Disclosures: Robert A. Churchill: No financial relationships or conflicts of interest

Case Diagnosis: Patient presenting with 9-year history of unexplained right thigh pain is found to have an osteoid osteoma in her femur.

Case Description or Program Description: A 46-year-old female patient with history of metastatic rectal cancer was referred for evaluation of 9-year history of right thigh pain. Symptoms were not precipitated by injury. Previous evaluations including lumbar spine MRI and hip/pelvis radiographs and MRI could not determine an etiology. Pain was localized to the right anterior hip and thigh to the knee. She rated her pain a “10/10” both with sitting and walking and reported nightly sleep interruptions due to pain. She demonstrated a mildly antalgic gait with tenderness throughout the right buttock, lateral hip, and circumferential thigh. Right femur radiograph showed dense cortical thickening centered posteriorly along the mid to distal femoral shaft with underlying cortically based lucencies. MRI appeared consistent with multifocal osteoid osteoma. CT guided biopsy obtained was consistent with AE1/AE3 negative osteoid osteoma.

Setting: Outpatient Rehabilitation Clinic at a tertiary medical center

Assessment/Results: MRI results and biopsy were consistent with osteoid osteoma. Given history of metastatic cancer, her oncologist wanted to wait 2 years from her last treatment before re-evaluating for orthopedic recommended extended intralesional curettage with rod stabilization. While awaiting surgery, symptoms improved with nonsteroidal anti-inflammatory drug (NSAID) treatment.

Discussion (relevance): Osteoid osteomas are benign bone tumors that typically occur in long bones and cause night pain relieved with NSAIDS. Misdiagnosis and delayed diagnosis are common with osteoid osteoma, which contributes to prolonged suffering for patients. While the lumbar spine and hip/pelvis are common sources of thigh pain, the differential must include local diagnoses in the thigh. One should consider the presence of atypical symptoms (e.g. prominent nighttime pain) when formulating the differential diagnosis.

Conclusions: It is important to consider a broad differential diagnosis for localized pain without clear explanation, especially if atypical features are present.

Level of Evidence: Level V

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PM&R Meeting Abstracts - https://pmrjabstracts.org/abstract/chronic-leg-pain-secondary-to-undiagnosed-multifocal-osteoid-osteoma-a-case-report/