AB0041 TO ESTIMATE THE PREVALENCE OF ACETABULAR OSSIFICATIONS IN THE ADULT POPULATION WITH ASYMPTOMATIC, MORPHOLOGICALLY NORMAL HIPS AT CT AND TO DETERMINE WHETHER THE PRESENCE OF LABRAL OSSIFICATIONS IS ASSOCIATED WITH PATIENT-RELATED OR HIP-RELATED PARAMETERS
Authors: C. Valente, L. Haefliger, J. Favre, P. Omoumi
Journal: Annals of the Rheumatic Diseases (2021)

Background: In clinical practice, ossifications adjoining the acetabular rim are frequently seen in healthy-appearing hip joints, at all ages. The origin of these acetabular rim ossifications (ARO) is unclear. While ARO have been described by some authors as variants that may mimic marginal acetabular osteophytes, others have hypothesized that ARO may be the cause or the consequence of femoroacetabular impingement. Overall, the literature on ARO is limited, in particular in the healthy population, and their characteristics and origin not fully understood. Objectives: To estimate the prevalence of acetabular rim ossifications in the adult population with asymptomatic, morphologically normal hips at CT and to determine whether the presence of these ossifications is associated with patient-, or hip-related parameters. Methods: We prospectively included all patients undergoing thoracoabdominal CT over a 3-month period. After exclusion of patients with a clinical history of hip pathology and/or with signs of osteoarthritis on CT, we included a total of 150 hips from 75 patients. We analyzed the presence and the size of ossifications around the acetabular rim. The relationships between the size of acetabular rim ossifications and patient-related (sex, age, BMI), or hip-related parameters (joint space width, and cam- and pincer-type femoroacetabular impingement morphology) were tested using multiple regression analysis. Results: The prevalence of acetabular rim ossifications in this population of asymptomatic, non-osteoarthritic hips was 96% (95%CI=[80.1;100.0]). The presence of ossifications and their size were correlated between right and left hips (Spearman coefficient=0.64 (95%CI=[0.46;0.79]),p&lt;0.05)).The size of acetabular rim ossifications was significantly associated with age (p&lt;0.0001) but not with BMI (p=0.35), gender (p=0.05), joint space width (p≥0.53 for all locations) or any of the qualitative or quantitative parameters associated with femoroacetabular morphology (p≥0.34). Conclusion: Acetabular rim ossifications are highly prevalent in asymptomatic, non-osteoarthritic adult hips at all ages. Their size is not correlated with any patient-, or hip-related parameters except for the age. These findings suggest that ossifications at the acetabular rim, when present in isolation, should not be considered as signs of osteoarthritis or femoroacetabular impingement morphology. References: [1]J. W. T. Byrd, K. S. Jones, C. R. Freema. Surgical Outcome of Pincer Femoroacetabular Impingement With and Without Labral Ossification. Arthroscopy 2016; 32: 1022–1029. [2]P. D. Byers, C. A. Contepomi, and T. A. Farkas. A post mortem study of the hip joint. Including the prevalence of the features of the right side. Annals of Rheumatic Diseases 1970 ; 29: 15–31. [3]S. Ninomiya, A. Shimabukuro, T. Tanabe, Y. T. Kim, Y. Tachibana. Ossification of the acetabular labrum. Journal of Orthopaedics Science 2001; 5: 511–514. Table 1. Association between the average severity size of ossifications and patient-related, and hip-related parameters Regression coefficient p- value Patient-related parameters BMI 0.02 0.35 Age 0.04 &lt;0.001 Gender -0.43 0.05 Joint space width Apical 0.17 0.53 Supero-medial 0.17 0.65 Supero-lateral 0.06 0.82 Cam morphotype parameters Angle alpha 45 0.00 0.81 Offset 0.09 0.34 Pincer morphotype parameters Acetabular version angle -0.01 0.83 Lateral center-edge angle 0.02 0.56 Acetabular index 0.03 0.53 Crossover sign 0.26 0.41 Posterior wall sign -0.25 0.47 Figure 1. Coronal reformats of CT examinations showing different sizes of labral ossifications in the posterosuperior quadrant (arrows). (a) No labral ossification, (b-c-d-e) Increasingly large labral ossification from left to right. Two lines are visible at the location of the ossification, formed by the contour of the acetabular rim and of the ossification (double line-sign). Disclosure of Interests: None declared