Shoulder Tendon Disorders
Normal Anatomy
Normal Anatomy: The shoulder joint is the second largest and most mobile joint in the human body and can be easily understood if divided into three layers. The first layer is the deepest layer made up of the bones that form the foundation. There are three bones consisting of the arm bone (humerus), the shoulder blade (scapula), and the collar bone (clavicle). There is a rounded head on top of the arm bone called the humeral head and a saucer shaped surface of the shoulder blade called the glenoid which complements the humeral head and together they form the shoulder joint. A layer of cartilage (blue area) covers the articular surfaces of the humeral head and glenoid to provide a cushioned surface which allows for smooth pain free shoulder motion. These three bones unite to form three joints, which are held together by the second layer which keeps the bones from separating during shoulder movement, allowing the bones to function as a unit.
The second layer is comprised of collagen tissue fibers that attach to the bones on both sides of the joint and form the joint capsule. Within the joint capsule, are dense cordlike collagen bundles that unite to form ligaments that in strategic locations further enhance the stability of the jointby resisting the forces created when we perform our routine daily activities.
The rim of the glenoid is encircled by a rubbery fibro-cartilage tissue called the labrum. The labrum is an anchor point for the ligaments of the shoulder capsule and the long head of the biceps tendon which attach to it creating a suction seal mechanism when the humeral head is in contact with the glenoid. This sealing mechanism adds another joint stabilizing effect. The three shoulder bones form there joints called the Glenohumeral (GH) joint, Acromioclavicular (AC) joint, and the sternoclavicular (SC) joint.
The third layer in the shoulder is the muscle layer. Within the muscle layer, there are several potential spaces that carry the arteries which supply the bodies’ nutrition and nerves that deliver the commands sent by the brain and spinal cord for muscle movement. The most important muscle group in the shoulder is called the rotator cuff muscles. Theyare comprised of four muscles that begin (originate) in the shoulder blades’ flat surfaces and attach to the arm bone in an area called the greater tuberosity footprint as a common tendon unit. The four tendons formed by the four rotator cuff muscles interdigitate with one another forming a protective mechanism that prevents rotator cuff tendon tears from quickly spreading once they occur. The interdigitation also allows the four muscles to work together as a unit, carefully balancing the shoulder joint against the forces of the deltoid muscle to create precise shoulder movement. The deltoid muscle, biceps muscle and other muscles about the shoulder that balance the shoulder blade, called the scapular stabilizers complete the shoulder muscles that make up the third layer and together create a dynamic balanced force which allows for normal function. The major function of the rotator cuff muscles is to provide shoulder joint dynamic stability, shoulder joint motion and strength to the arm.
Pathology
Shoulder pain is the most common presenting shoulder complaint in an orthopedic practice. The causes of shoulder pain are divided into intrinsic (caused by structures in the shoulder) and extrinsic causes (caused by pathology outside the shoulder with the pain referred to the shoulder from another epicenter). The intrinsic causes of shoulder pain can be divided into mechanical pain which is pain occurring with active motion and non-mechanical pain which is pain occurring at rest without use of the shoulder. The causes of non-mechanical pain are commonly nerve compressions syndromes, inflammatory conditions or tumors about the shoulder. The mechanical causes of shoulder pain are the most common and include contusions, fractures, arthritis, and tendon disorders. Thetendon disorders causing shoulder pain include bursitis, tendonitis and rotator cuff tears. All of these conditions present with a physical finding called impingement. Impingement is pain that is elicited in the shoulder when the shoulder is elevated between 90°-120° overhead. It is not a diagnosis but simply a physical finding that has many causes and because of this, it is calledimpingement syndrome. Other findings associated with tendon disorders about the shoulder include limited motion due to pain and variable amounts of muscle weakness.
Bursitis is the inflammation of the tendon lining called the bursa in the shoulder. The shoulder bursa, like bursa’s present in other joints, is a cellular layer forming a sac that produces a limited amount of synovial fluid acting to reduce friction during joint motion allowing for smooth tendon gliding. The shoulder bursa is extensive and lies under the shoulder blade roof called the acromion (subacromial space), next to the space around the deltoid muscle (subdeltoid bursa) and the space under the coracoid process of the shoulder (subcoracoid bursa). When the bursa is inflamed due to injury or repetitive overhead activities, the fluid filled sac over secretes synovial fluid, thickens and results in shoulder impingement pain. When the tendon proper of the rotator cuff is inflamed it is called shoulder tendonitis and in this condition, impingementpain is also demonstrated on exam.
If arotator cuff tear develops, impingement pain in this instance is usually accompanied by variable amounts of rotator cuffweakness on physical exam. Rotator cuff tears have two theorized causes: intrinsic and extrinsic causes. There are two intrinsic causes 1) the bend the rotator cuff tendon takes prior to inserting (attaching) onto the humeral tuberosity footprint is a sharp angle which creates a differential pressure on the various tendon layers (articular vs bursal sided tendon fibers) 2) decreased blood supply to the tendon at this same site and for this same reason, as we age. The extrinsic cause is attributed to acromial bone spurs that form in the anterior and inferior part ofthe acromial undersurface with aging and consequently abrade the tendon when we perform overhead activities until a rotator cuff tear develops. The size of the acromial bony spur has been classified as being according to size and it is either flat (Type I), curved(Type II) or hooked (Type III). Types two and three are the larger ones that arebelieved to be the ones that cause the abrasion on the rotator cuff tendon that results in a rotator cuff tear.
