Differential Diagnosis
- Jones fracture
- Pathologic fracture
- Fracture of the proximal diaphysis of the fifth metatarsal bone
- Osteomyelitis
- Lisfranc dislocation
Physical Examination
On physical examination, the patient has a temperature of 98.4°F (37°C), a pulse rate of 92 beats/min, a respiration rate of 20 breaths/min, a blood pressure of 128/78 mm Hg, and an oxygen saturation of 97% on room air. He is alert and oriented, is not in acute distress, and is breathing comfortably.
He has a regular heart rate and rhythm without murmur, rub, or gallop. His abdomen has a normal appearance and is soft and nontender without rigidity, rebound, or guarding. His lungs are clear to auscultation.
The patient’s right ankle does have swelling over the lateral malleolus, and there is pain with palpation of this site. There is pain with palpation over the proximal fifth metatarsal bone but no swelling in this area. There is no pain with palpation of the medial malleolus or over the midfoot. The ankle has a good range of motion with minimal pain in the anteroposterior distribution, but inversion is restricted because of pain. His dorsal pedal pulse is 2+. Sensation is grossly intact over the foot and toes.
Diagnosis
An x-ray is obtained (Figure 2) that shows a fracture of the proximal fifth metatarsal bone at the tuberosity (arrow). Note that the fracture line extends through the tuberosity but does not involve the metaphysis or proximal diaphysis.
Learnings
The fifth metatarsal bone approximates proximally with the cuboid bone and medially with the fourth metatarsal bone, bound in place by ligaments. These are the five aspects of the fifth metatarsal, from proximal to distal:
- Tuberosity (sometimes called the styloid)
- Metaphysis (a widened area of bone that articulates with the cuboid bone proximally and with the proximal fourth metatarsal bone medially)
- Proximal diaphysis (the long, narrow aspect of the bone ending in the distal fifth metatarsal)
- Neck
- Head
What to Look For
Patients may present with ankle pain from a strain but in fact may have a fracture of the proximal fifth metatarsal bone. This injury may be missed if it is not specifically evaluated. Classification of the fracture in the urgent care center is important because this may change treatment. A Jones fracture involves a specific location with fracture through the metaphysis; it is not an avulsion fracture of the tuberosity.
During the physical examination, do the following:
- Inspect for erythema, ecchymosis, and tenting of the skin.
- Palpate for the site of greatest pain, moving proximally, including the ankle, and distally.
- Gently check the range of motion.
- Use the Ottawa ankle rules, which have been validated.
Their use can decrease orders for x-rays by 30% to 40% in both adults and children. The rules consist of these points:
- The ability to walk four steps (to bear weight on the affected ankle twice)
- A lack of tenderness at the posterior edge of either malleolus
Typically, the x-rays ordered are the anteroposterior, oblique, and lateral views. If findings are negative on foot x-rays but the findings from the medical history and physical examination are very suggestive of a fracture, consider obtaining an ankle x-ray. The primary differentiation in urgent care is between a fracture of the tuberosity (an avulsion fracture), which is treated symptomatically, and a Jones fracture or fracture of the proximal diaphysis, which may require orthopedic expertise and possibly surgery.
Transfer the patient to an emergency department in the presence of the following:
- Associated major trauma
- The possibility of neurovascular compromise
- Compartment syndrome (the “5 P’s”)
- Pain
- Paresthesia
- Pallor
- Pulselessness
- Paralysis
- Uncontrolled pain
- Lisfranc or other dislocation in need of emergency reduction