Intraoperative tap test for coronal syndesmotic instability: A cadaveric study

Stress Tests for Deltoid Ligament and Syndesmosis Injury in Patients With Ankle Fracture: A Systemic Review With Meta-Analysis

OBJECTIVES

To determine the diagnostic accuracy of various stress tests for deltoid ligament and syndesmosis injury in patients with ankle fracture.

DATA SOURCES

A systemic literature search was conducted in the MEDLINE, Embase, and Cochrane Library databases to identify studies published from January 1990 to August 2022.

STUDY SELECTION

Studies that evaluated external rotation or gravity stress tests or hook or tap tests for the diagnosis of deltoid ligament or syndesmosis injury were included.

DATA EXTRACTION

Authors, publication years, study design, index tests, reference standards, demographic features of participants, reliability, and the numbers of true-positive, true-negative, false-positive, and false-negative subjects were extracted from 14 included studies. Article quality was assessed through the revised Quality Assessment of Diagnostic Accuracy Studies tool.

DATA SYNTHESIS

The pooled sensitivity and specificity of each index test for each structure were calculated with a random-effects model using the extracted data of true-positive, true-negative, false-positive, and false-negative outcomes in all relevant studies. The overall diagnostic performance of the different index tests for different structures was determined with the estimation of the area under the curve using the summary receiver operating characteristics curve.

CONCLUSIONS

The gravity stress test and the tap test exhibited high sensitivity and specificity in diagnosing deltoid ligament injury. The hook test has relatively high accuracy in diagnosing syndesmosis injury. Further studies with large sample sizes are warranted to confirm the results of this review.

LEVEL OF EVIDENCE

Diagnostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Instability of the distal tibiofibular syndesmosis

The distal tibiofibular syndesmosis (DTFS) is more frequently injured than previously thought. Early diagnosis and appropriate treatment is essential to avoid long term complications like chronic instability, early osteoarthritis and residual pain. Management of these injuries require a complete understanding of the anatomy of DTFS, and the role played by the ligaments stabilizing the DTFS and ankle. High index of suspicion, appreciating the areas of focal tenderness and utilizing the provocative maneuvers help in early diagnosis. In pure ligamentous injuries radiographs with stress of weight bearing help to detect subtle instability. If these images are inconclusive, then further imaging with MRI, CT scan, stress examination under anesthesia, and arthroscopic examination facilitate diagnosis. An injury to syndesmosis frequently accompanies rotational fractures and all ankle fractures need to be stressed intra-operatively under fluoroscopy after fixation of the osseous components to detect syndesmotic instability. Non-operative treatment is appropriate for stable injuries. Unstable injuries should be treated operatively. Anatomic reduction of the syndesmosis is critical, and currently both trans-syndesmotic screws and suture button fixation are commonly used for syndesmotic stabilization. Chronic syndesmotic instability (CSI) requires debridement of syndesmosis, restoration of ankle mortise with or without syndesmotic stabilization. Arthrodesis of ankle is used a last resort in the presence of significant ankle arthritis. This article reviews anatomy and biomechanics of the syndesmosis, the mechanism of pure ligamentous injury and injury associated with ankle fractures, clinical, radiological and arthroscopic diagnosis and surgical treatment.

Comparison between cotton test and tap test for the assessment of coronal syndesmotic instability: A cadaveric study

INTRODUCTION

In surgically treated rotational malleolar fractures, residual syndesmotic instability is typically assessed following fixation with the widely used intraoperative Cotton test. However, due to its dynamic nature, there are inconsistencies of the magnitude and direction of the distraction force when attempting to pull the fibula away from the tibia using a bone hook. The novel Tap test advances a cortical tap through a drilled hole in the fibula with a stable, unidirectional distraction force applied to the tibia. The objective of this cadaveric study was to compare the Cotton and Tap tests as diagnostic tools for coronal plane syndesmotic instability.

METHODS

Tibiofibular Clear Space (TFCS) of 10 cadaveric specimens was measured for: intact, non-stressed; intact, stressed; injured, non-stressed; and injured, stressed (Tap and Cotton tests). In injured conditions, the syndesmotic ligamentous complex was sectioned using an anterolateral longitudinal approach. Perfect fluoroscopic Mortise images were acquired for all conditions. Two independent and blinded Orthopaedic Foot and Ankle Surgeons measured TFCS 1 cm proximal to the ankle joint line. Intra and interobserver reliabilities were assessed by Intraclass Correlation Coefficient. Syndesmotic TFCS values for all conditions were compared by paired Wilcoxon. Diagnostic performance of the Cotton and Tap tests was assessed using a relative increase of TFCS > 2 mm when comparing intact stressed and injured stressed conditions. P-values <0.05 were considered significant.

