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Lunate type correlation to scaphoid fracture displacement - wrist size matters
Shai Luria, MD
1, Gili Daniel, MD
2, Ido Volk, MD
1, Hila Meiri, MD
3, Alona Katzir, MD
2, Amir Arami, MD
3; Simon Roner, MD
4(1)Orthropaedic Surgery, Hadassah-Hebrew University Medical Center, Jerusalem, Israel, (2)Hadassah-Hebrew University MC, Jerusalem, Israel, (3)Sheba MC, Ramat Gan, Israel, (4)Zurich University Hospital, Zurich, Switzerland
BackgroundThe surgical fixation of scaphoid fractures is dependent to a great extent on the physician's evaluation of fracture stability. A diagnosis of an unstable fracture is often based on limited evidence. The morphology of the lunate in the midcarpal joint is known to affect joint range of motion, load distribution, and the development of degenerative changes after injury. This study was designed to assess whether lunate morphology affects the stability of acute scaphoid fractures as revealed by fracture displacement.
MethodsThe radiology archives of two large tertiary hospitals were searched from 2010 to 2020 for CT scans of isolated acute scaphoid fractures in adults. The shortest distance between the triquetrum and capitate (T-C) was measured on the coronal reconstructions of these scans. A T-C distance of over 4 mm was considered a lunate type 2 morphology of the midcarpal joint. The ratio between T-C distance and capitate central length (T-C to CCL ratio) was used in order to control for wrist size. Displacement of the scaphoid fracture was defined as a gap or a step-off exceeding 1 mm in any of the CT scan planes. The fracture group measurements were compared to a control group composed of patients with acute wrist injuries but no diagnosed pathology on their CT scans.
ResultsScans of acute scaphoid fractures in 147 patients were compared to 87 injured wrists with no diagnosed pathology. A higher rate of type 2 lunate joints was found in the fracture group (66%) than in the control group (47%; p< 0.005), but when control for wrist size, the difference in ratio was insignificant. In contrast, fracture displacements were found more frequently in type 1 joints (36% vs. 21% in type 2 joints; p = 0.044), again, insignificant when controlled for wrist size. There were more females in the control group (37% vs. 12% in the fracture group; p<0.0001) and a longer capitate size in the fracture group (p=0.002). There was no correlation between displacement or lunate type with time from trauma to CT evaluation.
ConclusionsAlthough examination of the T-C distance may suggest an association between lunate types, midcarpal morphology and fracture displacement, correcting this distance according to wrist size, reveals the limited significance of these findings and questions previous studies which did not consider sex or wrist size. From these results, we cannot conclude that the midcarpal joint morphology effects scaphoid fracture stability or displacement.
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