The Modified Squat and Smile Test: Correlation with Fracture Union in Long Bone Fractures of the Lower Limb

Purpose Assessing fracture union remains a significant challenge in low-resource settings, such as those across Sub-Saharan Africa. The original Squat and Smile Test was developed as a potential surrogate measure for lower limb fracture union, aiming to reduce reliance on follow-up radiographs in environments with limited access to imaging. We evaluated the correlation between the (blinded) Modified Squat and Smile Test (MSST) and fracture union following intramedullary nailing of lower limb long bone fractures. Methods We performed a retrospective review of prospectively collected data from the HIV in Orthopaedic Skeletal Trauma (HOST) study. Results A total of 180 patients with recorded MSST data were included in the analysis. There was no significant correlation between the MSST total score, or its individual domains (squat, support, and smile), and radiological evidence of fracture union. However, health-related quality of life measures (EQ-5D and Disability Rating Index (DRI)) showed a significant positive correlation with the total MSST score, as well as with the squat and smile domains (p < 0.05). No significant correlation was found between the support domain and these measures. Conclusion The MSST and its individual domains did not correlate with radiological fracture union following intramedullary nailing of lower limb fractures. However, the test showed significant positive associations with patient-reported outcome measures, suggesting potential utility in assessing functional recovery. Further prospective research is needed to validate the MSST and to explore its role in both clinical assessment and follow-up care in resource-limited settings.