Anatomical Variants of Lister's Tubercle: A New Morphological Classification Based on Magnetic Resonance Imaging

OBJECTIVE: Lister's tubercle is used as a standard anatomical landmark in hand surgery and arthroscopy procedures. In this study, we aimed to evaluate and propose a classification for anatomical variants of Lister's tubercle. MATERIALS AND METHODS: Between September 2011 and July 2014, 360 MRI examinations for wrists performed using 1.5T scanners in a single institution were retrospectively evaluated. The prevalence of anatomical variants of Lister's tubercle based on the heights and morphology of its radial and ulnar peaks was assessed. These were classified into three distinct types: radial peak larger than ulnar peak (Type 1), similar radial and ulnar peaks (Type 2) and ulnar peak larger than radial peak (Type 3). Each type was further divided into 2 subtypes (A and B) based on the morphology of the peaks. RESULTS: The proportions of Type 1, Type 2, and Type 3 variants in the study population were 69.2, 21.4, and 9.5%, respectively. For the subtypes, the Type 1A variant was the most common (41.4%) and conformed to the classical appearance of Lister's tubercle; whereas, Type 3A and 3B variants were rare configurations (6.4% and 3.1%, respectively) wherein the extensor pollicis longus tendon coursed along the radial aspect of Lister's tubercle. CONCLUSION: Anatomical variations of Lister's tubercle have potential clinical implications for certain pathological conditions and pre-procedural planning. The proposed classification system facilitates a better understanding of these anatomical variations and easier identification of at-risk and rare variants.

Clinics in diagnostic imaging (165). Oesophageal rupture secondary to malposition of an SB tube gastric balloon

Oesophageal rupture is a life-threatening complication of balloon tamponade for bleeding oesophageal varices. We herein describe the clinical course and imaging findings in a 33-year-old Indian man who had a Sengstaken-Blakemore (SB) tube inserted for uncontrolled haematemesis, which was unfortunately complicated by malposition of the gastric balloon with resultant oesophageal rupture. The inflated SB tube gastric balloon was visualised within the right hemithorax on chest radiography after the SB tube insertion. Further evaluation of the thorax on computed tomography confirmed the diagnosis of oesophageal rupture associated with right-sided haemopneumothorax. It is crucial for both the referring clinician and reporting radiologist to recognise early the imaging features of an incorrectly positioned SB tube gastric balloon, so as to ensure prompt intervention and a reduction in patient morbidity and mortality.