Type I Type II Type III
SmallTear Medium Tear Large Tear Massive Retracted Tear
Rotator Cuff tears are classified as being partial or complete depending on whether the five layers making up the tendon thickness are partially torn, or completely torn with all five layers involved. Partial tears are further divided into location of the tear,occurring either on the top of the tendon called a bursal sided tear or on the joint( articular side) of the tendon called a PASTA lesion (Partial Articular SupraspinatusTendonAvulsion). If the tendon has a complete tear, it means that the tendon fibers are torn from the bursal subacromial side and communicates with the joint side allowing joint fluid form the joint to escape. Finally, when all five layers are torn, it is said to be a Complete tear, which are further divided according to their size: small (<1cm), medium (1.1-3.0 cms) large (3.1-5.0 cms) and massive tears (>5.0cms). The larger the tear, the more the associated weakness found on physical exam and the higher the probability or recurrence after it is repaired. This is why we prefer to repair a complete tear before it gets too large.
10 Things to know about a rotator cuff tears:
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1. Rotator cuff tears do not heal on their own. They require surgery to heal.
2. Rotator cuff tears when present, increase in size over time. The rate of progression is
unkown.
3. It is rare to find a rotator cuff tear in a person less than forty years of age without a prior
significant injury.
4. The incidence of Rotator cuff tears increase with age, starting at 40 years of age and are
present in about 50% of peopleafter the age of 60 years.
5. The presence of a rotator cuff tear does not necessarily mean that symptoms will also be
present.
6. The larger the rotator cuff tear, the more likely a tear will recur over timeafter a repair and
solifting discretions are permanently advised after repairing a large or massive tear.
7. If a massive rotator cuff tear separates from its attachment site and retracts, the muscle
begins to atrophyand if left unrepaired, after six months, the possibility of a repair is less
likely to be successful.
8. Rotator cuff repairs can be performed with open or arthroscopic techniques with similar
resultsobtained depending on the training and experience of the surgeon.
9. After a rotator cuff is repaired, the time to heal and have good return of function depends on
the size of the tear, quality of the tendon and bone density where the suture anchors are
placed (greater tuberosity footprint), and age of the patient. The repaired tendon has to take
root on the repair site and this takes about 4 months on average to occur.
10. How aggressive therapy is performed after surgery should take into account the size of the
rotator cuff tear, the quality of the tendon, the quality of the bone, and the amount of
tension on the repair which depends on how long a cuff tear was retracted prior to being
repaired. If pain is felt during exercises after a rotator cuff repair, it is an indication that
therapy is too aggressive and the exercises should be curtailed.
Biceps Tendon
The biceps muscle has two tendons of origin. One begins on the very top of the glenoid and the other originates on the coracoid bone of the shoulder blade (shown above). The biceps muscle serves to bend the elbow and rotate the forearm in a palm up position. When aproximal biceps tendon rupture occurs, it is typically the long head of the biceps tendon that comes off of the glenoid bone/labral junction. This tendon tear occurs with increasing age and activityand oftentimes occurs with a minor exertion. This is because as the long head tendon travels through the humeral groove called the bicipital groove, and is constantly having the humeral bone slide past it back and forth with arm motion, and in time, depending on the shape of the groove, it can cause the tendon to abrade and partially tear until a complete rupture is experienced. When the long head of the biceps tendon tears, a sudden pop in the shoulder is felt, followed by discoloration of the upper arm called echymoses, muscle spasms of the upper arm and the appearance of a bulge in the mid arm called a popeye muscle. Because there are two tendon origins of the biceps muscle, the lack of the long head of the biceps rarely causes a functional deficit and repair is normally not recommended.
Treatment
Arthroscopic Shoulder subacromial decompression and rotator cuff repair
Reverse Total Shoulder Prosthesis for massive irreparable rotator cuff tears
Impingement syndromes as a result of bursitis, tendonitis, androtator cuff tears that fail a non-operative3-6 month trial of activity modification, anti-inflammatory medication, Steroid injections, and a good therapy program are considered for surgical intervention. Surgery most often involves an arthroscopic procedure that removes the inflammatory bursa, partial tendon tears and acromial bony spurs that contributes torotator cuff tears. When a rotator cuff tear is present, it is repaired at ROC arthroscopically in all cases. Open Rotator cuff repairs are still performed by many competent surgeons but the rehabilitation, discomfort from surgery and scars from an open approach makes the arthroscopic method our preferred method. If a massive rotator cuff is irreparable and the patient is unable to elevate their arm overhead causing a significant functional deficit, is otherwise healthy and older than 65 years of age, a new technique using a reverse shoulder prosthesis is considered which uses the deltoid instead of the rotator cuff to power the arm to elevate to near normal ranges. (see section on arthritis)
Biceps tendon rupturesat the shoulder level most often occurs at the bicipital groove. When a spontaneous rupture causes persistent pain and muscles spasms in the midarmafter non-operative treatment has been donefor at least six months, surgery which buries the tendon stump in the bicipital groove or is tied to local soft tissues, called a biceps tenodesis is recommended. This procedure can be done through a small open incision or through the use of thearthroscope during an acute tear but a larger incision is used if it is a tear that occurred longer than 2-4 weeks. When repairing a rotator cuff during a routine arthroscopic procedure and a near complete biceps tendon tear is inadvertently found, a biceps tenodesis is often also performed at the same setting through the arthroscope.