Development and evaluation of a passive trunk support system for Duchenne muscular dystrophy patients

Patients with Duchenne muscular dystrophy gradually lose the ability to use different muscles of their body. Consequently, they lose the ability to stabilize their trunk against gravity. This hinders them to effectively perform different daily activities. In this paper, we describe the design, realization and evaluation of a trunk orthosis for these patients that should allow them to move their trunk and maintain stability.

This study aimed to primarily assess the effectiveness of the trunk support system in terms of unloading of trunk muscles, so only healthy participants were recruited for this phase of the study. Measurements were done on 10 healthy participants (23.4±2.07 [M±SD] years old, average body weight 68.42±24.22 [M±SD] kg). The experiment comprised maintaining a constant trunk posture in three different device conditions (control without orthosis and two conditions with different configurations of the orthosis), at four different flexion angles (10°, 20°, 30°, 40°) for each device condition and for two load conditions (with and without stretching the arms). Electromyography (EMG) signals from the trunk muscles were measured to estimate activation levels of the trunk muscles (iliocostalis, longissimus, external oblique and rectus abdominis) and a motion capture system was used to record the movement of the participants during the experiment.

Wearing the orthosis caused reductions in longissimus and iliocostalis activity. The average muscle activity level was 5%-10% of maximum voluntary contraction in the unsupported conditions for those particular muscles. This level was reduced to 3%-9% of maximal voluntary contraction for the supported conditions. No effect on external oblique and rectus abdominis activity was observed. Moreover, no pain or discomfort was reported by any of the participants during the experiment. The results from the current experiment also suggests the necessity of lumber stabilizing systems while using trunk orthosis.

The developed orthosis reduces trunk muscle activation level and provides a solid step for further development of support systems for Duchenne muscular dystrophy patients.

The current study was approved by the medical ethics committee Arnhem-Nijmegen (study number: NL53143.091.15 ), The Netherlands.