Developmental hip dysplasia, formerly known as congenital dislocation of the hip (CDH), is a general term for a group of pathologies characterized by spatial and temporal instability of the hip joint during development, including hip dislocation, subluxation, and acetabular dysplasia. DDH can cause abnormal gait, abnormal development of adjacent joints, and secondary deformities of the spine, leading to lower back pain and pain due to degenerative hip joint degeneration in adulthood. Because the disease is closely related to the developmental process of the hip joint, the presentation and corresponding treatment varies among age groups. The goal of DDH treatment is to obtain a stable concentric reposition and avoid ischemic necrosis (AVN) of the femoral head. Early diagnosis and treatment are the keys to improve the outcome. I. Birth to 6 months This stage is the prime time for DDH treatment, with simple and easy methods, good compliance, reliable efficacy and few complications. 1. Clinical manifestations and signs: asymmetry of thigh skin pattern and hip pattern, joint popping and unequal length of lower limbs. Positive hip abduction test on the dislocated side. Ortolani/Balow sign is positive. Inequality of limbs, positive Allis (Galleazzi) sign, etc. 2. Imaging: Ultrasound examination of the hip joint is preferred for children ≤4 months old, Graf method; X-ray double hip orthopantomographs can be taken for children >4 months old, commonly used indicators are Perkin’s square, acetabular index (AL), central marginal angle (CEA), Shenton’s line, tear drop (Teradrop) sign. 3, Treatment: Pavlik sling is preferred to maintain hip flexion at 100°~110° and abduction at 20°~50°. 24 hours maintenance. Prohibit dislocation movements (including examination and changing clothes). Regular ultrasound examinations, 1 time/1 to 2 weeks. If ultrasound indicates a concentric reposition after 3 weeks, continue to maintain for 2 to 4 months. An abduction brace was then used until the acetabular index (AL) was <25° and the central marginal angle (cea) was >20°. If ultrasound and clinical examination after 3 weeks suggest that no repositioning has been achieved, the Pavik sling is discontinued and other treatment is used instead. Otherwise, persistent compression of the acetabular wall by the posteriorly dislocated femoral head can lead to sling disease (dysplasia of the posterior acetabular wall). Other treatment methods include brace (fixed position as sling) or direct closed cast fixation, avoid repositioning under non-anesthesia, wearing extreme (frog) abduction brace to avoid damage to femoral head cartilage and AVN. 2. 7 months～18 months The compliance and efficacy of using sling decreases with the increase of age, weight and activity. 1. Clinical manifestations and signs: In addition to the above-mentioned manifestations, physical examination reveals asymmetric appearance of both hips, wide perineum, high greater trochanter, positive telescope sign (telescope sign) and Allis sign. 2. Treatment: Closed repositioning under anesthesia and plaster tube fixation in human position are preferred. Before closed repositioning, the internal longus muscle should be cut or cut percutaneously, and if necessary, the iliopsoas tendon should be cut at the same time, and repositioned by gentle Ortolani technique. The observation index is a safe zone >20°. Arthrography with Onyepek is recommended. If the imaging shows a gap of >4 mm between the cartilage margin of the femoral head and the inner wall of the acetabulum, it suggests soft tissue impaction between the head and socket, which prevents the reset. Abandon closed reduction and use transmedial approach (Ludolff, Ferguson) or anterolateral approach (Bikini, S-P) for incisional reduction instead. Preoperative skin traction is possible for 1-2 weeks, or for several weeks to achieve repositioning. After repositioning, the hip is fixed in a human plaster cast in 100° of flexion, 40-50° of abduction, and neutral rotation for 3 months, and then the cast is replaced and continued in a plaster cast or brace for 3-6 months. At the end of the above treatment, the child has the following conditions: ① concentric cephalo-acetabular repositioning, observation; films are taken every 6 months; ② cephalo-acetabular repositioning, but residual acetabular dysplasia, manifested by steep and straight acetabulum, AI>24°, but continuous Shenton line, wearing an abduction brace, especially at night; films are taken every 4 months to observe the improvement of acetabular inclusion (AI, CEA), or whether there is semi (3) Residual subluxation, which is manifested by discontinuity of the Shenton’s line, is usually associated with acetabular dysplasia. An abduction brace may be worn and the patient should be reviewed every 3 months for a total of 6 to 12 months. If the radiographs show persistent subluxation (Shenton’s line discontinuity), surgical correction should be performed; if it continues to improve, the treatment should be the same as ②; ④ For residual AVN, the affected femoral head should be placed under the inclusion of the acetabulum to allow for repair and shaping. The specific treatment is the same as ② and ③. Clinical manifestations and signs: limp, duck walk, unequal lower limbs, increased lumbar lordosis, limited hip abduction, positive Allis sign, positive Trendelenburg sign, etc. 2.Imaging: X-ray double hip orthopantomographs, assessment indexes are the same as before. CT 3D reconstruction is an effective means to observe the anterior femoral tilt angle and posterior dislocation. 