. Vital signs were within normal limits. There was no other relevant past medical history.

Physical Exam

The patient was well-appearing and breathing comfortably on room air. The right lower extremity examination revealed a visibly deformed right ankle. The skin was intact with swelling over the lateral and medial ankle. She was able to grossly fire her extensor hallucis longus and extensor digitorum muscles as well as the flexor hallucis longus and flexor digitorum muscles. She had intact sensation in all peripheral nervous distributions of the foot.  There was no tenderness to palpation of the proximal fibula. Her foot was warm and well-perfused.

Imaging

Anterior-to-posterior (AP), mortise, and lateral radiographs showed a bimalleolar ankle fracture with distal fibular fracture at the level of the syndesmosis (Weber B) and a displaced medial malleolus fracture. Subsequently, the patient underwent manual reduction via a Quigley maneuver¹² and stabilization with a plaster of Paris splint in the ED.

In general, the Ottawa ankle rules are a set of evidence-based guidelines established to assist with clinical decision-making regarding whether ankle radiographs are required for a patient presenting with an ankle injury in the emergency department.¹³ While they have been widely adopted and found to streamline the use of radiographs,¹⁴ there are concerns about potentially missing serious injuries, leading to variants or modifications of these recommendations.¹⁵ The authors recommend that local orthopedic leadership customize hospital policies about who needs ankle imaging to the availability of x-ray imaging and epidemiologic or mechanism-related risk factors.

In general, the three radiographs obtained for the current patient—AP, mortise, and lateral views—are the gold standard for identifying and characterizing ankle fractures. Additional imaging may be needed to identify additional injuries commonly associated with rotational ankle injuries. In Maisonneuve fractures, the rotational injury travels beyond the ankle, up the interosseous membrane between the tibia and fibula, and exits as a proximal fibular fracture. Patients with ankle fractures should be routinely examined for proximal fibular pain, and if present orthogonal tibia-fibular imaging should be performed. It is our recommendation that patients with an isolated medial malleolus fracture or isolated medial clear space widening should have full length tibia/fibula x-rays to evaluate for a Masionneuve type bimalleolar or bimalleolar-equivalent injury.

Some rotational ankle injuries may present as fractures, ligamentous ruptures, or both. While fractures may be more obvious on radiographs, ligamentous disruption may be more subtle. These can be identified by atypical widening between bones usually tethered by the intact ligament. Some important parameters to assess in these radiographs include increased tibio-fibular clear space or decreased tibio-fibular overlap on the mortise view, which represent syndesmotic injury, as well as medial clear space widening, representing deltoid ligament injury.¹⁶

Magnetic Resonance Imaging (MRI) scans are not routinely used in the evaluation of the ankle but may be used when radiographs do not provide sufficient information when there is a high clinical index of suspicion of subtle injuries, particularly ligamentous injuries. By contrast, Computed Tomography (CT) is often used in high-resource settings to characterize complex, comminuted fractures to formulate a preoperative plan for surgical fixation.^5,17–19

Natural History

The bony, ligamentous and tendinous components of the joint all contribute to the stability of the joint and are frequently injured in rotational ankle fractures, leading to a disruption of the normal anatomy of the ankle joint and instability. It is well-known that the ankle joint is poorly tolerant of instability,²⁰ and in the absence of restoration of normal anatomy and joint congruence in a timely fashion, post-traumatic arthritis, pain, and functional limitations are likely to result.^21,22

Options for Treatment

Ankle fractures can be treated conservatively or surgically, depending on whether the fracture is stable and the patient fit for surgery. At presentation, it is important to reduce the ankle and apply a splint to maintain the reduction, emphasizing concentric reduction of the tibiotalar joint and minimizing lateral shift of the talus by reducing the medial clear space.²³ After initial stabilization and reduction, a decision can be made on which treatment modality to adopt for each patient. Conservative management may be acceptable in stable, minimally-displaced fractures and when patients are not medically fit for surgery. Bimalleolar-equivalent fractures, which are characterized by a fibular fracture and medial deltoid ligament disruption with widening of the medial clear space, and bimalleolar ankle fractures are inherently unstable and are typically treated surgically.²⁴ If a patient has severe soft tissue swelling, an initial external fixation may be placed temporarily with planned conversion to definitive open reduction and internal fixation (ORIF) once the soft tissue swelling has decreased and permits safe surgical incisions to be made without risking wound complications.^5,25

Depending on the lateral malleolar fracture morphology, the standard fixation aims to compress across the fracture site by applying a lag screw and neutralization plate or a compression plate alone.^5,26 However, there has been recent interest in intramedullary fixation of fibular fractures, especially among individuals who may not be able to tolerate more extensive soft tissue dissection, with largely positive results.^27–29 Regarding the medial malleolus, lag screws or tension band wires are typically used for fixation.³⁰ In vertical fractures, buttress plates may be utilized.⁵

Syndesmotic injury often occurs with bimalleolar fractures. This is assessed intraoperatively with the Cotton or hook test, which involves the application of a distracting force orthogonal to the distal fibular surface while watching for a widening of the syndesmotic gap under direct visualization or fluoroscopy.^31,32 A surgeon may also assess this gap on a neutral and external rotation stress mortise view under fluoroscopy.^16,31 Screws, suture buttons, and other constructs are used to repair the syndesmosis, all with favorable outcomes.^33,34 The authors recommend using whatever device is locally available and most comfortable for the performing surgeon, although screws are our implant of choice given the significantly lower cost.

