Dynamic in vivo glenohumeral kinematics during scapular plane abduction in healthy shoulders.
METHODS
Controlled laboratory study.


OBJECTIVE
To measure superior/inferior translation and external rotation of the humerus relative to the scapula during scapular plane abduction using 3-D/2-D model image registration techniques.


BACKGROUND
Kinematic changes in the glenohumeral joint, including excessive superior translation of the humeral head and inadequate external rotation of the humerus, are believed to be a possible cause of shoulder impingement. Although many researchers have analyzed glenohumeral kinematics with various methods, few articles have assessed dynamic in vivo glenohumeral motion.


METHODS
Twelve healthy males with a mean age of 32 years (range, 27-36 years) were enrolled in this study. Fluoroscopic images of the dominant shoulder during scapular plane elevation were taken, and computed tomography-derived 3-D bone models were matched with the silhouette of the bones in the fluoroscopic images using 3-D/2-D model image registration techniques. The kinematics of the humerus relative to the scapula were determined using Euler angles.


RESULTS
On average, there was 2.1 mm of initial humeral translation in the superior direction from the starting position to 105° of humeral elevation. Subsequently, an average of 0.9 mm of translation in the inferior direction occurred between 105° and maximum arm elevation. The average amount of external rotation of the humerus was 14° from the starting position to 60° of humeral elevation. The humerus then rotated internally an average 9° by the time the shoulder reached maximum elevation. These changes in superior/inferior translation and external/internal rotation were statistically significant (P<.001 and P = .001, respectively), based on 1-way repeated-measures analysis of variance.


CONCLUSIONS
The observed glenohumeral translations and rotations characterize healthy shoulder function and serve as a preliminary foundation for quantifying pathomechanics in the presence of glenohumeral joint disorders.
Teikyo University Chiba Medical Center, Department of Orthopaedic Surgery, Ichihara, Chiba, Japan. kmatsuki@med.teikyo-u.ac.jp
Keisuke
K
Matsuki
Kei O
KO
Matsuki
Satoshi
S
Yamaguchi
Nobuyasu
N
Ochiai
Takahisa
T
Sasho
Hiroyuki
H
Sugaya
Tomoaki
T
Toyone
Yuichi
Y
Wada
Kazuhisa
K
Takahashi
Scott A
SA
Banks
D000328:Adult; D001696:Biomechanical Phenomena; D006801:Humans; D021621:Imaging, Three-Dimensional; D007564:Japan; D008297:Male; D008953:Models, Anatomic; D016059:Range of Motion, Articular / Q000502:physiology*; D012540:Scapula / Q000502:physiology*; D012785:Shoulder Joint / Q000502:physiology*