Objectives: Radiologic criteria for syndesmosis instability evaluation remain controversial and direct visualization (DV) of the distal tibiofibular articulation is an alternative diagnostic method worthy of further investigation. We speculate that DV is a more accurate way to evaluate syndesmosis instability than fluoroscopy. The purpose of this study is to determine whether syndesmosis instability can accurately be recognized through DV and if this new intraoperative diagnostic method is more sensitive than fluoroscopy in detecting syndesmosis instability. Methods: Ten cadaveric ankles were tested using a sequential iatrogenic syndesmosis injury model. Specimens were tested incrementally with the lateral stress test (LST) and the external rotation stress test (ERT). The resulting instability was measured directly and fluoroscopically with a true mortise view by using medial clear space (MCS) and tibiofibular clear space (TFCS). Results: DV detected a 2-ligaments injury at a mean diastasis of 3.02 mm ( P = 0.0077) and 3.19 mm ( P = 0.0077) with the LST and ERT, respectively. Fluoroscopically, TFCS showed a significant diastasis only with a complete syndesmosis rupture while MCS did not show any significant differences. Conclusions: DV of the syndesmosis in a cadaver injury model appears to be more sensitive than fluoroscopy in identifying injury, especially incomplete syndesmotic disruption.

Objectives: We hypothesize that a single syndesmotic view, capturing both sagittal and coronal tibiofibular displacement, will be more sensitive than a mortise view to detect syndesmotic instability. Methods: Ten fresh frozen human lower limbs were used to test the new syndesmotic view with simulated syndesmosis injury. The anteroinferior tibiofibular ligament, interosseous membrane, and posteroinferior tibiofibular ligament were sectioned sequentially. At each stage, the syndesmosis was tested using the external rotation stress (ERS) test and lateral stress test (LST). For each stress condition, a true mortise view and the new syndesmotic view were performed. Medial clear space and tibiofibular clear space (TFCS) were measured on a mortise view, and TFCS was measured on a syndesmotic view (TFCS-s). Wilcoxon signed-rank tests were used to compare measurements. Results: Syndesmotic view enabled instability detection with a 2-ligament dissection at a mean increase in TFCS-s of 2.37 mm (P = 0.021) and 1.98 mm (P = 0.011), using the ERS and LST, respectively. TFCS on the mortise view was significantly different only with a complete injury. Medial clear space did not vary significantly with injury increments. Sensitivity was 66% and 61% using ERS and LST, respectively, for the TFCS-s, compared with 27% and 33%, respectively, for the TFCS. Specificity was similar for TFCS and TFCS-s. Conclusions: This study was able to demonstrate that the syndesmotic view is more sensitive than the mortise view in detecting syndesmotic instability in a cadaveric model. It is particularly helpful to uncover instability secondary to an incomplete syndesmosis injury requiring fixation.

Background: In this cadaveric study, a new “torque test” (TT) stressing the fibula posterolaterally under direct visualization was compared with the classical external rotation stress test (ERT) and lateral stress test (LST). Methods: The anteroinferior tibiofibular ligament (AiTFL), the interosseous membrane (IOM), and the posteroinferior tibiofibular ligament (PiTFL) were sectioned sequentially on 10 fresh-frozen human ankles. At each stage of dissection, instability was assessed using the LST, ERT, and TT under direct visualization. Anatomical tibiofibular diastasis measurements were taken directly on cadavers and compared using the Wilcoxon signed rank test. Results: All 3 tests showed statistically significant motion in the syndesmosis when at least 2 ligaments were sectioned. The mean increase across diastasis with a 2-ligament section was 3.0 mm ( P = .005), 3.2 mm ( P = .005), and 4.8 mm ( P = .005) for the LST, ERT, and TT, respectively. The largest mean increase in diastasis was obtained with a complete injury using the TT and was 6.2 mm ( P = .008). With the TT, a 3.5-mm tibiofibular diastasis was 90% sensitive and 100% specific when 2 or more syndesmotic ligaments were sectioned. Conclusion: The TT was a more sensitive and specific tool for detecting syndesmosis instability than classic LST and ERT. Clinical relevance: Stressing the fibula in a posterolateral direction created a larger distal tibiofibular diastasis, which would be easier to detect in the intraoperative setting. The TT was more sensitive and specific to detecting a 2-ligament syndesmotic injury than the classic test and required less force to perform.

Level III, comparative study.