Chinese Expert Consensus on Ultrasonographic Acquisition, Measurement, and Reporting System for Developmental Dysplasia of the Hip

a Department of Ultrasound, The Shenzhen Children’s Hospital, China; b Department of Orthopedics, The Shenzhen Children’s Hospital, China; c Department of Ultrasound, The Qilu Children’s Hospital of Shandong University, China; d Department of Ultrasound, The Hunan Children’s Hospital, China; e Department of Ultrasound, The Henan Children’s Hospital, China; f Department of Ultrasound, The Kunming Children’s Hospital, China; g Department of Ultrasound, The Shanxi Children’s Hospital, China; h Department of Ultrasound, The Guizhou Women and Children’s Hospital, China; i Department of Ultrasound, The Wuhan Women's and Children's Health Care Center (Wuhan Children’s Hospital), China; j Shandong Medical Imaging Research Institute, China Received December 16, 2019; revision received January 07, 2020; accepted January 14, 2020.


Purpose
Developmental dysplasia of the hip (DDH) is one of the most common skeletal dysplasias in infants. There are significant differences in incidence among different ethnic and regions, ranging from 0.15‰ to 2‰ [1], with etiology related to congenital hereditary factors and postnatal factors [2]. Early diagnosis and treatment during childhood can prevent DDH from developing and result in completely normal hip joint structure and function in affected children. Delayed diagnosis and treatment can lead to different degrees of joint deformity, even disability. DDH is currently the most common cause of hip replacement in patients under 60 years of age. A large number of late-diagnosis cases [3] not only bring various difficulties to the treatment, but also cause great difficulties to the preservation of hip function after treatment. Therefore, the early diagnosis and treatment of DDH is very important.

Source and Selection Criteria
Publications from January 2000 to January 2019 were searched through PubMed, and a combination of the following medical subject headings (MeSH) were used for the searches: (dysplasia of the hip) AND (ultrasound or ultrasonography or hyperacoustic or ultrasonic). References were validated and articles with high impact factors were selected first. The search identified many research reports on DDH [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] and evidence-based guidelines and paper on DDH ultrasound in North America and Europe [22][23][24][25][26]. Considering that incidence, examination methods, and diagnostic criteria for DDH may be influenced by race, region, age, habits, and that differences in health care systems, we determined that it is necessary to unify the Chinese methods of DDH ultrasound examination and establish a uniform set of methods. This set of methods could be applied to different regions, different medical center, used for the screening, inspection and re-examination of hip joint, and to provide the basis for how to prevent, diagnose and treat DDH research.

Preparation
In ). Subsequently, many DDH multi-center satellite conferences were held. The cooperative units combined to examine the relevant international and Chinese consensus guidelines, and, after repeated discussions, formed this expert consensus. This consensus document will continue to be improved according to feedback in the future. It uses the following grading system for the level of evidence for each recommendation (Table 1). G Not recommended or as a regular recommendation. It is impossible to evaluate the pros and cons of the lack of evidence, lack of evidence, or conflicting results.

Indications/Contraindications and Timing
Ultrasound can be used to monitor DDH screening, diagnosis, and treatment. Indications of ultrasonography include the following [ Due to the presence of physiologic laxity, hip sonography is not performed on patients younger than 2 weeks of age unless clinical findings indicate dislocation or significant instability. For children over 6 months old, the study becomes less reliable compared to radiography because ossification of the femoral head progresses, and ultrasound examination can be selected according to clinical requirements.
Recommendations: Follow the guidelines from the ACR Appropriateness Criteria® on Developmental Dysplasia of the Hip-Child [27], and the American Academy of Orthopedic Surgeons Evidence-Based Guideline on Detection and Nonoperative Management of Pediatric Developmental Dysplasia of the Hip in Infants up to Six Months of Age [28]. Recommended level: A.

Equipment
Hip ultrasound for detecting DDH should be performed with a higher frequency linear probe and depth to meet the necessary penetration. The instrument may have preconditions for DDH ultrasonic examination. Total ultrasound exposure should be kept as low as reasonably achievable while optimizing diagnostic information.
The examination bed is a commonly used as the diagnostic bed.

