Figure 1.1
Anteroposterior (a), mortise (b), and lateral (c) radiographs showing an oblique lateral malleolus fracture with an intact medial malleolus and widening of the medial clear space on the AP and mortise views
There are several radiographic criteria used to assess tibiotalar and syndesmotic stability that must be evaluated on initial injury radiographs. These parameters include fibular shortening, widening of the medial joint space, talar tilt, and malrotation of the fibula. Adequately assessing the congruency of the tibiotalar articular is paramount as 1 mm of tibiotalar displacement can lead to a 40% increase in joint contact pressures [1]. While bimalleolar fractures are inherently unstable, an isolated fibula fracture is only considered unstable if there is an accompanying medial-sided deltoid ligament injury.
Medial clear space widening of greater than or equal to 5 mm on radiographs taken in dorsiflexion with an external rotation stress is most predictive of deep deltoid ligament incompetence after a distal fibular fracture [2]. A stress external rotation radiograph done either manually or with gravity is obtained to determine if there is talar shift and often shows a high rate of positive stress on isolated fibular fractures with an intact mortise [3]. It is important to note that medial tenderness, ecchymosis, and swelling are not predictive of deltoid incompetence. Studies have shown that the use of gravity stress radiographs is equivalent to manual stress to determine medial-sided ligamentous injury [4]. However, the author’s preference is to perform a manual stress examination.
Treatment Considerations and Timing of Surgery
Given the closed nature of this injury, after closed reduction and splinting, the decision was made to send the patient home and surgery was scheduled for the following week once swelling had subsided. Based on the radiographs showing a lateral malleolus fracture without signs of significant comminution, the plan was to proceed with open reduction and internal fixation with a lag screw and neutralization plate following the principles of absolute stability. The posterior malleolus fragment did not involve a significant portion of the articular surface and did not require internal fixation.
Surgical Tact
Positioning
The patient is positioned supine on a radiolucent operating room table with a radiolucent distal extension if available. A tightly rolled small bump is placed under the ipsilateral posterosuperior iliac spine to combat external rotation of the leg and allow for easier access to the lateral malleolus. A radiolucent foam ramp is placed under the ipsilateral extremity to aid in intraoperative imaging by positioning the operative extremity at a higher level than the contralateral limb (to allow for unimpeded lateral view), and the C-arm is placed on the contralateral side of the table.
Approach
The author prefers to use a posterolateral approach to the fibula, placing the incision along the posterior border of the fibula. Dissection is carried down to the fascia with care to protect any branches of the superficial peroneal nerve, although the more posterior placement of the incision usually keeps the nerve in the anterior skin flap and away from the surgical field. The peroneal tendons and muscles are retracted posteriorly and protected throughout the approach and procedure. Minimal retraction is performed to relieve tension on the soft tissues.
Fracture Reduction and Fixation
Following exposure and debridement of periosteum from the fracture site including sharp excision of any periosteum interposed within the fracture site, pointed reduction forceps are used to obtain an anatomic reduction of the fibula. Given the oblique nature of the fracture, and limited comminution, fixation is amenable to a lag screw. A 3.5 mm lag screw is then placed perpendicular to the fracture site in a lag-by-technique fashion, in an anterosuperior to posteroinferior direction. After placement of the 3.5 mm lag screw, a one-third tubular plate is pre-contoured and provisionally held to the lateral side of the fibula with reduction forceps. Fibular length, rotation, as well as appropriate plate placement and length are verified fluoroscopically on AP and lateral views. The plate is fixed proximally with 3.5 mm bicortical screws and distally with 4.0 mm unicortical fully threaded cancellous screws. After fixation of the fibula, an external rotation stress test was performed and showed widening of the medial clear space, so placement of a syndesmotic screw was required. With the ankle held in dorsiflexion, a large pointed reduction clamp was placed across the syndesmosis with one tine on the fibula and the second tine on the tibia just proximal to the medial malleolus through a small stab incision to obtain and maintain an adequate reduction of the syndesmosis on the mortise view. A quadricortical 3.5 mm cortical screw was then placed through the fibula, across the syndesmosis and into the tibia. Intraoperative fluoroscopic views showed acceptable reduction and fixation of the lateral malleolus and syndesmosis (Fig. 1.2). The wound was closed and the leg was placed in a short leg splint postoperatively.
