17-year-old male patient with chronic pain in the right ankle, without pathological or traumatic history. The pain partially improves with non-steroidal anti-inflammatory drugs and is exacerbated by palpation and during nighttime. Laboratory analytics are within normal limits.
Non-contrast CT and MRI ankle scans were performed using T1, T2, PD, and fat-suppression sequences in a Philips Ingenia 1.5T high-field MRI scanner and a Philips Incisive 128-slice CT scanner.
Initial MRI shows talus bone marrow oedema, anterior talofibular ligament’s partial tear, and increased joint fluid (Figures 1a and 1b). The CT scan shows cortical deformation in the distal and dorsal aspects of the talus associated with the talar beak (Figures 2a and 2b). The scintigraphy showed radiotracer uptake in the tibiotalar joint, extending up to the tibia, distal fibula, and tarsus (Figure 4). Control MRI scan revealed a T1 hypointense cortical lesion with a 6 mm maximum diameter, adjacent to the talar beak (Figures 5a and 5b). This lesion shows relaxation times similar to articular cartilage in cartilage mapping, suggesting a chondral matrix inside (Figure 6).
Osteoid osteomas (OO) are non-malignant bone tumours, with a 3:1 male-to-female presentation ratio. Usually, the diagnosis is made in the age range of 5 to 25 years [1–3].
OO represents 19.4% of all non-malignant bone tumours, with the talus being the fourth most commonly affected bone, occurring between 2% and 10% of cases [4]. These tumours rarely reach diameters greater than 1.5 cm [1,2].
The clinical presentation is local pain, most severe at night, swelling, and stiffness during daily activities, with temporary relief with non-steroidal anti-inflammatory drugs (NSAIDs). Local hypersensitivity and oedema are commonly observed because of the tumour hypervascularity and the consequent prostaglandins production [1–3].
OO are classified into 3 histological types: cortical, spongy, and subperiosteal. In long bones, OO tend to appear in cortical bone and cause an excessive subperiosteal reaction. In the short and flat bones of the foot, OO typically appears in spongy and subperiosteal location, without a significant subperiosteal reaction [3,4].
The misinterpretation of the initial symptoms often leads to a diagnostic delay, being the average time for the manifestation of these symptoms in the range of 1 to 2 years. This lapse of time between clinical presentation and diagnostic confirmation highlights the importance of a careful evaluation and the use of multiple imaging scans to achieve accurate identification of OO [1,2]. The typical nidus is seen in 62.2% of cases, which makes it difficult to diagnose and may require up to four scans in specialised centres for confirmation [1,2].
In this context, CT scan is superior to MRI scan, with MRI failing to make the diagnosis in 33% to 35% of the cases of suspected osteoid osteoma, therefore CT scan is the gold standard diagnostic method [1,2,4]. CT scans can identify a highly mineralised tumour focus, surrounded by a hyperdense sclerotic area up to 1 cm, while MRI shows bone marrow oedema and adjacent tissue lesions. Bone scintigraphy provides a metabolic evaluation of the lesion and may also be useful to differentiate it from other diseases [5].
MRI scans, as a non-invasive method, allow an early evaluation of cartilage changes, due to their ability to quantify structural modifications. T2 mapping is known to be sensitive to both the organisation of the collagen matrix and the water content of cartilage, increasing the signal when there is disorganisation of the collagen matrix. A cartilage mapping was performed on the patient, which showed T2 values consistent with normal cartilage [6].
Informed consent was obtained from the patient for publication.
Osteoid osteoma
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Based on the provided MRI and CT images, a small area of high-density sclerosis is observed in the right talus (ankle region), with a possible low-density lesion in the center (suspected “fissure” or “small cavity” appearance), along with a certain degree of bone marrow edema. A bone scan also indicates a localized hot spot (an area of increased metabolism) in the right ankle. MRI sequences reveal mild edema in the surrounding soft tissue, though no obvious soft tissue mass or malignant infiltration is noted. Overall, the images exhibit a typical pattern of sclerotic bone surrounding a small “cavity” (the so-called “nidus”) and some reactive bone changes, aligning with the characteristics of a benign bone tumor.
Integrating the chronic ankle pain during adolescence (worse at night, relieved by analgesics), imaging features (sclerotic band encircling a central small lucent focus on CT, localized hot spot on bone scan), and the classic clinical presentation of an osteoid osteoma, the most probable diagnosis is:
Osteoid Osteoma
Disclaimer: This report is based on the current imaging and patient history, and is for reference only. It cannot replace an in-person consultation or professional medical opinion. The specific treatment and rehabilitation plan should be determined by specialists in consideration of the patient’s individual condition.
Osteoid osteoma
