Acetabular fractures due to high-energy injuries are a current research hotspot in the field of orthopedics, and the treatment of acetabular fractures has evolved rapidly over the past 30 years, with a substantial decrease in mortality. To obtain good long-term clinical results, anatomic reduction of acetabular fractures is the basis, and the rate of functional excellence is significantly higher in anatomically reduced patients than in non-anatomically reduced patients. For complex acetabular fractures, it is the current medical consensus that incisional reduction and internal fixation is the first choice for surgical treatment. At present, the treatment of acetabular fractures mostly follows the two-column theory proposed by Letournel, in which the hip bone consists of the ilium, situs, and pubis, and the acetabulum seems to be located in an arch that includes 2 arms, called the anterior column (ilio-pubic column) and the posterior column (ilio-situs column) of the acetabulum, respectively. Letournel modified it by classifying acetabular fractures into 5 single fractures and 5 joint fractures. Of these, the five joint fractures include combined posterior wall and posterior column fractures, combined transverse and posterior wall fractures, T-shaped fractures, combined anterior and posterior column semi-transverse fractures, and bicolumnar fractures. The quadrilateral area behind the acetabular fossa formed by the internal rotation of the sciatic bone is called the quadrilateral body (or quadrilateral area), and the anterior and posterior columns intersect at 60° to form an arch-shaped structure called the acetabular roof, which is the main weight-bearing area of the acetabulum, and the upper part of the quadrilateral body is involved in the composition of the main weight-bearing area. Except for simple anterior or posterior wall fractures, all other fracture types may involve the quadrilateral body, and due to its special physiological anatomy and biomechanical characteristics, the position and direction of internal fixation implantation are more demanding. Complex acetabular fractures are more serious and complex intra-articular fractures, which mainly occur in young and middle-aged people with high-energy injuries, and their outcomes and prognosis are closely related to the quality of repositioning and fixation. Especially for various types of fractures involving all four sides of the body including the acetabulum, surgery requires anatomical repositioning and early functional exercise as much as possible to reduce the occurrence of long term complications. However, for complex acetabular fractures, especially comminuted fractures involving the acetabular apex area and the quadrilateral body of the acetabulum, the top of the acetabulum, the thin inner wall and the proximity to the femoral head greatly limit the type of internal fixation used in this area. The commonly used screws parallel to the quadrilateral body are difficult to place and can be easily misplaced into the joint or pelvic cavity, and even if anatomic reduction is achieved, there is a risk of loss of reduction in the long term. Therefore, it is important to design an internal fixation that conforms to local anatomy and facilitates intraoperative manipulation by the surgeon. The design concept of the Medial Pelvis Combined Locking Oblique Plate (MEP-CLOP) is based on fixing complex union fractures in the medial pelvic wall, ensuring effective fixation after repositioning, using only one internal fixation to account for as many fracture areas as possible, and safely placing the nail to reduce the operative The design concept is based on ensuring effective fixation after repositioning, using only one internal fixation to take into account as many fracture areas as possible, and safe nailing to reduce the difficulty of surgery. Based on the results of preliminary trial studies and clinical applications, it is found that MEP-CLOP has the following advantages in the treatment of complex acetabular fractures, especially those involving quadrilateral body parts. I. Anatomical design fits the medial pelvic wall The current clinical options for internal fixation of acetabular fractures are anatomical reconstruction plate and screw fixation. Some scholars found that the posterior column plate combined with anterior column retrograde tension screw and posterior column plate combined with anterior column plate can meet the clinical requirements in terms of fixation strength, among which the former has the greatest fixation strength, but the anterior column retrograde tension screw technique requires higher operator technique and equipment, and it cannot be fixed under direct vision, and if it deviates from the direction, the anterior column screw may The anterior column screw may penetrate into the joint and damage the external iliac vessels and the femoral nerve if it deviates from the direction. Clinically, reconstruction plate fixation is most common for complex joint acetabular fractures, especially for patients with severe comminution and poor bone quality. The shape of MEP-CLOP matches the irregular planes of the pelvis without pre-shaping, and the wide shape covers the entire medial wall of the pelvis, which has excellent repositioning and fixation effect for comminuted fractures. The locking nail holes on the surface of the steel plate avoid the situation that the screw holding force is insufficient due to the poor bone quality of the patient, resulting in the loss of second-stage repositioning. The unique grid design in the central area of the plate not only makes the curve of the plate fit the bone surface, but also facilitates the observation of the repositioning situation under direct vision during the operation. For quadrilateral comminuted fractures, the grid area can also be used as a bone graft placement area. The MEP-CLOP is a combination of the three main stress-bearing points and the unique modular design of the MEP-CLOP. The MEP-CLOP is designed to cover the entire anterior and posterior columns and the iliopubic wing, thus meeting the needs of almost all types of acetabular fractures. The main plate can be combined with various types of accessory plates, so that the clinician can match it with the patient’s fracture type during the operation. The choice of surgical approach is the key point in the treatment of acetabular fractures. Choosing the appropriate surgical approach is a prerequisite for high-quality