Morphological risk factors for scaphoid fracture: a case-control study

Purpose Most patients with a clinically suspected scaphoid fracture and normal initial radiograph are unnecessarily treated. Previously developed prediction rules using demographic and clinical risk are unable to accurately predict occult fractures. Adding other risk factors could enhance this. Therefore, we aim to explore if there are morphological risk factors of the wrist for sustaining a scaphoid fracture. Methods We retrospectively included adult patients with a clinically suspected scaphoid fracture between 2013 and 2019 in our case-control study. There were 82 patients with a scaphoid fracture and 158 patients with a wrist contusion. Morphological risk factors were identified using statistical shape modelling (SSM) and linear measurements. Independent wrist shape variations on posteroanterior and lateral radiographs were captured in modes using SSM. Associations between outcomes and a scaphoid fracture were explored using logistic regression and the reliability was assessed. Results Of the 15 posteroanterior modes and 8 lateral modes identified and linear measurements performed, 1 PA mode was associated with a scaphoid fracture (PA mode 4; OR 1.40, CI 1.04-1.93, p = 0.031). We described this mode as an ulna plus and narrower distal radius with more volar tilt and radial inclination. The reliability of the posteroanterior modes and linear measurements was mostly good/excellent and moderate/poor for the lateral modes. Conclusion There was one complex wrist shape significantly associated with a scaphoid fracture. Since the association was weak and the shape is difficult to identify radiographs, we believe this morphological risk factor would not enhance identifying occult scaphoid fractures in the future.