Reliability and validity of active and passive pectoralis minor muscle length measures

Bilateral Comparison of Anterior Shoulder Position in Elite Tennis Players

Background

In elite tennis players, musculoskeletal adaptations in the dominant upper extremity have been reported for range of motion, strength, and scapular biomechanics. In addition to scapular dysfunction, tightness and inflexibility of the pectoral musculature have been identified as risk factors for the development of overuse shoulder injury in overhead athletes.

Hypothesis

Differences in anterior shoulder position will be identified between the dominant and non-dominant extremity in elite tennis players. The purpose of this study was to examine bilateral differences in anterior shoulder posture measured using a double square in elite tennis players without shoulder injury.

Study Design

Descriptive Laboratory Study.

Methods

Three hundred and six uninjured elite tennis players were measured in the supine position using a double square method to measure anterior shoulder position. The distance from the surface of the table to the anterior most position of the shoulder (in millimeters) was measured bilaterally and compared. A dependent t-test was used to test for significant differences in anterior shoulder position between the dominant and non-dominant extremity.

Results

One hundred thirty-three males and 173 females were included in this study with a mean age of 16.58 years. The mean difference between extremities indicates increased anterior shoulder positioning on the dominant shoulder of 7.65 mm in females, and 8.72 in males. Significantly greater (p<.001) anterior shoulder position measures were documented on the dominant shoulder as compared to the non-dominant shoulder.

Conclusions

The results of this study showed significantly (p<.001) greater anterior shoulder position on the dominant extremity of elite male and female tennis players. The differences of 7-8mm between extremities has clinical application for interpreting anterior shoulder position test results in this population.

Level of Evidence

3.

Pectoralis minor length measurements in three different scapula positions

Background

The pectoralis minor (PM) muscle is commonly regarded as a contributor to abnormal scapula positioning. Subsequently, the muscle length of the scapular stabilising muscles may be affected, as these muscles assume a lengthened position, which over time causes weakness. There are inconsistencies regarding PM muscle length values because of the different techniques and positions used when the length of the PM muscle is measured.

Objective

To determine the PM muscle length in participants aged 18−24 using a Vernier^® caliper and expressed as pectoralis minor index (PMI), with the scapula in three different positions.

Method

The PM muscle length of 144 participants was measured with a Vernier^® caliper (intraclass correlation coefficient 0.83−0.87). Measurements were made with the scapula in the resting position, in an active and a passive posterior tilt position.

Results

Significant differences were observed in PMI between the resting scapula position – 10.04 (confidence interval, CI 9.93–10.14) and active posterior tilt – 10.19 (CI 10.09–10.30) (p < 0.001); the resting position – 10.04 (CI 9.93–10.14) and passive posterior tilt – 10.77 (10.66–10.87) (p < 0.001) and active – 10.19 (CI 10.09–10.30) and passive posterior tilt 10.77 (10.66–10.87) (p < 0.001). The dominant side had lower PMI values than the non-dominant side.

Conclusion

The significant differences between the active and posterior tilt positions suggested that optimal muscle length of PM was affected by the inner range strength of the lower fibres of Trapezius.

Clinical implications

It is important that in clinical practice not only the length of PM in scapular misalignment but also the strength of the antagonistic muscles is considered.

Shoulder impairment and pain of individuals with newly acquired spinal cord injury compared to uninjured peers

STUDY DESIGN

Cohort study.

OBJECTIVES

Shoulder pain prevalence is high in those with spinal cord injury (SCI) and is associated with decreased function, participation restrictions and decreased quality of life. Limited evidence exists regarding physical impairments of newly acquired SCI. The current study compared musculoskeletal factors at rehabilitation initiation in individuals with newly acquired SCI to uninjured individuals. We hypothesized no impairment differences of shoulder pain, strength, mobility, muscle extensibility, or rotator cuff integrity would exist between groups.

SETTING

Multi-site laboratory setting.

