Master in 5 Minutes! Key Technical Points for Open Reduction and Internal Fixation of Bimalleolar Ankle Fractures

From simple falls from standing height to high‑energy injuries such as motor vehicle accidents, the complexity of ankle fracture management varies widely due to the diverse presentations. Moreover, the ankle is a highly congruent hinge joint that tolerates malreduction poorly. As little as 1 mm of tibiotalar displacement increases the overall joint contact stress by 40%, significantly elevating the risk of post‑traumatic arthritis. With this in mind, each ankle fracture must be carefully evaluated for its fracture characteristics and patient‑specific factors, including bone quality, comminution, associated injuries, and the soft‑tissue condition around the injured ankle.

Most ankle fractures can be classified using the Lauge‑Hansen system, which describes several injury patterns and allows inference of the energy transmission that caused the fracture. Within each subgroup, the bones or ligaments are damaged in a predictable, similar pattern, thus requiring a consistent treatment strategy. This article focuses on bimalleolar fractures of the supination‑external rotation type, which account for approximately 75% of all ankle fractures. Traditionally, both the lateral and medial malleoli require anatomical reduction and fixation to restore joint integrity. If syndesmotic instability is present, syndesmotic fixation is then performed.

I. Preoperative Planning

In cases of difficult reduction or suspected syndesmotic injury, radiographs of the uninjured contralateral ankle are very useful for surgical planning. These films should include anteroposterior (AP), lateral, and mortise views. If intraoperative reduction is questionable, these images help the surgeon assess the restoration of length, rotation, the mortise, and the syndesmosis.

For posterior malleolar fractures, Chaput tubercle fractures, and osteochondral lesions (OCD) that require surgical treatment, radiographs should be carefully reviewed. When the size or orientation of a posterior malleolus or Chaput fragment is uncertain, CT can provide detailed information about the articular surface and fracture characteristics. If operative treatment is indicated, the appropriate surgical approach should be selected on a case‑by‑case basis.

Before anaesthesia is initiated, the surgical skin incisions should be inspected for fracture blisters, excessive swelling, or other skin lesions that may increase the risk of postoperative infection or compromise surgical safety. Surgery may be appropriately delayed until the soft tissues have healed satisfactorily—including resolution of fracture blisters, epithelialisation of abrasions, and the appearance of skin wrinkles over the planned incision site, indicating that oedema has subsided.

Patient‑related factors should be considered during planning. Those with significant comorbidities, a history of poor wound healing, or pre‑existing soft‑tissue injuries should be regarded as high‑risk for implant infection or fixation failure. Modifying the fixation strategy—for example, using external fixation or intramedullary devices—can reduce implant‑related risks. The anaesthesia team should administer prophylactic antibiotics preoperatively.

II. Surgical Technique

(A) Lateral Malleolus

The fibula is exposed through a direct lateral approach. Before incision, palpate and mark the distal third of the fibula with a skin marker. After exsanguination, inflate the tourniquet to 250 mmHg or 100 mmHg above systolic blood pressure. A midline incision is then made over the fibula, centred over the fracture and extended as proximally and distally as needed to allow direct plate application (Figure 2). If the fracture cannot be palpated, fluoroscopy can be used to localise it. The skin and subcutaneous tissues are sharply incised with a scalpel. Cautery is wisely used for superficial bleeding. Thereafter, blunt dissection with Metzenbaum scissors is performed over the distal fibular surface, creating an extraperiosteal plane that is extended proximally. Careful examination of the soft tissues is necessary because the superficial peroneal nerve (SPN) lies nearby. The SPN courses from posterior to anterior over the fibula, approximately 5 cm proximal to the ankle joint or 7 cm proximal to the fibular head. If the fibular fascia is intact, it is sharply divided. The peroneal muscles and tendons are retracted posteriorly. When the SPN is encountered, it should be carefully mobilised from the surrounding soft tissues so that it can be lifted superiorly if needed without tension. The nerve should be protected throughout the procedure.

(Figure 2)

The fracture site is then debrided. Use a dental hook, periosteal elevator, small rongeur, curette, and irrigating syringe to remove haematoma and any necessary soft tissue. Avoid damaging the tips of bone cortices, as they are crucial for reduction. Use a scalpel to remove 1–2 mm of periosteum from the cortical edges at the fracture site to visualise cortical reduction. Posterior and medial bone spikes often pierce the soft tissues and impede reduction. When working anteriorly, carefully expose the fracture site to avoid avulsing the syndesmotic ligaments, which are commonly attached to the fracture fragments. If dissection and mobilisation of fragments are necessary, they must be performed gently.

