INTRODUCTION:

Shoulder disorders are considered to be the most common musculoskeletal disorders. Prevalence of Shoulder pain is estimated between 16% and 26%, it is the third most common cause of musculoskeletal consultation in primary care¹. Shoulder is a complex combination of bones, joints, ligaments, muscles etc. which act to provide the range of motion of the specific joints. The glenohumeral joint is a ball and socket synovial joint with 3⁰ of freedom. The articulation is made up of the long head of humerus and small glenoid fossa. Since the glenoid fossa of scapula is the proximal segment of glenohumeral joint, any motions of scapula may affect glenohumeral joint function^2,6.Compromised shoulder movement due to pain, weakness, stiffness may cause substantial disability and can affect an individual’s daily activities like eating, personal hygiene, dressing etc.

Posture is defined as the relative arrangement of body parts³. Shoulder posture is significantly the position of the scapula on the thorax, influencing the resting position and status of muscles having attachments both to the cervical spine and the shoulder complex. The changes in the direction of muscle pull, as a result of alterations in scapular position, can affect the length tension relationship required to maintain a static stability^4. Changes in skeletal alignment may indicate muscle lengthening or shortening, strength imbalances between muscular agonists and antagonists or musculoskeletal derangements which promote these muscular changes⁵. Excessive or abnormal muscle tension, are adapted when inefficient or abnormal postures are maintained over time, can lead to musculoskeletal dysfunction causing pain or movement restriction⁶.

Shoulder pain happens when pain sensitive structures are involved in positions which overload, overstretch (or) shorten the associated muscles, tendons and ligaments. Stretching of a soft tissue causes discomfort initially, and further stretching causes pain and over stretching will cause microphysical damage which may turn out to be a vicious cycle. Shoulder pain is often linked to movement repetition, uncomfortable postures, prolonged maintenance of static postures and muscular fatigue⁷.

Shoulder pain syndromes results due to prolonged positional changes, where soft tissues on one side of the body will undergo shortening and soft tissues on other side of the body may adaptively lengthen. The common postural deviations are forward head, forward shoulder (scapular protraction) humeral internal rotation and increased thoracic kyphosis. Literature also mentions that common postural malalignment is forward head posture with rounded shoulders^5,6,8.Scapula protraction is a positional fault defined as an increased distance between the inferior angle of scapula and the spinous process of thoracic vertebrae⁹. The muscles that stabilize the scapula are levator scapulae, Rhomboids major and minor, serratus anterior and trapezius, controls scapular motion mainly through synergistic co contraction and force couples which are paired muscles that control the movement or position of a joint¹⁰. When the muscles are weak or fatigued scapula humeral rhythm is compromised and shoulder dysfunction results¹¹. The shoulder protraction may occur due to various factors like lack of shoulder flexibility, muscle imbalance, endurance and faculty posture¹².

Alterations in shoulder girdle muscle imbalance, muscle length tension relationship, ligamentous laxity, joint congruity, and gross shoulder motion can result from postural malalignment^13,14.

This study intends to identify the movement dysfunction in the shoulder having postural deviation and relationship of the dysfunction to the functional dominance of the extremity.

MATERIALS AND METHODS:

Participants:

An Observational study was conducted at Outpatient unit in physiotherapy department of Saveetha medical college and hospital. Subjects were selected based on convenient sampling technique. The study was approved by the Institutional Ethical Committee of the Saveetha Institute of Medical and Technical Sciences. A total of 60 subjects with altered posture of shoulder were evaluated based on the following inclusion criteria (1) age 18- 45 years (2.) Both males and females were included. Participants were excluded based on the following criteria. (1) Any Shoulder pathology (2) Cervical Joint Disease (3) Trauma and recent fracture in the cervical and upper limb regions (4.) Mechanical disorders of upper limb (5) Any surgeries on upper limb. The materials used were (1). Universal Goniometer (2.) Body marker

(3.) Inch tape (4.) Plumb line.

Procedure:

Sample size was determined based on prevalence rate by power analysis of 60% and 2-tailed. A total of 60 subjects were selected based on convenient sampling technique.

Shoulder posture was measured using plumb line, by placing it lateral to the ear and observing the deviation of the shoulder from the rope hanging from the block.

Sixty individuals with an altered posture on observation were enrolled for the study based on inclusion and exclusion criteria. Detailed procedure was explained to subjects verbally. A written informed consent was obtained from all the participants for authorizing their participation in the study. Subjects were assessed based on a general orthopaedic assessment and also including the outcome measures. The degree of protraction was measured and the individuals with restricted range of motion of the shoulder were identified from the subjects included in the study. The readings were documented. A comparison was done later on the values obtained and the hand dominance of the subjects was taken into consideration.

Outcome Measures

Outcome measures used to assess scapular protraction was scapular protraction formula and Range of motion (ROM) of shoulder measured using goniometer.

Scapular protraction:

Scapular protraction was measured by palpating and marking, using a pen with water- soluble ink and inch tape as in Fig. 1. The following formula was used to determine scapular protraction:

Scapular Protraction=line BAE/line AE, where line BAE = the distance from the mark on the thoracic spine corresponding to the root of the scapular spine to the tip of the acromion, and line AE = the distance from the root of the scapular spine to the tip of the acromion.

Figure 1- Scapular Protraction

Range of motion of shoulder:

An assessment sheet including information on Hand dominance and Range of Motion (ROM) of Shoulder flexion and shoulder abduction using universal goniometer. Three readings of every movement were taken and their mean was taken for statistical analysis.

