Computerized anatomy of the distal radius and its relevance to volar plating, research, and teaching

Abstract

Distal radius fractures are common and fracture patterns and fixation can be complex. Computerized anatomy evaluation (CAE) might offer non-invasive and enhanced anatomy assessment that might help with implant selection and placement and screw length determination. Our goal was to test the accuracy of two CAE methods for anatomical volar plate positioning and screw lengths measurement of the distal radius. We included 56 high-resolution peripheral quantitative computed tomography scans of intact, human distal radii. Plates were placed manually onto 3D printed models (method 1), which was compared with automated computerized plate placement onto the 3D computer models (method 2). Subsequently, screw lengths were determined digitally for both methods. Screw lengths evaluations were compared via Bland-Altman plots. Both CAE methods resulted in identical volar plate selection and in anatomical plate positioning. For screw length the concordance correlation coefficient was ≥0.91, the location shift ≤0.22 mm, and the scale shift ≤0.16. The differences were smaller than ±1 mm in all samples. Both CAE methods allow for comparable plate positioning and subsequent screw length measurement in distal radius volar plating. Both can be used as a non-invasive teaching environment for volar plate fixation. Method 2 even offers fully computerized assessments. Future studies could compare our models to other anatomical areas, post-operative volar plate positioning, and model performance in actual distal radius fracture instead of intact radii. Clin. Anat. 32:361-368, 2019. © 2018 The Authors. Clinical Anatomy published by Wiley Periodicals, Inc. on behalf of American Association of Clinical Anatomists.

Keywords: anatomy; radius; tomography.

Figure 1

Modeling workflow of M1: A: a right volar plate fixed on an exemplified 3D printed model of the distal radius; B: left: CT scan with orthogonal views of a 3D printed distal radius and a semi‐automated segmented 3D model of the plate (green) (note also CT artifacts due the metallic implant), right: computer model of a right distal radius (yellow) with attached volar plate (green) after CT scanning and image segmentation; C: computer model of the right distal radius (yellow) and the registered virtual plate template (blue). [Color figure can be viewed at wileyonlinelibrary.com]

Figure 2

Computerized screw length measurements: A: volar plate with screws in neutral positions without specific screw angulations (volar and lateral views), B: the two parallel screws (green), manually oriented more distally toward the styloid process with 15° angulation (dorsal view), C: labeling of the screw hole positions in narrow, normal and wide plates. [Color figure can be viewed at wileyonlinelibrary.com]

Figure 3

Virtual plate positioning onto the volar side of a computer model of the distal radius: A: manually placed landmarks (green) used for pre‐alignment of the virtual plate template, B: final position of the plate template after running the optimization algorithm. [Color figure can be viewed at wileyonlinelibrary.com]

Figure 4

Box plots (left), scatter plot (middle) and Bland–Altman plot (right) for C1 when comparing M1 versus M2. [Color figure can be viewed at wileyonlinelibrary.com]

Figure 5

Example for additional screw HR‐pQCT measurements (gray values given in vBMD) at a given screw position (VA5) when using virtual methods. [Color figure can be viewed at wileyonlinelibrary.com]