A systematic review and meta-analysis on the value of the external rotation stress test under fluoroscopy to detect syndesmotic injuries

Standardized analysis of syndesmosis stability in ankle trauma with an innovative syndesmosis-test-tool: a biomechanical study

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 (STT) 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 conditions and 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 STT 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 significantly better for the developed STT. 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, the newly developed STT was superior to the commonly used HT to detect instability.

A systematic review of studies on the diagnostics and classification system used in surgically treated, acute, isolated, unstable syndesmotic injury: a plea for uniform definition of syndesmotic injuries

Objective

To this day, diagnostic standards and uniform definition for acute, isolated syndesmotic injuries are missing. The aim of the current study was to conduct a systematic review of the classification systems and diagnostics currently applied and to propose a best evidence diagnostic approach.

Methods

Medline (PubMed), Scopus, Cochrane Central Register of Controlled Trials, and Embase were searched from inception to June 5, 2022, for studies reporting the outcome of surgically treated acute, isolated syndesmotic injuries. First, all classifications used in the eligible studies were identified and illustrated according to the individual syndesmotic structures injured. Second, the indication for surgery and stabilization, based on the diagnostics applied and the time point assessed (pre- or intra-operatively), was analyzed, including the applied cutoff criteria.

Results

Ten out of 4190 studies, comprising 317 acute ligamentous syndesmotic injuries, met the inclusion criteria. Seven studies facilitated one of the three different classification systems (Calder, West Point, or Sikka classification). Eight studies based their indication for surgery on a combination of clinical and radiographic examinations and two on radiographs only. The most applied clinical tests were the external rotation stress test and squeeze test. The most common radiologic diagnostics were plain radiographs and MRI. Intraoperatively, instability was verified most commonly using arthroscopy.

Conclusion

Current classifications and diagnostics for syndesmotic injuries are heterogeneous, often cannot be attributed to the ligaments injured. An evidence-based diagnostic algorithm based on noninvasive diagnostics and an anatomy-based classification for acute syndesmotic instability is presented.

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.

Physical Examination of Ankle Sprain and Ankle Instability: Can We Really Divide It into Low and High Ankle Sprains?

Lateral ankle ligament sprains and syndesmotic injuries are two different entities. However, they may be combined under the same spectrum depending on the arch of violence during the injury. Currently, the clinical examination has a limited value in the differential diagnosis between an acute anterior talofibular ligament rupture and a syndesmotic high ankle sprain. However, its use is indispensable for raising a high index of suspicion for detecting these injuries. Based on the mechanism of injury, clinical examination plays an essential role in guiding further imaging and early diagnosis of low/high ankle instability.