A 17-year-old male with a history of sickle cell disease presents with hip pain after lifting weights.
17岁男性，有镰状细胞病病史，负重后髋关节疼痛。
Findings and Diagnosis
- Osteonecrosis of the femoral head 股骨头坏死
- Osteomyelitis 骨髓炎
- Femoral neck fracture 股骨颈骨折
- Legg-Calve-Perthes disease 股骨头骨骺
Discussion
Avascular necrosis (AVN), or osteonecrosis, of the femoral head is a potential complication of sickle cell anemia.1,2
股骨头缺血坏死（AVN）是镰状细胞病的潜在并发症之一。
Sickle cell anemia is an autosomal recessive condition in which an HBB gene mutation produces an abnormal version of beta-globin, hemoglobin S (HbS), which polymerizes and weakens red blood cells.1, 3 These red blood cells are prone to structural instability, reduced flexibility, and increased susceptibility to oxidative stress, leading to vaso-occlusive processes, ischemia-reperfusion injury, and hemolytic anemia.1,3 Sickle cell anemia is prominent in African and Mediterranean populations and may be protective against Plasmodium falciparum malaria.1
镰状细胞病是一种常染色体隐性异常，由于HBB基因突变可生成异常的β球蛋白和血红蛋白S，聚合并消弱红细胞，使红细胞结构不稳定、弹性降低、氧分压增高，引起血管阻塞、缺血-再灌注损伤、溶血性贫血。镰状细胞贫血多发生于非洲和地中海人群，可预防疟疾。
Together, vaso-occlusion, stasis, and ischemia promote ongoing sickling of red blood cells and contribute to AVN of the femoral head. This condition may develop in nearly half of all patients with sickle cell anemia by age 35 with potential bilateral joint involvement.3
血管阻塞、血液凝滞、局部缺血共同促进了镰状细胞的生成，导致股骨头缺血性坏死。35岁以上的镰状细胞病患者中，有超过一半的人患有股骨头坏死，且可能累及双侧股骨头。
Clinical Presentation
Radiographic image features
AVN in sickle cell anemia typically occurs in the medullary cavity and epiphysis.3 Over time, radiography may demonstrate the following sequence: ill-defined radiolucency followed by “arc-like” subchondral and intramedullary zones that have patchy areas of lucency and sclerosis.3 There may also be sclerosis in the peripheral rim of medullary bones.3
镰状细胞贫血并发AVN通常发生于骨髓腔和骨骺。随着病情的发展，影像学可出现以下一系列改变：不规则透光区，随后发展为软骨下弧形改变，骨髓内斑片状透光区和硬化区。髓质骨周边有时可见环形硬化。
Specifically in AVN of the femoral head, initial radiographs may be negative even in the presence of clinical symptoms.3 Radiographic imaging may reveal mottled attenuation of the epiphysis, subchondral lucencies, and the key finding of flattening of the articular surface.3 Joint space narrowing, articular sclerosis, osteophytosis, secondary degenerative changes, and the dreaded complication of joint collapse may subsequently be visible as well.3,4
即使有临床症状，早期的股骨头坏死X线也可以表现为阴性。AVN的X线可表现为骨骺区的斑片状低密度、软骨下透光区、股骨头变平。有时可见关节间隙狭窄、关节硬化、骨质增生、继发退行性变，甚至关节塌陷。