Once the fracture site is mobile, reduction can be achieved using various techniques. For oblique fractures, depending on bone quality, a toothed reduction clamp or pointed reduction forceps may be used. The surgeon gently grasps the two ends of the fracture at equal distances from the fracture line and combines pronation/supination and ulnar/radial deviation movements to reduce and restore length. Traction and external rotation of the foot usually facilitate mobilisation of the distal fragment. However, this manoeuvre can be complex and may jeopardise the delicate reduction, so care must be taken to avoid comminution.

For transverse fractures, two toothed clamps can be used for manual reduction. If simple traction fails to reduce the fracture shortening, a push‑pull technique can be employed: secure the plate with two screws to the distal fragment, then place a unicortical screw in the proximal hole of the plate. Thereafter, a distractor is applied over the plate to distract the fracture site, restoring length and achieving reduction. If the fracture cannot be reduced, it is important to carefully review the intraoperative fluoroscopic images to identify the cause of obstruction. Sometimes the medial gutter or the tibiofibular interval needs to be cleared, as soft tissue or bone interposition may hinder reduction.

After reduction, the choice of fixation depends on multiple factors such as bone quality, comminution, soft‑tissue envelope, and patient‑related factors. Generally, oblique fractures are treated with lag screws and a neutralisation plate or a posterior antiglide plate; transverse fractures with a compression plate; and comminuted fractures with a bridge plate. During fixation, the surgeon should allow empty screw holes in case later syndesmotic screws need to be placed from the lateral side.

In supination‑external rotation injuries, the fracture is oblique and can be addressed with a lateral plate or a posterior antiglide plate. When using a lateral plate, a lag screw is first placed independently, usually from anterior to posterior, perpendicular to the fracture line. For an antiglide plate, a lag screw is placed through the plate, also perpendicular to the fracture line, but in a posterior‑to‑anterior direction. This is accomplished using an AO technique with a 3.5‑mm lag screw: drill the near cortex with a 3.5‑mm drill bit, then insert a 2.5‑mm soft‑tissue guide into the drill hole; drill the far cortex with a 2.5‑mm drill bit; insert an appropriate 3.5‑mm cortical screw through the track until the head is fully seated. For small fragments, a 2.7‑mm lag screw with appropriate drills can be used. Alternatively, if the initial lag screw purchase is insufficient, a 4.0‑mm partially threaded cancellous screw can be used as a salvage option.

When using a lateral plate, the distal screws must be unicortical to avoid penetrating the distal tibiofibular joint. These distal screws are usually 4.0‑mm fully threaded cancellous screws. The remaining screws in the plate are typically 3.5‑mm (Figure 3).

(Figure 3, from clinical case)

(B) Medial Malleolus

A longitudinal incision is made along the midline of the medial aspect of the tibia, extending 1–2 cm distal to the tip of the tibia to allow access to the anterior colliculus of the medial malleolus. The skin is sharply incised, but care must be taken not to cut too deeply, as the saphenous neurovascular bundle runs deep below the incision. Blunt dissection is used to identify the neurovascular bundle, which is mobilised and retracted anteriorly. The fracture site is then sharply incised. The fragment can be turned over with a dental hook to inspect the articular surface of the talar dome. These fragments are often small and reduction may be difficult; fluoroscopy is essential for adequate reduction. AP and lateral views of the tibiotalar joint should be used to assess reduction.

For proper reduction, soft tissue and haematoma at the fracture site must be adequately cleared. Periosteum often becomes interposed and hinders reduction; it should be cleared similarly to the lateral malleolus. Care must be taken to protect the structures posterior to the medial malleolus—namely the posterior tibial tendon and the neurovascular bundle. Use a dental hook or pointed reduction clamp to sharply remove 2 mm of periosteum from both fracture ends to visualise cortical reduction. Maintain reduction with a 0.062‑in K‑wire or pointed reduction forceps. If using reduction forceps, create an auxiliary hole in the proximal tibial metaphysis to provide a point for the forceps; place the other tip on the apex of the anterior colliculus. Once fluoroscopy confirms reduction, proceed with fixation.

