A clinical method for identifying scapular dyskinesis, part 2: validity

Abstract

Context: Although clinical methods for detecting scapular dyskinesis have been described, evidence supporting the validity of these methods is lacking.

Objective: To determine the validity of the scapular dyskinesis test, a visually based method of identifying abnormal scapular motion. A secondary purpose was to explore the relationship between scapular dyskinesis and shoulder symptoms.

Design: Validation study comparing 3-dimensional measures of scapular motion among participants clinically judged as having either normal motion or scapular dyskinesis.

Setting: University athletic training facilities.

Patients or other participants: A sample of 142 collegiate athletes (National Collegiate Athletic Association Division I and Division III) participating in sports requiring overhead use of the arm was rated, and 66 of these underwent 3-dimensional testing.

Intervention(s): Volunteers were viewed by 2 raters while performing weighted shoulder flexion and abduction. The right and left sides were rated independently as normal, subtle dyskinesis, or obvious dyskinesis using the scapular dyskinesis test. Symptoms were assessed using the Penn Shoulder Score.

Main outcome measure(s): Athletes judged as having either normal motion or obvious dyskinesis underwent 3-dimensional electromagnetic kinematic testing while performing the same movements. The kinematic data from both groups were compared via multifactor analysis of variance with post hoc testing using the least significant difference procedure. The relationship between symptoms and scapular dyskinesis was evaluated by odds ratios.

Results: Differences were found between the normal and obvious dyskinesis groups. Participants with obvious dyskinesis showed less scapular upward rotation (P < .001), less clavicular elevation (P < .001), and greater clavicular protraction (P = .044). The presence of shoulder symptoms was not different between the normal and obvious dyskinesis volunteers (odds ratio = 0.79, 95% confidence interval = 0.33, 1.89).

Conclusions: Shoulders visually judged as having dyskinesis showed distinct alterations in 3-dimensional scapular motion. However, the presence of scapular dyskinesis was not related to shoulder symptoms in athletes engaged in overhead sports.

Keywords: assessment; kinematics; shoulder; upper extremity.

Figure 1. Individual axes and rotations used to describe scapular orientation and position. A, Scapular posterior tilting. Negative or decreasing values represent anterior tilting. B, Scapular upward rotation. Negative or decreasing values represent downward rotation. C, Scapular external rotation. Decreasing values represent scapular internal rotation. Because the scapula remains internally rotated relative to the frontal plane of the thorax, these values remain negative. D, Clavicular elevation. Negative or decreasing values represent clavicular depression. E, Clavicular protraction. Decreasing values represent retraction. Because the clavicle tends to remain retracted relative to the frontal plane of the thorax, these values typically remain negative. Reprinted with permission of the American Physical Therapy Association. This material is copyrighted, and any further reproduction or distribution is prohibited.

Figure 2. Mean scapular rotations during humerothoracic flexion during arm elevation (minimum [min] to maximum [max]) and lowering (max to min). The solid line represents the mean values of the participants with normal motion; the dashed line represents the mean values of the participants with obvious dyskinesis during weighted test movements. The minimum values for humerothoracic flexion for the normal and abnormal groups were 9.8 and 8.2, respectively; the maximal values were 149.6 and 150.0, respectively. A, Scapular posterior tilting, with negative or decreasing values representing anterior tilting. B, Scapular upward rotation, with decreasing values representing scapular downward rotation. C, Scapular external rotation, with decreasing values representing scapular internal rotation. D, Clavicular elevation, with decreasing values representing clavicular depression. E, Clavicular protraction, with decreasing values representing retraction. The clavicle remains retracted with respect to the coronal plane of the thorax and, therefore, exhibits negative values. Error bars indicate standard error. ^a Indicates P < .05.

Figure 3. Mean scapular and clavicular rotations during humerothoracic coronal-plane abduction during arm elevation (minimum [min] to maximum [max]) and lowering (max to min). The solid line represents the mean values of the participants judged to have normal motion; the dashed line represents the mean values of the participants judged to have obvious dyskinesis during weighted test movements. The minimum values for humerothoracic abduction for the normal and abnormal groups were 6.2 and 3.7, respectively; the maximum values were 149.2 and 149.3, respectively. A, Scapular posterior tilting, with negative or decreasing values representing anterior tilting. B, Scapular upward rotation, with decreasing values representing downward rotation. C, Scapular external rotation, with decreasing values representing scapular internal rotation. D, Clavicular elevation, with decreasing values representing clavicular depression. E, Clavicular protraction, with decreasing values representing retraction. The clavicle remains retracted with respect to the coronal plane of the thorax and, therefore, exhibits negative values. Error bars indicate standard error. ^a Indicates P < .05.