Clinical Evaluation
What is Known and What is Not Known
Acknowledgement: Portions of the 'Examination' section of this paper were taken and modified with permission from McClure P, Greenberg E, Kareha S. Evaluation and management of scapular dysfunction. Sports Med Arthrosc 2012;20:39–48.
The goal of scapular assessment is to identify abnormal scapular motion (dyskinesis), determine any relationship between altered motion and symptoms and identify the underlying causative factors of the movement dysfunction. Clinical assessment of scapular dyskinesis is inherently challenging due to the three-dimensional nature of scapular movement and soft tissue surrounding the scapula obscuring direct measurement of bony positioning. Several methods of identifying scapular dyskinesis have been described; although many of these tests have been shown to possess adequate levels of reliability, the validity of most tests remains questionable due to a lack of direct correlation with symptoms. Clinical evaluation of scapular dysfunction in patients with shoulder pain should include three basic elements: (1) visual observation to determine the presence or absence of scapular dyskinesis, (2) the effect of manual correction of the scapular dysfunction on symptoms and (3) evaluation of surrounding anatomic structures that may be responsible for the observable dyskinesis.
The Lateral Scapular Slide Test (LST) is a static measurement of the side-to-side difference of the distance from the inferior angle of the scapula to the adjacent spinous process. The validity of this test has been questioned due to the findings that both symptomatic and asymptomatic individuals will demonstrate asymmetry when measured in this manner. Additionally, it is possible to have symmetrical pathological dyskinesis so validity is questionable when comparison is made only to the contralateral side. A lack of validity was also found in a systematic review, which found that the LST was unable to differentiate between those with and without shoulder pain. The static and two-dimensional nature of this test fails to fully assess the dynamic three-dimensional motion found to occur with scapular movement. This inadequacy of measurement along with questionable validity of results requires the use of other methods of scapular assessment during clinical examination.
Visual dynamic assessment schemes of classifying the presence of scapular dyskinesis during shoulder motion have been developed in an attempt to resolve the issues with linear or static measures. These methods are considered more functional and more inclusive with the ability to judge scapular movement in three-dimensional patterns. Kibler et al were the first to describe a visually based system for rating scapular dysfunction that defined three different types of motion abnormality and one normal type. Reliability values for this system were too low to support clinical use and the test was subsequently refined in two later studies using a simplified method of classification.
The SDT is a visually based test for scapular dyskinesis that involves a patient performing weighted shoulder flexion and abduction movements while scapular motion is visually observed. This test consists of characterising scapular dyskinesis as absent or present and each side is rated separately. Dyskinesis is defined as the presence of either winging (prominence of any portion of the medial border or inferior angle away from the thorax) or dysrhythmia (premature, or excessive, or stuttering motion during elevation and lowering). Good inter-rater reliability of this test (75–82% agreement; weighted κ=0.48–0.61) was achieved after brief standardised online training http://www.arcadia.edu/academic/default.aspx?id=15080. Concurrent validity was demonstrated in a large group of overhead athletes, finding those judged as demonstrating abnormal motion using this system also demonstrated decreased scapular upward rotation, less clavicular elevation and less clavicular retraction when measured with three-dimensional motion tracking. These results support the assertion that shoulders visually judged as having dyskinesis utilising this system demonstrate distinct alterations in three-dimensional scapular motion, particularly during flexion. However, while visually observed dyskinesis resulted in altered three-dimensional motion, those with dyskinesis were no more likely to report symptoms.
Another dynamic test developed by Uhl et al used essentially the same criteria as the SDT (winging or dysrhythmia) to classify an abnormality in scapular motion into the 'yes' classification and normal movement was classified as 'no'. They studied both symptomatic patients with various soft tissue pathologies as well as an asymptomatic group. The 'yes/no' test was found to have superior inter-rater reliability (79% agreement; κ=0.41) and demonstrated better specificity and sensitivity values when using asymmetry found with three-dimensional testing as a gold standard. An important finding in this study was a higher frequency of multiple-plane dyskinesis during shoulder flexion in patients (54%) compared with asymptomatic subjects (14%), while no differences between groups were detected during scapular plane elevation. It appears that the optimum position for evaluating scapular dyskinesis dynamically is in forward flexion. Another interesting finding was that the prevalence of overall scapular dyskinesis was essentially equal between those with and without shoulder pain, respectively, 76% and 77% in scaption and 71% and 71% in flexion.
The presence of scapular dyskinesis or abnormal scapular position is not able to diagnose the presence or absence of shoulder pain, as reported in a recent systematic review. In this systematic review, the diagnostic accuracy values indicated that some tests had moderate-to-high specificity or sensitivity, but no test provided value in shifting the pretest probability when the test was used. This is likely due in large part to the common finding of scapular dyskinesis in those with and without shoulder pain. Moreover, scapular asymmetry (side-to-side differences) is a common finding in healthy individuals, further complicating the ability to identify when scapular motion or position is abnormal. Based on evidence to date, scapular dyskinesis (dynamic) and position (static) tests are not helpful tests to completely diagnose shoulder pain. These tests should be considered as impairment assessment tools.
