Glenohumeral Joint Kinematics following Clavicular Fracture and Repairs

Abstract

BackgroundThe purpose of this biomechanical study was to determine the effect of shortened clavicle malunion on the center of rotation of the glenohumeral (GH) joint, and the capacity of repair to restore baseline kinematics.MethodsSix shoulders underwent automated abduction (ABD) and abbreviated throwing motion (ATM) using a 7-DoF automated upper extremity testing system in combination with an infrared motion capture system to measure the center of rotation of the GH joint. ATM was defined as pure lateral abduction and late cocking phase to the end of acceleration. Torsos with intact clavicle underwent testing to establish baseline kinematics. Then, the clavicles were subjected to midshaft fracture followed by kinematics testing. The fractured clavicles underwent repairs first by clavicle length restoration with plate fixation, and then by wiring of fragments with a 2-cm overlap to simulate shortened malunion. Kinematic testing was conducted after each repair technique. Center of rotation of the GH joint was plotted across all axes to outline 3D motion trajectory and area under the curve.ResultsThroughout ABD, malunion resulted in increased posterior and superior translation compared to baseline. Plate fixation restored posterior and superior translations at lower abduction angles but resulted in excess anterior and inferior translation at overhead angles. Throughout ATM, all conditions were significantly anterior and superior to baseline. Translation with malunion was situated anterior to the fractured and ORIF conditions at lower angles of external rotation. Plate fixation did not restore baseline anteroposterior or superoinferior translation at any angle measured.ConclusionsThis study illustrates the complex interplay of the clavicle and the GH joint. While abnormal clavicle alignment alters shoulder motion, restoration of clavicle length does not necessarily restore GH kinematics to baseline. Rehabilitation of the injured shoulder must address the osseous injury and the dynamic forces of the shoulder girdle.

The development and evaluation of an in-vitro shoulder simulator with active muscle simulation

“…baseball pitch). While there have been some efforts in this regard by other groups, it was not a goal of our current study 11,38 A last limitation is the relatively simple representation of muscle. The classical methodology to represent muscles by single line of action was retained in this study may not suffice to mimic the moments produced by muscles with large attachment sites e.g.…”

“…In vitro cadaver models offer the advantage www.nature.com/scientificreports/ of applying invasive tracking and measurement methods and of alteration and manipulation of the joint with the advantage retaining much of the native anatomy. Thus several passive and active shoulder simulators have been built in the recent decades with the goal of simulating physiologic and pathologic kinematics and identifying the significant contributors [8][9][10][11][12] The use of the passive shoulder simulators without active muscle simulation is largely limited to research questions associated with the stabilizing soft tissues of the joint. Nonetheless, previous studies have illustrated the importance of the musculature in creating and maintaining glenohumeral stability during active joint motion.…”

Effect of intraarticular pressure on glenohumeral kinematics during a simulated abduction motion: a cadaveric study

“…With the feedback of the anatomical coordinate systems and the programmable humeral actuator, [ 37 – 39 ] the humerus was passively raised in the scapular plane from 60 to 90˚ of GH joint abduction, which represents approximately 90 to 120 humerothoracic abduction, for five repetitions after a single preconditioning trial. The humerus was fixed so the medial and lateral condyles aligned vertically at 90˚ humerothoracic abduction, and the system did not allow for external rotation of the humerus.…”