Functional Evaluation of the Ligaments at the Acromioclavicular Joint during Anteroposterior and Superoinferior Translation

Abstract

We examined the anatomy and measured the in situ force in ligaments at the acromioclavicular joint using a universal force-moment sensor. The in situ force in the coracoacromial, conoid, trapezoid, superior acromio clavicular capsular, and inferior acromioclavicular cap sular ligaments of 10 fresh-frozen cadaveric shoulders was determined for a load of 70 N applied to the clavicle in anteroposterior and superoinferior direc tions. The lengths of the conoid and trapezoid liga ments were found 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, respec tively. The in situ force of the trapezoid (42.9 ± 15.4 N) was significantly greater than that for the other liga ments during posterior displacement. Otherwise, no statistically significant differences could be found be tween any of the in situ forces in each ligament during all other motions examined. During anterior displace ment, the inferior acromioclavicular capsular ligament appeared to be the major restraint. The trapezoid lig ament was the primary restraint during posterior dis placement and provided 55.8% ± 20.0% of the resist ing force. Our results suggest that the coracoclavicular and other acromioclavicular joint capsular ligaments should be considered for reconstruction to restore normal joint function, especially in the anterior, poste rior, and superior directions.