Assessing the risk of re-fracture related to the percentage of partial union in scaphoid waist fractures.

Aims There is ambiguity surrounding the degree of scaphoid union required to safely allow mobilization following scaphoid waist fracture. Premature mobilization could lead to refracture, but late mobilization may cause stiffness and delay return to normal function. This study aims to explore the risk of refracture at different stages of scaphoid waist fracture union in three common fracture patterns, using a novel finite element method. Methods The most common anatomical variant of the scaphoid was modelled from a CT scan of a healthy hand and wrist using 3D Slicer freeware. This model was uploaded into COMSOL Multiphysics software to enable the application of physiological enhancements. Three common waist fracture patterns were produced following the Russe classification. Each fracture had differing stages of healing, ranging from 10% to 90% partial union, with increments of 10% union assessed. A physiological force of 100 N acting on the distal pole was applied, with the risk of refracture assessed using the Von Mises stress. Results Overall, 90% to 30% fracture unions demonstrated a small, gradual increase in the Von Mises stress of all fracture patterns (16.0 MPa to 240.5 MPa). All fracture patterns showed a greater increase in Von Mises stress from 30% to 10% partial union (680.8 MPa to 6,288.6 MPa). Conclusion Previous studies have suggested 25%, 50%, and 75% partial union as sufficient for resuming hand and wrist mobilization. This study shows that 30% union is sufficient to return to normal hand and wrist function in all three fracture patterns. Both 50% and 75% union are unnecessary and increase the risk of post-fracture stiffness. This study has also demonstrated the feasibility of finite element analysis (FEA) in scaphoid waist fracture research. FEA is a sustainable method which does not require the use of finite scaphoid cadavers, hence increasing accessibility into future scaphoid waist fracture-related research.</p

Screenshots of the Urban Mind app interface.

Screenshots of the Urban Mind app interface.</p

Higher mental wellbeing for visiting canals and rivers compared to being anywhere else and being in other green spaces.

Adjusted for age, gender, ethnicity, and level of education. Error bars represent 95% Confidence Intervals.</p

Demographic characteristics of participants.

Demographic characteristics of participants.</p

Technical note.

(DOCX)</p

Associations between visiting canals and rivers and subjective mental wellbeing.

Associations between visiting canals and rivers and subjective mental wellbeing.</p

Interaction effects of age, gender, ethnicity, and having a diagnosed mental illness on the association between visiting canals/rivers versus being anywhere else and mental wellbeing.

Interaction effects of age, gender, ethnicity, and having a diagnosed mental illness on the association between visiting canals/rivers versus being anywhere else and mental wellbeing.</p