Secondary Compressive Disease

Secondary Compressive Disease

Impingement or compressive symptoms may be secondary to underlying instability of the glenohumeral joint. Attenuation of the static stabilizers of the glenohumeral joint, such as the capsular ligaments and labrum from the excessive demands incurred in throwing or overhead activities, can lead to anterior instability of the glenohumeral joint. Because of the increased humeral head translation, the biceps tendon and rotator cuff can become impinged secondary to the ensuing instability. A progressive loss of glenohumeral joint stability is created when the dynamic stabilizing functions of the rotator cuff are diminished from fatigue and tendon injury.  The effects of secondary impingement can lead to rotator cuff tears as the instability and impingement continue.

Tensile Overload

Another etiological factor in rotator cuff injury is repetitive intrinsic stress overload. Heavy, repetitive eccentric forces borne by the posterior rotator cuff muscles during the deceleration and follow-up phases of overhead sports can lead to tendon overload failure. Pathological changes defined by Nirschl as "angiofibroblastic hyperplasia" occur in the early stages of tendon injury and can progress to rotator cuff tears due to ongoing stress overload. The investigation of Kraushaar and Nirschl, in a histological study of the extensor radialis brevis carpus, the primary tendon involved in lateral humerus epicondylitis, identified specific features inherent in an injured tendon. Based on their histopathological study, these researchers recommended using the term tendinosis, rather than tendonitis, to more precisely describe tendon injury. Histopathological studies of tendons taken from areas of chronic overuse in the human body do not show large numbers of macrophages, lymphocytes, or neutrophils. “Rather, tendinosis [sic] appears to be a degenerative process, characterized by the presence of dense populations of fibroblasts, vascular hyperplasia and disorganized collagen. Kraushaar and Nirshl noted that researchers don't know why tendinosis is painful, given the absence of acute inflammatory cells, or why collagen doesn't mature. In the biomechanical study of highly skilled throwers, the tensile stresses incurred by the rotator cuff during the arm deceleration phase of the throwing movement (to resist joint distraction, horizontal adduction and internal rotation) were approximately 1090 N. Acquired or congenital, capsular laxity and labial insufficiency can greatly increase the tensile stresses of the tendon units of the rotator cuff muscle. Macro traumatic tendon insufficiency

Unlike the rotator cuff classifications mentioned above, cases of macro-traumatic tendon insufficiency usually involve a previous or unique traumatic event in the patient's medical history. The forces encountered during the traumatic event are greater than the normal tendon can tolerate. Full-thickness rotator cuff tears, with bone avulsions of the greater tuberosity, can occur from single traumatic events. According to Cofield, normal tendon injuries do not occur easily because 30% or more of the tendon must be damaged to produce a substantial reduction in strength. Although the patient often reports a single traumatic event on subjective examination, resulting in tendon failure, repeated microtraumatic insults and degeneration over time may have created a substantially weakened tendon. The tendon eventually gave way under the heavy load described by the patient. Full-thickness rotator cuff tears require intensive surgical treatment and rehabilitation to achieve a positive functional outcome. 

Posterior or “Undersurface” Impingement

An additional cause for a lower surface rotator cuff tear in the shoulder of an athletic young man is called posterior, internal, or inferior impingement. This phenomenon was originally observed by Walch et al during shoulder arthroscopy with the shoulder positioned in the 90/90 position. By placing the shoulder in a position of 90 ° of abduction and 90 ° of external rotation causes the supraspinatus and infraspinatus tendons to rotate backwards. This more posterior orientation of the tendons aligns them so that the inferior surfaces of the tendons graze the posterior-superior glenoid labrum and pinch or compressed between the humeral head and the superior posterior glenoid border. Individuals who have Posterior shoulder pain caused by positioning the arm at 90 ° of abduction and 90 ° or more of external rotation, typically from elevated positions in sporting or industrial situations, can be considered as a potential candidate for inferior surface impingement. The presence of anterior translation of the humeral head. with maximum external rotation and abduction of 90, which was arthroscopically confirmed during the subluxation relocation test, it can produce mechanical friction and wear on the inferior surface of the rotator cuff tendons. The posterior deltoid can cause further damage if the rotator cuff is not functioning properly. The posterior deltoid angle of traction pushes the humeral head against the glenoid cavity and accentuates skeletal, tendon and labral injuries. Walch et al. Arthroscopically evaluated 17 throwing athletes with shoulder pain during throwing and found inferior surface impingement resulting in 8 partial thickness rotator cuff tears and 12 upper posterior lip injuries. Impact of the inferior surface of the rotator cuff to the posterior superior glenoid labrum may be a cause of painful structural disease in the overhead athlete.

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