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Syndesmotic injury: Treatment in a rotationally unstable ankle fracture
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When a syndesmotic injury occurs in conjunction with a rotationally unstable ankle fracture, treatment of the ligamentous injury follows restoration of the bony integrity of the ankle mortise. Restoration of all distal tibiofibular relationships is paramount.
Maintenance of proper fibular length and rotation relative to the distal tibia is difficult in certain injury patterns. While the need for anatomic restoration of these parameters is universally agreed upon, controversy exists with regard to certain technical aspects of surgical treatment of syndesmotic injuries that occur in conjunction with a rotationally unstable ankle fracture. Different implants, fixation constructs and rehabilitation protocols for these injuries exist.
This Orthopedics Today Round Table centers upon the indications for and techniques of syndesmotic fixation in conjunction with an associated unstable ankle fracture. Our panel of experts, all well versed in the management of these injuries and members of the Orthopaedic Trauma Association and have graciously given us their expert opinions about syndesmotic fixation.
Kenneth A. Egol, MD
Moderator
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Kenneth A. Egol, MD
Sean E. Nork, MD
David W. Sanders, MD
Paul Tornetta III, MDKenneth A. Egol, MD: In the situation in which you have a fibula fracture in conjunction with a syndesmotic injury, when do you use fibular plate fixation versus screws alone?
Sean E. Nork, MD: I try to fix the fibula with a plate in almost every instance. Invariably the fibula is shortened and rotated to some degree, even in fractures perceived to be minimally displaced. I think an accurate restoration of the fractured fibula guarantees that the length and the rotation of the fibula are restored. The combination of an open reduction of the fibula with an open reduction of the distal tibiofibular syndesmosis ensures that the relationship between the tibia and the fibula is accurate at the time of syndesmotic fixation. I realize that fractures of the fibula in the proximal and middle third are surgically inconvenient, but the cost to the patient of a syndesmotic malreduction is high. Relying on inaccurate qualitative intraoperative radiographic measures is not reliable.
David W. Sanders, MD: I prefer fibular plate fixation when the fibula is shortened. While syndesmotic screw fixation is excellent at maintaining rotational alignment of the fibula within the incisura, its ability to prevent axial shortening is limited. I do not rely on a specific rule with regards to height of the fibular fracture, but simply prefer to use a plate if there is a fracture associated with axial shortening of the fibula.
Paul Tornetta III, MD: This is a wonderful question. We all tend to use some arbitrary cutoff as to when a plate is needed. For me, screw only fixation is a common procedure, but the key to whether this is possible lies in the comfort of the surgeon with the fibular alignment. Additionally, whether to open the syndesmosis or use a percutaneous technique requires some thought. In my practice, I try to focus on the alignment of the mortise, as this is the single variable that is most predictive of outcome. If I can get perfect alignment of the mortise as compared with the other side without opening the fibular fracture, then I use syndesmotic fixation only.
This requires that the mortise is accurately aligned, based on tibia-fibula distance, talocrural angle, and the position of the distal fibula on the lateral radiograph as compared with the normal side. Additionally, the fibula should appear to be perfectly out to length on fluoroscopic assessment of the fibular fracture, if one exists. Given this “perfect” scenario, then fixation of the syndesmosis alone will allow union in the proper position.
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Images: Tornetta P |
One potential trap is the assessment of fibular length, as without fibular fixation, it is easy to be slightly short. If there is any question of length, I recommend opening the fibular fracture if it is in the distal half of the bone, or the mortise if the fibular fracture is very high, in order to accomplish an accurate reduction.
Egol: What is your preferred construct for syndesmotic fixation and why with regard to number of screws, size of screws and number of cortices?
Nork: I typically use 3.5-mm screws placed through 4 cortices. Because I rarely remove the implants, I want to be able to retrieve the screw if late hardware failure occurs. Hence, the need to leave the implant slightly proud on the medial side. A 4.5-mm screw is so large that it obligates screw removal. The number of screws depends on the associated injuries and the associated fixations. In cases where there is an associated fibular fracture relatively close to the ankle joint (within 4 or 5 cm) that I’ve accurately fixed with a plate, I’ll typically place a single 3.5-mm screw through 4 cortices. If a more proximal fibula fracture exists, I will still fix the fibula fracture (even if quite proximal) but will more often place 2 syndesmotic screws given the perceived larger disruption between the tibia and the fibula.
In patients with significant osteopenia, I typically use at least 2 screws, and sometimes even more in revision cases. One additional caveat, in addition to fixing the fibular fracture whenever possible, I also do an open reduction of the syndesmosis to ensure the reduction is accurate. I think a good reduction decreases the stress on the implants.
Sanders: My preferred construct varies depending on the fracture pattern. For the typical supination external rotation injury associated with a slight increase in the medial clear space noted on an external rotation stress test, I generally use a single tricortical 3.5-mm screw. For the high fibular fracture, as in a pronation external rotational injury associated with obvious syndesmotic diastasis, I prefer 2 screws. Here again, I use 3.5-mm screws with tricortical fixation. My indication for obtaining 4 cortices of fixation is when trying to achieve a lateral buttress function. For example, to reinforce a fibular construct in the face of excessive comminution, or in a diabetic with a Charcot tibiofibular diastasis.
