Rotator Cuff Injury: Addressing Overhead
Overuse
Preston M. Wolin, MD; Joyce A. Tarbet, MD
THE PHYSICIAN AND
SPORTSMEDICINE
- VOL 25 - NO. 6 - JUNE 97
In Brief: Rotator cuff injuries in sports are usually a result of microtrauma
from repetitive movements. Classic, or primary, impingement results directly
from overhead motions, and secondary impingement is related to underlying
shoulder instability. A variety of physical maneuvers are used to assess pain,
muscle weakness, and shoulder stability. The workup also includes plain x-rays,
supplemented by other imaging tests if a cuff tear is suspected. Nonoperative
treatment, which may include steroid injections, is often effective for an
inflamed rotator cuff tendon. Surgery is indicated if the patient has no
improvement after at least 6 weeks of physical therapy.
For
competitive or recreational athletes involved in baseball, tennis, or swimming,
shoulder disorders--especially rotator cuff injuries--can be debilitating.
Though medical understanding of rotator cuff injuries has improved greatly,
successful diagnosis and treatment of patients still depend on understanding
the mechanisms of injury and ruling out shoulder instability, particularly in
athletes who use overhead motions. The keys to success include tailoring the
treatment to the diagnosis and prescribing appropriate rehabilitation programs,
either alone or in combination with surgery.
Functional Anatomy
The subscapularis, supraspinatus, infraspinatus, and teres minor muscles are
collectively referred to as the rotator cuff. Together with the deltoid, they
place the arm in the overhead position essential in many sports.
Individually, the subscapularis is an internal rotator of the arm. It is
innervated by the upper and lower subscapular nerves, branches of the posterior
cord of the brachial plexus. The supraspinatus assists the deltoid in abducting
the arm, with its greatest contribution being the initiation of abduction
(1,2). It is innervated by the suprascapular nerve of the brachial plexus. The
infraspinatus and teres minor muscles both externally rotate the arm. The
infraspinatus is also supplied by the suprascapular nerve, while the teres
minor is innervated by a branch of the axillary nerve. Together, the supraspinatus,
infraspinatus, and teres minor muscles abduct and externally rotate the arm
into the cocked position for throwing.
In addition, muscles of the rotator cuff, primarily the infraspinatus, teres
minor, and subscapularis (1,3,4), depress and stabilize the humeral head.
Without them, the humeral head would move upward in the glenoid fossa during
arm abduction because of the unopposed pull of the deltoid muscle. This
movement would result in constant abutment against the coracoacromial arch.
![[FIGURE 1]](Rotator%20Cuff%20Injury_files/image001.gif)
The coracoacromial arch forms the roof over
the rotator cuff (figure 1). The structures forming this arch include the
acromion, the acromioclavicular joint, the coracoid process, and the
coracoacromial ligament. Variations in the architecture of the coracoacromial arch
determine the amount of space available for the rotator cuff. This space is
called the supraspinatus outlet (5). Therefore, reduction of this space by a
downward sloping anterior acromion or by acromioclavicular osteophytes can
result in impingement and injury to the rotator cuff.
Microvascular injection studies of rotator cuffs in human cadavers of all
ages have demonstrated an undervascularized zone within the supraspinatus
tendon just proximal to its humeral insertion (6,7). In addition, studies have
shown that the articular surface is less vascular than the bursal surface in
this zone (6). and that there is a significant decrease in vascularity with
aging (7). Since most degenerative tears occur in this hypovascular region of
the supraspinatus, it is assumed that this localized relative ischemia combined
with aging plays a role in the pathogenesis of rotator cuff tears.
Mechanisms of Injury
Several different mechanisms of rotator cuff injury are presently
recognized. These can be divided into acute traumatic injuries (macrotrauma)
and the more common repetitive overuse injuries (microtrauma) seen in overhead
activities.
Acute macrotraumatic rotator cuff injury, although uncommon, can result in
partial- and full-thickness tears from a direct contact injury to the shoulder
in patients under 40 years old (8). In addition, partial and complete tears of
the rotator cuff can occur with traumatic anterior instability of the
glenohumeral joint in the over-40 population; rupture of the subscapularis
should especially be considered among these patients (9).
Four microtraumatic mechanisms of rotator cuff injury have been described,
and several may occur simultaneously in the same patient.
Primary impingement. The first is the classic impingement injury, now
called primary impingement (10). Repetitive overhead activity results in
impingement of the supraspinatus against the anterior, inferior aspect of the
acromion and/or the coracoacromial ligament.
