Ultrasound evaluation of greater trochanter pain syndrome in patients with spondyloarthritis: are there any specific features?

Although greater trochanter pain syndrome (GTPS) is a prevalent cause of musculoskeletal pain in the general population, there is lack of imaging studies searching for differential features of inflammatory enthesitis in GTPS. We analyzed the features of GTPS using sonography and magnetic resonance imaging (MRI) to identify useful differential signs between spondyloarthritis (SpA) and other inflammatory or non-inflammatory musculoskeletal diseases. All patients with unilateral GTPS attended by our Arthritis Unit between February 2011 and March 2012 were included. Patients were classified as having SpA or mechanical (without inflammatory musculoskeletal disease) GTPS. Rheumatoid arthritis (RA) patients were also included as inflammatory controls. Ultrasound scans of the painful and contralateral, asymptomatic, greater trochanter were made. We assessed the gluteus medius and gluteus minimus tendons for signs suggestive of tendinopathy. Random MRI of the same regions was made in a subgroup of patients to validate the ultrasound findings. A total of 107 patients with unilateral GTPS were included, of whom 96 were female, with a mean age of 61.6 years: 34 had SpA, 48 had non-inflammatory musculoskeletal disease, and 25 had RA. No specific sonographic features for SpA were found. Pathological findings were more frequent in patients without musculoskeletal inflammatory disease (mainly bursitis and erosions). A large number of alterations were found in the asymptomatic side (around 40 % had cortical irregularities and 20 % bursa effusion). Signs of enthesopathy were more prevalent in the gluteus minimus tendon, regardless of the diagnosis (54.2 % had erosions, 39.3 % bursitis, 38.3 % calcifications and 37.4 % tendinosis). No patient had power Doppler signal. Age was the main factor in the appearance of tendinopathy. MRI confirmed the changes detected by ultrasound in all 40 patients evaluated. GTPS in patients with SpA has similar sonographic findings to those observed in patients with RA and patients without musculoskeletal inflammatory disease. Neither sonography nor MRI was clinically useful in classifying GTPS as a manifestation of SpA.