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A novel radiological classification system of the distal femur



In our previous studies, we were able to identify anatomical differences as a predictor for aseptic loosening following primary and revision surgery with the use of rotating hinge prosthesis. This study was performed to answer following question: can a novel radiological classification system of the distal femur be identified?

Materials and methods

A total of 200 patients who received standardized anteroposterior (AP) and lateral views of the knee joint were included in this study. On AP radiographs, we measured the distance between inner diameter of the femur at 20 cm proximally from the knee and at a point 2 cm proximally from the adductor tubercle. The ratio of the inner diameter of the femoral canal at 20 cm proximal of knee joint to the inner diameter of medullary canal at 2 cm proximal of adductor tubercle was used as a novel index ratio. Two observers blindly and independently reviewed the anteroposterior radiographs twice.


Three groups of anatomical classification can be constructed for each sex according to the 25th and 75th percentiles. A higher distribution of Type C was found in female patients. The median intra-observer reliability for rater 1 was 0.995 (IQR 0.994–0.997). We had also a high inter-observer reliability with ICC of 0.997 (95% CI 0.996–0.998).


The novel classification presents three different types of the knee joint for male and female patients. Type C has a wider inner diaphyseal diameter compared to Type A with a narrow inner diaphyseal diameter.

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Correspondence to Mustafa Citak.

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The authors declare that they have no conflict of interest regarding this manuscript. Independent from the submitted manuscript, received royalties/payments of all authors are listed: payments for presentations from Waldemar Link, Hamburg, Germany, Zimmer Biomet Inc., Warsaw, USA. Heraeus, Ceramtec Co.

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Ethical approval was performed and has following number: WF-086/20.

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Citak, M., Levent, A., Suero, E.M. et al. A novel radiological classification system of the distal femur. Arch Orthop Trauma Surg 142, 315–322 (2022).

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  • Novel classification system
  • Radiological
  • Inter-observer reliability
  • Intra-observer reliability
  • Distal femur