RESUMO
Supracondylar fractures are common injuries in children. Diagnosis typically relies on radiography, which can involve long wait times in the ED, emits ionizing radiation, and can miss non-displaced fractures. Ultrasound (US) has the potential to be a safer, more convenient diagnostic tool, especially with new highly portable handheld 2D point of care US (POCUS). This study aimed to determine the reliability of 2D POCUS for the detection of supracondylar fractures and elbow joint effusions, to contrast the accuracy of 2D POCUS vs. 3DUS vs. radiographs, and to determine whether blinded image interpretation could produce similar results to non-blinded real-time imaging. Fifty-seven children were scanned with 2D POCUS and 3DUS on the affected elbow. US scans were then read by three blinded readers, and the results were compared to gold-standard radiographs. Compared to a gold standard of 30-day radiographic diagnosis, readers of 2D POCUS detected supracondylar fracture and effusion with sensitivities of 0.91 and 0.97, respectively, which were both higher than with 3DUS. Inter-rater reliability of fracture detection was moderate for 2D POCUS (k = 0.40) and 3DUS (k = 0.53). Consensus sensitivities, although high, were lower than reports from some non-blinded studies, indicating that clinical presentation serves as an important factor in detection rates. Our results from consensus US diagnosis support the validity of using 2D POCUS in children for supracondylar fracture and elbow effusion diagnosis.
RESUMO
High resolution peripheral quantitative computed tomography (HR-pQCT) was designed to study bone mineral density (BMD) and microarchitecture in peripheral sites at the distal radius and tibia. With the introduction of the second generation HR-pQCT scanner (XtremeCT II, Scanco Medical) that has a larger, longer gantry it is now possible to study the human knee in vivo using HR-pQCT. Previous validation of HR-pQCT measurements at the distal radius and tibia against micro-CT is not representative of the knee because the increased cross-sectional area, greater amount of soft tissue surrounding the scan region, and different imaging protocol result in potentially increased beam hardening effects and photon scatter and different signal-to-noise ratio. The objective of this study is to determine the accuracy of density and microarchitecture measurements in the human knee measured by HR-pQCT using an in vivo protocol. Twelve fresh-frozen cadaver knees were imaged using in vivo HR-pQCT (60.7 µm) protocol. Subsequentially, distal femurs were extracted and imaged using a higher resolution (30.3 µm) ex vivo protocol, replicating micro-CT imaging. Scans were registered so that agreement of density and bone microarchitecture measurements could be determined using linear regression and Bland-Altman plots. All density and microarchitecture outcomes were highly correlated between the 2 protocols (R2 > 0.89) albeit with statistically significant differences between absolute measures based on paired t tests. All parameters showed accuracy between 4.5% and 8.7%, and errors were highly systematic, particularly for trabecular BMD and trabecular thickness (R2 > 0.93). We found that BMD and microarchitecture measurements in the distal femur obtained using an in vivo HR-pQCT knee protocol contained systematic errors, and accurately represented measurements obtained using a micro-CT equivalent imaging protocol. This work establishes the validity and limitations of using HR-pQCT to study the BMD and microarchitecture of human knees in future clinical studies.
