by Steve Kilgore
The Rotator Cuff - Anatomy
The Rotator Cuff consists of four muscles that function to dynamically stabilize the shoulder joint.
(http://www.mendelsonortho.com/_livesite2012/wp-content/uploads/2011/11/cons1_348_127.gif) The muscles include the supraspinatus, infraspinatus, teres minor, and subscapularis. Activation of the rotator muscles results in movements of abduction, internal rotation, and external rotation. These muscles also function as stabilizers by depressing the humeral head in the gleniod fossa during motion about the joint.
The supraspinatus muscle is involved in the initial 15 to 30 degrees of abduction required for elevation of the upper extremity into overhead motions. The infraspinatus is responsible for external rotation of the shoulder in conjunction with the teres minor. The subscapularis muscle completes the rotator cuff as it functions as an internal rotator of the shoulder. The muscle most commonly involved in rotator cuff pathologies is the supraspinatus. The supraspinatus muscle in vulnerable to tearing due to its anatomic position and the biomechanics of the shoulder complex. 1,2
The prevalence of rotator cuff tears increases with age. The pathology is most commonly seen between 40 and70 years of age. Many patients that have a full-thickness tear are asymptomatic, accounting for nearly 40% of rotator cuff injuries. In comparison patients greater than age 60 presenting with partial and full-thickness tears account for approximately 60% of rotator cuff tears. The supraspinatus is most commonly injured muscle of the rotator cuff. 1,2,3,4
Rotator Cuff Biomechanics and Function
The rotator cuff functions to approximate the humerus in the glenoid fossa. The supraspinauts muscle assists the deltoid in abduction of the upper extremity while the subscapularis, infraspinatus, and teres minor function to depress the humeral head. The muscles of the rotator cuff dynamically stabilize the joint during movement. Additionally the rotator cuff muscles act as essential force couples to aide in normal strength and function. When the muscles work together they contribute to rotational movement about the shoulder joint while providing stability and support to the entire shoulder complex. 1,2,3
Anatomic Representation of Rotator Cuff Muscles Surrounding the Glenoid Fossa
The proximal attachment of the humerus is the medial two-thirds of the supraspinatus fossa and the deep fascia that covers the muscle. The distal attachment is the most superior facet on the greater tubercle of the humerus. It is innervated by suprascapular nerve and functions to initiate abduction of the arm. The tendon of the supraspinatus blends into the joint capsule, as well as the tendon of the infraspinatus. Additionally, the tendon of the supraspinatus muscle passes under the acromion of the acriomioclavicular joint. Inflammation in this area can lead to injury of supraspinatus tendon.
Actively, the supraspinatus muscle plays a role as a stabilizer of the humeral head by compressing it into the glenoid fossa. Throughout movement of the upper extremity, the supraspinatus helps make up for the lack of stability at the glenohumeral joint. By compressing the humeral head the supraspinatus aids in the prevention of shoulder dislocation in lower ranges of motion during abduction (60 to 90 degrees of abduction). 1,2,5
Essential force couples between the deltoid and rotator cuff muscles are active during abduction of the shoulder. The deltoids superior line of force directs the humeral head upward. At the same time, the supraspinatus causes the humeral head to roll into the movement of abduction while it is also compressing glenohumeral joint for added stability. Additionally the remaining muscles of the rotator cuff act to stabilize the shoulder complex by counteracting superior translation of the humeral head. When essential force couples surrounding the shoulder complex are disrupted weakness and decreased range of motion contribute to poor function. A major decrease in overhead activities may lead to gross functional limitations. 3,6
Causes of rotator cuff pathology are theorized to be consistent with two etiological factors related to strength and force. It is believed the tensile strength of the rotator cuff tendon and the amount of force being applied to the rotator cuff directly relates injury. Repetitive micro-traumas, subacromial impingement, tendon degeneration, and hypo-vascularity can decrease the integrity of the rotator cuff muscles leading to decreased strength and decreased ability to resist shearing forces. 5,6,7
Patients greater than 40 years of age will present with pain that may involve the lateral arm with radiation no further than the elbow. Initially the patient may have experienced a loss of strength is abduction that has progressed to persistent pain in the shoulder region. Complaints may also include pain and difficulty with overhead activity, night pain, and a history of trauma to the upper extremity. During the initial evaluation the following should be noted: 2-10
• Manual Muscle Testing (MMT)
• Range of Motion (ROM)
Manual Muscle Testing
Abduction is the primary action of supraspinatus muscle, initially assisting the deltoid during the first 15 to 30 degrees of motion. This motion can be test two ways:
1. Arm Elevated4,5,7,9
• Supraspinatus strength tested with patient sitting
• The arm is held at 90 of forward flexion and moved into 45 degrees about the scapular plane.