Tornetta: Typically I use at least 2 3.5-mm-position screws. One screw may suffice in distal fractures with adequate plate support and only minimal post plating instability. I will use only three cortices in young patients, and expect that these may loosen over time if not removed. In older patients, diabetics, in revision work, and fusions, I use multiple screws, usually through a stronger plate and engage all four cortices. The tradeoff here is that smaller screws are more likely to break, and if they are all the way across to the far cortex, the distal end can be removed from the far side if it breaks. If only three cortices are used, then in the event that the screw breaks, the distal part is left in place. Larger screw heads are annoying to the surrounding soft tissues and demonstrate little advantage clinically.
Egol: What is your postoperative management in patients whom you have stabilized an unstable syndesmotic injury? Should the syndesmotic screws be removed prior to weightbearing or at any point?
Nork: Postoperatively I keep patients nonweight-bearing for 12 weeks. Yes, 12 weeks. I allow early (immediate) ankle motion, but I limit their activities to ensure scarring of the syndesmosis in an accurate position. The most unhappy patients imaginable are those with a poorly treated or inaccurate syndesmotic reduction. I think the screws can be removed but I don’t remove them unless they are symptomatic. Even broken screws (which occur frequently) are not usually a source of pain.
Sanders: There is not much data on this. I have adopted a protocol which tried to balance early mobilization and adequate protection of the repair.
I restrict weight-bearing in syndesmotic injuries for 6 weeks and provide a removable brace until about 3 months. I try to start ankle mobilization after about 2 weeks, provided the incisions are healing. I have traditionally left the syndesmotic screws in position unless evidence of screw prominence or substantial restriction of ankle motion was noted. However, we recently reviewed our results and found that the patients in whom the screws were removed, broken or loose are doing better than patients with screws that had remained intact. As a result, I have now increased the number of screws I am removing such that if a screw is tight and the ankle is at all symptomatic after about 6 months, I generally offer screw removal.
Tornetta: I have no idea! There is no well-done evaluation of this question. We used to remove all of them at 3 months, and stress the ankle under fluoroscopy to confirm that there was no residual instability But, we have gotten away from this. While that method was successful, no late instability was noted so the need for the exam is limited. Given this, and the paucity of literature to help with the decision, we now offer the patient the option of removal. We tell them that we do not know if it will potentially improve their long term function, but it is a minimal morbidity operation to remove them, and that these screws will loosen or break over time in all cases.
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I would state strongly, however, that if screws are removed, it cannot be before 3 months, otherwise the risk of redisplacement is higher. Protected weight-bearing is an acceptable option, although we use this on a very limited basis.
Egol: Do you feel there is a role for suture fixation of the syndesmosis?
Nork: I’ve never done this technique.
Sanders: I am not sure what role suture fixation of the syndesmosis will to play. I agree with the general principle that syndesmotic fixation which permits slight motion may be beneficial. But, whether a suture is strong enough to prevent post operative tibiofibular diastases remains unknown. I think this is a topic which requires a great deal of further study, and I’m not sure that the best implant has yet been developed.
Tornetta: We have not used this technique ourselves, but have had the opportunity to revise 4 cases treated this way. Several methods have been described including local suture techniques and trans-syndesmotic methods. Currently, there is no evidence that this is superior to standard screw fixation. I await evidence before embarking on a new method of surgical management, particularly in cases where a successful method is available. While there may be some potential for “dynamic” methods of fixation to allow earlier “anatomic” motion of the syndesmosis, given my experience with revisions and complex cases, the scar tissue in the area that forms in response to the injury is significant. I would need to see a randomized trial with documented improvements compared with the current standard in order to try this. As with all other “new” techniques, I believe that they should be introduced only after there is sufficient evidence of safety. General adoption should be deferred until a randomized trial shows some benefit.
For more information
- Kenneth A. Egol MD, can be reached at NYU-Hospital for Joint Diseases, 301 E. 17th St., New York, NY 10003; 212-598-3889; e-mail: ljegol@att.net. He has no direct financial interest in any products or companies mentioned in this article.
- Sean E. Nork, MD, can be reached at Harborview Medical Center, Department of Orthopaedics, 325 9th Ave., Seattle, WA 98104; 206-744-3466; e-mail: mkanna@u.washington.edu. He has no direct financial interest in any companies or products mentioned in the article.
- David W. Sanders, MD, can be reached at Victoria Hospital, E4-123 Westminster Tower, London, ON N6A4G5, Canada; e-mail: david.sanders@lhsc.on.ca. He has no direct financial interest in any products or companies mentioned in the article.
- Paul Tornetta III, MD, can be reached at 850 Harrison Ave., 3rd Floor, Boston, MA 02118; 617-414-5212; Email: ptornetta@pol.net. He is a consultant for, and receives royalties from Smith & Nephew.