Age / Sex : 18 / M

Chief complaint : Thigh pain (D: 1 month)

What is your impression?

Two weeks later, you can see the final diagonosis with a brief discussion of this case (Please submit only one answer).

Courtesy of Jin-Gyoon Park, Chonnam National University Hospital

Discussion

Answer:  

Longitudinal stress fracture

Findings:

AP radiograph of the femur demonstrates a faint longitudinal lucent line of the medial cortex with periosteal new bone formation. MR images show a longitudinal linear increased signal of the medial cortex with periosteal reaction and perilesional bone marrow and soft tissue edema.  Axial CT image shows a curvilinear lucency of the medial cortex with periosteal new bone formation.

Differential Diagnosis:

(Longitudinal) stress fracture

Osteomyelitis

Diagnosis:  

(Longitudinal) stress fracture

Discussion:

Stress fractures are mainly divided into fatigue fractures and insufficiency fractures. Fatigue fractures result from abnormal stress on a normal bone, occurring more frequently in unconditioned athletes and military recruits, while insufficiency fractures usually result from normal stress on an abnormal, weakened bone, usually in osteopenic patients. Usually, stress fractures in lower limbs are perpendicular to the long axis of the bone and are transverse in orientation, but rarely they can have a longitudinal orientation parallel to the long axis of the bone. Most longitudinal stress fractures have been reported in the tibia, and longitudinal stress fractures of the femur are rare. Radiographic findings include cortical thickening and an intracortical longitudinal fracture line. However, in many cases, findings may not be apparent on plain radiographs. Even if the longitudinal fracture line is evident, it may be mistaken for a normal nutrient artery canal. MRI usually demonstrates bone marrow edema and cortical thickening. MRI is less sensitive than CT for detection of fracture lines. Bone marrow edema on MRI will have broad differential diagnosis including trauma, stress, infection, inflammation, and tumors. CT is usually diagnostic and more sensitive than radiography for fracture. CT shows cortical thickening and intracortical longitudinal fracture line. Differential diagnoses for longitudinal stress fractures on radiographs include an osteoid osteoma in the absence of a visible fracture line.

References:

1. Kumar Y, Hayashi D, Hooda K, et al. Longitudinal stress fracture of the femur: a rare entity.

Connecticut Medicine 2017;81:31-33

2. Bilreiro C, Bahia C, Castro MO. Longitudinal stress fracture of the femur: a rare presentation. Eur J Radiol Open. 2016;3:31–34.


3. Kiuru MJ, Pihlajamaki HK, Ahovuo JA. Fatigue stress injuries of the pelvic bones and proximal femur: evaluation with MR imaging. Eur Radiol. 2003;13:605–611.


4. Williams M, Laredo JD, Setbon S, et al. Unusual longitudinal stress fractures of the femoral diaphysis: report of five cases. Skeletal Radiol. 1999;28:81–85.

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