Hoffa fracture: the CT classification system / 中华创伤骨科杂志

ABSTRACT

Objective To introduce a new CT classification system we designed for Hoffa fractures and compare the interrater reliability between the CT and X-ray classification systems.Methods A total of 20 isolated Hoffa fractures from January 2008 to December 2011 were randomly selected for the present analysis of their imaging data (anteroposterior and lateral X-ray films of the knee joint and three-dimensional CT reconstruction of the femoral condyle).At the same time,a total of 20 independent observers (clinicians with junior,intermediate and senior professional qualifications) were selected for classification of the Hoffa fractures in the same manner respectively according to the Letenneur's X-ray system and our self-designed CT system.We used Kappa statistics to evaluate the interrater reliability among the clinicians between the 2 classification systems for Hoffa fractures.Results According to the CT classification of the 20 Hoffa fractures by the 20 clinicians,type Ⅰ,Ⅱ and Ⅲ fractures accounted for 66.0％,30.5％ and 3.5％ respectively.In type Ⅰ fractures,type Ⅰb involving zone b accounted for the most (50.0％),next by type Ⅰc(31.0％) and type Ⅰa (19.0％).In type Ⅱ comminuted fractures,fracture fragments were mostly seen in zone b.The overall incidence of fractures involving zone b by CT classification was 67％.According to the X-ray classification,type Ⅰ,Ⅱ,Ⅲ and Ⅳ fractures accounted for 31.4％,14.3％,28.0％ and 26.3％,respectively.The interrater reliability for CT classification agreement (Kappa =0.681) among clinicians was higher than that for X-ray agreement (Kappa =0.261).Conclusion For Hoffa fractures,communicated ones in particular,our CT classification system may be better than the X-ray classification system.