Proximal femur fractures have significant functional repercussions in both older adults (sometimes life-threatening) and younger adults (socioeconomic). This study will review the early mechanical complications (EMC) associated with the fixation of femoral neck (FNF) and trochanteric (TF) fractures. What is the nature of these complications? They consist of incorrect fracture fixation, secondary displacement and/or fixation failure (FNF: 3–10%; TF: 5–7%), and more rarely, secondary fractures distal to the implant. What are the risk factors and how can they be controlled? They are related to the patient (osteoporosis), to the type of fracture (FNF: posterior comminution, magnitude of displacement, vertical fracture line, fracture of calcar/TF: comminution of calcar, lesser trochanter fracture, metaphyseal comminution, lateral cortex fracture, greater trochanter comminution), to the chosen treatment (FNF: triple screw fixation or screw-plate are preferable/TF: all implants suitable for simple fractures, cervicomedullary implants for complex fractures), and to the surgical technique (quality of reduction, implant positioning). How should they be treated? Early revision of internal fixation can be difficult and increases the infection risk. Inter- or subtrochanteric valgus osteotomy leads to satisfactory results but is difficult to carry out. Secondary arthroplasty, which is the preferred option in older adults, leads to good outcomes but is technically more difficult, and has a higher complication rate in EMC of trochanteric fractures.

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