• The patient is resists downward pressure by the examiner
Australian Family Physician 2004;33(3):143-147
2. Arm at Side4,5,7,9
• The supraspinatus muscle is tested with the elbow extended and the arm held at the side
• The arm is position at 45 degrees in respect to the scapular plnae of motion
• The patient attempts to raise the arm into flexion while being resisted by the examiner
• This test is the preferred examining position because the primary action of the supraspinatus is activation during the first 15 degrees of abduction to initiate movement of the upper extremity.
MMT Video for Supraspinatus
Range of Motion Testing
Range of motion of the supraspinatus muscle is assessed with a goniometer. Normal abduction of the shoulder joint is 180 degrees. A decrease in motion may be the result of tight musculature or decreased strength of the supraspinatus muscle. How to measure shoulder abduction: 2,7,8
• Patient seated or supine
• Align the stationary arm of the goniometer vertically with the side of the trunk in the frontal plane (front or back) with the axis close to the acromion process
• The moveable arm of the goniometer should be parallel to the arm, using the lateral epicondyle of the humerus as a reference points
• Move the moveable arm along with the arm in abduction. The shoulder abduction range is the angle between the stationary arm and the moveable arm of the goniometer
• Normal abduction measures180°
When suspecting a rotator cuff tear all muscles of the rotator cuff should be tested to determine which muscles may be torn. Since the supraspinatus muscle is most commonly involved in rotator cuff tears the following special tests: 2,4,5,9,10
• Drop Arm
• Empty Can
• Impingements Tests
• Lag Sign
Drop Arm Test
This test is performed by passively abducting the patient's shoulder, then observing as the patient slowly lowers the arm to the waist. Often, the arm will drop to the side if the patient has a rotator cuff tear or supraspinatus dysfunction. The patient may be able to lower the arm slowly to 90 degrees (because this is a function mostly of the deltoid muscle) but will be unable to continue the maneuver as far as the waist.
Drop Arm Test Video
Empty Can Test
The empty can position is 90 degrees of abduction, 30 degrees of horizontal flexion, and full internal rotation of the arm. Thumbs are pointed down. The examiner pushes downward while the patient resists the motion.
Empty Can Test Video
Impingement & Hawkins’s Impingement Tests
The ‘impingement sign’, also known as Neer’s Neer describes impingement of the supraspinauts to be the result of a mechanical issue between the tendon and the acromion. To elite an “impingement sign”, scapular rotation is prevented with one hand. Simultaneously, the other hand raises the arm in forced forward elevation, causing the greater tuberosity of the humerus to impinge against the acromion. If this action causes pain, the test is positive, indicating supraspinatus pathology.
This test is performed by positioning the arm in 90° of flexion and then forcibly internally rotating the shoulder. The test is positive if this maneuver provokes pain. A positive impingement test and a positive Hawkins test are highly suggestive of a supraspinatus tendon tear.
Hawkins-Kennedy Test http://www.clinicalsportsmedicine.com/chapters/14d.htm
A noticeable difference between the maximal active and the maximal passive range of motion of the joint in any given plane is called a lag. Determination of a lag sign is indicative of muscular weakness and possible pathology. 5
The secondary action of the supraspinatus muscle is external rotation of the arm; therefore the Lag sign called the external rotation lag sign (ERLS) may be used to assist is the diagnosis of rotator cuff pathology. Hertel and colleagues first described this sign. To perform the test, the arm is elevated 20° with the elbow passively flexed to 90° and the shoulder is placed in maximal external rotation. Next the patient is asked to maintain the position of external rotation as the examiner releases the wrist while maintaining support of the arm at the elbow. If the patient is not able to maintain the external
rotation and a “lag” occur, then the test is considered positive. 5
Lag Sign Video
Ultrasonography and arthrography have been used when rotator cuff tears are suspected. Unfortunately arthrography is invasive and expensive, therefore it is not the diagnostic test of choice. Magnetic resonance imaging, also expensive, provides the best imaging mode for rotator cuff pathology but arthroscopy is known as the best diagnostic modality. Commonly MRIs are performed to view pathologies of the rotator cuff. 3,6,7
Rotator Cuff tears can be treated conservatively or with surgical repair. Treatment options are considered based on physician recommendation, patient preference, and degree of tear. Conservative treatment consists of decreasing aggravating activities often accompanied by physical therapy, while surgical repair is more invasive and requires post-surgical rehabilitation in conjunction with rehabilitation techniques. 3,11,12
Activity modification is recommended when rehabilitating a rotator cuff tear within the supraspinatus muscle. Avoidance of overhead or pain-provoking activities is also advised. The patients’ physician may prescribe a short course of a nonsteroidal anti-inflammatory medication to reduce the associated pain and inflammation of the condition. 3,11,12
