Rotator Cuff Tears Physical Examination
The rotator cuff tendons surround the humeral head and provide rotational control and strength to the shoulder. Along with the large deltoid muscle, these muscles are primarily responsible for elevation of the shoulder. When there are significant tears of the rotator cuff, there is loss of elevation of the shoulder and weakness. There is often tenderness as well as subacromial crepitation with rotational motion of the arm. External rotation weakness is demonstrated by the lag sign and demonstrates involvement of the supraspinatus infra spinatus tendons and, on occasion, the teres minor tendon. These tendons are primarily responsible for external rotation strength. Tears involving these three tendons can cause a positive external rotation lag sign. The level of weakness as seen by the amount of internal rotation drift from the point of full passive external rotation is associated with the size of the tear and the number of tendons involved. In some cases there can be weakness of external rotation secondary to nerve injury (see Plate 1-51). The supraspinatus and infraspinatus muscles are innervated by the suprascapular nerve. When there is injury to this nerve, often due to a compressive lesion at the suprascapular notch or the spinoglenoid notch (see Plate 1-51), the muscle will be weak and is best tested by resistance in external rotation or by the external rotation lag sign.
Large and massive rotator cuff tears often involving two or more of the rotator cuff tendons will typically result in the patient’s inability to either raise the arm or maintain an elevated position of the arm against moderate resistance. The shrug sign is defined as the inability to elevate the arm associated with compensatory elevation of the scapula. In some cases there is an inability to raise the arm, but this is not associated with elevation of the scapula. This can resemble paralysis of the shoulder, but in these cases the nerves to the muscles are normal and thus this is termed pseudoparalysis. This loss of elevation is generally associated with superior escape of the shoulder due to deficiency of the coracoacromial arch (see Plate 1-48). All of these signs of loss of elevation are physical examination findings associated with rotator cuff weakness and are associated with different parts of the rotator cuff and other associated shoulder pathologic processes, such as deficiency of the coracoacromial arch. For the diagnosis to be related to a large rotator cuff tear when the shrug sign or other signs of rotator cuff weakness are present, there should be full or near-full passive range of motion of the shoulder and the apparent weakness should not related to significant pain. In some cases of large and massive tears, the patient can achieve full active elevation yet with weakness that can be demonstrated by the inability to hold the arm at 90 degrees of elevation against mild to moderate resistance. Smaller tears, particularly those without severe pain, can demonstrate normal range of motion and remarkably good strength with these tests; negative tests are not an indication for lack of a full thickness tear often in the 1- to 2-cm range. Patients with smaller tears will often demonstrate weakness with the internal and external rotation strength testing or lag signs tested with the arm by the side of the body. When the validity of these tests is in question as they relate to testing the strength of the shoulder due to pain associated with stiffness due to a frozen shoulder or subacromial pain due to inflammation of the bursae or other soft tissues of the shoulder, then injection of a local anesthetic to either the glenohumeral joint and/or to the subacromial space will often relieve the pain, thereby both confirming the location of the pain and pathologic process to the shoulder (i.e., cervical spine or other non shoulder-related referred pain to the shoulder) and allows for reexamination for shoulder strength in a setting of minimal or much reduced shoulder pain.