Glenohumeral kinematics and capsule-ligamentous strain resulting from laxity exams

Objective. Identification and quantification of strain in shoulder capsular -ligamentous structures during clinical exams and validation of this testin g on cadavers. Methods. Mercury strain gauges were sutured in seven locations on shoulders from cadavers. An electromagnetic tracker quantified humeral head translat ions during laxity exams. Strain and humeral position were acquired during performance of Sulcus, Feagin, Apprehension, Load and Shift, Drawer, and Ha wkins tests. Results. Anterior humeral head translation in neutral position was primaril y constrained by the coracohumeral ligament. With the arm abducted, anterio r middle and inferior ligaments also became active. External rotation and a bduction activated inferior and middle capsules. Posterior capsule constrai ned motion for posterior tests in neutral and abduction. Superior and infer ior capsular ligaments were active during inferior tests in neutral positio n. With abduction, inferior ligaments provided primary translation constrai nt. Conclusion. Study of kinematics and strain evaluation on cadavers can yield useful information on mechanisms of glenohumeral instability.