Objective assessment of syndesmosis stability with an innovative Syndesmosis-Test-Tool - a biomechanical study

Abstract

Abstract When treating ankle fractures, the question of syndesmosis complex involvement often arises. So far there is no standardized method to reliably detect syndesmosis injuries in the surgical treatment of ankle fractures. For this reason, an intraoperative Syndesmosis-Test-Tool (SST) was developed and compared to the recommended and established Hook-Test (HT). Tests were performed on cadaveric lower legs (n=20) and the diastasis was visualized by 3D camera. Tests were performed at 50, 80, and 100 N in native condition and in four instability levels. Instability was induced from anterior to posterior and the reverse on the opposite side. The impact on diastasis regarding the direction, the force level, the instability level and the device used was checked using a general linear model for repeated measurement. The direction of the induced instability showed no influence on the diastasis during the stability tests. The diastasis measured with the SST increased from 0.5 to 3.0 mm depending on the instability, while the range was lower with the HT (1.1 to 2.3 mm). The results showed that the differentiation between the instability levels was statistically significant better for the developed SST. The last level of maximum instability was significantly better differentiable with the STT compared to the HT. An average visualizable diastasis of more than 2 mm could only be achieved at maximum instability. In conclusion, to detect instability, the newly developed STT was superior to the commonly used HT.