Effect of coracoacromial ligament resection on glenohumeral stability under active muscle loading in an in vitro model.
OBJECTIVE
The purpose of this study was to determine whether or not the coracoacromial ligament (CAL) has a relevant effect in stabilizing the humeral head under active rotator cuff and deltoid loading compared to passive loading conditions without muscular stabilization.


METHODS
Nine human cadaver shoulders were tested in a dynamic shoulder simulator. Forces of the rotator cuff muscles and the middle deltoid muscle were applied using servohydraulic cylinders, while glenohumeral motion was imposed in closed-loop force-control by a sensor-guided robot. Translational movement was measured with the CAL intact and resected under two different testing conditions: (1) simulated physiologic muscle force loading and (2) the passive drawer test, with loads applied in anterior, anterio-inferior, and anterio-superior directions in different glenohumeral positions.


RESULTS
The resection of the CAL caused a significant increase in anterior and superior translation during translational testing and muscle force loading. However, the passive testing mode revealed differences in translation from 2.4 to 4.4 mm. The differences were quantitatively minor under muscle loading conditions, ranging from 0.5 to 1.0 mm.


CONCLUSIONS
CAL resection induces an increased glenohumeral translation under passive loading conditions without muscular stabilization, whereas the effect under rotator cuff and deltoid loading was defined to be quantitatively small.


CONCLUSIONS
A resection of the CAL should be critically discussed in shoulders with massive rotator cuff tears. In contrast, in muscularly intact shoulders, the release of the CAL evokes a light increase of translation, the clinical relevance of which is questionable.
Wellmann
Mathias
M
Department of Orthopaedic Surgery, Hannover Medical School, Hannover, Germany. mathias.wellmann@annastift.de
Petersen
Wolf
W
Zantop
Thore
T
Schanz
Steffen
S
Raschke
Michael J
MJ
Hurschler
Christof
C
D001696:Biomechanical Phenomena; D006801:Humans; D006811:Humerus / Q000502:physiology*; D008023:Ligaments, Articular / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D016059:Range of Motion, Articular; D012371:Robotics; D017006:Rotator Cuff / Q000502:physiology*; D012540:Scapula / Q000033:anatomy & histology; D012783:Shoulder Dislocation / Q000503:physiopathology / Q000601:surgery; D013710:Tendons / Q000502:physiology; D016474:Weight-Bearing