(140) What Spatulation Angle Most Optimally Increases Anastomosis Circumference While Maintaining The Flap Length: Width Ratio To &lt; 2:1? Three-Dimensional Modelling Applications for Surgical Spatulation for Urologic Reconstruction
Authors: Mallavarapu S , Sandhu S , Smith S , Garcia M 
Published: February 2024

Abstract

Introduction
Spatulation is a surgical technique used to anastomose tubular structures in urology, including the urethra, ureter, and in transgender surgery, the neovaginal canal-end to a peritoneal pouch. This is critical in restoring normal function with a water-tight repair, and reducing the risk of stricture-formation secondary to post-operative scarring at the site of repair within a tubular structure. Considerations such as the optimization of the length-to-width ratio of the spatulated tube to &lt;2:1 have been described as a means of ensuring adequate blood supply to the distal-most spatulated end, however, no studies to date have evaluated the optimal angle of spatulation to achieve this. We used CAD models to 3-D print tubular structures that would maintain their internal measurements as we conducted our analysis to ascertain the optimal angles of spatulation. (Figure 1a)

Objective
1) To ascertain the optimal angle of spatulation using 3-D tubular structures maintain a 2:1 ratio of length to width for consideration during operative repair of tubular structures.

Methods
Three-dimensional CAD files of hollow, tubular structures were designed and printed with an internal circumference of 110mm. Each of the four models were then cut at 30°, 45°, 60°, and 75° to represent each of the different incision angles (Figure 1b). The inner circumferences and added length of each of the resulting flaps were measured on each CAD models. Using this information, the optimal angle of spatulation was calculated using geometric and mathematical analysis. We used the accepted convention of the 2:1 length to width ratio to ensure sufficient perfusion to the distal-most point of the flap as the limit when calculating the optimal angle of spatulation.

Results
The inner circumferences and added length is shown in Figure 1c. Overall, as expected, increasing the angle of spatulation from 30° to 75° increased the circumference of the anastomotic site and decreased the risk of stricture-formation post-operatively. It was noted that as the angle of spatulation increases, the inner circumference and the length of the resulting flap both increase exponentially. The angle of spatulation corresponding to the widely accepted criterion of 2:1 for the Length-to-Width ratio is 63.4°.

Conclusions
Our findings show that as the angle of spatulation increases, the circumference of the spatulation site increases. However, a competing limit to increasing spatulation-angle is that the spatulated ends become increasingly narrow and far from the source of the blood vessels, which compromises the blood supply to the distal tip-ends. To help ensure adequate perfusion of the spatulated limbs, it is desirable to maintain a Length-to-Width ratio of &lt;2:1. Our work finds that the maximum spatulation angle that maintains Length-to-Width at &lt;2:1 is 63.4 degrees.

Disclosure
No.