What is the current use of Ultrasound (US) imaging in the shoulder region?
The US can be used in the shoulder region as diagnostic tool to detect abnormalities of rotator cuff tendons and long head of the biceps tendon by clinicians (1, 2) . Nowadays, US is increasingly used in physiotherapy, with 1 out of 6 physical therapists in the Netherlands in primary care using US mainly when suspecting tissue damage in shoulder complaints (3) . Duijn et al. reported in a recent study that physical therapists agreed on the presence of rotator cuff ruptures and other pathology in patients with subacromial shoulder pain, but they agreed less on the absence of these pathologies (4) . This study included physiotherapists who followed courses on musculoskeletal US and had a short training before the start of the study.
Training is important
We know that a good training in US examination is essential when evaluating the shoulder. This was recently highlighted in a reliability study conducted by our research team in patients with subacromial shoulder pain and asymptomatic participants, where two examiners with different US experience (novice versus experienced examiners) compared their results (5), obtained with the US machine in Figure 1. We examined: 1) the acromiohumeral distance (AHD) – showed in Figure 2 -, which is the representation of the space between the acromion and the humerus on the US image, 2) the supraspinatus tendon thickness, which is a tendon passing through this space, and 3) the relationship between these two parameters. We found that the agreement between the two examiners varied largely from poor to good and we suggested a structured training on patients with shoulder pain. Most of the research on these measures found excellent agreement when images were taken at different times by the same examiner (6), but agreement between raters with different US experience is usually more difficult to achieve (7). A structured training and overall agreement phase are suggested in order to obtain excellent agreement between different raters (6).
Is there a relationship between symptoms and results of US images in shoulder pain?
When looking at the AHD as representation of the subacromial space, a recent systematic review found no relationship between AHD and shoulder symptoms (8) . Traditionally, the impingement theory supposes that shoulder complaints are caused by the irritation of the rotator cuff tendons under the acromion, through a reduction of the subacromial space. The poor diagnostic accuracy of the impingement tests (9) and the non-clinically significant difference between surgical decompression of this space and placebo surgery (10) call into question this theory. This would mean that treatments aiming mainly at opening this subacromial space are not clinically meaningful for a patient with subacromial shoulder pain. Moreover, the relationship between rotator cuff abnormalities and pain is also not always clear, as we see that rotator cuff tears can be asymptomatic (11) or abnormalities as thinning or degeneration are part of the normal process of aging (12) .
The conclusion (…or not)
The US can be used to tailor treatment or as feedback during exercises of motor control (13) : it is non-invasive, it doesn’t have ionizing radiations and it gives insight into tissue damage as additional aid to shoulder evaluation. However, it is very operator-dependent and therefore a structured training is necessary. The link of the US findings with medical history and physical examination is important but we should be aware that sometimes the findings don’t correspond to the complaints. Moreover, the US can be used in research to further explore intrinsic factors related to the cause of subacromial shoulder pain.
PhD student at the University of Antwerp, research group MOVANT.
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2. Ottenheijm RP, Jansen MJ, Staal JB, van den Bruel A, Weijers RE, de Bie RA et al. Accuracy of diagnostic ultrasound in patients with suspected subacromial disorders: a systematic review and meta-analysis. Arch Phys Med Rehabil. 2010;91(10):1616-25.
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4. Duijn E, Pouliart N, Verhagen AP, Karel Y, Thoomes-de Graaf M, Koes BW et al. Diagnostic ultrasound in patients with shoulder pain: An inter-examiner agreement and reliability study among Dutch physical therapists. Musculoskelet Sci Pract. 2021;51:102283.
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