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Impingement: Primary

Impingement of the tendinous portion of the rotator cuff as it passes under the coracoacromial arch is a classic cause of rotator cuff injury. The impingement syndrome, as originally described by Neer, encompasses a spectrum of pathologic changes involving the rotator cuff and associated bony changes within the coracoacromial arch, affecting primarily those 40 years of age and older.

When impingement-type symptoms present in a younger population, great care must be taken to avoid over-diagnosing and over-treating as the impingement may be internal or secondary to instability, which effectively moves the cuff closer to the arch . Middle-aged to older patients presenting with impingement symptoms are generally recreational overhand athletes or individuals whose occupation requires repetitive, forceful overhead work.

These patients present with chronic, low-level shoulder pain that is exacerbated with overhead activity or motions that necessitate internal rotation of the humerus in the abducted position, such as reaching behind a car seat. The pain usually localizes to the anterosuperior shoulder with radiation into the deltoid insertion region, following the course of the underlying bursa and capsule. Frequently, the primary reason for presenting to the orthopaedic surgeon is sleep disturbance.

Treatment of impingement syndrome is patient specific. After the diagnosis has been made, the varying degrees of pathology and patient expectations must be considered. To assist in developing a treatment plan, Neer  described the three stages of rotator cuff involvement:

Stage 1: reversible edema and inflammation;

Stage 2: tendon fibrosis and chronic inflammation, a stage that has been further subcategorized  into Type 1 without a cuff tear and Type 2 associated with a partial thickness tear; and

Stage 3 complete fiber failure with a full thickness tear. Knowing the status of the rotator cuff is critical in making therapeutic decisions.

If impingement is diagnosed, the initial treatment should be conservative. Great care should be taken to evaluate the scapula and to diagnose any associated dyskinesia. In addition to proper activity modification, physical therapy exercises can be of great benefit, focusing not only on rehabilitating the rotator cuff musculature, but also on re-establishing a full, pain-free range of motion and normal scapulo-thoracic rhythm and strength.

The net effect of a proper rehabilitation program should result in decreased inflammation and thickening in the subacromial space as well as an increase in the interval between the humeral head and acromion.

The younger overhand athlete with impingement-type pain should be carefully examined for a functional loss of internal rotation. A tight posterior capsule tends to shift the humeral head in a posterior-superior direction leading to rotator cuff symptoms. By simply stretching the posterior capsule using the “sleeper” stretch, resolution of symptoms can often be achieved in this population of patients.

Nonsteroidal anti-inflammatory medication is appropriate to assist in decreasing associated soft tissue swelling while, on occasion, the judicious use of a steroid can be very helpful when introduced into the subacromial space.

For those who fail conservative care, surgery may be appropriate. Most patients who respond to a nonoperative program will do so within a six-month period. If surgery is indicated, an MRI may prove useful to determine whether or not there is concomitant significant cuff pathology. If the cuff is intact, a simple subacromial decompression should be performed.

If the impingement has resulted in associated cuff tearing, the tear may need to be repaired in addition to the decompression.In the properly selected patient, the results of subacromial decompression have been reliable and durable. Although there are several described surgical techniques for subcromial decompression, the “cutting block” approach may be the most reliable with regard to referencing the final result against known anatomic guide-lines. Furthermore, pre-operative planning should include the shape and width of the acromion such that over or under-resection is avoided.

Subacromial decompression has become one of the most common procedures performed by the orthopaedist, and although a success rate of nearly 90% has been reported for isolated decompressions, a word of caution is warranted. Failures can and do occur. Authors have reported failure rates ranging from 5% to 40%. Despite appropriate treatment, complications and unsatisfactory results can occur.

When a failed acromioplasty is encountered, it is incumbent upon the treating surgeon to invoke a systematic, thorough analysis of the failed acromioplasty. The work-up should attempt to answer the follow questions:

Was the initial diagnosis correct?

Was the appropriate operation chosen?

Was the procedure performed technically correctly?

Was associated pathology recognized? Was the postoperative rehabilitation timely and appropriate?

As these questions are answered during the re-evaluation, the cause for failure can be established and categorized as initial diagnostic error, treatment failure, or a complication of treatment, and then appropriately treated.

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