title: [Biomechanical investigations for the development of a SLAP-II-lesion].
abstract: The superior labral-biceps-tendon-complex forms an anatomical and functional unit and combines static and dynamic elements of shoulder stability. At present, only theoretical hypotheses exist on the etiology of the microtraumatic SLAP-II-lesion. To gain further insight into this, an instrument was developed to simulate throwing motions such as the late-cocking/early acceleration phase as well as deceleration/follow-through. Sixteen freshly frozen shoulder specimens were tested, varying the loads on the biceps tendon (25 N, 50 N, 100 N) and the compression of the humeral head against the glenoid (25 N, 50 N, 80 N). Each shoulder had to run through a certain number of cycles during the particular phase of throwing. The tests were stopped after a SLAP-II-lesion was observed, or after a limit of 15,000 cycles. Every 1,000 cycles the results of the tests were checked arthroscopically. A SLAP-II-lesion developed in only 10% of the specimens during the acceleration/ late cocking phase whereas in the deceleration/ follow-through phase 83% developed such a lesion. According to our results, the deceleration/follow-through of the throwing motion seems to be responsible for creating microtraumatic SLAP-II-lesions. One reason is the loss of the centering function of the long head of the biceps tendon during total internal rotation, another is the increased posterosuperior translation of the humeral head in this position, which leads to a non-physiological contact, creating lesions in this area due to the large sheering forces.
authors.affiliation: Abteilung und Poliklinik für Sportorthopädie, Technische Universität, Munich.
authors.forename: T
authors.initials: T
authors.lastname: Vaitl
authors.forename: A
authors.initials: A
authors.lastname: Burkart
authors.forename: E
authors.initials: E
authors.lastname: Steinhauser
authors.forename: E
authors.initials: E
authors.lastname: Hohmann
authors.forename: A
authors.initials: A
authors.lastname: Imhoff
mesh_terms: D000054:Acceleration; D000328:Adult; D000368:Aged; D001265:Athletic Injuries / Q000145:classification / Q000503:physiopathology*; D001696:Biomechanical Phenomena / Q000295:instrumentation; D002358:Cartilage, Articular / Q000293:injuries* / Q000503:physiopathology*; D012090:Cumulative Trauma Disorders / Q000145:classification / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D016059:Range of Motion, Articular / Q000502:physiology*; D017006:Rotator Cuff / Q000503:physiopathology; D000070636:Rotator Cuff Injuries; D012783:Shoulder Dislocation / Q000145:classification / Q000503:physiopathology*; D000070599:Shoulder Injuries; D012785:Shoulder Joint / Q000503:physiopathology*; D013708:Tendon Injuries; D013710:Tendons / Q000503:physiopathology*; D016474:Weight-Bearing / Q000502:physiology