1. Introduction Acetabular impingement is a condition in which the head of the femur breaks through the inner wall of the acetabulum and exceeds the iliac line. Primary acetabular invagination is rare and the etiology is not completely clear, while secondary acetabular invagination is mostly secondary to infection, inflammation and post-trauma [1]. For adult patients with osteoarthritic changes, artificial total hip replacement is often used, at present, there are still many controversies at home and abroad on the acetabular reconstruction of acetabular socket, our department uses artificial total hip replacement and bone grafting to rebuild the acetabulum, to restore the femur of the affected hip eccentricity and the center of rotation of the acetabulum. 2, Clinical data and methods 2.1 General data From January 2006 to February 2010, our department admitted 12 cases of acetabular socket in 12 hips, 5 male and 7 female; age 39 to 72 years old, average 61.5 years old: duration of the disease 1.5-25 years, average 7.8 years. Among them, there were 3 cases of mild invagination, 7 cases of moderate invagination, 2 cases of severe invagination, 3 cases of primary and 9 cases of secondary factors: 5 cases of rheumatoid arthritis, 2 cases of ankylosing spondylitis and 2 cases of trauma. 2.2 Surgical methods 2.2.1 Preoperative preparation After the patients were admitted to the hospital, all of them were photographed with the pubic symphysis as the center of the pelvic orthopantomogram and enlarged according to 1:1.15, and were measured with a prosthesis template to roughly determine the size of the prosthesis before the operation. The distance between the inner wall of the acetabulum and Kohler’s line was measured and graded according to Charnley’s diagnostic criteria: 2nd degree: (moderate internal 3rd degree: (severe invagination) more than 15 mm.In our case, there were 3 cases of mild invagination, 7 cases of moderate invagination and 2 cases of severe invagination. And the bilateral femoral eccentricity (the vertical distance between the center of rotation of the femoral head and the longitudinal axis of the femoral stem) and the center of rotation of the acetabulum were measured and marked on the X-ray film. For patients with secondary acetabular invagination, the preoperative relevant examinations were perfected, and the surgical plan was determined after actively treating the primary disease until the symptoms were relieved. 2.2.2 Surgical methods: adopt hard lumbar anesthesia or general anesthesia with tracheal intubation, patients take the healthy side lying position, axillary pads are empty, after routine disinfection and laying of towels, make a 12-15cm long incision for the posterior lateral approach of the affected hip, incise the skin, subcutaneous, and broad fascial tensor muscles, peel off the externally rotated muscle group and joint capsule, fully expose the operation field, make a bone cut on the lesser rotor at 0.5-1.0cm, take out the head of the femur, clean up the bone cumbersome and soft tissues around the acetabulum, and polish the acetabulum. The acetabulum was cleaned of the bony and soft tissues around the acetabulum, and the acetabulum was polished. During the operation, the degree of acetabular socket was assessed again, and for mild socket, autologous bone grafting was performed, while for moderate to severe acetabular socket, the femoral head was removed to remove the cartilage surface and the cancellous bone was implanted into the socket to restore the center of acetabular rotation of the affected hip, and then according to the size of the specimen, the appropriate type of acetabular cup and polyethylene liner were inserted and screwed in for fixation. Then flex and internally rotate the affected hip joint, expand the medulla through the osteotomy, insert the biologic or cemented femoral stem prosthesis according to the size of the trial mold of the prosthesis stem, install the ball head, reset the affected hip joint, and restore the cervical stem angle of the affected hip and the eccentricity of the femur. After checking that the position of the prosthesis is satisfactory, flush and close the wound, and transfuse blood appropriately according to the amount of intraoperative bleeding. 2.2.3 Postoperative rehabilitation and follow-up After operation, antibiotics are used for 3-5 days to prevent infection, and conventional anticoagulation is used for 7-10 days to prevent deep vein thrombosis depending on the bleeding condition of the wound in the first to second day after operation, and partially weight-bearing walking of the affected limb assisted by a walker is begun in 1 week after operation, and fully weight-bearing walking is begun in 2-3 months, and excessive flexion/extension, inward retraction and internal rotation of the affected hip is avoided. The orthopantomograms of the pelvis were reviewed at 1, 2, 3, 6, 9, 12 months after the operation and once a year thereafter, to assess whether the acetabulum and femoral stem prosthesis had loosened or displaced, and whether the acetabulum had fallen in again. Harris Hip Score was used to assess the hip function and compared with the preoperative period. 3, Results The incision of 12 patients in this group healed in stage I after surgery, and the patients were given follow-up from 12 months to 62 months, with an average of 37 months. Preoperative Harris hip score averaged (49.5+5.5) points, and Harris hip score averaged (90.5+4.5) points at the last follow-up, with an average improvement of 41 points from the preoperative period. Repeat X-rays showed that the prostheses were all in good position, with no loosening or displacement, and the grafted bone was fused to the acetabulum, with no re-indentation of the acetabulum. During the follow-up period, all the patients had satisfactory results, the clinical symptoms were completely relieved, all of them gained the ability of daily life, and none of them had loosening and displacement of the prosthesis. 4.Discussion Acetabular invagination is a disease in which the femoral head invagination breaks through the inner wall of the acetabulum and exceeds the Kohler’s line (the line between the medial border of the sciatic bone and the medial border of the ilium bone), which causes joint pain and activity limitation. It was first proposed by the German pathologist Otto [2] in 1824, and began to be widely recognized all over the world at the end of the 19th century. According to the etiology, it can be divided into two categories: primary and secondary, for primary acetabular subsidence the etiology of the disease is still not completely clear [1,2], and for secondary acetabular subsidence, which is mostly secondary to infections, inflammation, and traumatic injuries, the patient’s acetabulum is inwardly and upwardly invaginated, and it is often manifested as hip pain and Hip joint mobility is reduced. Surgery is the main treatment for acetabular socket (for secondary acetabular socket, the secondary factors should be clarified and pre-treated first). The commonly used surgical procedures include: arthroplasty, total hip arthroplasty, acetabuloplasty, intertrochanteric osteotomy, cartilage fusion, etc. The choice of surgical procedures for patients with acetabular socket indentation is based on the age of the patient, the maturity of the bone development, as well as the extent and degree of degenerative changes in the joint [4,5].