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THE PAINFUL SHOULDER Dr. Aubrey Smith’s article in Panhandle Health The knowledge of the causes of pain about the region of the shoulder has expanded quite impressively over the last 20 years. Interestingly, considerable understanding of the shoulder existed many years before surgical and conservative management of painful shoulder problems was commonly available. As with many developments in medicine, the original thoughts on the causes for pain about the shoulder were not widely accepted. Refuted by his peers, E. A. Codman was one of the first physicians to recognize that the tendons that are most intimately associated with the ball and socket joint of the shoulder may become detached due to wear and tear and cause immense discomfort (1). His early attempts at surgical repair were mixed with considerable success. It was not until 40 years later that the world of medicine was convinced that a common cause of pain about the shoulder had a solution. In 1972, Charles Neer described what is now accepted as the most common cause of pain in the shoulder, Impingement Syndrome (2). There are many other causes of a painful shoulder that must be considered when the diagnosis of Impingement Syndrome is entertained. As well, the Impingement Syndrome encompasses a considerable array of diagnoses that must be correctly differentiated in order to obtain a consistently successful result from treatment. The shoulder should be thought of as a golf ball on a tee that is encompassed by 4 tendons that keep the golf ball always located on the tee. Above the joint is located a roof. The tendons that keep the golf ball on the tee are known as the rotator cuff. The bone that makes up the roof is known as the acromion. The wing bone, or scapula, is attached to the rest of the skeleton by way of the clavicle. Interestingly, the attachment is to the acromion. Anything that interfered with the normal relationship of these anatomic structures can be responsible for pain around the shoulder and may aggravate or cause an impingement of the humeral head against the acromion. This leads to a painful syndrome that when untreated may lead to a tear of the rotator cuff. Once the rotator cuff tears, the pain is accomplished by weakness in arm elevation that usually worsens with time. If a painful rotator cuff tear is left untreated, some cases will go on to develop an arthritic condition of the glenohumeral relationship that is difficult to treat. Impingement syndrome is a presentation of the same resulting disease process at different stages. In pathological circumstances, as the arm is repeatedly elevated, the tendons of the rotator cuff have an excessive pressure exerted upon them. Over time, this leads to an interruption in the usual flow of the activities of daily living. As the syndrome worsens, the pain becomes so severe that the patient awakens at night and may develop doing his or her job. If untreated and undiagnosed, the patient may develop a chronic pain problem. Depression is not uncommon after many months of pain without relief. The key to successful treatment is an early and accurate diagnosis of the actual reason for the impingement. The most common cause for impingement is a prominent anterior acromion. Cadaver studies have led to the description of three different types of an acromion. In the cadavers that were noted to have a tear of the rotator cuff, the acromion was very prominent and had a leading edge that hung down. This overly abundant bone has more of a tendency to run the top of the humeral head and thus the rotator cuff as the arm is repeatedly elevated. Interestingly, the cadavers that had no tears of the rotator cuff uniformly had a small flat acromion. As a rule, the cadavers with the biggest rotator cuff tears had the most prominent anterior acromion as a rule. Knowing that the shape of the acromion had a great deal to do with the development of symptoms is helpful when viewing the transacromial "Y" x-ray of the shoulder. The history of the patient’s occupation is also helpful. Repeated use of the arm above the head leads to an exacerbation of symptoms at an earlier age. It is probably true that sedentary people with mildly prominent acromion might never develop symptoms or develop symptoms much later than the patient that does heavy work that has the same prominence of the anterior acromion. Arthritis of the acromioclavicular joint can be painful by and of itself. However, if a large spur of bone protrudes under this joint from arthritis, this can create impingement. This condition may coexist with or exist independent of a prominent acromion. Other bony structures in the area, such as the greater tuberosity of the humeral head can lead to impingement. As unfused anterior acromion from childhood can be symptomatically painful. Irregularities in bony surfaces from old fractures may lead to the development of the impingement syndrome. There are several other actual causes that are more rare. The diagnosis of impingement requires an accurate assessment of the anatomic reason behind it in order to have success with treatment. The diagnosis of whether impingement is the cause for the pain in the shoulder is based upon not only the history and physical, but a crucial test whereby Lidocaine is injected into the subacromial bursal tissue (3). If a great deal of the patient’s pain is relieved by this procedure, greater confidence in the diagnosis can be given. Failure to relieve a vast percentage of the patient’s pain with this Lidocaine "impingement test" must lead the physician to seek another diagnosis for the patient’s shoulder pain. The differential diagnosis for shoulder pain is quite large (4,5). Cervical disc disease is a common disorder that may cause shoulder and upper extremity pain. As well, cervical disc disease may coexist with the impingement syndrome making the diagnosis all the more confusing and difficult to elaborate. Entrapment of peripheral nerves in the upper extremity may mimic impingement and vice versa. Impairment of the suspensory mechanism of the scapula as in "winging" from long thoracic nerve palsy or other cause can lead to impingement. True arthritis of the glenohumeral joint is very, very rare without a longstanding rotator cuff tear but must be considered in the differential. Tumors of the chest wall, upper thorax, and bones of the shoulder must be kept in mind. Thoracic outlet syndrome is particularly elusive diagnosis that may be responsible for pain in the shoulder and entire upper extremity. Biceps tendinitis must be kept in mind as the diagnosis of impingement is entertained. The long head of the biceps travels up the humerus, through the bicipital groove, directly under the acromion, and attaches to the glenoid. Tendinitis of the biceps almost always is an additional component of the impingement syndrome. It should be noted that the literature strongly suggests that treating biceps tendinitis as a separate entity often results in a poor outcome. Rupture of the biceps is