The shape of the anterior slope of the acromion has been implicated in the
development of primary impingement. Three distinct shapes have been described
on the basis of a Y view or lateral radiograph of the scapula (figure 2). Type
I is a flat acromion, type II is curved, and type III is hooked. Although the
cause-effect relationship between acromial shape and rotator cuff disorders is
unclear, the occurrence of a full-thickness tear appears to correlate closely
with a type II and especially a type III acromion. Bursal side,
partial-thickness rotator cuff tears are associated with a type II acromion
(5,11).
![[FIGURE 2]](Rotator%20Cuff%20Injury_files/image002.gif)
Primary impingement injury has three stages (10). The first stage is edema
and hemorrhage. With repetitive impingement comes the second stage of fibrosis
and tendinitis; the subacromial bursa becomes fibrotic and thickened, and the
supraspinatus tendon becomes further inflamed. The third stage can be a partial
(usually bursal side) or a complete tear of the rotator cuff, with bony changes
like spurring of the anterior acromion.
Secondary impingement. The second microtraumatic mechanism is
secondary impingement. Individuals who have shoulder instability as a result of
congenital laxity, repetitive microtrauma (from participation in overhead
sports), or macrotrauma place increased demands on the rotator cuff as it
attempts to keep the humeral head centered in the glenoid. These demands are
especially pronounced with overhead activities. Fatigue, intrinsic injury
(tendinitis), and a partial undersurface tear of the cuff may ensue. If the
rotator cuff continues to fatigue, it may no longer center the humeral head in
the glenoid, and dynamic cephalad migration of the humeral head in the glenoid
occurs, resulting in secondary impingement of the rotator cuff under the
coracoacromial arch.
Tensile failure. A third mechanism of microtrauma to the rotator cuff
is tensile failure with throwing. The throwing motion has been divided into
five phases: wind-up, early cocking, late cocking, acceleration, and
follow-through (12). Electromyographic analysis of the throwing motion has
demonstrated that the supraspinatus, infraspinatus, and teres minor muscles
begin to fire at the end of early cocking phase and become idle at the end of
late cocking as the shoulder has achieved maximum external rotation. The
subscapularis subsequently fires in late cocking to decelerate the shoulder's
external rotation. However, it is during follow-through when all the rotator
cuff muscles fire most intensely. As the subscapularis internally rotates the
shoulder, the remaining rotator cuff muscles are contracting eccentrically to
decelerate the arm. During this repetitive eccentric loading, the rotator cuff
is prone to overload, fatigue, tendinitis, and even a partial undersurface
tear. Again, as the rotator cuff fatigues, dynamic cephalad migration of the
humeral head can occur, resulting in secondary impingement of the rotator cuff
under the coracoacromial arch.
![[FIGURE 3]](Rotator%20Cuff%20Injury_files/image003.gif)
Internal or posterior superior glenoid
impingement. The fourth and final mechanism of microtrauma is internal or
posterior superior glenoid impingement (figure 3) (13). This occurs with
repetitive overhead activities, particularly in throwers, when the arm is
abducted 90° and maximally externally rotated. In this position, the posterior
inferior aspect of the supraspinatus is impinged between the greater tuberosity
of the humeral head and the posterior superior labrum, producing fraying of the
posterosuperior labrum and an undersurface tear of the posterior aspect of the
supraspinatus. In addition, this position puts very high stresses on the
anterior inferior capsule. Therefore, glenohumeral instability may be
associated with internal impingement.
Clinical Presentation
The symptoms of rotator cuff injury caused by both macro- and microtraumatic
mechanisms include pain, weakness, and limitation of active motion. Pain tends
to be located in the anterior, superior, and lateral aspects of the shoulder.
Patients with acute inflammation of the rotator cuff have intermittent mild
pain with overhead activities. Patients with chronic inflammation of the
rotator cuff have persistent, moderate pain with overhead activities; there may
be pain at rest, but much less than with overhead activities. Patients with
partial and full-thickness rotator cuff tears have persistent pain at rest that
is often referred to the deltoid insertion. Those with complete cuff tears
typically have night pain. The symptoms of weakness and limitation of active
motion may be the result of pain or a rotator cuff tear.
Physical examination will usually demonstrate tenderness in the subacromial
space. Atrophy may be apparent in the supraspinatus or infraspinatus fossa in
patients with full-thickness tears.
