Age / Sex : /

Chief complaint: right thigh pain for 2 months

1) What is your impression?

Two weeks later, you can see the final diagnosis with a brief discussion of this case.

(Quiz는 quiz일 뿐이오니 답안은 한개만 보내주시기 바라오며, 복수의 답안을 보내주시는 분은 정답이 포함되어 있더라도 부득이 semi-correct answer로 처리토록 하겠습니다.)

Intracortical abscess

Discussion

Findings:

Radiography

- oval-shaped osteolysis with irregular margins in right femur proximal diaphysis

- vertical bony fragment within the osteolytic lesion, suggestive of sequestrum

- single layer periosteal reaction

MRI

- elongated cortical lesion at posterior side of right proximal femur

- central hypointense sequestrum mimicking calcified nidus

- extensive bone marrow edema and soft tissue edema

Differential Diagnosis:

1. Intracortical abscess

2. Osteoid osteoma

Diagnosis: Intracortical abscess

Discussion: In 1940, Jaffe and Lichtenstein described an osteoid osteoma as “osteomyelitis or abscess of the bone.” Before this description, osteoid osteomas were classified as intracortical bone abscesses or sclerosing nonsuppurative osteomyelitis. Several conditions have imaging findings that may mimic osteoid osteoma, such as localized cortical thickening, reactive sclerosis surrounding an osteolytic lesion, and bone marrow edema. These conditions include stress fracture, intracortical abscess and intracortical hemangioma

 When abscess is located in the cortex, its radiographic appearance, consisting of a lucent lesion with surrounding sclerosis and periostitis, simulates that of an osteoid osteoma or a stress fracture. A rounded radiolucent lesion without calcification is characteristic of a cortical abscess. At radiography, however, an intracortical abscess and an osteoid osteoma often are indistinguishable. When a sequestrum is present, like in this case, the appearance of an intracortical abscess is very similar to that of an osteoid osteoma with a calcified nidus. Sequestration of a piece of cortical bone is less frequent and usually takes the appearance of a Brodie's abscess. In childhood, bone necrosis is facilitated by the deprivation of blood supply to the inner portion of the cortex, which is caused by thrombosis of the metaphyseal vessels and interruption of the periosteal vessels. Cortical necrosis and sequestration can subsequently appear.

References:

1. Jaffe HL, Lichtenstein L. Osteoid-osteoma: further experience with this benign tumor of bone—with special reference to cases showing the lesion in relation to shaft cortices and commonly misclassified as instances of sclerosing non-suppurative osteomyelitis

or cortical-bone abscess. J Bone Joint Surg Am 1940;22:645–682

2. Chai JW, Hong SH, Choi JY, Koh YH, Lee JW, Choi JA, Kang HS. Radiologic diagnosis of osteoid osteoma: from simple to challenging findings. Radiographics 2010;30:737-749

3. Resnick D. Osteomyelitis, septic arthritis, and soft tissue infection: mechanism and situation. In: Resnick D, Kransdorf MJ, eds. Bone and joint imaging. 3rd ed. Philadelphia, Pa: Saunders, 2005; 713-742

4. Jennin F, Bousson V, Parlier C, Jomaah N, Khanine V, Laredo JD. Bony sequestrum: a radiologic review. Skeletal Radiol 2011;40:963-975