Background: The fabella is a sesamoid bone having anatomical variations and it is more common in patients with primary keen osteoarthritis (KOA). The purpose of this study was to classify the fabellae and discuss the relationship between the classification of fabellae and the severity of KOA in Chinese.
Material and methods: 136 patients were measured and classified using CT three-dimensional reconstruction. According to the CT imaging characteristics, the fabellae were divided into 5 types: type Ⅰ, a fabella on the lateral femoral condyle; type Ⅱ, a fabella on the medial femoral condyle; type Ⅲ, a fabella on the lateral femoral condyle and a fabella on the medial femoral condyle; type Ⅳ, two fabellae on the medial femoral condyle and type Ⅴ, two fabellae on the lateral femoral condyle. The severity of KOA was assessed on the Recht grade by MRI. The data were analyzed with SPSS 24.0.
Results: The classification of fabellae were correlated with KOA grades (c 2 =35.026, P<0.05). In terms of KOA grades, grade Ⅰ and grade Ⅱ were occupied most of fabellar type Ⅱ (32, 72.8%); type Ⅱ and other types were significant statistical difference (P<0.05). Grade Ⅰ and grade Ⅱ were also the most of fabellar type Ⅳ (4, 100%). Fabellar type Ⅴ’s biggest component were grade Ⅲ and grade Ⅳ (6, 75%). Type Ⅳ and type Ⅴ were significant statistical difference (P<0.05).
Conclusion: The classification of fabellae were correlated with KOA grades. The type Ⅱ may mean the lower KOA grades while type Ⅴ may mean the higher KOA grades.
Trial registration: the Ethics Inspection Committee at Southwest Medical University, V1.0/20180801. Registered 20 August 2018.