The rotator cuff consists of the supraspinatus, infraspinatus, teres minor, and subscapularis muscles and their tendons, which surround and stabilize the shoulder joint. Rotator cuff-related disorders may cause pain, particularly during arm elevation and external rotation, and may limit shoulder movement and daily function.
Shoulder function depends not only on the muscles surrounding the shoulder but also on the coordinated transfer of force through the trunk and extremities, known as the kinetic chain. Impairments in trunk muscle function, core stability, proprioception, and balance may therefore negatively affect shoulder mechanics.
This study aims to investigate the relationships between latissimus dorsi and abdominal muscle thickness, trunk proprioception, and postural stability in individuals with rotator cuff pathology. The study will also examine whether these measurements differ between individuals with rotator cuff pathology and healthy participants.
Willing to participate in the study and able to provide written informed consent
Aged 18 years or older
Unilateral shoulder pain lasting for at least 3 months
Right-hand dominance
Unwilling or unable to provide written informed consent
Younger than 18 years
History of a chronic orthopedic or neurological condition that may affect shoulder, abdominal, or periscapular muscle function
History of injury or surgery involving the abdominal region
Study participants will be selected from adults evaluated at the Physical Medicine and Rehabilitation outpatient clinic of Göztepe Prof. Dr. Süleyman Yalçın City Hospital. The patient group will include right-hand-dominant adults with unilateral shoulder pain lasting at least 3 months and a diagnosis of rotator cuff pathology. The control group will include right-hand-dominant healthy adults without shoulder pain who meet the study eligibility criteria.
Other
Cross-sectional
Not listed
Abdominal Muscle Thicknesses
The thicknesses of the rectus abdominis, external oblique, internal oblique, and transversus abdominis muscles will be measured separately in millimeters using diagnostic ultrasonography. Participants will be assessed in the supine position with a pillow placed under the knees. Lateral abdominal muscle measurements will be performed at the midpoint of a line drawn between the anterior superior iliac spine and the inferior border of the lowest rib at the midaxillary line. Rectus abdominis thickness will be measured immediately above the umbilicus at the thickest visible region of the muscle. Minimal transducer pressure will be applied to avoid compression of the muscle tissue. Each measurement will be repeated three times, and the mean of the three measurements will be used in the analysis.
Latissimus Dorsi Muscle Thickness
Latissimus dorsi muscle thickness will be measured with participants in the prone position, with both upper extremities relaxed and positioned alongside the body and the trunk maintained in a neutral position. The measurement site will be identified at the level of the 10th rib along a line drawn between the midpoint of the axilla and a point located 2 cm medial to the posterior superior iliac spine. The ultrasound transducer will be positioned perpendicular to the 10th rib at this level, and latissimus dorsi muscle thickness will be measured at this site. Minimal transducer pressure will be applied to avoid compression of the muscle tissue. Each measurement will be repeated three times, and the mean of the three measurements will be used in the analysis.
Static Postural Stability
Static postural stability will be assessed using a pedobarographic platform. Participants will stand on the platform under standardized testing conditions, and postural sway parameters recorded by the system will be used to evaluate static balance. Higher postural sway values indicate poorer static postural stability.
Trunk Proprioception
Trunk proprioception will be assessed using a digital inclinometer and the active repositioning method. Participants will sit at the edge of a bed with the feet supported, hips and knees flexed to 90°, and the pelvis stabilized. The inclinometer will be positioned over the T4 spinous process. After three practice trials, participants will perform 30° trunk flexion with their eyes open and maintain the target position for 5 seconds. They will then return to the target position with their eyes closed. The absolute difference between the target and reproduced angles will be recorded in degrees. Three measurements will be performed, and the mean repositioning error will be used in the analysis. Higher values indicate poorer trunk proprioception.
Timed Up and Go Test (TUG)
Functional mobility will be assessed using the Timed Up and Go Test. Participants will be instructed to rise from a chair, walk a distance of 3 meters at a comfortable pace, turn, walk back to the chair, and sit down. The time required to complete the test will be recorded in seconds. A longer completion time indicates poorer functional mobility.
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