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J Orthop Trauma. 2019 May 15. doi: 10.1097/BOT.0000000000001507. [Epub ahead of print]

The Ankle Fracture Stability-Based Classification: A Study of Reproducibility and Clinical Prognostic Ability.

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Department of Orthopaedics and Rehabilitation Larner College of Medicine University of Vermont Burlington, VT.



To compare the reproducibility and prognostic capacity of two commonly used ankle fracture classifications to the Stability-based classification.


One hundred ninety-three consecutive rotational type ankle fractures treated during a year at our institution in patients >18 years old were retrospectively analyzed. Pilon and pathologic fractures were excluded. The fractures were treated by attending physicians who were unaware of the Stability-Based classification system. Three observers classified injury radiographs using the Lauge-Hansen, Weber/AO, and Stability-Based classifications systems. Reproducibility (inter-observer variation) of each classification system was calculated using kappa statistics. Prognostic values were evaluated by calculating the area under the curve (AUC) for the ROC curves (using surgery as the positive outcome).


The Stability-Based and Weber/AO classifications showed better reproducibility (kappa .938 [95% CI .921-.952], kappa .97, [.961-.976], respectively, than the Lauge-Hansen (kappa .74 [.664-.795]; p<.05). The Stability-Based classification was more accurate (p<.001) in predicting surgical treatment (AUC .883, [95% CI .852-.914]) compared to the other 2 classifications (.626, [.576-.675], and .698, [.641-.755], respectively.


The Stability-Based classification was both highly reproducible (kappa .938) and had superior prognostic capacity to identify patients who needed surgical intervention compared to both the Lauge-Hansen and AO/Weber classification systems. Importantly, there were no patients who were classified as stable who failed non-operative treatment. This extends earlier studies by directly demonstrating its prognostic advantage to other classification systems.Level of Evidence - Level I (Diagnostic test - Testing of previously developed diagnostic criteria (consecutive patients with consistently applied reference standard and blinding).

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