Since scapular dyskinesis is a common finding, a basic problem in evaluation is deciding if the presence of scapular dyskinesis is an important abnormality-perpetuating symptom. The possibility exists that alterations of scapular motion could be compensatory strategies to avoid stress on pain-sensitive tissue. Symptom alteration tests have been developed as a way to infer scapular mal-position is driving symptoms by manually correcting scapular movement during provocation testing. If altering scapular position causes an immediate decrease in symptoms, this provides direct evidence that scapular dyskinesis is a contributing factor to shoulder symptoms. The two main symptom alteration tests are the SAT test and the SRT.
The SAT involves manually assisting scapular upward rotation during shoulder elevation and determining the effect on pain. This test was later modified by Rabin incorporating scapular posterior tilting as well. A positive test is when pain with elevation is either decreased or abolished during the assisted manoeuvre. This test has demonstrated acceptable levels of reliability. It is unknown if the SAT can identify those who have scapular dyskinesis or mal-position that is perpetuating their symptoms.
The SRT involves manually positioning and stabilising the medial border of the scapula with simultaneous posterior tilting in a slightly retracted position on the thorax. This test was developed in order to help in identifying patients in whom strength loss in shoulder elevation may be due to a loss of proximal stability of the scapula or that the scapular mal-position may be promoting pain. The test is considered positive when the patient demonstrates a reduction of pain or an increase in shoulder elevation strength when the scapula is stabilised during isometric arm elevation in the scapular plane at 90°. Kibler et al studied this test in symptomatic and asymptomatic subjects and found no change in pain, and all subjects had improved strength output regardless of the symptoms. The SRT was also studied in overhead athletes, where roughly half of those with pain (46/98) during impingement testing had reduced pain and 26% had a substantial increase in isometric elevation strength. It is unclear if the SRT is helpful based on these equivocal findings, and future studies are needed to confirm if this test can identify a subset of patients with shoulder pathology that may benefit from interventions designed to improve scapular muscle function.
Examination of the surrounding tissue should be performed in order to identify those impairment factors that may be responsible for causing the altered scapular motion. Implicated as possible contributors to the development of scapular dyskinesis are the deficits in strength or motor control of scapular-stabilising muscles, postural abnormalities and impaired flexibility. A comprehensive examination of these components is necessary.
Muscle strength of key scapular stabilisers can be assessed utilising standard positions and procedures described by Kendall et al. The key muscles to test are the serratus anterior, middle trapezius and lower trapezius, as these are muscles that have been identified with key roles for scapular stabilisation and movement. An important concept in testing these muscles is that even though resistance is applied through the arm, weakness is identified by early 'breaking' of the scapula rather than the arm. In patients with rotator cuff or deltoid weakness, the arm may need to be supported and resistance applied directly to the scapula to accurately determine scapular muscle weakness.
Many authors have suggested that forward head posture and increased thoracic kyphosis may contribute to scapular protraction and lead to adaptive shortening of postural muscles or muscular strength imbalances. A protracted scapular position may be associated with a narrowed subacromial space, upright posture with increased subacromial space and a flexed thoracic spine and forward shoulder position alters scapular motion and results in diminished force output with elevation. Adaptive shortening of the pectoralis minor muscle has been identified as a contributor to abnormal scapular kinematics and implicated as a factor that may contribute to shoulder impingement syndrome. Sahrmann has described an assessment method for pectoralis minor length that involves taking a linear measurement with the patient supine from the treatment table to the posterior aspect of the acromion, with any measurement greater than 2.54 cm suggesting tightness. Although highly reliable, the validity of this method is questioned as it failed to discriminate those with shoulder pain. Another assessment method that has been described involves using a tape measure or calipre to record the linear distance between the anatomic origin and insertion of the pectoralis minor muscle. This measure was found to have satisfactory intrarater reliability (intraclass coefficient=0.82–0.87) and good concurrent validity, but practicality for routine clinical use is questionable. This linear measure requires careful palpation and must be normalised to the size of the individual, but a threshold for 'tightness' has not been established.
Posterior shoulder tightness (capsular or rotator cuff) has been associated with excessive scapular protraction and may contribute to scapular dyskinesis. Three methods of assessing posterior shoulder tightness are (1) internal rotation at 90° abduction, (2) spinal level reached with reaching behind the back and (3) horizontal adduction with the arm at 90° flexion and the scapula blocked from moving into abduction. These methods have demonstrated acceptable levels reliability for clinical use. Gerber et al showed that different parts of the posterior capsule restrict internal rotation with the arm by the side versus 90°. Therefore, authors have recommended that clinicians utilise multiple assessment methods in order to allow for a more comprehensive assessment of posterior shoulder tightness. Measurements of shoulder internal rotation are affected by humeral and glenoid version and therefore make it difficult to distinguish between soft-tissue tightness and bony alterations causing diminished internal rotation.
Future Directions
Much more data need to be assembled to make the clinical evaluation more diagnostic and more specific for treatment. While these data are being assembled, the fairly comprehensive evaluation protocol outlined should be used to create a clinical picture of the variety of alterations that can be demonstrated to be part of scapular dyskinesis. This examination should be included as a routine part of the shoulder examination.