Determining the resting position of the glenohumeral joint in subjects who are healthy.
OBJECTIVE
The resting position is frequently used by clinicians in the examination and early treatment of patients with joint impairments. However, there is a lack of research on the kinematic characteristics of the resting position of the glenohumeral (GH) joint. The aim of this study was to define the resting position of the GH joint by quantifying the humeral head translation and axial rotational range of motion (ROM).


METHODS
The anterior and posterior translation of the humeral head and the rotational ROM of the dominant arm were assessed in the seated position at multiple abduction positions in 15 subjects who were healthy by use of an electromagnetic tracking device. A force of 80 N and a torque of 4 N.m were applied during the measurement procedures for the translation of the humeral head and the rotational ROM, respectively.


RESULTS
The mean resting position determined by rotational movement was located at 49.8 degrees of GH abduction. However, the mean resting position determined by translational movement was located at 23.7 degrees of GH abduction and was significantly lower than the resting position determined by rotational movement (t=5.45, P=.000).


CONCLUSIONS
The mean resting position for rotational movement is consistent with the already accepted range of 30 to 60 degrees for a "loosely packed" position of the GH joint. The mean resting position for translational movement appears to be lower than 30 to 60 degrees. The results of this study suggest that, at least for the GH joint, different resting positions should be assessed with different movement criteria (accessory or physiological movement).
Lin
Hui-Ting
HT
Department of Physical Therapy, I-Shou University, Kaohsiung County, Taiwan.
Hsu
Ar-Tyan
AT
Chang
Guan-Liang
GL
Chang Chien
Jia-Rea
JR
An
Kai-Nan
KN
Su
Fong Chin
FC
D000328:Adult; D000704:Analysis of Variance; D005260:Female; D006801:Humans; D006811:Humerus / Q000502:physiology*; D008297:Male; D011187:Posture / Q000502:physiology*; D016059:Range of Motion, Articular / Q000502:physiology*; D012146:Rest / Q000502:physiology*; D012399:Rotation; D012785:Shoulder Joint / Q000502:physiology*