Diagnosis of Traumatic Ankle Arthrotomies Using Saline Load Tests, Methylene Blue, and Radiopaque Tracer: A Cadaveric Study

Abstract

Background: The objective of this study was to define the volume (mLs) needed for a positive saline load challenge test in anterolateral (AL), anteromedial (AM), posterolateral (PL), or posteromedial (PM) ankle arthrotomy wounds using normal saline (NS) and methylene blue (MB). Another objective was to evaluate the use of fluoroscopy and iodinated contrast in the diagnosis of ankle arthrotomies. Methods: Four cadaveric ankle specimens underwent standardized arthrotomy creation in either the AL, AM, PL, or PM portion of each specimen. An 18-gauge needle was used to inject fluid into each ankle, and the volumes needed for positive fluid challenges were recorded. All 4 ankles were tested 10 times (n = 40) with NS and 10 times using MB (n = 40). A fifth cadaveric ankle was injected with radiopaque contrast solution, and an arthrotomy was simulated and imaged with fluoroscopy.Statistical analyses compared the volumes of NS and MB needed for a positive test. In addition, the 25th, 50th, 75th, 90th, and 95th percentiles of volumes needed for a positive test was calculated. Results: The volume of fluid necessary to detect 25%, 50%, 75%, 90%, and 95% of ankle arthrotomies from any site was 2.0 mL, 4.5 mL, 9.0 mL, 10 mL, and 10 mL, respectively. Anterior arthrotomies required less fluid (2.1 mL ± 0.5) than posterior arthrotomies (9.0 mL ± 1.2) for a positive test ( P < .0001). There was no difference between the amount of NS (5.5 mL ± 3.6) vs MB (5.6 mL ± 3.7) needed for a positive challenge test ( P = .739). Conclusion: Ninety-five percent of ankle arthrotomies could be diagnosed with 10 mL of injected fluid; there was no difference between the volume of NS vs MB needed. Fluoroscopy assisted with needle placement and can be combined with radiopaque contrast solution to diagnose ankle arthrotomies. Clinical Relevance: The findings of this study may improve sensitivity and efficiency in the diagnosis of traumatic ankle arthrotomies, for which there is currently a paucity of literature.