Diaphyseal intramedullary osteoid osteoma: an enigmatic subtype

This retrospective study aimed to evaluate patients with similar clinical and radiological features of diaphyseal intramedullary osteoid osteoma, an enigmatic location subtype. Sixteen patients (11 males and 5 females) with an average age of 12.3 years at the time of presentation were reviewed. The lesion was located in the tibia unilaterally in 10 patients, bilaterally in three, and in the femur unilaterally in three. Diagnosis was established based on the typical clinical presentation of OO and the identification of nidus on computed tomography (CT) scan and magnetic resonance imaging (MRI), and confirmed by histopathological examination of tissues obtained during surgery. All patients underwent en bloc excision of the intramedullary abnormal bone, including the nidus, through a small cortical window. The typical pain of OO was the main complaint in all patients and was completely relieved by the second day after surgery. Out of the 16 histopathologically confirmed lesions, 15 showed a visible nidus on CT scan and MRI. After a mean follow-up period of 40.1 months (range 26 - 73 months), most patients were enthused about surgery and resumed their daily activities without pain or any limitation of movement. Only one patient experienced a traumatic tibial fracture at the operative site 3 months after surgery and healed spontaneously after 6 weeks of immobilization. Diaphyseal intramedullary osteoid osteoma should be considered when the typical clinical picture is present, regardless of whether the nidus is detected radiologically.