Mastering The Treatment Of High Ankle Sprains

Author(s): 
George T. Liu, DPM, FACFAS, and Michael D. VanPelt, DPM, FACFAS

High ankle sprains can be particularly challenging to treat given the desire to return the athlete to the sport as quickly as possible. Accordingly, these authors review the biomechanics of ankle syndesmosis, the pros and cons of imaging modalities, and keys to treatment and rehabilitation that will help ensure a safe and reasonably expeditious return to play for athletes.

While lateral ankle sprains are viewed as the most common athletic injury occurring in sports, high ankle sprains have been responsible for more lost time from game play and training activities.1 Since high ankle sprains are commonly mistaken for lateral ankle sprains, they are less commonly reported.

   Misdiagnosing a high ankle sprain can result in lingering pain and recovery as the treatment course for syndesmosis injuries is often protracted, requiring longer periods of offloading and rehabilitation in comparison to lateral ankle sprains.1 For recreational and elite athletes, high ankle sprain is the most common contributor to persistent ankle pain and disability.2

   A high ankle sprain refers to injury of the distal tibiofibular syndesmosis. This complex is comprised of the anterior inferior tibiofibular ligament, interosseous ligament, posterior inferior tibiofibular ligament and deep transverse tibiofibular ligament. The syndesmotic complex serves as a ligamentous restraint to the fibula, resisting normal physiologic external rotation and lateral translation of the talus during the stance phase of gait. This restraint also allows an increased intermalleolar distance (an average of 1.25 mm) to accommodate the wider shape of the anterior talar dome with dorsiflexion of the ankle.3

Key Insights On The Biomechanics Of The Syndesmosis Injury

The ankle syndesmosis injury comprises a strong complex of ligaments that require significant force to cause disruption. Syndesmosis injuries often involve forceful external rotation of the foot relative to the leg and commonly occur in collision sports, such as football, hockey and court sports such as basketball.1,4

   Lauge-Hansen previously described this mechanism as a pronation-external rotation injury in which the talus and foot externally rotate relative to the tibia while the foot is in a fixed, pronated position.5

   While the foot is pronated, the deltoid ligament complex becomes taut. As the foot externally rotates on the ankle, the deltoid ligament is the first ligament to rupture. With the talus now unrestrained, the force of talar external rotation translates to the fibula and the anterior inferior tibiofibular ligament is the first syndesmotic ligament structure to fail. The anterior inferior tibiofibular ligament contributes 35 percent of the stiffness of the syndesmotic complex.6

   Once this primary restraint ceases, the talus continues to migrate laterally and in external rotation against the fibula, causing tearing of the interosseous membrane. With rupture of both the anterior inferior tibiofibular ligament and interosseous ligament, the syndesmosis loses approximately 58 percent of its stability.6

   The ankle is comprised of bony and ligamentous restraints, which are designed to stabilize the talus within the mortise of the ankle. Ankle injuries, such as isolated lateral malleolar ankle fractures and syndesmosis injuries, are considered stable provided the deltoid ligament is intact.7-9 Though the deltoid ligament complex is made up of superficial and deep fibers, it is the deep fibers that restrain the talus, maintaining stability and the physiologic motion within the ankle joint mortise.

   A cadaveric study demonstrated that isolated lateral malleolar fractures and isolated syndesmosis injuries do not alter the kinematics or stability of the ankle in the absence of a deep deltoid ligament rupture.10

   Patients with high ankle sprains often report the foot being anchored to the ground while being tackled by an opponent from the lateral side. This forceful twisting injury may be accompanied by an audible pop and the patient’s inability to bear weight after the injury. Additionally, traditional functional immobilization with a controlled ankle motion (CAM) walker or lateral stirrup bracing typically does not provide adequate relief for weightbearing in severe syndesmosis ankle injuries as it would with lateral ankle sprains.

What To Look For In The Diagnostic Workup

On the clinical examination, patients often present with supramalleolar swelling and ecchymosis. Other than direct palpation of the syndesmosis, several clinical maneuvers can help diagnose syndesmosis injuries.

   The most commonly utilized test is the fibular squeeze test, which can produce pain at the ankle syndesmosis by squeezing the proximal fibula to the tibia at approximately the middle of the leg in an attempt to bow the fibula, widening the disrupted syndesmosis. The external rotation test, also known as Kleiger’s maneuver, is another widely utilized exam. Placing the patient’s knee in flexion and ankle at 90 degrees, one then externally rotates the foot on the leg.

   A cadaveric study comparing these two maneuvers found the external rotation test to reproduce the greatest amount of widening of the syndesmosis.11 Palpating the extent of interosseous pain may provide prognostic information about the length of recovery time. Nussbaum and colleagues have shown the number of days missed from activity to be statistically related to the interosseous tenderness length.12

   As far as imaging goes, widening of the tibiofibular clear space is the most common radiographic sign to indicate syndesmotic widening. However, physicians often overlook occult widening of the tibiofibular clear space because small changes are difficult to identify. Radiographic studies evaluating syndesmosis widening are largely insensitive in that only a lack of tibiofibular overlap correlates with syndesmosis disruption.13

   While bilateral radiographic comparisons may be helpful, syndesmotic widening may not be apparent due to the concave morphology of the tibial incisura and overlap of the anterior tibial tubercle over the convex shape of the fibular tubercle. Therefore, one would not be able to identify syndesmotic widening due to fibular rotation and anterior-posterior translation.

   Computed tomography (CT) provides the best confirmation of diastasis and fibular rotation and translation at the level of the syndesmosis. A CT axial view enables you to compare quantitative measure of widening between the fibula and tibia to the contralateral syndesmosis.

