病史23岁长跑运动员，胫骨前侧疼痛。（A 23-year-old long distance runner with pain in the anterior tibia.）影像学表现小腿正位(a)和侧位(b)X 线片显示胫骨前外侧较厚的骨膜反应（shows an area of thick periosteal reaction in the anterolateral tibial shaft），在骨膜反应区中部可见垂直于胫骨长轴的线状低密度灶（there is a linear lucency which is perpendicular to the long axis of the tibia）。MR抑脂 T2WI(c)显示线状缺损及其周围的水肿（demonstrates edema in and adjacent to the linear defect.）。鉴别诊断(前3位)
- 骨样骨瘤 Osteoid osteoma
- Brodie脓肿 Brodie’s abscess
- 应力性骨折 Stress facture
讨论骨膜反应和骨髓水肿可见于上述三种疾病中的任意一种（Periosteal reaction and marrow edema can be seen in any of the three entities listed above. ）。线性低密度骨折线（The linear lucent fracture line）是最有用的鉴别点，这是因为骨样骨瘤的瘤巢或Brodie骨脓肿的病灶在大多数病例中都是圆形的（the nidus in an osteoid osteoma or Brodie’s abscess is round in most cases），但线性瘘道（a linear cloaca）也可见于 Brodie脓肿。基于病史，应力性骨折是这三个鉴别诊断中最可能的诊断，此病例还应考虑骨肉瘤和 Ewing肉瘤（Additional considerations in this case would include osteosarcoma and Ewing sarcoma;），但这两种肿瘤通常有更具侵袭性表现并可见软组织肿块（have a more aggressive appearance and can have a soft tissue component）。最后，和其他疾病相比，应力性骨折在随访检查中可出现愈合的表现（show healing on subsequent exams）。
诊断
- 应力性骨折Stress facture
要点
- 应力性骨折是一种过劳性损伤，可发生于异常或反复应力作用于正常骨(疲劳骨折)或正常应力作用于异常薄弱骨(不全骨折)的情况下。Stress fractures are overuse injuries that occur in the setting of unusual or repeated stress to normal bone (fatigue fracture) or normal stress to abnormally weakened bone (insufficiency fracture).
- 应力性骨折最常见的部位是股骨颈、跖骨、跗骨和胫骨（后内侧或前外侧)。The most common sites for stress fractures are in the femoral neck, metatarsals, tarsals, and tibia (posterior medial or anterolateral aspect).
- 发生机制部分是由于骨对拉力/张力反应较差，而不是对压力的反应差。Mechanism is partly due to poor response of the bone to tensile instead of compressive forces.
- 应力性骨折的表现取决于其愈合的不同阶段，早期X线片上往往不可见。The appearance of a stress fracture depends on the stage of healing and is often not visible on early radiographs.
- MRI和骨扫描比X线片能更早的检测到应力性骨折和应力反应。MRI and bone scan can help detect stress fractures and stress response earlier than radiographs.
- 透亮的骨折线常垂直于骨皮质。The lucent fracture line is often perpendicular to the cortex.