Rotator Cuff Tears, Partial

Types

There are three types of partial tears: (1) bursal-side tear (BT), confined to the bursal (outer) surface of the tendon; (2) intratendinous tear (IT), found within the tendon; and (3) joint-side tear (JT), present on the side of the tendon adjacent to the joint (inner side).

Incidence

The true incidence of partial tears is not known. Most data have been obtained from cadaver and imaging studies. Yamanaka and Fukuda reported an incidence of supraspinatus partial-thickness and full-thickness tears of 13% and 7%, respectively, in a group of 249 cadaveric specimens in 1987. Partial-thickness tears were further grouped as bursal sided (2.4%), intratendinous (7.2%), and articular sided (3.6%). However, several authors have noted that, clinically, articular-sided tears are two to three times more common than bursal-sided tears. In fact, in a population of young athletes, articular-sided tears constituted 91% of all partial-thickness tears.

Partial tears of the suprapinatus are the most common, but tears can also occur in the infraspinatus and subscapularis.

Pathology

Causative factors can be broadly categorized as either intrinsic or extrinsic to the rotator cuff tendons.

Intrinsic causes may be subclassified into metabolic and vascular changes that lead to degenerative tearing or intratendinous lesions developing from shear stress. A zone of relative poor blood supply is seen on the articular surface of the rotator cuff 1 to 2 centimeters from its insertion on the humerus. This area is particularly at risk for tear.

Extrinsic causes include subacromial impingement (trapping of the tendon by the acromial spur), shoulder instability (typically anterior), [Page 1228]internal impingement (trapping of the tendon by the humeral head), a single acute traumatic injury, or repetitive microtrauma.

Often, more than one of these factors (either intrinsic or extrinsic) is responsible for the development of a partial-thickness tear. The articular surface of the rotator cuff has an ultimate stress to failure that is approximately half that of the bursal surface, with thinner and less uniformly arranged collagen bundles. It is believed that articular tears are due to intrinsic pathologic changes of the rotator cuff, whereas bursal-side tears are associated with subacromial impingement on an underlying, milder pathologic change of the rotator cuff.

Diagnosis

Pain, especially at night, is the most irritating symptom. Partial tears can be more painful than full-thickness tears.

The results of impingement tests, such as the Neer and Hawkins tests, with or without subacromial local anesthetic injection, are often positive in the presence of partial-thickness rotator cuff tears, although occasionally these test results are negative, especially in the high-level, well-conditioned athlete.

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