Purpose: Although several indexes have been used for patellar height evaluation, the literature on patellar height evaluation using a femoral reference point is scant. We have previously reported on a new index, the modified Blumensaat (MB) method, which evaluates the patellar height using a femoral reference point. The purpose of this study was to evaluate the validity of the MB method.
Methods: In addition to 10 volunteers (group C), 10 men (group M) and 10 women (group F) who underwent knee surgery were selected for the study. The Insall-Salvati (IS), modified IS (MIS), Blackburne-Peel (BP), MB, and modified intercondylar-shelf-angle-corrected Blumensaat (MIB) ratios were measured on lateral knee radiographs with the knee in 30°, 40°, and 50° flexion.
Results: In group C, the MB and MIB ratios were similar; the IS ratio was not dependent on the knee flexion angle, and there was no significant difference in the MIS and BP ratios between 40° and 50° of knee flexion and in the MB and the MIB ratios between 30° and 40° of knee flexion. There were no differences between group M and group F with respect to any of the indexes. Furthermore, the differences in all indexes among the different knee flexion angles, in groups M and F, were similar to those in group C.
Conclusions: The MB method is applicable for patellar height evaluation and is recommended with a knee flexion angle of 30°-40°.