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Purpose: Scapholunate dissociation frequently results in malalignment and scapholunate advanced collapse (SLAC). Previous analyses have relied on visual observations of carpal angles among the scaphoid, lunate, and capitate on lateral radiographs. However, the 3-dimensional carpal alignment during SLAC progression remains unclear. The purpose of this study was to analyze 3-dimensional carpal malalignment in SLAC wrists., Methods: Using computer-aided cone-beam computed tomography analysis software based on segmentation and numerical modeling, we defined three-dimensional carpal axes and examined alignment and carpal height ratio in 18 SLAC wrists along the radial coordinate (positive in palmar and ulnar directions). These results were compared with previously reported normal alignment values obtained from 121 healthy wrists., Results: In the sagittal plane, mean scapholunate, lunotriquetral, lunocapitate, and capitometacarpal angles were -100° (SD, 11°); 20° (SD, 11°); 7° (SD, 12°); and 18° (SD, 8°); respectively, whereas the angles were -58° (SD, 9°); 12° (SD, 8°); -17°(SD, 11°); and 8° (SD, 6°); respectively, in healthy wrists. The sagittal scapholunate angle exhibited the highest area under the receiver operating characteristic curve (0.999), with a threshold value of ≤-76°, indicating pathology. In the coronal plane, the carpal alignment of SLAC wrists remained unchanged, excluding a minimal ulnar tilt of the capitate., Conclusions: Carpal malalignment in SLAC wrists not only affects the radio- and midcarpal joints, but also extends to the third carpometacarpal joint, with malalignment evident in both the sagittal and coronal planes. In SLAC wrists, the sagittal lunotriquetral angle increases in the positive direction, due to the lunate angulating more than the triquetrum., Clinical Relevance: These findings have potential to contribute to the development of computer-aided diagnostic tools for 3-dimensional imaging technology. In the future, such tools could highlight abnormal values and minimize diagnostic errors in clinical practice., Competing Interests: Conflicts of Interest Dr Alanen reports support from Vappu Uuspää foundation. Dr Höglund reports grant for PhD studies from Finska Iäkäresaliskapet (2021, 2022, and 2023) and Varppu Uuspään säätio (2020). Dr Sippo reports research grant from the Finnish Medical Foundation. Dr Waris owned stock in Disior Ltd, Helsinki, Finland and sold them in January 2022. No benefits in any form have been received or will be received by the other authors related directly to this article., (Copyright © 2024 American Society for Surgery of the Hand. Published by Elsevier Inc. All rights reserved.)

The purpose of this study was to compare computer-aided analysis and different methods of manual measurements in the evaluation of carpal alignment. The radioscaphoid, radiolunate, radiocapitate and radiometacarpal angles were measured on cone-beam computed tomography (CT) scans of 30 healthy wrists by automated software (Disior Ltd.) and by hand surgeons using lateral radiographs reconstructed from the CT data. Hand surgeons were either given ( n  = 6) or not given ( n  = 7) prior instructions on how to perform the measurements. Inter- and intra-observer reliability of manual measurements ranged from good to excellent (intra-class correlation coefficients [ICC] 0.77-0.99), being highest in specialists with standardized methods and in reconstructed radiographs with bone overlap digitally removed. Computer-aided software provided excellent intra-observer reliability (ICC 0.94-1.00) consistently and values that were highly comparable (mean difference range 1°-7°) with the manual measurements made in optimal settings. Computer-aided software provides an accurate and repeatable method to measure carpal alignment in CT scans, minimizing observational errors., Competing Interests: Declaration of conflicting interestsThe authors declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: EW has owned stock in Disior Ltd, Helsinki, Finland and sold them in January 2022. The other authors have no conflicts of interest to declare.

Background: Several carpal pathologies are considered to be related to ulnar variance. Recently, computer-aided computed tomography (CT) analysis software was introduced to quantify three-dimensional (3D) carpal alignment with high accuracy and reliability., Purpose: To determine the association of ulnar variance with 3D carpal alignment and demographics., Material and Methods: A wrist of 121 asymptomatic volunteers (69 men, 52 women; mean age = 38 ± 10.4 years) was imaged in the neutral wrist position with cone-beam CT. Computer-aided CT analysis software (Bonelogic), based on segmentation and numerical modelling, was used to define ulnar variance and standardized 3D axes for all carpal bones. The association of ulnar variance with 3D carpal alignment, age of the volunteer, and side and dominance of the imaged wrist was assessed., Results: The mean ulnar variance was -1.6 ± 1.5 mm (range = -5.3 to 2.4 mm). The mean ulnar variance was -1.9 mm and -1.1 mm in men and women ( P  = 0.007), respectively. Of the imaged 121 wrists, 18 (15%) had positive and 103 (85%) negative ulnar variance. There was no association between ulnar variance and any of the radio- or intercarpal angle values in either the sagittal or coronal plane (ρ = -0.16…0.17, r  = -0.13….0.12). The ulnar variance showed no association with side ( P  = 0.51) or dominance ( P  = 0.27) of the imaged wrist., Conclusion: 3D carpal alignment is not affected by ulnar variance. The association of ulnar variance with sex may in part explain the difference in reported prevalence of some carpal pathologies, such as ulnar impaction syndrome and Kienböck's disease., Competing Interests: Declaration of conflicting interestsThe authors declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: EW has owned stock in Disior Ltd., Helsinki, Finland and sold them in January 2022. The other authors have no conflicts of interest to declare.

We examined the reliability of a computer-aided cone-beam CT analysis of radiographic parameters of 50 normal distal radii and compared it with interobserver agreement of measurements made by three groups of physicians on two-dimensional plain radiographs. The intra-rater reliability of the computer-aided analysis was evaluated on 33 wrists imaged twice by cone-beam CT. The longitudinal axis, anterior tilt, radial inclination and ulnar variance were measured. The reliability of computer-aided analysis was excellent (intraclass correlation coefficient (ICC) 0.94-0.96) while the interobserver agreement of two-dimensional radiograph interpretation was good (ulnar variance, ICC 0.80-0.84) to poor (anterior tilt and radial inclination, ICC 0.20-0.42). We conclude that computer-aided cone-beam CT analysis was a reliable tool for radiographic parameter determination, whereas physicians demonstrated substantial variability especially in interpreting the angular parameters.