Morphometry of sigmoid notch: A novel method of shape assessment for clinical practice

Using a novel technique, we assess and describe the distal radioulnar joint (DRUJ) anatomy with reference to sigmoid notch shapes. The purpose of this study was to develop a non-invasive, fast, reliable and reproducible technique for analysing the shapes of sigmoid notch on CT scans.

40 cadaveric wrist specimens exposing the sigmoid notch and 100 normal adult wrist CT scans with end on axial sections showing the sigmoid notch outline were obtained. The shape of the sigmoid notch was assessed on both using the geometric construction method.

Of the 40 cadaveric specimens, 42 % were C-shaped, 33 % were flat,17 % were Ski sloped, and 8 % were S-shaped.Of the 100 wrist CT scans, 48 % were C-shaped sigmoid notch, 17 % were flat, 15 % were ski-sloped, and 20 % were S-shaped shapes.

Our sample population had a higher prevalence of C-shaped sigmoids in both cadaveric and CT-based studies. It is considered the most stable shape because of its increased depth. The DRUJ morphology in our sample population can be inferred to have a stable configuration.

The relationships and measurements demonstrated in this study can be a guide when considering ligament reconstruction for DRUJ instability, managing complex fractures involving the DRUJ and in decision-making for notchplasty, osteotomy and arthroplasty of DRUJ.