title: Influence of different peg length in glenoid bone loss: A biomechanical analysis regarding primary stability of the glenoid baseplate in reverse shoulder arthroplasty.
abstract: BACKGROUND
  There is no biomechanical basis to determine the influence of different length of the central peg of the baseplate anchored within the native scapula in glenoid defect reconstruction in cases of degenerative or posttraumatic glenoid bone loss in reversed shoulder arthroplasty.
  
  
  OBJECTIVE
  The purpose of this study was to analyse the stability of different peg lengths used in glenoid bone loss in reversed shoulder arthroplasty.
  
  
  METHODS
  Different lengths of metaglene pegs with different depths of peg anchorage performed with or without metaglene screws in sawbone foam blocks were loaded in vertical and horizontal directions for differentiating load capacities. Simulated physiological loadings were then applied to the peg implants to determine the limits of loading in each depth of anchorage.
  
  
  RESULTS
  The loading capacity of the implant was reduced as less of the peg was anchored. The vertically loaded implants showed a significantly higher stability, in contrast to those loaded horizontally at a corresponding peg length and depth of anchorage (p < 0.05). The tests revealed that the metaglene screws are more essential for primary stability than is the peg particularly in the vertically directed loadings (2/3 anchored: peg contributed to 28% of the stability, 1/3 anchorage: peg contributed to 12%). Under the second test conditions, the lowest depth of peg anchorage (1/3) resulted in 322 Newtons [N] in the long peg with a vertical loading direction, and in 130 N in the long peg with a horizontal loading direction (p < 0.05).
  
  
  CONCLUSIONS
  The pegs should be anchored as deeply as possible into the native scapula bone stock. The metaglene screws play a major role in the initial stability, in contrast to the peg, and they become more important when the depth of the peg anchorage is reduced. If possible, four metaglene screws should be used in cases of uncontained bone loss to guarantee the highest stability.
authors.affiliation: Department of General and Trauma Surgery, University Bergmannsheil Bochum, Ruhr-University Bochum, Bochum, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Königshausen
authors.affiliation: Department of General and Trauma Surgery, University Bergmannsheil Bochum, Ruhr-University Bochum, Bochum, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Jettkant
authors.affiliation: Department of Mechanical Engineering, Ruhr-University Bochum, Bochum, Germany.
authors.forename: N
authors.initials: N
authors.lastname: Sverdlova
authors.affiliation: Department of Mechanical Engineering, Ruhr-University Bochum, Bochum, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Ehlert
authors.affiliation: Department of General and Trauma Surgery, University Bergmannsheil Bochum, Ruhr-University Bochum, Bochum, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Gessmann
authors.affiliation: Department of General and Trauma Surgery, University Bergmannsheil Bochum, Ruhr-University Bochum, Bochum, Germany.
authors.forename: T A
authors.initials: TA
authors.lastname: Schildhauer
authors.affiliation: Department of General and Trauma Surgery, University Bergmannsheil Bochum, Ruhr-University Bochum, Bochum, Germany.
authors.forename: D
authors.initials: D
authors.lastname: Seybold
mesh_terms: D019643:Arthroplasty, Replacement; D001696:Biomechanical Phenomena; D006801:Humans; D007595:Joint Prosthesis; D011474:Prosthesis Design / Q000295:instrumentation*; D012785:Shoulder Joint
keywords: Glenoid bone loss; glenoid bone grafting; glenoid defect; omarthrosis; peg length; primary stability; reversed shoulder arthroplasty; total shoulder arthroplasty