   Utilization of magnetic resonance imaging (MRI) improves diagnostic accuracy if clinical exam findings are inconclusive.14 The MRI can identify specific syndesmotic ligaments that are disrupted and aid in providing a prognosis on return to activity.

   One may tailor treatment to the grade of injury. The West Point Ankle Grading System Classification is among the classification schemes for syndesmosis injuries but this system provides little prognostic information as the scale has not been validated.4 Grade I signifies stable injury, grade II denotes mild evidence of instability and grade III signifies complete instability.

Determining The Appropriate Course Of Treatment

The physician may treat a majority of high ankle sprains conservatively, provided that the syndesmosis is reduced and the ankle is stable. In the absence of frank diastasis, syndesmosis injuries are often stable provided that the deep deltoid ligament is intact. The only radiographic evidence of concomitant deltoid ligament injury is medial clear space widening greater than 4 mm.10 If medial clear space widening is not obvious, one may obtain an anterior–posterior projection stress radiograph with an external rotation test to determine if one can widen the medial clear space.15,16

   If you confirm the diagnosis of syndesmosis ligament injury and 4 mm of medial clear space widening is present on the radiograph, surgical intervention to achieve anatomic reduction and stable fixation can improve functional outcomes and facilitate a quicker return to activity.

   Reducing the fibula to the tibial incisura of the distal tibial syndesmosis is necessary to achieve anatomic healing and restore function of the ankle. However, malreduction of the syndesmosis is reportedly as high as 52 percent in trauma institutions and has been associated with poor functional outcomes.17

   One can achieve reduction by placing the pointed reduction forceps, either with a Weber or periarticular reduction forceps, across the biomechanical axis. This identifies the center of rotation of the ankle joint. Once you have achieved anatomic reduction of the syndesmosis, use either two parallel screws or suture fixation to achieve stable fixation.

A Guide To Conservative Treatment And Rehabilitation

There is little evidence in the existing literature to guide the rehabilitation of syndesmotic injuries. Rehabilitation protocols are therefore based on a patient’s level of activity and progress with recovery. Syndesmosis injuries requiring surgical intervention or grade III injuries will often require a six-week period of immobilization and non-weightbearing prior to rehabilitation.18 For competitive athletes, the timing of injury during the season and severity of injury will generally influence the course of treatment and rehabilitation.

   Immobilizing the injured ankle is the initial stage of treatment in addressing the acute inflammatory response of edema and pain. The grade of injury should determine the method of immobilization. Grade II and III injuries often require a short leg non-weightbearing boot for four to five days. Patients may remove the boot to perform passive range of motion exercises. Patients may use nonsteroidal anti-inflammatory drugs (NSAIDs), rest from the athletic activity, contrast baths, compression and elevation to decrease the swelling and pain from the acute injury.

   Functional treatment with a removable device also allows the use of ancillary therapeutic modalities such as cryotherapy or electrical stimulation. Research has shown that functional immobilization with taping, a lace-up ankle stabilizing brace, a double upright hinged ankle brace or a walking boot reduces the time it takes to return to work or sport, and reduces swelling in comparison to cast immobilization.19 Once the acute inflammation of injury has subsided, rehabilitation of the high ankle sprain may begin.

   In general, after five to six days, athletes may begin the second phase of rehabilitation. This entails transitioning to full weightbearing in functional bracing, such as the double upright, hinged ankle brace. This brace allows sagittal ankle range of motion while limiting external rotation stresses of the syndesmosis. Active assisted and active range of motion should begin with low intensity resistance and high repetition. Gait training and light proprioception exercises may begin at the patient’s tolerance.

   The ability to perform a repetitive, painless hop test is a common indicator that the patient is ready to transition to the final phase of rehabilitation.4,12 The third phase of rehabilitation involves continued protected full weightbearing in an ankle brace, resistive exercises, proprioception and multi-axial ankle movements.

   For athletes, rehabilitative measures are focused strength, balance and neuromuscular control while incorporating sport specific drills. If athletes are ready to return to sport, they must complete a battery of sport specific drills without pain or functional limitation.

When There Is A Delay In Treatment With Syndesmosis Injuries

Untreated syndesmosis injuries often result in chronic pain, instability and difficulty returning to pre-injury activities. Late stage reconstruction may be indicated if degenerative arthritic changes of chronic syndesmotic instability are not present. However, descriptions of late stage reconstructions of chronic syndesmosis injuries are mainly anecdotal and few articles detail long-term outcomes.

   Arthroscopic debridement and anatomic reduction with transsyndesmotic fixation may produce adequate fibrosis for syndesmosis function in athletic patients.20 To reduce pain and instability in high demand patients, one may use ligamentoplasty procedures with autologous or allograft peroneal longus graft to anatomically reconstruct the syndesmosis ligaments.21

In Summary

High ankle sprains are predictive of lingering pain and disability to the competitive athlete or high demand patient. By incorporating clinical exam findings with imaging results, one can diagnose, treat and appropriately rehabilitate the syndesmosis injury. Late stage reconstructions may be an option for chronic syndesmosis injuries in young patients without the onset of arthritic changes. However, current data does not produce conclusive evidence that late stage reconstructions produce satisfactory long-term results.

   Dr. Liu is an Assistant Professor in the Department of Orthopaedic Surgery with the Orthopaedic Foot and Ankle Trauma and Reconstruction Service at the University of Texas Southwestern Medical Center and Parkland Memorial Hospital in Dallas.

   Dr. VanPelt is an Assistant Professor in the Department of Orthopaedic Surgery with the Orthopaedic Foot and Ankle Sports Medicine Service at the University of Texas Southwestern Medical Center and Parkland Memorial Hospital.

   For further reading, see “A Guide To Treating Ankle Sprains From Start To Finish” in the July 2006 issue of Podiatry Today.




References:


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