Understanding ankle injuries

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A 15 year old male presents to the Emergency Department one day after sustaining a “twisting” injury to his left ankle while playing soccer. The patient claims to have sustained a “twisted ankle” while he was running towards the goal. He does not recall exactly in which direction his ankle twisted. He did not feel or hear any “snaps,” “pops,” or “clicks.” Although he was able to bear some weight on the ankle immediately after the injury, today he has much more pain and swelling about the anterior and lateral aspect of the affected ankle.

Overnight he did not elevate the ankle nor did he apply any ice to the injured ankle. He denies sustaining any other injuries and has not sustained any previous injury to his left ankle. This morning he is unable to walk on the ankle secondary to increased pain and swelling.

 

Exam findings

On examination, he is barely able to bear any weight on the affected ankle secondary to pain. There is obvious swelling (without ecchymosis) to the anterior and lateral aspect of the ankle joint. Distally, his toes are pink, with brisk capillary refill and intact sensation to light touch. Tenderness can be elicited by palpation over the anterior aspect of the ankle joint

The black arrow points to the region of maximum tenderness. There is no tenderness along the inferior tip of the lateral malleolus or over the bony prominence of the lateral malleolus. There is no tenderness along the medial aspect of the ankle or along the proximal aspects of both the tibial and fibular shafts. The squeeze test over the distal tibia-fibula region does not produce any pain. Both the anterior drawer and talar tilt maneuvers are within normal limits when compared to the nonaffected ankle.

 

Questions

  • Has this patient sustained a typical ankle sprain?
  • What is the typical mechanism of injury for the majority of ankle sprains sustained during sporting events?
  • Which ankle ligament is most commonly sprained during an inversion injury, and where on the ankle should one palpate to check for tenderness to this ligament?
  • Describe the anterior drawer test and what specifically does this maneuver test for?
  • Describe the talar tilt test and what specifically does this maneuver test for?
  • What is the syndesmosis, and how does one examine for possible syndesmotic injuries?

 

Discussion & teaching points

Ankle injuries are one of the most common sports-related orthopedic injuries seen in the Emergency Department. These types of injuries are most commonly sustained in patients between 15 – 35 years of age. The majority of ankle sprains (up to 85%) are due to inversion injuries while only 15% are due to eversion-related injuries. There are 3 lateral ankle ligaments and one broad, fan-shaped medial ligament.

Although ankle sprains are common in older adolescent patients and young adults, isolated ankle sprains are not very common in younger children and in preadolescent patients. The physis (growth plate) in these younger children is much weaker than the surrounding ligaments, and is thus more susceptible to injury. Therefore in the pediatric population, injuries involving the growth plates (Salter-Harris injuries) must also be considered in addition to ligament sprains.
The anterior talofibular ligament (ATFL) is the weakest of the 3 lateral ligaments and is the most commonly injured of the lateral ankle ligaments. (Note that ATFL can also stand for anterior tibiofibular ligament, however, in this case, ATFL will be used to stand for anterior talofibular ligament.) 65% of lateral ligament sprains are confined to the ATFL alone, while 20% have concomitant calcaneofibular ligament (CFL) tears. The ATFL can be palpated just inferior and anterior to the distal most aspect of the lateral malleolus.

The white arrow points to the region of the ATFL. Because the patient in this case has point tenderness in an area other than over the ATFL, he has therefore not sustained a typical ankle sprain. In comparison to these lateral ligaments, the medial, deltoid ligament has a fair degree of elasticity and is much more resistant to tears. Most injuries also occur while the ankle joint is in plantar flexion rather than in dorsiflexion. Anatomically, the talar dome is wedge-shaped, with the anterior aspect of the talus being wider than the posterior aspect.

During dorsiflexion, this wider, anterior aspect of the talus is engaged within the mortise (formed by the distal tibia and fibula), and the joint is very stable. However during plantar flexion, the narrower, posterior aspect of the talus becomes engaged in the ankle mortise.

Note the obvious widening of the joint space during plantar flexion on the left compared to dorsiflexion on the right. Thus, with this understanding of the articulation of the talus within the mortise, it is not surprising that most ankle injuries occur while the ankle is in plantar flexion, rather than in dorsiflexion.

The last part of the clinical examination of an injured ankle involves assessing the stability of the ankle joint. The two maneuvers that can be performed to assess the stability of the ankle joint are the anterior drawer and talar tilt maneuvers. Keep in mind that the ability to perform these tests and the results immediately after an injury may be limited by swelling, pain and muscle spasm. Do not attempt to perform either of these tests if there is an obvious deformity of the ankle suggestive of a possible ankle fracture.

The ATFL ligament normally prevents the anterior subluxation of the talus from the mortise. The talus may be subluxed anteriorly whenever the ATFL is partially ruptured (second-degree sprain) or completely ruptured (third-degree sprain). The anterior drawer maneuver assesses the integrity of the ATFL. Since the ATFL is usually the first ligament to be injured in a typical inversion injury, some physicians feel that if this anterior drawer test is negative, it is then unnecessary to perform the talar tilt maneuver (since the talar tilt stress test is positive only if both the ATFL and the CFL are injured).