![[FIGURE 4]](Rotator%20Cuff%20Injury_files/image004.gif)
Pain and muscle weakness can be evaluated by
manual motor testing. The subscapularis lift-off test (figure 4) of Gerber and
Krushell (14) is performed with the arm internally rotated behind the back with
the elbow flexed. The patient pushes away from the back against resistance,
keeping the elbow flexed; inability to push away indicates subscapularis
injury.
Resistance testing of the supraspinatus is performed with the arms abducted
90° in the scapular plane (30° anterior to the coronal plane of the body) and
internally rotated so that the thumbs point toward the floor. The examiner
applies a downward force, while the patient attempts to maintain the arms
parallel to the floor. Inability to resist the examiner's downward force
demonstrates isolated supraspinatus weakness.
The infraspinatus and teres minor muscles are examined together. Patients
position their arms at their sides, elbows flexed. Weakness of external
rotation against resistance is abnormal.
The impingement sign of Neer (15) is positive when forcibly forward flexing
the arm--jamming the greater tuberosity against the anterior inferior surface
of the acromion (15)--causes pain. Another method of demonstrating impingement
is by forward flexing the shoulder to 90° and internally rotating the proximal
humerus, driving the greater tuberosity under the coracoacromial ligament (16).
The impingement test involves administering 10 mL of 1% lidocaine
hydrochloride into the subacromial space and repeating the impingement sign of
Neer (10). Pain relief confirms the diagnosis of impingement syndrome. If pain
relief eliminates weakness, then a complete tear is unlikely.
The diagnosis of instability and therefore secondary impingement must always
be ruled out. Stability testing is initially performed with the patient supine.
To test for anterior translation of a patient's right shoulder, the patient's
right hand is placed in the examiner's right axilla and held by the examiner.
The patient remains completely relaxed. The right shoulder is held in 90°
abduction and neutral external rotation. The patient's scapula is stabilized by
the examiner's left hand by pressing the scapular spine forward with the index
and middle fingers and applying counterpressure with the thumb on the coracoid
process. The examiner's right hand grasps the patient's right humerus and an
attempt is made to lever the humeral head over the rim of the glenoid
anteriorly. Anterior translation is measured as grade 0 (no motion), grade 1
(humeral head to the glenoid rim), grade 2 (humeral head over the glenoid rim),
and grade 3 (frank dislocation). Posterior translation is similarly recorded.
The apprehension and relocation tests are also for anterior instability.
With the patient supine, the apprehension test is performed by abducting the
patient's arm to 90°, externally rotating it, and trying to translate the
humeral head anteriorly. Patient apprehension is noted with the development of
anxiety and the sensation of impending subluxation. (The patient may say,
"My shoulder feels like it is coming out.") The relocation test is
then performed by placing a hand on the anterior aspect of the patient's
shoulder and applying a posteriorly directed force (to prevent anterior translation
of the humeral head), while doing the apprehension test. A positive relocation
test is obtained when the hand pressure eliminates the patient's apprehension.
The sulcus sign is performed to demonstrate inferior instability, a
component of multidirectional instability. This test is done with the patient
sitting upright with the shoulder in neutral position. The examiner applies
downward traction on the humerus and looks and feels for the development of a
sulcus between the greater tuberosity of the humerus and acromion.
Diagnostic Imaging
![[FIGURE 5]](Rotator%20Cuff%20Injury_files/image005.gif)
Radiographic evaluation of the shoulder
starts with a routine shoulder series, including anteroposterior (AP) views
with both internal and external rotation of the humerus. These views profile
the acromioclavicular and glenohumeral joints and the tuberosities of the
humerus and provide information regarding fractures, dislocations, arthritic
changes, and calcific deposits. An acromiohumeral distance of less than 7 mm on
the AP internal rotation view indicates the static cephalad migration of the
humeral head in chronic rotator cuff tear (figure 5). An axillary view allows
better visualization of the glenohumeral joint and glenoid margin as well as
the acromion. A scapular Y view assesses the anterior slope of the acromion. The
Stryker notch view best evaluates the presence of humeral head defects
(Hill-Sachs lesions) seen in anterior instability.
Special diagnostic imaging, such as arthrography, ultrasonography, and
magnetic resonance imaging (MRI), may aid in evaluating the rotator cuff. The
goal of any special test is to provide information regarding the presence of a
partial- or full-thickness tear of the rotator cuff, the size of the tear
(retraction), and the quality of the muscle. Such information is especially
important if surgery is being considered.
