Glenoid version: the role of genetic and environmental factors on its variability. An MRI study on asymptomatic elderly twins

Abstract

Background Glenoid version is the most variable parameter of the shoulder joint. No authors investigated if intrinsic genetic factors or influences from extrinsic sources are responsible for its variability. Aim We compared glenoid version between elderly monozygotic and dizygotic twins intending to separate the contributions of genetics from shared and unique environments. Methods Glenoid version of the dominant shoulder was assessed by MRI using Friedman’s method in 30 pairs of elderly twins (16 monozygotic–14 dizygotic; mean age ± SD: 63.72 ± 3.37, 53–72). Heritability was estimated as twice the difference between the intraclass correlation coefficients for monozygotic and dizygotic pairs. The influence of shared environment was calculated as the difference between monozygotic correlation coefficient and the heritability index. According to job category, one way analysis of variance was used to estimate the differences between groups in the total sample and within zygosity groups. Results Glenoid version angle in monozygotic and dizygotic twins was −2° (SD: 2°) and −3° (SD: 3°), respectively (p = 0.334). Heritability index was 0.98, while the contributions of shared and unique environment were 0 and 0.02, respectively. According to working classes, no significant differences were found between the groups (p = 0.732, F = 0.31). Conclusions Glenoid version is mainly genetically determined and only marginally influenced by environments. Level of evidence: III.

Posterior Shoulder Instability in Tennis Players: Aetiology, Classification, Assessment and Management

“…[50][51][52][53] Glenoid retroversion angles can vary within a normal shoulder population, though most authors agree that a retroversion angle of 10 or more degrees would be considered excessive (Figure 2a). 53,54 The degree of glenoid version is considered to be largely genetically determined in the general population, 55 however repetitive overhead use of the arm before the age of 12 years (prior to the development of secondary ossification centers) could impact glenoid development. 56 Recent evidence 57 identifies an increased incidence of posterior glenoid dysplasia in adoles- Posterior humeral head subluxations can cause glenoid erosion due to shearing of the humeral head across the posterior glenoid rim which can further progress PSI (Figure 2b).…”