Development of Contractures in DMD in Relation to MRI-Determined Muscle Quality and Ambulatory Function

Background: Joint contractures are common in boys and men with Duchenne muscular dystrophy (DMD), and management of contractures is an important part of care. The optimal methods to prevent and treat contractures are controversial, and the natural history of contracture development is understudied in glucocorticoid treated individuals at joints beyond the ankle. Objective: To describe the development of contractures over time in a large cohort of individuals with DMD in relation to ambulatory ability, functional performance, and muscle quality measured using magnetic resonance imaging (MRI) and spectroscopy (MRS). Methods: In this longitudinal study, range of motion (ROM) was measured annually at the hip, knee, and ankle, and at the elbow, forearm, and wrist at a subset of visits. Ambulatory function (10 meter walk/run and 6 minute walk test) and MR-determined muscle quality (transverse relaxation time (T2) and fat fraction) were measured at each visit. Results: In 178 boys with DMD, contracture prevalence and severity increased with age. Among ambulatory participants, more severe contractures (defined as greater loss of ROM) were significantly associated with worse ambulatory function, and across all participants, more severe contractures significantly associated with higher MRI T2 or MRS FF (ρ: 0.40-0.61 in the lower extremity; 0.20-0.47 in the upper extremity). Agonist/antagonist differences in MRI T2 were not strong predictors of ROM. Conclusions: Contracture severity increases with disease progression (increasing age and muscle involvement and decreasing functional ability), but is only moderately predicted by muscle fatty infiltration and MRI T2, suggesting that other changes in the muscle, tendon, or joint contribute meaningfully to contracture formation in DMD.