Shoulder arthrography (both single and double contrast) can help in
diagnosing full-thickness rotator cuff tears. However, its ability to detect
partial undersurface tears remains controversial, and bursal side partial tears
will go undetected. In addition, it cannot evaluate the size of a tear or the
quality of the muscle. Arthrography, although inexpensive to perform, is
invasive.
Ultrasonography is noninvasive, painless, and inexpensive. Although it is
widely used in Europe, its reliability is controversial, and its diagnostic
accuracy appears to depend on the skill of the sonographer.
![[FIGURE 6]](Rotator%20Cuff%20Injury_files/image006.gif)
MRI is very accurate at depicting full
thickness rotator cuff tears (figure 6). The sensitivity and specificity for
full thickness tears are 100% and 95%, respectively (17). The advantage of MRI
is its ability to show the location, size, and retraction of the tear as well
as co-existing pathology, such as labral tears. It can also assess the quality
of the muscle; in chronic tears, the muscle degenerates and fat infiltrates,
preventing normal muscle performance even if the tendon is repaired to bone.
MRI can aid in diagnosing partial tears with 82% sensitivity and 85%
specificity. Its major disadvantage is cost.
Suprascapular nerve entrapment should always be included in the differential
diagnosis of patients with shoulder weakness. These patients present with
weakness of external rotation and occasionally abduction that can be
accompanied by atrophy of the infraspinatus and/or supraspinatus. Pain is not
usually a significant symptom but, if present, tends to be a dull ache in the
posterior aspect of the shoulder. Electrodiagnostic studies, such as
electromyography and nerve conduction velocity, should be obtained. MRI is
recommended to assess the possible causes of nerve entrapment, such as a
ganglion cyst.
Nonoperative Treatment
Nonoperative management is often effective for treating acute and chronic
inflammation of the rotator cuff, and a supervised program of physical therapy
is the mainstay. The first phase of therapy aims to reduce rotator cuff
inflammation and improve range of motion. Rest from the inciting activity is
often accompanied by cryotherapy and short-term nonsteroidal anti-inflammatory
drugs, if not contraindicated. The glenohumeral joint is mobilized with passive
and active assisted range of motion; the arc of motion should be increased as
pain permits. Overhead athletes commonly have limited internal rotation (and
therefore a tight posterior capsule) and increased external rotation. However,
a tight posterior capsule may aggravate impingement because it forces the
humeral head against the anteroinferior acromion as the shoulder is forward
flexed (5). Therefore, local heat or ultrasound followed by gentle stretching
of the posterior capsule in cross-body adduction and internal rotation can be
helpful.
A subacromial corticosteroid injection, which bathes the tendon, can provide
significant pain relief in impingement cases (18). However, injection into the
tendon must be avoided since adverse reactions, including a significant loss of
ultimate tensile strength and spontaneous rupture, have been well-documented
(19). Since local corticosteroid injection is associated with tendon weakness
caused by collagen necrosis and the disruption of the normal parallel collagen
arrangement, corticosteroid use in partial tears is a concern. The following
are guidelines for corticosteroid use:
- Never inject into the tendon,
- Use a maximum of two injections at least 3 months
apart, and
- Prescribe 1 week of rest from resistance exercises
after an injection.
The second phase of physical therapy emphasizes full and painless
range-of-motion exercise. Progressive isometric exercises, performed in the
nonpainful planes below shoulder level, should include the scapular
stabilizers, the trapezius, levator scapulae, rhomboid major and minor, and
serratus anterior muscles. Strengthening the stabilizers can restore proper
scapulohumeral motion.
The third phase of therapy introduces isotonic exercises to strengthen the
rotator cuff, deltoid, and scapular stabilizers in order to stabilize the
humeral head in the glenoid and prevent the dynamic, proximal migration leading
to impingement. These exercises, initially done with light weights or elastic
bands, are performed below shoulder level and with the arm at the side to
prevent irritation of the inflamed cuff. Exercises that isolate specific cuff
muscles, especially the supraspinatus at greater than 90° abduction, should be
avoided to prevent reinjury. In addition, the thumb should be turned upward
during exercise to externally rotate the humerus, moving the greater tuberosity
away from the acromion.
Weight-bearing, closed-chain exercises promote dynamic strengthening with
proprioceptive input; in one such exercise the patient "walks" on his
or her arms while the trunk is supported by a Swiss ball or a low stool.
Plyometric and sport-specific activities, such as high-speed tubing exercises,
come last and often accompany isokinetic concentric and eccentric training. An
athlete recovering from an impingement disorder should gradually return to
sports activity while continuing to work with an athletic trainer and coach to
ensure proper mechanics.