Options for conservative Care
• Decrease activity
• Use of a sling
• Strengthening and physical therapy
Surgical intervention is determined by several factors including history of trauma to the shoulder, patient age, and activity level. The decision is based per patient case as a specific protocol for surgerical intervention timing and application is not well established. Indications for surgery following a supraspinatus tear can be found below. 3,11,12
Indications for Surgery
• Failure of 3 to 6 months of conservative care of symptomatic partial-thickness rotator cuff tears
• activity level
The type of surgery performed on the rotator cuff depends on the size, shape, and location of the tear. A partial tear may require a " debridement. ", a procedure that trims or smooth frayed fibers of the supraspinatus muscle that is torn. A complete tear , defined as a tear in the thickest part of the tendon, is mended by suturing the two sides of the tendon back together. If the tendon is torn away from where it inserts into the humerus, it is repaired directly to bone. Today, many surgical repairs can be done on an outpatient basis. During the surgery the physician may remove part of the acromion as part of the procedure. This is done to eliminate impingement of the repaired tendon of the supraspinatus. Today, many surgical repairs can be done on an outpatient basis. 3,11,12
Arthroscopic photographs of a rotator cuff tear (left) and the final repair (R) This was performed all-arthroscopically. Sutures (green) were used to reattach the tendon back to bone (arrow) (Courtesy of Louis Rizio, MD.) http://orthoinfo.aaos.org/topic.cfm?topic=a00406
Three approaches of surgical repair are listed below; referenced by the AAOS (2009):
• Arthroscopic Repair. A fiberoptic scope and small, pencil-sized instruments are inserted through small incisions instead of a large incision. The arthroscope is connected to a television monitor and the surgeon can perform the repair under video control.
• Mini-Open Repair. Newer techniques and instruments allow surgeons to perform a complete rotator cuff repair through a small incision, typically 4 cm to 6 cm.
• Open Surgical Repair. A traditional open surgical incision is often required if the tear is large or complex or if additional reconstruction, such as a tendon transfer, has to be done. In some severe cases, where arthritis has developed, one option is to replace the shoulder joint.
Rotator Cuff Arthroscopic Surgery
The rotator cuff requires adequate time to heal by means of conservative treatment or surgical intervention. The rehabilitation process lasts approximately four months to one year, depending on the treatment intervention. Initially the focus of both treatments is to decrease pain and inflammation by reducing activity and resting the limb. Once the healing process has been established the focus of physical therapy interventions is increasing strength and range of motion within a pain-free range until full power and movement is attained. 3,11,12
If the tear of supraspinatus muscle is small, healing without surgical intervention may take four to nine months. ROM exercises are indicated if they can be performed without pain and discomfort. The cycle of rehabilitation is as follows; regain ROM-regain strength-increase range-increase strength. The type of strengthening exercises used during the rehabilitation process should progress initially from isometric, followed by concentric. Lastly eccentric exercises are integrated into the treatment schedule to provide return to full functional activities.
Non-surgical Treatment: Benefits and Limits
Surgical repair of rotator cuff tears is often followed by a physician directed protocol. The rehabilitation process following surgical repair of the rotator cuff, including the supraspinatus takes approximately six months to one year. Physical therapy interventions not guided by a protocol follow the guideline listed below: 3,11,12
Initial Three Weeks: patient typically in a sling
• Isometric strengthening
• Shoulder shrugs
• Pendulum activities
• Supine exercises consisting of abduction and ER
• Anti-gravity strengthening
• Progress exercises to full ROM with resistance
Protocol Link : #4 Rotator Cuff Repair Protocol
Arthroscopic Rotator Cuff Repair Protocol Copyright © 2007 The Brigham and Women's Hospital, Inc. Department of Rehabilitation Services.
• American Academy of Orthopedic Surgeons, AAOS www.aaos.org
• Amerian Family Physician, AFP www.aafp.org
• Up to Date www.uptodate.com
• American Orthopedic Society for Sports Medicine, AOSSM www.aossm.org
• Murell, G. Walton, J. Diagnosis of Rotator Cuff Tears. The Lancet. 2001;357:759-761
• Romeo, A.A., et al. Repair of Full Thickness Rotator Cuff Tears; Gender, Age, and Other Factors Affecting Outcome. Clinical Orthopedics and Related Research. 1999;367:243-255.
• Holtby, R., Razmjou, H. Valididty of Supraspinatus Test as a Single Clinical Test in Diagnosing Patients with Rotator Cuff Pathology. J of Orhop Sports Phys Ther. 2004;34:194-200.
• Hayes, K. et al. Reliability of Five Methods for Assessing Shoulder Range of Motion. Australian J of Physiotherapy. 2001;47:289-294.
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