The anterior hip capsule is thinner in dysplastic hips: a study comparing different young adult hip patients

Abstract

Purpose To investigate the thickness and intra-substance change of anterior capsule of the hip joint, and compare the difference of the capsular features in patients with diferent statuses of hip stability. Methods A retrospective study was performed to review a hip preservation database. Using the lateral center edge angle(LCEA), patients with borderline dysplasia of the hip (BDH) of 20° ≤ LCEA ≤ 25°, femoracetabular impingement(FAI) with LCEA > 30° and dysplasia of the hip (DH) of LCEA < 20° were enrolled and stratiied into diferent treatment groups. The patients' imaging was reviewed by two experienced musculoskeletal radiologists who were blinded to clinical outcomes. Thickness and intra-substance change of the anterior hip capsule was measured on the sagittal oblique sequences of MRI. A surgeon measured the thickness of the anterior hip capsule during arthroscopy. The capsular thickness and intra-substance change were compared among diferent groups. Results Thirty patients (17 women and 13 men) enrolled in each group (FAI, BDH, and DH) matched by sex and ages were evaluated. There were no signiicant diferences in terms of age, sex, BMI, Alpha angle, and Tönnis grade among all three groups. The mean thickness of the anterior capsule in the DH group was 3.2 ± 0.5 mm, which was signiicantly thinner than that in the BDH and FAI groups (4.5 ± 0.8 mm and 4.7 ± 0.6 mm), and there was no signiicant diference in capsular thickness between the BDH and FAI groups. The Median of anterior capsule thickness via arthroscopic measuring was 6 mm and 7 mm in the BDH and FAI groups respectively, which has no statistical diference. The intra-substance change of the anterior capsule shows a signiicant diference among the three groups, and a higher incidence of delamination of the capsule was found in DH groups (p < 0.001). Conclusions Patients with hip dysplasia have a signiicantly reduced capsular thickness on MRI and delaminated anterior joint capsule, which could be a sequence of instability. The clinical relevance of this study is that capsular thickness and intra-substance changes of the anterior capsule vary which could alter capsular management strategies. Level of evidence Level III of evidence, DIAGNOSTIC STUDIES, No consistently applied reference standard.

Femoral neck-shaft angle can predict the anterior capsular thickness in patients with femoracetabular impingement syndrome

“…Males had a significantly thicker capsule than females, this result is in line with previous studies [1, 7, 10, 20]. Interestingly, the LCEA angle and BTS were not significantly corrected with ACT in our study.…”

“…Bai et al reported that patients with hip dysplasia had a significantly reduced ACT compared with FAIS and borderline DDH patients (4.7 ± 0.6 mm and 4.5 ± 0.8 mm, respectively). They attribute this to the sequence of hip instability, the thinner capsular thickness could be the result of repetitive strains from hip instability [1]. The current study did not include dysplasia or borderline dysplasia patients to exclude the effect of LCEA angle on capsular thickness.…”

“…2). ACT was measured on proton density‐weighted oblique‐sagittal sequence through the anterior inferior iliac spine (AIIS) around the site of routine capsulotomy (interportal capsulotomy) during arthroscopy [1, 10]. The Picture Archiving and Communication System was used for ACT measurement and values were given with two decimal places.…”

“…Rakhra et al reported that the capsule was thicker in cam impingement and chondrolabral pathology hips compared with asymptomatic control hips [15]. Bai et al reported that developmental dysplasia of the hip (DDH) patients had a significantly reduced anterior capsular thickness (ACT) compared with femoracetabular impingement syndrome (FAIS) patients [1].…”

Magnetic Resonance Imaging and Magnetic Resonance Arthrography Are Both Reliable and Similar When Measuring Hip Capsule Thickness in Patients With Femoroacetabular Impingement Syndrome

“…This measurement strategy allows for a more consistent quantification of the hip capsule than has been shown in previous work. 16 , 17 Repeatable measurement protocols of hip capsule thickness are increasingly important as the focus on the hip capsule continues to rise. Our findings demonstrate an opportunity for future standardization of hip capsule measurements on advanced imaging studies.…”