Operative Treatment
Surgical treatment of chronic inflammation of the rotator cuff is indicated
only if the patient fails to progress after a minimum of 6 weeks of supervised
physical therapy (5). Individuals with a flat acromion (type I), demonstrated
on a scapular Y view, are likely to have secondary impingement, and the underlying
instability will need to be addressed. Those with a type II (curved) or type
III (hooked) acromion may undergo subacromial decompression whereby the
anterior inferior acromion is resected, converting it to type I. This is also
referred to as an anterior acromioplasty. Subacromial decompression can be
performed through open or arthroscopic approaches. Arthroscopic subacromial
decompression has an overall patient satisfaction rate of 92% (20). The only
disadvantage of the arthroscopic technique is its technical difficulty.
The open technique of subacromial decompression is technically easier to
perform than the arthroscopic technique. However, it does not allow inspection
of the glenohumeral joint for co-existing pathologies, such as labral tears, biceps
tendon tears, or undersurface partial-thickness rotator cuff tears. In
addition, the open technique requires some detachment of the deltoid from the
acromion to facilitate exposure. The detached deltoid is surgically reattached
but requires postoperative protection, thus retarding rehabilitation and
possibly resulting in residual weakness.
Partial-thickness rotator cuff tears can be approached in two ways. Tears
affecting less than 40% of the total cuff thickness can be treated by
arthroscopic debridement with subacromial decompression to remove the anterior
curve of the acromion that is impinging on the rotator cuff. Partial-thickness
tears greater than 40% of the cuff thickness over an area of more than 1 cm2
should be excised and repaired.
Repair of full-thickness rotator cuff tears varies. If a tear is less than 1
cm long (anterior to posterior), it can be treated with debridement and
subacromial decompression. Tears longer than 1 cm should be treated with
subacromial decompression and repair. Surgeons use one of three general
approaches, depending on their preference and the size of the tear. The all
arthroscopic rotator cuff repair done solely through arthroscopy is presently
investigational. The mini-open deltoid splitting technique, which has demonstrated
an 83% good to excellent result (21), has the advantage of splitting rather
than detaching the deltoid from the acromion; however, exposing massive tears
with this technique is technically difficult. The classic open approach, while
requiring deltoid detachment, may be required for massive tears. If a massive
tear has been neglected, successful repair is not always possible; if the
posterior and anterior cuff is intact, however, patients with such massive
tears can obtain significant pain relief with arthroscopic subacromial
decompression and debridement (4). No matter what the operative procedure, the
goals of rotator cuff repair are to preserve the deltoid and make a good repair
that allows early range-of-motion exercise and thus reduces the likelihood of a
stiff shoulder.
Postoperative rehabilitation varies with the surgical procedure performed.
Patients with partial-thickness rotator cuff tears treated with arthroscopic
subacromial decompression and debridement are placed in a simple sling. Active-assisted
range-of-motion exercise begins immediately. Full active motion is achieved
within 2 weeks. Resistive exercises and progressive strengthening start during
the second week and continue for up to 12 weeks. Full return to sports
activities requires 2 to 3 months, but high-level overhead athletes may take
longer.
Following mini-open rotator cuff repair, patients use a simple sling only.
Many surgeons prescribe an abduction pillow to prevent stretching of the
repair. When the tendon is repaired with the arm at the side, passive
range-of-motion exercises begin immediately. Active-assisted motion is started
at 4 weeks, allowing for initial healing of the repair, and active motion is
started at 6 weeks. Resistive exercises are then introduced. Full rehabilitation
takes approximately 4 to 6 months.
The classic open technique requires prolonged postoperative protection of
the deltoid, so rehabilitation is slower, taking about 9 to 12 months for full rehabilitation.
The phases of rehabilitation, though delayed and extended, are essentially the
same as those described above.
Injury Prevention
Coaches and athletic trainers can help develop and carry out sound programs
for preventing rotator cuff injuries. Preseason conditioning should address the
flexibility, strength, and endurance of the shoulder muscles, particularly the
scapular stabilizers and external rotators of the rotator cuff. The
conditioning program must be tailored to the sport and fitness level of the
athletes. Learning the correct mechanics of the sport and choosing proper
equipment are also important. In-season training must be adjusted to avoid
overuse injuries, and a proper warm-up and cool-down period should be routine
with practice or competition. Such measures will not only help prevent injury,
but will also make athletes more successful.
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Dr Wolin is director of the Center for Athletic Medicine in Chicago, team
physician for