Abstract
ObjectivesTo evaluate differences in collagen density as detected by dual-energy computed tomography (DECT) of wrist ligaments between patients with calcium pyrophosphate-dihydrate deposition disease (CPPD) and a control group in order to gain insight into changes of the extracellular matrix in response to crystal deposition.Materials and methodsThis retrospective study included 28 patients (18 with CPPD, 10 controls) who underwent DECT of the wrist. Collagen density maps were reconstructed from the DECT datasets and used to measure densities in regions of interest (ROIs) placed in the scapholunate (SL) ligament (dorsal, palmar, proximal), lunotriquetral (LT) ligament, and extensor carpi radialis (ECR) tendon, (n = 260 measurements). The presence of calcifications on standard CT images in these regions was assessed by a blinded reader. Densities were compared with nonparametric tests, and linear regression analysis was performed to investigate the impact of age, sex, and CT- detected calcium deposition on collagen density.ResultsCollagen density in the SL ligament was significantly higher in CPPD patients than in controls (overall mean: 265.4 ± 32.1 HU vs. 196.3 ± 33.8 HU; p < 0.001). In the ECR tendon, collagen densities did not differ significantly (p = 0.672): 161.3 ± 20.1 HU in CPPD vs. 163.6 ± 12.0 HU in controls. Regression analysis showed that diagnosis, but not age or calcification, had a significant impact on collagen density.ConclusionCollagen density of the SL ligament is significantly higher in CPPD patients than in control patients. Further research is needed to understand these changes in the extracellular matrix of ligaments in CPPD.
Highlights
Calcium pyrophosphate dihydrate crystal deposition disease (CPPD) has been described as the third most common inflammatory arthritis [1], affecting predominantly the elderly [2]
While dual-energy computed tomography (DECT) was traditionally mainly used for imaging in gout [12], recent studies have critically evaluated its capacity to differentiate between different forms of crystal arthropathy [13] and demonstrated its ability to visualize bone marrow edema [14, 15]
A total of 260 individual collagen density measurements were recorded—another 20 measurements could not be included due to macroscopic calcification (n = 5), ankylosis (n = 3), and SL ligament rupture (n = 6), or because the region was not included in the scan (n = 6)
Summary
Calcium pyrophosphate dihydrate crystal deposition disease (CPPD) has been described as the third most common inflammatory arthritis [1], affecting predominantly the elderly [2]. While DECT was traditionally mainly used for imaging in gout [12], recent studies have critically evaluated its capacity to differentiate between different forms of crystal arthropathy [13] and demonstrated its ability to visualize bone marrow edema [14, 15]. Another pioneering application of the technique has been the visualization of collagen, first demonstrated by Johnson et al [16]. A number of investigations have shown collagen mapping using DECT to be feasible in the Skeletal Radiol (2021) 50:417–423 imaging of the ligaments of the knee [17, 18] and the tendons of the hands and feet [19]
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