Findings at the Bone-Component Interface in Symptomatic Unicompartmental Knee Arthroplasty and the Relationship to Radiographic Findings

Excerpt

We thank Sabour et al. for their interest in our study and thoughtful comments. They indicate that to assess agreement or reproducibility of a qualitative variable, using Cohen’s kappa statistic (κ) is not always appropriate, since a κ value depends on the prevalence in each category and on the number of categories. When a variable with more than two categories or an ordinal scale is used, the weighted κ would be more optimal to assess inter-rater agreement. In our study, the presence or absence (nominal variable) of each magnetic resonance imaging (MRI) finding was scored and used to calculate the inter-rater agreement of all findings (bone marrow edema, fibrous membrane, osteolysis, and loosening) [2]. Two of these findings were graded according to an ordinal scale: bone marrow edema as the volume of marrow that was involved and fibrous membrane as the percentage of the implant interface that was involved [1]. …