Objective Assessment of Syndesmosis Stability Using the Hook Test

The hook test is a widely used intraoperative method for assessing syndesmosis stability. However, there are no recommendations regarding the force required to perform this test. Furthermore, the reliability of the test is unclear. Ten experienced surgeons performed hook tests on a cadaver bone model. The applied forces were recorded in a blinded manner. In addition, standardized hook tests with defined forces (50, 80, and 100 N) were performed on 10 pairs of cadaver lower legs and the syndesmosis was sequentially destabilized. Diastasis of the syndesmosis was recorded using an optical 3D camera system. A median force of 81 N (Range: 50 N-145 N) was applied. A proportion of 82% of the tests showed a force < 100 N. The data showed good intraraterreliability and poor interraterreliability. In the standardized investigation of the hook test on the cadaver bone model, both the force and the instability of the syndesmosis had a significant influence on the syndesmosis diastasis. Nevertheless, even with maximum instability of the syndesmosis, diastasis > 2 mm could only be measured in 12 of the 19 evaluable specimens. The widely used hook test shows a high variability when performed in practice. Even in a standardized manner, the hook test cannot detect a relevant syndesmosis injury.

Automated summary

The hook test is commonly used to assess syndesmosis stability during surgery, but there are no guidelines for the force required or the reliability of the test. In this study, ten experienced surgeons performed hook tests on cadaver bone models, with forces recorded in a blinded manner. Standardized hook tests were also performed on cadaver lower legs, revealing that the force and instability of the syndesmosis significantly influenced syndesmosis diastasis. However, even with maximum instability, only a small percentage of specimens showed significant diastasis (>2 mm). The hook test shows high variability and is not able to detect relevant syndesmosis injuries, even when performed in a standardized manner.