Extract
To The Editor:We read with great interest "Quantifying the Extent of Femoral Head
Involvement in Osteonecrosis" (2003;85:309-15), by Cherian et al. We
think that the authors achieved good agreement because the evaluators
discussed ways to clarify the evaluation techniques prior to the study. This
was lacking in the study by Kim et al.1. We agree with the authors
that intraobserver and interobserver agreements improve with practice.
However, we think that measuring the necrotic arc angle has some drawbacks. It
is not easy to identify the center of the femoral head, even using a template
of concentric circles, because femoral heads are not spherical. It is possible
that most readers think that the center is located too inferiorly and
posteriorly in Figure 1-B in the article. Another drawback is that it is very
confusing to draw two arms of the necrotic arc angle when the center is
located inside a necrotic area or the shape of a lesion is irregular. Necrotic
lesions with a very irregular configuration are frequently seen on magnetic
resonance imaging, and a good method should be applicable to all situations.
We would appreciate it if the authors would describe a concrete method to
determine the center of a femoral head and identify the margin of irregular
lesions as seen in Figure 2 in the article by Kim et al.1.