Critical shoulder angle (CSA): age and gender distribution in the general population

S Gumina; G Polizzotti; A Spagnoli; S Carbone; V Candela

doi:10.1186/s10195-022-00627-w

Critical shoulder angle (CSA): age and gender distribution in the general population

J Orthop Traumatol. 2022 Feb 14;23(1):10. doi: 10.1186/s10195-022-00627-w.

Authors

S Gumina^{1

2}, G Polizzotti³, A Spagnoli⁴, S Carbone⁵, V Candela⁶

Affiliations

¹ Department of Anatomical, Histological, Forensic Medicine and Orthopaedics Sciences, Istituto Clinico Ortopedico Traumatologico (ICOT), Sapienza University of Rome, Latina, Italy. Stefano.gumina@uniroma1.it.
² Department of Anatomy, Histology, Legal Medicine and Orthopedics, University of Rome, Piazzale Aldo Moro 5, 00185, Rome, Italy. Stefano.gumina@uniroma1.it.
³ Department of Anatomical, Histological, Forensic Medicine and Orthopaedics Sciences, Istituto Clinico Ortopedico Traumatologico (ICOT), Sapienza University of Rome, Latina, Italy.
⁴ Department of Public Health and Infectious Diseases, Sapienza University of Rome, Rome, Italy.
⁵ Orthopaedics and Traumatology Unit, San Feliciano Hospital, Rome, Italy.
⁶ Department of Anatomy, Histology, Legal Medicine and Orthopedics, University of Rome, Piazzale Aldo Moro 5, 00185, Rome, Italy.

Abstract

Objective: Anatomical 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.

Methods: Patients 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°).

Results: The 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.

Conclusions: In 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.

Keywords: Critical shoulder angle; Extrinsic factors for rotator cuff tear; Glenoid inclination; Rotator cuff tear etiology; Rotator cuff tear risk factors; Scapular anatomy.

MeSH terms

Adolescent
Adult
Female
Humans
Male
Reproducibility of Results
Retrospective Studies
Rotator Cuff Injuries*
Shoulder
Shoulder Joint* / diagnostic imaging
Young Adult