Muscle co-activation is the simultaneous activation of agonist and antagonist muscles that produces forces around a joint to provide joint stability. To determine if the use of a wrist-driven, 3D-printed transitional prosthesis influenced the neuromuscular motor control strategies of the affected hand of children with unilateral upper-limb reduction deficiencies, researchers examined the co-activation index (CI) before and after six months of the children’s use of such a prosthesis. The study concluded that the affected hand had a higher coactivation index for flexion and extension than the non-affected hand. Wrist flexion indicated that the affected and non-affected hand had a significantly lower co-activation index after six months.
Inclusion criteria for the participants was unilateral carpus upper-limb reductions, missing some or all fingers, and wrist range of motion of the affected wrist greater than 20 degrees. Nine children (two girls and seven boys, six to 16 years of age) were fitted with a wrist-driven, 3D-printed prosthetic hand. From the nine children, five (two girls and three boys, 7 to 10 years of age) completed a second visit after using the prosthesis for six months.
Researchers collected data from the EMG activity of wrist flexors and extensors (flexor carpi ulnaris and extensor digitorum) recorded during maximal voluntary contraction of the affected and non-affected wrists. Co-contraction was calculated using the CI and was expressed as percent activation of antagonist over agonist.
To determine the results, separate, two-way, repeated measure analysis of variances (ANOVAs) were performed to analyze the co-activation index and strength data of the participants. The findings showed that the affected hand of children with unilateral upper-limb reductions had a significantly higher co-activation index for wrist flexion and extension at baseline. Furthermore, the use of a wrist-driven (by flexion) 3D-printed hand prosthesis lowered the co-activation index during wrist flexion by 70 percent compared to a 30 percent reduction for the non-affected hand, which the researchers believe has the potential to improve prosthetic rehabilitation outcomes.
The open-access study was published June 8 in the Journal of NeuroEngineering and Rehabilitation.
