The evaluation of the scapulothoracic joint is an integral part of both a preventive physical examination as well as during the examination of the injured overhead athlete [6
]. In the clinical setting, methods used to evaluate the scapula rely on visual observation and a keen understanding of the normal mechanics and pathomechanics of scapular motion. We used a clinical method of visual observation to evaluate uninjured professional baseball players for the presence of scapular dyskinesis using a scapular classification system recommended in the literature [6
]. The presence of subtle scapular dyskinesis identified in laboratory studies [13
] in overhead athletes coupled with the reported consequences of scapular dyskinesis on high-level overhead upper extremity function [6
] highlight the importance of early identification and recognition of scapular pathology in overhead athletes to both prevent injury and optimize performance. The overall purpose of this study was to use a clinical method of visual observation to evaluate the scapula of uninjured professional baseball players to determine the interrater reliability of visual observation and the Kibler et al. [8
] scapular classification system.
We recognized limitations to our study. First, scapular function and motion were not assessed on these players while performing their sport-specific movements such as throwing or pitching. Instead, a clinical method of scapular evaluation was used that involved elevation of the shoulder in the scapular plane using a 2-pound weight as has been advocated and studied elsewhere in the clinical and experimental literature [8
]. Second, the use of video recording and capture of the upper extremity movements rather than live evaluation may have limited the interpretation of scapular outline and full appreciation of some aspects of human scapular motion that are better captured with live observation. This method of using video recording of upper extremity movements has been used in the literature in other investigations and the quality of the video was not deemed a limitation by the examiners who were able to review and rereview each subject’s repetitions. Additionally, it was not possible to have multiple examiners at the time of data capture and the use of video did allow for unbiased private evaluation of the data by each of the examiners truly in an independent manner. Lastly, the use of healthy uninjured players may have limited the identification of more obvious forms of scapular dyskinesis typically reported and found in patients and athletes with shoulder injury [6
]. The use of uninjured players was meant to best replicate the clinical challenge of early identification of players at risk for injury before a season of sport, a frequent clinical challenge encountered by orthopaedic surgeons and sports physical therapists and athletic trainers.
Several studies have begun evaluating the effectiveness of visual observation of scapular motion. McClure et al. [12
] videotaped a sample of 142 uninjured athletes using the motions of flexion and coronal plane abduction with a 3- to 5-pound weight. Multiple raters viewed the videotape recording and rated the scapula as normal, subtle, or obvious dyskinesis. Their study produced k coefficients ranging between 0.48 and 0.61 with percentage agreement ranging between 75% and 82% between examiners (Table ). They identified satisfactory reliability using this scapular classification system in overhead athletes. Tate et al. [18
] performed an additional study to validate the scapular classification system used in the study by McClure et al. [12
] using 66 of the same 142 subjects clinically analyzed in the McClure et al. study. Using three-dimensional electromagnetic kinematic testing, Tate et al. [18
] revealed less scapular upward rotation and less clavicular elevation in subjects classified with obvious dyskinesis compared with those classified with normal scapular motion. The study by Tate et al. [18
] demonstrated the important objective relationship identified between three-dimensional electromagnetic kinematic testing and observationally based scapular evaluation in overhead athletes. Uhl et al. [19
] measured 56 subjects, 35 of which had been diagnosed with shoulder injury on clinical examination and/or imaging studies using both a “yes/no” and “four-type” (Kibler Type I, II, III, IV) classification system to document scapular dyskinesis. Two blinded examiners rated the subjects using both methods of categorization, which resulted in k coefficients of 0.40 for the yes/no method of evaluating scapular dyskinesis and 0.44 for the “four-part” method. The percent agreement for the two methods were 79% and 61% for the yes/no and four-part methods, respectively. Uhl et al. [19
] also used a three-dimensional tracking method to objectively quantify scapular motion on each subject. They compared the visual observation classifications with the objective tracking data and found each method to have sensitivity values of 74% to 78% (yes/no) and 10% to 54% (four-part), whereas specificity values ranged between 38% and 31% (yes/no) and 62% and 94% (four-part). Uhl et al. [19
] used both flexion and scapular plane elevation movements in their study. Interestingly, they reported more multiple plane scapular movement asymmetries in the symptomatic population (54%) in flexion compared with asymptomatic (14%) subjects. The flexion movement pattern identified abnormal scapular movement in both symptomatic and asymptomatic populations. Our study only used the scapular plane elevation position. Differences between the Uhl et al. [19
] study and our present research include analysis of “live” versus videotaped evaluation of the subjects as well as the comparison between two examiners by Uhl et al. [19
] and the use of four examiners in our present study. This might partially explain the lower k values generated in our present research using the same four-type Kibler system and dichotomous classifications.
Summary of findings for visual observation of scapular dyskinesis
Several studies have identified alterations in scapular movement in healthy uninjured overhead athletes [10
]. Myers et al. [13
] measured increased scapular upward rotation, internal rotation, and retraction in throwing athletes on their dominant throwing extremity as compared with a control group of nonthrowers. Laudner et al. [10
] tested baseball pitchers and position players and found the pitchers had less scapular upward rotation on their dominant arm at 60° and 90° of scapular plane elevation compared with position players. This decrease in upward rotation may compromise the acromiohumeral interval during overhead motion and increase injury risk in individuals in this population. Finally, Oyama et al. [15
] measured scapular posture in a population of 43 overhead athletes. They found greater scapular protraction in tennis players on the dominant shoulder than on the nondominant side. Additionally, in all the overhead athletes (baseball pitchers, volleyball players, and tennis players), the dominant scapula was more internally rotated and anteriorly tilted than the nondominant side. These studies all show alterations in dominant arm scapular motion in overhead-throwing athletes. Unilateral repetitive overhead activity coupled with extreme ROM demands throughout the upper extremity kinematic chain is believed to result in musculoskeletal adaptations that have been documented with laboratory-based research methods.
We found low reliability between experienced examiners using the Kibler scapular classification system for professional baseball pitchers and catchers without known shoulder pathology. The subtle adaptations and absence of shoulder injury may have complicated the ability of the examiners to more clearly identify the subtle scapular adaptations and dyskinesis patterns that may accompany these athletes. Further testing of both the four-part and yes/no classification on injured overhead athletes is needed to further understand the optimal method for identifying and classifying scapular pathology that is commonly associated with overuse injury in the overhead athlete. Further research is needed to best determine the humeral elevation positions and load additions and classification system to most reliably and accurately identify scapular pathology in a clinically based environment.