盂肱關節內轉缺失的棒球選手：投球生物力學、肌肉骨骼特質、本體感覺及運動表現

Abstract

盂肱關節內轉缺失（GIRD）被視為過肩運動員上肢傷害的重要危險因子。由於投球動作具有單側、強力且重複性的特性，常導致慣用側肩關節出現特定的適應性變化，尤其在棒球選手中更為常見。GIRD 指的是慣用側肩關節內轉活動度相較於非慣用側的減少。研究者推測，肩關節生物力學與投擲動作的改變可能增加受傷風險。先前研究已觀察到 GIRD 棒球選手在盂肱關節投球動作及在單純肩內外轉時肩胛骨運動的差異。 在第二章第一個研究中，我們深入探討了 GIRD 棒球選手在快速球投擲時的肩胛骨運動學與肌肉活化，發現其後傾與上轉角度減少，且肌肉徵招模式與有症狀的 GIRD 投手不同。這些結果提醒臨床人員與運動醫學專家應密切關注出現 GIRD 現象的投手，並透過肩胛穩定與活動度訓練來改善代償性肌肉徵招與肩胛骨運動學。 儘管 GIRD 被廣泛認為會影響功能表現，但實證證據仍有限。Kerlan–Jobe Orthopedic Clinic（KJOC）問卷是目前評估過肩運動員功能表現的主要工具，能敏感偵測上肢功能的微小變化。由於 GIRD 具有適應性，不同競技層級的棒球選手可能展現出不同特徵。第二章第二個研究中，我們探討了不同層級選手的肌肉骨骼特徵與 KJOC 分數的關聯，發現各層級選手的 GIRD 表現與肌肉骨骼特徵不同，並與功能表現相關。特別是後肩緊繃、肱骨後旋與棒球經驗等因素可作為低功能表現的指標，並應依競技層級進行針對性介入。 第二章第三個研究進一步探討了軟組織型 GIRD（ST-GIRD），提供對潛在肌肉骨骼變化更細緻的理解。與傳統僅測量關節角度的 GIRD 不同，ST-GIRD 納入軟組織變化，能更全面反映傷害機轉。我們發現 ST-GIRD 與功能、自覺表現、肩胛排列、肩峰肱骨距離與後關節囊厚度等因素有更強的關聯，支持內轉受限與後關節囊增厚、肩峰肱骨距離減少有關。這些結果為教練與醫療人員提供更精準的監測與介入依據。 根據第二章第三個研究的特徵，我們在第四個研究導入機器學習技術，建立個人化的傷害風險評估與預測工具。研究追蹤 98 位棒球選手一個球季，其中 28 位發生傷害。透過肩峰肱骨距離、棘上肌肌腱厚度、佔位比與後關節囊厚度四項特徵，我們顯著提升了預測準確性，為棒球選手量身打造傷害預防策略。 在 GIRD 適應過程中，肩關節周圍的機械感受器可能受損，導致部分去導入與本體感覺缺損。儘管已有研究探討棒球選手的本體感覺，但 GIRD 對此的影響仍不明確。本體感覺涉及多系統神經回饋，理解其來源相當複雜。雖然已有研究探討肩關節的關節位置感，但中樞神經系統皮質活動在本體感覺中的角色仍待釐清。了解 GIRD 導致的本體感覺缺損來源，有助於臨床治療規劃。此外，GIRD 的適應可能影響投球表現，導致周邊與中樞層級的本體感覺缺損。 在本次的研究中，我們探討了皮質活動、本體感覺敏銳度與功能表現三者在 GIRD 發展中的關聯，並分析 ST-GIRD 與這些參數的關係。86 位高中棒球選手接受評估，使用 3D 電磁動作分析與腦波儀記錄主動關節再定位任務中的肩關節本體感覺與皮質活動，並以手機與雷達儀器記錄投球表現。主要指標包括肩胛胸關節與盂肱關節的關節位置感、F3/4 與 P3/4 電極的 β 與 α 波皮質活動，以及肌力、投球速度與準確性等功能表現。結果顯示，越高的內轉缺失數值與下斜方肌、前鋸肌與旋轉肌群肌力下降呈中度負相關，並與投球誤差增加與球出手時額葉皮質活動下降有關。高內轉缺失組的投球誤差與皮質活動顯著劣於低內轉缺失組。ST-GIRD 與肩胛本體感覺上升、球速減慢與中下斜方肌肌力下降有關，且頂葉皮質活動亦顯著下降。這些結果顯示 GIRD 與 ST-GIRD 不僅是肌肉骨骼問題，更涉及神經肌肉與感覺運動控制的改變，強調應針對軟組織活動度、肩胛控制與感覺運動訓練進行介入，以維持表現並預防傷害，臨床人員也應隨時監控ST-GIRD，並在介入時適度控制ST-GIRD在0至5度範圍內，避免影響本體感覺回饋輸入。

