Waters Peter M, Monica James T, Earp Brandon E, Zurakowski David, Bae Donald S
Department of Orthopaedic Surgery, Children's Hospital Boston, Harvard Medical School, Hunnewell 2, 300 Longwood Avenue, Boston, MA 02115, USA.
J Bone Joint Surg Am. 2009 Oct;91(10):2367-75. doi: 10.2106/JBJS.H.00417.
Muscle imbalance about the shoulder in children with persistent brachial plexus birth palsy is thought to contribute to glenohumeral joint deformity. We quantified cross-sectional areas of the internal and external rotator muscles in the shoulder by magnetic resonance imaging in patients with chronic brachial plexopathy and the correlation between these muscle cross-sectional area ratios and glenohumeral deformity. The purposes of this investigation were to evaluate differences in the ratios between affected and unaffected shoulders in the same individual and to assess whether an increased internal to external rotator muscle cross-sectional area correlated with greater glenohumeral deformity.
This cohort study consisted of magnetic resonance imaging of seventy-four patients with chronic neuropathic changes about the shoulder from brachial plexus birth palsy. There were at least nine patients with scans available for each of the five classified subtypes of glenohumeral deformity: type I (fifteen patients), type II (seventeen), type III (seventeen), type IV (sixteen), and type V (nine). Cross-sectional areas of the pectoralis major, teres minor-infraspinatus (external rotators), and subscapularis muscles were measured. The supraspinatus muscle cross-sectional area could not be reliably measured. The ratio of subscapularis to external rotators, the ratio of pectoralis major to external rotators, and the compound ratio of subscapularis and pectoralis major to external rotators were compared with the severity of the glenohumeral deformity. Passive range of motion, Mallet and Toronto clinical scores, and Narakas type were also compared with the severity of the glenohumeral deformity and the muscle cross-sectional area measurements.
Muscle cross-sectional area ratios were significantly correlated with glenohumeral deformity type. The mean ratio of pectoralis major to external rotators for affected shoulders over all deformity types compared with that for unaffected shoulders was significantly increased by 30% (p < 0.001); the mean ratio for subscapularis and pectoralis major to external rotators, by 19% (p = 0.015), and the mean ratio for subscapularis to external rotators, by 10% (p = 0.008). There was a significant increase in the ratio of pectoralis major to external rotators in affected shoulders within each type of deformity. Analysis of variance indicated higher ratios of pectoralis major to external rotator muscle cross-sectional areas in more severe deformity types (p < 0.001). There were significant differences in external rotation measurements with the shoulder at 90 degrees of abduction only among glenohumeral deformity types I, II, and III (p < 0.05).
The degree of muscle imbalance between internal and external rotators about the shoulder is measurable by magnetic resonance imaging in children with persistent brachial plexopathy, and the imbalance correlates with the degree of glenohumeral deformity. Our results may provide useful information to guide the timing and the choice of operative intervention in these children.
持续性臂丛神经产瘫患儿肩部肌肉失衡被认为会导致盂肱关节畸形。我们通过磁共振成像对慢性臂丛神经病变患者肩部内、外旋肌的横截面积进行了量化，并分析了这些肌肉横截面积比值与盂肱关节畸形之间的相关性。本研究的目的是评估同一个体患侧与健侧肩部比值的差异，并评估内旋肌与外旋肌横截面积增加是否与更严重的盂肱关节畸形相关。
本队列研究纳入了74例因臂丛神经产瘫导致肩部慢性神经病变的患者的磁共振成像资料。盂肱关节畸形的五种分类亚型中，每种至少有9例患者有扫描资料：I型（15例）、II型（17例）、III型（17例）、IV型（16例）和V型（9例）。测量了胸大肌、小圆肌-冈下肌（外旋肌）和肩胛下肌的横截面积。冈上肌的横截面积无法可靠测量。比较了肩胛下肌与外旋肌的比值、胸大肌与外旋肌的比值以及肩胛下肌和胸大肌与外旋肌的复合比值与盂肱关节畸形的严重程度。还比较了被动活动范围、马利特和多伦多临床评分以及纳拉卡斯分型与盂肱关节畸形严重程度和肌肉横截面积测量值之间的关系。
肌肉横截面积比值与盂肱关节畸形类型显著相关。所有畸形类型患侧肩部胸大肌与外旋肌的平均比值与健侧相比显著增加了30%（p < 0.001）；肩胛下肌和胸大肌与外旋肌的平均比值增加了19%（p = 0.015），肩胛下肌与外旋肌的平均比值增加了10%（p = 0.008）。每种畸形类型中患侧肩部胸大肌与外旋肌的比值均显著增加。方差分析表明，在更严重的畸形类型中，胸大肌与外旋肌横截面积的比值更高（p < 0.001）。仅在盂肱关节畸形I型、II型和III型中，外展90度时肩部外旋测量值存在显著差异（p < 0.05）。
持续性臂丛神经病变患儿肩部内、外旋肌之间的肌肉失衡程度可通过磁共振成像测量，且这种失衡与盂肱关节畸形程度相关。我们的结果可能为指导这些患儿手术干预的时机和选择提供有用信息。
