Effectiveness of the Saline Load Test in Diagnosis of Traumatic Ankle Arthrotomies in Varying Arthrotomy Locations

CATEGORY: Ankle, Trauma INTRODUCTION/PURPOSE: The purpose of this study was to investigate the amount of fluid required and the sensitivity of the saline load test to identify an intra-articular arthrotomy of the ankle. Limited prior studies have been conducted in arthroscopic models with proposed volumes ranging from 30 ml to 60 ml. Due to this range it was inferred that volume needed to detect arthrotomy would vary based on site of arthrotomy. Using cadavers without prior ankle trauma or surgeries we aim to assess volume needed to detect ankle arthrotomies at varying arthrotomy locations. METHODS: A cadaveric study was conducted using 20 thawed, fresh-frozen below knee amputations. Cadavers were randomly divided into four groups of five and an ankle arthrotomy was made using a 4 mm trochar at standard ankle portal sites; anteromedial, anterolateral, posteromedial, and posterolateral. To confirm intra-articular location, a scope was inserted for direct visualization. A 18-gauge needle was then inserted into the anteromedial portal, except for the anteromedial arthrotomy where the needle was inserted into the anterolateral portal, and saline mixed with methylene blue was loaded into joint. During the injection, the known arthrotomy site was viewed for extravasation. Amount of saline required to diagnose arthrotomy was recorded. All injections were confirmed as intra-articular by demonstrating methylene blue staining of the anterior joint by open exploration. RESULTS: The saline volume required to achieve extravasation ranged from 3 mL to 11 mL. The median saline volume required to achieve extravasation was 5.3 mL. A total of 8 mL was required to achieve 90% sensitivity, 10 mL for 95% sensitivity and 11 mL for 99% sensitivity. For the anterolateral, anteromedial, posteromedial, and posterolateral arthrotomy sites the median saline volume needed to detect a traumatic arthrotomy was 5.2 ml, 6.2 ml, 5 ml, and 4.8 ml respectively. There was no statistically significant difference in volume needed to detect arthrotomies across all four locations. CONCLUSION: A minimum injection of 10 mL is recommended to identify 95% of traumatic arthrotomies approximately 4 mm in size. Prior studies performed in arthroscopic models with prior ankle pathology may overestimate volume needed to detect arthrotomies. No difference in volume needed to detect extravasation was found across all four arthrotomy locations.