repositioning and is more conducive to the recovery of the patient’s postoperative joint and limb function. Most scholars believe that the ilioinguinal approach can reveal the structure of the hip pelvic surface from the sacroiliac joint to the pubic symphysis, including the complete anterior column, the quadrilateral body surface and the medial surface of the posterior column. In anterior column fractures, they can be repositioned and fixed under direct visualization, but this approach does not reveal enough of the posterior column structures, and only part of the posterior column surface can be revealed. Although the modified Stoppa approach has the advantages of less trauma, relatively simple operation, and shorter operative time, it does not allow direct visualization of the posterior quadrilateral body, has a smaller window, has limited application, and requires additional secondary incisions once concomitant iliac fossa and iliac wing fractures are present. The Kocker-Langengback approach is mainly used for posterior column with posterior wall, transverse wall with posterior wall, and T-shaped fractures, and can also achieve a clearer visualization of the superior acetabular wall and the roof of the socket. The expanded iliofemoral approach can reveal both the anterior and posterior columns of the acetabulum, but it has the disadvantages of being more traumatic, bleeding, and difficult to operate, and the exposure of the anterior and posterior columns of the acetabulum is not as clear as that of the simple ilioinguinal approach and the K-L approach, respectively. For these reasons, many scholars at home and abroad suggest that for complex acetabular fractures involving both columns, a combined anterior and posterior incision can provide better repositioning and fixation. In the past, when a single anterolateral incision was used for posterior column fixation, longitudinal screws were generally used to fix the posterior column fracture blindly, and it was very easy to penetrate the weak area of the acetabular bone plate, and screws entering the joint or pelvis would cause serious complications. In recent years, some scholars have tried various methods to fix complex acetabular fractures using a single anterolateral approach, such as the computer-guided screw fixation technique and the anterior titanium plate combined with quadrilateral screw technique. However, the long learning curve and high equipment cost of the navigation technique make it difficult to promote its use. The anterior quadrilateral screw technique has the disadvantage of poor fixation for fractures with large displacements and severe comminution. The three locking holes in the upper part of the body of the MEP-CLOP plate use the locking guidance technique to prevent the screws from accidentally entering the acetabulum and pelvis, and the locking guidance nail can take into account the anatomic plate itself and the bone markings to correctly guide the direction of the screws, so that the accuracy of nail placement is greatly improved. The posterior column fracture can be repositioned with two locked position screws using only a single iliac inguinal approach. This design makes the intraoperative operation safer and simpler, and the wide plate allows for better repositioning of the comminuted fracture and the locking nail ensures firm fixation after repositioning, which is more advantageous than screw fixation alone. V. Direct repositioning and fixation of comminuted quadrilateral fractures without entering the true pelvis Internal fixation of the reconstruction plate along the pelvic boundary is the most common treatment method for acetabular fractures, but when it comes to quadrilateral fractures, the anatomical characteristics of the area make it difficult to expose and safely place screws, and the nail holes of the plate in this area are often left open and cannot fix the fracture directly and effectively. The screw holes in the lower part of the body of the MEP-CLOP plate allow for large angled oblique nail placement, and the matching design of the guiding sleeve and pelvic pulling hook can reposition and fix the fracture without entering the true pelvis, increasing the fixation strength. The three angled screw holes restrict the direction of screw insertion and prevent screw penetration. Precise screw placement reduces the risk of direct access to the true pelvis for repositioning and fixation. Complex acetabular fractures have long been a topic of lively discussion in the orthopedic community, and with the development of clinical treatment techniques and biomedical engineering technologies, surgical techniques and internal fixations have gradually evolved in the direction of minimally invasive, safe, and effective. Although many new technologies have improved the cure rate of acetabular fracture, the occurrence of complications such as nerve and blood vessel damage, fracture non-union, and loosening of internal fixation is still a difficult clinical problem. At present, the plate screw fixation technique is still the preferred surgical approach for complex acetabular fractures. Although the tension screw technique has the characteristics of less trauma, less bleeding and faster recovery, it is not suitable for patients with severe comminution and poor bone quality, and it requires high surgical technique and hardware conditions of the operating room, and it is not easy to master the long learning curve, and once the operation is wrong, it will cause catastrophic complications such as screw penetration into the joint and damage to blood vessels and nerves. Based on many years of clinical experience, the author designed the medial pelvic wall oblique locking combination plate (MEP-CLOP) based on the physiological anatomy and mechanical structural characteristics of the acetabulum, which is a new type of internal fixation plate designed to solve complex acetabular compound fractures, especially acetabular fractures with quadrilateral displacement that are difficult to be repositioned and reliably fixed . Although the findings of this study have yet to be verified by biomechanical tests and further clinical applications. However, with the advent of MEP-CLOP, fixation of complex acetabular fractures is no longer the exclusive preserve of advanced surgeons, and the minimally invasive, simple and safe operation allows physicians with certain clinical experience and surgical skills to master this type of surgical technique.