Evaluation of the Interobserver Agreement of the Fraser and Blake & McBryde Classifications for Floating Knee

Objective  To evaluate the interobserver agreement of two classifications for floating knee: Fraser and Blake & McBryde. Method  Thirty-two observers, subdivided according to the degree of titration (26 resident physicians and 6 orthopedic physicians specialized in orthopedic trauma), classified 15 fractures of the ipsilateral femur and tibia. Interobserver agreement was evaluated by using the Kappa coefficient . Result  When evaluating the agreement between the 9 R1, a Kappa index of 0.58 was obtained for the Fraser classification and of 0.46 for the Blake & McBryde classification. Among the 7 R2, a rate of 0.59 was obtained for the Fraser rating and 0.51 for the Blake & McBryde rating. Among the 10 R3, the agreement index was higher for both classifications: 0.72 for the Fraser and 0.71 for the Blake & McBryde classification. Considering the 3 groups (R1, R2, R3) as one large group, the general Kappa index was calculated, which resulted in 0.63 for the Fraser classification and 0.56 for the Blake & McBryde classification. In the group of trauma and orthopedic knee specialists, in turn, an agreement of 0.597 was obtained for the Blake and McBryde classification and of 0.843 for the Fraser classification. Conclusion  Comparatively, the two classifications presented a weak to moderate degree of agreement. Fraser classification had better agreement in both groups. The agreement was higher when evaluating orthopedic trauma physicians.