Ultrasonography and color Doppler of proximal gluteal enthesitis in juvenile idiopathic arthritis: a descriptive study

Abstract

Background: The presence of enthesitis (insertional inflammation) in patients with juvenile idiopathic arthritis (JIA) is difficult to establish clinically and may influence classification and treatment of the disease. We used ultrasonography (US) and color Doppler (CD) imaging to detect enthesitis at the small and deep-seated proximal insertion of the gluteus medius fascia on the posterior iliac crest where clinical diagnosis is difficult. The findings in JIA patients were compared with those obtained in healthy controls and with the patients' MRI results.

Methods: Seventy-six proximal gluteus medius insertions were studied clinically (tenderness to palpation of the posterior iliac crest) and by US and CD (echogenicity, thickness, hyperemia) in 38 patients with JIA and in 38 healthy controls, respectively (median age 13 years, range 7-18 years). In addition, an additional MRI examination of the sacroiliac joints and iliac crests was performed in all patients.

Results: In patients with focal, palpable tenderness, US detected decreased echogenicity of the entheses in 53% of the iliac crests (bilateral in 37% and unilateral in 32%). US also revealed significantly thicker entheses in JIA patients compared to healthy controls (p < 0.003 left side, p < 0.001 right side). There was no significant difference in thickness between the left and right sides in individual subjects. Hyperemia was detected by CD in 37% (28/76) of the iliac crests and by contrast-enhanced MRI in 12% (6/50).

Conclusions: According to US, the gluteus medius insertion was thicker in JIA patients than in controls, and it was hypoechoic (enthesitis) in about half of the patients. These findings may represent chronic, inactive disease in some of the patients, because there was only limited Doppler flow and MRI contrast enhancement. The present study indicates that US can be useful as an adjunct to clinical examination for improved assessment of enthesitis in JIA. This may influence disease classification, ambition to treat, and choice of treatment regimen.

Figure 1

Schematic, lateral view of the iliac bone. The fascia of the gluteus medius muscle (Gmed) inserts proximally on the posterior aspect of the iliac crest, dorsally to the insertion of the iliotibial band (itb) on the gluteal tubercle (gt) and anterior to the insertion of the gluteus maximus muscle (Gmax). TFL = tensor fascia latae muscle.

Figure 2

Longitudinal US scanning of the proximal insertion of the gluteus medius fascia on the posterior iliac crest in a child lying on the side.

Figure 3

Schematic view of different grades of enthesopathy of the gluteus medius insertion as presented in longitudinal US scans. Gmed = gluteus medius muscle, ap = apophysis. Grade 0: normal enthesis. The fascia is a thin echorich line. Grade 1 enthesopathy: hypoechoic fascial thickening at the insertion. Grade 2 enthesopathy: small cranial triangular hypoechoic area in the muscle between fascia and iliac crest. Grade 3 enthesopathy: large hypoechoic area in the muscle with caudal extension.

Figure 4

Transversal US scanning of the proximal insertion of the gluteus medius fascia on the posterior iliac crest in a child lying on the side.

Figure 5

Longitudinal US scanning of the proximal enthesis of the gluteus medius fascia on the posterior iliac crest in a 13 year old healthy control. A) The insertion is measured (1) perpendicularly to the iliac crest at the level of the physis (ph). The gluteus medius (Gmed) fascia (F) is hyperechoic and thin. The apophysis (ap) is cartilaginous. B) No hyperemia is seen on longitudinal CD examination.

Figure 6

Transversal US scanning of the gluteus medius fascia in a healthy control. A) The wavy aspect of the gluteal fascia caused by the longitudinal reinforcements. The fascia is hypoechoic due to the anisotropic artifact. B) Schematic view of longitudinal fascia reinforcements in a transversal US scan.

Figure 7

The normal gluteus medius muscle and fascia in an adult cadaveric specimen. A) Lateral view showing the longitudinal fascia reinforcements over the gluteus medius muscle (Gmed). The iliotibial band (itb) inserts on the gluteal tubercle (gt) of the iliac crest and covers the greater trochanter (troch). TFL = tensor fascia latae muscle. The gluteus maximus muscle is resected. B) Transversal cut of the Gmed insertion. Gmax = gluteus maximus. C) Longitudinal cut of the Gmed insertion at the level of a fascia reinforcement. D) Longitudinal cut of the Gmed insertion between fascia reinforcements.

Figure 8

Longitudinal CD examination showing normal arteries (blue) and veins (red) between the iliac bone and the gluteus medius muscle (Gmed) with collateral perforants extending through the muscle.

Figure 9

Longitudinal US scanning of gluteus medius enthesopathy in patients with JIA. A) Grade 1: hypoechoic fascial thickening at the insertion (arrow). B) Grade 2: small cranial triangular hypoechoic area in the muscle between fascia and iliac crest (arrows), here with a thin caudal extension. C) Grade 3: large hypoechoic area in the muscle with caudal extension (arrows). D) Longitudinal CD examination shows hyperemia at the insertion.

Figure 10

Transversal US scanning of the gluteus medius fascia insertion in a patient with JIA and enthesopathy. A) The wavy aspect, due to the longitudinal reinforcements of the fascia, is visualized in the thickened fascia. B) Transversal CD examination shows hyperemia at the insertion.

Figure 11

US and MRI images of a 15 year old boy with JIA and enthesitis. A) Fat suppressed T2-weighted MRI sequence showing bilateral, physiological edema of the iliac crests (arrows). Focal muscle edema at the left gluteus medius insertion (arrowhead) indicates enthesopathy. B) Longitudinal US with CD of the left insertion showing a hypoechoic area and hyperemia. C) T1-weighted MRI sequence before intravenous gadolinium contrast injection. D) Fat suppressed T1 sequence after contrast injection showing enhancement (arrowhead) in the muscular insertion.