Shoulder Flexion:

With the subject in standing position, as in Fig. 2, the shoulder positioned in 0 degrees of abduction, adduction and rotation. The forearm positioned in 0 degrees of supination and pronation so that the palm of the hand faces the body. (1) Centre the fulcrum of the goniometer close to the acromion process (2) Align the proximal arm with the mid-axillary line of the thorax (3) Align the distal arm with the lateral midline of the humerus, using the lateral epicondyle of the humerus for reference.

Fig. 2: Shoulder flexion

Shoulder Abduction:

With the subject in standing position as in Fig. 3, the shoulder is positioned in 0 degrees of flexion and extension and full lateral rotation so that the palm of the hand faces anteriorly. The elbow should be extended. (1) Centre the fulcrum of the goniometer close to the anterior aspect of the acromion process. (2) align the proximal arm so that it is parallel to the midline of the anterior aspect of the sternum. (3) At the end of the ROM, align the distal arm with the medial midline of the humerus.

Fig. 3 :Shoulder Abduction

Statistical Analysis

Sample size was determined based on prevalence rate by power analysis of 60% and 2 –tailed test. The effect size for the sample size calculation was obtained from the previous studies done on shoulder dysfunction. Data were analysed using SPSS for window version 24 (SPSS Inc., Chicago, IL, USA).

The collected data was tabulated and analysed using descriptive and inferential statistics. Mean and standard deviation (SD) were calculated for all parameters. Independent t-test was used to analyse significant difference between the dominant and the non-dominant shoulder.

RESULTS:

Sixty subjects were enrolled for the study using convenient sampling method. Subjects with altered shoulder postures were selected. Shoulder protraction and shoulder ROM of flexion and abduction of both upper extremities were recorded. Table 1 shows baseline characteristics on the mean age of subjects with protracted shoulder on the dominant side. Among the sixty participants, 43 were males and 17 were females. Table 2, shows a significant difference in shoulder protraction between the dominant and non- dominant shoulder (***P<0.0001). Table 3 shows significant difference in shoulder flexion between dominant and non- dominant shoulder (***P<0.0001). Table 4 shows significant difference in shoulder abduction between dominant and non-dominant shoulder (***P<0.0001).

Table I: Baseline characteristics of Dominant and Non-Dominant shoulder

Baseline characteristics	Right hand dominance (n = 60)	Left hand dominance (n =0)
Mean age (yrs)	28.35±6.29	nil
Male/Female n	43/17	nil

Data are presented as mean ±Standard deviation (SD)

n - Number of subjects

Table II: Comparison of Scapular Protraction between Dominant and Non- Dominant Shoulder

Scapular

Protraction

Value (cms)

t –Value

Significance

Dominant Hand

2.114±0.547

18.1510

P<0.0001

Non- Dominant Hand

0.698±0.255

Cms- Centimetres

Mean ± Standard Deviation (SD)

Table III: Comparison of Shoulder Flexion Range of Motion between Dominant and Non-Dominant Shoulder

Shoulder Flexion

Range of Motion

t- Value

Significance

Dominant Hand

153.17±11.18

6.2709

P<0.0001

Non- Dominant Hand

164.82±9.29

Mean ± Standard deviation (SD)

Table IV: Comparison of Shoulder Abduction Range of Motion between Dominant and Non-Dominant Shoulder

Shoulder Abduction

Range of Motion

t- Value

Significance

Dominant Hand

152.03±11.66

3.7003

P=0.0003

Non- Dominant Hand

159.41±10.76

Mean± Standard deviation (SD)

DISCUSSION:

Scapula protraction is an abnormal position which has been defined as an increased distance between the inferior angle of scapula and the spinous process of the vertebra.

The muscle that stabilize the scapula attach to the medial border of the scapula, thereby controlling its position. Hence these muscles controls scapular motion through synergistic co-contractions and force couples, which are paired to control the movement or position of a joint.

The main functions of these force couples are to obtain maximal congruency between the glenoid fossa and the humeral head, to provide dynamic glenohumeral stability, and to maintain optimal length-tension relationships.

Authors have suggested that strength imbalance of the anterior shoulder muscles can pull the shoulder forward producing a protracted posture which predisposes to sub acromial impingement due to decrease in sub acromial space.

The alteration of scapula position not only may have an effect on shoulder muscles performance but also it may predispose the protracted individuals to injuries because of weaker muscle performance and poor posture.

The difference in ROM of end range shoulder flexion and abduction between dominant and non- dominant upper extremity is may be due to frequent use of dominant limb in ADL activities.

In a study conducted by Christopher J Barnes et al in 2001, to determine the effect of age, sex and dominance on range of motion of shoulder, shoulder ROM decreased with age and there was no significant difference between dominant and non- dominant shoulder¹⁵.

In this study, protraction was found in the younger subjects were the mean age is 28 years. Incidentally, all the participants had right hand dominance and hence protraction was more profound on the right side shoulder.

This study is clinically useful to the therapist to measure protraction using clinical method. So it will be helpful to therapist, in making diagnosis and decisions regarding intervention to altered posture of shoulder.

A small sample size is a limitation of the study. Future studies can be done using a larger sample in different age groups and application of the study on subjects with overuse injuries of shoulder.

CONCLUSION:

In this study there was a significant difference in the end range shoulder flexion and abduction range of motion between dominant and non- dominant upper extremity, while measuring scapular protraction, which is clinically useful to the therapist to diagnose the altered posture of the shoulder.

CONFLICT OF INTEREST:

All authors have none to declare.

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Received on 07.10.2019 Modified on 30.11.2019

Research J. Pharm. and Tech. 2020; 13(10):4678-4682.

DOI: 10.5958/0974-360X.2020.00823.9