RESULTS

The intraclass correlation coefficient for intraobserver and interobserver reliability was respectively 0.96 and 0.79. TFCS measurements were similar in intact non-stressed, intact stressed (both Cotton and Tap tests) and injured non-stressed conditions, with mean values and 95% Confidence Intervals of: intact non-stressed, 3.5 mm; intact stressed, 3.6 mm (Cotton test) and 4.0 mm (Tap test); injured non-stressed, 3.8 mm. The Cotton test and Tap test had, respectively, 73.3% and 70% sensitivity, 100% and 90% specificity, 86.7% and 80% diagnostic accuracy.

CONCLUSIONS

Our cadaveric study compared the Cotton and Tap tests for detection of coronal plane syndesmotic instability. Both tests demonstrated similar increases in the TFCS measurements in stressed injured conditions when compared to intact non-stressed and stressed conditions, as well as injured non-stressed conditions.

Ankle Fracture with a Complex Injury Mechanism and Misleading Hook Test Result: A Case Report

Ankle fractures and their mechanisms of injury can be complex. We report a case of a patient with an uncertain mechanism of injury and an uncommon combination of lower extremity fractures, which fit the criteria for a Lauge-Hansen classification pronation-external-rotation fracture, Maisonneuve fracture, Wagstaffe fracture, and posterior pilon fracture. Plain radiographs and computed tomography scan revealed Chaput tubercle avulsion fractures, an anterior distal fibular fracture fragment, multiple lateral malleolar fractures, a posterior malleolar fracture fragment with proximal displacement, a die-punch fragment between the posterior malleolar fragment and the tibia, a proximal fibular fracture, and possible ankle syndesmotic diastasis. Intraoperative hook test was negative after fixation of the fractures, so syndesmotic fixation was not performed. At 3-month follow-up, plain radiographs showed obvious syndesmotic diastasis. At 1-year follow-up, symptoms persisted and syndesmotic fusion was recommended but declined by the patient. This case demonstrates that both ankle fractures and their mechanisms of injury can be remarkably complex and confusing, posterior pilon fractures can occur along with pronation-external-rotation ankle fractures, syndesmotic fixation should be considered for all patients with Maisonneuve fractures, reliance on the hook test for surgical management decisions may not always be reliable, and there exists a need for a more accurate and reliable intraoperative test to determine the presence of ankle syndesmotic injury.

Tibiofibular syndesmosis in asymptomatic ankles: initial kinematic analysis using four-dimensional CT

AIM

To evaluate the reliability of ankle syndesmotic measurements and their changes during active motion using four-dimensional computed tomography (4DCT) examination in asymptomatic ankles.

MATERIALS AND METHODS

4DCT was performed on both ankles of patients with signs and symptoms of unilateral ankle instability. Ankles from the asymptomatic side of 10 consecutive patients were included in this analysis. Five ankle syndesmotic measurements were adopted from the available literature and performed by two fellowship-trained foot and ankle surgeons: (1) syndesmotic anterior distance (SAD); (2) syndesmotic posterior distance (SPD); (3) syndesmotic translation (ST); (4) syndesmotic tibiofibular angle (STFA); and (5) ankle tibiofibular angle (ATFA). A Monte Carlo simulation was also performed to obtain exact p-values with 99% confidence intervals.

RESULTS

Excellent interobserver reliability was observed among the two readers for four out of five measurements (intra-class correlation coefficients [ICC]: 0.767-0.995, p<0.001-0.020). The ICC values for SAD were not statistically significant (ICC=0.548 and 0.569 for dorsi and plantarflexion respectively, p=0.1). Among the five measurements, only ST measurements had significant changes during active motion (median [interquartile range] for change: -0.70 mm [-1.6-0.10]; p=0.012). Of the above measurements, only the ST measurements demonstrated a negative linear association with the tibiocalcaneal angle during active motion (beta=-2.5, p=0.04).

CONCLUSIONS

Reliable quantitative kinematic assessment of ankle syndesmosis can be performed using 4DCT examination. Syndesmotic measurements remain unchanged during ankle motion except for the syndesmotic translation, which tends to decrease during plantar flexion.