Assessment of Force Applied During Examination Under Anesthesia Used to Determine Stability in Posterior Wall Acetabular Fractures.

Objectives: Determination of hip instability associated with posterior wall acetabular fractures may be difficult. Thus, dynamic stress examination under anesthesia (EUA) was developed as a tool for guiding treatment. EUA uses positioning of the hip and application of force across the hip to detect instability. While aspects of the EUA technique seems consistently described in the literature and practiced by surgeons, some components are ill-defined. The goal of this study was to assess standardization of applied force during EUA among experienced acetabular surgeons.

Methods: Fellowship-trained orthopaedic trauma surgeons with experience in acetabular fracture treatment performed EUA for posterior wall instability on an intact, fresh human cadaver. All surgeons used a similar method, and each expert performed EUA multiple times separated by a brief hiatus. The maximum force applied along the femur's vector in Newtons (N) was measured using a hand-held digital dynamometer.

Results: The EUAs of 19 surgeons were evaluated. Five surgeons had been practicing for <5 years, six for 6 to 10 years, five for 11 to 20 years, and three for >20 years. The mean force applied during EUA was 173N, with a notable variability between surgeons (range, 77-368N). Notable variability was also observed between sequential measures of individual surgeons with six surgeons (31.6%) having a >50N range on repeat trials.

Conclusion: This is the first study to report force applied during an EUA to assess for posterior wall acetabular fracture stability. Notable variability was observed among surgeons performing the examination and in repeated examinations by the same surgeon, suggesting that results of EUA may be surgeon-dependent. Further study is needed to determine what optimal applied force should be used to assess hip stability after a posterior wall acetabular fracture.

Level of evidence: Level V. An assessment of a diagnostic tool.