Leshinger T, Wallwraff C, Muller C, Hackenbroch M, Bovenschulte H, Siewe J. Internal Impingement of the Shoulder: A Risk of False Positive Test Outcomes in External Impingement Tests. BioMed Research International 2017, P1-5.
The classification of the impingement of tissues of the shoulder joint complex has evolved into two major categories: external and internal. External impingement occurs when the soft tissues around the joint, primarily the rotator cuff, are pinched between the humeral head and the overlying acromion. Since the impingement occurs outside the joint capsule, the impingement is considered “external” in contrast to inside the joint. Internal impingement occurs when the compression of tissues occurs between the humeral head and the glenoid fossa. Multiple passive movement tests have been shown to create pain when external impingement is present. The purpose of this study was to determine if these same tests could re-create internal impingement (a false positive for external impingement).
The study utilized MRI images of the shoulder tissues in the position of the 3 common clinical test procedures. The MRI images of 37 healthy subjects (19 male, 18 female) were classified by the degree of impingement of the rotator cuff between the humerus and glenoid. A classification system of “0” when there was no contact, “1” when there is tissue contact without deformation, and “2” when cuff deformation was utilized. Assuming that deformation of the tendons would create pain in symptomatic patients, the authors concluded that the tests for external impingement compress tissues between the humerus and glenoid, therefore potentially producing false positive tests for external impingement. The supraspinatus showed the internal impingement during all three procedures, ranging from 8-13 percent of the subjects. The subscapularis showed impingement on 2 of the 3 tests ranging from 3 to 11 percent of the subjects. The infraspinatus tendon did not show any internal impingement on any of the tests.
The results of this study indicate that the tests will identify impingement when it is present (sensitivity), but may lack accuracy (specificity) for external impingement. Is this lack of test specificity bad? The lack of specificity is only bad if any non-surgical intervention depends on whether the impingement is external or internal. At Gray Institute®, the differentiation between external and internal impingement matters very little unless surgery is performed. The impingement is only a symptom. The goal of any movement-based intervention is to first identify where in the “Chain Reaction®” the parts of the system are not functioning normally. In physical therapy parlance the problem might be called an impairment in the system. But the truth of the body’s neuro-musculo-skeletal system is that the impairment is usually not where the symptoms are located. The symptom is not the cause!
The challenge in treating shoulder impingements is that the cause could be any where in the body. Reduced mobility or insufficient strength at the scapula-thoracic articulation, thoracic spine, hip joint, or ankle-foot complex could be the cause of shoulder impingement. To treat the cause, we must identify the cause(s). This can be overwhelming for any movement practitioner without an efficient system of examination that can assess how all these joints work together. The Gray Institute created the 3D Movement Analysis & Performance System (3DMAPS®) for this purpose.
3DMAPS® takes advantage of six global movements (driven by the legs, arms, and head) to identify in which plane(s) the body may not be moving optimally, and which joint(s) impairments might be the cause. Then the 3DMAPS® Performance System provides multiple strategies to resolve the impairments that are producing the shoulder impingement (whether external or internal). Treating the cause is essential to long-term resolution of symptoms, avoidance of surgery, and restoration of function!