Accuracy of simple plain radiographic signs and measures to diagnose acute scapholunate ligament injuries of the wrist.

Objective: To determine the accuracy of common radiological indices for diagnosing ruptures of the scapholunate (SL) ligament, the most relevant soft tissue injury of the wrist.

Methods: This was a prospective diagnostic accuracy study with independent verification of index test findings by a reference standard (wrist arthroscopy). Bilateral digital radiographs in posteroanterior (pa), lateral and Stecher's projection were evaluated by two independent expert readers. Diagnostic accuracy of radiological signs was expressed as sensitivity, specificity, positive (PPV) and negative (NPV) predictive values with 95 % confidence intervals (CI).

Results: The prevalence of significant acute SL tears (grade ≥ III according to Geissler's classification) was 27/72 (38 %, 95 % CI 26-50 %). The SL distance on Stecher's projection proved the most accurate index to rule the presence of an SL rupture in and out. SL distance on plain pa radiographs, Stecher's projection and the radiolunate angle contributed independently to the final diagnostic model. These three simple indices explained 97 % of the diagnostic variance.

Conclusions: In the era of computed tomography and magnetic resonance imaging, plain radiographs remain a highly sensitive and specific primary tool to triage patients with a suspected SL tear to further diagnostic work-up and surgical care.

Key Points: • Scapholunate ligament (SL) lesions are the most relevant soft tissue wrist injuries. • Missed and untreated SL ruptures can cause painful and disabling post-traumatic wrist osteoarthritis. • Reliable threshold values of radiographic indices should prompt further imaging or surgical care. • Plain radiographs deliver conclusive clinical information if certain hand positions are used.