Digital measurement and correlation analysis of anatomical CT for clinical application in the hip joint

Abstract

BACKGROUND: The complexity of hip joint anatomy makes it difficult to quantitatively assess by parameter indexes, and real-image rendering technology is important for the accurate display of hip joint microstructure and detection of diseases. OBJECTIVE: To evaluate the anatomical and morphological parameters of the hip joint through three-dimensional digital measurement by CT multi-planar reconstruction and cinematic rendering, compare the differences and analyze the correlation, so as to provide a precise anatomical parameter basis for the diagnosis and evaluation of hip-related diseases and hip replacement. METHODS: A total of 156 subjects (312 hips) aged ≥18 years without hip trauma or disease were included and divided into 6 groups by 10-year age intervals. CT images were processed with cinematic rendering and multi-planar reconstruction. Bilateral hip joint parameters including acetabular abduction angle, femoral head center distance, acetabular coverage, acetabular depth, neck-shaft angle, femoral offset, center-edge angle, acetabular anterior sector angle, acetabular posterior sector angle, and acetabular anteversion angle were measured. SPSS software was used to compare differences between different age groups and analyze correlations among anatomical parameters and with clinical baseline data. RESULTS AND CONCLUSION: (1) Significant differences were found between left and right sides for neck-shaft angle and femoral offset (P < 0.05). (2) By gender, acetabular abduction angle, femoral offset, and acetabular anteversion angle were greater in females than males (P < 0.05). (3) By age group, the young group had smaller acetabular maximum depth, acetabular coverage, acetabular anterior sector angle, acetabular posterior sector angle, and center-edge angle than the elderly group (P < 0.05). (4) No significant differences were found between traditional and innovative methods for acetabular coverage, and between coronal and axial positions for acetabular maximum depth, but significant correlations existed (r=0.76, 0.95, P < 0.01). Acetabular abduction angle was negatively correlated with body mass index, acetabular coverage, acetabular maximum depth, center-edge angle, acetabular anterior sector angle, and acetabular posterior sector angle (P < 0.05), and the latter five indicators were positively correlated with each other (P < 0.01). (5) Cinematic rendering and multi-planar reconstruction are beneficial for precise measurement and evaluation of hip joint anatomical parameters. There are significant differences in parameters among different genders and age groups, showing certain characteristic trends, and significant correlations exist among different anatomical parameters.

1. Introduction

The hip joint is the largest weight-bearing joint in the human body, a ball-and-socket joint with significant flexion, extension, and rotational mobility, playing a crucial role in locomotion. Consequently, it is also the most frequently affected joint [1]. The anatomical structure of the hip is complex, and with aging and lifestyle changes, degenerative changes can occur. For the detection of subtle hip lesions, multi-slice spiral CT three-dimensional reconstruction has been recognized by clinicians and plays an irreplaceable role in personalized and precise treatment compared with X-ray plain films [2]. However, traditional CT three-dimensional reconstruction techniques (such as shaded surface display and volume rendering) still have limitations in presenting the extremely complex bony anatomical details (e.g., subtle articular surface morphology, osteophytes, cortical continuity) and spatial relationships of the hip joint. The generated images sometimes fail to achieve the 'surgical-grade' realism and spatial depth required by surgeons, especially in distinguishing closely adjacent structures such as the femoral head and acetabular labrum [3-4].

More importantly, despite providing three-dimensional views, orthopedic surgeons still need to mentally reconstruct two-dimensional tomographic images and three-dimensional models during preoperative planning to understand lesions and anatomical details and estimate key anatomical parameters. This process heavily relies on the surgeon's experience and spatial imagination, and the quantitative assessment of fine anatomical parameter ranges (such as acetabular abduction angle, femoral offset, acetabular anteversion) is often conceptually vague and lacks objective consistency [5-6]. MARATT et al. followed up 120 patients after total hip arthroplasty in 2012 and found that 30% had lower limb length discrepancy, poor hip function, and some had claudication, largely related to inaccurate preoperative assessment of anatomical parameters and planning errors [7].

Cinematic rendering technology originated from post-production special effects in film. It maps the gray values of each voxel in the original image to a three-dimensional space through transfer functions, and then applies different transfer functions to render the object, ultimately optimizing the image quality and providing a more realistic and immersive visualization.