Magnetic resonance imaging of an osteoid osteoma of the proximal femur: a potentially confusing appearance

A case report of an unrecognized osteoid osteoma of the proximal femur

We present the case of a 59-year-old male patient with unrecognized osteoid osteoma in radiography as well as in magnetic resonance imaging. Computed tomography revealed osteoid osteoma that was successfully treated with percutaneous computed tomography guided radiofrequency ablation. The osseous pathology was underestimated on magnetic resonance imaging in the presented case and bone marrow edema led to incorrect diagnosis. The particular case emphasizes the value of computed tomography scans diagnosing an osteoid osteoma.

Osteoid osteoma

Osteoid osteomas consist of a nidus with surrounding sclerotic bone. The differential diagnosis covers a wide range of conditions due to the variable presentation of osteoid osteoma. The natural history is for regression to occur within 6 to 15 years with no treatment; however, this can be reduced to 2 to 3 years with the use of aspirin and non-steroidal anti-inflammatory drugs. Computed tomography-guided percutaneous techniques, including trephine excision, cryoablation, radiofrequency ablation, and laser thermocoagulation, are described.

Percutaneous CT-guided curettage of osteoid osteoma with histological confirmation: a retrospective study and review of the literature

Osteoid osteoma is a benign bone tumour usually occurring in young individuals (10-30 years). It presents with intense pain (typically nocturnal), which can be alleviated by salicylates. Treatment consists of surgical excision or destroying the nidus and it is curative. In the past, surgery was performed in an "open" fashion and the nidus had to be removed with a bone block. This extensive type of surgery could be associated with some rates of both failure and complication. There is growing evidence to suggest that percutaneous CT-guided removal or destruction of the nidus is a good alternative and it is indeed gaining worldwide popularity. We present a series of 18 consecutive patients with osteoid osteoma of the pelvis, femur, and tibia, treated percutaneously under CT guidance. Removal of the nidus was performed using a 4.5-mm cannulated drill and a cannulated curette of our own design. Tissue samples for histological evaluation were obtained in the same way. The mean follow-up time was 29 months. Sixteen patients were initially cured. The procedure had to be repeated in two patients and was eventually successful (primary and secondary success rates 88 and 100% respectively). The diagnosis was histologically confirmed in 14 cases out of 18 (77%). In four cases no histological confirmation of osteoid osteoma could be achieved. There were only two minor complications, one case of femoral neuropraxia and one case of skin abrasion. Percutaneous CT-guided removal seems to be efficient and safe for the treatment of osteoid osteoma. The use of a cannulated drill and a cannulated curette facilitates efficient removal of the tumour and procurement of tissue for diagnosis.

Primary bone tumors of the femur presenting with spinal symptoms: a report of two cases and review of the literature

Two case reports of femoral bone lesions simulating lumbar spinal disease are presented. Physical examination and case history were strongly suggestive of lumbar spinal pathology. In case 1, surgical resection of a venous hemangioma in the lumbar epidural space was performed but did not relieve pain. In case 2, conservative treatments for a protruded disk were performed for 3 months before an accurate diagnosis was made. After correct diagnoses were made, excision of the femoral tumors brought rapid relief of all abnormal findings in both cases. Compared with other causes of sciatica, femoral bone tumors are rare. However, careful attention should be paid to rule out these lesions if the diagnosis of a lumbar spinal disease is uncertain. Bone scintigraphy seems to be a sensitive diagnostic method to detect extraspinal osseous lesions.

Preoperative CT localization and marking of osteoid osteoma: description of a new technique

We describe a new technique for the preoperative localization of an osteoid osteoma nidus. Four lesions (mean patient age 26 years) were localized with CT. A needle was advanced into the cortex, methylene blue was injected, and a self-retaining localization wire was then left in place. A final CT image confirmed localization. The site of marking was identified intraoperatively by following the guide wire to the cortical mark, permitting nidus excision with minimal resection of bone.

MR imaging of edema accompanying benign and malignant bone tumors

To evaluate the incidence, quantity, and presentation of intra- and extraosseous edema accompanying benign and malignant primary bone lesions, the magnetic resonance (MR) studies of 63 consecutive patients with histologically proven primary bone tumors were reviewed. MR scans were assessed for the presence and quantity of marrow and soft tissue edema and correlated with peroperative findings, resected specimens and follow-up data. The signal intensity and enhancement of tumor and edema prior to and after intravenous administration (if any) of gadolinium-labeled diethylene triamine pentaacetate (Gd-DTPA) was analyzed. Marrow edema was encountered adjacent to 8 of 39 malignant tumors and 14 of 24 benign lesions. Soft tissue edema was found accompanying 28 of 39 malignancies and 10 of 24 benign disorders. On unenhanced T1-weighted MR images tumor and edema were difficult to differentiate. Tumor inhomogeneity made this differentiation easier on T2-weighted sequences. In 36 patients the contrast medium Gd-DTPA was used. Edema was present in 27 of these patients and the respective enhancement of tumor and edema could be compared. Edema always enhanced homogeneously, and in most cases it enhanced to a similar degree as or more than tumor. Marrow and, more specifically, soft tissue edema is a frequent finding adjacent to primary bone tumors. The mere presence and quantity of marrow and soft tissue edema are unreliable indicators of the biologic potential of a lesion. Unenhanced MR scans cannot always differentiate between tumor and edema, but the administration of Gd-DTPA is of assistance in differentiating tumor from edema.(ABSTRACT TRUNCATED AT 250 WORDS)

Magnetic resonance imaging of inflammatory reaction in osteoid osteoma

Between 1988 and 1993, 16 cases of osteoid osteoma were examined by magnetic resonance imaging (MRI). MRI clearly visualized the extent of inflammation in the bone marrow and soft parts that is difficult to observe with other diagnostic techniques. The degree of inflammation varied among the patients. This might be associated with the anatomical relationship between the nidus and the cortex. The high sensitivity of MRI, unfortunately, may lead to an erroneous interpretation in lesions accompanied by inflammatory responses of the bone marrow or soft parts, such as osteoid osteoma. However, these reactions on MRI may offer a key to the pathogenesis of osteoid osteoma, a unique bone neoplasm.