Abstract / Summary
Objectives: Ankle fractures can cause long-term gait dysfunction, even after surgical treatment. Reduced ankle plantar flexion strength has been implicated; however, the role of soleus muscle architecture in walking speed reserve (WSR), an indicator of mobility in daily life, remains unclear. This study aimed to investigate the association between ultrasound-derived architectural properties of the soleus and WSR in patients after ankle fracture surgery. Material and Methods: This cross-sectional observational study included patients who underwent open reduction and internal fixation of ankle fractures and participated in a standardized postoperative rehabilitation program. Three months after surgery, soleus muscle architecture, including muscle thickness (MT), pennation angle, shear modulus, and echo intensity (EI), was measured using musculoskeletal ultrasonography. Ankle range of motion, plantar flexion strength, WSR, and pain during walking were also assessed. Multiple regression analyses were conducted to examine factors associated with WSR. Results: Forty-five participants (mean age, 47.0 ± 21.4 years) were included. Increased fat-corrected EI (β = −0.336, 95% CI, −0.572 to −0.100; p = 0.006), decreased physiological MT (β = 0.529, 95% CI, 0.293 to 0.764; p < 0.001), and ankle plantar flexion strength (β = 0.429, 95% CI, 0.173 to 0.686; p = 0.002) were independently associated with decreased WSR. The multiple regression model had an adjusted R 2 of 0.525. Conclusion: Physiological MT and corrected EI of the soleus were independently associated with WSR after ankle fracture surgery. These findings suggest that the structural properties of the soleus are associated with WSR in the early postoperative period. Because of the cross-sectional design and assessment at a single postoperative time point, causal relationships cannot be determined.