METHODS

Thirty-five individuals with newly acquired SCI and age and gender-matched controls without SCI (n = 34) participated. Musculoskeletal Pain Survey, shoulder range of motion (ROM), strength, pectoralis minor muscle extensibility (PM) and tissue integrity [Ultrasound Pathology Rating Scale (USPRS)] were obtained.

RESULTS

Higher pain was reported by individuals experiencing new SCI along with lower strength across all bilateral measures, reduced elevation, external rotation, and horizontal adduction ROM, with large effect sizes. PM bilateral extensibility was reduced compared to controls, with moderate between group effect size; however, no USPRS score difference existed.

CONCLUSIONS

This study provided the first comprehensive clinical description for individuals with newly acquired SCI. In comparison to matched uninjured controls, participants with new SCI reported greater shoulder pain with impairments in mobility, strength, and extensibility. The identified early clinical impairments aligned with progressive impairment including further pain development and persistence. Awareness and modification of these early clinical impairments may lead to improved long-term outcomes, improving the overall health and well-being of individuals with newly acquired SCI.

SPONSORSHIP

Spinal Cord Injury Research Program Investigator-Initiated Research Award under Award No. W81XWH-17-1-0476.

Clinical Measures Related to Forward Shoulder Posture: A Reliability and Correlational Study

OBJECTIVES

The purpose of this study was to examine the reliability of clinical measures related to forward shoulder posture (pectoralis minor index [PMI], scapular index [SI], abduction index [AI], acromion to the wall index [AWI] acromion to the treatment table index [ATI], and thoracic curvature [TC]), and to investigate the association (redundancy) among these measures.

METHODS

Twenty-one asymptomatic participants participated in this study. Two physiotherapists were trained to perform the clinical measurements. Intraclass correlation coefficients (ICC_2,k) were calculated to assess intra- and interrater reliabilities. Pearson product moment correlation was used to investigate the existence of possible redundancy between the measures that showed high intra- and interrater reliabilities.

RESULTS

The measures showed ICCs between 0.30 and 0.97. Five measures, PMI, SI, AWI, ATI, and TC, showed appropriate values for intrarater reliability (ICCs 0.77-0.94), and 3 measures, AWI, ATI, and TC, for interrater reliability (ICCs 0.82-0.85). Among measures that showed acceptable intra- and interrater reliability values, 2 measures were redundant, showing high association (AWI vs ATI) (r = 0.80, P < .001).

CONCLUSION

For PMI, SI, AWI, ATI, and TC measures, adequate values of intrarater reliability were observed. For AWI, ATI, and TC, adequate values of interrater reliability were found. Two pairs of measures were highly associated (PMI with SI; AWI with ATI), which indicates redundancy among them. Our results suggest that, when the same examiner performs the assessment, the combined use of the PMI, AWI, and TC measures allows a quick but comprehensive evaluation of the presence of forward shoulder posture.

Pectoralis minor muscle elongation and scapulothoracic motion do not differ in individuals with short versus typical resting pectoralis minor muscle length: a cross-sectional study

BACKGROUND

Individuals with short resting pectoralis minor muscle length have been shown to have aberrant scapulothoracic motion when compared to individuals with long resting pectoralis minor muscle length. However, the degree to which the pectoralis minor muscle can be lengthened and whether or not scapulothoracic motion differs between individuals with short and typical resting pectoralis minor muscle length is unknown.

OBJECTIVES

To determine if: (1) pectoralis minor muscle elongation (percent pectoralis minor muscle can be actively and passively lengthened beyond resting length), (2) pectoralis minor muscle percent length change during overhead reaching, and (3) scapulothoracic motion during overhead reaching differ between individuals with short and typical resting pectoralis minor muscle length.

DESIGN

Two group comparison.

