Diagnostic accuracy of hip joint ultrasound for detection of calcium pyrophosphate deposition

Objective CPPD disease is a chronic and disabling arthropathy. US has been shown to be a tool with high sensitivity and specificity for the diagnosis of CPPD disease, but its value at the hip joint has not yet been determined. Therefore, our objective was to evaluate the diagnostic accuracy of US for the identification of CPP crystals in the hip joint as compared with histopathology.Methods Diagnostic test study involving patients over 50 years of age with osteoarthritis, scheduled for hip replacement surgery. US was performed on the affected hip. Acetabular fibrocartilage (FC) and hyaline cartilage (HC) of the femoral head were assessed, and a dichotomous score was used for the presence/absence of CPP crystals. SF was obtained from the affected hip and examined using polarized light microscopy. Histopathological examination was performed by an experienced pathologist in search of CPP crystals in FC and HC samples.Results One hundred patients were enrolled, of whom 62% were found to have hyperechoic areas suggestive of CPP deposition on US examination. Pathological evaluation revealed a prevalence of 61% of CPP crystals. The sensitivity, specificity and the positive predictive and the negative predictive values were 90%, 82%, 89%, and 84%, respectively. The area under the curve for US compared with histopathology for the diagnosis of hip CPPD was 0.86 (95% CI: 0.78-0.94).Conclusion US is a valid imaging modality with good diagnostic accuracy for the detection of hip CPPD.