Glenohumeral Internal Rotation Deficit (GIRD) is considered a significant risk factor for upper extremity injuries among overhead athletes. The unique nature of overhead pitching, characterized by unilateral, forceful, and repetitive movements, often leads to specific adaptations in the dominant shoulder complex, particularly prevalent in baseball players. GIRD refers to a reduction in internal rotation range in the dominant shoulder compared to the non-dominant shoulder. Researchers speculate that altered shoulder biomechanics and throwing motions may contribute to injury risk. Previous studies have observed differences in pitching biomechanics in the glenohumeral joint among baseball players with GIRD. Additionally, changes in scapular movement have been noted during simple internal and external shoulder rotation in baseball players with GIRD. In the first study (Chapter II), we investigated scapular kinematics and associated muscle activation during fastball pitching motion in baseball players with GIRD. Our findings revealed reduced posterior tilt and upward rotation in pitchers with GIRD, along with distinctive patterns of muscle recruitment compared to symptomatic GIRD pitchers. Based on our findings, it's crucial for clinicians and sports medicine practitioners to pay close attention to pitchers exhibiting signs of GIRD. Additionally, targeted interventions focusing on scapular strengthening and mobility exercises may help address compensatory muscle recruitment patterns and restore optimal scapular biomechanics in pitchers with GIRD. Although the relationship between GIRD and impaired functional performance is widely believed, empirical evidence supporting this connection remains scarce. The Kerlan–Jobe Orthopedic Clinic self-report questionnaire (KJOC) stands as the primary tool for assessing functional performance in overhead athletes, offering sensitivity to detect even subtle changes in upper extremity-related function specific to sports. Given the adaptive nature of GIRD, baseball players across different competitive levels may exhibit distinct characteristics. Moreover, GIRD arises from a combination of changes in musculoskeletal characteristics, likely influenced to some extent by the player's competitive level. In the second study, we investigated the musculoskeletal characteristics across players at varying levels of competition and their correlations with the KJOC score. Our findings revealed unique GIRD patterns and associated musculoskeletal characteristics among players at different competitive levels, with implications for functional performance. Specifically, we identified criteria indicative of low functional performance related to posterior shoulder tightness, humeral retroversion, and baseball experience, which were tailored to baseball players at each competitive level. Our findings suggest that targeted interventions addressing specific musculoskeletal characteristics associated with GIRD, such as posterior shoulder tightness and humeral retroversion, should be implemented across all levels of baseball players. In addition to exploring the traditional range of GIRD, our research in the third study explores deeper into the concept of Soft Tissue GIRD (ST-GIRD), which provides a more detailed understanding of the underlying musculoskeletal changes. Unlike traditional GIRD measurements, which focus solely on joint angles, ST-GIRD considers soft tissue alterations, offering a more comprehensive view of potential injury mechanisms. Our study investigates the correlation between GIRD and ST-GIRD with self-perceived function and performance, as well as their relationship with various musculoskeletal factors associated with injury. We found that ST-GIRD provides more detailed insights than GIRD alone, showing stronger correlations with function and performance, scapular alignment, acromiohumeral distance, and posterior capsule thickness. These findings support the hypothesis that internal rotation deficiency is linked to increased posterior capsule thickness and decreased acromiohumeral distance. By shedding light on the role of soft tissue changes in GIRD, our research offers coaches and healthcare practitioners a more refined approach to monitoring the function and performance of baseball players. Understanding these distinctions can inform targeted interventions aimed at preventing injuries and optimizing performance. According to the features identified in the third study, we integrated artificial intelligence through machine learning techniques in the fourth study to develop precise and individualized injury risk assessment and prediction tools for baseball players. Our study tracked 98 baseball players over a season, with 28 players experiencing injuries during this period. By incorporating four distinct clinical features—acromiohumeral distance, supraspinatus tendon thickness, occupation ratio, and posterior capsule thickness—we advanced the prediction of upper extremity injuries in baseball players. Our machine learning analysis unveiled the potential of these features to significantly improve predictive accuracy, paving the way for personalized injury prevention strategies tailored specifically for baseball athletes. In the process of adapting to GIRD, the mechanoreceptors in the capsular and soft tissue structures surrounding the shoulder joint may be impacted, leading to partial deafferentation and proprioceptive deficits. Despite existing research on proprioception in baseball players, there is limited evidence on how GIRD affects this aspect. Furthermore, proprioception involves neurological feedback from various systems, making it complex to understand fully. While previous studies have explored the joint position sense of baseball players' shoulders, the role of cortical activity in the central nervous system for proprioception remains unclear. Understanding the potential sources of proprioceptive deficits related to GIRD could aid clinicians in planning treatment strategies for affected baseball players. Additionally, pitching performance may be influenced by GIRD adaptations, resulting in proprioceptive deficits at the peripheral and/or cortical levels. In the last study, we investigated the relationships among cortical activity, active joint position sense acuity, and performance in baseball players to understand their roles in the development of GIRD. We also examined the ST-GIRD in relation to these parameters. Eighty-six high school baseball players were assessed. A 3-dimensional kinematics data by Polhemus 3Space FASTRAK electromagnetic-based motion analysis system, and electroencephalography by NeXus-10 hardware with BioTrace + software were employed during an active joint repositioning task to capture shoulder active joint position sense and cortical activity, while pitching performance was recorded using a smartphone and radar device. Key outcome measures included joint position sense at the scapulothoracic and glenohumeral joints, cortical activity at F3/4 and P3/4 (in both beta and alpha frequencies), and functional performance indicators such as muscle strength, pitching velocity, and accuracy. Results revealed that a greater internal rotation deficit value was moderately associated with reduced strength in the lower trapezius, serratus anterior, and internal/external rotators, and was linked to increased constant pitching error and lower frontal cortical activity during ball release. The higher deficit cases demonstrated significantly greater pitching inaccuracy and lower cortical activation compared to players with lower deficits. ST deficit values were associated with enhanced scapular active joint position sense, reduced ball velocity, and decreased strength in the middle and lower trapezius, with notable reductions in parietal cortical activity. These findings suggest that GIRD and ST-GIRD are not solely musculoskeletal in nature but involve neuromuscular deficits and sensorimotor alterations, underscoring the importance of interventions targeting tissue mobility, scapular control, and sensorimotor retraining to preserve performance and prevent injury in overhead athletes.