The crescent sign—a predictor of hip instability in magnetic resonance arthrography

Abstract

Currently, much is debated on the optimal treatment of borderline hips, being in the continuum between stable and unstable hips. The diagnosis of stability is often difficult but is a prerequisite for further treatment. Analysis includes a variety of radiographic parameters. We observed that unstable hips often had a crescent-like gadolinium collection in the postero-inferior joint space. We therefore questioned if the ‘crescent sign’ could be an indicator for hip instability? A retrospective comparative study was conducted including 56 hips in the instability group (treated with PAO) and 70 hips with femoroacetabular impingement (FAI) as control group. Based on standard radiographic parameters and magnetic resonance imaging (MRI), the association between hip instability and the ‘crescent sign’ was analyzed. For univariate group comparisons, the non-parametric Wilcoxon two sample test was used. Association between discrete variables was examined by means of chi-square tests. To examine predictive variables, logistic regression models were carried out. Most hips with a crescent sign belong to the instability group. A crescent sign has a sensitivity of 73.3% and specificity of 93% for instability. Based on our results, the crescent sign is a factor that is more prevalent in unstable hips. However, its absence does not exclude instability of the hip. If present, the specificity speaks strongly in favor for instability of the hip.

SSR white paper: guidelines for utilization and performance of direct MR arthrography

“…The cliff sign on radiographs is said to be highly specific for hip micro-instability, up to 100% sensitive and specific in women under 32 years [ 325 ]. One study suggested utilizing dMRA to visualize a crescent shaped pooling of contrast in the posteroinferior joint space, and the crescent sign has recently been proposed as being relatively specific for the diagnosis of hip instability [ 243 ]. Another study of dMRA found a thinner anterior capsule (2.5 mm) and wider anterior recess (5.8 mm) in patients with capsular laxity at arthroscopy [ 326 ].…”

Präoperative MRT-Bildgebung bei Hüftdysplasie

“…3c). Letzteres wurde in der MR-Arthrographie beschrieben und ist gemäß aktueller Literatur ein nützliches Zeichen zur Beurteilung der Instabilität bei Patienten mit grenzwertiger Hüftdysplasie [84].…”

A New Parameter of Hip Instability in Developmental Dysplasia of the Hip (DDH): Teardrop Distance

“…Radio stereometric analysis (RSA) has also been applied to measure the in vivo 3D kinematics of the joint by tracking the position of implanted titanium beads. However, this invasive technique limits the subject population to patients who have undergone surgical intervention and is difficult to be applied to the native hip joint (10)(11)(12)(13)(14)(15). Some hip indicators based on anteroposterior pelvic radiographs, such as reduced LCEA, subluxated femoral head, deficient acetabular wall with concomitant insufficient femoral coverage, positive femoro-epiphyseal acetabular roof (FEAR) index, upsloping lateral sourcil, can also indicate hip instability.…”