Atypical Osteoid Osteoma of Proximal Femur and its Surgical Challenges: A Technical Note on ‘Wandering Nidus’ and Double Lesion

Abstract

Introduction: Osteoid osteomas are painful benign bone tumors, accounting for 10% of overall primary bone tumors. Typical osteoid osteomas are located intracortical or intramedullary in the metadiaphyseal region of the long bones. The Atypical ones are the Juxta and Intraarticular type, posing greater challenges in its diagnosis and management. CT and MRI scans have better chances of defining the nidus lesions in Atypical osteoid osteoma of the hip joints. Surgical treatment options include, image guided percutaneous interventions such as Radio frequency ablation, Laser or Cryo ablation. These modalities achieve surgical cure, but lacks the opportunity for a histo-pathological confirmation. Our cases will highlight the ‘wandering nidus’ in hip osteoid osteoma and the possibility of dual pathology (Osteoid osteoma and Osteomyelitis) in the same hip. Case study: We present two cases of hip joint osteoid osteomas (aged 18 yrs and 10 yrs) to highlight the diagnostic challenges and to discuss the different methodology of treatment. CT scan with additional MRI studies confirmed the radiological diagnosis after a delay of 6-8 months. The first case will highlight the wandering nature of the nidus (explained by the position of the calcific spicule within the nidus with reference to the needle tip), the challenges for needle trajectory with close proximity to femoral vessels and the “coaxial technique using chopstick maneuver” for CT guided needle excision. The second case will highlight the feasibility of percutaneous excision and surgical curettage in the presence of dual pathology. Conclusion: Both the cases were successfully treated by CT guided n excision biopsy and had the histopathological confirmation. Needle technique allows confirmation of diagnosis and exclusion of other differential pathology. Keywords: Wandering nidus, Atypical osteoid osteoma hip, Chopstick maneuver, Coaxial technique, Double hip lesion.