Abstract
ObjectiveAnatomical parameters and pathologies that can affect the critical shoulder angle (CSA) are subjects of discussion. To date, we do not know if the CSA value changes in the different decades of life in a population characterized by the same ethnicity, nor if there are differences related to gender or side. This study hypothesizes that age and gender may affect the CSA.MethodsPatients older than 15 years old affected by a shoulder trauma and who were discharged with a diagnosis of shoulder contusion were enrolled. A true AP view of the shoulder was obtained as well as data regarding age and gender of all participants. The CSA was measured by three authors, and interoperator reliability was assessed. Eight subcategories, according to decades of life, were considered. Finally, the studied population was divided into three subcategories according to CSA values (< 30°; 30–35°; ≥ 35°).ResultsThe initial sample comprised 3587 shoulder X-rays. The interobserver reproducibility was high, with an intraclass correlation coefficient of 0.865 (95% CI 0.793–0.915).Two thousand eight hundred seventy-three radiograms were excluded. The studied group comprised 714 patients [431 females, 283 males; mean age (SD): 47.2 (20.9) years, range: 11–93 years]. The mean CSA was 33.6° (range: 24–50°; SD: 3.9°). The mean CSA values in females and males were 33.7°and 33.5°, respectively. The mean CSA values of the right and left shoulders were 33.3° and 33.9°, respectively (p > 0.05). Linear regression analysis showed a CSA increase by 0.04° every year. The mean CSA in subjects aged between 15 and 19 years was significantly lower than all the other groups, except for patients older than 80 years.No significant differences were found between CSA subcategories, gender, or side.ConclusionsIn the general population, the mean CSA value was 33.6°. No significant differences were found regarding the mean CSA value according to gender or side. A significant positive linear correlation between CSA and age was detected. In each decade of life, the CSA value, which is genetically determined, shows a large variability.Level of evidence: IV.
Highlights
The critical shoulder angle (CSA) corresponds to the angle obtained by the conjunction between two lines: the first line is drawn by joining the superior and inferior bony margins of the glenoid; the second line joins the inferior bony margin of the glenoid to the mostGumina et al Journal of Orthopaedics and Traumatology (2022) 23:10 lateral border of the acromion
No significant differences were found regarding the mean CSA value according to gender or side
In 2013, Moor et al [1] stated that patients with primary glenohumeral osteoarthritis have a significantly smaller CSA compared with controls and patients with rotator cuff tear
Summary
The critical shoulder angle (CSA) corresponds to the angle obtained by the conjunction between two lines: the first line is drawn by joining the superior and inferior bony margins of the glenoid; the second line joins the inferior bony margin of the glenoid to the mostGumina et al Journal of Orthopaedics and Traumatology (2022) 23:10 lateral border of the acromion. Anatomical parameters that can affect the angle width are the lateral acromial offset and the glenoid inclination. In 2013, Moor et al [1] stated that patients with primary glenohumeral osteoarthritis have a significantly smaller CSA compared with controls and patients with rotator cuff tear. This hypothesis has been recently confirmed: CSA has been shown to be significantly different when patients with osteoarthritis are compared with subjects without degenerative changes of the glenohumeral joint [3, 6, 11]. Isolated types II–IV superior labrum anterior to posterior lesions have been associated with a low CSA (< 30°) [10]
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