title: Construct damage and loosening around glenoid implants: A longitudinal micro-CT study of five cadaver specimens.
abstract: The evolution of failure of bone and cement leading to loosening of glenoid components following shoulder arthroplasty is not well understood. The purpose of this study was to identify and visualize potential mechanisms of mechanical failure within cadavers, cemented with two types of components, and subject to cyclic loading. Five glenoid cadaver bones were implanted with either a three-pegged polyethylene component, or prototype posteriorly augmented component which addresses posterior bone loss. Specimens were loaded by constant glenohumeral compression combined with cyclic anterior-posterior displacement of the humeral head relative to the glenoid. At six time points across 100,000 cycles, implant loosening micromotions were optically measured, and specimens were imaged by micro-computed tomography. Scans were 3D registered and inspected for crack initiation and progression, and micro-CT based time-lapse movies were created. Cement cracking initiated at stress concentrations and progressed with additional cyclic loading. Failure planes within trabecular bone and the bone-cement interface were identified in four of the five specimens. Implant subsidence increased to greater than 1.0 mm in two specimens. Cemented glenoid structural failure can occur within the cement, along planes of trabecular bone, or at the bone cement interface. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1053-1060, 2016.
authors.affiliation: Department of Orthopaedics and Rehabilitation, Penn State College of Medicine and M.S. Hershey Medical Center, 500 University Drive, Mail Code H089, Hershey, Pennsylvania, 17033.
authors.forename: Gregory S
authors.initials: GS
authors.lastname: Lewis
authors.affiliation: Department of Orthopaedics and Rehabilitation, Penn State College of Medicine and M.S. Hershey Medical Center, 500 University Drive, Mail Code H089, Hershey, Pennsylvania, 17033.
authors.forename: Jacob B
authors.initials: JB
authors.lastname: Brenza
authors.affiliation: Department of Orthopaedics and Rehabilitation, Penn State College of Medicine and M.S. Hershey Medical Center, 500 University Drive, Mail Code H089, Hershey, Pennsylvania, 17033.
authors.forename: Emmanuel M
authors.initials: EM
authors.lastname: Paul
authors.affiliation: Department of Orthopaedics and Rehabilitation, Penn State College of Medicine and M.S. Hershey Medical Center, 500 University Drive, Mail Code H089, Hershey, Pennsylvania, 17033.
authors.forename: April D
authors.initials: AD
authors.lastname: Armstrong
mesh_terms: D006801:Humans; D008137:Longitudinal Studies; D011475:Prosthesis Failure; D012785:Shoulder Joint / Q000000981:diagnostic imaging; D000072227:Shoulder Prosthesis; D055114:X-Ray Microtomography
keywords: glenoid component; implant fixation; implant loosening; micro-computed tomography; total shoulder arthroplasty