Qualifications and Responsibilities of Personnel
1. Master the basic knowledge and skills of DDH ultrasonic examination.
1.2 Take the measurements with hip ultrasound mainly include alpha angle, femoral head coverage, femoral head size, pubis-femoral distance, ischiumfemoral distance, and femoral-pubis distance.
1.3 Master the manipulation and criteria of the hip stability test (body axial, adduction and abduction).
2. For hospitals that have not yet carried out DDH ultrasound examination, the physicians need to receive standardized hospital training on the operation and diagnostic capacity for DDH ultrasound.
2.1 Operational training: under the guidance of professional DDH ultrasound doctors, trainees should complete 50 cases of DDH ultrasonography and including more than 10% abnormal cases.
2.2 Diagnostic ability training: under the guidance of professional DDH ultrasound doctors, trainees should independently diagnose 50 cases of DDH. The coincidence rate of the main diagnosis should be more than 90% and including more than 10% abnormal cases.

The body position
It is acceptable to perform the examination with the infant in a supine or a lateral decubitus position. Morphology is assessed at rest or with the lower extremities relaxed.
Neutral position: The hip is neutral and the knee is at shoulder width on the same side ( Fig. 2A, 2B).
Flexion position: The hip flexion is 90° and the knee is at shoulder-width on the same side (Fig. 2C, 2D).
The doctor is located on the right side of the patient, and the parents are located on the left side of the patient to assist the child into position and to comfort the child so that the child can keep as quiet and relaxed as possible.
Recommendations: Follow the guidelines of the AIUM-ACR-SPR-SRU practice parameter for the performance of an ultrasound examination for detection and assessment of developmental dysplasia of the hip [24]. Recommended level: A.

Specifications of the Examination
Bilateral hips should be examined. The purpose of DDH ultrasound is to evaluate hip stability, the femoral head position and the acetabular morphology. Referring to the clinical practice guidelines from the American Institute of Ultrasound in Medicine (AIUM), the American College of Radiology (ACR), the Society for Pediatric Radiology (SPR), and the Society of Radiologists in Ultrasound (SRU) [22][23][24][25], this standard is formulated jointly according to the relevant guidelines at home and abroad and the experience of multi-center research in China [29].
All the children were examined in two standard positions neutral and flexion hip position, and image storing and quantitative analysis. Four static diagrams and four (loop) dynamic diagrams are required for each hip sides (Fig. 2). The recommendations for specifications of the operation are shown in Table 2.

Specifications of the Measurement
The following measurements were performed on a standardized hip section (Fig. 3): alpha angle, femoral head coverage (FHC), femoral head size, pubo-femoral distance, ischium-femoral distance, and femoral-pubo distance.
In order to improve the accuracy of measurement, all data are measured on the machine. 1. α angle measurement: As shown in Figure 3A, this angle should be measured in neutral position or flexion position with coronal section imaging.
2. β angle measurement: As shown in Figure 3B, this angle should be measured in neutral position with coronal section imaging.
3. FHC measurement: As shown in Figure 3C, this parameter should be measured in neutral position or flexion position with coronal section imaging.
4. Femoral head size measurement: As shown in Figure 3D, this parameter should be measured in neutral position with coronal section imaging.
5. PFD and IFD measurements: As shown in Figure  3E, this parameter should be measured in neutral position with transverse section imaging. 6. FPD measurement: As shown in Figure 3F, this parameter should be measured in flexion position with transverse section imaging.
4. Femoral head measurement refers to the "Developmental dislocation of the hip in infants: the hip's ultrasound quantitative analysis" study [33]. Recommended level: B.
5. PFD and IFD measurements refer to "Ultrasonic measurement and analysis of hip in healthy infants: a multicenter study" [29]. Recommended level: B.

Report
The acetabular morphology, the femoral head position, the hip stability, and the quantitative analysis results should be described in the report. The ultrasound examination and its interpretation should be available as a permanent record, including all abnormal and normal images. The application of DDH ultrasonography includes Graf 's method, Hacker 's method, and Terjesen's method, among others. The examinations and measurement programs mentioned above can be selected according to clinical needs to develop a clinical diagnosis and follow-up the hip treatment.
To observe the development of hip joint, it is suggested that all infants less than 6 months old should be followed up. Follow-up is important for establishing a mechanism to avoid missing any abnormal hip development and prevent dislocation in the early stages of life.

Limitation and Potential Developments
We need a large study population before and after treatment to meet the clinical needs. And this consensus helps to identify patients with mild hip disease who do not need surgery. So as to improve the basis of early treatment for such patients.