Correlation of strength, mobility and bone mineral density in duchenne muscular dystrophy

Objective: Mobility and muscle strength are known to affect bone mineral density (BMD) in with Duchenne Muscular Dystrophy (DMD). The aim of the present study is to evaluate the association of strength and mobility with BMD in patients DMD. Patients and methods: A total of 33 boys with diagnosis of DMD aged from 6-18 years were grouped as non-ambulatory and ambulatory. Outcome measures were static muscle strength tests (pinch strength, grip strength) and BMD for both of the groups and mobility tests (10 m walk/run, 6 min walking, stair ascend/descend) and dynamic strength tests (60°/s speed, knee flexor/extensor strength) for ambulatory group. Results: 18 non-ambulatory boys from 9-18 years and 15 ambulatory boys from 6 to 13 years participated to the study. In the ambulatory group, there was high positive correlation between grip strength, right and left leg knee flexion peak power and left and right arm and leg, pelvis, and total BMD (p<0.05). In the non-ambulatory group, grip and key pinch strength were identified to be highly positive correlation with right arm BMD (p<0.05). Additionally, there was a positive correlation between the 6-minute walking test and only pelvis and right arm BMD (p<0.05). Conclusion: In this study, the correlation of strength, power and mobility parameters with BMD varied according to anatomic region. Static and dynamic strength and power were found to affect BMD rather than mobility. Therefore, preserving strength and power in DMD patients is also an important factor in maintaining bone health.