The use and efficacy of intra-operative stress tests in supination-external rotation IV ankle fracture fixation

Direct visualization of the syndesmosis for evaluation of syndesmotic disruption: A cadaveric study

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.

A New and More Sensitive View for the Detection of Syndesmotic Instability

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.

Intraoperative Torque Test to Assess Syndesmosis Instability

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.

Finite element analysis of the influence of anterior talofibular ligament injury on Hook test results

AIM

To determine whether the anterior talofibular ligament injury will influence the Hook test result.

METHOD

A three-dimensional model of the ankle was established based on CT scan of a healthy volunteer and ligament attachment through references; Four groups (A-D) of operating conditions were set up. In group A, the anterior and posterior ligaments of the inferior tibiofibular joint were cut off and the anterior talofibular ligament was kept intact; in group B, all the anterior and posterior tibiofibular ligaments and the anterior talofibular ligament were cut off; in group C, the medial and lateral ligaments of the ankle joint and the inferior tibiofibular ligament were kept intact; in group D, only the talofibular ligament was cut off and other ligaments were kept intact. The proximal end of the model was restrained in all four groups, an outward pulling force of 100N perpendicular to the fibula was applied, and displacement and rotation of the distal end of the fibula in the four groups was observed.

RESULTS

When the inferior tibiofibular joint injury was associated with an anterior talofibular ligament injury, the Hook test indicated about 3.19mm of displacement of the distal end of the fibula, and obvious external rotation occurred due to increased activity of the anterior border of the fibula. In the other groups, a single inferior tibiofibular joint injury or a single anterior talofibular ligament injury did not increase displacement or rotation of the distal end of the fibula.

Current trends in the diagnosis and management of syndesmotic injury

Ideal management of the various presentations of syndesmotic injury remains controversial to this day. High quality evidentiary science on this topic is rare, and numerous existing studies continue to contradict one another. The primary reasons for these discrepancies are that previous studies have failed to (1) properly distinguish between isolated (non-fractured) and non-isolated injuries, (2) accurately define stable from unstable injuries, and (3) sufficiently differentiate between acute and chronic injuries. The purpose of this review is to summarize today's body of literature regarding diagnosis and management of syndesmotic injury and discuss current trends and important future directions to optimize care of this very heterogeneous population.

Technique Tip: Novel Use of a Targeting Drill Guide for Syndesmotic Screw Placement

Ankle fractures are among the most common traumatic injuries encountered by orthopaedic surgeons, but obtaining anatomic syndesmosis fixation can be difficult. Previous authors have described the centroidal axis of the syndesmosis. Our group has developed a novel technique of aligning the tibia and fibula along their anatomic centroidal axis using a targeting guide, which has showed good results in 1 patient at 1-year follow-up.

LEVELS OF EVIDENCE

Level V: Expert opinion.

Predictors of a persistent dislocation after reduction of syndesmotic injuries detected with intraoperative three-dimensional imaging

BACKGROUND

In about 25% of cases, reduction of acute unstable syndesmotic injuries and stabilization with syndesmotic screws leads to an inadequate reduction. Conventional fluoroscopy does not provide reliable information about the reduction outcome. However, use of intraoperative 3D imaging can be more accurate. The purpose of this study was to identify predictors of inadequate reduction so that the need for intra- or postoperative 3D imaging could be assessed. Our hypothesis was that complex injuries of the syndesmosis present a higher risk of malreduction than simpler ankle fractures.

METHODS

From August 2001 to February 2011, 251 unstable syndesmotic injuries were treated from a total of 2286 ankle fractures. In 61 of these cases, malreduction of the fibula into the fibular notch was detected by intraoperative 3D imaging. The influence of all possible concomitant and combination injuries of the ankle joint, surgeon's experience, and potential implant-related effects was analyzed.

RESULTS

Thirty-seven Weber C fractures (60.7%), 13 Maisonneuve fractures (21.3%), 10 Weber B fractures (16.4%), and 1 syndesmotic injury without fracture (1.6%) were included. In 14 cases (23%) there was involvement of the posterior malleolus, in 10 cases of the medial malleolus (16.4%), and in 12 cases both (19.7%). The Weber C fractures included 10 bimalleolar fractures with involvement of the posterior malleolus. In neither this combination nor in any other possible injury configuration was it possible to identify a statistically significant correlation with malreduction of the fibula into the fibular notch. The surgeon's experience or an implant-related effect had no detectable influence either.

CONCLUSION

Based on the factors studied, it is not possible to conclude whether a patient has an increased risk of malreduction. Therefore we still recommend verifying all reduction outcomes by intraoperative 3D imaging or postoperative computed tomography.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.