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ISSN : 1225-8962(Print)
ISSN : 2287-982X(Online)
Physical Therapy Korea Vol.24 No.2 pp.48-57
DOI : https://doi.org/10.12674/ptk.2017.24.2.048

Relationships Between Rounded Shoulder Posture and Biceps Brachii Muscle Length, Elbow Joint Angle, Pectoralis Muscle Length, Humeral Head Anterior Translation, and Glenohumeral Range of Motion

Sil-ah Choi1 , Heon-seock Cynn1,2 , Ji-hyun Lee1 , Da-eun Kim1 , A-reum Shin1
1Applied Kinesiology and Ergonomic Technology Laboratory, Dept. of Physical Therapy, The Graduate School, Yonsei University
2Dept. of Physical Therapy, College of Health Science, Yonsei University
Corresponding author: Heon-seock Cynn cynn@yonsei.ac.kr
April 5, 2017 April 5, 2017 May 10, 2017

Abstract

Background:

Rounded shoulder posture (RSP), a postural abnormality, might cause shoulder pain and pathologic conditions. Although most previous research has investigated RSP focusing on the proximal structures of the shoulder, such as the scapula and pectoralis muscles, the relationship between RSP and anterior distal structures of the upper extremity, such as the biceps brachii muscle and elbow joint, is not clearly understood.

Objects:

This study aimed to investigate the correlations between RSP and the biceps brachii length, elbow joint angle (EJA), pectoralis minor length, general pectoralis major length, humeral head anterior translation (HHAT), glenohumeral internal rotation (IR), external rotation (ER), and horizontal adduction (HAD).

Methods:

Twelve subjects with RSP (6 male, 6 female) were recruited. All subjects fulfilled the RSP criteria indicated by a distance ≥2.5 cm from the posterior aspect of the acromion to the table in the supine position. The examiner measured each of the following parameters twice: RSP, biceps brachii length, EJA, pectoralis minor length, pectoralis major length, HHAT, glenohumeral IR, ER, and HAD. Pearson’s correlation coefficient(r) was used to assess the correlation between RSP and all the variables.

Results:

There was a significant moderate positive correlation between RSP and biceps brachii length (r=.55, p=.032), moderate negative correlation between RSP and pectoralis minor length (r=-.62, p=.015), and moderate positive correlation between RSP and HHAT (r=.53, p=.038).

Conclusion:

The biceps brachii length, pectoralis minor length, and HHAT could be used to evaluate patients with RSP. Better understanding of the correlation between these factors and RSP could help in the development of effective methods to treat patients with this condition in clinical management.


초록


    Introduction

    Rounded shoulder posture (RSP) is a specific postural abnormality that might cause shoulder pain and pathologic conditions such as subacromial impingement syndrome, adhesive capsulitis, and rotator cuff disease (Lewis et al, 2005; Ludewig and cook, 2000; Michener et al, 2005). In RSP cases, excessive humeral head anterior translation (HHAT) relative to the line of gravity of the body with glenohumeral internal rotation (IR) is common when the scapula is abducted and tilted anteriorly (Massimini et al, 2012; Myers et al, 2006). Also, the elbow is excessively flexed, and the forearm is pronated and placed anterior to the hips, although the ideal alignment of the elbow is slight flexion, which indicates that the proximal and distal humerus is placed almost in the same vertical line, and the forearm is in neutral rotation so that the thumb is oriented anteriorly and the palm of the hand is oriented towards the body (Page et al, 2009; Sahrmann, 2002).

    Most previous research has investigated RSP focusing on the proximal structures of the shoulder girdle, such as the scapular or humeral head position, glenohumeral range of motion (ROM), and pectoralis muscle length. To correct RSP, pectoralis muscle stretching or manual release (Borstad and Ludewig, 2006; Wong et al, 2010) and scapular repositioning or stabilization exercises such as exercises with a scapular brace, scapular posterior tilt exercise, and wall push-up plus are frequently used by physical therapists (Cole et al, 2013; Lee et al, 2015). However, the relationship between RSP and anterior distal structures of the upper extremity, such as the biceps brachii muscle length and elbow joint angle (EJA), is not clearly understood. The biceps brachii muscle and elbow joint could be important components to consider when dealing with shoulder problems.

