Low-dose computed tomography as diagnostic tool in calcium pyrophosphate deposition disease arthropathy: focus on ligamentous calcifications of the wrist.

OBJECTIVES

To identify specific morphologic features of calcium pyrophosphate deposition disease (pseudogout, CPPD) manifestations of the wrist as detected using low-dose CT-scans.

METHODS

In this retrospective study 46 patients with arthritis of the wrist were included. All patients underwent a low dose CT scan of both wrists on a 320-row detector in volume scan mode. Individual radiation exposure was recorded for all patients. Two blinded raters independently evaluated osteoarthritis, cysts, erosions, calcifications (cartilage and ligaments separately) and carpal misalignment in 33 specified locations. An expert rheumatologist classified the patients as CPPD positive or negative. Fisher's exact test was applied to identify differences between both groups. Receiver operating characteristics (ROC) analyses with calculations of area under the curve (AUC) were carried out for both in the literature established and newly identified imaging findings for each rater individually.

RESULTS

Twenty-seven patients were classified as CPPD, 19 patients as other diagnoses. Ligamentous calcifications were significantly more prevalent in the CPPD group (p<0.05). All non-ligamentous findings revealed no difference in frequency. AUC analysis for established findings (0.675; 0.619 - rater 1; 2) vs. ligamentous calcifications (0.786 both raters) showed a markedly higher diagnostic accuracy for the latter. Effective radiation exposure was determined to be 0.019-0.095 mSv per patient.

CONCLUSIONS

Calcifications of carpal ligaments are highly specific morphologic features of CPPD arthropathy. Low-dose CT is a useful tool to detect these calcifications at a radiation exposure similar to a standard radiograph.