FUNCTIONAL-EVALUATION OF THE LIGAMENTS AT THE ACROMIOCLAVICULAR JOINTDURING ANTEROPOSTERIOR AND SUPEROINFERIOR TRANSLATION

We examined the anatomy and measured the in situ force in ligaments at the acromioclavicular joint using a universal force-moment sensor. Th e in situ force in the coracoacromial, conoid, trapezoid, superior acr omioclavicular capsular, and inferior acromioclavicular capsular ligam ents of 10 fresh-frozen cadaveric shoulders was determined for a load of 70 N applied to the clavicle in anteroposterior and superoinferior directions. The lengths of the conoid and trapezoid ligaments were fou nd to be 15.1 +/- 4.1 and 11.5 +/- 2.2 mm, respectively; the widths of the conoid and trapezoid ligaments were 10.7 +/- 1.5 and 11.0 +/- 2.8 mm, respectively. The in situ force of the trapezoid (42.9 +/- 15.4 N ) was significantly greater than that for the other ligaments during p osterior displacement. Otherwise, no statistically significant differe nces could be found between any of the in situ forces in each ligament during all other motions examined. During anterior displacement, the inferior acromioclavicular capsular ligament appeared to be the major restraint. The trapezoid ligament was the primary restraint during pos terior displacement and provided 55.8% +/- 20.0% of the resisting forc e, Our results suggest that the coracoclavicular and other acromioclav icular joint capsular ligaments should be considered for reconstructio n to restore normal joint function, especially in the anterior, poster ior, and superior directions.