    The biceps brachii muscle affects the glenohumeral joint function because of the two different attachments of the biceps brachii: the long and short heads. The long head of the biceps (LHB) is attached from the supraglenoid tubercle of the scapula and passes through the bicipital groove, and the short head of the biceps (SHB) is attached from the coracoid process of the scapula (Buck et al, 2011; Drake et al, 2009; McGarry et al, 2016). Especially, the LHB has long been considered as a causative factor of anterior shoulder pain (Wilk and Hooks, 2016). Inflammation of the LHB diagnosed as biceps tendonitis has been associated with rotator cuff lesions and subacromial impingement syndrome (Chen et al, 2005; Gill et al, 2007; Habermeyer et al, 2004). Also, subcoracoid impingement syndrome related with the common origin of the coracoid process (the SHB and coracobrachialis) is characterized by anterior shoulder pain, cervical myofascial pain syndrome, and radiating pain to the upper arm and forearm (Karim et al, 2005; Paulson et al, 2001).

    The myofascial pain syndrome may occur when the shoulder pain or injury originating from muscle imbalance, malalignment, or abnormal posture changes the shoulder mechanics (Karim et al, 2005; Simon et al, 1999). Simon et al. (1999) reported that in patients with trigger points in the pectoralis minor, biceps brachii, or coracobrachialis muscles, pain can radiate from the anterior shoulder region and suprascapular region to the arm. Clinically, upper extremity pain or symptoms from sustained and repeated postural compensation patterns, such as forward neck posture, RSP, or excessive kyphosis would be observed along with the myofascial meridian, for example, biceps tendinopathy, elbow epicondylitis, or carpal tunnel syndrome (Myers, 2009; Sahrmann, 2002). In this way, myofascial referral pain and the myofascial meridian may explain why the contributing factors to shoulder or scapular issues would involve not only the pectoralis major and minor but also the biceps brachii and elbow joint.

    Therefore, the purpose of this study was to investigate the correlations between RSP and the biceps brachii length, EJA, pectoralis minor length, general pectoralis major length, humeral head anterior translation (HHAT), glenohumeral internal rotation (IR), external rotation (ER), and horizontal adduction (HAD). It was hypothesized that there would be a moderate to strong correlation between RSP and the biceps brachii muscle length, EJA, pectoralis minor muscle length, pectoralis major muscle length, HHAT, glenohumeral IR, ER, and HAD.

    Methods

    Subjects

    A power analysis was performed with G*power software ver. 3.1.2 (Franz Faul, University of Kiel, Kiel, Germany) using the results of a pilot study involving 5 subjects. The sample size calculation was carried out with a power of .80, alpha level of .05, and effect size of .96. This provided a necessary sample size of 4 subjects for this study. Twelve subjects with RSP (6 male, 6 female) were recruited from a university population (age=21.7±1.7 years; height=167.3±8.6 cm; weight=59.7±11.5 kg; and body mass index=21.1±2.3 kg/m2). All subjects fulfilled the specific RSP criteria in the preferred arm when eating and writing (Yoshizaki et al, 2009). RSP was indicated by a distance ≥2.5 cm from the posterior aspect of the acromion to the table in the supine position (Sahrmann, 2002). Subjects were excluded if they had a history of surgery or existing pathologies of the shoulder and elbow, dysfunction that substantially limited shoulder and elbow motion, current complaint of numbness or tingling in the upper extremity limiting their activities, and any congenital postural abnormalities (Cole et al, 2013; Lee et al, 2015).

    Prior to collecting data, the examiner informed the subjects of the study procedures and each subject completed an informed consent form. The study protocol was approved by the Yonsei University Wonju Institutional Review Boar (approval number: 1041849- 201704-BM-034-01).

    Procedures

    The examiner measured each of the following twice: RSP, biceps brachii length, EJA, pectoralis minor length, general pectoralis major length, HHAT, glenohumeral IR, ER, and HAD. The mean value from the two measurements was used for analyzing data.

