Objective Assessment of Syndesmosis Stability Using the Hook Test

Area of Science:

• Orthopedic Surgery
• Biomechanics
• Surgical Assessment

Background:

• The hook test is a common intraoperative method for evaluating syndesmosis stability.
• Current guidelines lack specific force recommendations for the hook test.
• The reliability of the hook test in clinical practice remains uncertain.

Purpose of the Study:

• To investigate the forces applied during the hook test by experienced surgeons.
• To assess the reliability and diagnostic accuracy of the hook test under standardized conditions.
• To determine the influence of applied force and syndesmotic instability on diastasis measurement.

Main Methods:

• Ten experienced surgeons performed hook tests on cadaver models, with forces recorded.
• Standardized hook tests with defined forces (50, 80, 100 N) were conducted on cadaver lower legs with sequential destabilization.
• Syndesmotic diastasis was measured using an optical 3D camera system.

Main Results:

• Surgeons applied a median force of 81 N (Range: 50-145 N), with 82% of tests below 100 N.
• The study found good intra-rater reliability but poor inter-rater reliability.
• Even with maximum instability, diastasis > 2 mm was measured in only 12 of 19 specimens, indicating low sensitivity.

Conclusions:

• The hook test demonstrates significant variability in clinical application.
• Standardized application of the hook test is insufficient to reliably detect relevant syndesmotic injuries.
• The findings suggest limitations in the hook test's ability to accurately diagnose syndesmotic instability intraoperatively.