Tibial Stress Fracture - Diagnosis
Tibial stress fracture is one of several conditions that can present with exercise related leg pain. Early suspicion and identification of a tibial stress fracture are critical to proper treatment and successful outcomes.
Stress fractures usually present with a gradual onset of pain during activity, and usually develops when there has been an increase in training load. Pain worsens during running and other impact activity and is alleviated with rest.
Physical examination reveals focal tenderness at the site of the stress fracture over an area of typically 2-3 cm. Tenderness in an area of more than 5 consecutive cm indicates medial tibial stress syndrome (commonly known as «shin splints»).
In addition to pain on palpation, pain is often provoked by single leg hops, tibial bending/fulcrum test and/or vibration test with a 120 Hz tuning fork (1,2). The tuning fork test has low sensitivity and specificity (75 % and 67 %) in diagnosing stress fractures, and should not be used as a stand-alone test (2,3). If there is a suspicion of an anterior tibial stress fracture (high-risk stress fracture), fulcrum testing and single leg hop test should be performed with caution.
Radiographic imaging («X-rays»)
A plain radiograph is often the first-line imaging for a suspected stress fracture (4). However, radiographs are insensitive to early stress fractures (10 % sensitivity) and may be negative for several months after injury (2,5). In the majority of individuals with a stress fracture, conventional radiographs are negative both at presentation and on follow-up examinations.
The reason for this is that a cortical fracture line is infrequently seen. The only way to detect a stress fracture on plain radiographs is to look for signs of bone remodeling, including callus formation, cortical bone thickening, and increased bone mineral density in the affected area (2,4,5), which may take weeks or evens months to become visible (32).
Despite being insensitive to stress fractures, radiographic imaging is still being used as first-line imaging around the world. It is cheaper and more readily available than other imaging modalities (6), it manages to diagnose some stress fractures, and it excludes the more serious conditions, including "the dreaded black line" which is a fracture line in the anterior tibial cortex.
Magnetic resonance imaging (MRI)
MRI is considered the test of choice for early diagnosis of stress fractures. It is extremely sensitive (sensitivity 100 %, specificity 85 %) (2,4), and are able to diagnose stress fractures within 1-3 days after onset of symptoms (7).
The typical MRI appearance of stress fracture include periosteal edema, adjacent soft tissue edema, band-like bone marrow edema, and a T1 hypointense fracture line in a high-grade injury (4). Although bone marrow edema is decidedly non-specific (it occurs frequently even in non-symptomatic runners), it is very sensitive for very early stress response (4).
Exercise related leg pain can be related to several conditions. A thorough physical examination and medical history is important to make the correct diagnosis. Among conditions that may present with similar symptoms are medial tibial stress syndrome (shin splints), chronic exertional compartment syndrome, popliteal artery entrapment syndrome (PAES), leg muscle strains, and lower leg tendinopathies.