a tipoff that the rotator cuff is torn and the impingement syndrome exists. It should be noted that this condition can exist without the impingement syndrome, but is likely due to traumatic event if so. Throwers can develop a very bad case of biceps tendinitis but this usually is still a manifestation of impingement. Instability of the shoulder, especially inferior and anterior type instability that is not related to previous dislocation, may be responsible for symptoms that mimic impingement. If fact, this type of instability may actually cause impingement. Treating instability should be the primary goal of intervention. Failure to recognize that instability exists may lead to a failed treatment course. Frozen shoulder, or adhesive capsulitis, may cause pain that is associated with, related to, or a result of impingement from other causes. Frozen shoulder is characterized by lack of movement both actively and passively. When adhesive capsulitis exists, the reason must be established why it is present. If impingement has caused it, it may be impossible to treat the adhesive normal motion of the shoulder before any intervention surgically is entertained. In cases of adhesive capsulitis existing with a tear of the rotator cuff, if motion passively can not be made reasonably normal first, then operative intervention will be followed by and immense post operative rehabilitation challenge. Treatment should be given only after an accurate diagnosis of not only whether impingement exists, but for what reason. During the work up, most often an arthrogram is ordered. This is to rule out a tear of the rotator cuff. Conservative measures are much less likely to be of benefit if the rotator cuff is already torn. In younger patients and arthrogram may not be necessary. Once the diagnosis is firm, treatment can begin with nonsteroidals and gentle exercises. The exercises should be mostly stretching into internal rotation and strengthening of the shoulder external rotators. It is a mistake to give the patient a blanket order for physical therapy, as vigorous exercise will make the problem worse. If there is no tear of the rotator cuff, prudent and careful use of steroid injections into the subacromial space can be of benefit. Multiple injections of steroids should be avoided and in the author’s opinion, should be avoided completely in cases whereby a rotator cuff tear is documented. In cases of failed conservative modalities, surgery may be the only solution to the problem (4,5). It is reasonable to assume that if the patient is getting no better or worsening after several months of conservative treatment, surgery needs to be considered. The surgical intervention should be directed at solving the anatomic reason for the impingement. As well, if surgery is considered, the rotator cuff should be studied prior to surgery to determine if a repair will be necessary. Recovery from an operation for impingement is usually tenfold easier than recovery from the same operation accompanied by a rotator cuff repair. Delay in operative intervention in cases whereby symptoms are worsening in spite of ordinary measures will often lead to further damage to the rotator cuff. Not all patients with rotator cuff tears will need an operation. Interestingly, most patients that have incapacitation pain from impingement syndrome will develop a rotator cuff tear is untreated. However, not all patients that have rotator cuff tear have incapacitating pain. Indeed, some patients are pain free and have only weakness in elevation of the arm as a symptom. This of course leads to further confusion about an already difficult situation. Pain is and should always be the major criteria for consideration of surgical intervention. If a patient does not suffer from pain, the operative intervention is most likely not worth going through. Recovery after massive tears of the rotator cuff can take many months or even a year. Once an operation is considered, the type of operation must be decided upon. If impingement syndrome exists without a tear of the rotator cuff, the anatomic reason for the impingement should be removed. In most cases, the reason for impingement is the anterior prominent acromion. Most authorities agree that the rotator cuff begins to tear, usually, from inside the shoulder joint. Arthroscopy provides access to viewing the inside of the shoulder joint. In cases where the rotator cuff is damaged badly and is torn more than 50%, it should be repaired because it is in imminent danger of rupture. Whatever the status of the rotator cuff, the cause for impingement must be corrected. Controversy exists about the methods of removing the prominent anterior acromion. The procedure that has proven the test of time and remains the standard, which is currently unsurpassed regarding successful outcome, is an open acromioplasty. Several techniques are available as described by various authors; however, unsurpassed ability to see the pathology and address other anatomic reasons that may be overlooked using more conservative alternatives exists with an open operation. The results from arthroscopic acromioplasty have been good. Some studies have reported results that approximate that of an operation. It is safe to say that many investigations are on going and some studies of the past have demonstrated very satisfactory results with all arthroscopic surgery(6). In more recent years, most surgeons do the decompression operation arthroscopically. Other causes of shoulder pain often need to be addressed surgically as well. Arthritis of the acromioclavicular joint occasionally necessitates removal of the distal end of the clavicle. Shoulder instability problems that mimic impingement syndrome that fail conservative modalities should be addressed with an operation that addresses the instability. The impingement will often resolve as the cause for the instability is removed. It is interesting that one cause for failure of the operation for impingement is failure to address a primary shoulder instability problem initially. Impingement syndrome does indeed encompass a considerable array of diagnoses. When properly treated, the results are uniformly good to excellent in most cases. Knowledge continues to expand in this aspect of Orthopaedic Surgery and investigation continues to provide more options for treatment. As long as the correct diagnosis is made, the treatment is likely to be successful. Codman, E.A.: The Shoulder, Boston, Thomas Todd, 1934. Neer, C.S.: Anterior Acromioplasty for the Chronic Impingement Syndrome of the shoulder. Journal of Bone and Joint Surgery. 54A: 41, 1979. Brown, J.T.: Early assessment of supraspinatus tears: Procaine infiltration as a guide to treatment. Journal of Bone and Joint Surgery. 31B: 423-425, 1949. Neer, C.S.: Shoulder Reconstruction, W.B. Saunders Co. 1990. Rockwood and Matsen: The Shoulder, W.B. Saunders Co. 1990. Iannotti, J.P.: Rotator Cuff Disorders, American Academy of Orthopedic Surgeons Monograph Series, 1991.
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