    1.Biceps brachii muscle length

    The subject was positioned in the supine position, with the shoulder at the edge of a table with the elbow extended and forearm pronated. After instructing subjects on the motion desired, the examiner hyperextended the shoulder completely through the available ROM while maintaining the elbow in full extension (Reese and Bandy, 2010). This passive movement allows an estimate of the available ROM. In this position, the digital inclinometer (GemRed DBB, Gain Express Holdings, Ltd., Hong Kong, China) was placed on the humerus aligned with the lateral aspect of the acromion process and lateral epicondyle of the humerus (Figure 1.).

    2.Elbow joint angle

    To achieve a natural resting posture, subjects were instructed to march in place 5 times, moving both the upper and lower extremities. Next, subjects stood in a relaxed position looking straight ahead with their feet shoulder width apart. Three reflective markers were placed over the acromion, humerus lateral epicondyle, and middle point of the radial styloid process and the ulnar head. The EJA was measured as the angle between the line connecting the acromion and the humerus lateral epicondyle and the line connecting humerus lateral epicondyle and the middle point of the radial styloid process and the ulnar head. With Image J software (National Institutes of Health, Bethesda, MD, USA), the EJA was calculated automatically (Figure 2.).

    3.Pectoralis minor muscle length

    The subjects stood up straight with the forearm in neutral position and hand in resting position. To measure the muscle length of the pectoralis minor, the examiner marked the origin and insertion of the pectoralis minor on the skin (the medio-inferior aspect of the coracoid process and just lateral to the sternocostal junction of the inferior aspect of the fourth rib). The examiner measured the distance between the two bony landmarks with a digital caliper (Borstad and Ludewig, 2005).

    4.General pectoralis major muscle length

    The subject was placed in the supine position, with the hands clasped together behind the head. The examiner ensured that the subject maintained the hands clasped and did not flex the cervical spine any more than necessary to place the clasped hands behind the head. The subject relaxed the shoulder muscles, allowing the elbows to move toward the support surface; the lumbar spine was to remain flat against the support surface. Using a digital caliper, the examiner measured the distance between the olecranon process of the humerus and the support surface (Reese and Bandy, 2010)

    5.Humeral head anterior translation

    HHAT was measured with the subject lying in a relaxed position on a table, with both arms placed beside the trunk in the neutral position. The examiner then calculated the difference between the distance from the table and the anterior peak of the humeral head, and the distance from the table and the acromion (Gong et al. 2013).

    6.The range of glenohumeral internal rotation and glenohumeral external rotation

    The subject was positioned in the supine position with the shoulder abducted 90° and the elbow flexed 90° to ensure a neutral horizontal position. The humerus was passively rotated internally and externally with the examiner stabilizing the scapula with his other hand (Lunden et al, 2010). In this position, the digital inclinometer was placed on the dorsal surface of the forearm aligned with the long axis of the ulna for reference. A second examiner measured the angle between the forearm and a plane perpendicular to the table.

    7.The range of glenohumeral horizontal adduction

    The examiner stood beside the table and positioned the test shoulder with the elbow in 90° flexion and the shoulder abducted 90°. The examiner stabilized the lateral border of the scapula by providing a dorsally directed force to control scapular protraction, rotation, and abduction. The examiner held the forearm, and then moved the humerus into horizontal adduction passively until the limit of movement (Moore et al, 2011). An examiner recorded the ROM for horizontal adduction using a digital inclinometer aligned with the ventral midline of the humerus.

    Statistical Analysis

    The Kolmogorov-Smirnov Z-test was used to assess normal data distribution. Pearson’s correlation coefficient (r) was used to assess the correlation between RSP and the biceps brachii length, EJA, pectoralis minor length, general pectoralis major length, humeral head anterior translation (HHAT), glenohumeral internal rotation (IR), external rotation (ER), and horizontal adduction (HAD). As suggested by Portney and Watkins (2008), correlation coefficient values under .25, between .25 and .5, between .5 and .75, and above .75 indicated little or no relationship, fair relationship, moderate to good relationship, and good to excellent relationship, respectively. The level of significance was set at .05. All statistical analyses were performed using SPSS Statistics ver. 21.0 (SPSS, Inc., Chicago, IL, USA).

