Diagnostic accuracy of the gravity stress test and clinical signs in cases of isolated supination–external rotation-type lateral malleolar fractures

Abstract

We prospectively assessed the diagnostic accuracy of the gravity stress test and clinical findings to evaluate the stability of the ankle mortise in patients with supination-external rotation-type fractures of the lateral malleolus without widening of the medial clear space. The cohort included 79 patients with a mean age of 44 years (16 to 82). Two surgeons assessed medial tenderness, swelling and ecchymosis and performed the external rotation (ER) stress test (a reference standard). A diagnostic radiographer performed the gravity stress test. For the gravity stress test, the positive likelihood ratio (LR) was 5.80 with a 95% confidence interval (CI) of 2.75 to 12.27, and the negative LR was 0.15 (95% CI 0.07 to 0.35), suggesting a moderate change from the pre-test probability. Medial tenderness, both alone and in combination with swelling and/or ecchymosis, indicated a small change (positive LR, 2.74 to 3.25; negative LR, 0.38 to 0.47), whereas swelling and ecchymosis indicated only minimal changes (positive LR, 1.41 to 1.65; negative LR, 0.38 to 0.47). In conclusion, when gravity stress test results are in agreement with clinical findings, the result is likely to predict stability of the ankle mortise with an accuracy equivalent to ER stress test results. When clinical examination suggests a medial-side injury, however, the gravity stress test may give a false negative result.

Dynamic Stress Testing Is Unnecessary for Unimalleolar Supination-External Rotation Ankle Fractures with Minimal Fracture Displacement on Lateral Radiographs

“…Previously, an analysis of standard, non-stress radiographs alone was considered insufficient to determine the stability of the ankle mortise in patients with this type of isolated SER fracture (10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22). We also found that female sex and only two fracture fragments were independent factors for predicting ankle mortise stability.…”

“…However, due to its moderate reliability, the MRI offers limited value to clinical decisionmaking (15). Alternatively, manual external-rotation (ER) stress radiographs (10)(11)(12)(13)(14)(15)(16)(17)(18)(19), gravity stress tests (16)(17)(18)(19), or weight-bearing radiographs (20)(21)(22) have been used to quantify possible dynamic instability. Computer tomography (CT) has mainly been used in research settings (23,24).…”

“…There is no "gold standard" method for evaluating the stability of the ankle mortise; however, external-rotation (ER) stress radiographs have been studied most extensively (6,7,(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21). ER stress testing typically requires clinicians with surgical experience (19), and weight-bearing radiographs may not be possible initially, due to pain.…”

“…ER stress testing typically requires clinicians with surgical experience (19), and weight-bearing radiographs may not be possible initially, due to pain. Therefore, an early control visit is often needed (20)(21)(22).…”

“…Stress test examinations are costly, increase exposure to radiation, and may cause pain to patients (19). Therefore, a less intensive diagnostic protocol would be beneficial.…”