title: A comprehensive update on current fixation options for two-part proximal humerus fractures: a biomechanical investigation.
abstract: BACKGROUND
  Recent advancements in implant technology offer updated options for surgical management that have been rapidly adopted into clinical practice. The objective of this study is to biomechanically test and compare the current fixation options available for surgical fixation of two-part proximal humerus fractures and establish load to failure and stiffness values.
  
  
  METHODS
  Sixteen match-paired (32 total) fresh-frozen, cadaveric specimens were randomized to receive 1 of 4 fixation constructs following creation of an AO/OTA Type 11A3 (two-part) proximal humerus fractures. Fixation constructs tested consisted of 3.5 mm fixed angle plate (3.5-FAP), 4.5 mm fixed angle plate (4.5-FAP), humeral intramedullary nail (IMN), and a humeral intramedullary nail with a fixed angle blade (IMN-FAB). Specimen bone density was measured to ensure no adequate, non-osteoporotic bone. Constructs were tested for stiffness and ultimate load to failure and compared via one-way ANOVA analysis with subsequent post hoc Tukey HSD multiple group comparison statistical analysis.
  
  
  RESULTS
  The IMN-FAB construct was significantly stiffer than the 3.5-FAP construct (123.8 vs. 23.9, p<0.0001), the 4.5-FAP construct (123.8 vs. 33.3, p<0.0001) and the IMN construct (123.8 vs. 60.1, p=0.005). The IMN-FAB construct reported a significantly higher load to failure than the 3.5-FAB construct (4667.3 N vs. 1756.9 N, p<0.0001), and the 4.5-FAP construct (4667.3 N vs. 2829.4 N, p=0.019, Table 2). The IMN construct had a significantly higher load to failure than the 3.5-FAP construct (3946.8 vs. 1756.9, p=0.001, Table 2).
  
  
  CONCLUSIONS
  Biomechanical testing of modern fixation options for two-part proximal humerus fracture exhibited that the stiffest and highest load to failure construct was the IMN-FAB followed by the IMN, 3.5-FAP and then the 4.5-FAP constructs. However, prospective clinical trials with longer-term follow-up are required for definitive assessment of the ideal fixation construct for surgical management of two-part proximal humerus fractures.
authors.affiliation: Division of Orthopaedic Trauma, Department of Orthopaedic Surgery, NYU Hospital for Joint Diseases, New York, NY 10003, USA.
authors.forename: Richard S
authors.initials: RS
authors.lastname: Yoon
authors.affiliation: Division of Orthopaedic Trauma, Department of Orthopaedic Surgery, INOVA Fairfax Hospital, Faiefax, VA 22003, USA.
authors.forename: Daniel
authors.initials: D
authors.lastname: Dziadosz
authors.affiliation: Division of Orthopaedic Trauma, Department of Orthopaedic Surgery, INOVA Fairfax Hospital, Faiefax, VA 22003, USA.
authors.forename: David A
authors.initials: DA
authors.lastname: Porter
authors.affiliation: Division of Orthopaedic Trauma, Department of Orthopaedic Surgery, INOVA Fairfax Hospital, Faiefax, VA 22003, USA.
authors.forename: Matthew A
authors.initials: MA
authors.lastname: Frank
authors.affiliation: Division of Orthopaedic Trauma, Department of Orthopaedic Surgery, Swedish Medical Center, Denver, CO 80204, USA.
authors.forename: Wade R
authors.initials: WR
authors.lastname: Smith
authors.affiliation: Division of Orthopaedic Trauma, Department of Orthopaedic Surgery, NYU Hospital for Joint Diseases, New York, NY 10003, USA. Electronic address: liporace33@gmail.com.
authors.forename: Frank A
authors.initials: FA
authors.lastname: Liporace
mesh_terms: D001696:Biomechanical Phenomena; D015519:Bone Density; D001858:Bone Nails; D001860:Bone Plates; D002102:Cadaver; D005260:Female; D005594:Fracture Fixation, Intramedullary / Q000379:methods; D006801:Humans; D006810:Humeral Fractures / Q000473:pathology / Q000601:surgery*; D008297:Male; D011897:Random Allocation; D016474:Weight-Bearing
keywords: Fixed angle blade; Fixed angle plate; Intramedullary nail; Locked plate; Proximal humerus fracture