    Results

    All variables had a normal distribution. The measured values of RSP, biceps brachii length, EJA, pectoralis minor length, pectoralis major length, HHAT, glenohumeral IR, ER, and HAD are presented in Table 1. There was a significant moderate positive correlation between RSP and biceps brachii length (r=.55, p=.032), moderate negative correlation between RSP and pectoralis minor length (r=-.62, p=.015), and moderate positive correlation between RSP and HHAT (r=.53, p=.038) (Table 2).

    Discussion

    To our knowledge, this study is the first to analyze the correlation between RSP and not only proximal structures of the shoulder girdle such as the humeral head position, the glenohumeral ROM, and pectoralis major, and minor muscles length, but also distal structures of the upper extremity such as the biceps brachii muscle length and EJA. The results partially supported the research hypothesis.

    This study found a significant moderate positive correlation between RSP and biceps brachii muscle length. RSP is related to the dominant or tight pectoralis major muscle, which pulls the humeral head anteriorly (Konrad et al, 2006; Page et al, 2009; Labriola et al, 2005), i.e., the glenohumeral position is regarded as extension. In the glenohumeral extension position, the biceps brachii muscle length increased, which supported our research. Many previous researchers found that the LHB functions as a stabilizer for the glenohumeral joint (Itoi et al, 1993; Pagnani et al, 1996; Rodosky et al, 1994). In a simulated cadaveric study, the LHP contraction prevented anterior, superior, and inferior translation of the humeral head (Pagnani et al, 1996). Especially, the LHB develops the anterior stability of the glenohumeral joint and resistance to torsional force, increasing the anterior instability when the shoulder is abducted and externally rotated (Itoi et al, 1993; Rodosky et al, 1994). Also, the scapular position was associated with the biceps function (Kibler and McMullen, 2003; Lukasiewicz et al, 1999; Solem-Bertoft et al, 1993). Kibler and McMullen (2003) reported that secondary scapular dyskinesis from the abnormal scapular position or motion could affect the biceps function because of coupled scapulohumeral movements. Therefore, the positive correlation between RSP and biceps brachii muscle length in the present study was consistent with previous studies, which supported that the proper position of the scapula is needed to improve upper extremity function.

    This study found a significant moderate negative correlation between RSP and pectoralis minor muscle length, supporting the research hypothesis. This finding is consistent with many previous studies (Burkhart et al, 2000; Escamilla et al, 2009; Hebert et al, 2002; Ludewig and Cook, 2000). Because the pectoralis minor is attached to the coracoid process, Escamilla et al (2009) indicated that scapular malalignment and dysfunction, especially scapular anterior tilting or winging, are associated with tightness of the pectoralis minor muscles. Hebert et al (2002) and Ludewig and Cook (2000) reported that increased tension of the pectoralis minor changes the subacromial space narrowly causing impingement syndrome. Accordingly, the importance of pectoralis minor stretching exercise is emphasized to correct RSP, thoracic kyphosis, or forward head posture, which are characterized by scapular malalignment (Borstad and Ludewig, 2005; Finley and Lee, 2003). A previous report by Lee et al (2015) revealed that pectoralis minor stretching helped correct RSP, decreasing by 30.72%, and restore the length of the pectoralis minor, increasing by 4.54%. These studies supported the fact that decreased flexibility or shortness of the pectoralis minor is a main factor to aggravate excessive forward scapular posture (Borstad and Ludewig, 2005).

    This study found a significant moderate positive correlation between the RSP and HHAT, supporting the research hypothesis. RSP is associated with upper crossed syndrome (USC) (Page et al, 2009). In UCS, tightness of the pectoralis major and minor on the anterior part crosses with tightness of the upper trapezius and levator scapulae on the posterior part. The dominant or tight pectoralis major muscle pulls the humeral head anteriorly because the pectoralis major is attached to the lateral lip of the intertubercular groove (anteromedial area) of the humerus, so the humeral head is displaced more anterior than the distal humerus not in the same vertical line (Konrad et al, 2006; Page et al, 2009; Labriola et al, 2005). Konrad et al (2006) and Labriola et al (2005) found that the posture with HHAT reduced the glenohumeral stability and centration on the glenoid fossa, and pain appeared in the anteriomedial shoulder during the glenohumeral motion. Similarly, Matsen et al (1991) and Bahk et al (2007) described the glenohumeral instability as a clinical sign of unwanted translation of the humeral head. Additionally, subjects with RSP or forward scapular posture frequently experience posterior shoulder muscle tightness (Laudner et al, 2006; Tyler et al, 2000), and tight posterior shoulder muscles may cause anterior and superior translation of the humeral head on the glenoid fossa (McClure et al, 2007; Tyler et al, 2000).

