Stäbler A, Beck R, Bartl R, Schmidt D, Reiser M
Institute of Diagnostic Radiology, Klinikum Grosshadern, Ludwig Maximilian University, Munich, Germany.
Skeletal Radiol. 1995 Jan;24(1):31-5. doi: 10.1007/BF02425944.
Insufficiency fractures of the sacrum are found in women who have undergone radiation therapy to the lower abdomen as well as those suffering from osteoporosis of postmenopausal, steroid-induced, or primary biliary cirrhosis-related origin. Increased uptake in bone scintigraphy and osteolytic changes in these fractures can be misinterpreted as bone metastases, leading to unnecessary biopsies and other procedures in the ensuing search for non-existent primary tumor.
In eight female patients averaging 69.4 years of age, insufficiency fracture of the sacrum was diagnosed by computed tomography (CT) and bone scintigraphy. Three underwent a total of five MRI examinations. Malignancy was excluded by histology in two patients and follow-up of at least 6 months in the remainder. Retrospective analysis of CT scans of 13 patients with metastases in the sacrum revealed no vacuum phenomena.
In seven of eight patients with insufficiency fracture of the sacrum, vacuum phenomena were shown on CT examination. The gas was localized centrally within the ventral part of the fracture in three patients; gas was located in ten adjacent sacro-iliac joints of six patients.
The vacuum phenomenon may be an incidental finding in osteoarthritis of the sacro-iliac joint, but it has not been previously recognized in IFS. The presence of intra-articular vacuum phenomena in the sacro-iliac joints in combination with a sacral fracture and vacuum phenomena located within the sacral fracture supports a diagnosis of insufficiency fracture or may indeed be the clue by which this diagnosis is established.
骶骨不全骨折见于接受下腹部放射治疗的女性以及患有绝经后、类固醇诱导或原发性胆汁性肝硬化相关骨质疏松症的女性。骨闪烁显像中摄取增加以及这些骨折中的溶骨性改变可能被误诊为骨转移，从而导致在随后寻找不存在的原发性肿瘤时进行不必要的活检和其他检查。
8名平均年龄69.4岁的女性患者，通过计算机断层扫描（CT）和骨闪烁显像诊断为骶骨不全骨折。3名患者共接受了5次磁共振成像（MRI）检查。2名患者通过组织学排除了恶性肿瘤，其余患者进行了至少6个月的随访。对13例骶骨转移患者的CT扫描进行回顾性分析，未发现真空现象。
8例骶骨不全骨折患者中有7例在CT检查中显示真空现象。3例患者气体集中位于骨折腹侧部分中央；6例患者的10个相邻骶髂关节中有气体。
真空现象可能是骶髂关节骨关节炎的偶然发现，但此前在骶骨不全骨折中尚未被认识到。骶髂关节内关节内真空现象与骶骨骨折以及骶骨骨折内的真空现象同时存在支持骶骨不全骨折的诊断，或者实际上可能是确立该诊断的线索。
