To review, this is a 23 year-old female with right ankle pain after fall.
Questions and Answers: 1) What is this patient's orthopedic injury?
This patient has severe right lateral ankle swelling and tenderness in the context of normal x-rays. She has no distal fibular fracture, tibial fracture, or mortise widening concerning for an unstable or fractured ankle. This patient has an ankle sprain.
Ankle sprains can be diagnosed without x-rays in patients who meet the Ottawa Ankle Rules, which have been demonstrated to have a sensitivity of ankle sprain without fracture of 92-100%.
The Ottawa Ankle Rules are as follows:
1) absence of bony tenderness to distal 6cm of posterior edges of medial and lateral malleolus
2) ability to bear weight for 4 steps immediately after the injury
3) ability to bear weight for 4 steps immediately prior to the injury
2) What further tests should you attempt in the emergency department?
Patients with isolated sprains should be assessed for both severity of the ankle sprain and an associated syndesmotic sprain. The ankle joint is stabilized by 3 sets of ligaments: the lateral, the medial, and the syndesmotic. As you can see above, the lateral complex (which comprises the majority of ankle sprains) involves anterior, posterior, and the more central calcaneofibular ligament. Lateral ankle sprains that involve all three ligaments, or medial sprains that involve the complete deltoid ligament complex are considered to be grade III sprains and have a high risk of progressing to chronic ankle instability and occasionally require surgical fixation.
The syndesmotic complex, comprised of the interosseus membrane and anterior and posterior inferior tibiofibular ligament, can also be sprained, and grade III sprains also can require operative repair.
Formal recommendations for evaluation of high grade medial and lateral ankle sprains include the "anterior drawer test," in which the provider stabilizes the distal tibia and fibula and translates the calcaneotalar complex anteriorly, comparing the laxity of the injured ankle to the noninjured ankle. A positive test is said to be > 2mm of increased laxity in the injured ankle when compared to a noninjured ankle. High grade syndesmotic sprains can be diagnosed by a squeeze test, in which the examiner puts compressive horizontal pressure on the distal tibia and fibula 6-8 cm proximal to the area of ankle pain. Pain with this maneuver is said to be positive for syndesmotic sprain (specificity 88%). Providers can also assess for syndesmotic sprain with the external rotation test, in which the provider stabilizes the distal tibia and externally rotates the fibula/talus/forefoot complex, comparing the laxity of the injured ankle to the noninjured ankle.
However, these maneuvers are frequently limited because of acute pain and swelling, and studies have shown that the maneuvers are more sensitive and specific when the patient is examined 3-4 days after acute injury. If a patient is unable to tolerate tests or unable to ambulate because of pain (like this patient), they are at higher risk for grade III ankle sprain and can be more accurately reassessed in an outpatient setting.
3) What is the appropriate emergency department management for this patient's injury (and what if this patient was a child)?
Patients with severe ankle sprains as above or those with obvious grade III ankle sprains by provocative testing should be made non-weightbearing for 3-5 days during the most significant period of swelling. They should also be treated with removable splint or stabilization such as an aircast. If the patient has had no improvement in pain or range of motion after this period, they should follow-up with a primary care physician for repeat films and examination for associated injuries. At this point, the patient may tolerate an exam that can differentiate between grade II and III ankle sprains and be referred to orthopedics as needed.
If a patient is able to ambulate and has negative provocative testing, they most likely have a grade I ankle sprain and can be given an airsplint to use as needed while performing normal activity.
Traditionally, children ages 5-12 with similar injury mechanisms, exams, and x-rays, were thought to have salter harris I fractures; as such, casting and orthopedic follow-up were recommended. And in terms of obtaining x-rays, the Ottawa Ankle Rules have proved robust in children as young as 5 years old. However, recent studies show that rates of salter harris I fractures and occult fibular avulsion fractures in x-ray negative ankle injuries are 3% and 36% respectively. More importantly, patients with occult fractures had no difference in return to function or pain when treated with removable aircast as recommended for patients with true sprains. It is appropriate to treat children with radiographically negative lateral ankle pain with aircast alone and crutches for comfort when the mechanism is reassuring against serious fracture.
Normal ankle radiographs courtesy of Dr Craig Hacking, Radiopaedia.org, rID: 37495
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