Value of shoulder US compared to MRI in infants with obstetric brachial plexus paralysis

PURPOSEChildren with brachial plexus birth injury (BPBI) may eventually develop glenohumeral instability due to development of unbalanced muscular strength. Our major goal in this study is to compare the accuracy of physical examination and ultrasonography (US) in determination of glenohumeral instability in infants with BPBI compared with magnetic resonance imaging (MRI) as a gold standard, and to investigate the role and value of US as a screening modality for assessing glenohumeral instability.METHODSForty-two consecutive patients (mean age, 2.3±0.8 months) with BPBI were enrolled into this prospective study. Patients were followed up with physical examination and US with dynamic evaluation in 4–6 weeks intervals. Patients who developed glenohumeral instability based on physical examination and/or US (n=21) underwent MRI. Glenohumeral instability was defined as alpha angle >30° and percentage of posterior humeral head displacement >50%. Diagnostic accuracy of physical examination and US was calculated and quantitative parameters were compared with Wilcoxon test.RESULTSGlenohumeral instability was confirmed with MRI in 15 of 21 patients. Accuracy and sensitivity of physical examination and US were 47%, 66% and 100%, 100%, respectively in determination of glenohumeral instability. No significant difference was found for the alpha angle (p = 0.173) but the percentage of posterior humeral head displacement was statistically significant between US and MRI (p = 0.028).CONCLUSIONOur results indicate that US with dynamic evaluation is a good alternative for MRI in assessment of glenohumeral instability in infants with BPBI, since it is highly accurate and specific, and quantitative measurements used for glenohumeral instability were comparable to MRI. US can be used as a screening method to assess glenohumeral instability in infants with BPBI.

Children with brachial plexus birth injury (BPBI) may eventually develop glenohumeral instability (GI) due to development of unbalanced muscular strength. Shoulder related problems in patients with BPBI include internal rotation contracture, impaired physeal growth, and articular changes (glenoid retroversion and posterior glenoid deformation) (1, 2). Despite the fact that GI is most commonly believed to develop gradually after birth, the exact timing is not clear (3, 4). In order to prevent the development of osseous deformity, early diagnosis and intervention of GI is critical (5–7). Recent studies showed that development of GI can be detected with ultrasonography (US) as early as 3 months of age (8, 9). Clinical diagnosis of GI can be challenging and imaging modalities are important for the evaluation of stability of the joint (2). Because of the lack of ossification in the humeral head and glenoid, conventional radiographs and computerized tomography have only minor roles in the assessment of GI (10, 11). Although magnetic resonance imaging (MRI) is the current gold standard imaging modality for dysplasia in the whole age spectrum, US is also a very promising modality that can be used for this purpose. Since it is cost effective and, unlike MRI, requires no anesthesia, frequent follow-up examinations are possible with US (1, 2, 9, 12, 13). Furthermore, it is also possible to perform dynamic examination and assess the reducibility of the humeral head with US (13), which can be used as a good indicator for GI. In the literature, a variety of quantitative parameters has been used to assess the presence of GI but the alpha (α) angle and the percentage of posterior humeral head displacement (PPHHD) are the most valuable parameters for overall evaluation of the GI (2, 12, 14). Intra- and interobserver reliability of these measurements was shown to be good to excellent for US (12, 15) but there was poor agreement between US and MRI (15).The major goal of our study is to compare the accuracy of primary physical examination and US in infants with BPBI and determine whether the diagnostic success of US is comparable to MRI, the current gold standard modality. In addition, the secondary objective of this study is to assess the agreement between US and MRI measurements for detecting GI in this patient population.