Partial-Thickness Rotator Cuff Tears

Partial-thickness rotator cuff tears constitute an interesting and difficult group of shoulder lesions. In large part, the difficulty stems from terminology: we use the phrase partial-thickness rotator cuff tear to describe the anatomic end result of several different pathophysiologic pathways. If we consider rotator cuff disease to be an intrinsic tendinopathy and part of the natural aging process, partial-thickness rotator cuff tears represent a transition from tendinosis to tendon rupture. If we view rotator cuff changes as lesions caused by extrinsic compression forces, partial-thickness rotator cuff tears are the result of more compression than that which results in tendinosis and less compression than that which results in full-thickness tears. If we accept the hypothesis that partial-thickness rotator cuff tears are the result of compression between the humeral head and the acromion, do these compression forces cause partial-thickness tears in patients with internal impingement? Perhaps the rotator cuff tears we see in younger patients are due to excessive eccentric muscular contraction. Because it appears that the same anatomic lesion (partial-thickness rotator cuff tear) can be caused by different mechanisms, the surgeon must determine the cause and treat the tear accordingly.

Diagnosis

Patients with partial-thickness rotator cuff tears may present with signs and symptoms typical of rotator cuff disease. When the shoulder is elevated through the painful arc during activities of daily living, pain is localized deep to the lateral deltoid muscle (subdeltoid pain). Night pain may also occur. Examination demonstrates normal active and passive range of motion with positive impingement signs. Subacromial anesthetic injection relieves the pain for bursal-sided tears. A critical feature of the examination is the amount of pain and weakness observed when resisted manual muscle testing is performed. Significant pain and weakness with resisted external rotation or elevation are relative indications for early operative intervention. Plain radiographs appear similar to those of patients with impingement syndrome or full-thickness tears. Most commonly, the diagnosis is made with magnetic resonance imaging (MRI). The use of intra-articular gadolinium increases the sensitivity of MRI (MRA) in patients with partial-thickness rotator cuff tears, particularly in those who must have open MRI. Diagnostic ultrasonography has also been very helpful, especially in cases of intrasubstance partial-thickness rotator cuff tears ( Figs. 11.1–11.3 ). Often, a partial-thickness tear is found at the time of arthroscopic examination of the glenohumeral joint.