Meister Keith, Day Timothy, Horodyski MaryBeth, Kaminski Thomas W, Wasik Michael P, Tillman Susan
TMI Sports Medicine and Orthopedics, Arlington, TX 76014, USA.
Am J Sports Med. 2005 May;33(5):693-8. doi: 10.1177/0363546504269936. Epub 2005 Feb 16.
Differences in range of motion and rotational motion between the dominant and nondominant shoulders in throwing athletes are well documented, although the age at which these changes begin to occur is not known.
Changes in glenohumeral rotational motion in the shoulder of the Little League/adolescent baseball player occur during the most formative years of physical development.
Cross-sectional study.
Elevation, internal rotation at 90 degrees of abduction, and external rotation at 90 degrees of abduction were measured in the dominant and nondominant shoulders of 294 baseball players, aged 8 to 16 years.
Analysis of variance revealed 2-way interactions between arm dominance by age for elevation (P = .005) and internal rotation (P = .001). Significant differences were noted between dominant and nondominant arms for internal rotation at 90 degrees (P = .001) and external rotation at 90 degrees (P = .001). Elevation, internal rotation at 90 degrees , external rotation at 90 degrees , and total range of motion varied significantly (P = .001) among age groups. Elevation in the dominant arms of 16-year-olds was on average 5.3 degrees less than in 8-year-olds (179.6 degrees vs 174.3 degrees ). In the nondominant arms, mean elevation for 16-year-olds was 5.6 degrees less than in 8-year-olds (179.7 degrees vs 174.1 degrees ). Internal rotation at 90 degrees for the dominant arms averaged 39.0 degrees at age 8 and only 21.3 degrees at age 16. In the non-dominant arms, internal rotation for 8-year-olds averaged 42.2 degrees and only 33.1 degrees for 16-year-olds.
Elevation and total range of motion decreased as age increased. These changes may be consequences of both bone and soft tissue adaptation. The most dramatic decline in total range of motion was seen between the 13-year-olds and 14-year-olds, in the year before peak incidence of Little Leaguer's shoulder. This decrease in rotational motion may cause increased stress at the physis during throwing.
投掷运动员优势肩和非优势肩在活动范围和旋转运动方面的差异已有充分记录，尽管这些变化开始出现的年龄尚不清楚。
青少年棒球运动员肩部盂肱关节旋转运动的变化发生在身体发育的最关键时期。
横断面研究。
对294名年龄在8至16岁的棒球运动员的优势肩和非优势肩进行了外展90度时的内旋、外展90度时的外旋以及抬高测量。
方差分析显示，年龄与手臂优势在抬高（P = 0.005）和内旋（P = 0.001）方面存在双向交互作用。90度时优势臂和非优势臂在内旋（P = 0.001）和外旋（P = 0.001）方面存在显著差异。各年龄组在抬高、90度时内旋、90度时外旋以及总活动范围方面存在显著差异（P = 0.001）。16岁优势臂的抬高平均比8岁时少5.3度（179.6度对174.3度）。在非优势臂中，16岁的平均抬高比八岁时少5.6度（179.7度对174.1度）。8岁时优势臂90度内旋平均为39.0度，16岁时仅为21.3度。在非优势臂中，8岁儿童的内旋平均为42.2度，16岁时仅为33.1度。
随着年龄增长，抬高和总活动范围减小。这些变化可能是骨骼和软组织适应的结果。在青少年棒球肩发病率高峰前一年，即13岁至14岁之间，总活动范围下降最为显著。这种旋转运动的减少可能会在投掷过程中导致骨骺处应力增加。
