Magnetic Resonance Imaging of the Shoulder
There are many causes of a painful shoulder. Rotator cuff tears (tendon tears), labral tears, and biceps injuries are common shoulder problems that are seen by our orthopedic doctors. Magnetic resonance imaging may be recommended during your office visit in order to further evaluate your shoulder.
Rotator Cuff Tears
The shoulder joint resembles a ball and socket. The ball (humeral head) is the uppermost portion of the humerus bone (the long bone of the upper arm). The socket (or glenoid) is a part of the shoulder blade. The ball is able to move with the help of various muscles of the shoulder, especially the rotator cuff muscles. The rotator cuff consists of four muscles that arise from the shoulder blade (scapula), and finally attach to the humeral head (ball). The muscle is generally dark as it starts on the shoulder blade. As it travels toward the ball it turns into tendon and becomes dark black. The thick, dark tendon then attaches to the bone of the humeral head (ball).
The rotator cuff is usually injured near its attachment to the ball. This may occur with normal aging ("wear-and-tear"), or may occur following a traumatic event such as a fall. Rotator cuff tears fall into two categories: partial thickness tears and full thickness tears.
Full thickness tears of the rotator cuff occur when the tendon completely detaches from the ball. This will result in a gap between the edge of the tendon and its normal attachment to the bone. This can be seen in the following MRI image:
Partial thickness tears occur when a portion of the tendon is torn, but some of the tendon fibers remain attached to the ball. This can be seen on MRI as well. Dark tendon fibers are still attached to the ball but there is a small white "gap" on the undersurface of the tendon. The undersurface of the tendon is the most common site for partial thickness rotator cuff tears. This can be seen in the following MRI image:
Rotator cuff injuries are often managed successfully with a supervised Physical Therapy program consisting of stretching and strengthening. In some circumstances, early surgical intervention may be recommended.
The bone of the socket is relatively flat. The socket has a rim of soft cartilage that exists in order to "deepen" the socket. This helps to keep the ball from sliding out of joint. Sliding out of joint may be referred to as subluxation or dislocation.
The ring of soft cartilage around the socket is known as the labrum. When the labrum tears away from the socket, the injury is often called a "labral tear". This may result in the sense of instability of the shoulder.
The normal labrum is usually seen as a dark black triangular structure on MRI. The MRI image below shows a normal labrum. The labrum is directly attached to the socket.
Labral tears can often be detected on magnetic resonance images. The labrum will be detached from the socket, and a "gap" will be present between the labrum and the socket. This gap is usually white. The MRI image below shows a labral tear:
Many labral injuries can be effectively treated with conservative treatment including supervised Physical Therapy. In some cases, surgery may be recommended.