## 4 Discussion  
The development of an automated system for FHC/DAE measurement represents a significant step toward improving the objectivity and reliability of CHD assessments. This study evaluated the system's agreement with expert human examiners to determine its clinical applicability, ensuring that automated classifications align with established methodologies. The results demonstrated strong inter-rater agreement and reliability between the two human examiners (E1 and E2), as well as high concordance between the system and E1, who served as the reference standard. These findings allow us to reject the null hypothesis, which stated that there is no agreement beyond chance in the FHC/DAE classifications made by the two examiners and between the examiners and the automated system. Additionally, the system exhibited consistent performance across both frequent and less common classification categories, supporting its potential as a robust tool to assist in CHD scoring. However, some classification tendencies were noted, particularly a slight shift toward less severe categories, which may have implications for clinical decision-making. The system also demonstrated strong performance, with precise keypoint detection by the FHC model and accurate acetabular segmentation by the DAE model. The following discussion explores the key findings in depth, addressing the strengths and limitations of our automated FHC/DAE measurement system. Beyond automation, the reliability of CHD assessment is ultimately limited by the diagnostic metrics that define it. While the NA has been a longstanding reference, its methodological limitations and susceptibility to anatomical variability challenge its role as a universal standard [6; 9]. These concerns warrant a closer examination of complementary approaches, particularly the FHC/DAE metric, which offers distinct advantages. A primary limitation of the NA is its dependence on acetabular morphology, which varies considerably across breeds. Studies have shown that using a universal NA cutoff of \(\geq\)105\({}^{\circ}\) leads to inconsistencies and a high rate of false positives, potentially excluding genetically valuable dogs from breeding populations [6; 9]. [PERSON] et al. highlighted that the prominence of the CrAR directly influences the NA, with more pronounced rims leading to larger angles [9]. Conversely, structural irregularities such as CrAR notching, characterized by indentations along the rim that disrupt its continuity, steepen the cranial curvature, and result in a flattened appearance, can lower the NA [2; 9]. Additionally, osteophyte formation, which refers to localized new bone formation, on the cranial aspect of the acetabular margin can create the appearance of a double rim in the VDHE view, making the CrAR more difficult to identify [34; 35]. Furthermore, variations in acetabular depth contribute to breed-dependent differences [9], introducing additional inconsistencies. Both the NA and the FHC/DAE metrics require precise definition of the femoral head and its center. However, they differ in the other anatomical landmarks upon which they \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & & & & & **System** & & & \\ \cline{3-8}  & **Medial+** & **Medial** & **Super** & **Lapsed** & **Lateral+** & **Luxation** & **Total** \\ \hline \multirow{5}{*}{E2} & **Medial+** & 5 & 2 & 0 & 0 & 0 & 0 & 7 \\  & **Medial** & 1 & 5 & 3 & 0 & 0 & 0 & 9 \\  & **Super** & 0 & 5 & 56 & 0 & 0 & 0 & 61 \\  & **Lapsed** & 0 & 0 & 11 & 37 & 2 & 0 & 50 \\  & **Lateral+** & 0 & 0 & 0 & 4 & 8 & 0 & 12 \\  & **Luxation** & 0 & 0 & 0 & 0 & 0 & 1 & 1 \\  & **Total** & 6 & 12 & 70 & 41 & 10 & 1 & 140 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Contingency Table of FHC/DAE Classifications Between Examiner 2 (E2) and System. rely. While the NA depends on the CrAR, the FHC/DAE is determined by the DAE. In this context, we believe that the FHC/DAE metric offers distinct practical advantages.