Fixation Of The Medial Malleolus Fracture: What You Should Know
Those with experience in the surgical treatment of ankle fractures often consider the medial malleolus fracture a relatively straightforward fracture to repair. Most commonly, surgeons use two screws to fixate the fracture and it is a short procedure in terms of operative time.
The surgery is often so predictable that the surgeon may go into “auto pilot” mode (more appropriately termed “auto surgeon” mode). However, there is some fracture variability that occurs and it is important for the surgeon to slow down and choose the best fixation for the fracture pattern.
The pattern of fracture of the medial malleolus is dictated by the mechanism of action, transmitted force and patient bone stock. There are five patterns of fracture. They are as follows:
Some fracture patterns are more amenable to certain types of fixation.
Avulsion fractures. Surgeons do not typically repair the avulsion “fleck” fracture of the medial malleolus because the fracture fragments are too small to accept fixation. As long as the talus is aligned within the mortise and there is no increased medial clear space, it is best to treat these injuries conservatively. However, medial ankle ligamentous avulsions may be suspicious for lateral ankle and/or syndesmotic injury, which one should evaluate thoroughly and treat appropriately (see figure 2).
Transverse fractures. Transverse fractures occur at or below the joint line. Depending on the size of the fracture, one may use screw(s) and/or K-wire(s). The tension band technique is ideal for transverse fractures of the medial malleolus (see figure 3). These fracture fragments are often small and there is limited bone real estate to place screws but this depends on the particular fracture fragment.
Ideally, surgeons should use two screws to prevent rotation (see figure 4). However, small fracture fragments may only accommodate one screw with the medial malleolus. Adding a K-wire may be advantageous in these situations. As the fracture fragment tends to be relatively small, the surgeon must ensure accurate placement of the fixation without multiple attempts. Multiple fixation attempts may result in iatrogenic fracture, which may render the fragments unfixable. Cannulated screws are beneficial here. One should strongly consider the tension band technique as a first-line approach to significantly lessen the chance of iatrogenically pulverizing the fracture fragment.
Oblique fractures. The oblique fracture is probably the most commonly encountered fracture of the medial malleolus. In these cases, there is often sufficient bone of the fractured malleolus to accommodate two screws. However, the surgeon should space the screws out from anterior to posterior on the medial malleolus. The partially threaded 4.0 mm screw seems to be the screw of choice and a cannulated system simplifies the process.
Remember that the distal tibia is constructed of spongy bone and a cancellous pitch screw is ideal. One should ensure the screws are divergent in one plane in order to maximize the fixation (see figure 5). If the screws are embedded within the bone, they most often measure 5.0 mm in length. The surgeon may fixate the oblique fracture percutaneously and perform this fixation with intraoperative fluoroscopy.
Long oblique/vertical fractures. The long oblique/near vertical medial malleolar fractures may be a little tricky to fixate. In these cases, the forces acting on this fracture tend to displace the medial malleolus superiorly. This may occur intraoperatively and/or postoperatively. The malleolar screw is ideal for these patients because the screw has a trocar tip that penetrates the lateral tibial cortex. This screw tip provides some additional stability that limits the upward migration of the fractured malleolus (see figure 6). Another option is to incorporate a medial anti-glide plate (see figure 7).
Comminuted fractures. Comminuted fractures of the medial malleolus may be especially challenging. Tension band technique is particularly useful for these patients. The two largest fracture fragments should receive the K-wires for incorporation into the tension band construct (see figure 8). In severe cases with multiple fragments, K-wire fixation may be the only fixation option possible. Threaded K-wires may provide some stabilization of the distal fragment as well.
While there are several fixation options to repair a fractured medial malleolus, the decision to use a specific type of fixation and fixation construct is based on the fracture pattern, bone stock and, most importantly, the surgeon’s experience.