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AAOS Now

Published 11/1/2014
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Terry Stanton

Syndesmotic Injury: Managing Fractures and Failed Repairs

Proper reduction and anatomic restoration are keys to long-term success

Addressing management of syndesmotic injuries at a symposium at the annual meeting of the American Orthopaedic Foot & Ankle Society, Robert B. Anderson, MD, sounded a theme to work by: Respect the joint.

“This is a functional, synovial-lined joint,” he elaborated. “It has cartilage on both sides. It pistons. It rotates. It widens.”

The joint “gets its stability from the ligaments that surround it,” Dr. Anderson, of OrthoCarolina in Charlotte, N.C., explained. “It basically contains the fibula to the tibia to keep the talus in proper position.”

A common mechanism of injury to the syndesmotic region is external rotation of the foot around the tibia. Common injuries include the purely ligamentous “high ankle sprain” and fractures, including the Weber B pronation exorotation fracture across the syndesmosis, Weber C supination exorotation fracture above the joint, proximal fibula (Maisonneuve) fracture, and posterior malleolar fracture.

The posterior malleolar fracture has drawn increased attention, said Dr. Anderson. “It is important to understand that the posterior malleolus is where the posterior-inferior tibiofibular (PITF) ligament attaches, and this ligament imparts most of the stability to the syndesmotic region and thus to the ankle joint.”

The deltoid ligament is also significant in the management of syndesmotic injuries. Dr. Anderson admitted to having a “low threshold” for using an open approach for syndesmotic injuries involving the deltoid. “It is more common to approach the deltoid ligament through an open approach on the medial side, to visualize it, and to possibly repair it when a concomitant syndesmotic injury exists,” he said. “Opening medially should be considered if the ankle joint cannot be reduced, due to the possibility of an embedded superficial deltoid or large avulsion piece.”

Timely, effective repair important
Syndesmotic reduction is important, said Dr. Anderson, for the following reasons:

  • 1 mm of lateral displacement of the talus results in a 42 percent reduction in tibiotalar contact, with a resulting increased risk of degeneration.
  • An increase in the width of the syndesmosis of more than 1.5 mm is unacceptable and associated with a poor result.
  • Anatomic reduction of the syndesmosis has been found to be the only significant positive predictor of functional outcome.

Missed injuries, with longstanding subtle instability or failed reduction, risks development of bipolar cartilage lesions and secondary degenerative joint disease, warned Dr. Anderson. He listed the following common causes of failed syndesmotic repair:

  • poor reduction of the fracture
  • poor reduction of the syndesmosis
  • inadequate fixation
  • premature removal of fixation
  • too-aggressive rehabilitation and/or patient noncompliance
  • degeneration/synostosis

Effective syndesmotic reduction “begins with proper fracture management,” Dr. Anderson said. This requires restoring fibular length and rotation as well as reducing the posterior malleolus to achieve the proper relationship to the PITF ligament.

In Maisonneuve fracture, fixation of the proximal fibula requires a difficult exposure with a risk of nerve injury.” I will not typically fix the fracture with open techniques,” he said. He will perform an open reduction of the syndesmosis distally to ensure proper length and rotation.

“Avoid malreduction and make sure you get the syndesmotic joint back into position regardless of whether you are fixing the fibular fracture,” he advised.

Using a clamp requires cautious handling. “The clamp itself can create a malreduction. If it is placed obliquely instead of transversely, it can pull the fibula out of its natural groove,” warned Dr. Anderson.

Although malreduction may occur in about one-third of cases, one study found that most patients (89 percent) demonstrated adequate syndesmotic reduction on CT imaging after syndesmotic screw removal. Dr. Anderson suggested removing the syndesmotic fixation and observation in the event of malreduction.

Addressing the issue of how best to assess the distal tibial-fibula relationship, Dr. Anderson said that classic radiographic measures have been shown to be inaccurate. Intraoperative options include tests that manipulate the fibula to look for lateral translation or posterior displacement of the fibula out of the natural sulcus of the tibia. He advised looking for instability on both AP and lateral views during intraoperative assessment.

Intraoperative O-arm and CT imaging have been used for assessment, but Dr. Anderson noted these modalities are not readily available, are expensive, and involve considerable radiation exposure. He has found that intraoperative arthroscopy may be the best assessment technique to confirm alignment.

Fixation matters
If screws are used, Dr. Anderson recommended large 4 mm screws—4.5 mm in larger individuals—because they provide more rigidity and are stronger in axial loading. Quadricortical screws are preferable to those with three cortices of fixation.

“Regardless of fixation, you must protect these ligamentous injuries postoperatively,” he cautioned. Early screw removal can lead to failure of syndesmotic repair. A 10 percent loss of reduction was seen with screw removal at a median of 9 weeks. “These ligament injuries take a long time to heal,” he said, and proposed not removing the screw at all. “Studies have shown that if screws are retained and break, people still do fine,” he said. “The trend is toward keeping them in place.”

An increasingly popular alternative to screws is suture button fixation, which carries no concern about breakage or removal. Although no long-term studies have evaluated the use of suture buttons, short-term studies have been favorable. Most situations require two suture-button constructs.

Whichever fixation method is used, place the fixation at least 1.5 cm above the joint line to avoid the “true” syndesmotic joint, said Dr. Anderson.

“Avoid placing the screw in the distal area, because if it should break, it is very hard to retrieve, and iatrogenic damage to that functional joint may occur,” he instructed.

The position of the foot in fixation is not consequential, and it can be left in the resting position.

Complications and concerns with syndesmotic repair include pain relating to inflammation and degeneration. Bone scan or CT scan may aid in diagnosis. Incomplete synostosis may be signaled by mechanical symptoms with activity; treatment may include cortisone injection and immobilization.

For cases of failed fixation and recurrent diastasis, Dr. Anderson advised obtaining a CT scan to evaluate the fracture, using both axial and comparison images. An MRI to assess the joint condition may also be useful.

If the fibula is short, he advised fibular lengthening, with repeat syndesmotic reduction and fixation. For early recurrent diastasis, reconstructive options may be appropriate. These include allograft options, autogenous tendon grafts (including the plantaris and split peroneus longus), and reconstruction with multiple extensor tendons.

Disclosure information: Dr. Anderson—Arthrex, DJ Orthopaedics, Wright Medical Technology, Amniox, Foot & Ankle International, Elsevier.

Terry Stanton is a senior science writer for AAOS Now. He can be reached at tstanton@aaos.org

Bottom Line

  • The syndesmosis should be viewed as a functional joint.
  • Common injuries include the “high ankle sprain” and fractures above and around the joint.
  • Syndesmotic repair begins with good fracture management, including restoration of fibular length and rotation.
  • Placement of screws in the “true” syndesmotic joint should be avoided; screws should be placed at least 1.5 cm above the joint line.
  • Screws should not be removed too early; broken screws may best be left in place.