title: Glenoid implant orientation and cement failure in total shoulder arthroplasty: a finite element analysis.
abstract: BACKGROUND
  To minimize glenoid implant loosening in total shoulder arthroplasty (TSA), the ideal surgical procedure achieves correction to neutral version, complete implant-bone contact, and bone stock preservation. These goals, however, are not always achievable, and guidelines to prioritize their impact are not well established. The purpose of this study was to investigate how the degree of glenoid correction affects potential cement failure.
  
  
  METHODS
  Eight patient-specific computer models were created for 4 TSA scenarios with different permutations of retroversion correction and implant-bone contact. Two bone models were used: a homogeneous cortical bone model and a heterogeneous cortical-trabecular bone model. A 750-N load was simulated, and cement stress was calculated. The risk of cement mantle fracture was reported as the percentage of cement stress exceeding the material endurance limit.
  
  
  RESULTS
  Orienting the glenoid implant in retroversion resulted in the highest risk of cement fracture in a homogeneous bone model (P < .05). In the heterogeneous bone model, complete correction resulted in the highest risk of failure (P = .0028). A positive correlation (ρ = 0.901) was found between the risk of cement failure and amount of exposed trabecular bone.
  
  
  CONCLUSIONS
  Incorporating trabecular bone into the model changed the effect of implant orientation on cement failure. As exposed trabecular bone increased, the risk of cement fracture increased. This may be due to shifting the load-bearing support underneath the cement from cortical bone to trabecular bone.
authors: Centers for Orthopaedic Research and Shoulder, Elbow and Sports Medicine, Department of Orthopaedic Surgery, Columbia University, New York, NY 10032, USA.
authors: Charlie
authors: C
authors: Yongpravat
authors: H Mike
authors: HM
authors: Kim
authors: Thomas R
authors: TR
authors: Gardner
authors: Louis U
authors: LU
authors: Bigliani
authors: William N
authors: WN
authors: Levine
authors: Christopher S
authors: CS
authors: Ahmad
mesh_terms: D000368:Aged; D019643:Arthroplasty, Replacement / Q000009:adverse effects / Q000379:methods*; D001843:Bone Cements / Q000009:adverse effects*; D003198:Computer Simulation; D020342:Finite Element Analysis; D006801:Humans; D007595:Joint Prosthesis; D008297:Male; D008875:Middle Aged; D010003:Osteoarthritis / Q000503:physiopathology / Q000601:surgery; D011474:Prosthesis Design; D011475:Prosthesis Failure; D012680:Sensitivity and Specificity; D012785:Shoulder Joint / Q000601:surgery*; D013314:Stress, Mechanical; D016474:Weight-Bearing
chemical_list: D001843:Bone Cements