    Our study had anticipated originally that RSP would have significant relationship with the EJA for the following reasons. One reason is that RSP associated with the HHAT would induce the glenohumeral extension position and deliver passive tension of the long head of the biceps brachii and might cause reduction in a relaxed EJA (i.e., increased elbow flexed position) (Chleboun et al, 1997; Dartnall et al, 2008). An altered length-tension relationship disturbs maintaining optimal muscle lengths for peak force generation, increases whole-muscle passive tension, and reduces maximal force, which would cause difficulty in achieving an ideal joint angle (Newmann, 2002; Proske and Allen, 2005). Another possible explanation is the presence of the myofascial meridian around the arm line, especially the deep front arm line, including the pectoralis minor and biceps brachii. According to Myers (2009), the fascia of the pectoralis minor connects to the short head of the biceps and coracobrachialis at the coracoid process. As mentioned above, RSP was related to the pectoralis minor, and so we expected that the dominant pectoralis minor would tighten the biceps brachii and coracobrachialis, inducing excessive elbow flexion. Despite these possible reasons, our study did not confirm a significant correlation between RSP and the EJA; therefore, future study with a greater number of patients with RSP, chronic pain, or pathologic symptoms from RSP is needed clarify the relationship between RSP and the EJA.

    In this study, there was no significant correlation between RSP and the glenohumeral ROM such as IR, ER, and HAD. The reason for this unexpected result is that this study did not focus on tight or stiff posterior shoulder muscles or capsule regardless of recruiting subjects with RSP. Many previous studies reported that posterior shoulder tightness leads to approximation of the humeral head to the acromion causing shoulder impingement (Choi et al, 2012; Tyler et al, 2000; Yang et al, 2012), related to altered acromioclavicular and sternoclavicular joint motion (Wong et al, 2010), and change in glenohumeral flexion, IR, and HAD (Kibler and McMullen, 2003; Laudner et al, 2006; Tyler et al, 2000). Additionally, posterior shoulder tightness contributed 5% more to the prediction of forward scapular posture (Lee et al, 2015). Therefore, the glenohumeral ROM should be considered as a significant contributor to clinical RSP.

    This study has several limitations. First, our findings could not be generalized to the general patient population because healthy young subjects with only specific RSP criteria participated in this study. Therefore, young as well as older subjects with various clinical assessments for RSP should be investigated in future studies. Second, because this study only examined the relationship between RSP and independents variables, it could not explain the cause and effect for RSP by other independents variables. Further research about the long-term effect of therapeutic intervention or a randomized controlled trial is warranted to validate the results of our study.

    Conclusion

    This study examined the relationship between RSP and the biceps brachii length, EJA, pectoralis minor length, pectoralis major length, HHAT, glenohumeral IR, ER, and HAD. There was a significant positive correlation between RSP and biceps brachii muscle length, negative correlation between RSP and pectoralis minor muscle length, and positive correlation between RSP and HHAT. While these findings do not establish a cause and effect relationship, the results suggest that the assessment of HHAT, pectoralis minor muscle length, and especially biceps brachii muscle length should be taken into consideration when evaluating RSP. Better understanding of the correlation between these factors and RSP could help in the development of effective methods to treat patients with this condition in clinical management.

    Figure

    PTK-24-2-48_F1.gif

    Measurement of biceps brachii muscle length.

    PTK-24-2-48_F2.gif

    Measurement of elbow joint angle.

    Table

    Measurement values of all variables (N=12)

    Pearson correlation coefficients (r) between round shoulder posture and all variables (N=12)

    *p<.05.

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