Musculoskeletal images. Acetabular tuberculous osteomyelitis.

vague complaints of right-sided knee pain. Conservative management was initiated without radiography. Two months later he was having difficulty with simple ambulation and began to experience rest and night pain. The location of the pain gradually moved proximally during this period and settled in the region of the right buttock. The patient had no relevant medical history. However, he had lost 7 kg over the preceding 4 months and had experienced several months of night sweats. He had immigrated to Canada from the Philippines 5 years before, and he was working in a restaurant. On physical examination, his body temperature was normal. He had an obvious antalgic gait. Range of motion of the right hip was slightly decreased and painful on internal rotation, but no other abnormality was noted. On plain radiography of the pelvis and right hip (Fig. 1), a large lytic lesion was identified in the posterior column of the right acetabulum, with extension into the ischium. Differential diagnoses included giant cell tumour, chondroblastoma, osteoblastoma, eosinophilic granuloma, infection or a synovial-based process such as pigmented villonodular synovitis. Magnetic resonance imaging (Fig. 2) demonstrated a multicystic, multilobulated, peripherally enhancing lesion centred on the right acetabulum, with soft-tissue extension into the internal obturator muscle and the pelvic cavity, as well as within the posteromedial muscles of the proximal right thigh. Given these imaging characteristics, the most likely diagnosis was either an infecSurgical Images Imagier chirurgical