Mrs. R is a 49-year-old married, White, female who presents to the urgent care center complaining of ankle pain following an injury last night. She states she got out of bed during the night, slipped on a stack of magazines, and fell to the floor. She had some difficulty walking immediately after the injury. Her husband helped her elevate her leg and applied ice and a compression bandage immediately after the injury. She describes the pain as continuous and throbbing, and rates it as a 7 on a scale of 0 to 10. Mrs. R's past medical history is significant for hypertension, well controlled with lisinopril. Additionally, she takes 1,200 mg of calcium carbonate and 600 international units of vitamin D per day. She reports that her mother experienced a hip fracture at age 68. She drinks 2 to 3 cups of caffeinated coffee each morning and a glass of white wine each night. She denies recreational drug or tobacco use. She is physically active, walking 5 times per week for 60 minutes, and is upset that the injury will impair her exercise schedule. She is still menstruating, but her periods have become irregular lately. Her last menstrual period was 5 weeks ago.

Mrs. R's physical exam reveals she is thin (BMI 21) and has some difficulty walking around the exam room due to pain in her left ankle. Examination of the left ankle reveals it to be moderately swollen with some ecchymosis laterally. Mrs. R has limited flexion and extension, and her ankle is tender to palpation both laterally and medially (see Normal bony structures of the ankle). Her distal pulses and sensation are intact. The differential diagnoses for Mrs. R are fracture versus ankle strain. An X-ray of the left foot and ankle (three views) was ordered to help confirm the diagnosis.

Ottawa ankle rules

In 1992, medical staff working in the ED at the University of Ottawa evaluated clinical findings in patients with ankle and mid-foot injuries. The group attempted to develop a system to help providers determine the need for X-rays after an ankle injury. The study group determined that the only aspects of the physical exam with interrater reliability were the patients' ability to walk four steps at the time of the injury and in the ED, and tenderness with palpation over the bony portions of the lateral and medial malleoli, the navicular, and the proximal fifth metatarsal.1 Based on this study, the group developed the Ottawa ankle rules. Ankle X-rays are required if there is pain in the malleolar zone and: bone tenderness along the distal 6 cm of the posterior edge of the tibia or tip of the medial malleolus, or bone tenderness along the distal 6 cm of the posterior edge of the fibula or tip of the lateral malleolus, or an inability to bear weight both immediately and in the exam room for four steps.1 When initially developed, these rules were determined to have a 98% sensitivity and a 40% specificity for excluding fractures based on the initial derivation study and several validation studies.2,3 More recently, a meta-analysis including data from 27 high-quality studies involving over 15,000 adults and children revealed a 98% sensitivity and a 20% specificity in using the Ottawa rules to exclude fracture.4

The Ottawa ankle rules can assist NPs in reducing the amount of unnecessary X-rays, resulting in lower medical cost and decreased radiation exposure for patients. However, the easy access to radiology equipment and the fear of litigation over missed fractures often lead to X-ray orders for most patients presenting with injury and subsequent pain, regardless of the result of the Ottawa ankle rules.

X-ray views

Typically, the standard radiographic exam of the ankle consists of three views. These are the anteroposterior, mortise, and lateral views. The mortise view includes tibial plafond, medial and lateral malleoli. Widening of the mortise medially is usually suggestive of a ligament injury and, in most cases, requires surgical repair.5

Testing results

Radiographs of Mrs. R's ankle revealed an oblique fracture of the distal fibula and a widening of the mortise medially. She was treated for her ankle pain and admitted to the hospital for an open reduction and internal fixation procedure. After successful surgery, immobilization, and physical therapy, Mrs. R was advised that she could gradually return to her previous level of exercise. Additionally, it was recommended that she obtain a bone mineral density test at a local diagnostic center.

Making the right diagnosis

Careful history and physical exam are the foundations for an accurate diagnosis. Knowledge of specific testing that can assist with clinical reasoning and the judicious use of diagnostic testing should result in positive outcomes for patients.

Mrs. R experienced a fracture due to a traumatic event. However, her perimenopausal status, thin body habitus, and family history of maternal fracture put her at risk for postmenopausal osteoporosis. Her bone density status should be examined to determine current bone density and subsequent risk of future fractures.

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