["Rotator interval" lesion. Part 2: Biomechanical study].
Motion analyses by a NAC Selgraph, electromyographic examination and measurement of intraarticular pressure during shoulder elevation were done in this study. Abnormal patterns during shoulder motion were analysed and compared with normal patterns. Results are as follows; A "floating phenomenon" in which the scapula adducts as soon as the arm elevates and then begins to abduct disappears in cases with "rotator interval" lesion: the scapula abducts immediately when the arm elevates. Disappearance of the "floating phenomenon" depends on higher activity of the upper trapezius observed in EMG. Anterior and middle fibers of the deltoid are highly active in normal individuals. At arm elevation of 110 degrees the upper trapezius joins the activity. On the other hand, it is the upper trapezius that mainly acts in cases with "rotator interval" lesion. The intra-articular pressure in the early phase of arm elevation depends on the opening of the "rotator interval" and on the abduction of the scapula. Abnormal patterns of should movement in cases with "rotator interval" lesion are almost normalized after surgery.
D000293:Adolescent; D000328:Adult; D001696:Biomechanical Phenomena; D002648:Child; D004576:Electromyography; D005260:Female; D006801:Humans; D008297:Male; D008365:Manometry; D009068:Movement; D012540:Scapula / Q000502:physiology; D012785:Shoulder Joint / Q000502:physiology*; D013710:Tendons / Q000502:physiology