Huang L.Y.1, Huang T.S.1, Du W.Y.1, Lin J.J.1,2
1National Taiwan University, School and Graduate Institute of Physical Therapy, College of Medicine, Taipei, Taiwan, 2National Taiwan University Hospital, Division of Physical Therapy, Department of Physical Medicine and Rehabilitation, Taipei, Taiwan
Background: Pectoralis minor adaptive shortening may change scapula resting position and scapular kinematics during arm elevation. Scapular dyskinesis with impingement pain and associated dysfunction may develop subsequently. Utility of pectoralis minor index (PMI) can help clinical decision making when evaluating and treating these individuals.
Purpose: The aim of this study was to evaluate the ability of PMI in distinguishing symptomatic scapular dyskinesis from healthy control.
Methods: Ninety-six participants with symptomatic scapular dyskinesis and 50 healthy control were recruited.
At the sitting neutral position with arms by side, PM length were measured as the distance between the medial-inferior angle of the coracoid process and the inferior aspect of the 4th rib, laterally to the sternocostal junction with a 200 mm digital caliper on symptomatic side in dyskinesis group and on dominant side in healthy control. PMI was defined as PM length divided by subject height and multiplied by 100. PMI between 2 groups were compared and receiver operating characteristic (ROC) curves were plotted on long (upper third) and short (lower third) PMI subjects.
Results: Compared to healthy group (9.4±0.8), there is a significantly shorter PMI in symptomatic scapula dyskinesis group (8.9±0.6, p=0.001). ROC curves showed significant discriminative power for symptomatic scapula dyskinesis (area under the curve [AUC] = 0.686, p = 0.0385 and AUC = 0.835,
p 0.0001 for short and long PMI, respectively). For short PMI, a cutoff of 8.7 was obtained, with sensitivity and specificity of 100.0% and 41.2%, respectively. For the long PMI, a cutoff of 9.8 was obtained, with sensitivity and specificity of 80.0% and 100.0%, respectively.
Conclusion(s): Subjects with symptomatic scapular dyskinesis have shorter PMI compared to healthy control. With excellent discrimination results, the cut-off values may be used to characterize symptomatic dyskinesis. PMI values less than 8.7 and more than 9.8 can be supposedly to be related to symptomatic dyskinesis and healthy shoulder, respectively.
Implications: PMI provides quantitative length measurements that can potentially help in symptomatic dyskinesis characterization and assisting the decision for treatment recommendations.
Funding acknowledgements: Ministry of Science and Technology, 101-2314-B-002-019-MY3, Taiwan
Topic: Musculoskeletal: upper limb
Ethics approval: Human Subject Research Ethics Committee, National Taiwan University Hospital
All authors, affiliations and abstracts have been published as submitted.
