Background 

Strength testing of shoulder rotation is commonly used in clinical examinations of the shoulder. People prone to shoulder injury, such as overhead athletes and manual trade workers, place their shoulders under tremendous amounts of stress when the cervical spine is in nonneutral positions. If these nonneutral cervical spine positions result in decreased shoulder strength, it may help explain the etiology of the high prevalence of shoulder injuries in these populations. Given standard clinical strength assessments are performed with a neutral cervical spine, an investigation into the effects of cervical spine rotation is warranted.

Questions/purposes 

We sought to compare isokinetic shoulder rotation strength while in a neutral position with rotated cervical spine positions, specifically (1) with the cervical spine rotated contralaterally with the shoulder elevated in the frontal plane and (2) with the cervical spine rotated ipsilaterally and the shoulder elevated in the scapular plane.

Methods 

A convenience sample of 52 individuals (height 170 ± 10 cm; weight 73 ± 18 kg, age 21 ± 2 years; 18 males, 34 females), without shoulder or cervical spine pathology participated in this study. Participants were screened for eligibility via questionnaire. Concentric shoulder internal and external rotation torque was measured through a 90° arc on an isokinetic dynamometer with the shoulder elevated 90° in the frontal plane, and again 45° anterior to the frontal plane (scapular plane). Two repetitions were performed in a single testing session with the participant’s cervical spine in neutral in both planes, maximally rotated contralaterally in the frontal plane, and maximally rotated ipsilaterally with the shoulder in the scapular plane; the second repetition was used for analysis. The testing order was randomized. Data were imported into a platform for statistical parametric mapping analysis (a technique that allows data from the entire arc of motion to be compared with data from another arc to identify differences in the wave form) to compare strength between positions throughout 90° arc of motion.

Results 

Rotating the cervical spine contralaterally with the shoulder in the frontal plane resulted in a decrease in external (2.24 Nm or 12% average difference; p < 0.001) and internal (2.22 Nm or a 6% average difference; p = 0.02) rotation strength with the forearm within 15° and 20° of the vertical position. Rotating the cervical spine ipsilaterally with the shoulder in the scapular plane resulted in a decrease in external rotation strength (1.27 Nm or a 6% average difference; p < 0.001) throughout nearly all the motion, with peaks approximately 20° and 60° from the horizontal position, and internal rotation strength (1.78 Nm or 5% average difference; p < 0.001) the last 60° towards the horizontal position.

Conclusion 

Patient populations who require strenuous use of their shoulders in altered cervical spine positions may be at increased risk for injury from decreased shoulder rotator strength.

Clinical Relevance 

Clinicians should assess shoulder strength in the position the patient requires to use their shoulder because cervical spine position may cause weakness that would be missed in standard testing positions.

中文翻译：

---

颈椎位置改变会导致肩部旋转强度下降

背景 

肩关节旋转力量测试是肩关节临床检查中常用的方法。肩部容易受伤的人，例如过头运动员和体力工人，当颈椎处于非中立位置时，他们的肩膀会承受巨大的压力。如果这些非中立的颈椎位置导致肩部力量下降，则可能有助于解释这些人群中肩部损伤高发的病因。鉴于标准临床强度评估是在颈椎中立的情况下进行的，因此有必要对颈椎旋转的影响进行研究。

问题/目的 

我们试图比较处于中立位置和旋转颈椎位置时的等速肩部旋转强度，特别是（1）颈椎向对侧旋转，肩部在额状面上抬高；（2）颈椎向同侧旋转，肩部抬高肩胛平面升高。

方法 

52 名无肩部或颈椎病理的个体（身高 170 ± 10 厘米；体重 73 ± 18 公斤，年龄 21 ± 2 岁；18 名男性，34 名女性）组成的方便样本参与了这项研究。通过问卷调查参与者的资格。同心肩部内旋和外旋扭矩是通过等速测功机上的 90° 弧测量的，肩部在额状面中抬高 90°，并再次在额状面（肩胛面）前面 45°。在一次测试中进行两次重复，参与者的颈椎在两个平面中均处于中立位置，在额状平面中最大程度地向对侧旋转，并在肩胛平面中最大程度地向同侧旋转肩部；第二次重复用于分析。测试顺序是随机的。将数据导入统计参数映射分析平台（一种允许将整个运动弧的数据与另一个弧的数据进行比较以识别波形差异的技术），以比较整个 90° 运动弧中位置之间的强度。

结果 

在额状面中与肩部对侧旋转颈椎会导致外部（2.24 Nm 或 12% 平均差异；p < 0.001）和内部（2.22 Nm 或 6% 平均差异；p = 0.02）旋转强度下降前臂与垂直位置的夹角在 15° 和 20° 之间。在肩胛平面内与肩部同侧旋转颈椎会导致几乎所有运动中的外旋强度下降（1.27 Nm 或 6% 平均差异；p < 0.001），峰值与肩胛骨平面成约 20° 和 60°。水平位置，以及最后 60° 朝向水平位置的内旋强度（1.78 Nm 或 5% 平均差异；p < 0.001）。

结论 

需要在改变颈椎位置时用力使用肩膀的患者群体可能因肩旋转肌力下降而面临更大的受伤风险。

临床相关性 

临床医生应在患者需要使用肩膀的位置评估肩部力量，因为颈椎位置可能会导致标准测试位置中遗漏的无力。