3.Treatment: It is still possible to try closed repositioning within 2 years of age, but most children need incisional repositioning and osteotomy. Osteotomy of the pelvis and proximal femur not only corrects the deformity of the acetabulum and proximal femur itself, but also provides stability after reset. Currently, there is a common international phase I surgical treatment; incisional repositioning, pelvic osteotomy, and proximal femoral osteotomy. Preoperative traction is not required. (1) Incisional repositioning: anterolateral S-P or Bikini approach. The main points are: full exposure, release, T-shaped incision of the joint capsule, removal of the acetabular contents (round ligament, transverse menhaden ligament, avoid removing the menhaden lip), return of the femoral head into the true acetabulum to achieve concentric repositioning, and V-shaped capsule tightening and molding. (2) Selection of pelvic osteotomy: Any kind of pelvic osteotomy cannot treat DDH, and the basic preoperative requirement is that concentric repositioning has been achieved. Reconstructive pelvic osteotomy should be preferred, mainly: a change the acetabular direction: Salter, Triple (Triple) osteotomy; b change the acetabular form: for large acetabulum and relatively small femoral head, steep and straight acetabulum, true and false acetabular continuation, commonly used is Pemberton osteotomy, Dega osteotomy. (3) Proximal femur (inter-rotor and sub-rotor) shortening osteotomy is to reduce the inter-acetabular pressure and avoid AVN; rotational inversion osteotomy is to correct excessive anterior tilt angle and neck stem angle. Postoperatively, the hip was fixed in herringbone plaster for 6 weeks. In children over 5 years old, to prevent joint stiffness, plaster fixation was feasible for 3 weeks followed by bilateral lower extremity abduction skin traction for 3 weeks. X-ray examination was performed to confirm the healing of the osteotomy, the absence of AVN, and the resumption of walking. Review the development of the hip joint until bone maturity by annual radiographs. Clinical manifestations and signs: In addition to the above manifestations, attention should be paid to the presence or absence of fatigue pain and (in children with subluxation) joint movement end-extrusion pain. 2. imaging examination: X-ray double hip orthopantomographs, assessment indexes as before, and should pay attention to the presence or absence of osteoarthritic manifestations in the semi-dislocated joint. CT 3D reconstruction can also assess the morphological adaptation of the head socket in addition to observing the anterior tilt angle and posterior dislocation. 3. Treatment: recommendations exist. The aim of treatment for unilateral dislocation is to maximize anatomical and functional restoration and to create conditions for joint replacement. Equalization of lower limb length prevents secondary spinal deformities. The prognosis for surgical complications in bilateral dislocations without pseudosocket formation is inferior to the natural prognosis and treatment may be abandoned. Bilateral dislocation with pseudoacetabular formation is prone to early onset arthritis, and palliative treatment is feasible. The common procedures for palliative treatment (abandonment of repositioning) are internal pelvic displacement osteotomy (Chiari procedure), acetabular expansion (slot extension, Staheli), and Shanz osteotomy (subrotor abduction osteotomy). Surgical treatment of older DDH. The indications are not clear, the surgical operation is difficult, there are many surgical complications and the efficacy is uncertain, so it should be used with caution and with the participation of experienced and dedicated surgeons. V. Diagnosis and treatment of acetabular dysplasia can be seen in all age groups and can be primary or secondary (after closed/incisional repositioning). 1, clinical manifestations and signs: mostly asymptomatic, late stage may have hip fatigue or pain. There are few positive signs, but end-of-motion pain should be noted, suggesting a labral injury. 2, imaging: X-ray double hip orthopantomogram CEA>20°, cephalic socket coverage <80%. faux posture (pseudo-lateral) film, to understand the development of the acetabular anterior margin. ct three-dimensional reconstruction. 3. Treatment: Acetabular dysplasia has the potential to improve with development. If there are no imaging changes of early osteoarthritis and/or subluxation, close follow-up observation is possible. If there is no improvement and early osteoarthritic changes are present, external osteotomy should be performed. In case of subluxation (interruption of Shenton's line), additional orthopantomographies of both hips in abduction (≥20°) should be taken, and if central repositioning is possible, extracapsular osteotomy should be performed; if neutral repositioning is not possible, incisional repositioning with osteotomy should be performed.