Scapholunate interosseous ligament dysfunction as a source of elbow pain syndromes: Possible mechanisms and implications for hand surgeons and therapists

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.

Lateral epicondylalgia: A primary nervous system disorder

Lateral epicondylalgia (LE) is the most common chronic painful condition affecting the elbow in the general population. Although major advances have been accomplished in recent years in the understanding of LE, the underlying physiopathology is still a reason for debate. Differences in clinical presentation and evolution of the symptoms among patients, suggest the need for revisiting the current knowledge about subjacent mechanisms that attempt to explain pain and functional loss. Previous models have suggested that the condition is mainly a degenerative tendinopathy, associated with changes in pain pathways and the motor system. The hypothesis of this work is that LE is the clinical manifestation of a primary nervous system disorder, characterized by an abnormal increase in neuronal activity and a subsequent loss of homeostasis, which secondarily affects the musculoskeletal tissues of the elbow-forearm-hand complex. A new model for LE is presented, supported by an in-deep analysis of basic sciences, epidemiological and clinical studies.