Developmental dysplasia of the hip (DDH) describes a broad spectrum of developmental abnormalities of the hip joint that are traditionally diagnosed during infancy. Because the development of the hip joint is a dynamic process, optimal treatment depends not only on the severity of the dysplasia, but also on the age of the child. Various imaging modalities are routinely used to confirm suspected diagnosis, to assess severity, and to monitor treatment response. For infants younger than 4 months, screening hip ultrasound (US) is recommended only for those with risk factors, equivocal or positive exam findings, whereas for infants older than 4-6 months, pelvis radiography is preferred. Following surgical hip reduction, magnetic resonance (MR) imaging is preferred over computed tomography (CT) because MR can not only confirm concentric hip joint reduction, but also identify the presence of soft-tissue barriers to reduction and any unexpected postoperative complications. The routine use of contrast-enhanced MR remains controversial because of the relative paucity of well-powered and validated literature. The main objectives of this article are to review the normal and abnormal developmental anatomy of the hip joint, to discuss the rationale behind the current recommendations on the most appropriate selection of imaging modalities for screening and diagnosis, and to review routine and uncommon findings that can be identified on post-reduction MR, using an evidence-based approach. A basic understanding of the physiology and the pathophysiology can help ensure the selection of optimal imaging modality and reduce equivocal diagnoses that can lead to unnecessary treatment.

中文翻译：

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髋部发育异常的成像：超声，放射线照相和磁共振成像。

髋关节发育不良（DDH）描述了广泛的髋关节发育异常，这些异常通常在婴儿期就被诊断出来。由于髋关节的发育是一个动态过程，因此最佳治疗不仅取决于发育不良的严重程度，还取决于孩子的年龄。常规地使用各种成像方式来确认可疑诊断，评估严重性和监测治疗反应。对于4个月以下的婴儿，仅建议对那些具有危险因素，检查结果含糊或阳性的婴儿进行超声筛查（US），而对于4-6个月以上的婴儿，则首选骨盆造影。手术减少髋关节后，磁共振（MR）成像比计算机断层扫描（CT）更可取，因为MR不仅可以确认同心髋关节复位，还可以识别出软组织复位障碍以及术后意外并发症。由于功能强大且经过验证的文献相对较少，因此常规使用造影剂增强型MR仍存在争议。本文的主要目的是检查髋关节的正常和异常发育解剖，讨论关于成像方式最适当的选择，目前的建议背后的基本原理为筛查和诊断，并审查程序和罕见的发现，即可以使用基于证据的方法对减少后的MR进行识别。