Pearls and Pitfalls of the Volar Locking Plating for Distal Radius Fractures

ANATOMICAL STUDY OF VOLAR FACE OF DISTAL RADIUS AND COMPARISON WITH THE SHAPE OF LOCKING VOLAR PLATES

ABSTRACT Objective: To evaluate the volar cortical angle (VCA), the variation in lateral and intermediate columns, the shape and pattern of the watershed line (WL) of the distal radius and its correlation with locking volar plates available. Methods: 27 human cadaveric radial bones of the Department of Morphology and nine locking volar plates of six different companies were analyzed. VCA were measured from lateral and intermediate columns and their corresponding values on plates, as well as comparing the relief of radius and plates. In the WL analysis, we compared the standard format found on the radius and its equivalent on plates and divided into four types: biconvex, convex, ulnar convex and plan. Results: VCA varied between columns of the distal radius extremity. The mean in the lateral column was 153.40 degrees and 146.06 degrees in the intermediate. Four of nine plates showed no variation in volar angulation. From 27 distal radius, 13 showed convex pattern and 12 had biconvex, whereas most plates (seven of the nine analyzed) were biconvex drawing. Conclusion: Radial bone anatomy was variable. The intermediate column was, on average, steeper than lateral column. Synthes®-2 plate presented the closest design to the anatomy of the distal end of the radial bone, followed by Newclip®-2 plate. Level of Evidence II, Anatomic and Descriptive Study.

Interpretations of the Term "Watershed Line" Used as Reference for Volar Plating

Objective  The objective of this systematic review is to provide an overview of all interpretations of the definition of the watershed line used in literature. Methods  The Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) guidelines were followed for this review. A comprehensive search was performed for definitions of the watershed line given in literature. A total of 32 studies giving an explicit interpretation of the definition of the watershed line or anatomical reference for plate positioning in writing and/or imaging were included. Results  In 32 studies, we found eight different landmarks used to refer to the watershed line or correct plate positioning. Five studies used two different soft tissue landmarks. Six different bony landmarks were described in 24 studies. These could further be subdivided into three anatomical interpretations, described in seven studies, in which the term "watershed line" is explained as a distinguishable anatomical line, and two surgical interpretations, described in 15 studies, which are purely reflecting the optimal location of the volar plate. One interpretation of the watershed line described in two studies combined both anatomical and surgical landmarks. Conclusion  The (mis)interpretation of the definition of the term "watershed line" as described by Orbay is subject to the type of landmarks and purpose used: soft tissue or bony landmarks and an anatomical or a surgical purpose. A clear distinction can be made between interpretations using bony landmarks, as the true watershed line is defined and definitions using soft tissue landmarks, which might represent the reference points surgeons use in clinical practice.

The Watershed Line of the Distal Radius: Cadaveric and Imaging Study of Anatomical Landmarks

Background  Placement of volar plates remains a challenge as the watershed line may not be an easy-identifiable distinct line intraoperatively. Objectives  The main objective of this article is to define how anatomical landmarks identifiable upon the volar surgical approach to the distal radius relate to the watershed line. Methods  We identified anatomical landmarks macroscopically upon standard volar approach to the distal radius in 10 cadaveric forearms and marked these with radiostereometric analysis (RSA) beads in cadaveric wrists. The RSA beads were then referenced against the volar osseous structures using quantification of three-dimensional computed tomography and advanced imaging software. Results  The mean measurements were the radial and ulnar prominences 11.1 mm and 2.1 mm proximal to the joint line of the distal radius, respectively. The interfossa sulcus was 0.3 mm proximal and 3 mm dorsal to the ulnar prominence. The watershed line was between 3.5 (minimal) and 7.6 (maximal) mm distal to the distal line of insertion of the pronator quadratus. Conclusion  The watershed line is situated distal to the pronator quadratus, but with a wide variability making it an impractical landmark for plate position. The osseous ulnar prominence is a good anatomical reference for safe plate positioning, as it is located on the watershed line and easily palpated at surgery. One should keep in mind the sulcus-the point on the watershed line where the flexor pollicis longus runs-can be situated just proximal to the ulnar prominence. Clinical Relevance  To provide anatomical landmarks that are easy to identify upon surgical approach without the direct need for intraoperative imaging.

Utility of an image fusion system for 3D preoperative planning and fluoroscopy in the osteosynthesis of distal radius fractures

Background

Recently, computerized virtual surgery planning has been increasingly applied in various orthopedic procedures. In this study, we developed an image fusion system for 3D preoperative planning and fluoroscopy for the osteosynthesis. To assess the utility of image fusion system, we evaluated the reproducibility of preoperative planning in the osteosynthesis of distal radius fractures with using the image fusion system, and compared with the reproducibility of the patients without using the image fusion system.

Methods

Forty-two wrists of 42 distal radius fracture patients who underwent osteosynthesis using volar locking plates were evaluated. The patients were divided into two groups. Image fusion group utilized three-dimensional (3D) preoperative planning and image fusion system. Control group utilized only 3D preoperative planning. In both groups, 3D preoperative planning was performed in order to determine reduction, placement, and choice of implants. In the image fusion group, the outline of planned image was displayed on a monitor overlapping with fluoroscopy images during surgery. Reductions were evaluated by volar tilt and radial inclination of 3D images. Plate positions were evaluated with distance to joint surface, plate center axis position, and inclination relative to the radius axis. Screw choices were recorded for the plan and actual choices for each screw hole. Differences in the parameters between pre- and postoperative images were evaluated. Differences in reduction shape, plate positions, and screw choices were compared between groups.

Results

The differences in the distance from plate to joint surface were significantly smaller in the image fusion group compared to the control group (P < 0.01). The differences in the distal screw choices were significantly smaller in the image fusion group compared to the control group (P < 0.01).

Conclusions

The image fusion system was useful to reproduce the planned plate position and distal screw choices in the osteosynthesis of distal radius fractures.

Trial registration

ClinicalTrials.gov, NCT03764501