title: Effect of humeral head component size on hemiarthroplasty translations and rotations.
abstract: Glenohumeral translation and rotation were measured in 6 grossly normal, fresh frozen shoulder preparations while a manual load was applied to the humerus. The same tests (maximum elevation, total rotation, anterior/posterior (A/P) translation, and inferior translation) were repeated for each shoulder through 8 series: 1 with the shoulder intact, 1 with the shoulder vented, and 6 with progressively larger humeral head components after hemiarthroplasty. There was an inverse linear relation between humeral head component size and all 4 outcome variables. Replacing the native head with a component of equal diameter reduced elevation 20%, rotation 40%, A/P translation 50%, and inferior translation 60% in the vented shoulder. Replacing the native head with a component of equal effective volume decreased elevation 8%, rotation 20%, A/P translation 25%, and inferior translation 40% in the vented shoulder. Increasing humeral head component size decreased rotation, A/P translation, and inferior translation by similar percentages and elevation somewhat less. Humeral head component size is better described in terms of volume than in terms of diameter or offset.
authors.affiliation: Department of Orthopaedics, University of New Mexico School of Medicine, USA.
authors.forename: F T
authors.initials: FT
authors.lastname: Blevins
authors.forename: F E
authors.initials: FE
authors.lastname: Pollo
authors.forename: P A
authors.initials: PA
authors.lastname: Torzilli
authors.forename: R F
authors.initials: RF
authors.lastname: Warren
mesh_terms: D019643:Arthroplasty, Replacement; D002102:Cadaver; D006801:Humans; D006811:Humerus / Q000601:surgery*; D010027:Osteotomy; D016059:Range of Motion, Articular; D012399:Rotation; D012785:Shoulder Joint / Q000502:physiology* / Q000601:surgery*