Investigating the thickness of the long head of biceps brachii tendon with the application of heat

Abstract

Background: Subacromial impingement is a common cause of shoulder pain, leading to other injuries such as long head of biceps (LHB) tendinopathy. Excessive compression, caused by reduced acromiohumeral distance or tendon hypertrophy, has been described as the key contributor. Interventions directed at reversing these forces are not well studied. Heat has been reported to reduce pain and improve function in subacromial impingement, however its effects on the structure of the tendon are unclear.

Objectives: This study aimed to investigate the effect of heat on LHB tendon thickness. The main objectives were to determine whether heat may result in changes in tendon thickness and contribute to reducing the overall compression within the subacromial space.

Study Design: An experimental pretest – posttest design was used for this study, which involved the measurement of the tendon, followed by a heat application, and remeasurement.

Methods: 100 healthy participants were included. A diagnostic ultrasound scan was carried out to measure tendon thickness and width of both shoulders. A continuous 3MHz therapeutic ultrasound application at 1.5W/cm2 or 1.0W/cm2 was applied to one shoulder for 8 minutes. A second ultrasound scan was done to re-measure tendon dimensions.

Findings and Results: No significant difference was reported between pretest and posttest measurements for both width and thickness of the 1.5W/cm2 (p = 0.618, p = 0.704) or 1.0W/cm2 (p = 0.410, p = 0.808) groups. Mixed 2-way ANOVA showed that there was no significant difference between the experimental and control groups (p = 0.584, p = 0.230, p = 0.790, p = 0.800) as well as the 1.5W/cm2 and 1.0W/cm2 intensity groups (p = 0.377, p = 0.937). The intra-rater reliability of the sonographer was good to excellent for width (0.84 – 0.91) and thickness (0.80-0.88) measurements.

Conclusion: The findings suggest that an application of heat does not have an effect on LHB tendon thickness and compression within the subacromial space; a 1.0W/cm2 intensity ultrasound produces the same effects as the 1.5W/cm2; and finally, that diagnostic ultrasound is a reliable tool in measuring LHB tendon dimensions.