510 What Is the Posterior Condylar Offset Ratio for Both the Medial and Lateral Femoral Condyles?

Abstract

Abstract Aim Traditionally, the posterior condylar offset ration (PCOR) has been calculated from lateral radiographs however new evidence suggests that a measuring technique based on 3D imaging may be superior. MRI has been trialled, but no protocol has been standardised and evaluated for reliability. This study aims to create a reproducible and reliable MRI technique as well as exploring whether there are any morphological differences in PCOR. Method A team of 5 researchers collaborated to create 2 novel ways of evaluating PCOR on healthy knees, one based on the transepicondylar axis (TEA) and one on the posterior condylar axis (PCA). The hospital database was searched for all MRI scans reported as having no internal derangement. From the 103 eligible scans a sample of 10 scans was selected and analysed by 4 independent reviewers in order to assess inter-rater reliability. The same sample was also analysed by one reviewer on two separate occasions in order to establish intra-rater reliability. Results Both methods demonstrated no significant difference in morphology between the condyles. Gender was found not to be a significant factor in condylar morphology. When calculating the PCOR the TEA method has a good intra-rater reliability and shows a higher degree of inter-rater reliability than the PCO protocol, yet consensus was not achieved among all reviewers using either method. Conclusions No significant morphological differences between condyles or genders were found. A TEA method may be superior for measuring PCOR nevertheless it is difficult to establish an easily applicable, reliable, and reproducible protocol.