Paprosky femur defect classification. Diagram showing the classification system for femur cortex defects used to assess revision (replacement or repair) of a hip implant. The ball and socket part of the implant is at top. The rest of the implant consists of a shaft inside the femur (thigh bone). The amount of degradation in the cortical (outer) bone layer determines the amount of bone grafting needed, and whether a cementless implant can replace a cemented one. Six regions are labelled, and five subtypes described (type IV not shown). Named for US surgeon Wayne G. Paprosky, the classification was developed in the 1980s and 1990s. For specific types, see images C016/6622 to C016/6637.