# How Common Is Femoroacetabular Impingement Morphology in Asymptomatic Adults? A 3D CT-Based Insight into Hidden Risk

## TL;DR

This study uses 3D CT scans to find that a significant number of asymptomatic adults have hip structures linked to femoroacetabular impingement, suggesting potential for early detection.

## Contribution

The study provides new empirical insights into the prevalence of FAI morphology in asymptomatic adults using 3D CT analysis.

## Key findings

- Cam-type FAI features were found in 25.6% of right hips and 13.9% of left hips in asymptomatic individuals.
- Males had higher alpha angles than females, indicating a higher prevalence of cam-type deformities in males.
- Pincer-type FAI morphology was more sporadic and often unilateral in asymptomatic hips.

## Abstract

Background and Objectives: Femoroacetabular impingement (FAI) morphology refers to structural abnormalities that can alter normal joint mechanics and potentially lead to early onset osteoarthritis. Although commonly diagnosed in symptomatic individuals, such morphological features are also found in asymptomatic adults, underlining their relevance for early detection and preventive management. This study aimed to evaluate the three-dimensional congruence of hip joint surfaces in relation to FAI and the morphology of asymptomatic hips with potential FAI features. Materials and Methods: Retrospective three-dimensional reconstructions of 86 hip joints were created using Mimics software from computed tomography (CT) scans of the lower abdomen and pelvis retrieved from the radiology archive. CT scans belonged to individuals with preserved anatomical integrity (20 females, 23 males, bilateral hips), aged 24–76 years. Lateral center-edge angle (LCEA) and alpha angle measurements were obtained from reconstructions to assess the risk of asymptomatic FAI. Results: Significant gender differences were found in alpha angles. The mean right alpha angle was 46.57 ± 3.12° in females and 49.28 ± 6.66° in males p = 0.046, while the mean left alpha angle was 43.75 ± 5.53° in females and 47.37 ± 5.77° in males p = 0.021. An alpha angle >50°, suggestive of cam type FAI, was present in 25.6% of right hips and 13.9% of left hips. LCEA values showed no significant gender or side differences, with a mean of 30.21 ± 8.96° across the cohort. Conclusions: Three-dimensional evaluation of asymptomatic hips revealed FAI-consistent morphology in a notable proportion of individuals, particularly males. Cam-type deformities tended to occur bilaterally, whereas pincer-type morphologies were more sporadic and often unilateral. Increased alpha and LCEA measurements in asymptomatic individuals suggest that FAI morphology may exist subclinically without always indicating disease. Future studies incorporating longitudinal imaging and clinical follow-up are needed to clarify the prognostic significance of these findings.