UNDERSTANDING ORTHOPAEDICS IMPINGEMENT SYNDROME
Consultant Orthopaedic Surgeon, Bombay Hospital Specialist in Joint Replacement and Reconstruction
The awareness of shoulder problems is increasing day by day. Lay people as well as the physicians are realising that not all painful shoulders are frozen shoulders. Entities such as impingement syndrome which we will discuss here, acromioclavicular arthritis, rotator cuff tears, glenohumeral osteoarthritis and glenohumeral instability are increasingly being recognised and treated.
Let us see what is impingement syndrome of the shoulder, how it is diagnosed and how best to treat it.
A brief knowledge of anatomy of the shoulder region is necessary to understand impingement syndrome. The shoulder blade or scapula articulates with the head of the humerus forming the glenohumeral joint. Glenoid is the saucer shaped cavity on the shoulder blade. Clavicle articulates with the acromion on the lateral side and the sternum on the medial side. The coracoid process is a hook shaped projection on the anterior aspect of the scapula which is attached to the acromion and the clavicle with ligaments (Figs. 1 and 2).
Fig. 1 : Fig. 2 :
We all know that the deltoid muscle is the prime abductor of the shoulder joint which is the superficial muscle that arises from the outer borders of the clavicle and the scapula. Underneath the deltoid arising from the flat surfaces of the scapula are the muscles of the rotator cuff namely the subscapularis, the supraspinatus, the infraspinatus and the teres minor. These are so called because they rotate the humeral head - the subscapularis internally and the rest externally. Supraspinatus is an important muscle which helps in the initiation of abduction of the shoulder. One other important function of the rotator cuff is todepress the humeral head during abduction.
DEFINITIONImpingement syndrome is a condition in which there is impingement (mechanical surmountable obstruction) between the coracoacromial arch and the contents of the subacromial space (rotator cuff, subacromial bursa, long head of biceps tendon) during abduction of the shoulder. The coracoacromial arch consists of the coracoid process, the acromion and the coracoacromial ligament. This condition was often described as the painful arc syndrome but Charles Neer has provided the modern definition and understanding for this condition.
Charles Neer has described the pathology as
Stage 1 occurs in individuals younger than 25 years and is reversible at times even without treatment.
Stage 2 occurs in individuals between 25 and 40 years and may still respond to conservative treatment. (physio, steroid injection etc.). At times in this stage surgery may be necessary.
Stage 3 generally requires surgery such as anterior acromioplasty with or without cuff repair. acromioplasty involves resection of such areas of bone from the anterior aspect of acromion and clavicle so that the impingement is relieved.
The classical symptom is pain. The intensity and its occurrence varies according to the stage of the disease. In stage 1 the pain is intermittent, in Stage 2 the pain is regular and in stage 3 the pain is constant. It is typically felt just beneath the anterior acromion during certain positions of the shoulder. The pain is felt typically during the mid-range of abduction of the shoulder. After the rotator cuff is torn the pain is more or less constant and is also felt at rest.
Impingement injection test involves injecting lignocaine into the subacromial space to see whether that relieves the pain. If it does the site of pathology is confirmed as the subacromial space. In earlier stages, the injection of lignocaine is often mixed with a long acting steroid to act as a definitive treatment for the impingement syndrome.
DIFFERENTIAL DIAGNOSISExtrinsic causes of shoulder pain should also be kept in mind notably pain from the cervical spine, sub-diaphragmatic pathology, at times cardiac cause when the left shoulder is painful.
Intrinsic causes can be glenohumeral instability, calcific tendinitis, AC arthritis, adhesive capsulitis, RA, glenohumeral OA, neoplasm etc.
X-rays may show spurs, osteophytes, cystic changes near the greater tuberosity and in later stages there will be upward migration of the humeral head. USG and MRI can localize the pathology. A recent advance is to a Dynamic MR with the abducted position of the shoulder.
TREATMENTThe treatment can consist of NSAIDs, rest, local heat, avoidance of activities that increase pain, physiotherapy, steroid injection in the subacromial space and in refractory cases anterior acromioplasty with subacromial decompression with or without rotator cuff repair. These procedures can be done open or through the arthroscope.
Not all shoulders with impingement syndrome need surgery. The majority will respond to conservative measures. Not all rotator cuff tears need treatment as the incidence of age related cuff tears is high. Only when the shoulder is symptomatic enough treatment should be instituted.