Computerized Tomography for Diagnosing Traumatic Arthrotomies of the Ankle

Owing to the risk for septic arthritis, traumatic arthrotomies are an urgent surgical problem for the treating orthopaedic surgeon. Traditionally, diagnosis is with the saline load test (SLT), although in the awake patient is an invasive and potentially painful procedure. While computerized tomography (CT) has been shown to be a reliable diagnostic tool for traumatic arthrotomies of other joints, its role has only recently been investigated in the setting of ankle arthrotomy.

Eight fresh-frozen mid-tibia ankle cadaveric specimens were included for study. Baseline CT scans were performed to confirm intact ankle joint capsules with absence of intra-articular air. Ankle arthrotomies were performed under fluoroscopic guidance with vertical 1 cm incisions made at the anteromedial or anterolateral portals. After arthrotomy, all ankles underwent a second CT scan, and images were evaluated for the presence of intra-articular air. Finally, SLT was performed and the volume of saline required for extravasation was recorded.

Of 8 ankles, 100% (n = 8) demonstrated intra-articular air on CT scan following arthrotomy. Computerized tomography scan and SLT both demonstrated 100% sensitivity and specificity for diagnosing ankle arthrotomies. Average saline volume necessary for extravasation (and positive SLT) was 4 mL (range: 2-7 mL) and did not differ by foot position.

In this small cadaveric study, CT scan and SLT were both able to detect 100% (n = 8) of traumatic ankle arthrotomies with 100% sensitivity and specificity. Further comparative study of CT scan and SLT for detection of traumatic ankle arthrotomy in a clinical setting is warranted.

Level IV.