The choice of fixation for the medial malleolus depends on fracture and patient characteristics. A popular technique is to place two screws retrograde into the tibial metaphysis. On the lateral view, these screws should be parallel to each other; on the AP view, they should be inclined along the tibial axis and as perpendicular to the fracture line as possible (Figure 4).

(Figure 4, from clinical case)

Care must be taken to avoid the articular surface when inserting screws. The anterior screw should be placed in the anterior colliculus; the second screw should not be placed more posterior than the centre of the intercollicular groove to avoid injury to the posterior tibial tendon (Figure 5). The screws used are typically 4.0‑mm partially threaded cancellous screws, 40–50 mm in length, adjusted individually. Some surgeons avoid routinely using washers because they may protrude and irritate soft tissues, impairing fracture compression.

(Figure 5, from clinical case)

For osteoporotic bone or fractures where only one screw can be placed, consider additional anti‑rotational K‑wires or bicortical fixation. A 3.5‑mm cortical screw can be placed across the fracture to engage the posterolateral tibial cortex. In vertical medial malleolar fractures, the AO technique advocates a buttress plate, which can be a 3.5‑mm plate or a small fragment plate. For fragments too small for screw fixation, tension‑band wiring or a small locking plate may be used.

(C) Syndesmosis

Approximately 10% of all ankle fractures are associated with syndesmotic injury. After stabilisation of the ankle fractures, the syndesmosis should be assessed intraoperatively. Evaluation is typically performed using the Cotton test or the external rotation stress test. The Cotton test (or modified Cotton test) involves applying a direct lateral force to the fibula using a bone hook to create distal tibiofibular separation. Widening of more than 1–2 mm on fluoroscopy indicates syndesmotic injury. The external rotation test applies an external rotational force to the foot while stabilising the leg, increasing tension on the distal tibiofibular joint; again, widening is assessed. An external rotation fluoroscopic view may demonstrate widening of the medial clear space, indicating syndesmotic injury (Figure 6).

(Figure 6, from clinical case)

When syndesmotic injury is present, fixation can be achieved using suture‑button devices or screws from lateral to medial. If a lateral fibular plate is used, it can also serve for syndesmotic fixation. A large pointed reduction clamp is placed across the distal tibiofibular joint—one tine on the distal tibia and one on the fibula. Under clamp compression, the syndesmosis is reduced. Accurate reduction should be confirmed by comparison with preoperative contralateral radiographs. In the absence of preoperative images, the distal fibula should lie anterior to the posterior border of the tibial epiphysis on the lateral view. During reduction and fixation, the heel must not rest on the bed, as this can cause anterior translation of the talus and potential syndesmotic malreduction. Although controversial, fixing the syndesmosis with the ankle in dorsiflexion may help avoid overtightening.

The method of syndesmotic fixation varies, with no clear superiority of one technique. Some surgeons prefer suture‑button fixation or a single 3.5‑mm screw through four cortices; others advocate two 3.5‑ to 4.5‑mm screws through three or four cortices. Screws are best placed approximately 2 cm proximal to the tibiotalar joint and parallel to the joint line (Figure 7). If a lateral fibular plate is used, the screws or buttons should pass through the plate; however, the lateral malleolar lag screw may interfere with plate placement. Screws or buttons should be directed anteriorly at an angle of 25° to 40° to engage the tibia. When using suture buttons, leave approximately 1–2 cm of suture length to allow the knot to lie flat on the bone; excessive length may cause local soft‑tissue irritation.

(Figure 7, from clinical case)

After copious irrigation, the medial and lateral wounds are closed in a standard fashion. Ensure adequate soft‑tissue coverage over the implants, especially laterally over the peroneal tendons and fascia. Finally, the skin and subcutaneous tissues are closed.

III. Summary of Key Technical Points

1. Carefully identify the superficial peroneal nerve during the lateral approach.

2. Meticulously clear soft tissue around the fracture as needed; if reduction is difficult, consider further exposure and debridement.

3. Protect the fibula during reduction to avoid iatrogenic comminution.

4. If the lateral fracture cannot be reduced, assess the need to clear the tibiofibular interval or the medial/lateral gutters.

5. Avoid placing medial malleolar screws from the posterior aspect to prevent injury to the posterior tibial tendon and neurovascular bundle.

6. When placing syndesmotic screws, elevate the distal leg with a towel roll or similar support to allow your hand to descend to the appropriate angle and prevent malreduction.