Computer tomography acquired hip angles and patient reported outcomes in patients with femoroacetabular impingement syndrome

Abstract

Purpose: Patients with femoroacetabular impingement syndrome (FAIS) experience pain, decreased function and quality of life. Patients present with cam and/or pincer morphology in their hip joint. FAIS is diagnosed via imaging, clinical signs and symptoms. In large cohorts using radiological measures, cam morphology has been associated with later development of osteoarthritis (OA) of the hip while it is less certain how pincer morphology is related to development of OA. In the cohort studies, pincer morphology was quantified using the lateral center edge angle (CE) and the anterior CE angle. Pincer, defined this way, was not associated with development of OA. However, quantifying pincer only by these two angles may not give the full picture of pincer impingement and its relation to hip OA. Hence, further description of abnormal values in patients with FAIS could help investigate the pathogenesis of FAIS. Furthermore, associations between patient reported outcomes and the specific angles might highlight which radiological parameters affect outcomes experienced by the patients. Hence, the aims of the study were 1) to describe computer tomography (CT) acquired angles in patients with FAIS compared with reference values from the literature 2) to investigate the association between hip angles in patients with FAIS and the Copenhagen Hip and Groin Outcome Score (HAGOS) and if HAGOS scores differ between patients with hip angles above/below mean reference values. Methods: Patients were eligible for inclusion if they were scheduled for primary hip arthroscopic surgery for FAIS. The study was approved by the Central Denmark Region Committee on Biomedical Research Ethics (1-10-72-239-14) and the Danish Data Protection Agency (1-16-02-499-14). The CT images of the hip were acquired on a Philips Brilliance 64 (Philips Medical Systems, Best, the Netherlands) scanner with low-dose radiation. Furthermore, a single image through the femoral condyles was obtained to measure the femoral anteversion (FeAV). Data were transferred to a Philips Mx view station (Philips Medical Systems, Best, the Netherlands). On the reformatted images the alpha angle, the CE angle, the acetabular index (AI), the posterior acetabular sector angle (PASA), the anterior acetabular sector angle (AASA), the horizontal acetabular sector angle (HASA) and the acetabular anteversion (AcAV) was measured by an experienced musculoskeletal radiologist. All patients completed the HAGOS. Associations between patient reported outcomes and hip angles was tested with linear regression. Comparisons between HAGOS data above/below mean reference values of hip angles were performed with the Wilcoxons test for unpaired data. Results: Sixty patients aged 36 ±9, 63% females were included in the study. Hip angles (55 patients) and HAGOS scores (60 patients) are tabulated in Table 1. Hip angles were not associated with any of the HAGOS scores. Those patients with a higher FeAV, PASA and HASA than reference mean values had worse HAGOS scores compared to those with lower hip angles than reference mean values. Conclusions: Patients presented with a high FeAV angle and many patients had a low AI angle. There was no overall association between HAGOS scores and hip angles, but patients with a high FeAV, PASA and/or HASA had worse HAGOS scores. These angles should be further investigated in order to investigate the pathogenesis of FAIS and to investigate whether the angles are related to later development of hip OA. Table details: ∼ Healthy reference values from Valera et al. 2018 Arch Orthop Trauma Surg, Lepage-Saucier et al. 2014 Eur Radiol and Kierkegaard et al. 2017 Journal of Science and Medicine in Sport. ∗ For the acetabular index angle, it is %patients below the reference meanTable 1Hip angles and HAGOS scores.Patients (mean±standard deviation)Healthy reference values (mean±standard deviation) ∼%patients with scores higher than reference mean (number of pt.)Affected legAlpha51.7 ±9.653.3 ±13.138% (21)FeAV27.5 ±10.517 ±391% (50)CE33.1 ±5.635 ±640% (22)AI2.8 ±6.06 ±569% (38)*AASA59.2 ±6.663 ±631% (17)PASA94.9 ±6.8103 ±911% (6)HASA154.1 ±9.3165 ±942% (23)AcAV18.0 ±4.724 ±547% (26)HAGOSPain51 ±20100Symptoms47 ±17100Activities of daily living53 ±24100Sport34 ±18100Physical activities21 ±23100Quality of life31 ±15100 Open table in a new tab