# Comparison of the Isometric Position of the External Elbow Fixator: Self-Centering Versus Traditional Techniques, Postoperative CT Evaluation, and 3D Motion Analysis

## TL;DR

This study compares a new self-centering elbow fixator to traditional ones, finding it easier to use and just as effective in aligning with the elbow's center of rotation.

## Contribution

A self-centering external elbow fixator is introduced, simplifying surgical alignment and reducing the need for precise center-of-rotation pin placement.

## Key findings

- The self-centering fixator achieved average alignment deviations of 2–3° across different views.
- The device's average range of motion was 10–145 degrees, comparable to traditional methods.
- It reduced surgical complexity, operating time, and radiographic exposure.

## Abstract

Background/Objectives: The external hinged elbow fixator is a surgical choice both in the case of simple dislocations and elbow dislocation fractures. The correct positioning with respect to the elbow’s center of rotation is demanding. Authors developed a self-centering external fixator that does not require a pin in the elbow’s center of rotation. The aim of this study was to analyze the margin of error in its positioning. Methods: We subjected 16 patients to a CT-3D study reconstruction using 3D motion software to analyze the divergence angle and offset between the elbow’s center of rotation and that of the external fixator. The results were compared to those published on traditional implants. Results: All elbows were correctly reduced without re-dislocation. The average distance was 2° in relation to the center of rotation in the antero-posterior view, 3° in the cranio-caudal, and 2° in the medio-lateral. The divergence angle was 3.5° (min 0.4°; max 9.3°) and the offset 6.8 mm (min 0.06; max 17.5). The average range of motion was 10–145 (range 0–155). Discussion: The traditional hinged elbow external fixator creates severe complexity for surgeons in the necessary positioning of the elbow axial rod to correctly align the implant. The self-centering device avoids this step, making the procedure faster and easier. Although the alignment is still not perfect, the results are still comparable with traditional devices. Conclusions: The self-centering external fixator allows for correct alignment with the elbow’s center of rotation. It is less invasive and simpler, with a shorter learning curve, faster operating time, and less radiographic exposure.