The greater tuberosity is a rounded bony projection on the upper humerus, the long bone of the upper arm. It serves as an attachment site for muscles important for the shoulder’s wide range of motion and stability. Understanding this feature helps comprehend shoulder function and how injuries can impact movement.
Anatomical Features and Location
The greater tuberosity is a prominent, rounded area on the lateral humerus, just below the humeral head and superior to the surgical neck. It is the most lateral bony point of the humerus and can often be felt on the outer side of the shoulder. This structure is distinguishable from the lesser tuberosity, a smaller, more medially located projection.
Its superior aspect features three flattened impressions or facets: superior, middle, and inferior. Inferiorly, the greater tuberosity forms a ridge known as the crest of the greater tubercle.
Muscles and Their Role
The greater tuberosity anchors three of the four rotator cuff muscles: the supraspinatus, infraspinatus, and teres minor. Each has a specific attachment point on the tuberosity’s facets.
The supraspinatus inserts onto the superior facet, initiating abduction (lifting the arm away from the body).
The infraspinatus attaches to the middle facet. Along with the teres minor, it plays a role in external rotation. The teres minor inserts onto the inferior facet and also assists in adduction (bringing the arm back towards the body).
These muscle attachments are important for the shoulder’s range of motion and stability. Their coordinated action helps keep the humeral head secure within the shoulder socket and allows for powerful, controlled arm movements.
Clinical Significance
The greater tuberosity’s role as an attachment site for rotator cuff tendons makes it clinically relevant. Injuries to this area can impair shoulder function. Tears of the rotator cuff tendons, particularly the supraspinatus, are common and often involve their insertion onto the greater tuberosity. These tears can result from chronic degeneration or acute trauma.
Fractures of the greater tuberosity also occur, often due to direct impact to the shoulder or a fall onto an outstretched arm. Such fractures can happen in isolation or in conjunction with other shoulder injuries, like dislocations. When the tuberosity fractures, the attached rotator cuff muscles can pull the bone fragment out of its normal position, leading to pain and reduced shoulder mobility. The integrity of the greater tuberosity is important for proper shoulder biomechanics and overall upper limb function.