Differences in 3-dimensional shoulder kinematics between persons with multidirectional instability and asymptomatic controls.
BACKGROUND
Evidence that persons with multidirectional instability (MDI) of the shoulder have abnormal shoulder kinematics is limited. A kinematic description of scapulothoracic and glenohumeral motion can assist both conservative and surgical rehabilitative programs.


OBJECTIVE
Persons with MDI of the shoulder demonstrate increased anterior and inferior glenohumeral translation and decreased scapular upward rotation and increased scapular internal rotation compared with age-matched and gender-matched asymptomatic controls.


METHODS
Controlled laboratory study.


METHODS
Sixty-two subjects were recruited from an outpatient orthopaedic clinic. Subjects with MDI were matched according to age, gender, and hand dominance to asymptomatic controls. An electromagnetic motion capture system evaluated the 3-dimensional position of the trunk, scapula, and humerus during frontal and scapular plane elevation. A repeated measures analysis of variance evaluated joint positions and glenohumeral translations during 4 phases of elevation (0 degrees-30 degrees, 31 degrees-60 degrees, 61 degrees-90 degrees, and 91 degrees-120 degrees).


RESULTS
When averaged across the 4 phases of elevation, persons with MDI demonstrated a significant decrease in scapular upward rotation in scapular plane abduction (8 degrees, P = .006) and abduction (5.8 degrees, P = .016) and increased internal rotation during scapular plane abduction (12.2 degrees, P = .03). Alterations in glenohumeral translations in the MDI group did not reach statistical significance (P = .54-.71).


CONCLUSIONS
Abnormal scapular kinematics are seen in the MDI shoulder, highlighting the importance of incorporating scapular positioning and stability exercises during rehabilitation. Additional study is warranted concerning the efficacy of various rehabilitation programs, and also both surgical and nonsurgical interventions in this population.
Ogston
Jena B
JB
College of St. Scholastica, 1200 Kenwood Ave., Duluth, MN 55811, USA. jogston@css.edu
Ludewig
Paula M
PM
D000293:Adolescent; D000328:Adult; D001696:Biomechanical Phenomena; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D016059:Range of Motion, Articular / Q000502:physiology*; D012785:Shoulder Joint / Q000503:physiopathology*