In Vivo Assessment of Conjoint Tendon Spatial Relationships in Healthy and Reverse Shoulder Arthroplasty Shoulders Using Three-Dimensional Ultrasound

Le, Marie Huynh Phuong Nhi

In Vivo Assessment of Conjoint Tendon Spatial Relationships in Healthy and Reverse Shoulder Arthroplasty Shoulders Using Three-Dimensional Ultrasound

Files

Le_Marie_MESc_2026_thesis.pdf (5.81 MB)

Date

2026-05-26

Authors

Le, Marie Huynh Phuong Nhi

Abstract

Reverse total shoulder arthroplasty is a common surgical procedure used to treat complex shoulder pathologies by reversing the ball-and-socket anatomy to restore native biomechanics. However, postoperatively, anterior shoulder pain can occur. A potential etiology is conjoint tendon impingement. Conjoint tendon impingement across functionally relevant positions and rotations has not been well established in vivo. Therefore, this thesis aims to determine a healthy normative range across varying elevations and rotational positions to enable comparison of conjoint tendon clearance and impingement risk in RSA patients. Using three-dimensional ultrasound, the study demonstrated that shoulder rotation significantly affects conjoint tendon clearance in a healthy population. In contrast, patients tended to exhibit reduced clearance, with some demonstrating contact between the tendon and the humerus or implant component.

Summary for Lay Audience

Reverse shoulder arthroplasty (RSA) is a type of shoulder replacement surgery used to restore arm function in people with severe shoulder damage, often due to rotator cuff tears, arthritis, or previous failed shoulder surgery. Although RSA can improve movement and quality of life, some patients continue to experience pain at the front of the shoulder following surgery. A possible cause of the pain is compression or impingement of the conjoint tendon, a tendon that runs along of the front of the shoulder, as it moves close to nearby bones during specific arm positions. Currently, it is not well established how the conjoint tendon moves, where it is located spatially in healthy shoulders, or how these characteristics change after RSA. It is also unclear which arm positions may reduce the space between adjacent bones and, thus, the space between the tendon and the bone. This reduction in space may place the tendon at risk for compression. This thesis aimed to develop a method using three-dimensional ultrasound to quantify the anatomical relationships among the conjoint tendon, coracoid process, and humerus in living participants during functional shoulder positions that mimic real-life conditions. In this study, healthy participants and RSA patients were scanned using three-dimensional ultrasound while their arms were placed in different positions, including elevation, rotation, and behind-the-back positions and different rotations (internal and external). From these images, measures of the coracohumeral distance and the distance between the conjoint tendon and humerus were taken. The findings demonstrated that internal rotation generally reduced these distances, suggesting there is a rotational influence on tendon-to-bone proximity. RSA patients also tended to have smaller distances than healthy participants, but not all patients with reduced space had symptoms of pain/ impingement. Overall, this thesis developed a protocol for imaging and assessing anterior shoulder anatomy using three-dimensional ultrasound. These findings provide the foundation for understanding how the compression of the conjoint tendon may contribute to anterior shoulder pain following RSA. This work may support future work aimed at improving surgical planning as well as patient-specific assessment and monitoring following replacement surgery.

Keywords

Reverse Shoulder Arthroplasty, Three-Dimensional Ultrasound (3D US), Conjoint Tendon, Shoulder Impingement, Internal Rotation, Musculoskeletal Imaging, Glenohumeral Joint, Subcoracoid Distance, Coracohumeral Distance, Implant, Musculoskeletal Disorders