Observational Scapular Dyskinesis: Known-Groups Validity in Patients With and Without Shoulder Pain
STUDY DESIGN: Cross-sectional.
BACKGROUND: The scapular dyskinesis test (SDT) has demonstrated reliability and validity, but its utility for clinical decision making is unclear.
OBJECTIVES: To characterize the prevalence of scapular dyskinesis in participants with and without shoulder pain, and to determine the influence of blinding to the presence of shoulder pain on prevalence of scapular dyskinesis.
METHODS: Participants (n = 135), 67 with shoulder pain and 68 healthy controls, were included in this study. The SDT was performed by 2 examiners, from a total of 21 physical therapists. The second examiner was blinded to the participant's presence of shoulder pain. The SDT involved participants performing 5 repetitions of shoulder flexion and abduction, while the clinician observed for scapular dyskinesis, as characterized by scapular winging or dysrhythmia. Dyskinesis was rated as normal, subtle, or obvious. Ratings were collapsed into 2 groups, dyskinesis (subtle and obvious) and no dyskinesis (normal), as recommended by expert consensus.
RESULTS: There were no significant differences for scapular dyskinesis prevalence between the shoulder pain group and control group during the SDT in abduction (shoulder pain, 67.2%; 95% confidence interval [CI]: 0.55, 0.77 and control group, 52.9%; 95% CI: 0.41, 0.64; P = .09) or flexion (shoulder pain, 67.2%; 95% CI: 0.55, 0.77 and control group, 61.8%; 95% CI: 0.50, 0.72; P = .51). There were significant differences (P≤.001) between the examiners' SDT ratings in the shoulder pain group. The unblinded examiner reported a higher prevalence when testing the involved shoulder for dyskinesis in flexion (blinded, 67.7%; 95% CI: 0.56, 0.78 and unblinded, 80%; 95% CI: 0.69, 0.88) and during abduction (blinded, 66.2%; 95% CI: 0.54, 0.76 and unblinded, 78.5%; 95% CI: 0.67, 0.87).
CONCLUSION: Scapular dyskinesis as assessed with the SDT is not more prevalent in those with shoulder pain. Rating was influenced by an examiner's knowledge of shoulder pain presence. Scapular dyskinesis may represent normal movement variability.
LEVEL OF EVIDENCE: Diagnosis, level 4.
KEY WORDS:evaluation, screening, shoulder pain