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Eric Lee, M.D.
OAK Orthopedics

Ankle sprains are among the most common musculoskeletal injuries in athletes, both competitive and noncompetitive, accounting for anywhere between 10-30% of injuries. Indeed, the NCAA Injury Surveillance Survey demonstrated that it was the most common injury in college athletes, accounting for 15% of reported injuries. The medical cost of treating ankle sprains in athletes and the general population is extremely large, has been estimated to be greater than one billion dollars per year (US Consumer Products Safety Commission). Most people have some knowledge of the “classic” low, or inversion, ankle sprain and appropriate diagnostic, treatment, and rehabilitative measures. However, less is understood about the high, or syndesmotic, ankle sprain even though multiple studies have demonstrated that high ankle sprains cause more morbidity, dysfunction, and greater time to return to sport or activity. Epidemiological studies point out that between 11-17% of all ankle sprains are high/syndesmotic sprains. Due to the different mechanism of injury than low ankle sprains, they are found to be most common in high velocity collision sports, such as football, hockey, rugby, and lacrosse. Wrestling, due to the nature of the moves required to compete, also has a higher rate of high ankle sprains. There is not a clear consensus on the best approach to treating high ankle sprains, which also lends confusion to the overall management of these injuries. Because of this, it is important for the health care provider to distinguish between low and high ankle sprains with a careful history, examination, and appropriate imaging. In this article, we will take a look at the high ankle sprain - the anatomy of the syndesmosis, the mechanisms behind the most common causes of syndesmotic injuries, the diagnosis, and finally the treatment/management of high ankle sprains.

Anatomy

The syndesmosis plays an important role in maintaining the structural stability of the ankle joint, both between the tibia and talus (ankle bone), as well as between the tibia and fibula. It is made of up both bony and soft tissue structures. For the purpose of this article, we will focus on the soft tissue complex, which includes an interosseus membrane and four ligaments: the anterior inferior tibiofibular ligament (AITFL), posterior inferior tibiofibular ligament (PITFL), inferior transverse (tibiofibular) ligament (ITL), and the interosseus ligament (IOL). Fig. 1.

The deltoid ligament, on the medial side of the lower ankle, also plays a role in helping to stabilize the ankle syndesmosis in addition to its role as the primary ligamentous stabilizer of the entire ankle joint. It is important to include examination of this ligament whenever you suspect a syndesmotic ankle injury, as injury to the deltoid ligament usually indicates a more serious injury.

Figure 1

Mechanism of Injury

Because the syndesmosis is so stable, it takes a large force to cause a significant injury; therefore it is not surprising that many syndesmotic injuries are accompanied by a fracture. The most common mechanism of injury is forceful external rotation of the foot and ankle, most often when the foot is dorsiflexed and slightly pronated, as is seen when 1) an athlete rapidly pivots internally off of a foot planted in external rotation, 2) when contact with another player applies a valgus load to the leg while the foot is planted, or 3) when a direct blow to the lateral aspect of the heel forces the foot and ankle of a kneeling or fallen athlete into external rotation (toward the ground).1 Less commonly hyperdorsiflexion, as is seen, for example, when a gymnast underrotates on a landing or dismount, can cause syndesmotic injury by forcing the talus up into the syndemosis, driving the tibia and fibula apart. A number of other mechanisms of injury have been reported, including eversion ofthe ankle, inversion ofthe ankle with foot in plantarflexion (more commonly seen with low ankle sprains), and internal rotation of the foot and ankle.

History/Exam

As with all injuries, a careful history is important as it can yield many clues to a diagnosis of syndesmotic injury. The patient’s or another observer’s report of the mechanism of injury and description of the symptoms is important, as is whether any risk factors, such as rigid ski boots or skates, participation in high velocity collision sports, or history of flat foot, were involved. Most athletes are not able to ambulate immediately after the injury. If they can ambulate, it is usually with a protected gait pattern avoiding both full heel strike and full push off. The exam of the ankle may or may not demonstrate swelling and/or bruising. Isolated sprains to the distal tibiofibular ligaments (AITFL, PITFL) often have a small amount of swelling directly over the area, whereas more extensive injuries involving tears of the interosseus membrane and/or deltoid ligament will often have more substantial swelling of the ankle and distal leg. Most patients will have tenderness over the anterior syndesmosis, just above the ankle joint line, and it may extend proximally between the tibia and fibula as much as six inches. Studies have shown that there is a significant association between how far tenderness extends up the leg and how much time is lost from competitive sports. 2 There may be tenderness posteriorly over the PITFL as well. The deltoid ligament should be checked for tenderness, and depending on the mechanism of injury, tenderness may be noted over the lateral ligaments. Palpating the bony structures about the ankle as well the entire fibular shaft is important to help rule out fracture.

