[Characteristics of posterior coronal banana-shaped fragments and its research progress in treatment of intertrochanteric femoral fracture with cephalomedullary nail].

Objective: To summarize the characteristics of posterior coronal banana-shaped fragments and its research progress in treatment of intertrochanteric femoral fracture with cephalomedullary nail, provide valuable reference for clinical practice. Methods: Relevant domestic and foreign literature was extensively reviewed to summarize the history, anatomical structure of posterior coronal banana-shaped fragments, and the need for reduction and fixation, the influence on the stability of cephalomedullary nail, and the remedies. Results: The posterior coronal banana-shaped fragments refers to the second level fracture line of the intertrochanteric femoral fracture, involving four anatomical structures, namely, the posterior part of the greater trochanter, the intertrochanteric crest, the lesser trochanter, and the posteromedial cortex. With the wide application of three-dimensional-CT in clinical practice, the posterior coronal banana-shaped fragments were more comprehensively understood. According to whether the anterior extension of the fracture line affects the integrity of the lateral entry of the head and neck implant, the posterior coronal banana-shaped fragments can be divided into small and large ones, of which the large single banana-shaped fragment account for about 20% of the AO/Orthopaedic Trauma Association (AO/OTA) type A2 fractures. If the large fragment involving the posteromedial wall (lesser trochanter) will increase the difficulty of the medial cortical contact reduction; or involving the posterolateral wall and resulting in rupture of the entry portal (type A2.4), which will cause sagittal swing of the nail in the femoral marrow cavity, thereby affecting the stability of the nail. There is no effective technique for reduction and fixation of the banana-shaped fragment nowadays. However, the adverse effects of posterior coronal banana-shaped fragment can be compensated by improving the quality of fracture reduction and choosing high filling cephalomedullary nail. Conclusion: The posterior coronal banana-shaped fragments can easily lead to the rupture of the entry portal of head-neck implants, cause the sagittal swing of the cephalomedulis nail, and then lead to the loss of fracture reduction and affect the treatment effect. Whether the entry portal rupture or not and its risk factors still need further clinical and basic research.