Reference Values and influencing factors of the Glenohumeral Subluxation Index - a study on 3004 participants

The primary objective of this study was to examine the Glenohumeral subluxation index (GHSI) in a large general population cohort and to define reference values. Glenohumeral subluxation is important in the development and prediction of pathological states of the shoulder joint and in total shoulder arthroplasty. Therefore, another objective was to examine the influence of age, sex, BMI, body height and weight on GHSI. GHSI according to Walch was measured on bilateral MRI of 3004 participants of the Study of Health in Pomerania (SHIP, aged 21-90 years). SHIP drew a sample of the adult general population of Pomerania (Northeastern Germany). Reference values for GHSI were assessed by quantile regression models. Associations of sex, age and anthropometric markers with the GHSI were calculated by linear regression models. A reference range between 42% and 55% for men with a mean of 49% ±4% was defined, while the upper reference limit of women was 1% higher (mean 50% ±4%). Age was inversely associated with the GHSI in males (p˂0.001), while no significant association in females was observed (p=0.625). Body weight and body mass index (BMI) was positively associated (p˂0.001) without effect modification by sex. Heavy mechanical oscillations on the upper extremity showed no significant association with GHSI (p = 0.268). The reference values for GHSI were expanded to a range of 42% – 57% on MRI. Several associations between GHSI and anthropometric properties are present. According to these associations, adjusted formulas are provided to enable individual, patient specific diagnostics and therapy. Nevertheless, the clinical picture cannot be neglected.