Comparison of intra-and interobserver reliability analysis of orientation proximal femur physis parameters on radiographs

Background

The orientation of proximal femur physis is important as it can cause 3-dimensional deformity of the proximal femur. Recently, authors have described various parameters to describe the orientation of proximal femur physis. Therefore, we aim to compare the intra and interobserver reliability of these parameters in this study.

Methods

Radiographs of the bilateral hip with the pelvis of children between 1 and 10 years of age were retrieved from the hospital archives to measure the Physeal orientation angle (PO), Physeal tilt angle (PTA), Head shaft angle (HSA), and Alsberg angle (AA). Intra- and inter-observer reliability was tested using Pearson's correlation coefficient and Cronbach's alpha respectively by three independent observers at two separate times, two weeks apart.

Results

The total analysis included 179 radiographs, including 378 hips. PO, PTA, HSA, and AA had values ranging from 9.57⁰ -14.04⁰, 19.62°-25.04⁰, 58.75°-65.82⁰, and 24.47⁰ -31.79⁰, respectively, for the six data sets (three observers at two different times).The intra-observer reliability of PO, PTA, HSA, and AA ranged from 0.59- 0.72, 0.9–0.95, 0.91–0.95 and 0.86–0.95 respectively. PO, PTA, HSA, and AA had inter-observer reliability values between 0.79 -0.82, 0.88–0.92, 0.85–0.88, and 0.89–0.92, respectively.

Conclusion

The study found that PTA, AA, and HSA have shown good reliability, but they may not accurately represent the true orientation of the capital femoral physis with respect to the femoral neck. For routine follow-up, PO may be a suitable alternative. However, it is not as reliable as other parameters.