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Impingement syndrome: Diagnostic approaches have increased accuracy and treatment options
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Impingement syndrome is a term frequently used by orthopedic surgeons. It means different things to different surgeons and their approaches to the treatment and surgery for this condition have varied over the years. Based on the work of Charles S. Neer II, MD, many surgeons have accepted that an osteophyte or variation in the shape of the undersurface of the acromium often requires surgery to relieve “impingement symptoms.”
For this month’s 4 Questions interview, I asked Winston J. Warme, MD, to give his perspectives based on work done in his department.
Douglas W. Jackson, MD
Chief Medical Editor
Douglas W. Jackson, MD: How was the diagnosis of “impingement syndrome” made clinically? What did it mean in the past?
Winston J. Warme, MD: Dating back to Neer’s classic article in 1972, the term “impingement syndrome” has been widely used to describe the entire spectrum of rotator cuff and subacromial conditions, including cuff tendinosis, partial and complete tears, acute and chronic subacromial bursitis, as well as calcific tendinosis, which were not clearly differentiated on clinical examination nor with plain radiographs.
The diagnosis of impingement syndrome was often made with Neer’s and Hawkin’s signs, which we now know have very low specificity, 36% ± 22% and 41% ± 19%, respectively. Neer’s test also has been shown to be a rather imprecise diagnostic test, as the medication reached the subacromial space between 60% and 100% of the time, but also reached other structures in as many as 63% of the cases. Additionally, these tests are also positive in patients with glenohumeral internal rotation deficit or posterior capsular tightness — further delineating their lack of specificity.
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Jackson: What has changed in regards to our understanding of the coracoacromial (CA) arch?
Warme: We have learned from the high-level studies we reviewed that the acromion, including the various shapes seen on outlet radiographs, has not been shown to be the cause of rotator cuff tears as had been previously speculated. The spurs commonly seen on imaging studies are enthesophytes within the CA ligament (CAL). There is contact between the cuff and CA arch in the normal shoulder, and this construct serves as a restraint to upward displacement of the humerus.
Diederichsen and others have detected mechanoreceptors within the CAL. In live subjects, they were able to show that when electrically stimulated, the Ruffini and Pacini bodies sent afferent signals that resulted in reflex inhibition of voluntary shoulder muscles. These findings suggest that the mechanoreceptors within the CAL may play a role in muscular coordination and functional shoulder joint stability.
Finally, therapeutic measures that do not alter the CA arch or the shape of the acromion are as effective as acromioplasty in the treatment of disorders lumped under the moniker of impingement syndrome. We should not forget the admonition of Ernest A. Codman, MD, that ‘‘the coracoacromial arch has an important duty and should not be thoughtlessly divided at any operation.’’
Jackson: What and how has new technology helped sort out rotator cuff pathology and/or CA arch pathology to allow orthopedic surgeons to be more specific in our diagnosis?
Warme: In the ensuing 4 decades, our diagnostic armamentarium has grown to include digital radiographs, ultrasound and MRI, which greatly increase our diagnostic accuracy and enable us to provide appropriate treatment for specific diagnoses. Additionally, our more sophisticated approach to scientific inquiry and the advent of evidence-based practice allow us to differentiate high level studies that should change our practice from “expert opinion” that may have limited value.
Jackson: What are your current indications for the commonly performed acromioplasty? What can the patient expect in terms of outcomes when it is performed?
Warme: We do not change the morphology of the CA arch or acromion in any way when performing cuff repairs. At this point, we only modify the undersurface of the acromion if it is misshapen from trauma, such as in cases of a malunion, or it there is an abnormal growth on it such as an osteochondroma. These cases are exceedingly rare.
Another unusual condition is a symptomatic os acromiale which, if small, is excised arthroscopically leaving the deltoid attachment intact. These cases are infrequent and can have associated cuff conditions that make their outcomes more related to the tendon healing than the bone modification.
- Winston J. Warme, MD, can be reached at University of Washington Medical Center, Department of Orthopaedics and Sports Medicine, 1959 NE Pacific St., Box 356500, Seattle, WA 98195; 206-543-3690; fax: 206-685-3139; email: warmewj@u.washington.edu.
- Disclosure: Warme has no relevant financial disclosures.