To perform the anterior drawer maneuver, the patient can either be supine or sitting down, with the ankle in neutral position. One hand of the examiner cups the heel of the affected ankle (and attempts to pull the foot anteriorly), while the other hand braces along the anterior aspect of the lower leg.

If the foot of the affected ankle can be pulled forward by more than 3-5 mm (or if the affected ankle can be subluxed more forward than the nonaffected side), suspect a rupture of the ATFL. The talar tilt test assesses the integrity of the CFL. To perform this maneuver the patient can again be either sitting down or supine, with the ankle in neutral position. While one hand of the examiner holds the lower leg stationary, the other hand gently attempts to invert the ankle.

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Greater than 10 degrees of difference in the talar tilt when compared to the nonaffected side is suggestive of an injury to the CFL.

Proximal to the lateral and medial ankle ligaments, the distal tibia and distal fibula are connected to each other by a series of tough fibrous structures collectively referred to as the tibiofibular syndesmosis. The three individual components which make-up this syndesmosis include: a) anterior tibiofibular ligament, b) posterior tibiofibular ligament, and c) intraosseous membrane.

Note that on this diagram, the PTFL stands for the posterior talofibular ligament (not the posterior tibiofibular ligament). The posterior tibiofibular ligament is NOT drawn on this diagramatic view.

Clinically one can check for injuries of the tibiofibular syndesmosis by the squeeze test. To perform this test, the examiner firmly grasps the patient’s lower leg (around the lower aspect of the calf), and gently squeezes the tibia and fibula together.

Provided that there are no fractures of the tibial or fibular shafts, if ankle pain can be elicited by this squeeze maneuver, one should suspect an injury to one or more of the components of the tibiofibular syndesmosis.

Questions

  • What are some clinical criteria that would warrant a radiographic examination of an injured ankle?
  • What are the 3 standard radiographic views that are obtained on patients with ankle injuries?
  • When do the distal tibial and distal fibular epiphyses appear, and by what age do these epiphyses fuse to the adjacent metaphyses?

 

Discussion & teaching points

It is estimated that over $500 million dollars are spent each year on ankle radiographs. However the majority (up to 85%) of these radiographs are negative.

In 1992, a Canadian study suggested the adaptation of the Ottawa ankle rules, which could be used to order ankle radiographs based on selected clinical criteria. It is important to remember that this study excluded patients younger than 18 years of age. Therefore, since the Ottawa study did not include growth plate injuries, one should not strictly adhere to these rules when deciding whether or not to obtain a radiograph on a pediatric patient.

Based on these Ottawa ankle rules, clinical indications that would warrant a radiographic evaluation would include any one of the following criteria:

  • Inability to bear weight both immediately after the injury and in the Emergency Department.
  • Bony tenderness over the posterior edge, tip or distal 6 cm of the lateral malleolus.
  • Bony tenderness over the posterior edge, tip or distal 6 cm of the medial malleolus.
  • Tenderness over the base of the 5th metatarsal.

A complete, standard radiograph examination of the ankle should include 3 views (AP, lateral, and a mortise view).

AP view

There are several findings that can be observed on the AP view. The tip of the lateral malleolus normally extends more distally than the tip of the medial malleolus. The syndesmosis of the ankle joint normally causes an overlap of the medial aspect of the distal fibula and the lateral aspect of the distal tibia on this AP view. Therefore, subtle fractures involving either the lateral aspect of the distal tibia or the medial aspect of the distal fibula (i.e. between the tibia and fibula) may be difficult to visualize on this AP view alone because of the overlap.

It is a common pitfall to miss a Salter Harris Type III fracture of the distal lateral tibia because it is obscured by the overlapping fibula.

 

Lateral view

On a true lateral view, the malleoli should be superimposed upon one another. The lateral view provides a better view of the posterior aspect of the distal tibia and fibula, the talus, calcaneus and the base of the 5th metatarsal.

 

Mortise view

To obtain a better view of the ankle mortise, the patient’s leg must be internally rotated just enough so that the lateral malleolus (which is normally posterior to the medial malleolus), is on the same horizontal plane as the medial malleolus, and a line drawn through both malleoli would be parallel to the tabletop. Usually this only requires approximately 10-20 degrees of internal rotation. In other words, when viewing the mortise view, the tibia and fibula must be viewed without superimposition on each other.

This mortise view represents a true AP projection of the ankle mortise and also provides a good visualization of the talar dome (to rule-out osteochondral talar dome fractures). The clear joint space [formed by the talofibular joint, the superior space between the dome of the talus & the tibial plafond (the inferior articulating surface of the tibia) and the tibiotalar joint] should all uniformly measure 3-4 mm. A difference of greater than 2 mm (i.e. the joint space width varies by more than 2 mm. Eg., Joint space measures 2 mm at lateral part of joint and 5 mm at medial side of joint.) is suggestive of mortise instability.

