title: Associations between in-vivo glenohumeral joint motion and morphology.
abstract: Joint morphology has a significant influence on joint motion and may contribute to the development of rotator cuff pathology, but the relationships between glenohumeral joint (GHJ) morphology and in-vivo GHJ motion are not well understood. The objectives of this study were to assess measures of joint morphology and their relationship with in-vivo joint motion in two populations: shoulders with intact rotator cuffs (n=48) and shoulders with rotator cuff pathology (n=36, including 5 symptomatic tears, 9 asymptomatic tears and 22 repaired tears). GHJ morphology was measured from CT-based three-dimensional models of the humerus and scapula. In-vivo GHJ motion was measured during shoulder abduction using biplane x-ray imaging. Associations between GHJ morphology and motion were assessed with univariate and best subsets regression. The only morphological difference identified between the populations was the critical shoulder angle (intact: 34.5 ± 4.7°, pathologic: 36.9 ± 5.0°, p=0.03), which is consistent with previous research. In intact shoulders, the superior/inferior (S/I) position of the humerus on the glenoid during shoulder abduction was significantly associated with the glenoid's S/I radius of curvature (p<0.01), conformity index (p<0.01), and stability angle (p<0.01). Furthermore, the S/I position of the humerus on the glenoid was negatively associated with the critical shoulder angle (p=0.04), which contradicts previous research. No significant associations between GHJ morphology and GHJ motion were detected in shoulders with rotator cuff tears. It is unknown if rotator cuff pathology compromises the relationships between GHJ morphology and motion, or if the absence of this relationship is a pre-existing condition that increases the likelihood of pathology.
authors.affiliation: Department of Orthopaedic Surgery, Bone & Joint Center, Henry Ford Health System, United States. Electronic address: cpeltz1@hfhs.org.
authors.forename: Cathryn D
authors.initials: CD
authors.lastname: Peltz
authors.affiliation: Department of Public Health Sciences, Henry Ford Health System, United States.
authors.forename: George
authors.initials: G
authors.lastname: Divine
authors.affiliation: Department of Orthopaedic Surgery, Bone & Joint Center, Henry Ford Health System, United States.
authors.forename: Anne
authors.initials: A
authors.lastname: Drake
authors.affiliation: Department of Orthopaedic Surgery, Bone & Joint Center, Henry Ford Health System, United States.
authors.forename: Nicole L
authors.initials: NL
authors.lastname: Ramo
authors.affiliation: Department of Orthopaedic Surgery, Bone & Joint Center, Henry Ford Health System, United States.
authors.forename: Roger
authors.initials: R
authors.lastname: Zauel
authors.affiliation: Department of Orthopaedic Surgery, Sports Medicine Division, Henry Ford Health System, United States.
authors.forename: Vasilios
authors.initials: V
authors.lastname: Moutzouros
authors.affiliation: Department of Orthopaedic Surgery, Bone & Joint Center, Henry Ford Health System, United States.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Bey
mesh_terms: D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016059:Range of Motion, Articular; D017006:Rotator Cuff / Q000473:pathology / Q000503:physiopathology*; D000070636:Rotator Cuff Injuries; D012540:Scapula / Q000473:pathology; D012785:Shoulder Joint / Q000473:pathology / Q000503:physiopathology*
keywords: Critical shoulder angle; Glenohumeral joint motion; Glenoid inclination; Glenoid morphology; Rotator cuff