The Measurement of Subacromial Contact Pressure in Patients with Impingement Syndrome
abstract & commentary
Synopsis: Impingement syndrome of the shoulder has a complex and, at times, unclear pathogenesis.
Source: Nordt WE 3rd, et al. The measurement of subacromial contact pressure in patients with impingement syndrome. Arthroscopy 1999;15(2):121-125.
Twenty-five patients who underwent an arthroscopic subacromial decompression and acromioplasty for impingement syndrome after failing conservative care were evaluated postoperatively by the UCLA scoring system. The morphology of the acromion was also assessed radiographically. Perioperatively, a catheter was placed beneath the anterior component of the acromium under arthroscopic visualization, and contact pressures were recorded through a normal arc of motion. Mean pressure was recorded, and the results were statistically evaluated. Mean pressures prior to acromioplasty were measured at 0°, 90°, and 180° of abduction as well as hyperabduction (which was defined as force-passive abduction to the maximum) and cross-arm adduction. All five measurements diminished significantly following the decompression.
At 90° of abduction, pressure always decreased with internal rotation and always increased with external rotation. Maximum contact pressure developed in either hyperabduction or cross-arm adduction in all patients except two. In general, the preoperative findings of maximum impingement pain generally correlated with the position of maximum contact pressure.
Nordt and colleagues concluded that while acromioplasty significantly decreases anterior edge subacromial contact pressures, the correlation between symptoms and acromium type appears to be much more complex. They also concluded that there are at least two types of impingement pathogenesis according to arm position and rotator cuff contact pressure and that further evaluation is necessary to increase our understanding of this complex process.
Comment by James P. Tasto, MD
Impingement syndrome has become a popular diagnosis in the hands of orthopedists, as well as those dealing with musculoskeletal problems in general. We have found over the last few years that it is a condition that is grossly overdiagnosed. It has become the most common shoulder diagnosis entering the sports medicine physician’s office. Many of these patients have rotator cuff tears, partial or complete; acromioclavicular joint pathology; subtle glenohumeral instability; or, in many cases, an early adhesive capsulitis. Therefore, before a surgical procedure is to be recommended to a patient, the conservative management symptoms should have failed and specific physical examination criteria must be met.
The greatest error that we see as consultants in the field of orthopaedics is the early frozen shoulder syndrome being diagnosed as an impingement syndrome. The classical definition by Neer mandates that the patient have an almost full range of motion before this diagnosis can be made.1 He also implicated the anterior edge of the acromium as the causal factor in impingement pathology.
This study points out a unidimensional analysis of contact pressure only and does not take into consideration other factors such as sheer forces and other causes of pain such as bursitis, which can be intrinsic to any type of cuff tendonapathy. Surgically, we have always concentrated on removing the anterior component of the acromium, but we should also pay close attention to the lateral acromial morphology, which can also be an important factor in increasing contact stresses. The cause of residual pain in patients after an apparently adequate subacromial decompression can be difficult to define. Scarring or intrinsic changes within the cuff may be the cause. Nordt et al clearly point out that subacromial pressure may not directly correlate to acromial morphology. They also point out that rotator cuff contact on the acromium in the position of hyperabduction, as well as cross-arm adduction, may each represent a different pathogenesis. In this study, a cross-arm adduction test, generally thought to be indicative of acromioclavicular joint pathology, did generate high subacromial pressures. Findings of supraspinatous partial cuff tears were quite consistent in the group that had increased pressure with hyperabduction. It is also to be noted that these studies were done with active range of motion rather than passive range of motion, which does not adequately simulate the clinical condition in the functionally active patient.
Shoulder pain that falls within the general diagnosis of impingement syndrome continues to be an intriguing diagnostic dilemma. As in other areas, such as the patellar tendon and the Achilles tendon, osseous encroachment is not a factor, and pain is often the result of microtears and degradation of the tendon itself. Further studies in this area, as well as further improvement in our diagnostic skills, are imperative to formulate an appropriate treatment program for many of these patients.
Suggested Readings
1. Neer CS. Anterior acromioplasty for the chronic impingement syndrome in the shoulder: A preliminary report. J Bone Joint Surg Am 1972;54:41-50.
2. Neer CS. Impingement lesions. Clin Orthop 1983; 173:70-77.
3. Rockwood CA, Lyons FR. Shoulder impingement syndrome: Diagnosis, radiographic evaluation, and treatment with a modified Neer acromioplasty. J Bone Joint Surg Am 1993;75:409-494.
4. Hawkins RJ, Kennedy JC. Impingement syndrome in athletes. Am J Sports Med 1980;8:151-158.
5. Bigliani LU, et al. The relationship of acromial architecture to rotator cuff disease. Clin Sports Med 1991; 10:823-838.
You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
- Award-winning Medical Content
- Latest Advances & Development in Medicine
- Unbiased Content