Treatment Strategies and Complications in Reverse-Oblique Trochanteric Femur Fractures and Evaluation of a New Classification System

<b>Background:</b> Reverse-oblique femoral fractures are regarded as highly unstable and are still associated with high complication and failure rates. A new classification system is said to facilitate risk assessment and decision-making. <b>Methods:</b> Over ten years, 7804 patients with per/subtrochanteric fractures were screened in this retrospective analysis. A total of 552 patients with a reverse-oblique fracture pattern were included. The fractures were classified according to the new classification system. The choice of implants, complication rates, revision surgery, and time of surgery were recorded. Radiological outcome parameters and dislocation were measured. <b>Results:</b> For the classification, a good intra-rater reliability (r = 0.77) and inter-rater reliability (k = 0.64) were calculated. The complication rate was overall 19% (n = 105). More than 60% of complications needed revision surgery. The most common complications were cut-out and implant failure (3%); only Parker's ratio, as a radiological parameter, had prognostic value. Malreduction had a negative impact on mal- or non-unions (<i>p</i> < 0.01), and a trend towards higher overall complications (<i>p</i> = 0.52). Prolonged time of surgery increased the overall complication rate (r = 0.2, <i>p</i> < 0.001). The same was found after open reduction (<i>p</i> = 0.005, OR 2.00). The use of cerclage wires had no positive or negative effects. The use of short or long implants did not influence the outcome. <b>Conclusions:</b> Reverse-oblique femoral fractures are associated with a high complication rate. Short implants can be safely used in cases without severe dislocation if a sufficient working length is considered. Anatomical reduction benefits the outcome as long as it can be performed closed. The classification system presents good inter- and intra-rater reliability.