Ligament Mechanics During Three Degree-of-Freedom Motion at the Acromioclavicular Joint

Abstract
The development of effective treatment and reconstruction procedures for injuries to the soft tissues around the acromioclavicular (AC) joint relies on a comprehensive understanding of overall joint function. The objective of this study was to determine the magnitude and direction of the in situ forces in the AC capsular and coracoclavicular ligaments as well as the resulting joint kinematics during application of three external loading conditions while allowing three degree-of-freedom joint motion. A robotic/universal force-moment sensor testing system was utilized to determine the in situ forces in the soft tissue structures and the resulting joint kinematics. The clavicle translated 5.1±2.0, 5.6±2.2, and 4.2±1.9 mm during application of a 70 N load in the anterior, posterior, and superior directions, respectively, representing almost a 50% increase over previous studies using similar load magnitudes. In response to an anterior load, the magnitude of in situ force in the superior AC ligament (35±18 N) was found to be greater (pin situ force in the conoid (49±22 N) was significantly greater (pin situ force in the coracoclavicular ligaments with each loading condition, surgical procedures should reconstruct these ligaments in a more anatomical manner or treat them separately to prevent joint degeneration. © 2000 Biomedical Engineering Society. PAC00: 8719Rr, 8719Ff, 8719St, 8780Rb