METHODS

Thirty healthy individuals were placed into a short or typical resting pectoralis minor muscle length group. A caliper was used to measure resting pectoralis minor muscle length and pectoralis minor muscle length during active and passive muscle lengthening. An electromagnetic tracking system was used to measure pectoralis minor muscle length change as well as scapular, humeral, and trunk motion during several arm elevation tasks. Pectoralis minor muscle elongation and length change during arm elevation tasks were compared between groups using independent t-tests. Two-factor mixed-model analyses of variance were used to compare scapulothoracic motion at arm elevation angles of 30°, 60°, 90°, and 120°.

RESULTS

Pectoralis minor muscle elongation and pectoralis minor muscle length change during arm elevation did not differ between groups. Scapulothoracic motion did not differ between groups across arm elevation tasks.

CONCLUSIONS

Although resting pectoralis minor muscle length differed between groups, pectoralis minor muscle lengthening and scapulothoracic motion were similar between participants with short and typical resting pectoralis minor muscle length. Additional studies are needed to better understand the role of pectoralis minor muscle elongation on scapulothoracic motion.

Effect of flexibility deficit on scapular asymmetry in individuals with and without shoulder pain

BACKGROUND

Many studies have investigated the relationship between soft tissue tightness and shoulder kinematics. However, there is a lack of information on the dynamic properties responsible for side-to-side differences such as scapular asymmetry.

OBJECTIVE

To determine the relationship between a deficit in soft tissue flexibility and scapular asymmetry.

METHODS

A total of 58 individuals (29 patients with shoulder pain and 29 asymptomatic participants) were enrolled. Bilateral shortening of the pectoralis minor muscle and posterior shoulder tightness were assessed. Additionally, side-to-side flexibility deficit was calculated. Scapular kinematics were measured with an electromagnetic tracking device while individuals were standing in a resting position and during arm elevation. The symmetry angle was calculated to quantify scapular asymmetry.

RESULTS

The pectoralis minor and the posterior capsule flexibility deficit showed a significant positive relationship with the symmetry angle in the resting position separately for both asymptomatic (r=0.47, r=0.37 relatively) and symptomatic groups (r=0.58, r=0.38 relatively), indicating that the increased deficit in the pectoralis minor and posterior capsule flexibility were associated with increased scapular asymmetry. However, no significant relationship was found between flexibility deficit and scapular asymmetry during arm elevation and lowering for both asymptomatic and symptomatic groups.

CONCLUSION

The findings of the study provided information on the relationship of a flexibility deficit on the scapular position and orientation in asymptomatic and symptomatic populations.

Association of Pectoralis Minor Muscle Extensibility, Shoulder Mobility, and Duration of Manual Wheelchair Use

OBJECTIVE

To assess the relation of pectoralis minor muscle (PMm) length and extensibility to shoulder pain, shoulder girdle motion, and duration of manual wheelchair (MWC) use, and to compare differences in muscle length, muscle extensibility, peak humeral elevation, and pain among groups based on duration of wheelchair use.

DESIGN

Cross-sectional cohort study.

SETTING

Laboratory setting.

PARTICIPANTS

Individuals with spinal cord injury (SCI) who used an MWC for daily community and home mobility (N=22; 18 men; mean age, 41.7y; duration wheelchair use, 14.6y). Participants were stratified into groups based on duration of wheelchair use: <5 years (n=6), 5 to 15 years (n=8), and >15 years (n=8).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Clinical measures of PMm length and extensibility, shoulder girdle motion, and shoulder pain (Wheelchair User's Shoulder Pain Index).

RESULTS

Significant high correlations were found among duration of wheelchair use, passive PMm length, passive PMm extensibility, and peak humerothoracic elevation. Moderate correlation of peak humerothoracic elevation to pain was found. Individuals with >15 years wheelchair use had reduced PMm extensibility and reduced peak humerothoracic elevation than those with <5 years duration of use.

CONCLUSIONS

To our knowledge, this is the first investigation to identify the association of reduced PMm extensibility with reduced shoulder girdle mobility, pain, and duration of wheelchair use in individuals with SCI.