title: A biomechanical analysis of initial fixation options for porous-tantalum-backed glenoid components.
abstract: BACKGROUND
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Orthopaedic Surgery, Beaumont Health System, Royal Oak, MI, USA.
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Budge
authors.forename: Michael D
authors.initials: MD
authors.lastname: Kurdziel
authors.forename: Kevin C
authors.initials: KC
authors.lastname: Baker
authors.forename: J Michael
authors.initials: JM
authors.lastname: Wiater
mesh_terms: D019643:Arthroplasty, Replacement / Q000379:methods*; D001672:Biocompatible Materials; D001696:Biomechanical Phenomena; D001843:Bone Cements; D018786:Bone Substitutes; D006801:Humans; D007595:Joint Prosthesis; D016348:Osseointegration; D011475:Prosthesis Failure; D012540:Scapula / Q000601:surgery*; D012785:Shoulder Joint / Q000503:physiopathology* / Q000601:surgery*; D013635:Tantalum
chemical_list: D001672:Biocompatible Materials; D001843:Bone Cements; D018786:Bone Substitutes; D013635:Tantalum