Intraoperative tap test for coronal syndesmotic instability: A cadaveric study.

Area of Science:

• Orthopedic Surgery
• Diagnostic Imaging
• Biomechanical Testing

Background:

• Diagnosing distal tibiofibular syndesmotic injuries remains challenging, lacking a definitive gold standard test.
• Tibiofibular clear space (TFCS) on radiographs is a key indicator, but intraoperative assessment often relies on the Cotton test, which has limitations.

Purpose of the Study:

• To introduce and evaluate a novel intraoperative test for diagnosing distal tibiofibular syndesmotic injuries using a 3.5 mm blunt cortical tap.
• To compare the accuracy and reliability of this new tap test against established methods in cadaveric specimens.

Main Methods:

• Tibiofibular clear space was measured using fluoroscopic imaging in nine cadaveric specimens under intact and injured (ligamentous release) conditions.
• A 3.5 mm blunt cortical tap was used to apply stress, creating tibiofibular separation, with measurements taken before and during stress application.
• Statistical analysis included one-way ANOVA, paired Student's t-test, and intraclass correlation coefficient (ICC) for intra- and inter-observer reliability.

Main Results:

• The novel tap test demonstrated excellent intra-observer (0.97) and inter-observer (0.98) agreement.
• Significant differences in tibiofibular clear space were observed between intact and injured states (p < .05).
• The tap test achieved 96.3% sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy in diagnosing coronal syndesmotic instability when TFCS > 6 mm.

Conclusions:

• The 3.5 mm blunt cortical tap test is a simple, accurate, and reliable intraoperative method for diagnosing coronal syndesmotic instability.
• This technique provides a more controlled and stable alternative to the conventional Cotton test.
• The study validates the tap test's ability to detect significant differences in tibiofibular clear space indicative of injury.