Rationale for Treatment

The overarching principle guiding ankle fracture repair is to restore joint stability and achieve an anatomic reduction. In bimalleolar fractures, at least two components of the mortise construct of the joint are affected, making conservative measures such as immobilization in a cast or boot often insufficient to achieve the stability necessary to achieve adequate fracture healing. Currently, operative fixation is the recommended treatment for bimalleolar fractures, unless there are significant contraindications.²³

Special Considerations

Patients with diabetes mellitus are at a high risk of complications related to poor wound healing, slow fracture healing, and peripheral neuropathy with progressive Charcot neuroarthropathy.³⁵ In a series of 84 patients with ankle ORIF and diabetes by Costigan et al, 1 in 7 patients developed postoperative complications, the most common being infection (12%).³⁶ If absent pedal pulses or peripheral neuropathy was present, a patient was at higher risk of developing a complication. To mitigate these complications, many surgeons advocate supplemental fixation with temporary transarticular Steinmann pin placement, syndesmotic screw placement regardless of Cotton/hook test result, multiple syndesmotic screw placement, or external fixation.³⁵ In patients with complicated diabetes and complex fractures, some surgeons instead suggest primary ankle arthrodesis with a tibiotalocalcaneal intramedullary nail procedure, with outcome reports demonstrating a limb salvage rate of 96% and maintained ambulation in 81%.³⁷

Discussion

Rotational Ankle Injury Overview and Epidemiology

Ankle fractures are one of the most common orthopaedic complaints in the emergency department, accounting for more than 5 million injuries annually in the United States.¹ The Danis-Weber/AO classification was developed to help characterize fracture pattern and guide treatment: Weber A fractures occur below the level of the syndesmosis, Weber B fractures at the level of the syndesmosis, and Weber C fractures above the syndesmosis. From A to C, the risk of an associated syndesmotic injury increases; as the risk of an associated syndesmotic injury increases, the resultant instability further drives the treating physician toward operative management.³⁸ In displaced bimalleolar fractures such as the one sustained by the current patient, there is a loss of the ankle mortise, and most experts recommend ORIF of the malleoli for this injury.^38,39 The current video demonstrates one of the most common fixation constructs applied for bimalleolar fractures: interfragmentary screw and neutralization plate to fix the distal fibula and partially-threaded cannulated screws to fix the medial malleolus. Syndesmotic screws were not used due to a negative Cotton/hook test.

Treatment Considerations – Syndesmotic Fixation Constructs

The main goal of rotational ankle injury surgery is to restore joint stability. The primary drivers of ankle stability rely medially on the deltoid ligament complex and lateral on the syndesmotic ligament complex, which includes the anterior inferior tibiofibular ligament (AITFL), posterior inferior tibiofibular ligament (PITFL), interosseous ligament (IOL), and interosseous membrane (IOM).⁴⁰ The tibiofibular articulation stability is largely driven by these ligaments due to high variability in the tibial incisura. A key to reducing the syndesmosis is to restore fibular length, thus better approximating ligamentous remnants and restoring the lateral talar buttress. Patients with syndesmotic malreduction go on to have worse functional outcomes.⁴¹

Syndesmotic fixation can either be rigid or dynamic. Rigid fixation is best used in diabetic or neuropathic patients and patients with osteoporotic bone, typically with two or more tri- or quadri-cortical screws. A drawback to rigid fixation is the potential for screws to break or become symptomatic, requiring an eventual reoperation for hardware removal. Dynamic fixation, such as with a suture button, is more forgiving for minor malreductions and is a better mimic of physiologic fibular motion. Although suture buttons are initially more expensive than cortical screws, cost-effectiveness analyses find that the lower rate of hardware removal ultimately makes dynamic fixation more cost-effective than rigid fixation. A meta-analysis of level I studies suggests that the American Orthopaedic Foot & Ankle Society Score (AOFAS) at 24 months was superior in patients with dynamic fixation, while there was no difference in the Olerud Molander Ankle Score (OMAS) patient-reported outcome instrument.^42,43 However, a randomized control trial of pronation-external rotation ankle fractures with a minimum of 6 years of follow up demonstrated no differences in OMAS, questioning whether these earlier differences persist with longer term follow-up.⁴⁴

Postoperative Management and Rehabilitation

After wound closure and dressing placement, patients are placed in a short leg splint with a posterior slab holding the ankle in neutral plantar/dorsiflexion and a U-shaped slab protecting the medial and lateral ankle. This splint is for soft tissue protection and immobilization. The patient is immobilized in the splint for 2 weeks, then transitioned to a removable boot for 4–6 additional weeks, which can be removed for a gentle range of motion activities and hygiene. The patient remains non-weight bearing for 6 weeks, then gradually can bear weight as tolerated depending on fracture healing on radiographs.

Equipment

• Stryker distal fibula small fragment anatomically-contoured locking plate and screws
• Stryker Asnis 4.0-mm cannulated screws

Disclosures

None.

Statement of Consent

The patient referred to in this video article has given their informed consent to be filmed and is aware that information and images will be published online.