Influence of Pectoralis Minor Muscle and Upper Trapez Muscle Tightness in Scapular Dyskinesis

OBJECTIVES: Alterations in scapular kinematics were found in individuals with shoulder problems compared with healthy individuals. These alterations in scapular kinematics such as changes in the normal position or any abnormal motion of the scapula during active motions are defined as “’Scapular Dyskinesis (SD)”. Relationship between tight muscles and scapular kinematics has been investigated. Pectoralis Minor Muscle Tightness (PMMT) effects scapular motion and make changes in scapular kinematics. Although there are some studies indicating a possible relationship between PMM or Upper Trapezius Muscle Tightness (UTMT) and SD, this relationship hasn’t been investigated yet. The aim of this study was to evaluate the influence of PMMT and UTMT on SD in an asymptomatic population. METHODS: One-hundred-eleven participants (mean age: 22.73±3.45 years old, 222 arms, 42 Female-69 Male) were recruited. Subjects were eligible if they were ≥18 years of age, having active full shoulder motion and who has no health problem to hinder them from participate. Individuals with symptoms produced by cervical spine motion, impingement syndrome, frozen shoulder, shoulder instability and a history of shoulder fracture/surgery were excluded. Scapular Dyskinesis Test (SDT) was used to identify SD. PMMT was determined by Pectoralis Minor Index (PMI), UTMT by UTMT Test. Logistic regression analysis performed to ascertain the effects of PMMT and UTMT on the likelihood that participants have SD. RESULTS: SD was identified in 62 arms (27.9%), PMMT in 32 arms (14.4%), and UTMT in 75 arms (33.8%) in total number of participants. PMMT was determined in 23 arms (37.1%) and UTMT in 39 arms (62.9%) in participants with SD. The logistic regression model was statistically significant, X(2)=65.472, p<.000, df= 2. The model explained 36.8% (Nagelkerke R2) of the variance in SD and correctly classified 78.4% of cases. The Wald criterion demonstrated that both PMMT and UTMT made a significant contribution to prediction (p<0.000 for PMMT, p<0.000 for PMMT). People who have PMMT were 13.76 times more likely to exhibit SD than people who haven’t. People who have UTMT were 7.59 times more likely to exhibit SD than people who haven’t. CONCLUSION: It was determined that people with PMMT and UTMT are more likely to exhibit SD than people who have normal muscle length in this asymptomatic population. Assessment of PMMT and UTMT could be included as a routine part of the scapula and scapular dyskinesia examination. This investigation should be repeated in symptomatic population who has shoulder problems. The effects of various interventions for lengthening these muscles in scapular dyskinesia, needs further research.