A number of tests have been used to assess the syndesmosis including the Cotton test, crossed-leg test, fibular translation test, stabilization test, squeeze test, and external rotation stress test. All of these tests aim to apply a stress to the syndesmosis. However, subsequent reviews and studies have demonstrated that none of the tests accurately predict the degree of instability of the syndesmosis. Only the external rotation test has good reliability for diagnosing an actual sprain and can be predictive of the time it takes to return to activity. In my practice, I use the external rotation test to gauge for pain, and have found it to be useful in following the athlete’s progress in rehabilitation. It is administered by having the patient sit on a table with the knee flexed to 90 degrees and grasping the lower leg to stabilize. The ankle is slightly dorsiflexed and externally rotated, without inverting the foot. (Fig. 2) It is positive if it causes pain in the syndesmotic area. However, in the acute setting, the external rotation test is often too painful to attempt.

Figure 2

Imaging

If there is a suspected syndesmotic injury, xrays of the ankle and of the entire tibia and fibula are obtained to rule out fractures and to look for any abnormalities in ankle joint spacing. Traditionally, if there has been a question of ankle joint instability, stress xrays were recommended. However, recent studies have demonstrated that they may not add much to normal, non-stress views, especially in the acute setting where pain and swelling may limit the ability to stress the ankle. MRI has been shown to be very sensitive and specific in identifying injuriesto the soft tissues ofthe syndesmosis. In my practice, I always obtain xrays to rule out a fracture. If there is a question of syndesmotic disruption which may lead to instability, I obtain an MRI, as treatment can be surgical in these cases. MRI is also very helpful in ruling out injuries to the deltoid and lateral ligaments.

Management/Treatment

One of the difficulties in treating syndesmotic ankle injuries is that there is not universal agreement on one treatment approach, and there are not scientifically validated studies which detail the optimal rehabilitative program. In addition, despite following a logical treatment plan, patients often are left with residual pain or feelings of instability following a return to activity after a high ankle sprain. Even with a logical rehabilitative program, experienced therapist, and motivated patient/athlete, the time to return can still vary from between 10 to 60 days.

Frank disruption of the ankle joint, displaced fracture, or Maissoneuve fracture (fracture of the proximal fibula due to rotational stress at the ankle joint at time of injury) are indications for operative repair. Recent research has suggested that operative screw fixation of the distal syndesmosis in complete tears of the interosseus ligament, even without disruption of the ankle joint, can allow athletes to return to their sport much quicker than nonoperative treatment (as early as six weeks vs. twelve to fourteen weeks). Clinically, I have found this to be the case and will usually obtain a surgical consult in this instance.

When the ankle syndesmosisissprained, butstable, as confirmed by exam and imaging studies, I follow a three phase progression of rehabilitation. The goal of the first phase is to reduce swelling and pain and protect the ankle from further injury, usually by limiting external rotation. If the patient is having pain or trouble with weightbearing, or the injury is suspected to be on the more severe end of the spectrum, he is placed in a CAM boot to allow the ankle to rest. Crutches are used in addition to the boot if weightbearing is painful. Ice, compressive wrap, and elevation are used to control swelling. If the patient does not have a limp or painful gait, or the injury appears to be quite mild, he may be placed in a lace up tri-lock ankle brace for support and allowed to weightbear. The ability of the patient to protect the ankle within the gait cycle also plays a role in the extent of initial immobilization. As swelling and pain subside, I will have the patient start gentle, pain free range of motion exercises about the ankle.

The goal of the second phase of treatment is to restore normal range of motion to the ankle and build strength for simple daily tasks such as walking or doing stairs. The goal is to normalize gait, and allow the ankle to begin to take some light stress. Strengthening progresses from low-intensity, high repetition sets to higher intensity, low repetition sets. Closed chain functional tasks and light balancing exercises are helpful as well as the patient progresses. If there is access to a pool, aquatic therapy is a useful adjunct in this phase. Some authors have suggested a time based progression through phases in return. However, because of the variability of healing time with these injuries, I prefer a functional capacity progression. The patient can progress out of phase two when functional strength for normal tasks is achieved, such as walking normally or hopping on one foot without pain or significant dysfunction.

The goal of the third phase is return to sport and increased activity. As the patient progresses to full functional strength in his every day activities, higher level neuromuscular and sport specific activities are added in. These will focus on neuromuscular control, higher level functional strength, and sport specific stresses. As stated earlier, the time to return is quite variable, which is why progression through the phases is determined by functional capacity of the ankle rather than by strict time measures. Throughout the process, good communication between the athlete, trainers, physical therapist, and physician is essential.

High ankle sprains can be a discouraging injury for an athlete and a frustrating injury to manage for physicians, trainers, and therapists. Managing the athlete’s expectations regarding return to play is important, as is regular communication between all involved in the patient’s care. With a prompt diagnosis, early initiation of treatment, and a logical rehabilitation program which progresses as the athlete proves he is ready, we can provide the athlete the best chance at resuming his activity as quickly as possible.

1. Williams et all. Rehabilitation of Syndesmotic (High) Ankle Sprains. Sports Health: A Multidisciplinary Approach. December 2010. Vol. 2 No. 6. Pg. 460-70.

2. Ibid.