Ultrasound imaging can be reliably used to identify calcium pyrophosphate crystal (CPP) deposits in the hip joints of patients with calcium pyrophosphate deposition disease (CPPD), according to a preliminary study published in Arthritis Care & Research.
Researchers evaluated the comparability, sensitivity, and specificity of ultrasound imaging and conventional radiography when detecting CPP in patients with CPPD (n=50) and age-, gender-, and body mass index-matched controls (n=40). A total of 180 hips (100 hips in patients with CPPD and 80 hips in matched controls) were evaluated.
All patients completed a clinical examination, a synovial fluid analysis, an ultrasound examination of the anterior acetabular labrum fibrocartilage and the hyaline cartilage on the femoral head, and a conventional radiography examination with antero-posterior views.
Ultrasound detected calcium pyrophosphate crystal deposits in at least 1 hip in 45 out of 50 patients with CPPD.
CPP deposits were more frequently found at the acetabular labrum fibrocartilage vs the femoral head hyaline cartilage (72% and 17% of the hips in patients with CPPD, respectively).
Conventional radiography detected CPP deposits in at least 1 hip in 43 out of 50 patients with CPPD (86.0%) and in 4 out of 40 disease controls (10.0%; P <.0001), and in 72 out of 100 hips in patients with CPPD (72.0%) and in 5 out of 80 hips in disease controls (6.3%, P <0.0001).
Total agreement between the ultrasound findings and conventional radiography findings was 77.8%. There was no statistically significant difference found between ultrasound and conventional radiography for sensitivity (P =.5), specificity (P =.5) and diagnostic odds ratio (P =.25)
Future studies need to include across-operator reproducibility, incorporate a fluid analysis from the hip joint, and determine proper handling of hyperechoic spots and other pathological conditions that could lead to an incorrect diagnosis.
The researchers concluded that these findings indicate ultrasound imaging is comparable to conventional radiography for sensitivity and specificity for identifying CPP deposits and “should be regarded as the fist-line imaging technique in the assessment of the hip joint in patients with suspected [calcium pyrophosphate deposition disease] because of its reliability and safety compared to [conventional radiography].”
Di Matteo A, Filippucci E, Cipolletta E, et al. Hip involvement in patients with calcium pyrophosphate deposition disease: potential and limits of musculoskeletal ultrasound [published online November 26, 2018]. Arthritis Care Res (Hoboken). doi: 10.1002/acr.23814