High Ankle Sprains
Minimizing the Frustration of a Prolonged Recovery
Andrew H. Smith, MD; Bernard R. Bach, Jr, MD
THE PHYSICIAN AND SPORTSMEDICINE - VOL 32 - NO. 12 - DECEMBER 2004
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In Brief: High ankle sprains, or syndesmotic injuries, are a distinct entity from the more common inversion ankle sprain. Dorsiflexion of the ankle, external rotation of the leg, or a combination of both can disrupt the syndesmotic ligament complex, including the anterior and posterior tibiofibular ligaments. Diagnostic maneuvers, such as the squeeze test and the external rotation test, plus radiographic findings help make the diagnosis. Less severe sprains can be treated nonoperatively with protected weight bearing, but grade 3 sprains require surgical anatomic reduction of the syndesmotic joint. If misdiagnosed or managed incorrectly, syndesmotic injuries can lead to unfavorable late sequelae. Clinicians should set realistic expectations for a long recovery period and slow return to sports.
Ankle sprains, the most common of all sports injuries, have a spectrum of injury severity from minor ligamentous injury to complete ligament rupture with joint dislocation. The magnitude of an ankle injury depends not only on the energy of the force, but on which of the many ligaments that stabilize the ankle are injured. The location of injury can involve the medial, lateral, or proximal ligament complexes. By definition, an ankle sprain is a partial or complete rupture of one or more of the ligaments of the ankle joint.
More than 25,000 ankle sprains occur each day in the United States, but only 1% to 15% involve syndesmotic injuries.1 While typical inversion-type ankle sprains are more common, the sheer number of ankle injuries makes it statistically likely that most sports medicine physicians will see patients who have high ankle sprains.
Grading sprains from least severe to most severe is useful for more than classifying the severity of the injury; it also directs treatment and prognosis. Grade 1 injuries represent intrasubstance fiber disruption that is only apparent on microscopic evaluation of the ligament fibers. Grade 2 injuries are characterized by intrasubstance fiber disruption that is visible on gross examination of the ligament. Complete ligament disruption or avulsion is categorized as grade 3.2 Clinical pearls aimed at clarifying the diagnosis, treatment, and return-to-play considerations concerning high ankle sprains will aid the sports medicine physician in evaluating these injuries.
High Ankle Anatomy
The major ligament complexes of the ankle are the medial, lateral, and syndesmotic complexes. The medial ankle ligaments are composed of the deep and superficial deltoid ligaments. The lateral ligament complex is made up the anterior talofibular ligament (ATFL), calcaneofibular ligament (CFL), and posterior talofibular ligament (figure 1). Inversion ankle sprains typically involve the lateral ankle ligaments, in particular the ATFL.
High ankle sprains involve the interosseous ligament and/or the anterior and posterior tibiofibular ligaments. The syndesmotic ligament complex comprises the interosseous ligament and the tibiofibular ligaments; together these form the entire connection between the distal tibia and fibula. The interosseous membrane fibers course obliquely from their tibial attachment to their fibular attachment and join the two bones along their entire length. The interosseous membrane thickens distally to form the interosseous ligament of the syndesmosis. Immediately above the ankle joint, the anterior tibiofibular ligament connects the tibia and fibula anteriorly. At the same level, the posterior tibiofibular ligament attaches the tibia to the fibula posteriorly. The posterior transverse tibiofibular ligament supplements the posterior connection of the tibia to the fibula at the inferior aspect of the posterior tibiofibular ligament (figure 2).
Distinct Injury Mechanism
A classic inversion-type ankle sprain involves the ATFL or the CFL. In high ankle sprains, the interosseous ligament is variably injured, along with the anterior and/or posterior tibiofibular ligaments. A high ankle sprain can occur alone, or in conjunction with additional adjacent ligament injuries, so adjacent joints must also be assessed for injury.
Even though the trauma occurs at the ankle, the proximal energy dissipation and injury to the interosseous ligament vary. Associated fractures can be found anywhere from 2 cm above the ankle joint proximally to the fibular head (Maisonneuve fracture).
Whereas a typical ankle sprain is caused by inversion, the mechanism of injury for a syndesmotic injury is dorsiflexion of the ankle or external rotation of the leg or a combination of dorsiflexion and external rotation. A typical pattern involves twisting on a planted foot. Athletes at risk include football linemen who rotate on a planted leg, downhill skiers who dorsiflex in ski boots, and hockey players who push off with the ankle everted and externally rotated.
Examination and Targeted Tests
Classically, a patient who has a high ankle sprain reports point tenderness over the anterolateral tibiofibular joint where the fibers of the anterior tibiofibular ligament are often disrupted. The patient may have pain with passive dorsiflexion of the ankle.
The external rotation stress test and the squeeze test are used to assess the injury (figure 3). Pain closer to the knee during the squeeze test indicates a more severe injury that will take longer to heal. Additional provocative maneuvers can identify the level of injury. The patient may be unable to squat with his or her feet flat, because it is too painful (dorsiflexion-external rotation mechanism). The athlete's symptoms may be exacerbated by sport-specific activity. For example, a football lineman may be unable to push off out of his stance.
