Physiologic Long Head Biceps Tendon Excursion Throughout Shoulder Range of Motion: A Cadaveric Study

Abstract

Background: Restoration of the long head of the biceps tendon (LHBT) length-tension relationship is critical in preserving muscle strength and efficiency when performing biceps tenodesis. While static anatomic landmarks such as the inferior border of the pectoralis major may be used intraoperatively to achieve this, shoulder position may affect the excursion of the biceps tendon and represents another variable to consider. Purpose/Hypothesis: The purpose of this study was to quantitatively evaluate the normal excursion of LHBT that occurs through a glenohumeral range of motion. We also sought to determine whether elbow position affects LHBT excursion. We hypothesized that LHBT excursion will be affected by glenohumeral flexion and extension, and elbow extension will result in increased excursion at each glenohumeral position compared with a neutral position. Study Design: Controlled laboratory study. Methods: A total of 10 fresh-frozen specimens underwent a standard approach for subpectoral biceps tenodesis. The LHBT was identified and tagged with a radiopaque marker within zone 3 of the bicipital tunnel. A total of 3 K-wires were then drilled into the osseous floor: one at the level of the marker in the LHBT, one at 1 cm proximal, and a third 1 cm distal. All 3 K-wires were then cut flush with the anterior humeral cortex. The specimens were next placed into 8 different positions, and the excursion of the LHBT was measured by referencing the K-wires using static fluoroscopic imaging. The results were analyzed using 1-way analysis of variance testing followed by Tukey honestly significant difference testing for pairwise comparison between each individual position and the reference position. Results: The average total LHBT excursion was 24.4 ± 5.2 mm between the neutral shoulder position and the other shoulder positions tested. The position of the LHBT was significantly different in the reference position compared with each of the other 7 shoulder positions ( P < .001). Additionally, the 2 positions of shoulder extension had different LHBT excursions when compared with each position of shoulder flexion ( P < .0001). For each shoulder position tested, the position of the LHBT was not significantly different in elbow flexion compared with extension. Conclusion: There is approximately 24 mm of LHBT excursion throughout the glenohumeral range of motion, with significantly different amounts of excursion in glenohumeral flexion and extension. Elbow position does not significantly affect LHBT excursion. Positioning the shoulder in extension during biceps tenodesis may overtension the biceps, while positioning the shoulder in flexion may undertension the biceps relative to the neutral position. Further research is needed to identify the optimal shoulder position for biceps tenodesis. Clinical Relevance: Shoulder positioning is an important consideration in establishing a normal length-tension relationship during biceps tenodesis. When compared with flexed shoulder positions, LHBT excursion significantly differs in positions of extension and in a neutral position.