A biomechanical analysis of initial fixation options for porous-tantalum-backed glenoid components.

Porous-tantalum (PT)-backed glenoid components have recently been developed to improve fixation and minimize the incidence of glenoid component loosening, which remains a key limiting factor in long-term survival in total shoulder arthroplasty. PT-backed glenoids promote bony ingrowth as a method of preventing glenoid loosening at the prosthesis-glenoid interface. The use of polymethyl-methacrylate (PMMA) cement for initial fixation may prevent osteointegration due to mechanical occlusion of the porous surface and the nonosteoconductive properties of PMMA. This study aims to investigate alternative fixation methods of PT-backed glenoids in a biomechanical investigation. Nine PT-backed monoblock glenoid components were implanted in a polyurethane bone substitute using either press-fit, PMMA cement, or calcium phosphate cement techniques. A control group of 3 all-polyethylene pegged glenoid components was implanted with PMMA. Glenoid and humeral head components were fixed to a biomechanical testing machine for testing according to ASTM Standard F-2028. The humeral head was translated ±1.5 mm along the superior-inferior axis for 50,000 cycles for characterization of glenoid rocking and inferior-superior translation. Glenoid compression and glenoid distraction followed similar patterns for PT-backed glenoids. Overall, the all-polyethylene cemented glenoid demonstrated superior fixation compared to all PT-backed groups throughout the test. Glenoids fixed with PMMA cement displayed more favorable initial fixation and resistance to glenoid motion throughout cyclic testing. This study showed that among PT-backed glenoids, PMMA fixation provided an increase in stability during initial and final cycles compared to press-fit and calcium-phosphate fixation techniques. This improved stability may enhance the osteointegration of the implant.

Budge MD ，Kurdziel MD ，Baker KC ，Wiater JM ... -  《-》

Biomechanical Evaluation of All-Polyethylene Pegged Bony Ingrowth Glenoid Fixation Techniques on Implant Micromotion.

Wiater BP ，Moravek JE Jr ，Kurdziel MD ，Baker KC ，Wiater JM ... -  《-》

Glenohumeral mismatch affects micromotion of cemented glenoid components in total shoulder arthroplasty.

The "rocking horse" phenomenon is considered the main cause of glenoid component loosening by eccentric loading of the glenoid rim. This study aimed to investigate the influence of increasing glenohumeral implant mismatch on bone-implant interface micromotion in a cemented all-polyethylene pegged glenoid biomechanical model. Five glenoid sizes, 40 mm, 44 mm, 48 mm, 52 mm, and 56 mm, representing +2 mm, +6 mm, +10 mm, +14 mm, and +18 mm glenohumeral mismatch, respectively, were cyclically loaded according to ASTM Standard F2028-08 at a constant frequency of 2 Hz to a size-dependent humeral head subluxation translation. Additional glenoid components were cyclically loaded to their subluxation translations at a constant humeral head rate of 4.4 mm/s. Component micromotion was characterized as compression, distraction, and superior-inferior translation measured by differential variable reluctance transducers. During constant frequency tests, 52-mm and 56-mm glenoids were unable to complete cyclic testing because of catastrophic failure of the glenoid-implant interface and permanent glenoid deformation, probably due to increasing severity of testing parameters. When tested at a constant humeral head speed, 48-mm, 52-mm, and 56-mm glenoids had significantly increased glenoid distraction and glenoid translation at cycle 50,000 compared with cycle 1. Distraction and translation measurements for 52-mm and 56-mm glenoids were significantly greater compared with 40-mm, 44-mm, and 48-mm glenoids at 50,000 cycles. In a biomechanical model, optimal glenohumeral mismatch in cemented pegged glenoid implants is multifactorial and has not been definitively established. However, our data suggest that a radial mismatch of less than +10 mm may decrease the risk of glenoid micromotion.

Sabesan VJ ，Ackerman J ，Sharma V ，Baker KC ，Kurdziel MD ，Wiater JM ... -  《-》

Cemented polyethylene versus uncemented metal-backed glenoid components in total shoulder arthroplasty: a prospective, double-blind, randomized study.

Boileau P ，Avidor C ，Krishnan SG ，Walch G ，Kempf JF ，Molé D ... -  《JOURNAL OF SHOULDER AND ELBOW SURGERY》

Analysis of Glenoid Fixation with Anatomic Total Shoulder Arthroplasty in an Extreme Cyclic Loading Scenario.

Roche CP ，Staunch C ，Hahn W ，Grey SG ，Flurin PH ，Wright TW ，Zuckerman JD ... -  《-》