Biomedical Engineering Reference
In-Depth Information
1.4
Problem
Despite advances in diagnostic and treatment interventions, shoulder injuries
continue to plague throwing athletes [
43
]. These athletes are prone to shoulder
injuries as a result of the high forces placed on the shoulder during the throwing
motion. Overhead athletes require a delicate balance between shoulder mobility and
stability in order to meet the functional demands of their respective sport. Altered
mobility patterns, concerning rotational movement, as mentioned before, have been
consistently reported in the dominant shoulder of throwers such as elite baseball
pitchers [
21
], volleyball players [
44
] or handball players [
45
].
Commonly, clinical ROM testing includes the measurement of maximal external
and internal rotation using a goniometric approach, i.e., placing patient in a supine
or a sitting position, with the arm abducted to 90
ı
and totally supported by the table.
In this position, the examiner passively rotates the arm until the extreme position
of internal or external rotation (end-range). In a sited position the examiner has to
stabilize the inferior angle of the scapula, having the patient hold his/her elbow at
a side while rotating the forearm around the long axis of the humerus [
46
,
47
].
On both procedures the examiner passively sets the arm according to the capsular
end-feel [
28
,
48
,
49
], or by scapular liftoff [
47
]orevenbypain[
46
]. On the other
hand, the goniometric protocol imposes that the scapular motion must be limited
by a posterior force applied by the examiner on the coracoids process and clavicle,
restricting arm motion to the glenohumeral joint.
From a biomechanical perspective the goniometric protocol has three key limita-
tions: (1) the end-range is determined by clinical end-feel, as opposed to an objective
assessment of torque; (2) goniometers were designed to assess glenohumeral
motion, but they are really measuring both glenohumeral and scapulothoracic
motion and scapula can have a significant effect on both goniometric and vertebral
level measurements. Isolating glenohumeral motion typically requires a fixation
technique to prevent unwanted scapular motion, but this approach is difficult to
perform and may induce unwanted artifact into the measurement. Third, the effect
of the plane of motion has not been well documented [
26
].
1.5
Purpose of the Study
The main purpose of the study was to clarify the scapular contribution to the
amplitude of shoulder external rotation on thrower athletes. The assessment of
internal and external rotation ROM is a standard part of a shoulder clinical
examination. However, the contribution of shoulder girdle in the rotational motion
pattern often is frequently not considered by clinicians. Additionally, the study looks
to quantify the effects of the end-range determination and the speed of motion on
the external rotation ROM. To date, no studies have specifically investigated how
humeral rotational pattern is affected by active or passive end-range determination
in overhead throwing athletes.
