The assessment of femoral shaft morphology in the sagittal plane in Chinese patients with osteoarthritis-a radiographic analysis

Background: The purpose of this study was to analyze femoral shaft sagittal parameters in Chinese osteoarthritis (OA) patients undergoing total knee arthroplasty (TKA) and identify whether the parameters in the coronal plane could be predictors of those in the sagittal plane. Methods: Standard long-standing anteroposterior and femoral lateral radiographs of 50 lower limbs in 50 Chinese OA patients were included. Sagittal femoral bowing angle (sFBA), angle between femoral distal anterior cortex axis and sagittal mechanical axis (DACSMA), angle between femoral distal anterior cortex axis and sagittal distal anatomic axis (DACSDAA), and angle between femoral sagittal mechanical axis and sagittal distal anatomic axis (SMADAA) were measured. Then the relationship between femoral shaft parameters in the sagittal and coronal planes were identified, including coronal femoral bowing angle (cFBA), valgus angle, hip-knee-ankle angle (HKA), length of femur (LF), femoral offset, femoral neck stem angle (FNS), and mechanical lateral distal femoral angle (mLDFA). A two-sided Pearson correlation coefficient was obtained to identify the correlations between parameters in the coronal and sagittal planes. P values < 0.05 were considered statistically significant. Results: The mean sFBA was 15.08 degrees +/- 3.79 degrees, the mean DACSMA was 1.35 degrees +/- 2.70 degrees, the mean DACSDAA was -2. 66 degrees +/- 2.05 degrees, and the mean SMADAA was 4.01 degrees +/- 2.55 degrees. No correlation between parameters in the coronal and sagittal planes was found. Conclusions: In this study, the discreteness of DACSMA, DACSDAA, and SMADAA in Chinese OA patients is high and this may affect the position of femoral prosthesis after TKA using the conventional intramedullary device. No parameters in the coronal plane are found correlated with those in the sagittal plane.