A three-dimensional virtual morphometry study of the sigmoid notch of the distal radius

Abstract

Our primary objectives were to create a reliable, noninvasive method for three-dimensional morphometry of deep bony parameters within the sigmoid notch of the distal radius, to identify its morphological patterns, and to identify any significant variation between the left and the right wrists. Our secondary objectives were to obtain morphometric values that could represent our population and to identify any possible ethnic variations. Methods: Computed tomography scans of 102 wrists from 51 healthy individuals were analyzed using a virtualization software. Four anatomical parameters at the distal radius sigmoid notch, namely, the radius of curvature, depth, version angle, and sagittal slope were measured. Morphological patterns of the sigmoid notch surface were identified. The results were statistically analyzed to assess the reliability of the technique and were compared with previously published literature. Results: Comparing our findings with previously published values, our study revealed a slightly larger radius of curvature and sagittal slope, while revealing a smaller depth and version. We identified the S-type, C-type, and ski-slope morphological variants. The flat-face morphological variant, however, was not identified. The sigmoid notch at the left and right wrists were similar, except for the radius of curvature. Conclusion: This study demonstrates a noninvasive, fast, reliable, and reproducible technique for analyzing the sigmoid notch of the distal radius. In wrist injuries with intact distal radius sigmoid notch but involving comminuted fractures of the ulnar head, ulnar head replacement may be indicated. In such cases, analysis of the ipsilateral intact sigmoid notch would allow us to prepare an ulnar head prosthesis of appropriate size.

Midsectional Magnetic Resonance Imaging Analysis of the Sigmoid Notch of the Distal Radioulnar Joint

“…The sigmoid notch is no exception, and the present MRI study confirms the four main morphology types originally described by Tolat et al 7 In their cadaver study, the most represented morphologies were type A (42%) and type C (30%), with type B and type D each representing 14% of the wrists. In a study on 102 wrists, Shivdas et al 12 found a majority of type D (52%), and some type C (26.4%) and type B (21.6%) variants, but they did not identify any type A (flat type). In our study, the most represented morphology was type C (60%), followed by type B (30%); types D and A were the least represented (6 and 4%, respectively).…”

“…This discrepancy may be due to the limited number of wrists in our study, the study of healthy subjects rather than cadavers, and measurements completed using MRI rather than CT scans. 12 Tolat et al 7 based their descriptions on visual observation of midcoronal sections, lacking the defined elements of MRI analysis. Furthermore, compared to the cadaveric study of Tolat, the rest are based on biaxial imaging data.…”

A radiographic study of dorsovolar wrist axes and a database of angular measurements on axial computed tomography images

“…The principal axes of the wrist on axial CT sections are used as a reference in studies for following conditions: the distal radius anatomy, [1,4,8,15] rotational malalignment due to distal radius or shaft fractures, [7,9,16] anatomic and kinematic studies of the carpal region, [5,6,10] and DRUJ anatomy. [5,11,12,[17][18][19] Several anatomical locations have been used as principal axis of the distal radius in the past, including, the central axis, [4,[7][8][9]11,12,16] volar cortical axis at metaphyseal level, [5,8,9] and sigmoid notch axis. [5] In the current study, a series of angular measurements based on axial CT images provided improved data for evaluating radiographic anatomy of the wrist.…”

“…The sigmoid notch version angle is a fundamental axial parameter of the distal radius, [5,11,12,[17][18][19] This angle was used as a reference for kinematic studies of the DRUJ [5] and associated with some clinical conditions including triangular fibrocartilage tear [19] and DRUJ instability. [11,19] Jung et al [19] found an association between the DRUJ instability and the flat-face type of sigmoid notch described by Tolat et al [21] A flat-faced sigmoid notch inherently has a lower version angle, [19] and can be reconstructed with osteoplasty in case of instability.…”

“…Normative values of the sigmoid notch version angle have also been reported in a number of studies. [5,11,12,[17][18][19] Results of other studies are heterogeneous possibly, due to nonuniform measurement techniques. To illustrate, some [17][18][19] have measured the sigmoid notch version angle with reference to the dorsal half of the sigmoid notch itself as the principal reference axis and obtained mean values of 9°, 10°, and 13°.…”