title: Biomechanical benefits of anterior offsetting of humeral head component in posteriorly unstable total shoulder arthroplasty: A cadaveric study.
abstract: Restoration of joint stability during total shoulder arthroplasty can be challenging in the face of severe glenoid retroversion. A novel technique of humeral head component anterior-offsetting has been proposed to address posterior instability. We evaluated the biomechanical benefits of this technique in cadaveric specimens. Total shoulder arthroplasty was performed in 14 cadaveric shoulders from 7 donors. Complementary shoulders were assigned to either 10° or 20° glenoid retroversion, with retroversion created by eccentric reaming. Two humeral head component offset positions were tested in each specimen: The anatomic (posterior) and anterior (reverse). With loads applied to the rotator cuff and deltoid, joint contact pressures and the force and energy required for posterior humeral head translation were measured. The force and energy required to displace the humeral head posteriorly increased significantly with the anterior offset position compared to the anatomic offset position. The joint contact pressures were significantly shifted anteriorly, and the joint contact area significantly increased with the anterior offset position. Anterior offsetting of the humeral head component increased the resistance to posterior humeral head translation, shifted joint contact pressures anteriorly, and increased joint contact area, thus, potentially increasing the joint stability in total shoulder arthroplasty with simulated glenoid retroversion.
authors.affiliation: Department of Orthopaedics and Rehabilitation, Penn State College of Medicine, Hershey, 17033, Pennsylvania.
authors.forename: Hyun-Min Mike
authors.initials: HM
authors.lastname: Kim
authors.affiliation: Department of Orthopaedics and Rehabilitation, Penn State College of Medicine, Hershey, 17033, Pennsylvania.
authors.forename: Alexander C
authors.initials: AC
authors.lastname: Chacon
authors.affiliation: Department of Orthopaedics and Rehabilitation, Penn State College of Medicine, Hershey, 17033, Pennsylvania.
authors.forename: Seth H
authors.initials: SH
authors.lastname: Andrews
authors.affiliation: Department of Orthopaedics and Rehabilitation, Penn State College of Medicine, Hershey, 17033, Pennsylvania.
authors.forename: Evan P
authors.initials: EP
authors.lastname: Roush
authors.affiliation: Department of Orthopaedics and Rehabilitation, Penn State College of Medicine, Hershey, 17033, Pennsylvania.
authors.forename: Edward
authors.initials: E
authors.lastname: Cho
authors.affiliation: Department of Orthopaedics and Rehabilitation, Penn State College of Medicine, Hershey, 17033, Pennsylvania.
authors.forename: William K
authors.initials: WK
authors.lastname: Conaway
authors.affiliation: Department of Public Health Sciences, Penn State College of Medicine, 500 University Drive, Hershey, 17033, Pennsylvania.
authors.forename: Allen R
authors.initials: AR
authors.lastname: Kunselman
authors.affiliation: Department of Orthopaedics and Rehabilitation, Penn State College of Medicine, Hershey, 17033, Pennsylvania.
authors.forename: Gregory S
authors.initials: GS
authors.lastname: Lewis
mesh_terms: D000328:Adult; D001178:Arthroplasty / Q000379:methods*; D006801:Humans; D006811:Humerus / Q000502:physiology; D008875:Middle Aged; D012785:Shoulder Joint / Q000502:physiology / Q000601:surgery*
keywords: glenoid retroversion; humeral head offset; posterior instability; total shoulder arthroplasty