Lateral epicondylitis : intramuscular blood flow, pressure and metabolism in the ECRB muscle

Sammanfattning: Lateral epicondylitis is classified as an overuse injury and the main symptom is pain from the lateral side of the elbow. There is general agreement that the extensor carpi radialis brevis (ECRB) muscle and its proximal tendon play a central role in the development of lateral epicondylitis. However, the pathophysiology is to a large extent unclear. The aim of the thesis was to investigate the intramuscular blood flow, the muscle metabolism as well as the vascular reactivity and the intramuscular pressure (IMP). Patients having chronic unilateral epicondylitis were investigated, with the unaffected arm serving as a control. Measurements were performed during rest, before and 3 and 12 months after an injection of botulinum toxin type A to cause relaxation of the muscle as well as after muscle contraction and occlusion of blood flow.Initial intramuscular blood flow in the affected ECRB was lower compared with the unaffected muscle and anaerobic metabolism was recorded. The dif­ference in intramuscular blood flow between the affected and the unaffected arm was reduced after injection of botulinum toxin type A and muscle metabolism was aerobic. Perceived pain (VAS-score) was reduced and functional daily activity was improved, evaluated using the instrument Canadian Occupational Performance Measure (COMP) and the Disability of Arm, Shoulder and Hand instrument (DASH). Vascular reactivity during recovery after muscle contraction tended to be faster on the unaffected side than on the affected side. No difference in the post-occlusive reactive hyperaemia response between the affected and the unaffected ECRB was observed. The intramuscular pressure tended to be elevated in affected muscle.In conclusion, decreased microcirculation and an anaerobic metabolism in ECRB may contribute to the symptoms in chronic lateral epicondylitis, which has not previously been showed. The impaired blood flow in the affected arm does not seem to be caused by impaired vascular reactivity but may partly be due to an elevated IMP probably due to an increased tension in the affected ECRB.