Standard anteroposterior (AP), lateral, and mortise radiographs of the ankle may be within normal limits. If a high ankle sprain is suspected, AP and lateral views of the entire tibia and fibula should be obtained to rule out an associated proximal fibular fracture.
On radiographs, the medial clear space should be of equal width to the weight-bearing tibial talar articular surface and not more than 4 mm on the mortise view. On the AP view, the clear space between the fibula and the peroneal incisura of the tibia (fibular notch of the tibia) should be less than 5.2 mm in women and less than 6.5 mm in men. The tibiofibular overlap should be greater than 2.1 mm in women and more than 5.7 mm in men. Findings outside these parameters indicate syndesmotic injury (figure 4). Syndesmotic injuries may also result in lateral translation of the talus (figure 5).3-7
Special views. Dynamic radiographs are often needed to exhibit the injury. A single-leg, weight-bearing mortise radiograph may more accurately demonstrate instability. Stress radiographs are another way of testing for dynamic instability that is not apparent on plain x-rays. A stress x-ray can be performed by manually applying an external rotational force to the foot while holding the leg stable. A negative stress radiograph under anesthesia may exclude ankle instability.
MRI findings. Every patient with a high ankle sprain does not require magnetic resonance imaging (MRI), but it will define the zone of soft-tissue injury and may detect a talar bone bruise. Bone bruising is associated with longer recovery. Additionally, MRI may help identify injuries to anterior and/or posterior tibiofibular ligaments. If both ligaments are involved, recovery is longer.
In addition to recurrent instability, unrecognized syndesmotic injuries with concomitant lateral talar shift place the tibial talar joint at increased risk for the development of posttraumatic arthritis. Other late sequelae include ossification of the interosseous ligament and potential tibiofibular synostosis.8-10
The treatment for a grade 1 high ankle sprain does not vary widely from a typical inversion ankle sprain. Initial treatment consists of rest, ice, compression, elevation, and restriction from athletics. Immobilization with a long, semirigid pneumatic stirrup brace that extends to just below the knee is often beneficial. Protected weight bearing may be necessary for up to 3 weeks. The athlete may be able to return to play more rapidly with protective taping and a heel lift.
Grade 2 syndesmotic injuries are also managed nonoperatively. Weight bearing is restricted longer than with a grade 1 injury. Three to 6 weeks of non-weight bearing is recommended.
The foundation of successful treatment of grade 3 sprains is surgical anatomic reduction of the syndesmotic joint. The reduction is held provisionally with a large two-point bone tenaculum prior to fixation. One or two screws are used to stabilize the tibial-fibula joint. A large fragment screw (4.5 mm diameter) is preferred to a 3.5-mm screw to reduce the likelihood of hardware breakage. At least one screw should obtain four cortices of involvement. Screws should be inserted slightly proud (2 mm) on the opposite tibial cortex, which facilitates removal if screw breakage does occur. Drill placement and subsequent screw placement should be performed with the ankle dorsiflexed to avoid overtightening the ankle mortise, because the talus is wider anteriorly and narrower posteriorly, with a trapezoidal cross section. Overtightening may preclude recovery of ankle dorsiflexion. Intraoperative stress radiography after the fixation is in place is used to confirm a stable reduction. Syndesmotic screws can be left in place permanently, but they are generally removed 3 to 6 months after surgery (figure 6).
Recovery Phase and Return to Play
Patients should expect that recovery from a high ankle sprain will take much longer than from an inversion ankle sprain. Recovery for a grade 1 sprain can last 3 to 6 weeks, and recovery for grade 2 and grade 3 sprains is even longer. It is critical that the athlete, coaches, and parents be given realistic expectations.
The location of tenderness correlates with length of recovery. The more proximal the localized fibular tenderness, the longer the recovery. As the patient recovers, repetitive examinations will demonstrate distal progression of local fibular tenderness.
The ability to jump and land on the involved foot should be monitored for return-to-play decisions. The athlete should also be monitored in a sport-specific simulation prior to returning to competition. A football player should be able to explode out of his stance, and a hockey player should be able to skate with no pain on lateral push-off.
Syndesmotic injuries, or high ankle sprains, are less common than inversion sprains, but they occur with enough frequency that their unique characteristics should be appreciated. To the uninitiated, syndesmotic injuries can be difficult to diagnose and treat. Diagnostic maneuvers, treatment guidelines, and return-to-play criteria for high ankle sprains help clarify their management. With enhanced understanding of high ankle sprains, players, parents, coaches, athletic trainers, family practitioners, and orthopedic surgeons can set realistic expectations for a full recovery.
Dr Smith is a fellow and Dr Bach is a professor and director in the division of sports medicine in the department of orthopedic surgery at Rush University Medical Center in Chicago. Address correspondence to Bernard R. Bach, Jr, MD, Rush University Medical Center, 1725 W Harrison St, Suite 1063, Chicago, IL 60612; e-mail to [email protected].
Disclosure information: Drs Smith and Bach disclose no significant relationship with any manufacturer of any commercial product mentioned in this article. No drug is mentioned in this article for an unlabeled use.