Alterations in forearm muscle activation patterns after scapholunate interosseous ligament injury: A dynamic electromyography study

Study design: Case control.

Purpose of the study: This study aimed to investigate the alterations seen in the activation patterns of the forearm muscles and to demonstrate the associated functional outcomes, in patients with scapholunate interosseous ligament (SLIL) injury.

Methods: The study involved 15 patients with SLIL injury (instability group) and 11 healthy participants (control group). Both groups were evaluated with regard to their pain, grip strength, and upper extremity functional level (disabilities of the arm, shoulder and hand and patient-rated wrist evaluation questionnaires), and they also underwent a dynamic electromyography analysis of their forearm muscle activity. The activation patterns of the extensor carpi ulnaris (ECU), extensor carpi radialis (ECR), flexor carpi ulnaris, and flexor carpi radialis muscles during wrist extension and flexion were recorded by means of surface electromyography.

Results: In the instability group, the pain severity was higher and the functional level was worse than in the control group (P < .05). Furthermore, during wrist extension, the ECR activity was lower and the ECU activity was higher in the instability group than in the control group (P < .05).

Conclusion: Dynamic stabilization of the wrist, flexor carpi ulnaris, and flexor carpi radialis muscles have been shown to play an active role with ECU and ECR. Increased ECU and decreased ECR activation may pose a potential risk in terms of enhancing the scapholunate gap. We, therefore, propose that appropriate preventive neuromuscular exercise strategies implemented as part of a physiotherapy program for patients with SLIL lesions might increase the contribution of the dynamic stability effect of the relevant muscles.