Serial Changes in Image Findings of Herniation Pits from the First Appearance

BACKGROUD: Herniation pits (HPs) have been considered to be an incidental finding, but recently femoroacetabular impingement (FAI) has been proposed as a possible cause of their formation. The findings on bone scans of HPs are variable in the literature: some showed increased uptake; the majority did not. We hypothesized that serial changes in image findings of HPs would explain the reason for the variable bone scan findings. METHODS: Four patients (5 hips) were followed up for more than 7 years. All patients were women and regularly underwent bone scintigraphy after the diagnosis of breast cancer. Small lesions with increased uptake were first detected on bone scintigraphy at the age of 44 to 64 years. In all cases, the lesions were confirmed by magnetic resonance imaging and follow-up bone scintigrams were taken regularly. Four lesions were also evaluated by computed tomography. Changes in the size of the pits and the intensity of the increased uptake on bone scintigraphy were evaluated. RESULTS: On the bone scintigrams, the lesions with increased uptake were detected in the femoral neck at 5–20 months after previous negative bone scintigraphy. There had been no events or symptoms associated with the newly detected increased uptake. On follow-up scans, the intensity of the uptake decreased gradually and the areas of increased uptake disappeared completely at 14–50 months after their first appearance. In 3 cases (2 patients), the pit size increased during follow-up. CONCLUSIONS: The areas of increased uptake on bone scintigraphy gradually disappeared in all cases and the increase in pit size was frequent. There was no case in which signs or symptoms suggestive of FAI were noticed.