 

If all of the above 3 views appear normal in a patient with a high clinical suspicion of a fracture, one should then obtain internal and external oblique views of the ankle to obtain additional views of the distal tibia and distal fibula. To obtain such views, the patient’s leg is rotated 45 degrees internally, then 45 degree externally.

The epiphyses of the distal tibia and fibula both appear by 2 years of age. The physis of the distal tibia fuses to its adjacent metaphysis by 18 years of age. The physis of the distal fibula fuses to its adjacent metaphysis by 20 years of age. Therefore, growth plate injuries should still be considered as a possibility in any patient up to 20 years of age.

If one is unsure if a radiolucent line involving the distal tibia or fibula represents either a physis or an actual fracture, consider obtaining a comparison view of the nonaffected ankle. An x-ray of the patient’s ankle was obtained.

How would you interpret these 2 views? Oblique and mortise views were also obtained because of the physical exam findings.

What does this mortise view reveal that may not have be very evident on the 2 previous views?

[DDET View radiology comments]

There is a moderate amount of soft tissue swelling over the lateral malleolus. The AP and lateral views do not reveal any obvious fractures. However, there is a subtle widening of the medial aspect of the distal fibular growth plate (physis) on the mortise view.

Comparative views and/or stress views would confirm that this is a fracture versus a normal growth plate closure. [/DDET]

 

Questions

  • Does this patient require immediate orthopedic intervention or can he be sent home from the Emergency Department with an out-patient orthopedic referral?
  • If you would send this patient home, what type of dressing or splint would you apply?

 

Discussion & teaching points 

This patient has sustained a nondisplaced Salter-Harris type I fracture of the distal fibula (lateral malleolus). Clinical and or radiographic criteria that would warrant immediate orthopedic intervention include:

  • An open fracture.
  • Any type of injury with neurovascular compromise.
  • Any unstable fracture (which would be difficult to adequately immobilize in a splint).
  • Any ankle dislocation (which tends to carry a high risk of neurovascular compromise).

Since this patient does not have an open fracture, dislocation or evidence of neurovascular compromise, his stable fracture does not require an immediate orthopedic intervention. Therefore, this patient may be immobilized in an appropriate splint and sent home with an orthopedic referral for definitive casting. A posterior ankle splint would probably not be adequate immobilization by itself for an ankle fracture.

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The posterior splint is on the left. The sugartong (or stirrup) splint is on the right. An ankle stirrup splint would provide better immobilization, since it protects against inversion-eversion and to some degree also protects against a fair degree of flexion-extension. The stirrup splint can also be combined with the posterior splint to provide maximal immobilization and protection against further trauma to the injured ankle.

Patients should be told to refrain from weight-bearing (use crutches) and to elevate the injured extremity as much as possible.

 

References

Anderson AC. Injury: Ankle (Chapter 35). In: Fleisher GR & Ludwig S (eds). Textbook of Pediatric Emergency Medicine, Third Edition. Baltimore, Williams & Wilkins, 1993, pp. 259-267.

Harris JH, Harris WH, Novelline RA. The Ankle (Chapter 14). In: The Radiology of Emergency Medicine. Williams & Wilkins, 1993, pp. 966-1009.

Jackson JL, Linakis JG. Ankle and Foot Injuries. In: Barkin RM, et al (eds). Pediatric Emergency Medicine: Concepts and Clinical Practice. St. Louis, Mosby Year Book, 1993, pp. 366-375.

Pigman EC, Klug RK, Sanford S, et al. Evaluation of the Ottawa clinical decision rules for the use of radiography in acute ankle and midfoot injuries in the emergency department: An independent site assessment. Ann Emerg Med 1994;24;41-45.

Reisdorff EJ, Cowling KM. The injured ankle: New twists to a familiar problem. Emerg Med Reports 1995;16;39-48.

Simon RR, Koenigs SJ. The Ankle (Chapter 30). In: Emergency Orthopedics, The Extremities, Third Edition. Norwalk, Appleton & Lange, 1995, pp. 477-489.

Stiell IG, McDowell I, Nair RC, et al. Use of radiography in acute ankle injuries: Physician’s attitudes and practice. Can Med Assoc J 1992;147:1671-1678.

Stiell IG, McKnight RD, Greenberg GH. Decision rules for use of radiography in acute ankle injuries: Refinement and prospective evaluation. JAMA 1993;269:1127-1132.

Swischuk LE. The Extremities (Chapter 4). In: Emergency Imaging of the Acutely Ill or Injured Child, Third Edition. Baltimore, Wiliiams & Wilkins, 1994, pp. 528-548.

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Prof Loren Yamamoto MD MPH MBA. Professor of pediatrics at the University of Hawaii and a practising pediatric emergency doctor in Honolulu. | Contact | View Loren's DFTB posts