Objective To summarize the research progress of posterior coronal banana-shaped fragments in the 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, the need for reduction and fixation, the influence on the stability of cephalomedullary nail, and the remedies of posterior coronal banana-shaped fragments. Results  With the wide application of three-dimensional-CT in clinical practice, the posterior coronal fragments were more comprehensively understood, and the banana-shaped fragments accounted for about 20% in A2 type pertrochanteric femur fractures. According to whether the fracture line involves the entry portal of head-neck implants or not, the coronal fragments were divided into two types: small and large. 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 banana-shaped fragment can be compensated by improving the quality of fracture reduction and choosing high filling cephalomedullary nail. Conclusion The extension of the posterior coronal fracture line on the lateral wall may affect the entry portal of head-neck implants, which will impair the bone-nail integral stability in the sagittal plane. Whether the entry portal will rupture or not and its risk factors still need further clinical and basic research.